Double-differential cross sections and kerma coefficients for light-charged particles produced by 96 MeV neutrons on carbon

Double-differential cross sections of inclusive light-ion (p, d, t, ³He and α) production in carbon induced by 96 MeV neutrons have been measured at eight laboratory angles from 20° to 160° in steps of 20°. Experimental techniques, as well as procedures for data taking and data reduction, are presented. Deduced energy-differential and production cross sections are herewith reported. Experimental cross sections are compared with theoretical reaction model calculations and experimental data in the literature. The measured production cross sections for protons, deuterons, tritons, ³He, and α particles support the trends suggested by data at lower energies. Deduced partial kerma coefficients for carbon are also shown.     

Differential cross section and polarization for 2.63 MeV neutrons scattered from 12C

The differential cross section and polarization of 2.63 MeV neutrons scattered from ¹²C have been measured at eight angles between 17° and 118° in the laboratory system. By simultaneously fitting the cross section and polarization data, a set of scattering phase shifts was obtained. The values of the resulting d-wave phase shifts were larger than those of other existing sets of phase shifts in the energy region. A subsequent R-function analysis, reflecting these larger d-wave phase shifts, gave excellent fits to other experimental data below 3 MeV neutron energy region. The influence of narrow states at 7.50 and 7.55 MeV excitation energy in ¹³C is discussed.     

Cumulative fission yield measurements with 14.7 MeV neutrons on 238U

The fission yield data in the 14 MeV energy neutron induced fission of ²³⁸U play an important role in decay heat calculations and generation-IV reactor designs. In order to accurately measure fission product yields (FPYs) of ²³⁸U induced by 14 MeV neutrons, the cumulative yields of fission products ranging from ⁹²Sr to ¹⁴⁷Nd in the ²³⁸U(n, f) reaction with a 14.7 MeV neutron were determined using an off-line γ-ray spectrometric technique. The 14.7 MeV quasi-monoenergetic neutron beam was provided by the K-400 D-T neutron generator at China Academy of Engineering Physics (CAEP). Fission products were measured by a low background high purity germanium gamma spectrometer. The neutron flux was obtained from the ⁹³Nb (n, 2n)^92mNb reaction, and the mean neutron energy was calculated using the cross-section ratios for the ⁹⁰Zr(n, 2n)⁸⁹Zr and ⁹³Nb(n, 2n)^92mNb reactions. With a series of corrections, high precision cumulative yields of 20 fission products were obtained. Our FPYs for the ²³⁸U(n, f) reaction at 14.7 MeV were compared with the existing experimental nuclear reaction data and evaluated nuclear data, respectively. The results will be helpful in the design of a generation-IV reactor and the construction of evaluated fission yield databases.     

Scattemng of 14.1 MeV neutrons from 209Bi

Differential cross sections for the elastic and inelastic scattering of 14.1 MeV neutrons from ²⁰⁹Bi have been measured with a time-of-flight system which had an energy resolution of 650 keV. For elastic scattering from ²⁰⁹Bi, an optical-model analysis gave the best-fit potential parameters. The absolute cross sections for excitation of collective (2.66 and 4.36 MeV) states are reproduced by the results of distorted-wave calculations under the assumption of a core (²⁰⁸Pb) excitation model using deformation parameters obtained from (p, p') reactions.     

Fragmentation of 370 MeV/n 20Ne and 470 MeV/n 24Mg in light targets

Total charge-changing cross sections and cross sections for the production of projectile-like fragments were determined for fragmentation reactions induced by 370 MeV/n ²⁰Ne ions in water and lucite, and 490 MeV/n ²⁴Mg ions in polyethylene, carbon and aluminum targets sandwiched with CR-39 plastic nuclear track detectors. An automated microscope system and a track-to-track matching algorithm were used to count and recognize the primary and secondary particles. The measured cross sections were then compared with published cross sections and predictions of different models. Two models and the three-dimensional Monte Carlo Particle Heavy Ion Transport Code System (PHITS) were used to calculate total charge-changing cross sections. Both models agreed within a few percent for the system ²⁴Mg + CH₂, however a deviation up to 20% was observed for the systems ²⁰Ne + H₂O and C₅H₈O₂, when using one of the models. For all the studied systems, PHITS systematically underestimated the total charge-changing cross section. It was also found that the partial fragmentation cross sections for ²⁴Mg + CH₂ measured in present and earlier works deviated up to 20% for Z = 6–11. Measured cross sections for the production of fragments (Z = 4–9) for ²⁰Ne + H₂O and C₅H₈O₂ were compared with predictions of three different semi-empirical models and JQMD which is used in the PHITS code. The calculated cross sections differed from the measured data by 10–90% depending on which fragment and charge was studied, and which model was used.     

First track-structure measurements of 20 MeV protons with the STARTRACK apparatus

The STARTRACK experimental set-up, mounted on the +50° beam line of the Tandem-Alpi particle accelerator of Legnaro National Laboratories, has been conceived to give an experimental basis to nanodosimetric calculations. STARTRACK is based on a detection system able to measure ionization cluster distributions in a 20 nm propane site with a resolution of one ionization. The experimental layout has been designed to minimize pile-up distortions. The background noise is filtered by off-line dedicated software. Electron cluster distribution of 20 MeV protons has been measured. Monte Carlo data and experimental data are pretty well consistent.     

Neutron ambient dose equivalent from 5 MeV/u 10,11B, 12,13C and 16,18O projectiles incident on a thick Al target

The neutron ambient dose equivalent has been measured from ¹⁰B, ¹¹B, ¹²C, ¹³C, ¹⁶O and ¹⁸O projectiles of energy 5 MeV/amu incident on a thick Al target at 0°, 30°, 60° and 90° with respect to the beam direction using a conventional dose equivalent meter. The calculated results obtained using previously reported empirical relations do not reproduce the experimental data. The results obtained from the PACE nuclear reaction code are closer to the experimental data as compared to the various empirical expressions. The ratio of the increase in the dose rates when the projectile is changed from the lighter to the heavier isotopes is fairly reproduced by most of the empirical formulations and the PACE code. A previously reported relation for the slope parameter is used to predict the directional distribution of the neutron dose for the projectiles used in this study. The calculated doses are lower than the experimental results in the forward directions but agree within the uncertainties at the backward directions. A new set of projectile-based parameters have been derived from the present experimental data which can be used in an empirical formulation.     

Cross section measurements for the forward elastic scattering of 13 MeV 6,7Li and 24 MeV 16O from 9Be, 12C, 16O and 28Si

Absolute elastic cross sections have been measured at 12.45°, 16.45°, 20.45° and 28.0° for targets of ⁹Be, ¹²C, ¹⁶O, ²⁸Si and ¹⁹⁷Au being bombarded by beams of 13 MeV ^6,7Li and 24 MeV ¹⁶O. The reliability of a method previously proposed for low mass multielemental analysis [1,2] depends to some extent on the precision and accuracy of the cross sections reported here. The ¹⁶O-beam reactions, except the ¹⁶O + ⁹Be reaction, are found to be consistent with the Rutherford predictions. This allows us to obtain target thickness independent cross sections with uncertainties of approximately 7% for the reactions initiated with ^6,7Li beams. Most of these cross sections are found to be non-Rutherford. Comparisons made with previous investigations give strong support to the cross section values obtained in this work.     

The polarization of MeV neutrons elastically scattered from 4He

The analyzing power of ⁴He for neutron elastic scattering has been measured at four angles between 20° and 80° (lab) throughout the energy range 1.5–6.0 MeV using a doublescattering method. The intense flux of polarized neutrons was generated via the reactions Pb(γ, n) → ¹²C(n, $\text{n}$)¹²C, and the magnitude of the polarization of the neutron beam measured absolutely in a separate double-scattering experiment. Neutron energies were determined with a nanosecond time-of-flight spectrometer, and the generalized neutron spin-precession method was used to minimize systematic uncertainties.     

An upgrade of the SCANDAL setup for measurements of elastic neutron scattering at 175 MeV

The experimental setup SCANDAL, used for measurements of the differential cross section for elastic and inelastic neutron scattering, has recently been upgraded with larger CsI scintillating detectors to enable measurements at energies up to 175 MeV. Measurements on Fe, Bi and Si have been carried out using the quasi mono-energetic neutron beam at the The Svedberg Laboratory, and data is under analysis. The experimental setup can be used for measurements on a wide range of target nuclei, including C and O, which are important for dosimetry applications. SCANDAL can also run in proton mode, for measurements of the (n,p) reaction. This paper describes the new experimental setup, and reports on its properties, such as energy resolution.     

The 10,11B(n, p)10,11Be reactions at En=96 MeV

Double-differential cross sections of the ^10,11B(n, p)^10,11Be reactions have been measured at 96 MeV in the angular range 0°–30° for excitation energies up to 35 MeV. The spectra have been decomposed into different multipolarities using sample angular distributions calculated within the distorted-wave Born approximation. From the identified Gamow–Teller strength, S_β⁺ values were obtained for ¹⁰B and ¹¹B. At higher excitation energies, the spectra are dominated by L=1 strength in broad distributions with maxima around 22 and 12 MeV in ¹⁰B and ¹¹B, respectively.     

Scattering of 1 and 2 MeV neutrons from oriented 165Ho

The “deformation effect” in the neutron-¹⁶⁵Ho differential scattering cross section, defined as the relative variation of the cross section induced by the orientation of the target, has been measured at 1 and 2 MeV incident neutron energy, in the scattering angular interval from 30° to 130°. A polycrystalline holmium target has been employed, oriented normally to the scattering plane, with a nuclear alignment parameter $\text{B}{}_2\text{B}{}_{\mathrm{<mtext>2\; </mtext><mtext>max</mtext>}}\text{= 0.24}$. The observed effect has an oscillating character as a function of the scattering angle with a maximum value of 0.12 ± 0.02 at 2 (emMeV). The effect has been theoretically calculated by an adiabatic coupled-channel calculation performed by using the optical model and deformation parameters deduced from the analysis of previous experiments. The agreement between the experimental and the theoretical results is good, particularly at 2 MeV energy where the compound nucleus contribution in the scattering is negligible.     

Cross section measurements on zirconium isotopes for ~14 MeV neutrons and their theoretical calculations of excitation functions

The cross sections for the ⁹⁴Zr(n,d*)^93m+gY, ⁹⁶Zr(n,γ)⁹⁷Z, ⁹⁶Zr(n,2n)⁹⁵Zr, ⁹⁰Zr(n,α)^87mSr, ⁹⁴Zr(n,α)⁹¹Sr,⁹⁰Zr(n,p)^90mY, ⁹²Zr(n,p)⁹²Y, and ⁹⁴Zr(n,p)⁹⁴Y reactions have been measured in the neutron energy range of 13.5-14.8 MeV by means of the activation technique. The neutrons were produced via the D-T reaction. A high-purity germanium detector with high energy resolution was used to measure the induced γ activities. In combination with the nuclear reaction theoretical models, the excitation curves of the above-mentioned eight nuclear reactions within the incident neutron energy range from the threshold to 20 MeV were obtained by adopting the nuclear theoretical model program system Talys-1.9. The resulting experimental cross sections were analyzed and compared with the experimental data from published studies. Calculations were performed using Talys-1.9 and are in agreement with our experimental results, previous experimental values, as well as results of the theoretical excitation curves at the corresponding energies. The theoretical excitation curves generally match the experimental data well.     

Spin-flip probability in the inelastic scattering of 16.9 MeV neutrons from 12C

The neutron spin-flip probability S(θ) for inelastic scattering of unpolarized 16.9 MeV neutrons to the 4.44 MeV state of ¹²C has been determined by measuring the absolute directional correlation between the scattered neutrons and the subsequent E2 deexcitation γ- radiation emitted perpendicular to the scattering plane. Time-of-flight techniques with carbon recoil detection in a plastic scintillator were used to separate elastically and inelastically scattered neutrons. The neutron spin-flip data were found to be in close agreement with 20.0 MeV proton spin-flip results. Comparison of the measurement is made with the predictions of a microscopic antisymmetrized distorted wave calculation in which the direct reaction mechanism is supplemented by a two step resonance contribution. This theoretical analysis reveals the presence of a strong quadrupole resonance at 20.5 MeV excitation in ¹²C. The results are also influenced to a lesser extent by the E1 giant dipole resonance.     

Mass yield distributions of target fragments from the reactions of iron with 135 MeV/nucleon 12C and 80 MeV/nucleon 16O ions

Cross sections for the production of target fragments in the reactions of iron with 135 MeV/nucleon ¹²C and 80 MeV/nucleon ¹⁶O ions have been measured by off-line γ-ray spectroscopy. Through these data, the mass yield distributions have been obtained. The result of the experiment for the reaction with 135 MeV/nucleon ¹²C ions is compared with theoretical calculations using the fusion-fragmentation model and the GEMINI code for sequential binary decay, following a calculation with the fireball model. Reveived: 24 March 1999 / Revised version: 16 July 1999     

Mass attenuation coefficient of saccharides for X-rays in the energy range from 8 keV to 32 keV

Mass attenuation coefficients have been measured for mono and disaccharides at photon energies 8.136, 13.596, 17.781, 22.581 and 32.890 keV. The measured values are compared with the computed values obtained using personal computer software package WinXCOM. The agreement between the two is within −5.3% to 3%.     

Neutron induced light-ion production from iron and bismuth at 175 MeV

We have measured light-ion (p, d, t, ³He and α) production in the interaction of 175 MeV neutrons with iron and bismuth with low-energy thresholds and for a wide angular range (from 20° to 160°, in steps of 20°). Measurements have been performed with the Medley setup, semi-permanently installed at the The Svedberg Laboratory, Uppsala (Sweden), where a quasi-monoenergetic neutron beam is available and well characterized. Medley is a conventional spectrometer system and consists of eight telescopes, each of them composed of two silicon surface barrier detectors, to perform particle identification, and a CsI(Tl) scintillator to fully measure the kinetic energy of the produced light-ions. We report preliminary double-differential cross sections for production of protons, deuterons and tritons in comparison with model calculations using TALYS-1.0 code. These show better agreement for the production of protons, while the theoretical calculations seem to overestimate the experimental production of deuterons and tritons.     

Spin-flip probability for 7.6 MeV neutrons scattered inelastically (Q = −2.23 MeV) by a sulfur target

The spin-flip probability for 7.6 MeV (ΔE = 0.250 MeV) neutrons scattered inelastically (Q = ?2.23 MeV) from naturally occuring sulfur has been measured at scattering angles between 40° and 160° using a γ-correlated neutron time-of-flight method. The scattering by the natural sulfur target was assumed to be characteristic of ³²S. The results of the measurement were compared with an incoherent sum of statistical compound-nucleus (CN) and direct-interaction (DI) contributions. The DI contributions were obtained using either a DWBA calculation or the coupled-channel (CC) formalism. Neither combination of CN plus DI contributions reproduced the experimental spin-flip probability angular distribution which was peaked near 110° with a maximum value of 0.33 ± 0.08.     

Simultaneous 13C/12C and (18)O/(16)O isotope ratio measurements on CO2 based on off-axis integrated cavity output spectroscopy

A prototype off-axis integrated cavity output spectrometer (OA-ICOS) utilizing two identical cavities together with a near-infrared (1.63 microm) external cavity tunable diode laser is described. The two-cavity design-one for a reference gas and one for a sample gas-takes advantage of classical double-beam infrared spectrometer characteristics in reducing uncertainties due to laser scan or power instabilities and major temperature variations by a factor of three or better compared with a single-cavity scheme. This is the first OA-ICOS instrument designed to determine 13C/12C and (18)O/(16)O ratios from CO2 rotation/vibration fine structure in three different combination bands. Preliminary results indicate that at 0.8 Hz a precision of 3.3 and 2.8 per thousand is obtained for delta13C and delta(18)O, respectively, over a period of 10 h and a pure CO2 gas sample at 26 hPa. By averaging 100 spectra over a subset of the data, we achieved a precision of 1.6 and 0.8 \permil\ for delta13C and delta(18)O, respectively.     

Aspects of α-emission from the bombardment of 58Ni with 14.7 MeV neutrons

An enriched ⁵⁸Ni target has been bombarded with 14.7 MeV neutrons and the energies and angular distributions of the outgoing α-particles have been measured. A statistical theory analysis has been made which yields a value of 1.022 ± 0.15 MeV for the nuclear temperature and a value of 9.7 ± 0.45 MeV^?1 for the level density parameter of ⁵⁵Fe. The total cross section has also been measured. The results have been compared with previous measurements.