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MCNP6 is simply and accurately described as the merger of MCNP5 and MCNPX capabilities, but it is much more than the sum of those two computer codes. MCNP6 is the result of five years of effort by ...

The results of experimental measurement and numerical simulation of 979 rates of threshold reactions in 142 samples of 209Bi, 197Au, 181Ta, 169Tm, 115In, 93Nb, 65Cu, 64Zn, 63Cu, 59Co, 27Al, 19F, and 12C placed inside and outside of a “thick” W-Na target irradiated with 0.8-GeV protons are reported. The reaction rates are measured by the method of γ spectrometry using Ge and GeLi semiconductor detectors. The numerical calculations were performed using the LAHET code package together with the EXFOR database and the evaluated data libraries MENDL2N, MENDL2P, and IEAF2001. The experimental and calculated results are compared and the most significant discrepancies are analyzed.

The independent and cumulative measured yields of residual products in thin lead and bismuth targets irradiated with 0.04-2.6 GeV protons are compared with results by the LAHET, CEM03, LAQGSM03, INCL+ABLA, CASCADE and YIELDX codes, in order to evaluate the predictive power of the codes in this energy region. We found that the predictive power of the tested codes is different but is satisfactory for most of the nuclides in the spallation region, though none of the codes agree well with the data in the whole-mass region of product nuclides and all should be improved further. On the whole, the predictive power of all codes for the data in the fission and fragmentation product regions and, especially, at the borders between spallation and fission and between fission and fragmentation regions is much worse than in the spallation region; therefore, development of better evaporation/fission/fragmentation models is of first priority.

The developmental version of MCNP5 has recently been extended to provide for continuous-energy transport of high-energy protons. This enhancement involves the incorporation of several significant new physics models into the code. Multiple Coulomb scattering is treated with an advanced model that takes account of projectile and nuclear target form factors. In the next version, this model will provide a coupled sampling of both angular deflection and collisional energy loss, including straggling. The proton elastic scattering model is also new, based on recent theoretical work. Charged particle transport in the presence of magnetic fields is accomplished either by using transfer maps from the COSY INFINITY code (in void regions) or by using an algorithm adapted from the MARS code (in void regions or in scattering materials). Work is underway to validate and implement the latest versions of the Cascade-Exciton Model and the Los Alamos Quark-Gluon String Model, which will process inelastic nuclear interactions and generate secondary particles.

A modified version of MCNP5 has been developed to treat continuous-energy proton transport. This work is summarised in companion papers by Hughes et al. and Bull et al. (in these proceedings). An intrinsic part of this development effort has involved testing, verification and validation of a capability for simulating proton radiographs. This paper presents the results of calculations simulating various different test objects and the effects of alternative physics models. The significant physics processes include elastic scattering, multiple coulomb scattering, collisional energy-loss and straggling, magnetic fields and attenuation owing to nuclear interactions. Comparisons with experimental data are presented.

Experimental results obtained by determining the double-differential cross sections for neutron production in Pb, W, Zr, Cu, and Al targets irradiated with 0.8-, 1.0-, and 1.6-GeV protons are presented. The spectra of neutrons were measured at 15°, 30°, 60°, 90°, 120°, and 150° with a time-of-flight spectrometer by using a proton beam extracted from the 10-GeV synchrotron at the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The neutrons are recorded with 5MAB-1F6BC501A/5L liquid scintillation detectors and NE110 solid-state scintillators. The experimental data in question are compared with the results of simulations based on the CEM97, LAHET, and CASCADE codes.

The Monte Carlo transport workhorse, MCNP [Los Alamos National Laboratory report LA-13709-M, 2000], is undergoing a massive renovation at Los Alamos National Laboratory (LANL) in support of the Eolus Project of the Advanced Simulation and Computing (ASCI) Program. MCNP 1 Version 5 (V5) (expected to be released to RSICC in Fall 2002) will consist of a major restructuring from FORTRAN-77 (with extensions) to ANSI-standard FORTRAN-90 [American National Standard for Programming Language – Fortran-Extended, ANSI X3. 198-1992, 1992] with support for all of the features available in the present release (MCNP-4C2/4C3). To most users, the look-and-feel of MCNP will not change much except for the improvements (improved graphics, easier installation, better online documentation). For example, even with the major format change, full support for incremental patching will still be provided. In addition to the language and style updates, MCNP V5 will have various new user features. These include improved photon physics, neutral particle radiography, enhancements and additions to variance reduction methods, new source options, improved parallelism support (PVM, MPI, OpenMP), and new nuclear and atomic data libraries.

The CEM2k and LAQGSM codes have been recently developed at Los Alamos National Laboratory to simulate nuclear reactions for a number of applications. We have benchmarked our codes against most available measured data at incident particle energies from 10 MeV to 800 GeV and have compared our results with predictions of other current models used by the nuclear community. Here, we present a brief description of our codes and show illustrative results to show that CEM2k and LAQGSM can be used as reliable event generators for space-radiation-shielding, cosmic-ray-propagation, and other astrophysical applications. Finally, we show the use of our calculated cross sections together with experimental data from our LANL T-16 compilation to produce evaluated files which we use in the GALPROP model of galactic particle propagation to better constrain the size of the CR halo., 10 pages, 9 figures, LaTeX, talk given at the World Space Congress 2002, 34th COSPAR Scientific Assembly, Houston, Texas, USA, 10-19 October 2002, to appear in Advances in Space Research

A qualitative and quantitative comparison of the recent GSI measurements of the nuclide yields from 208 Pb and 238U at 1 GeV/nucleon and 197Au at 800 MeV/nucleon interactions with protons with the codes LAHET (with both ISABEL and Bertini options), CEM95, CEM97, CEM2k, CASCADE, CASCADE/INPE, YIELDX, HETC, and INUCL is presented The predictive power of these codes is reasonable for nuclides in the near spallation region but is worse for deep spallation and much worse in the fission region. None of these codes agree well with the data in the whole mass region of product nuclides and all must be improved to become reliable tools for accelerator-driven applications.

The work is aimed at experimental determining and computer simulating the independent and cumulative yields of residual product nuclei in the target and structure materials of the transmutation facilities driven by high-current accelerators. The ITEP U-10 accelerator was used in 48 experiments to obtain more than 4000 values of the yields of radioactive residual product nuclei in 0.1-2.6 GeV proton-irradiated thin 182, 183, 184, 186W, natW, 56Fe, 58Ni, 93Nb, 232Th, 232Th, natU, 99Tc, 59Co, 63, 65Cu, natHg, 208Pb, and 27Al targets. The results of verifying the LAHET, CEM95, CEM2k, CASCADE, CASCADE/INPE, YIELDX, HETC, INUCL, and other simulation codes are presented.

Early space radiation shield code development relied on Monte Carlo methods and made important contributions to the space program. Monte Carlo methods have resorted to restricted one-dimensional problems leading to imperfect representation of appropriate boundary conditions. Even so, intensive computational requirements resulted and shield evaluation was made near the end of the design process. Resolving shielding issues usually had a negative impact on the design. Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from the preliminary concept to the final design. For the last few decades, we have pursued deterministic solutions of the Boltzmann equation allowing field mapping within the International Space Station (ISS) in tens of minutes using standard Finite Element Method (FEM) geometry common to engineering design methods. A single ray trace in such geometry requires 14 milliseconds and limits application of Monte Carlo methods to such engineering models. A potential means of improving the Monte Carlo efficiency in coupling to spacecraft geometry is given.

Several new capabilities have been added to MCNP4C including: (1) macrobody surfaces; (2) the superimposed mesh importance functions, so that it is no longer necessary to subdivide geometries for variance reduction; and (3) Xlib graphics and DVF Fortran 90 for PCs. There are also improvements in neutron physics, electron physics, perturbations, and parallelization. In the more distant future we are working on adaptive Monte Carlo code modernization, more parallelization, visualization, and charged particles.

The results of experimental and computer simulation studies of the yields of residual product nuclei in Bi-209 thin targets irradiated by 130 MeV and 1.5 GeV protons are presented. The yields were measured by direct high-precision gamma-spectrometry. The gamma-spectrometer resolution was 1.8 keV in the 1332 keV line. The gamma-spectra were processed by the ASPRO code. The gamma-lines were identified, and the cross sections defined, by the SIGMA code using the GDISP radioactive database. The process was monitored by the Al-27(p,x)Na-24 reaction. Results are presented for comparisons between the 209-Bi(p,x) reaction yields obtained experimentally and simulated by the HETC, GNASH, LAHET, INUCL, CEM95, CASCADE, and ALICE codes.

MCNP6 is simply and accurately described as the merger of MCNP5 and MCNPX capabilities, but it is much more than the sum of these two computer codes. MCNP6 is the result of six years of effort by the MCNP5 and MCNPX code development teams. These groups of people, residing in Los Alamos National Laboratory’s X Computational Physics Division, Monte Carlo Codes Group (XCP-3) and Nuclear Engineering and Nonproliferation Division, Radiation Transport Modeling Team (NEN-5) respectively, have combined their code development efforts to produce the next evolution of MCNP. While maintenance and major bug fixes will continue for MCNP5 1.60 and MCNPX 2.7.0 for upcoming years, new code development capabilities only will be developed and released in MCNP6. In fact, the initial release of MCNP6 contains numerous new features not previously found in either code. These new features are summarized in this document. Packaged with MCNP6 is also the new production release of the ENDF/B-VII.1 nuclear data files usable by MCNP. The high quality of the overall merged code, usefulness of these new features, along with the desire in the user community to start using the merged code, have led us to make the first MCNP6 production release: MCNP6 version 1. High confidence in the MCNP6 code is based on its performance with the verification and validation test suites, comparisons to its predecessor codes, our automated nightly software debugger tests, the underlying high quality nuclear and atomic databases, and significant testing by many beta testers.

Shielding related calculations were performed for 230-MeV protons incident upon a stopping-length iron target using the LAHET code system (LCS). Secondary neutrons and photons, produced by proton interactions with the target nuclei, were transported through a spherical concrete shield in which absorbed dose and dose equivalent tallies were produced and attenuation parameters deduced. Comparing calculated results with measurements performed with a similar target, beam, and shielding geometry, the dose equivalent production term is double the measured value. The LCS overestimates measured attenuation values at 0, 22, and 45 deg while correctly predicting the attenuation length at 90 deg. Comparison of LCS results with HETC calculations and analytical methods indicates that LCS better estimates the attenuation length and dose equivalent production.

MCNP6 has been Validated and Verified (V&V) against intermediate- and high-energy fission cross-section experimental data. An error in the calculation of fission cross sections of 181Ta and a few nearby target nuclei by the CEM03.03 event generator in MCNP6 and a "bug: in the calculation of fission cross sections with the GENXS option of MCNP6 while using the LAQGSM03.03 event generator were detected during our V&V work. After fixing both problems, we find that MCNP6 using CEM03.03 and LAQGSM03.03 calculates fission cross sections in good agreement with available experimental data for reactions induced by nucleons, pions, and photons on both subactinide and actinide nuclei at incident energies from several tens of MeV to about 1 TeV., 3 pages, 3 figures, Proc. 2013 International Conference on Nuclear Data for Science & Technology (ND2013), March 4-8, 2013, New York, USA, to be published in Nuclear Data Sheets

For the past several years, a major effort has been undertaken at Los Alamos National Laboratory (LANL) to develop the transport code MCNP6, the latest LANL Monte-Carlo transport code representing a merger and improvement of MCNP5 and MCNPX. We emphasize a description of the latest developments of MCNP6 at higher energies to improve its reliability in calculating rare-isotope production, high-energy cumulative particle production, and a gamut of reactions important for space-radiation shielding, cosmic-ray propagation, and accelerator applications. We present several examples of validation and verification of MCNP6 compared to a wide variety of intermediate- and high-energy experimental data on reactions induced by photons, mesons, nucleons, and nuclei at energies from tens of MeV to about 1 TeV/nucleon, and compare to results from other modern simulation tools., Comment: 4 pages, 3 figures, Proc. 11th Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2012), St. Petersburg, FL, May 28 - June 3, 2012

The Monte Carlo code MCNP has three different, but correlated, estimators for calculating keff in nuclear criticality calculations: collision, absorption, and track length estimators. The combinati...

This paper reports on approximate method that is developed to allow S({alpha},{beta}) thermal collision contributions to next-event estimators in Monte Carlo calculations. The new technique is applicable to the more general problem of contributions to next-event estimators from any discrete probability distribution. The method is incorporated into the MCNP Monte Carlo radiation transport code.

This work presents results of computer simulation of two experiments which aim at measuring the threshold activation reaction rates in 1 2 C, 1 9 F, 2 7 Al, 5 9 Co, 6 3 Cu, 6 5 Cu, 6 4 Zn, 9 3 Nb, 1 1 5 In, 1 6 9 Tm, 1 8 1 Ta, 1 9 7 Au, and thin samples placed inside and outside a 0.8 GeV proton-irradiated 4-cm thick W target and a 92-cm-thick W-Na composite target of 15 cm diameter both. In total, more than 1000 values of activation reaction were determined in both the experiments. The measured reaction rates were compared with the rates simulated by the LAHET code with the use of several nuclear databases for the respective excitation functions, namely, MENDL2 together with MENDL2P for cross sections of protons and neutrons up to 100 MeV, and with the recently developed IEAF-2001 that provides neutron cross sections up to 150 MeV. A comparison of simulation-to-experiment agreement obtained with MENDL2 and IEAF-2001 is presented. The agreement between simulation and experiment has been found general satisfactory for both databases. However, further studies should be done to improve the simulation of production of secondary protons and high-energy neutrons, as well as the high-energy neutron elastic scattering. Our results allow to conclude about the reliability of the transport codes and databases used to simulate the accelerator driven systems (ADS), particularly with Na-cooled W targets. High-energy threshold excitation functions to be used in the activation-based unfolding of neutron spectra inside the ADS can also be inferred from these results.

Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from the preliminary design concepts to the final design. In particular, we will discuss the progress towards a full three-dimensional and computationally efficient deterministic code for which the current HZETRN evaluates the lowest-order asymptotic term. HZETRN is the first deterministic solution to the Boltzmann equation allowing field mapping within the International Space Station (ISS) in tens of minutes using standard finite element method (FEM) geometry common to engineering design practice enabling development of integrated multidisciplinary design optimization methods. A single ray trace in ISS FEM geometry requires 14 ms and severely limits application of Monte Carlo methods to such engineering models. A potential means of improving the Monte Carlo efficiency in coupling to spacecraft geometry is given in terms of re-configurable computing and could be utilized in the final design as verification of the deterministic method optimized design. Published by Elsevier Ltd on behalf of COSPAR.

The work presents results of computer simulation of two experiments whose aim was measuring the threshold activation reaction rates in 12C, 19F, 27Al, 59Co, 63Cu, 65Cu, 64Zn, 93Nb, 115In, 169Tm, 181Ta, 197Au, and 209Bi thin samples placed inside and outside a 0.8‐GeV proton‐irradiated 4‐cm thick W target and a 92‐cm thick W‐Na composite target of 15‐cm diameter both. In total, more than 1000 values of activation reaction were determined in both experiments. The measured reaction rates were compared with the rates simulated by the LAHET code with the use of two nuclear databases for the respective excitation functions, namely, MENDL2/2P for neutron/proton cross sections up to 100 MeV, and the recently developed IEAF‐2001 that provides neutron cross sections up to 150MeV. Here, we present a comparison of the simulation‐to‐experiment agreement obtained using MENDL2 and IEAF‐2001. The agreement between simulation and experiment has been found general satisfactory for both of the databases. High‐energy thresho...

More than 5500 independent and cumulative yields of radioactive residual product nuclides with lifetimes ranging from 13.2 min (187Re) to 31.55 years (207Bi) are measured in 208, 207, 206, natPb and 209Bi thin targets irradiated by 0.04, 0.07, 0.10, 0.15, 0.25, 0.40, 0.60, 0.80, 1.20, 1.60, and 2.60 GeV external proton beams from the ITEP U10 accelerator. The measured yields are compared with results by the LAHET (Bertini and ISABEL options), CEM03, LAQGSM03, INCL4+ABLA, CASCADE, CASCADE‐2004, CASCADO, and the LAHETO codes, in order to evaluate their predictive powers in this energy region. We found that the predictive power of the tested codes is different but is satisfactory for most of the nuclides in the spallation region, though none of the codes agree well with the data in the whole mass region of product nuclides and all should be improved further. On the whole, the predictive power of all codes for the data in the fission and fragmentation product regions and, especially, at the borders between sp...

Isotopically enriched 129I (85% 129I and 15% 127I) targets were irradiated with a beam of 660‐MeV protons at the JINR DLNP Phasotron and cross sections of formation of 74 residual products were determined using the γ‐spectrometry method. Here, we analyze all these data using eleven different models, realized in eight codes: LAHET (Bertini, ISABEL, INCL+ABLA, and INCL+RAL options), CASCADE, CEM95, CEM2k, LAQGSM+GEM2, CEM2k+GEM2, LAQGSM+GEMINI, and CEM2k+GEMINI, in order to validate the tested models against the experimental data and to understand better the mechanisms for production of residual nuclei. We find that most of the codes are fairly reliable in predicting cross sections for nuclides not too far away in mass from the targets, but differ greatly in the deep spallation, fission, and fragmentation regions. None of the codes tested here except GEMINI allow fission of nuclei as light as iodine, therefore the best agreement with the 129I data, especially in the A=40–90 region, is shown by the codes CEM2k and LAQGSM when they are merged with GEMINI. We conclude that none of the codes tested here are able to reproduce well all these data and all of them need to be further improved; development of a better universal evaporation/fission model should be of a high priority.

Double-differential cross sections of neutron production at angles from 0 to 110 degrees from many reactions induced by light and medium nuclei on targets from 12-C to 208-Pb, at several incident energies from 95 to 600 MeV/A have been measured recently at the Institute of Physical and Chemical Research (RIKEN) Ring Cyclotron in Japan and at the Heavy-Ion Medical Accelerator of the National Institute of Radiological Science in Chiba, Japan using the time-of-flight technique. We have analyzed all these new measurements using the Quantum Molecular Dynamics (QMD) model, the Oak Ridge intranuclear cascade model HIC, the ISABEL intranuclear cascade model from LAHET, and the Los Alamos version of the Quark-Gluon String Model code LAQGSM03. On the whole, all four models used here describe reasonably well most of the measured neutron spectra, although different models agree differently with data from specific reactions and some serious discrepances are observed for some reactions. We present here some illustrative results from our study, discuss possible reasons for some of the observed discrepancies and try to outline ways to further improve the tested codes in order to address these problems., Comment: 5 pages, pdf, 3 figures, to be published in Proc. Int. Conf. on Nuclear Data for Sciience & Technology (ND2004), Santa Fe, USA, Sept. 26 - Oct. 1, 2004

114 cross sections for nuclide production in a 1.0 GeV proton-irradiated thin 208Pb target have been measured by the direct gamma spectrometry method using a high-resolution Ge detector. The gamma spectra were processed by the GENIE-2000 code. The ITEP-developed SIGMA code was used together with the PCNUDAT nuclear decay database to identify the gamma lines and to determine the cross sections. The 27Al(p,x)22Na reaction was used to monitor the proton flux. Results of a feasibility study of the auxiliary 27Al(p,x)24Na and 27Al(p,x)7Be monitor reactions in the 0.07-2.6 GeV proton-energy range are presented as well. Most of the experimental data have been analyzed by the LAHET (with ISABEL and Bertini options), CEM95, CEM2k, INUCL, CASCADE, CASCADE/INPE, and YIELDX codes that simulate hadron-nucleus interactions.

Considering the prospects of using the W-Na target assemblies in ADS facilities, the experiments were made to study the nuclear-physics characteristics of W and Na, and the composite structures thereof in their interactions with 0.8-GeV and 1.6-GeV protons. The neutron and proton-induced reaction rates were measured inside, and on the surface of, a cylinder-shaped heterogeneous W-Na assembly together with the double-differential spectra of secondary neutrons emitted from different-depth W and Na discs. The measurement results were simulated by the LAHET, CEM2k, and KASKAD-S codes in terms of the latest versions of nuclear databases., Comment: Proc. Int. Conf. on Nuclear Data for Science and Technology (ND2001), October 7-12, 2001, Tsukuba, Ibaraki, Japan, 4 pages, 5 figures, only pdf file

Much to the disappointment of many, our distinguished speaker for the initial plenary session has been unable to attend our conference. I was prevailed upon by the conference organization to present a talk which, as prescribed, will be of a historical nature, but as the title describes, will also be a very personal view. Perhaps the opinions expressed will find sympathy with my associates around the world who have devoted their efforts to and found some satisfaction with providing the code tools for radiation transport to a large, and occasional anxious, community of users.

The Monte Carlo particle transport code MCNPX and its associated data have been the focus of a major development effort at Los Alamos for several years. The system has reached a mature state, and has become a significant tool for many intermediate and high-energy particle transport applications. A recent version has been released to the Radiation Safety Information Computational Center (RSICC). A recent report provides an overview of the code and an extensive set of references for the component physics modules used in the code. In this paper we review the status of the developmental version of MCNPX, and describe some important new enhancements, including the use of evaluated nuclear data files for proton transport; the use of photonuclear reaction data; improved elastic and inelastic react ion cross sections for nucleons, antinucleons, pions, and kaons; and two new modes of operation of the code. We also illustrate the use of the new proton and photonuclear data in two representative applications.

The Los Alamos National Laboratory Monte Carlo N-Particle radiation transport code, MCNP, has become an international standard for a wide spectrum of neutron-gamma radiation transport applications. These include nuclear criticality safety, radiation shielding, nuclear safeguards, nuclear oil-well logging, fission and fusion reactor design, accelerator target design, detector design and analysis, health physics, medical radiation therapy and imaging, radiography, decontamination and decommissioning, and waste storage and disposal. The latest version of the code, MCNP4C [1], was released to the Radiation Safety Information Computational Center (RSICC) in February 2000. This paper describes the new features and capabilities of the code, and discusses the specific applicability to neutron-gamma problems. We will also discuss some of the future directions for MCNP code development.

This document is intended to provide additional information supplementing a prior publication. The discussion describes the details of the implementation of the proton nonelastic cross section parameterization for LAHET usage. It also documents extensions of the method to stable nuclei with 2 {le} Z {le} 5.

MCNP has three different, but correlated, estimators for Calculating k{sub eff} in nuclear criticality calculations: collision, absorption, and track length estimators. The combination of these three estimators, the three-combined k{sub eff} estimator, is shown to be the best k{sub eff} estimator available in MCNP for estimating k{sub eff} confidence intervals. Theoretically, the Gauss-Markov Theorem provides a solid foundation for MCNP`s three-combined estimator. Analytically, a statistical study, where the estimates are drawn using a known covariance matrix, shows that the three-combined estimator is superior to the individual estimator with the smallest variance. The importance of MCNP`s batch statistics is demonstrated by an investigation of the effects of individual estimator variance bias on the combination of estimators, both heuristically with the analytical study and emprically with MCNP.

A spallation target constructed of thorium metal has been designed for applications using molten‐salt as the target coolant. The design consists of an array of wire‐wrapped, hastelloy‐clad, thorium rods in which a parabolic void region is introduced in the upper regions. Each target rod is approximately 1 m in length, 3.1 cm in diameter, and has a clad thickness of 0.05 cm; 140 rods are arranged in a triangular lattice with a pitch of 3.2 cm, which results in a cylindrical target configuration with a radius of 20 cm and an estimated yield of 17 neutrons/proton for 800 MeV protons.

Neutron cross sections on carbon at and above 14 MeV are of interest for a variety of applications. It is argued that the ENDF/B-V evaluation of the nonelastic cross sections is in some error; this is due in part to the ''subtraction'' technique used for evaluating the nonelastic cross section, and to an overreliance on old nuclear emulsion data. In addition, secondary uncharged- (and, for biomedical applications, charged-) particle spectra are important. It is shown that kerma-factor calculations are very sensitive to the secondary charged-particle spectrum. Thus an assessment of the reaction mechanisms, leading to evaluated secondary particle spectra, is also needed.

The results of an experiment to measure the 12C(n,n′)3α reaction in nuclear emulsions up to 35 MeV were reanalyzed, with various corrections made using a previously validated nuclear reaction model...

Double differential cross sections for the neutron-induced production of p, d, t, $^{3}\mathrm{He}$, and alpha particles from carbon have been measured using unpolarized neutrons. Neutron beam energies of 27.4, 39.7, and 60.7 MeV were used. The charged particle energy spectra at nine laboratory angles---15, 20, 35, 40, 45, 65, 90, 130, and 150 deg---range up to the kinematic maximum, from a lower energy cutoff of 4 MeV for p, d, t, and alpha and 8 MeV for $^{3}\mathrm{He}$. A CH target was used so that the absolute normalization was obtained simultaneously from the n-p cross sections. Intranuclear cascade plus deexcitation calculations were carried out. The data are compared with these calculations and with available proton induced (charge symmetric) reaction spectra.NUCLEAR REACTIONS $^{12}\mathrm{C}(\mathrm{n}, \mathrm{p}x; \mathrm{d}x; ^{3}\mathrm{H}x; ^{3}\mathrm{He}x; ^{4}\mathrm{He}x)$, ${E}_{\mathrm{n}}=27.4, 39.7, 60.7$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta}; E)$, ${\ensuremath{\theta}}_{\mathrm{lab}}=15, 20, 35, 40, 45, 65, 90, 130, 150$ deg. Intranuclear cascade plus deexcitation calculations.

Double-differential cross sections for the neutron-induced production of p, d, t, $^{3}\mathrm{He}$, and alpha particles from oxygen and nitrogen have been measured using an unpolarized neutron facility. Neutron beam energies of 27.4, 39.7, and 60.7 MeV were used. The charged particle energy spectra, at six forward laboratory angles, 15, 20, 35, 40, 45, and 65, and, where feasible, at three backward angles, 90, 130, and 150 deg, range up to the kinematic maximum, from a typical low-energy cutoff of 4 MeV for p, d, t, and alpha particles, and 8 MeV for $^{3}\mathrm{He}$. Intranuclear cascade plus deexcitation calculations were carried out. The data are compared with these calculations and with available proton-induced (charge-symmetric) reaction spectra for oxygen.