Light-ion Production Research Articles

Medley spectrometer for light ions in neutron-induced reactions at 175 MeV

We have upgraded the Medley spectrometer to measure neutron-induced double differential cross-sections for light-ion production, with neutron energies up to 175 MeV. Measurements were performed at the quasi-monoenergetic neutron beam line at the The Svedberg Laboratory, in Uppsala (Sweden). Medley is a spectrometer system composed of eight three-element telescope detectors; Δ E – E technique is used for particle identification and total kinetic energy measurement. We have improved particle separation and installed new detectors that fully stop ions with kinetic energy up to 170 MeV. To reduce the contribution of the low energy tail in the quasi-monoenergetic neutron spectrum, we have applied time-of-flight techniques and investigated the results for measurements with 175 MeV neutrons. We have investigated the response function of the CsI(Tl) scintillators and describe a method for efficiency correction. We have studied the signal-to-background ratio of the new configuration of the spectrometer and of the collimation system. A method to obtain absolute cross-section normalization, separating the peak neutrons from the low-energy tail, is proposed. Finally we have characterized the 175 MeV quasi-monoenergetic neutron spectrum with the Medley spectrometer. This upgraded configuration has been used in 2007 and 2009 for light-ion production measurements at 175 MeV from C, Si, O, Fe, Bi and U.

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, He-3 and alpha) production in carbon induced by 96 MeV neutrons have been measured at eight laboratory angles from 20 to 160 in steps of 20 degrees. 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, He-3, and alpha particles support the trends suggested by data at lower energies. Deduced partial kerma coefficients for carbon are also shown.

C/O Kerma coefficient ratio for 96 MeV neutrons deduced from microscopic measurements

Double-differential cross sections for neutron-induced light-ion production at 96 MeV have been measured for a variety of nuclei at The Svedberg Laboratory. Using the measured cross-section data, we deduce the Kerma coefficient from carbon and oxygen for p, d, t, He-3 and alpha particles. In order to get the total Kerma for C and O, we add GNASH calculation values where experimental data are not available and obtain a Kerma coefficient of 7.85 +/- 0.63 fGy m(2) for carbon and 7.09 +/- 0.57 fGy m(2) for oxygen. The C/O Kerma coefficient ratio then becomes 1.11 +/- 0.11. In addition we determine the Kerma ratio between ICRU muscle and A-150, again adding calculations with the GNASH code where no experimental data are available, and obtain a value of 0.98 +/- 0.05. While the Kerma coefficients for carbon and oxygen do not agree with the prediction in ICRU Report 63, the ratio values are in good agreement with existing predictions.

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

We have measured light-ion (p, d, t, He-3 and alpha) production in the interaction of 175 MeV neutrons with iron and bismuth with low-energy thresholds and for a wide angular range (from 20 degrees ...

A Medley with over ten years of (mostly) light-ion production measurements at The Svedberg Laboratory

Over the past years an experimental programme has been run at the neutron beam of The Svedberg Laboratory with the aim to study light-ion production induced by 96 and 175 MeV neutrons for a wide variety of targets. The measurements have been conducted using the Medley facility which allows measurement of p, d, t, He-3 and alpha production at fixed angles (from 20 to 160 degrees in steps of 20 degrees) over a wide dynamic range. An overview of the results obtained at the now finished campaign at 96 MeV will be given. Since 2007 we have been running at 175 MeV with C, O, Si, Fe, Bi and U as target material. Preliminary results from these measurements will be shown and compared to model calculations with Talys-1.2. We also summarize the Medley measurements of elastic np and nd scattering and of angular distributions of fission fragments.

Neutron induced light-ion production from Iron and Bismuth at 175 MeV

Neutron induced light-ion production from Iron and Bismuth at 175 MeV

175 MeV 準単色中性子入射によるシリコンからの軽イオン生成収量の測定

175 MeV 準単色中性子入射によるシリコンからの軽イオン生成収量の測定

Light-ion production in the interaction of 96 MeV neutrons with carbon

Double-differential cross sections for light-ion (p, d, t, 3He and alpha) production in carbon induced by 96 MeV neutrons have been measured at eight laboratory angles from 20 degrees to 160 degrees in steps of 20 degrees. Experimental techniques are presented as well as procedures for data taking and data reduction. Deduced energy-differential, angle-differential and production cross sections are reported. Experimental cross sections are compared with theoretical reaction model calculations and experimental data in the literature. The measured particle data show marked discrepancies from the results of the model calculations in spectral shape and magnitude. The measured production cross sections for protons, deuterons, tritons, 3He, and alpha particles support the trends suggested by data at lower energies.

Quantum molecular dynamics calculation of light-ion production in neutron-induced reactions at intermediate energies

A quantum molecular dynamics (QMD) simulation is applied to light-ion production in neutron-induced reactions on O, Si and Fe at E(n) = 96 MeV. The generalized evaporation model (GEM) is used to account for statistical decay processes after the QMD stage. Good agreement with the experimental energy spectra is obtained for proton emission, but the calculation exhibits remarkable underestimation for pre-equilibrium emission of light clusters, i.e. d, t, (3)He and (4)He. It is found that the underestimation is improved except in the region around the high energy end of the emission spectra by implementation of a phenomenological coalescence model into the QMD under the assumption that these light clusters are formed in the nuclear surface region by a leading nucleon that is ready to leave the nucleus.

Neutron-induced light-ion production from Fe, Pb and U at 96 MeV

Double-differential cross-sections for light-ion production (up to A = 4) induced by 96 MeV neutrons have been measured for Fe, Pb and U. The experiments have been performed at The Svedberg Laboratory in Uppsala, using two independent devices, MEDLEY and SCANDAL. The recorded data cover a wide angular range (20 degrees -160 degrees ) with low energy thresholds. The data have been normalised to obtain cross-sections using np elastic scattering events. The latter have been recorded with the same setup, and results for this measurement are reported. The work was performed within the HINDAS collaboration with the primary aim of improving the database for three of the most important nuclei for incineration of nuclear waste with accelerator-driven systems. The obtained cross-section data are of particular interest for the understanding of the so-called pre-equilibrium stage in a nuclear reaction and will be compared with model calculations.

Light charged-particle production in 96 MeV neutron-induced reactions on carbon and oxygen

In recent years, an increasing number of applications involving fast neutrons have been developed or are under consideration, e.g. radiation treatment of cancer, neutron dosimetry at commercial aircraft altitudes, soft-error effects in computer memories, accelerator-driven transmutation of nuclear waste and energy production and determination of the response of neutron detectors. Data on light-ion production in light nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron beams, and for dosimetry of high-energy neutrons produced by high-energy cosmic radiation interacting with nuclei (nitrogen and oxygen) in the atmosphere. When studying neutron dose effects, it is especially important to consider carbon and oxygen, since they are, by weight, the most abundant elements in human tissue. Preliminary experimental double-differential cross sections of inclusive light-ion (p, d, t, (3)He and alpha) production in carbon induced by 96-MeV neutrons have been presented. Energy spectra were measured at eight laboratory angles: 20, 40, 60, 80, 100, 120, 140 and 160 degrees. Measurements were performed at The Svedberg Laboratory (TSL), Uppsala, using the dedicated MEDLEY experimental setup. The authors have earlier reported experimental double-differential cross sections of inclusive light-ion production in oxygen. In this paper, the deduced kerma coefficients for oxygen has been presented and compared with reaction model calculations.

Optimization of ECR ion sources for high charge state beam generation

The most important developments in the field of ion sources have been based on the generation of warm plasmas by means of microwaves at different frequencies.Different type of sources as electron cyclotron resonance ion sources (ECRIS) and microwave discharge ion sources have been designed and built at INFN-LNS, at operating frequencies between 2.45 and 28GHz, with different purposes ranging from high efficiency ionization or high current production of light ions to high charge state generation of heavy ion beams.The production of intense beams of highly charged ions (HCIs) has been a major task in the last few years.Different solutions have been proposed to improve the production rate. In particular the microwave coupling to plasma can be significantly improved with beneficial effects on ion beam current.Experimental activities in the field of microwave coupling to plasmas at different frequencies (14, 18 and 28GHz) along with theoretical modelling of the plasma formation and confinement have been undertaken to improve production of HCI.The description of the different methods and tasks to improve the performances of such sources will be carried out, along with a scenario of the existing and forthcoming ECRIS for HCI production.

Description of light ion production cross sections and fluxes on the Mars surface using the QMSFRG model

The atmosphere of Mars significantly attenuates the heavy ion component of the primary galactic cosmic rays (GCR), however, increases the fluence of secondary light ions (neutrons, and hydrogen and helium isotopes) because of particle production processes. We describe results of the quantum multiple scattering fragmentation (QMSFRG) model for the production of light nuclei through the distinct mechanisms of nuclear abrasion and ablation, coalescence, and cluster knockout. The QMSFRG model is shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections. We use the QMSFRG model and the space radiation transport code, HZETRN to make predictions of the light particle environment on the Martian surface at solar minimum and near maximum. The radiation assessment detector (RAD) experiment will be launched in 2009 as part of the Mars Science Laboratory (MSL). We make predictions of the expected results for time dependent count-rates to be observed by the RAD experiment. Finally, we consider sensitivity assessments of the impact of the Martian atmospheric composition on particle fluxes at the surface.

Neutron cross-sections above 20 MeV for design and modeling of accelerator driven systems

One of the outstanding new developments in the field of partitioning and transmutation (P&T) concerns accelerator-driven systems (ADS) which consist of a combination of a high-power, high-energy accelerator, a spallation target for neutron production and a sub-critical reactor core. The development of the commercial critical reactors of today motivated a large effort on nuclear data up to about 20 MeV, and presently several million data points can be found in various data libraries. At higher energies, data are scarce or even non-existent. With the development of nuclear techniques based on neutrons at higher energies, nowadays there is a need also for higher-energy nuclear data. To provide alternative to this lack of data, a wide program on neutron-induced data related to ADS for P&T is running at the 20-180 MeV neutron beam facility at 'The Svedberg Laboratory' (TSL), Uppsala. The programme encompasses studies of elastic scattering, inelastic neutron production, i.e., (n, xn') reactions, light-ion production, fission and production of heavy residues. Recent results are presented and future program of development is outlined.

Light-ion production in the interaction of 96 MeV neutrons with oxygen

Double-differential cross sections for light-ion (p, d, t, He-3 and alpha) production in oxygen, induced by 96 MeV neutrons are reported. Energy spectra are measured at eight laboratory angles from 20 degrees to 160 degrees in steps of 20 degrees. Procedures for data taking and data reduction are presented. Deduced energy-differential and production cross sections are reported. Experimental cross sections are compared to theoretical reaction model calculations and experimental data at lower neutron energies in the literature. The measured proton data agree reasonably well with the results of the model calculations, whereas the agreement for the other particles is less convincing. The measured production cross sections for protons, deuterons, tritons and alpha particles support the trends suggested by data at lower energies.

Erratum: Light-ion production in the interaction of 96 MeV neutrons with silicon [Phys. Rev. C69, 064609 (2004)

Double-differential cross sections for light-ion (p, d, t, He-3 and alpha) production in silicon, induced by 96 MeV neutrons are reported. Energy spectra are measured at eight laboratory angles, ranging from 20 degrees to 160 degrees in steps of 20 degrees. Procedures for data taking and data reduction are presented. Deduced energy-differential, angle-differential and production cross sections are reported. Experimental cross sections are compared to theoretical reaction model calculations and experimental data in the literature.

Light-ion production in the interaction of96MeVneutrons with silicon

Double-differential cross sections for light-ion ($p$, $d$, $t$, $^{3}\mathrm{He}$, and $\ensuremath{\alpha}$) production in silicon, induced by $96\phantom{\rule{0.3em}{0ex}}\text{MeV}$ neutrons, are reported. Energy spectra are measured at eight laboratory angles from $20\ifmmode^\circ\else\textdegree\fi{}$ to $160\ifmmode^\circ\else\textdegree\fi{}$ in steps of $20\ifmmode^\circ\else\textdegree\fi{}$. Procedures for data taking and data reduction are presented. Deduced energy-differential, angle-differential, and production cross sections are reported. Experimental cross sections are compared to theoretical reaction model calculations and experimental data in the literature.

The role of cosmic rays in the atmospheric processes

The energy flux of galactic cosmic rays falling on the earth's atmosphere is small in comparison with solar electromagnetic irradiation (by 108 times). But at altitudes of h ∼ 3 to 35 km in the atmosphere, cosmic rays are the only ionization source (from the ground level up to h ∼ 3 km, natural radioactivity is an additional source of ionization). Solar activity modulates cosmic ray flux. The cosmic rays produce atmospheric ions that define the electrical properties of the atmosphere. The electric charges play a very important role in the processes of cloud and thundercloud formation in the operation of the global electric circuit. The changes in electric properties of the atmosphere influence weather and climate. Thus, we have the following chain of the solar terrestrial relationship: solar activity—cosmic ray modulation—changes in the global electric properties of the atmosphere—changes in weather and climate. The following questions are discussed in this paper: light ion production in the atmosphere, role of electric charges in the formation of clouds and thunderclouds, experimental evidences of the relationships between cosmic ray flux and atmospheric current and lightning.

Experimental Double-Differential Light-Ion Production Cross Sections for Silicon at 95 MeV Neutrons

The importance of cosmic radiation effects in aircraft electronics has recently been highlighted. At commercial flight altitudes, as well as at sea level, the most important particle radiation is due to neutrons, created in the atmosphere by spallation of nitrogen and oxygen nuclei, induced by cosmic-ray protons. When, e.g., an electronic memory circuit is exposed to neutron radiation, charged particles can be produced in a nuclear reaction. The charge released by ionization can cause a flip of the memory content in a bit, which is called a single-event upset (SEU). A similar logic error in one of the storage registers of a microprocessor may trigger an unanticipated loop that cannot be escaped without turning the unit off.To get a deeper understanding of these phenomena, more detailed cross section information on neutron-induced charged-particle production at intermediate energies is needed. To this end, double-differential cross sections of inclusive light-ion production in silicon, induced by 95 MeV neutrons, have been measured. The experiment was performed using the MEDLEY setup, which consists of eight three-element particle telescopes, covering the angular range 20° – 160°. The charged particles were identified using ΔE – ΔE – E techniques. By using an active target, consisting of a 300 μm thick Si detector, the energy loss in the target itself could be measured and corrected for.

Cross Section Data and Kerma Coefficients at 95 MeV Neutrons for Medical Applications

Motivated by the need of data on neutron-induced reactions with biologically relevant materials, e.g., carbon and oxygen, we have constructed and installed the MEDLEY detector array at the neutron beam facility of the The Svedberg Laboratory in Uppsala. The central detection elements of MEDLEY are three-detector telescopes, consisting of two silicon detectors and a Csl crystal. To cover wide energy and angle ranges, we have mounted eight such telescopes at 20° intervals. We have used ΔE − ΔE − E techniques to obtain good particle identification for protons, deuterons, tritons, 3He and α particles over an energy range from a few MeV up to 100 MeV. To define the detector solid angle, plastic scintillators were employed to serve as active collimators.We have up to now measured double-differential cross sections of inclusive light-ion production induced by 95 MeV neutrons on carbon and oxygen. From these data production cross sections, as well as partial kerma coefficients, are being determined. We have found that especially the proton kerma coefficient for carbon is substantially larger than that of a recent evaluation, leading to a larger total kerma coefficient. The obtained data supports a trend observed for similar data at lower energies.