The n_TOF Collaboration (www.cern.ch/ntof)

# Measurement of the 14N(n,p)14C cross section at the CERN n_TOF facility from
sub-thermal energy to 800 keV

Pablo Torres-Sánchez<EMAIL_ADDRESS>University of Granada, Spain  Javier
Praena  University of Granada, Spain  Ignacio Porras  University of Granada,
Spain  Marta Sabaté-Gilarte  European Organization for Nuclear Research
(CERN), Switzerland  Universidad de Sevilla, Spain  Claudia Lederer-Woods
School of Physics and Astronomy, University of Edinburgh, United Kingdom
Oliver Aberle  European Organization for Nuclear Research (CERN), Switzerland
Victor Alcayne  Centro de Investigaciones Energéticas Medioambientales y
Tecnológicas (CIEMAT), Spain  Simone Amaducci  INFN Laboratori Nazionali del
Sud, Catania, Italy  Dipartimento di Fisica e Astronomia, Università di
Catania, Italy  Józef Andrzejewski  University of Lodz, Poland  Laurent
Audouin  Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud,
Université Paris-Saclay, F-91406 Orsay Cedex, France  Vicente Bécares  Centro
de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Spain
Victor Babiano-Suarez  Instituto de Física Corpuscular, CSIC - Universidad de
Valencia, Spain  Michael Bacak  European Organization for Nuclear Research
(CERN), Switzerland  TU Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
CEA Irfu, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France  Massimo
Barbagallo  European Organization for Nuclear Research (CERN), Switzerland
Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Italy  František
Bečvář  Charles University, Prague, Czech Republic  Giorgio Bellia  INFN
Laboratori Nazionali del Sud, Catania, Italy  Dipartimento di Fisica e
Astronomia, Università di Catania, Italy  Eric Berthoumieux  CEA Irfu,
Université Paris-Saclay, F-91191 Gif-sur-Yvette, France  Jon Billowes
University of Manchester, United Kingdom  Damir Bosnar  Department of Physics,
Faculty of Science, University of Zagreb, Zagreb, Croatia  Adam Brown
University of York, United Kingdom  Maurizio Busso  Istituto Nazionale di
Fisica Nucleare, Sezione di Perugia, Italy  Dipartimento di Fisica e Geologia,
Università di Perugia, Italy  Manuel Caamaño  University of Santiago de
Compostela, Spain  Luis Caballero  Instituto de Física Corpuscular, CSIC -
Universidad de Valencia, Spain  Francisco Calviño  Universitat Politècnica de
Catalunya, Spain  Marco Calviani  European Organization for Nuclear Research
(CERN), Switzerland  Daniel Cano-Ott  Centro de Investigaciones Energéticas
Medioambientales y Tecnológicas (CIEMAT), Spain  Adria Casanovas  Universitat
Politècnica de Catalunya, Spain  Francesco Cerutti  European Organization for
Nuclear Research (CERN), Switzerland  Yonghao Chen  Institut de Physique
Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, F-91406 Orsay
Cedex, France  Enrico Chiaveri  European Organization for Nuclear Research
(CERN), Switzerland  University of Manchester, United Kingdom  Universidad de
Sevilla, Spain  Nicola Colonna  Istituto Nazionale di Fisica Nucleare, Sezione
di Bari, Italy  Guillem Cortés  Universitat Politècnica de Catalunya, Spain
Miguel Cortés-Giraldo  Universidad de Sevilla, Spain  Luigi Cosentino  INFN
Laboratori Nazionali del Sud, Catania, Italy  Sergio Cristallo  Istituto
Nazionale di Fisica Nucleare, Sezione di Perugia, Italy  Istituto Nazionale di
Astrofisica - Osservatorio Astronomico di Teramo, Italy  Lucia-Anna Damone
Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Italy  Dipartimento
Interateneo di Fisica, Università degli Studi di Bari, Italy  Maria Diakaki
National Technical University of Athens, Greece  European Organization for
Nuclear Research (CERN), Switzerland  Mirco Dietz  School of Physics and
Astronomy, University of Edinburgh, United Kingdom  César Domingo-Pardo
Instituto de Física Corpuscular, CSIC - Universidad de Valencia, Spain  Rugard
Dressler  Paul Scherrer Institut (PSI), Villigen, Switzerland  Emmeric Dupont
CEA Irfu, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France  Ignacio
Durán  University of Santiago de Compostela, Spain  Zinovia Eleme  University
of Ioannina, Greece  Beatriz Fernández-Domínguez  University of Santiago de
Compostela, Spain  Alfredo Ferrari  European Organization for Nuclear Research
(CERN), Switzerland  Francisco Javier Ferrer  Centro Nacional de Aceleradores
(CNA), Seville, Spain  Universidad de Sevilla, Spain  Paolo Finocchiaro  INFN
Laboratori Nazionali del Sud, Catania, Italy  Valter Furman  Joint Institute
for Nuclear Research (JINR), Dubna, Russia  Kathrin Göbel  Goethe University
Frankfurt, Germany  Ruchi Garg  School of Physics and Astronomy, University of
Edinburgh, United Kingdom  Aleksandra Gawlik-Ramięga  University of Lodz,
Poland  Benoit Geslot  CEA Cadarache, DES, Saint-Paul-les-Durance 13108,
France  Simone Gilardoni  European Organization for Nuclear Research (CERN),
Switzerland  Tudor Glodariu† Horia Hulubei National Institute of Physics and
Nuclear Engineering, Romania  Isabel Gonçalves  Instituto Superior Técnico,
Lisbon, Portugal  Enrique González-Romero  Centro de Investigaciones
Energéticas Medioambientales y Tecnológicas (CIEMAT), Spain  Carlos Guerrero
Universidad de Sevilla, Spain  Frank Gunsing  CEA Irfu, Université Paris-
Saclay, F-91191 Gif-sur-Yvette, France  Hideo Harada  Japan Atomic Energy
Agency (JAEA), Tokai-Mura, Japan  Stephan Heinitz  Paul Scherrer Institut
(PSI), Villigen, Switzerland  Jan Heyse  European Commission, Joint Research
Centre (JRC), Geel, Belgium  David Jenkins  University of York, United Kingdom
Erwin Jericha  TU Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria
Franz Käppeler† Karlsruhe Institute of Technology, Campus North, IKP, 76021
Karlsruhe, Germany  Yacine Kadi  European Organization for Nuclear Research
(CERN), Switzerland  Atsushi Kimura  Japan Atomic Energy Agency (JAEA), Tokai-
Mura, Japan  Niko Kivel  Paul Scherrer Institut (PSI), Villigen, Switzerland
Michael Kokkoris  National Technical University of Athens, Greece  Yury
Kopatch  Joint Institute for Nuclear Research (JINR), Dubna, Russia  Milan
Krtička  Charles University, Prague, Czech Republic  Deniz Kurtulgil  Goethe
University Frankfurt, Germany  Ion Ladarescu  Instituto de Física Corpuscular,
CSIC - Universidad de Valencia, Spain  Helmut Leeb  TU Wien, Atominstitut,
Stadionallee 2, 1020 Wien, Austria  Jorge Lerendegui-Marco  Universidad de
Sevilla, Spain  Sergio Lo Meo  Agenzia nazionale per le nuove tecnologie
(ENEA), Bologna, Italy  Istituto Nazionale di Fisica Nucleare, Sezione di
Bologna, Italy  Sarah-Jane Lonsdale  School of Physics and Astronomy,
University of Edinburgh, United Kingdom  Daniela Macina  European Organization
for Nuclear Research (CERN), Switzerland  Alice Manna  Istituto Nazionale di
Fisica Nucleare, Sezione di Bologna, Italy  Dipartimento di Fisica e
Astronomia, Università di Bologna, Italy  Trinitario Martínez  Centro de
Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Spain
Alessandro Masi  European Organization for Nuclear Research (CERN),
Switzerland  Cristian Massimi  Istituto Nazionale di Fisica Nucleare, Sezione
di Bologna, Italy  Dipartimento di Fisica e Astronomia, Università di Bologna,
Italy  Pierfrancesco Mastinu  Istituto Nazionale di Fisica Nucleare, Sezione
di Legnaro, Italy  Mario Mastromarco  European Organization for Nuclear
Research (CERN), Switzerland  Francesca Matteucci  Istituto Nazionale di
Fisica Nucleare, Sezione di Trieste, Italy  Dipartimento di Astronomia,
Università di Trieste, Italy  Emilio-Andrea Maugeri  Paul Scherrer Institut
(PSI), Villigen, Switzerland  Annamaria Mazzone  Istituto Nazionale di Fisica
Nucleare, Sezione di Bari, Italy  Consiglio Nazionale delle Ricerche, Bari,
Italy  Emilio Mendoza  Centro de Investigaciones Energéticas Medioambientales
y Tecnológicas (CIEMAT), Spain  Alberto Mengoni  Agenzia nazionale per le
nuove tecnologie (ENEA), Bologna, Italy  Veatriki Michalopoulou  National
Technical University of Athens, Greece  Paolo Maria Milazzo  Istituto
Nazionale di Fisica Nucleare, Sezione di Trieste, Italy  Federica Mingrone
European Organization for Nuclear Research (CERN), Switzerland  Agatino
Musumarra  INFN Laboratori Nazionali del Sud, Catania, Italy  Dipartimento di
Fisica e Astronomia, Università di Catania, Italy  Alexandru Negret  Horia
Hulubei National Institute of Physics and Nuclear Engineering, Romania  Ralf
Nolte  Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116
Braunschweig, Germany  Francisco Ogállar  University of Granada, Spain
Andreea Oprea  Horia Hulubei National Institute of Physics and Nuclear
Engineering, Romania  Nikolas Patronis  University of Ioannina, Greece
Andreas Pavlik  University of Vienna, Faculty of Physics, Vienna, Austria
Jarosław Perkowski  University of Lodz, Poland  Luciano Persanti  Istituto
Nazionale di Fisica Nucleare, Sezione di Bari, Italy  Istituto Nazionale di
Fisica Nucleare, Sezione di Perugia, Italy  Istituto Nazionale di Astrofisica
- Osservatorio Astronomico di Teramo, Italy  José-Manuel Quesada  Universidad
de Sevilla, Spain  Désirée Radeck  Physikalisch-Technische Bundesanstalt
(PTB), Bundesallee 100, 38116 Braunschweig, Germany  Diego Ramos-Doval
Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-
Saclay, F-91406 Orsay Cedex, France  Thomas Rauscher  Department of Physics,
University of Basel, Switzerland  Centre for Astrophysics Research, University
of Hertfordshire, United Kingdom  René Reifarth  Goethe University Frankfurt,
Germany  Dimitri Rochman  Paul Scherrer Institut (PSI), Villigen, Switzerland
Carlo Rubbia  European Organization for Nuclear Research (CERN), Switzerland
Alok Saxena  Bhabha Atomic Research Centre (BARC), India  Peter Schillebeeckx
European Commission, Joint Research Centre (JRC), Geel, Belgium  Dorothea
Schumann  Paul Scherrer Institut (PSI), Villigen, Switzerland  Gavin Smith
University of Manchester, United Kingdom  Nikolay Sosnin  University of
Manchester, United Kingdom  Athanasios Stamatopoulos  National Technical
University of Athens, Greece  Giuseppe Tagliente  Istituto Nazionale di Fisica
Nucleare, Sezione di Bari, Italy  José Tain  Instituto de Física Corpuscular,
CSIC - Universidad de Valencia, Spain  Zeynep Talip  Paul Scherrer Institut
(PSI), Villigen, Switzerland  Ariel Tarifeño-Saldivia  Universitat Politècnica
de Catalunya, Spain  Laurent Tassan-Got  European Organization for Nuclear
Research (CERN), Switzerland  National Technical University of Athens, Greece
Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-
Saclay, F-91406 Orsay Cedex, France  Andrea Tsinganis  European Organization
for Nuclear Research (CERN), Switzerland  Jiri Ulrich  Paul Scherrer Institut
(PSI), Villigen, Switzerland  Sebastian Urlass  European Organization for
Nuclear Research (CERN), Switzerland  Helmholtz-Zentrum Dresden-Rossendorf,
Germany  Stanislav Valenta  Charles University, Prague, Czech Republic  Gianni
Vannini  Istituto Nazionale di Fisica Nucleare, Sezione di Bologna, Italy
Dipartimento di Fisica e Astronomia, Università di Bologna, Italy  Vincenzo
Variale  Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Italy  Pedro
Vaz  Instituto Superior Técnico, Lisbon, Portugal  Alberto Ventura  Istituto
Nazionale di Fisica Nucleare, Sezione di Bologna, Italy  Vasilis Vlachoudis
European Organization for Nuclear Research (CERN), Switzerland  Rosa Vlastou
National Technical University of Athens, Greece  Anton Wallner  Australian
National University, Canberra, Australia  PhilipJohn Woods  School of Physics
and Astronomy, University of Edinburgh, United Kingdom  Tobias Wright
University of Manchester, United Kingdom  Petar Žugec  Department of Physics,
Faculty of Science, University of Zagreb, Zagreb, Croatia

###### Abstract

Background

The 14N(n,p)14C reaction is of interest in neutron capture therapy, where
nitrogen-related dose is the main component due to low-energy neutrons, and in
astrophysics, where 14N acts as a neutron poison in the s-process. Several
discrepancies remain between the existing data obtained in partial energy
ranges: thermal energy, keV region and resonance region.

Purpose

Measuring the 14N(n,p)14C cross section from thermal to the resonance region
in a single measurement for the first time, including characterization of the
first resonances, and providing calculations of Maxwellian averaged cross
sections (MACS).

Method

Time-of-flight technique. Experimental Area 2 (EAR-2) of the neutron time-of-
flight (n_TOF) facility at CERN. 10B(n,$\alpha$)7Li and 235U(n,f) reactions as
references. Two detection systems running simultaneously, one on-beam and
another off-beam. Description of the resonances with the R-matrix code sammy.

Results

The cross section has been measured from sub-thermal energy to 800 keV
resolving the two first resonances (at 492.7 and 644 keV). A thermal cross-
section (1.809$\pm$0.045 b) lower than the two most recent measurements by
slightly more than one standard deviation, but in line with the ENDF/B-VIII.0
and JEFF-3.3 evaluations has been obtained. A 1/v energy dependence of the
cross section has been confirmed up to tens of keV neutron energy. The low
energy tail of the first resonance at 492.7 keV is lower than suggested by
evaluated values, while the overall resonance strength agrees with
evaluations.

Conclusions

Our measurement has allowed to determine the 14N(n,p) cross-section over a
wide energy range for the first time. We have obtained cross-sections with
high accuracy (2.5 %) from sub-thermal energy to 800 keV and used these data
to calculate the MACS for $kT$ = 5 to $kT$ = 100 keV.

##  I INTRODUCTION

The 14N(n,p)14C reaction plays a key role in many fields. It is relevant in
nuclear astrophysics because it is a significant neutron poison in the
s-process nucleosynthesis [1]. Also, this reaction is an important proton
feeder in the production of fluorine, via the chain of reactions
18O(p,$\alpha$)15N($\alpha$,$\gamma$)19F. 19F is a useful tracer of the
physical conditions in stellar interiors, since it can be easily destroyed by
proton or $\alpha$ reactions, hence any production site needs also to enable
19F to escape from the stellar interiors as it is observed with high abundance
in AGB atmospheres [2]. In radiotherapy, the dose in healthy tissues is a
limiting factor. Specifically, in Boron Neutron Capture Therapy (BNCT), the
14N(n,p)14C reaction constitutes the main contribution to the dose in healthy
tissue due to thermal neutrons [3], therefore, it is crucial for determining
the delivered dose in a BNCT treatment [4]. In addition, the International
Commission on Radiation Units and Measurements (ICRU) recommends that the
delivered dose should have less than 5% deviation from the prescribed dose
[5]. At present, nuclear data are under review and upgrade for the new IAEA
Technical Document (TECDOC) on BNCT [6]. An accurate 14N(n,p)14C cross section
is one of most important data to be considered there.

The 14N(n,p)14C reaction has been measured several times, though all of these
measurements have been focused on a specific energy region: thermal energy
(25.3 meV), 1/v region (up to a few tens of keV), integral measurements in the
keV range (25-200 keV) or resonance region (above 400 keV). Thus, there is no
single measurement connecting the thermal energy or the 1/v region with the
resonance region. The first resonance is above 450 keV. Despite the number of
experiments there are some issues that need to be clarified in the different
energy ranges.

At thermal energy, there are several measurements [7, 8, 9, 10, 11, 12, 13]
with values from 1.7 to 2.0 b. The last two provided ($1.93\pm 0.05$ b) [12]
and ($1.868\pm 0.006$ b) [13] and they are higher than the ENDF/B-VIII.0 and
JEFF-3.3 evaluations (1.8271 b) [14]. In BNCT, the disparities between
measurements and evaluations in involved reactions can lead to differences up
to 15 % in the thermal neutron dose estimation in human tissues and 3-4 % in
total dose in no-tumor tissues (including $\gamma$ and boron-induced doses).
Thus, a reduction of the uncertainty in the 14N(n,p) reaction leads to more
accurate treatments approaching to ICRU recommendations [5]. The thermal value
is also relevant in astrophysics. For instance, it has been shown that the
thermal value impacts considerably on the Maxwellian averaged cross section
(MACS) for (n,p) reactions [15].

The only differential measurement available in the 1/v region is by Koehler et
al. [16] that covers the range from 61 meV to 35 keV. It was normalized by
extrapolation to the thermal value in the Nuclear Data Compilation by
Ajzenberg-Selove, at $1.83\pm 0.03$ b [17]. In a second measurement, Koehler
et al. confirmed the assumed value at thermal energy [18], obtaining the same
results as Gledenov et al. [11]. Between 35 and 150 keV, there are no
differential measurements, and there is only derived data from the inverse-
reaction measurement by Gibbons et al. [19].

In the astrophysical range several integral measurements have been carried out
[20, 21, 22, 23, 1]. For all of them there is a good agreement at 25 keV,
except Brehm et al. [20]. However, some differences arise in the measurements
above 25 keV. Shima et al. [23] observed a reduction in the cross-sections
from 1.67 mb at 35.8 keV to 1.19 mb at 67.1 keV, while Gledenov et al. [21]
saw a mostly flat behavior between 24.5 keV and 144 keV with values
oscillating between 2.04 and 2.08 mb. The last measurement by Wallner et al.
[1] encountered a reduction above 25 keV, with values of 0.88 and 0.90 mb at
123 and 178 keV, respectively, in clear disagreement with Gledenov et al.
[21].

In the resonance region the most important measurements were carried out by
Johnson et al. [24] and Morgan [25]. Johnson et al. measured the cross section
from 150 keV to 2.15 MeV, using neutrons from a lithium target bombarded by
protons with an energy spread of 5 keV [24]. Later, Morgan [25] by time-of-
flight measured above 450 keV with better resolution, although he did not
provide an analysis of the resonance parameters. Morgan is the reference for
the evaluations in the resonance region. More recently, based on the
comparison of the aforementioned cross section determined at 123 and 178 keV
(at the low-energy tail of the first resonance at 492.7 keV) with the ENDF
data in this region Wallner et al. suggested a factor of about 3.3 lower
strength for this resonance.

The ENDF/B-VIII.0 evaluation does not provide resonance parameters for this
reaction, and refers to the Compilation by Ajzenberg-Selove [17]. Information
on the resonance parameters could be also obtained via other reactions that
lead to the same compound nucleus [26]. Specifically, the inverse 14C(p,n)14N
reaction, whose threshold allows the observation of the lowest neutron
resonances, has been used for providing information on their $J^{\pi}$ [27,
28, 19, 29]. Other reactions have thresholds above these states of 15N [17].
Some measurements found an anisotropy in the first resonance [28] (indicating
$J>\frac{1}{2}$), while others did not [19]. The neutron polarization
measurement by Niecke et al. [29] reported a positive parity for this state.
On the contrary, negative parity was assigned in another measurement [27] and
compilations [17, 30].

To summarize, although the 14N(n,p)14C cross-section has been measured several
times in different energy ranges, many open questions remain. In order to
solve the discrepancies found in the 14N(n,p)14C reaction, a measurement
covering the range from thermal neutron energy to the first two resonances was
carried out at the Experimental Area 2 of the n_TOF facility at CERN. The
neutron beam at this experimental area presents an excellent compromise
between high neutron flux, in particular at thermal energy, and energy
resolution. The present measurement has covered by far the largest neutron
energy range, and in particular, for the first time has connected the thermal,
1/v and resonance regions. This has allowed an accurate analysis of the
resonances, providing new information on the cross section in different energy
ranges. This measurement is a part of the scientific program of the n_TOF
Collaboration, including a series of experiments aiming at studying reactions
of relevant interest in nuclear astrophysics and in medical physics [31].

##  II EXPERIMENTAL SET-UP

###  II.1 The n_TOF neutron beam

The experiment was performed at the Experimental Area 2 (EAR-2) of the n_TOF
facility at CERN, located around 19.5 m from the neutron production target in
the vertical direction. The neutrons are generated by the 20 GeV/c proton beam
from the CERN Proton Synchrotron (PS) impinging onto a lead target. The
technical features of the facility and the characteristics of the neutron beam
are described in detail in Refs. [32, 33].

###  II.2 Detectors and data acquisition

The experimental setup for charged particle detection consisted of a couple of
separate systems that worked in parallel. The first of them, (upstream) was
based on a stack of micro mesh gaseous structure detectors (MicroMegas), while
the second (downstream) used Double-Sided Silicon Strip Detectors (DSSSD). The
MicroMegas detectors are based on microbulk technology, for which the low-
mass, robustness and neutron and $\gamma$ transparency allow the use of
several detectors along the beam with a minimal perturbation. This allows a
geometrical efficiency close to 50 % when one of the two reaction products are
detected [34]. This type of detectors have been used thoroughly in n_TOF
fission and charged-particle emission measurements, including the neutron flux
determination [33, 35]. A stack of MicroMegas detectors (9.5 cm in diameter)
were mounted in a common reaction chamber as shown in Figure 1, and operated
with a gas mixture of 90 % Ar and 10 % CF4. The 235U and 10B samples were
placed in forward direction, the two nitrogen(adenine) samples were placed in
a back-to-back configuration, and two KCl samples, which were used for a
separate measurement (not analyzed in this work), in the same configuration as
the adenine samples. Additional measurements by replacing the adenine samples
with dummy samples (Al foils as in the substrate of the adenine samples) were
carried out in order to determine the background and reduce systematic
uncertainties.

Figure 1: The MicroMegas setup, with the six targets and six MicroMegas
detectors used in the measurement. Adenine and KCl samples were placed in
back-to-back pairs.

The DSSSD are silicon detectors that provide position sensitivity and allow
background subtraction by means of front-rear strip coincidence analysis. W1
Model DC Strip Detectors with 16$\times$16 strips from Micron Semiconductors
were used [36]. These detectors have to be placed off-beam where a lower beam-
related background is found, at the cost of a lower geometrical efficiency.
The DSSSD allow one to extend the measured neutron energy range on the high
energy and also analyze the angular distribution of the emitted protons. The
setup, shown in Figure 2, consisted of a couple of detectors, one facing the
adenine sample (top) and the other facing the KCl sample (bottom), which was
used for a separate measurement as in the MicroMegas setup. The bottom panel
of Figure 2 shows a simulation of the protons emitted from the sample after
the neutron capture reaction. Protons from the (n,p) reaction impinging on the
DSSSD deposited all its energy inside the Silicon layer. Conversely, those
protons emitted from the adenine sample in backward direction (likewise for
the KCl sample) were absorbed by the Al backings. These samples were replaced
temporarily at the beginning and end of the measurement with 10B samples for
normalization purposes.

Figure 2: Top: The DSSSD setup, with the two samples in the center on the Al
backings (adenine facing upwards and KCl downwards) and two DSSSD, one facing
each sample. Bottom: Simulation to extract the count distribution and detector
efficiency considering isotropic proton emission. The position of the adenine
sample and the DSSSD are indicated, as well as the incoming neutron beam which
serves as the reference direction. The color code corresponds to the proton
track density per primary in the simulation.

The experimental setup was aligned to the nominal beam position. The real
position and spatial profile of the beam was checked by the use of Gafchromic
foils. These are radio-sensitive films that contain a dye that changes color
when exposed to ionising radiation, providing high resolution on the beam
profile distribution. The foils were placed at the position of interest. After
irradiation, data was processed through digital scanning. This information was
also adopted for corrections in the efficiency related to the beam-to-sample
intersection.

The detector signals were acquired by the standard n_TOF Data Acquisition
System (DAQ), based on SPDevices ADQ412DC-3G cards of 2GS/s maximum sampling
rate, 12 bits resolution and 175 MBytes on-board memory [37]. The special
features of these cards ensure the collection of data for a time-of-flight
(TOF) corresponding to neutron energies well below the thermal energy.

The signal induced by the prompt $\gamma$-flash generated in the interaction
of the 20 GeV/c proton beam with the lead target was used as a reference
signal to determine the time of flight of the neutrons.

###  II.3 Samples preparation and characterization

In this measurement, one 235U, one 10B and two 14N samples were used for the
MicroMegas setup. For the DSSSD setup, one 10B and one 14N sample were used.
All the sample deposits were 9 cm in diameter in the case of Micromegas, and 5
cm in diameter in the case of DSSSD, which is larger than the neutron beam.
The 235U sample, enriched to 99.934 %, was prepared with the electrodeposition
method and an areal density of $0.1176\pm 0.0005$ mg/cm2 onto 30 $\mu$m of Al.
The boron samples, with a thickness of 20 nm (MicroMegas) and 25 nm (DSSSD),
were made of 10B4C onto Al by the sputtering method.

The nitrogen samples were made of adenine (C5H5N5) and prepared by thermal
evaporation onto Al at CERN. Adenine was used due to a large nitrogen content.
At the same time, carbon has a low neutron cross section and neutron capture
on hydrogen produces only $\gamma$ radiation that is not detected by the
MicroMegas detectors. In addition, the proton recoils from elastic scattering
of neutrons have lower energy than those from the 14N(n,p) reaction and can be
identified and thus filtered out.

The adenine samples were characterized via Rutherford Back-Scattering (RBS) of
$H^{+}$ with 0.85 MeV at the Centro Nacional de Aceleradores (Spain), where
previous works showed excellent possibilities for sample characterization
[38]. The RBS spectra were analyzed using the SIMNRA package [39]. In the
SIMNRA simulations the Rutherford cross-section for the scattering of H+ in Al
was used. For C, N and H, the evaluated cross section data from the IBANDL
database were used [40].

Considering the dimension of the samples (5 and 9 cm in diameter) and of the
H+ beam spot (3 mm) used for the characterization of the samples, several
points were analyzed for each sample to provide a picture of the homogeneity
of the thickness. The samples were scanned from the edges to the center in
three different directions. In order to perform an accurate and precise
determination of the number of atoms of 14N, few points outside the area
coated with adenine were also analyzed by RBS. This allowed the determination
of any possible contamination of the substrate reducing the free parameters of
the SIMNRA fit of the data. The overall thickness of adenine is revealed both
by the presence of the peak and the reduction in energy of the edge from the
Al substrate. Figure 3 shows an example of SIMNRA fit to the data. The mass
density for each measured point was determined with uncertainty of 1-2 %.

Figure 3:  Example of a single RBS measurement. The results of the SIMNRA fit,
with the detailed contribution from each isotope is also shown with dashed
lines.

We found a smooth reduction of the adenine mass density from the center to the
edges. Within uncertainties, the same mass density was found for points at the
same distance from the center. Figure 4 reveals a parabolic pattern in the
mass density, which was attained through the equation $m=m_{0}-a\cdot r^{2}$.
The parameter $a$ is a measure of the mass distribution throughout the sample,
quantified as the curvature of the quadratic fit, while $m_{0}$ is the mass
density at the center of the samples. The total mass is computed as the
integral of the mass density given by the above mentioned formula. The mass of
each sample was determined with an uncertainty better than 1.5 %. Table 1
summarizes the results for all the samples.

Figure 4: Mass density radial distribution for the Forward adenine sample in the MicroMegas setup. The horizontal error bars match with the size of the probe (3 mm). The quadratic fit is shown with a dashed line.  Sample | $m_{0}$ | $a$ | Total number of atoms
---|---|---|---
| ( at/b) | (at/b/cm2) | ($10^{20}\cdot$at)
DSSSD | 6.88$\cdot 10^{-6}$ | 7.24$\cdot 10^{-8}$ | 1.306$\pm$0.020
Backward MicroMegas | 1.382$\cdot 10^{-5}$ | 2.18$\cdot 10^{-7}$ | 8.79$\pm$0.11
Forward MicroMegas | 1.958$\cdot 10^{-5}$ | 3.91$\cdot 10^{-7}$ | 9.94$\pm$0.12
Table 1: Results of the characterization of the mass density for all the
adenine samples.

##  III DATA ANALYSIS

The digitized signals from MicroMegas detectors and DSSSD were reconstructed
off-line by means of a Pulse Shape Analysis routine described in Ref. [41],
from which information was extracted on the amplitude, area, timing and other
features of the signals. The analysis was done separately for high intensity
(HI) and low intensity (LI) proton pulses from the PS accelerator complex.
High intensity pulses (around 7·1012 protons per bunch) allow larger
statistics, but suffer from a very intense $\gamma$-flash. On the other hand,
low intensity pulses (around 3.5·1012 protons per bunch) profit from a reduced
$\gamma$-flash which allows a better signal identification, specially for
higher neutron energies. The use of LI pulses thus extends the energy range of
the measurement in the high energy region, at the expense of a smaller neutron
flux and hence lower statistics.

Figure 5 shows a 2D histogram of the area of the signals versus their TOF for
the MicroMegas detector facing the 10B sample, where signals from $\alpha$
particles are discriminated from the other reaction products, electronic noise
and pile-up events. The $\alpha$-particles from the two reaction channels: the
decay to the ground state (n, $\alpha_{0}$) and to the first excited state (n,
$\alpha_{1}\gamma$) can be observed around 2.0 and 1.7 in area, respectively.
Some regions with low number of counts are observed, specially below 104 ns,
which correspond to dips in the neutron flux caused by Al in the target and
beam pipes.

Similarly, a threshold in energy deposition has been used to separate the
fission fragments from the signals from $\alpha$ decay and electronic noise
for the detector facing the 235U sample as shown in Figure 6. The Figure shows
the projection of the signal areas on the vertical axis (of a plot similar to
Figure 5) for several TOF ranges. Individual curves were normalized to prove
that the distribution is the same at all energies, hence the correction due to
the fraction of fission events lost below the threshold can be considered to
be the same at all TOF values.

The residual background within the selection thresholds was measured by means
of dummy samples. The relative background at all the neutron energies was
found well below $10^{-3}$ for the 235U and 10B samples, therefore it was
neglected in the analysis.

Figure 5: 2D histogram of deposited energy vs. time of flight for the
MicroMegas detector in forward emission from 10B. The lines indicate the
energy-dependent range applied to select the $\alpha$-particles used in the
analysis. The two regions corresponding to the detection of $\alpha$-particles
and 7Li are clearly distinguished above and below the bottom red line,
respectively. Pile-up events can also be observed above the regular signals
from $\alpha$ particles. The behavior at low TOF is related to the effect of
the $\gamma$-flash.  Figure 6: Energy deposition spectra for seven TOF
intervals at the MicroMegas detector facing the 235U sample. The two-bump
structure corresponds to the fission fragments asymmetric masses. The curves
have been normalized to the same integral between 2 and 18 and indicate that
the fraction of fission fragments lost below the threshold is independent of
the neutron energy.

In the case of the adenine samples, the emitted proton has a lower energy than
the $\alpha$ and 7Li from 10B capture, which makes it more complicated to
separate their signals from the low signal area noise and background. Fittings
of the count distribution along the whole neutron energy range were performed,
in order to estimate the fraction of rejected counts below the selection
threshold. Figure 7 shows the counts from the forward adenine sample and the
dummy sample used to estimate the background for several neutron energy
ranges. The signals from protons between 3.7 and 10 in area can be clearly
distinguished above the background. Note an increase of the noise (signals
with area lower than about 3) in the detector at higher neutron energies. This
noise limits the precision of the background subtraction at neutron energies
above 130 keV. Note also the slight increase in energy deposition at higher
neutron energies, due to kinematics.

Figure 7: Energy deposition spectra for four neutron energy intervals in the
MicroMegas detector facing the forward adenine sample. The adenine spectra
have been normalized to the same integral between 3.7 and 10. The background
spectra were normalized to the adenine ones using the total proton intensity
from the PS pulses.

For the analysis of measurement with DSSSD, only coincidence signals from the
front and rear strips in the detector were considered in order to reduce part
of the background signals appearing at high neutron energies. A time and
signal area coincidence rejection was performed. Figure 8 shows a 2D histogram
of the signal area versus their TOF for the DSSSD facing the adenine sample.
The use of only coincident signals has significant impact specially at TOF
corresponding to the first two resonances, where we already see impact of the
$\gamma$-flash. Only signals within a neutron energy-dependent signal area
region, enclosed in red lines in Figure 8, were considered in the analysis. A
small background was subtracted using collected data from dummy samples (Al
backings). Nonetheless, there was an additional small background contribution
that can not be easily subtracted, which was considered in the R-matrix
(sammy) analysis of the data. Pile-up events are negligible for all neutron
energies due to the low counting rate, given the off-beam location of the
DSSSD. A small amount of boron contamination is observed at large TOF from7Li
and $\alpha$ signals. They have higher signal area than the protons (around
1.5 and 2.8 in area in the plot, respectively), which hence do not affect the
analysis. As mentioned above, the spectra from LI proton pulses allow analysis
up to a higher energy as the background is lower than for the HI ones. Both HI
and LI data were used below 300 keV and only LI data above that energy,
resulting in lower collected statistics in the resonance region.

Figure 8: 2D histogram of deposited energy (signal area) vs. TOF for the DSSSD
facing the adenine sample. The spectra correspond only to the LI pulses. The
red lines indicate the region to select the protons from the 14N(n,p) reaction
used in the analysis. Signals below 0.3 in signal area are not shown as they
are strongly dominated by the electronic noise. The signals corresponding to
the first two resonances can be clearly identified around 2000 ns. The huge
number of events at short TOF (lower than 3·103 ns) is a consequence of the
$\gamma$-flash. The bottom panel is a zoom in the low TOF range.

###  III.1 Energy calibration

The TOF-to-energy calibration was performed according to the method described
in Ref. [42]. The experimental TOF yield was compared to the simulations from
the n_TOF Transport Code, which includes ENDF/B-VIII.0 cross-section
evaluation with the effect of the n_TOF EAR-2 resolution function. This
comparison is shown for the low energy resonances of 235U in Figure 9. There
is an overall good reproduction in the whole range, except in the dips between
some of the resonances, which had already been spotted as disagreements
between the last ENDF/B-VIII.0 and JEFF-3.3 evaluations. The extracted
effective flight path was 19.39 m for the 235U sample position in the
MicroMegas Chamber. This corresponds to the geometrical distance of the
experimental apparatus from the surface of the Pb spallation target. This
flight path was adjusted for the subsequent samples according to their
position inside the Micromegas chamber. For the DSSSD setup, the flight path
was 19.75 m and it was checked by the fitting of the thermal peak and the dips
in the flux observed with the reference 10B sample.

Figure 9: Measured 235U TOF spectra with MicroMegas in the low energy and
resonance region (blue points for LI pulses, black points for HI pulses),
compared to the ENDF/B-VIII.0 evaluation (red line) convoluted with the n_TOF
EAR-2 resolution function by means of the n_TOF Transport Code. Small
differences observed in some valleys come likely from improper values in
ENDF/B-VIII.0 - compare this database e.g. with JEFF-3.3.

###  III.2 Neutron Fluence and normalization

The 14N(n,p) cross section is extracted relative to the 10B(n,$\alpha$) cross
section according to:

$\sigma_{N}(E_{n})=\sigma_{B}(E_{n})\frac{\left(C_{N}(E_{n})-B_{N}(E_{n})\right)\Phi_{B}(E_{n})N_{B}\epsilon_{B}}{\left(C_{B}(E_{n})-B_{B}(E_{n})\right)\Phi_{N}(E_{n})N_{N}\epsilon_{N}},$
(1)

where $C_{X}$ ($X\equiv$ N or B for nitrogen and boron, respectively) is the
total number of counts in the detector at a given neutron energy $E_{n}$ and
$B_{X}$ is that of background counts, $\Phi_{X}$ is the neutron fluence,
$N_{X}$ is the areal density of the sample (in atoms per barn) and
$\epsilon_{X}$ is the efficiency, which accounts for the geometric efficiency
and the event selection thresholds. Reference boron cross-section data was
taken from Ref. [43].

Along with this, the 235U/10B yield ratio was calculated for validation
purposes. A good agreement is found, as shown in Figure 10, comparing the
ratio of the TOF count spectra to the simulations, where the different
detection efficiencies and the neutron beam resolution function are
considered, following Ref. [42]. The effect of neutron flux attenuation due to
the relative position of the uranium and boron samples was also considered.

Figure 10: Measured 235U/10B yield ratio for HI (black) and LI (blue) PS
proton pulses, compared to the ENDF/B-VIII.0 evaluation (red) folded with the
n_TOF EAR-2 resolution function.

###  III.3 Efficiency and dead-time corrections

The efficiency corrections for the Micromegas detectors were determined by
detailed Monte Carlo simulations of the reaction products’ energy loss in the
samples and the gas. The simulations were performed with the MCNP6.2 code
[44]. In these simulations, the actual thickness profiles that were found
experimentally have been used. Energy and angular distributions of emitted
charged-particles are adopted from [45] for the boron sample, and is assumed
as isotropic at the center of mass for U and for adenine samples at low
energy. See Sec. IV.2 for the check of the distribution from N in the
resonance region. The reaction events were assumed to occur uniformly along
the beam direction inside the sample, and the beam profile from the n_TOF
Transport Code was used. Figure 11 shows the efficiency for the forward and
backward adenine samples. As evident from the Figure, the efficiency changes
only weakly. The change is seen (due to kinematics) when the incident neutron
energy becomes comparable to the reaction Q-value. The efficiency at low
neutron energy is different for forward and backward samples due to the
different thickness of the samples (larger for the forward sample), which
becomes relevant for proton emission near grazing angles, specially at higher
energies. Furthermore, the increasing linear momentum transfer contributes to
a larger emission in the forward direction and thus a higher efficiency in the
forward case.

For the DSSSD setup, the geometry of the detectors was implemented in the
simulations, including the silicon layer thickness and the double strip
features, specially regarding the inter-strip spacing. The positioning and
orientation of the detector with respect to the sample and the beam were
checked by using an 241Am source and also the counts from the thermal neutron
capture on 10B, assuming isotropic $\alpha$ particle emission. Furthermore,
some of the strips from the DSSSD were malfunctioning and have been kept out
of the analysis. The simulated detection efficiency for the DSSSD adenine
sample is shown in the lower panel of Figure 11.

Figure 11: Upper panel: Simulated Detection Efficiency of the MicroMegas
Detectors. Lower panel: Simulated Detection Efficiency of the DSSSD. Note the
different vertical scale for Micromegas and DSSSD.

Dead-time corrections were computed following the non-paralyzable response
model [46] assuming a fixed dead time for each detector. The dead times were
estimated following two strategies. The first was based on estimating the
dead-time from the FWHM of the signals and the minimum time difference between
consecutive pulses (a sharp cut-off observed in the time-between-pulses
distribution). The second method relied on matching the total yield for low
and high intensity proton pulses, showing agreement with the first method.

###  III.4 Uncertainties

We adopted conservative estimations of the accuracy of the results. The
statistical uncertainty of the MicroMegas data was assessed with the use of a
binning of 10 bins per decade (bpd), ranging from 0.1 % around the thermal
point to the 4-5 % above 10 keV. Statistical uncertainties of the DSSSD data,
at 10 bpd, ranges from 0.4 % at thermal, to 10-15 % in the 10-300 keV range.
Above 300 keV, the need of a better energy resolution due to the presence of
resonances makes us use 100 bpd, at a cost of a higher uncertainty close to 20
% per bin.

The mass of the adenine samples was measured within 1.5 % accuracy for the
MicroMegas samples. Although the neutron energy dependence of the 14N(n,p)
cross-section was determined with respect to 10B at all neutron energies (as
indicated by Eq. 1), the absolute cross-section normalization was made using
the thermal point of the 235U(n,f) reaction, given that it is a standard at
that energy and the U sample mass was known more precisely, with uncertainty
of 0.43 %, than the B mass. The uncertainty of the cross-section of
235U(nth,f) reaction is 0.23 % [43].

The uncertainty related to the angular distribution of the $\alpha$ particles
from the 10B(n,$\alpha$)7Li reaction at higher energies was considered in the
calculation of the efficiency in both the MicroMegas and DSSSD setups
following the accurate data in Ref. [45]. The uncertainty due to the detection
efficiency includes the statistical uncertainty in the simulations of the
proton transport (and $\alpha$ particles for the 10B4C sample), which was
reduced below 0.2 %. Additional uncertainty due to the positioning and
orientation of the samples and DSSSD was estimated by simulations with
perturbations on the geometry to be 1.3 %. The uncertainty in the correction
to the selection cuts was estimated to be 1 % at thermal energy and up to 5 %
in the keV range. The effect of the neutron beam attenuation and neutron
scattering on Al windows in the n_TOF pipes, Kapton windows of the MicroMegas
and DSSSD chambers, the in-beam Micromegas detectors and upstream samples was
assessed via simulations and found around 1 %. Since DSSSD results are
normalized to the MicroMegas data at the 1/v region, additional systematic
uncertainties from this detection system can be dismissed. The sources of
uncertainty are summarized in Table 2.

Component | Uncertainty (%)
---|---
Sample mass 14N | 1.2-1.5
Normalization | 0.65-3
Efficiency and selection cuts | 1.8-5
Neutron Beam attenuation | 1
Statistical MGAS | 0.1-5
Statistical DSSSD | 0.4-20
Table 2: Major sources of uncertainty (in %) of the present 14N(n,p) cross
section. The uncertainties vary depending on the binning and the energy range
and on the sample.

##  IV RESULTS

###  IV.1 Data from MicroMegas and DSSSD

The main goal of this measurement was to obtain a consistent data set spanning
from thermal to the resonance region and to provide a verification of the
first two resonances strengths after a recent paper [1] suggested a possible
reduction by a factor of 3.3.

The measurement with MicroMegas detectors has covered the range from 8 meV to
80 keV with the backward sample, and up to 130 keV with the forward sample.
The extended range for the forward sample is due to its higher mass and
slightly higher efficiency at these energies, which leads to an improved
signal-to-background ratio. The results from both samples agree with each
other within uncertainties. The measurement covers the 1/v range, including
the thermal point, reproducing and extending the data by Koehler [16]. The
high-quality measurement with MicroMegas detectors profits from thick samples
and a large detection efficiency.

The measurement with DSSSD detectors then allows to extend the range from
thermal to 800 keV. This allows to fully cover the astrophysical range of
interest, and allows to determine the parameters of the first two observed
neutron resonances. The data from DSSSD have a lower counting statistics due
to a smaller thickness of the sample and lower geometrical efficiency. The
DSSSD data have been normalized to that of MicroMegas detectors in the range 8
meV - 100 eV, where there are data from both detection systems.

Overall, this measurement spans eight orders of magnitude of neutron energy
providing for the first time a common consistent dataset for the thermal and
1/v range, the astrophysical range and the resonance region. Figure 12 shows
the experimental yield corrected for areal density ($Y/N$). This quantity
differs from the cross-section only by the effect of the n_TOF EAR-2
resolution function. Data is presented for both MicroMegas detectors
(separately for the forward and backward samples and HI and LI proton pulses)
and DSSSD (merged HI and LI below 300 keV, and only LI above 300 keV).

Figure 12: 14N(n,p) Yield/Areal Density ($Y/N$) from the experiment. Data are
shown at 10 bins per decade below 300 keV and 100 bins per decade above 300
keV. MicroMegas results are separated for forward and backward samples, and
also in HI and LI PS proton pulses.

The cross-section derived from this yield by means of its fitting with the
R-Matrix based sammy code [47] will be shown below. Before this, the angular
distribution of the proton emission in the first resonance will be discussed.

###  IV.2 Angular distribution of protons from the 492.7 keV resonance

Previous measurements of the 14N(n,p) reaction did not carry out any analysis
of angular distribution of protons emitted from the resonances. As the DSSSD
detects protons emitted only in a range of angles, the knowledge of the
angular distribution of emitted protons is crucial for the cross-section
determination. In practice, the DSSSD allows to check the distribution for the
first time, even considering its moderate angular resolution. Any deviation
from isotropy would be an indication that the spin of these resonances is
$J>\frac{1}{2}$ and would complicate the determination of the cross-section,
given the relevance of the angular distribution in the efficiency calculation
of the DSSSD set-up. The spin and parity for the corresponding 15N state was
assigned as $\frac{1}{2}^{-}$ from a measurement of the 14C(p,$\gamma$)
reaction [27]. Previous measurements of the inverse reaction 14C(p,n)14C then
determined the angular distribution of neutron emission, with Sanders [28]
observing a possible anisotropy but attributing it to target non-uniformity,
and later Gibbons et al. not observing any anisotropy at the center of mass
[19].

The angular distribution of the protons emitted from the 492.7 keV resonance
was analyzed by means of the counts at individual strips in the DSSSD.
Dedicated MCNP simulations were run using an isotropic proton distribution in
the Center of Mass reference system. Protons were generated along the adenine
sample with a spatial distribution given by the neutron beam profile at a
distance of 19.75 m from the n_TOF target and the proton energy corresponding
to the center of the resonance. Figure 13 shows the count distribution in the
strips of the detector in the horizontal direction that is more sensitive to
the angular distribution. The experimental data is in agreement with a
distribution arising from protons emitted isotropically. The observed result,
compatible with isotropy, is in line with the spin adopted from compilations
($J=\frac{1}{2}$) for the first resonance.

For the determination of the cross section (and resonance parameters) we also
need to know the angular distribution from the second resonance at 644 keV. A
count distribution compatible with isotropy was also found for the second
resonance (though with fewer statistics), also in line with the
$J=\frac{1}{2}$ from the Compilation in Ref. [30].

Figure 13: Experimental counts at the horizontal strips of the DSSSD (black),
compared with the simulated distribution of counts for protons emitted
isotropically (red). Data are normalized so that the total number of counts
(from all active strips) is one. Error bars of the experimental data
correspond to statistical uncertainty.

###  IV.3 R-Matrix Analysis

To deduce the cross-section from the DSSSD yield, data were fitted using the
R-matrix codesammy [47], applying the Reich-Moore approximation.

In order to illustrate the quality of the sammy fit to the yield data, Figure
14 shows the experimental and fitted yield corrected for the sample areal
density. In addition, the deduced cross-section (at 300 K) from the sammy is
given. The ENDF/B-VIII.0 evaluation and the Wallner et al. results are also
shown for comparison. Multiple scattering and self-shielding effects were
found negligible given the small thickness of the adenine samples. A small
constant background was considered in the fit and it was found to be 0.42 mb.
It has no impact on derived resonance parameters and on the cross-section in
the 1/v region. However, subtracting a constant background becomes relevant at
neutron energies between about 50 and 300 keV if we want to reproduce
simultaneously the data with the resonance parameters. Furthermore,
subtracting this small background is only needed for the DSSSD data, since the
MicroMegas yield is fully consistent with no background contribution. We would
like to note that the actual background considered in DSSSD data must not
necessarily be exactly constant over the whole fitted energies but only have a
similar value to that required near 100 keV. As the deduced cross-section from
n_TOF in this region agrees perfectly with Wallner et al. data, we have a high
confidence that this region is treated correctly.

In the present analysis, the $J^{\pi}$ of both resonances was assumed from
Ref. [17]. The channel radii were taken as 5.5 fm; $\Gamma_{\gamma}$,
$\Gamma_{\alpha}$ and $E_{R}$ were fixed to values from Ref. [30], while
$\Gamma_{n}$ and $\Gamma_{p}$ were fitted. The impact of the exact
$\Gamma_{\gamma}$ and $\Gamma_{\alpha}$ on the fit is negligible provided that
they are much smaller than the other widths. from Ref [30]. The 432 keV
resonance, reported in Ref. [30] and present in the total cross-section of
nitrogen [48], was not observed neither in this measurement nor in any other
papers reporting results at this energy from the 14N(n,p) [24] or the 14C(p,n)
reaction [19, 49]. Therefore, the $\Gamma_{p}$ of this resonance was fixed to
zero. Bound states were included in the analysis in order to reproduce the 1/v
behavior of this reaction below tens of keV. Their positions were again taken
from Ref. [30], while $\Gamma_{n}$ and $\Gamma_{p}$ were adjusted. Other
higher-lying resonances (up to 1.5 MeV) have also been included in the
analysis, fixing all parameters to those in Ref. [30].

Figure 14: The Yield data corrected for the areal density ($Y/N$) are shown in
black. The red line is the sammy fit of the ($Y/N$) data, the blue line is the
cross-section at 300 K deduced from parameters obtained with sammy. The
integral measurements by Wallner et al. at 25, 123 and 178 keV are shown in
magenta. The ENDF/B-VIII.0 evaluation is included (in green). The upper panel
shows the full range covered by this measurement, and the lower panel shows a
detail of the resonance region.

The experimental yield was consistently described in the range from 8 meV to
800 keV with the sammy fit. The resonance partial widths and resonance
strengths, defined as $g\Gamma_{n}\Gamma_{p}/\Gamma$, where
$\Gamma=\Gamma_{n}+\Gamma_{p}+\Gamma_{\alpha}+\Gamma_{\gamma}$ is the total
resonance width and the statistical factor $g=(2J+1)/[(2I+1)(2i+1)]$, with
$J$, $I$ and $i$ the spins of the resonant state, the target ($1^{+}$) and the
projectile ($\frac{1}{2}^{+}$), respectively, are listed in Table 3.

$E_{R}$ (keV) | $J^{\pi}$ |  $\Gamma_{\gamma}$ (eV) |  $\Gamma_{\alpha}$ (keV) |  $\Gamma_{n}$ (keV) |  $\Gamma_{p}$ (keV) |  $g\Gamma_{n}\Gamma_{p}/\Gamma$ (keV)
---|---|---|---|---|---|---
432 | $\frac{7}{2}^{+}$ | $-$ | $-$ | 1.86 | 0.0 | 0.0
492.7 | $\frac{1}{2}^{-}$ | $0.29$ | $-$ | $1.90\pm 0.15$ | $6.2\pm 0.8$ | $0.48\pm 0.04$
644 | $\frac{1}{2}^{+}$ | $4.2$ | $0.0$ | $35\pm 5$ | $9.2\pm 0.7$ | $2.41\pm 0.22$
837 | $\frac{1}{2}^{+}$ | $19.2$ | $0.0$ | $4.0$ | $400.9$ | 1.32
997 | $\frac{3}{2}^{+}$ | $-$ | $-$ | $43.5$ | 0.8 | 0.52
1116 | $\frac{3}{2}^{-}$ | $-$ | $-$ | $12.7$ | 4.4 | 2.18
1184 | $\frac{5}{2}^{+}$ | $-$ | $-$ | 1.3 | $-$ | $-$
1211 | $\frac{1}{2}^{-}$ | $-$ | 0.26 | $14$ | $0.4$ | 0.13
1351 | $\frac{5}{2}^{+}$ | $-$ | 0.4 | $19$ | $0.8$ | 0.75
1405 | $\frac{3}{2}^{-}$ | $-$ | 1.8 | $42$ | $11$ | 5.6
Table 3: Parameters involved in the sammy fit of the first two 14N(n,p)14C
resonances. All values without error correspond to fixed parameters in the
analysis: $J^{\pi}$ was taken from Ref [17], $\Gamma_{\gamma}$,
$\Gamma_{\alpha}$ and $E_{R}$ fixed using the expectation values from Ref.
[30]; $\Gamma_{\alpha}=0$ was used in the fitting of the 644 keV resonance,
Ref. [30] gives $\Gamma_{\alpha}<0.3keV$. The 432 keV resonance was not
observed and thus $\Gamma_{p}$ was set to zero. The (n,p) resonance strengths
$g\Gamma_{n}\Gamma_{p}/\Gamma$ were derived from individual resonance
parameters. Uncertainties correspond to the sum of statistical uncertainties
(from sammy fit) and systematic uncertainties (from normalization of DSSSD
data).

As mentioned above, the fit of the experimental data includes the effect of
the EAR-2 Resolution Function, which is specially relevant in the resonance
region, as clearly seen in the lower panel of Figure 14. The Resolution
Function broadens the resonances but also shifts the maximum of the resonance
in the yield towards lower energy.

The n_TOF cross-section describes well the 1/v behavior up to 50 keV. In
contrast, the ENDF/B-VIII.0 evaluation shows a slight deviation from 1/v
starting from $\approx$3 keV. In the resonance region, the n_TOF cross-section
is consistent within uncertainties with the ENDF/B-VIII.0 evaluation; in terms
of the integrated cross-section of the resonance, between 450 and 550 keV, the
n_TOF reconstructed cross-section is 5.1 % lower.

A noteworthy situation appears at the low-energy tail of the first resonance
(between about 50 and 450 keV), where our cross section differs significantly
from the current ENDF/B-VIII.0 evaluation. However, the n_TOF cross-section
provides a much more consistent shape with the JENDL-5 evaluation in this
range. Our shape in this region is also consistent with the data by Johnson et
al. [24]. Additionally, we are fully consistent with Wallner et al. [1] at 127
and 178 keV. The disagreement between ENDF/B-VIII.0 and their cross-section
led Wallner et al. [1] to propose a reduction on the strength of the first
resonance by a factor of about 3.3. However, this proposal was based on the
assumption that the cross-section energy dependence in ENDF/B-VIII.0 is
correct in the region measured by Wallner et al.. We thus conclude that the
experimental data of Wallner et al., at 127 and 178 keV, as well as those of
Johnson et al. and Morgan at higher energies, are correct, in disagreement
with the ENDF/B-VIII.0 evaluation in $E_{n}\approx 3-450$ keV.

###  IV.4 Thermal Cross-section

The R-matrix fit of the corrected experimental yield ($Y/N$) allowed also the
extraction of the thermal cross-section of the 14N(n,p)14C reaction. It is
found to be $1.809\pm 0.045$ b. Figure 15 compares this value with results of
previous measurements and also with present evaluations. Our result is in
agreement with ENDF/B-VIII.0 (JEFF-3.3), while it is lower than the JENDL-5
evaluation, which adopts the original value reported by Wagemans et al. [12].
Our result is also compatible within uncertainties with the Compilation of the
Atlas of Neutron Resonances by Mughabghab. Compared to the most recent and
very precise measurement by Kitahara et al. [13], our values is lower by about
1.3 standard deviations. We are also in good agreement with the measurements
of Gledenov et al. [11], as well as with the thermal cross-section from the
data by Koehler et al. [18]. It is lower, but only by about 1.2 standard
deviations than results obtained by Wagemans et al., after renormalization of
their value due to a change in the 235U(nth,f) cross section used as reference
[43]. The same procedure was followed for other previous measurements, for
instance for Refs. [18, 11], measured relative to 6Li(n,t).

Figure 15:  14N(n,p)14C thermal values. ENDF/B-VIII.0 and JEFF-3.3 (blue),
JENDL-5 (green) and Atlas of Neutron Resonances (magenta, labelled ATLAS) [30]
are indicated with the dashed lines, with semi-transparent bands corresponding
to uncertainty. Experimental values are marked with squares, our value is
shown in red.

###  IV.5 Maxwellian Averaged Cross-Section

Maxwellian Averaged Cross-Sections (MACS) have been calculated for thermal
energies in the range of $kT$ = 5-100 keV, using the cross-section obtained
from sammy. The uncertainties are estimated considering a 2.5 % uncertainty in
the whole 1/v region, and the uncertainties in the resonance parameters as
given in Table 3. The results are listed in Table 4, together with values
given by Wallner et al. [1] and those derived from the ENDF/B-VIII.0
evaluation cross-section. All three MACS agree within uncertainties for $kT$
below about 15 keV. For higher $kT$ the different behavior of the tail of the
first resonance results in differences in MACS from different sources.
Specifically, the higher cross-section considered in ENDF/B-VIII.0 above a
neutron energy of about 40 keV makes our MACS smaller. The Wallner et al. MACS
values above $kT\approx$ 60 keV are strongly impacted by their suggestion
related to the strength of the first resonance.

kT (keV) | Wallner et al. | ENDF/B-VIII.0 | n_TOF
---|---|---|---
5 | $3.78\pm 0.06$ | 3.81 | $3.91\pm 0.10$
8 | $3.12\pm 0.05$ | 3.01 | $3.09\pm 0.08$
10 | $2.89\pm 0.05$ | 2.70 | $2.76\pm 0.07$
15 | $2.47\pm 0.04$ | 2.26 | $2.26\pm 0.06$
20 | $2.21\pm 0.04$ | 2.02 | $1.97\pm 0.05$
23 | $2.09\pm 0.04$ | 1.93 | $1.84\pm 0.04$
25 | $2.03\pm 0.04$ | 1.88 | $1.77\pm 0.04$
30 | $1.93\pm 0.04$ | 1.80 | $1.63\pm 0.04$
40 | $1.85\pm 0.05$ | 1.75 | $1.47\pm 0.03$
50 | $1.83\pm 0.06$ | 1.86 | $1.46\pm 0.03$
60 | $1.84\pm 0.07$ | 2.23 | $1.69\pm 0.04$
80 | $1.84\pm 0.08$ | 3.96 | $3.14\pm 0.10$
100 | $1.83\pm 0.08$ | 6.92 | $5.83\pm 0.20$
Table 4: Maxwellian Averaged Cross Sections derived from the n_TOF cross-
section, compared with the previous calculation by Wallner et al. [1] and the
value based on theENDF/B-VIII.0 evaluation cross-section [14]. Total
uncertainties are given.

##  V SUMMARY AND CONCLUSIONS

A new measurement of the 14N(n,p)14C reaction has been performed at the EAR-2
of the n_TOF facility at CERN. The measurement provides nuclear data from sub-
thermal to the resonance region for the first time, spanning from 8 meV to 800
keV. The cross-section is obtained via fitting the experimental yield using
the sammy code. The obtained thermal cross-section is 1.809$\pm$0.045 b, in
good agreement with ENDF/B-VIII.0 and JEFF-3.3, lower than the JENDL-5
evaluation and by slightly more than one standard deviation lower than values
reported from the two most recent dedicated measurements by Wagemans et al.
[12] and Kitahara et al. [13]. Our dependence of the cross-section on neutron
energy then starts to differ from ENDF/B-VIII.0 and JEFF-3.3 evaluations above
about 3 keV. The 1/v cross-section dependence is observed for all energies up
to about 50 keV and we observe significant disagreement with respect to these
evaluations between about 50 and 450 keV, at the low-energy tail of the first
resonance at 492.7 keV. On the other hand, our cross-section in this range
nicely reproduces the cross sections at 25, 123 and 178 keV obtained by
Wallner et al. [1]. Our resonance integrals of the first two resonances at
492.7 and 644 keV are consistent with the values reported by Morgan and
adopted by evaluations. These data could promote new evaluations of the cross-
section of the 14N(n,p) reaction. With our cross-section data, a calculation
of the MACS is carried out and the results show a good agreement with MACS
deduced from evaluations at $kT$ below 15 keV with discrepancies at higher
$kT$.

###### Acknowledgements.

We thank Mr. Wilhelmus Vollenberg for the preparation of the Adenine samples.
For the purpose of open access, the author has applied a Creative Commons
Attribution (CC BY) licence to any Author Accepted Manuscript version arising
from this submission. This work was partially supported by Spanish Ministerio
de Ciencia e Innovación (PID2020-117969RB-I00), Junta de Andalucía (FEDER
Andalucia 2014–2020) projects P20-00665 and B-FQM-156-UGR20. This work was
also supported by the UK Science and Facilities Council (ST/M006085/1,
ST/P004008/1 ), and the European Research Council ERC-2015-StG Nr. 677497.
Also by the funding agencies of the n_TOF participating institutes. P. T.
acknowledges support from the Spanish Ministry of Science, Innovation and
Universities under the FPU grant FPU17/02305.

## References

  * Wallner  _et al._ [2016] A. Wallner, M. Bichler, K. Buczak, I. Dillmann, F. Käppeler, A. Karakas, C. Lederer, M. Lugaro, K. Mair, A. Mengoni, G. Schätzel, P. Steier, and H. P. Trautvetter, Accelerator mass spectrometry measurements of the ${}^{13}\mathrm{C}(n,\gamma)^{14}\mathrm{C}$ and ${}^{14}\mathrm{N}(n,p)^{14}\mathrm{C}$ cross sections, Phys. Rev. C 93, 045803 (2016).
  * Abia  _et al._ [2015] C. Abia, K. Cunha, S. Cristallo, , and P. de Laverny, The origin of fluorine: abundances in AGB carbon stars revisited, Astronomy and Astrophysics 581, 8 (2015).
  * Goorley  _et al._ [2002] J. T. Goorley, W. S. Kiger III, and R. G. Zamenhof, Reference dosimetry calculations for neutron capture therapy with comparison of analytical and voxel models, Medical Physics 29, 145 (2002), https://aapm.onlinelibrary.wiley.com/doi/pdf/10.1118/1.1428758 .
  * Barth  _et al._ [2012] R. F. Barth, M. H. Vicente, O. K. Harling, W. S. K. III, K. J. Riley, P. J. Binns, F. M. Wagner, M. Suzuki, T. Aihara, I. Kato, and S. Kawabata, Current status of boron neutron capture therapy of high grade gliomas and recurrent head and neck cancer, Radiation Oncology 7, 10.1186/1748-717X-7-146 (2012).
  * ICR [1992] _ICRU Rep. 46_ , Tech. Rep. (International Commission on Radiation Units and Measurements, Bethesda, MD, 1992).
  * International Society for Neutron Capture Therapy () [ISNCT] International Society for Neutron Capture Therapy (ISNCT), IAEA technical meeting 2022.
  * Batchelor and Flowers [1949] R. Batchelor and B. H. Flowers, Thermal neutron capture in nitrogen. Atomic Energy Research Establishment Report  (1949).
  * Coon and Nobles [1949] J. H. Coon and R. A. Nobles, Disintegration of ${}^{3}{\mathrm{He}}$ and ${}^{14}{\mathrm{N}}$ by Thermal Neutrons, Phys. Rev. 75, 1358 (1949).
  * P.Cuer  _et al._ [1951] P.Cuer, J-P.Longchamp, and S.Gorodetzky, Determination of the cross section for reactions of thermal neutrons on nitrogen, Journal de Physique 12, 6S (1951).
  * Hanna  _et al._ [1961] G. C. Hanna, D. B. Primeau, and P. R. Tunnicliffe, Thermal neutron cross sections and resonance integrals of the reactions O17(n,$\alpha$)C14, Ar36(n,$\alpha$)S33, and N14(n,p)C14, Canadian Journal of Physics 39, 1784 (1961), https://doi.org/10.1139/p61-201 .
  * Gledenov  _et al._ [1993] Y. M. Gledenov, V. I. Salatski, and P. V. Sedyshev, The 14N(n, p)14C reaction cross section for thermal neutrons, Zeitschrift für Physik A Hadrons and Nuclei 346, 307–308 (1993).
  * Wagemans  _et al._ [2000] J. Wagemans, C. Wagemans, G. Goeminne, and P. Geltenbort, Experimental determination of the ${}^{14}\mathrm{N}{(n,p)}^{14}\mathrm{C}$ reaction cross section for thermal neutrons, Phys. Rev. C 61, 064601 (2000).
  * Kitahara  _et al._ [2019] R. Kitahara, K. Hirota, S. Ieki, T. Ino, Y. Iwashita, M. Kitaguchi, J. Koga, K. Mishima, A. Morishita, N. Nagakura, H. Oide, H. Otono, Y. Seki, D. Sekiba, T. Shima, H. M. Shimizu, N. Sumi, H. Sumino, K. Taketani, T. Tomita, T. Yamada, S. Yamashita, M. Yokohashi, and T. Yoshioka, Improved accuracy in the determination of the thermal cross section of ${}^{14}{N}(n,p){}^{14}{C}$ for neutron lifetime measurement, Progress of Theoretical and Experimental Physics 2019, 10.1093/ptep/ptz096 (2019), 093C01, https://academic.oup.com/ptep/article-pdf/2019/9/093C01/30024844/ptz096.pdf .
  * Chadwick  _et al._ [1999] M. Chadwick, P. Young, G. M. Hale, and et al.,  _Technical Report No. LA-UR-99-1222_ , Tech. Rep. (Los Alamos National Laboratory (LANL), 1999).
  * Druyts  _et al._ [1994] S. Druyts, C. Wagemans, and P. Geltenbort, Determination of the 35Cl(n, p)35S reaction cross section and its astrophysical implications, Nuclear Physics A 573, 291 (1994).
  * Koehler and O’Brien [1989] P. E. Koehler and H. A. O’Brien, ${}^{14}\mathrm{N}$(n,p${)}^{14}$C cross section from 61 meV to 34.6 keV and its astrophysical implications, Phys. Rev. C 39, 1655 (1989).
  * Ajzenberg-Selove [1986] F. Ajzenberg-Selove, Energy levels of light nuclei A = 13-15, Nuclear Physics A 449, 1 (1986).
  * Koehler [1993] P. E. Koehler, ${}^{14}\mathrm{N}$(n,p${)}^{14}$C cross section near thermal energy, Phys. Rev. C 48, 439 (1993).
  * Gibbons and Macklin [1959] J. H. Gibbons and R. L. Macklin, Total Neutron Yields from Light Elements under Proton and Alpha Bombardment, Phys. Rev. 114, 571 (1959).
  * Brehm  _et al._ [1988] K. Brehm, H. W. Becker, C. Rolfs, H. P. Trautvetter, F. Käppeler, and W. Ratynski, The cross section of14N(n, p)14C at stellar energies and its role as a neutron poison for S-process nucleosynthesis, Zeitschrift für Physik A Atomic Nuclei 330, 167–172 (1988).
  * Gledenov  _et al._ [1994] Y. M. Gledenov, V. I. Salatski, P. V. Sedyshev, M. V. Sedysheva, V. A. Pshenichnyj, and J. Andrzejewski, Cross sections of the 14N(n, p)14C reaction at 24.5, 53.5 and 144 keV, Zeitschrift für Physik A Hadrons and Nuclei 348, 199–200 (1994).
  * Sanami  _et al._ [1997] T. Sanami, M. Baba, I. Matsuyama, S. Matsuyama, T. Kiyosumi, Y. Nauchi, and N. Hirakawa, Measurement of 14N(n,p)14C cross section for kT = 25.3 keV Maxwellian neutrons using gridded ionization chamber, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 394, 368 (1997).
  * Shima  _et al._ [1997] T. Shima, T. Kii, T. Kikuchi, F. Okazaki, T. Kobayashi, T. Baba, Y. Nagai, and M. Igashira, Experimental Studies of keV Energy Neutron-Induced Reactions Relevant to Astrophysics and Nuclear Physics, JAERI Conference 97 (1997).
  * Johnson and Barschall [1950] C. H. Johnson and H. H. Barschall, Interaction of Fast Neutrons with Nitrogen, Phys. Rev. 80, 818 (1950).
  * Morgan [1979] G. L. Morgan, Cross Sections for the 14N(n,p0), (n,$\alpha$0), and (n,$\alpha$1) Reactions from 0.5 to 15 MeV, Nuclear Science and Engineering 70, 163 (1979), https://doi.org/10.13182/NSE79-A19649 .
  * deBoer  _et al._ [2020] R. J. deBoer, Q. Liu, Y. Chen, M. Couder, J. Görres, E. Lamere, A. Long, S. Lyons, K. Manukyan, L. Morales, D. Robertson, C. Seymour, G. Seymour, E. Stech, B. V. Kolk, and M. Wiescher, Global R-matrix analysis of the 11N($\alpha$,n)14N reaction, Journal of Physics: Conference Series 1668, 012011 (2020).
  * Bartholomew  _et al._ [1955] G. A. Bartholomew, F. Brown, H. E. Gove, A. E. Litherland, and E. B. Paul, Capture Radiation And Neutrons From The Bombardment Of C14 With Protons, Canadian Journal of Physics 33, 441 (1955), https://doi.org/10.1139/p55-053 .
  * Sanders [1956] R. M. Sanders, Study of the ${\mathrm{C}}^{14}(p,n){\mathrm{N}}^{14}$ and ${\mathrm{C}}^{14}(\alpha,n){\mathrm{O}}^{17}$ Reactions, Phys. Rev. 104, 1434 (1956).
  * Niecke  _et al._ [1977] M. Niecke, M. Niemeier, R. Weigel, and H. Wirzba-Lorenz, Angular distributions of neutron polarization from the 14C(p,n)14N and 11B($\alpha$,n)14N reactions and R-matrix analysis of 15N in the excitation-energy range between 11.5 and 12.5 MeV, Nuclear Physics A 289, 408 (1977).
  * Mug [2018] Recommended Thermal Cross Sections, Resonance Properties, and Resonance Parameters for Z = 1–60, in  _Atlas of Neutron Resonances (Sixth Edition)_, edited by S. Mughabghab (Elsevier, Amsterdam, 2018) sixth edition ed., pp. 89–822.
  * Chiaveri, E.  _et al._ [2020] Chiaveri, E., Aberle, O., Alcayne, V., Amaducci, S., Andrzejewski, J., Audouin, L., Babiano-Suarez, V., Bacak, M., Barbagallo, M., Bennett, S., Berthoumieux, E., Bosnar, D., Brown, A.S., Busso, M., Caamaño, M., Caballero, L., Calviani, M., Calviño, F., Cano-Ott, D., Casanovas, A., Cerutti, F., Colonna, N., Cortés, G.P., Cortés-Giraldo, M.A., Cosentino, L., Cristallo, S., Damone, L.A., Davies, P.J., Diakaki, M., Dietz, M., Domingo-Pardo, C., Dressler, R., Ducasse, Q., Dupont, E., Durán, I., Eleme, Z., Fernández-Domíngez, B., Ferrari, A., Ferro-Gonçalves, I., Finocchiaro, P., Furman, V., Garg, R., Gawlik, A., Gilardoni, S., Göbel, K., González-Romero, E., Guerrero, C., Gunsing, F., Heinitz, S., Heyse, J., Jenkins, D.G., Jericha, E., Jiri, U., Junghans, A., Kadi, Y., Käppeler, F., Kimura, A., Knapová, I., Kokkoris, M., Kopatch, Y., Krticka, M., Kurtulgil, D., Ladarescu, I., Lederer-Woods, C., Lerendegui-Marco, J., Lonsdale, S.-J., Macina, D., Manna, A., Martínez, T., Masi, A., Massimi, C., Mastinu, P.F., Mastromarco, M., Maugeri, E., Mazzone, A., Mendoza, E., Mengoni, A., Michalopoulou, V., Milazzo, P.M., Millán-Callado, M.A., Mingrone, F., Moreno-Soto, J., Musumarra, A., Negret, A., Ogállar, F., Oprea, A., Patronis, N., Pavlik, A., Perkowski, J., Petrone, C., Piersanti, L., Pirovano, E., Porras, I., Praena, J., Quesada, J.M., Ramos Doval, D., Reifarth, R., Rochman, D., Rubbia, C., Sabaté-Gilarte, M., Saxena, A., Schillebeeckx, P., Schumann, D., Sekhar, A., Smith, A.G., Sosnin, N., Sprung, P., Stamatopoulos, A., Tagliente, G., Tain, J.L., Tarifeño-Saldivia, A.E., Tassan-Got, L., Thomas, B., Torres-Sánchez, P., Tsinganis, A., Urlass, S., Valenta, S., Vannini, G., Variale, V., Vaz, P., Ventura, A., Vescovi, D., Vlachoudis, V., Vlastou, R., Wallner, A., Woods, P.J., Wright, T.J., and Zugec, P., Status and perspectives of the neutron time-of-flight facility n_TOF at CERN, EPJ Web Conf. 239, 17001 (2020).
  * Weiß  _et al._ [2015] C. Weiß, E. Chiaveri, S. Girod, V. Vlachoudis, O. Aberle, S. Barros, I. Bergström, E. Berthoumieux, M. Calviani, C. Guerrero, M. Sabaté-Gilarte, A. Tsinganis, J. Andrzejewski, L. Audouin, M. Bacak, J. Balibrea-Correa, M. Barbagallo, V. Bécares, C. Beinrucker, F. Belloni, F. Bečvář, J. Billowes, D. Bosnar, M. Brugger, M. Caamaño, F. Calviño, D. Cano-Ott, F. Cerutti, N. Colonna, G. Cortés, M. Cortés-Giraldo, L. Cosentino, L. Damone, K. Deo, M. Diakaki, C. Domingo-Pardo, E. Dupont, I. Durán, R. Dressler, B. Fernández-Domínguez, A. Ferrari, P. Ferreira, P. Finocchiaro, R. Frost, V. Furman, S. Ganesan, A. Gheorghe, T. Glodariu, K. Göbel, I. Gonçalves, E. González-Romero, A. Goverdovski, E. Griesmayer, F. Gunsing, H. Harada, T. Heftrich, S. Heinitz, A. Hernández-Prieto, J. Heyse, D. Jenkins, E. Jericha, Y. Kadi, F. Käppeler, T. Katabuchi, P. Kavrigin, V. Ketlerov, V. Khryachkov, A. Kimura, N. Kivel, M. Kokkoris, M. Krtička, E. Leal-Cidoncha, C. Lederer, H. Leeb, J. Lerendegui, M. Licata, S. Lo Meo, D. López, R. Losito, D. Macina, J. Marganiec, T. Martínez, C. Massimi, P. Mastinu, M. Mastromarco, F. Matteucci, E. Mendoza, A. Mengoni, P. Milazzo, F. Mingrone, M. Mirea, S. Montesano, A. Musumarra, R. Nolte, R. Palomo Pinto, C. Paradela, N. Patronis, A. Pavlik, J. Perkowski, I. Porras, J. Praena, J. Quesada, T. Rauscher, R. Reifarth, A. Riego-Perez, M. Robles, C. Rubbia, J. Ryan, A. Saxena, P. Schillebeeckx, S. Schmidt, D. Schumann, P. Sedyshev, G. Smith, A. Stamatopoulos, P. Steinegger, S. Suryanarayana, G. Tagliente, J. Tain, A. Tarifeño-Saldivia, L. Tassan-Got, S. Valenta, G. Vannini, V. Variale, P. Vaz, A. Ventura, R. Vlastou, A. Wallner, S. Warren, M. Weigand, T. Wright, and P. Žugec, The new vertical neutron beam line at the CERN n_TOF facility design and outlook on the performance, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 799, 90 (2015).
  * Sabaté-Gilarte  _et al._ [2017] M. Sabaté-Gilarte, M. Barbagallo, N. Colonna, F. Gunsing, P. Žugec, V. Vlachoudis, Y. H. Chen, A. Stamatopoulos, J. Lerendegui-Marco, M. A. Cortés-Giraldo, A. Villacorta, C. Guerrero, L. Damone, L. Audouin, E. Berthoumieux, L. Cosentino, M. Diakaki, P. Finocchiaro, A. Musumarra, T. Papaevangelou, M. Piscopo, L. Tassan-Got, O. Aberle, J. Andrzejewski, V. Bécares, M. Bacak, R. Baccomi, J. Balibrea, S. Barros, F. Bečvář, C. Beinrucker, F. Belloni, J. Billowes, D. Bosnar, M. Brugger, M. Caamaño, F. Calviño, M. Calviani, D. Cano-Ott, R. Cardella, A. Casanovas, D. M. Castelluccio, F. Cerutti, E. Chiaveri, G. Cortés, K. Deo, C. Domingo-Pardo, R. Dressler, E. Dupont, I. Durán, B. Fernández-Domínguez, A. Ferrari, P. Ferreira, R. J. W. Frost, V. Furman, K. Göbel, A. R. García, A. Gawlik, I. Gheorghe, T. Glodariu, I. F. Gonçalves, E. González, A. Goverdovski, E. Griesmayer, H. Harada, T. Heftrich, S. Heinitz, A. Hernández-Prieto, J. Heyse, D. G. Jenkins, E. Jericha, F. Käppeler, Y. Kadi, T. Katabuchi, P. Kavrigin, V. Ketlerov, V. Khryachkov, A. Kimura, N. Kivel, M. Kokkoris, M. Krtička, E. Leal-Cidoncha, C. Lederer, H. Leeb, M. Licata, S. Lo Meo, S. J. Lonsdale, R. Losito, D. Macina, J. Marganiec, T. Martínez, C. Massimi, P. Mastinu, M. Mastromarco, F. Matteucci, E. A. Maugeri, E. Mendoza, A. Mengoni, P. M. Milazzo, F. Mingrone, M. Mirea, S. Montesano, R. Nolte, A. Oprea, F. R. Palomo-Pinto, C. Paradela, N. Patronis, A. Pavlik, J. Perkowski, J. I. Porras, J. Praena, J. M. Quesada, K. Rajeev, T. Rauscher, R. Reifarth, A. Riego-Perez, M. S. Robles, P. C. Rout, C. Rubbia, J. A. Ryan, A. Saxena, P. Schillebeeckx, S. Schmidt, D. Schumann, P. Sedyshev, A. G. Smith, S. V. Suryanarayana, G. Tagliente, J. L. Tain, A. Tarifeño-Saldivia, A. Tsinganis, S. Valenta, G. Vannini, V. Variale, P. Vaz, A. Ventura, R. Vlastou, A. Wallner, S. Warren, M. Weigand, C. Wolf, P. J. Woods, C. Weiss, and T. Wright, High-accuracy determination of the neutron flux in the new experimental area n_TOF-EAR2 at CERN, The European Physical Journal A 53, 10.1140/epja/i2017-12392-4 (2017).
  * Andriamonje  _et al._ [2011] S. Andriamonje, M. Calviani, Y. Kadi, R. Losito, V. Vlachoudis, E. Berthoumieux, F. Gunsing, A. Giganon, Y. Giomataris, C. Guerrero, R. Sarmento, P. Schillebeeckx, and P. Siegler, A Transparent Detector for n_TOF Neutron Beam Monitoring, J. Korean. Phys. Soc. 59, 1597 (2011).
  * Praena  _et al._ [2018a] J. Praena, M. Sabaté-Gilarte, I. Porras, J. M. Quesada, S. Altstadt, J. Andrzejewski, L. Audouin, V. Bécares, M. Barbagallo, F. Bečvář, F. Belloni, E. Berthoumieux, J. Billowes, V. Boccone, D. Bosnar, M. Brugger, F. Calviño, M. Calviani, D. Cano-Ott, C. Carrapiço, F. Cerutti, E. Chiaveri, M. Chin, N. Colonna, G. Cortés, M. A. Cortés-Giraldo, M. Diakaki, M. Dietz, C. Domingo-Pardo, R. Dressler, I. Durán, C. Eleftheriadis, A. Ferrari, K. Fraval, V. Furman, K. Göbel, M. B. Gómez-Hornillos, S. Ganesan, A. R. García, G. Giubrone, I. F. Gonçalves, E. González-Romero, A. Goverdovski, E. Griesmayer, C. Guerrero, F. Gunsing, T. Heftrich, A. Hernández-Prieto, J. Heyse, D. G. Jenkins, E. Jericha, F. Käppeler, Y. Kadi, D. Karadimos, T. Katabuchi, V. Ketlerov, V. Khryachkov, N. Kivel, P. Koehler, M. Kokkoris, J. Kroll, M. Krtička, C. Lampoudis, C. Langer, E. Leal-Cidoncha, C. Lederer-Woods, H. Leeb, L. S. Leong, J. Lerendegui-Marco, R. Losito, A. Mallick, A. Manousos, J. Marganiec, T. Martínez, C. Massimi, P. Mastinu, M. Mastromarco, E. Mendoza, A. Mengoni, P. M. Milazzo, F. Mingrone, M. Mirea, W. Mondelaers, C. Paradela, A. Pavlik, J. Perkowski, A. J. M. Plompen, T. Rauscher, R. Reifarth, A. Riego-Perez, M. Robles, C. Rubbia, J. A. Ryan, R. Sarmento, A. Saxena, P. Schillebeeckx, S. Schmidt, D. Schumann, P. Sedyshev, G. Tagliente, J. L. Tain, A. Tarifeño Saldivia, D. Tarrío, L. Tassan-Got, A. Tsinganis, S. Valenta, G. Vannini, V. Variale, P. Vaz, A. Ventura, M. J. Vermeulen, V. Vlachoudis, R. Vlastou, A. Wallner, T. Ware, M. Weigand, C. Weiss, T. Wright, and P. Žugec (n_TOF Collaboration), Measurement and resonance analysis of the ${}^{33}\mathrm{S}(n,\alpha)^{30}\mathrm{Si}$ cross section at the CERN n_TOF facility in the energy region from 10 to 300 keV, Phys. Rev. C 97, 064603 (2018a).
  * [36] Micron Semiconductor Ltd., W1 DC Strip Detectors, http://www.micronsemiconductor.co.uk/product/w1/.
  * Masi  _et al._ [2018] A. Masi, A. A. Paiva, R. Cevenini, E. Chiaveri, M. Donzé, S. Gilardoni, A. Giraud, A. H. Prieto, R. Losito, D. Macina, F. Marazita, P. Peronnard, and L. Tassan-Got, The CERN n_TOF Facility Data Acquisition System, in  _Proc. of International Conference on Accelerator and Large Experimental Control Systems (ICALEPCS’17), Barcelona, Spain, 8-13 October 2017_, 16 (JACoW, Geneva, Switzerland, 2018) pp. 1900–1905, https://doi.org/10.18429/JACoW-ICALEPCS2017-THPHA195.
  * Praena  _et al._ [2018b] J. Praena, F. Ferrer, W. Vollenberg, M. Sabaté-Gilarte, B. Fernández, J. García-López, I. Porras, J. Quesada, S. Altstadt, J. Andrzejewski, L. Audouin, V. Bécares, M. Barbagallo, F. Bečvář, F. Belloni, E. Berthoumieux, J. Billowes, V. Boccone, D. Bosnar, M. Brugger, F. Calviño, M. Calviani, D. Cano-Ott, C. Carrapiço, F. Cerutti, E. Chiaveri, M. Chin, N. Colonna, G. Cortés, M. Cortés-Giraldo, M. Diakaki, M. Dietz, C. Domingo-Pardo, R. Dressler, I. Durán, C. Eleftheriadis, A. Ferrari, K. Fraval, V. Furman, K. Göbel, M. Gómez-Hornillos, S. Ganesan, A. García, G. Giubrone, I. Gonçalves, E. González-Romero, A. Goverdovski, E. Griesmayer, C. Guerrero, F. Gunsing, T. Heftrich, A. Hernández-Prieto, J. Heyse, D. Jenkins, E. Jericha, F. Käppeler, Y. Kadi, D. Karadimos, T. Katabuchi, V. Ketlerov, V. Khryachkov, N. Kivel, P. Koehler, M. Kokkoris, J. Kroll, M. Krtička, C. Lampoudis, C. Langer, E. Leal-Cidoncha, C. Lederer, H. Leeb, L. Leong, J. Lerendegui-Marco, R. Losito, A. Mallick, A. Manousos, J. Marganiec, T. Martínez, C. Massimi, P. Mastinu, M. Mastromarco, E. Mendoza, A. Mengoni, P. Milazzo, F. Mingrone, M. Mirea, W. Mondelaers, C. Paradela, A. Pavlik, J. Perkowski, A. Plompen, T. Rauscher, R. Reifarth, A. Riego-Perez, M. Robles, C. Rubbia, J. Ryan, R. Sarmento, A. Saxena, P. Schillebeeckx, S. Schmidt, D. Schumann, P. Sedyshev, G. Tagliente, J. Tain, A. Tarifeño-Saldivia, D. Tarrío, L. Tassan-Got, A. Tsinganis, S. Valenta, G. Vannini, V. Variale, P. Vaz, A. Ventura, M. Vermeulen, V. Vlachoudis, R. Vlastou, A. Wallner, T. Ware, M. Weigand, C. Weiss, T. Wright, and P. Žugec, Preparation and characterization of ${}^{33}S$ samples for ${}^{33}S(n,\alpha)^{30}Si$ cross-section measurements at the n_TOF facility at CERN, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 890, 142 (2018b).
  * Mayer [1997] M. Mayer,  _SIMNRA User’s Guide, Report IPP 9/113_ (Max-Planck-Institut für Plasmaphysik, Garching, Germany, 1997).
  * IBA [2014] _Ion Beam Analysis Nuclear Data Library (IBANDL)_ (IAEA, 2014).
  * Žugec  _et al._ [2016] P. Žugec, C. Weiß, C. Guerrero, F. Gunsing, V. Vlachoudis, M. Sabate-Gilarte, A. Stamatopoulos, T. Wright, J. Lerendegui-Marco, F. Mingrone, J. Ryan, S. Warren, A. Tsinganis, and M. Barbagallo, Pulse processing routines for neutron time-of-flight data, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 812, 134 (2016).
  * Vlachoudis  _et al._ [2021] V. Vlachoudis, M. Sabaté-Gilarte, V. Alcayne, F. Gunsing, E. Mendoza, F. Ogallar, I. Rejwan, M. Bacak, C. Guerrero, C. Massimi, and A. Stamatopoulos,  _On the resolution function of the n_TOF facility: a comprehensive study and user guide_, Tech. Rep. n_TOF-PUB-2021-001 (n_TOF Collaboration (CERN), 2021).
  * Carlson  _et al._ [2018] A. Carlson, V. Pronyaev, R. Capote, G. Hale, Z.-P. Chen, I. Duran, F.-J. Hambsch, S. Kunieda, W. Mannhart, B. Marcinkevicius, R. Nelson, D. Neudecker, G. Noguere, M. Paris, S. Simakov, P. Schillebeeckx, D. Smith, X. Tao, A. Trkov, A. Wallner, and W. Wang, Evaluation of the neutron data standards, Nuclear Data Sheets 148, 143 (2018), special Issue on Nuclear Reaction Data.
  * Werner  _et al._ [2018] C. J. Werner, J. S. Bull, C. J. Solomon, F. B. Brown, G. W. McKinney, M. E. Rising, D. A. Dixon, R. L. Martz, H. G. Hughes, L. J. Cox, A. J. Zukaitis, J. C. Armstrong, R. A. Forster, and L. Casswell,  _MCNP6.2 Release Notes - report LA-UR-18-20808_ (Los Alamos National Laboratory (LANL), 2018).
  * Hambsch and Ruskov [2009] F.-J. Hambsch and I. Ruskov, The 10B(n,$\alpha_{0}$)7Li and 10B(n,$\alpha_{1}\gamma$)7Li Alpha-Particle Angular Distributions for $E_{n}$ $<$ 1 MeV, Nuclear Science and Engineering 163, 1 (2009).
  * Moore [1980] M. Moore, Rate dependence of counting losses in neutron time-of-flight measurements, Nuclear Instruments and Methods 169, 245 (1980).
  * Larson [2008] N. M. Larson,  _Updated users’ guide for SAMMY: Multilevel R-Matrix fits to neutron data using Bayes’ equations_ (Oak Ridge National Laboratory, 2008).
  * Hinchey  _et al._ [1952] J. J. Hinchey, P. H. Stelson, and W. M. Preston, The total neutron cross section of nitrogen, Phys. Rev. 86, 483 (1952).
  * Wang  _et al._ [1991] T. R. Wang, R. B. Vogelaar, and R. W. Kavanagh, ${}^{11}\mathrm{B}$+$\alpha$ reaction rates and primordial nucleosynthesis, Phys. Rev. C 43, 883 (1991).