Proton Recoil Spectra Research Articles

Reanalysis of the β-ν[over ¯]_{e} Angular Correlation Measurement from the aSPECT Experiment with New Constraints on Fierz Interference.

On the basis of revisions of some of the systematic errors, we reanalyzed the electron-antineutrino angular correlation (a coefficient) in free neutron decay inferred from the recoil energy spectrum of the protons which are detected in 4π by the aSPECT spectrometer. With a=-0.104 02(82) the new value differs only marginally from the one published in 2020. The experiment also has sensitivity to b, the Fierz interference term. From a correlated (b,a) fit to the proton recoil spectrum, we derive a limit of b=-0.0098(193) which translates into a somewhat improved 90% confidence interval region of -0.041≤b≤0.022 on this hypothetical term. Tighter constraints on b can be set from a combined [shown as superscript (c)] analysis of the PERKEO III (β asymmetry) and aSPECT measurement which suggests a finite value of b with b^{(c)}=-0.0181±0.0065 deviating by 2.82σ from the standard model.

Simulation of Recoil Proton Spectrum in a Detector of Proton Telescope Type in Registering DT Neutrons

Simulation of Recoil Proton Spectrum in a Detector of Proton Telescope Type in Registering DT Neutrons

Fast neutron energy based modelling of biological effectiveness with implications for proton and ion beams

A practical neutron energy dependent RBE model has been developed, based on the relationship between a mono-energetic neutron energy and its likely recoil proton energy. Essentially, the linear energy transfer (LET) values of the most appropriate recoil proton energies are then used to modify the linear quadratic model radiosensitivities (α and β) from their reference LET radiation values to provide the RBE estimates. Experimental neutron studies published by Hall (including some mono-energetic beams ranging from 0.2 to 15 MeV), Broerse, Berry, and data from the Clatterbridge and Detroit clinical neutron beams, which all contain some data from a spectrum of neutron energies, are used to derive single effective neutron energies (NEeff) for each spectral beam. These energies yield a recoil proton spectrum, but with an effective mean proton energy (being around 50% of NEeff). The fractional increase in LET is given by the recoil proton LET divided by the proton (LETU) value which provides the highest RBE. This ratio is then used to determine the change in the linear-quadratic model α and β parameters, from those of the reference radiation, to estimate the RBE. The predicted proton recoil RBE is then reasonably close to the experimental neutron RBE values found when taking into account the variation inherent in biological experiments. The work has some important consequences. The data of Hall et al (1975 Radiat. Res. 64 245–55) shows that the highest RBE values are found with neutron energies around 0.3–0.4 MeV, but this energy cannot possibly generate recoil proton energies which are higher, as necessary for a 0.68 MeV proton with a 30.5 keV μm−1 LETU (the LET value which provides the maximum obtainable RBE for a specified ion). For 0.4 MeV neutrons with proton recoil energies of around 0.2 MeV, the latter have a LET of around 62.88 keV μm−1. This could have an impact on proton beam RBE modelling. However, this is compensated by finding that the maximum radiosensitivity for mono-energetic neutrons was around 1.7 times larger than previously suggested from experimental ion beam studies, probably due to the necessary spreading out of Bragg peaks for ion beam experimental purposes, sampling errors and particle range considerations. This semi-empirical model can be used with minimal computer support and could have applications in ionic beams and in radioprotection.

Proton inelastic scattering in inverse kinematics as a mean for determining decay rates in continuum: The 9Be + p case

In this work we investigate whether it is feasible with proton inelastic scattering in inverse kinematics to quantify breakup decay rates, by observing the proton recoil in a full kinematics approach. Taking as example the 2.43 MeV excited state of 9Be, we perform an exclusive breakup measurement of 9Be incident on a proton target at an energy of 51 MeV. Two of the three cluster constituents (α and α) as well as the proton target recoil are recorded in a triple coincidence mode. As in other methods we have determined relative α−α and α−n, Q-value and 9Be excitation spectra, energy spectra for all fragments observed and non observed, reconstructed in a full kinematics approach. Additionally to that, we have obtained and concentrated on energy spectra of the proton recoil. The signature of the 9Be configurations were identified in bi-dimensional ΔE−E spectra (proton contour) and decay rates were determined for all three configurations He5+α, Be8+n and α+α+n. Finally a breakup cross section was deduced as σbreak=(142±20)mb. We conclude that proton inelastic excitation to continuum of Borromean light nuclei in inverse kinematics, may provide the mean for probing in the proton recoil spectra the decay rates through all cluster configurations. This involves extensive simulations with the implementation of the experimental conditions and of calculations describing the physics in continuum.

Unfolding simulation of single-energy and continuous fast neutrons spectrum based on micro-pattern gas detector

This paper focuses on the feasibility of fast neutron energy spectrum measurement. The MCNPX and Geant4 are used to simulate two conversion models of stacking neutrons to protons in the triple GEM cathode coupled with multilayer polyethylene, with five kinds of single-energy neutron sources and Am-Be continuous neutron sources taken as research objects. The response function to 160 single energy neutrons and the recoil proton spectrum distribution of the above sources of the detection system are obtained by simulation. Using GRAVEL algorithm and MLEM algorithm and through simulation, the recoil proton spectra of six kinds of fast neutron sources are obtained, and they are further analyzed. The spectrum outcome is compared with the standard input spectrum, showing that they are in good agreement with each other. The relative uncertainty of the unfolding spectrum is around 10%–15%. In this part the relation of gas detector with the precision of unfolding spectrum is also discussed. The result shows that when the energy resolution of micro-pattern gas detection is better than 30%, the accuracy of fast neutron spectrum can meet the needs of practical applications. Furthermore, a new transformation model is proposed based on previous experiments and proves the feasibility of applying micro-pattern gas detector to fast neutron detection of simulation. Moreover, spectrum reconstruction can be achieved by using the obtained recoil proton spectrum combined with a suitable inversion algorithm. The modeling and spectrum analysis of this study can provide a different method of applying the fast neutron detection system composed of micro-pattern gas detectors to the detection of unknown fast neutron sources and also to the source recognition through spectrum reconstruction.

Improved determination of the β−ν¯e angular correlation coefficient a in free neutron decay with the aSPECT spectrometer

This work presents the until now most precise measurement of the angular correlation coefficient $a$ between the momenta of the electron and the electron-antineutrino in free neutron decay. The coefficient $a$ is inferred from a detailed analysis of the integral proton recoil spectrum measured with the $a$SPECT setup, a MAC-E-Filter type spectrometer with $4\ensuremath{\pi}$ acceptance. The result can be used to determine the axial-vector coupling constant ${g}_{A}$ in the weak interaction and shows a tantalizing disagreement with recent measurements of ${g}_{A}$ via the $\ensuremath{\beta}$-decay asymmetry in neutron decay.

РАСЧЕТНО-ЭКСПЕРИМЕНТАЛЬНАЯ ОЦЕНКА СЕЧЕНИЙ РЕАКЦИЙ 16O(p, α)13N И 12C(p, γ)13N,13C(p, n)13N, УСРЕДНЕННЫХ ПО СПЕКТРУ ПРОТОНОВ ОТДАЧИ ПРИ УПРУГОМ (N, P)-РАССЕЯНИИ 14 МЭВ НЕЙТРОНОВ В ВОДОРОДОСОДЕРЖАЩИХ СРЕДАХ

The paper describes the calculation-and-experimental method used to measure σO, σC cross-sections of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions when these cross-sections were averaged over the spectrum of recoil protons in hydrogen-containing media. Measurements were performed with the help of the ∼14 MeV neutron source. As a result, cross-sections were determined to be σO=17,2 Mbarn, σC =2,59 Mbarn and this fairly well agrees with the sufficiently limited data available on the energy dependence of cross-sections from the above reactions in the proton energy region E≤10 MeV. Cross-sections of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions in the region of small and medium proton energies E≤10 MeV are of interest for the fundamental science when studying the CNO - cycle of hydrogen burning in rather large stars and also for applied sciences when it is necessary to solve certain problems like (i) considering "false" nitrogen formation when protein content is determined in grain crops using the neutron activation analysis and the 14 MeV neutron source; (ii) studying applicability of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions to produce the shortlived β+-radioactive isotope 13N directly in water and alcohol solutions of preparations for positronemission tomography (PET) with high-energy sources of (D,T)-neutrons; and (iii) studying applicability of 16O(p, α)13N and 12C(p, γ)13N, 13C(p, n)13N reactions with the formation of the β+-radioactive isotope 13N to determine actual distribution of absorbed doses in the patient body or in the phantom thereof based on the annihilation radiation after a session of neutron therapy with the 14 MeV neutron source or after a proton therapy session.

Flux measurement of fast neutrons in the Gran Sasso underground laboratory

Neutron energy spectrum for energies extending up to 15 MeV has been measured in the Hall A of INFN Laboratori Nazionali del Gran Sasso in Italy, by using a mathrm {1.5~m^3} stainless-steel tank filled with 1.2 ton Gd-doped liquid scintillator. A two-pulse signature, due to proton recoils and delayed gammas from neutron capture on Gd, has been used for event selection. The neutron energy spectrum has been obtained from the detected proton-recoil spectrum, after unfolding the detector response, which had been simulated with GEANT4. Although this spectrum has been measured previously, the present work represents an improvement in the energy resolution with respect to previously published results. The results obtained with this technique are compared with other measurements existing in literature.

A Design and its Validation of a Proton Recoil Telescope with a Silicon Detector for Measurements of Fast Neutrons

A silicon detector combined with a thin polyethylene converter and a collimator is designed as a simple proton recoil telescope (PRT) detector for detecting 2.45 MeV neutrons from a D-D neutron generator. Monte Carlo simulations are performed for a quantitative optimization of the geometrical parameters of the detector that determine the statistics and the spectrum of recoil protons. On the basis of the optimized geometry, a 15 μm polyethylene converter and a 2.5 mm thick stainless steel collimator are chosen for the design of a PRT. A test experiment is done by using 2.45 MeV neutrons from a D-D generator at the Korea Research Institute of Standards and Science. Energy calibration of the silicon detector is done by using proton beams from the MC-50 cyclotron at the Korea Institute of Radiological & Medical Sciences. A peak corresponding to 2.45 MeV neutrons is observed. Neutron detection efficiency of our PRT detector for 2.45 MeV neutrons is found to be about 3 × 10 −6.

Design and performance of a hybrid fast and thermal neutron detector

We report the characterization, calibration and performance of a custom-built hybrid detector consisting of BC501A liquid scintillator and BC702 scintillator for the detection of fast and thermal neutrons, respectively. Pulse Shape Discrimination techniques are developed to distinguish events due to γ-rays, fast and thermal neutrons. Software analysis packages are developed to derive raw neutron energy spectra from measured proton recoil spectra. The validity is demonstrated through the reconstruction of the 241AmBe(α,n) neutron spectrum.

Study of an unfolding algorithm for D-T neutron energy spectra measurement using a recoil proton method**Supported by National Natural Science Foundations of China (11375077, 21327801) and National Key Scientific Instrument And Equipment Development Project (2013YQ40861)

A proton recoil method for measuring D-T neutron energy spectra using polyethylene film and a Si(Au) surface barrier detector is presented. An iteration algorithm for unfolding the recoil proton energy spectrum to the neutron energy spectrum is investigated. The response matrices R of the polyethylene film at angles of 0° and 45° were obtained by simulating the recoil proton energy spectra from mono-energetic neutrons using the MCNPX code. With an assumed D-T neutron spectrum, the recoil proton spectra from the polyethylene film at angles of 0° and 45° were also simulated using the MCNPX code. Based on the response matrices R and the simulated recoil proton spectra at 0° and 45°, the respective unfolded neutron spectra were obtained using the iteration algorithm, and compared with the assumed neutron spectrum. The results show that the iteration algorithm method can be applied to unfold the recoil proton energy spectrum to the neutron energy spectrum for D-T neutron energy spectra measurement using the recoil proton method.

Neutron and Gamma Spectrometry in the Research Reactor LR-0

The complex measurement system for the full-scale VVER models (mock-ups), created in the research reactor LR-0, is discussed. Fast neutron (energy from 0.5 to 10 MeV) and gamma spectra are measured in several representative points of the mock-ups by the two-parameter spectrometer with the cylindrical stilbene scintillation detectors. Measurements in the thermal and epithermal neutron region are carried out with the activation method using a broad set of activation monitors and with the $^3{\rm He}({\rm n},{\rm p})$ counter. Activation measurements with threshold fast neutron detectors enlarge also the proton-recoil spectra measurements, such activation measurements are carried out especially in cases, when a spectrometer cannot be put in the necessary position. The core fission rate distribution is obtained by means of gamma-scanning of the fuel pins. The low noise precise power (flux density) monitoring system, independent of the operation control system, was developed in the LR-0 reactor for mock-up experiments.

Re-evaluation of the EURACOS integral shielding experiment series

The EURACOS experiment series (sodium, iron, and no shielding) has been re-evaluated in the scope of the OECD/NEA SINBAD project to determine how useful these benchmarks can be for the validation of the modern nuclear data evaluations. The measured activation rates of different foils as well as unfolded proton recoil spectra at different depths in sodium and iron have been compared to the Monte Carlo calculated parameters. The results suggest good agreement with the experiment only for the high-threshold 32S(n,p) reaction detectors. The comparison of the lower threshold 103Rh(n,n′) and 115In(n,n′) reactions, and the (n,γ) reaction on 197Au under cadmium cover, reveals large discrepancy between the experimental and calculated spatial distributions for these reaction rates which is expected to be due to the uncertainties in the source and background description rather than due to the cross section uncertainties. On the other hand, the unfolded neutron spectra shapes are in relatively good agreement with the calculated ones. The overall results show that the EURACOS Na and Fe experiments cannot be considered of benchmark quality mainly due to unsatisfactory information on the neutron source. Nevertheless, some activation measurements from the EURACOS sodium and iron experiments such as the high threshold reactions and the spectra measurements are potentially useful for modern nuclear data and computer code benchmarking.

Unfolding the fast neutron spectra of a BC501A liquid scintillation detector using GRAVEL method

Accurate knowledge of the neutron energy spectra is useful in basic research and applications. The overall procedure of measuring and unfolding the fast neutron energy spectra with BC501A liquid scintillation detector is described. The recoil proton spectrum of Am-Be neutrons was obtained experimentally. With the NRESP7 code, the response matrix of detector was simulated. Combining the recoil proton spectrum and response matrix, the unfolding of neutron spectra was performed by GRAVEL iterative algorithm. A MatLab program based on the GRAVEL method was developed. The continuous neutron spectrum of Am-Be source and monoenergetic neutron spectrum of D-T source have been unfolded successfully and are in good agreement with their standard reference spectra. The unfolded Am-Be spectrum are more accurate than the spectra unfolded by artificial neural networks in recent years.

Development of large-area composite stilbene scintillator for fast neutron detection

Fast neutron applications have gained popularity with the growth of fast neutron production facilities. Covering a larger area and/or wider angle can be one of the advantages of a fast neutron detector. In the present study, a large-area composite stilbene scintillator with the dimensions of 200 mm (D) × 20 mm (H) was fabricated to examine its scintillation properties and to evaluate its applicability to fast neutron detection. The detector response of small- and large-area composite stilbene scintillators for neutrons and gamma rays was measured and compared with that of commercial and small single-crystal stilbene scintillators. To this end, the response of each scintillator was measured for radioisotopes as well as mono-energetic neutrons generated by a Tandem accelerator. The neutron–gamma separation performance of the large-area composite stilbene scintillator was evaluated in terms of figure-of-merit (FoM) using the digital pulse shape discrimination method. The composite stilbene scintillator showed good energy linearity, as determined from its recoil proton spectra, with reasonable n–γ separation capability. The results indicated that the composite stilbene scintillator could be applied to the field of fast neutron detection, especially when a large area and/or a wide angle is to be covered and could be a good alternative to liquid scintillators.

Measurement of the proton light response of various LAB based scintillators and its implication for supernova neutrino detection via neutrino–proton scattering

The proton light output function in electron-equivalent energy of various scintillators based on linear alkylbenzene (LAB) has been measured in the energy range from 1 MeV to 17.15 MeV for the first time. The measurement was performed at the Physikalisch-Technische Bundesanstalt (PTB) using a neutron beam with continuous energy distribution. The proton light output data is extracted from proton recoil spectra originating from neutron-proton scattering in the scintillator. The functional behavior of the proton light output is described succesfully by Birks' law with a Birks constant kB between (0.0094 +/- 0.0002) cm/MeV and (0.0098 +/- 0.0003) cm/MeV for the different LAB solutions. The constant C, parameterizing the quadratic term in the generalized Birks law, is consistent with zero for all investigated scintillators with an upper limit (95% CL) of about 10^{-7} cm^2/MeV^2. The resulting quenching factors are especially important for future planned supernova neutrino detection based on the elastic scattering of neutrinos on protons. The impact of proton quenching on the supernova event yield from neutrino-proton scattering is discussed.

Proton recoil spectra in spherical proportional counters calculated with finite element and Monte Carlo methods

Proton recoil spectra were calculated for various spherical proportional counters using Monte Carlo simulation combined with the finite element method. Electric field lines and strength were calculated by defining an appropriate mesh and solving the Laplace equation with the associated boundary conditions, taking into account the geometry of every counter. Thus, different regions were defined in the counter with various coefficients for the energy deposition in the Monte Carlo transport code MCNPX. Results from the calculations are in good agreement with measurements for three different gas pressures at various neutron energies.

Comment on “Nuclear Emissions During Self-Nucleated Acoustic Cavitation”

In a recent Letter to PRL, Taleyarkhan and coauthors claim to observe DD fusion produced by acoustic cavitation. Among other evidence, they provide a proton recoil spectrum that they interpret as arising from 2.45 MeV DD fusion neutrons. My analysis concludes the spectrum is inconsistent with 2.45 MeV neutrons, cosmic background, or a PuBe source, but it is consistent with a Cf-252 source.

Determination of the Electron-Antineutrino Angular Correlation Coefficient a0 in Unpolarized Neutron β-Decay.

The coefficient a0 has been derived from a measurement of the integral spectrum of recoil protons stored in a quasi-Penning trap with inhomogeneous magnetic field and adiabatic focusing onto an electro-static mirror of potential variable in 10 V steps between 0 V and 850 V. Correction for incomplete transfer of energy from transverse to longitudinal degrees of freedom, and the violation of the adiabatic conditions on reflection at the mirror, is carried out by alternately measuring the spectrum at trapping times of 1 ms and 2 ms. The results a0 = −0.1054 ± 0.0055 and |λ | = 1.271 ± 0.018 are comparable in precision with existing measurements of a0.

Study of resonance states in 12N using a radioactive ion beam of 11C

Resonance states in 12N were studied by using the resonance elastic scattering of 11C+p with a low-energy radioactive ion beam of 11C at 3.5 MeV/nucleon and a thick (CH2)n target. The 11C beam was separated by a newly installed CNS radioactive ion beam separator (CRIB). The energy spectrum of recoil protons was measured at laboratory scattering angles around θLAB=0° to identify resonance states in 12N. The spin-parity values of Jπ=3− and (2)+ have been determined for the levels at the excitation energies of Ex=3.1 and 3.6 MeV in 12N, respectively, suggesting a small contribution of the 3.1-MeV level to the 11C(p,γ)12N stellar reaction.