Thick Beryllium Target Research Articles

Cross-sections of large-angle hadron production in proton- and pion-nucleus interactions I: beryllium nuclei and beam momenta of +8.9 GeV/c and −8.0 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, deuterons, and charged pions and kaons, in the interactions with a 5% λ abs thick stationary beryllium target, of a +8.9 GeV/c proton and pion beam, and a −8.0 GeV/c pion beam. Results are given for secondary particles with production angles 20○<θ<125○.

The BSA modeling for the accelerator-based BNCT facility at INFN LNL for treating shallow skin melanoma

The SPES-BNCT ongoing project of the Istituto Nazionale di Fisica Nucleare (INFN) is aimed at the construction at the Laboratori Nazionali di Legnaro (LNL) of an accelerator-based (AB), high-flux thermal neutron beam facility devoted to boron neutron capture therapy (BNCT) experimental treatment of extended skin melanoma, in the framework of SPES (selective production of exotic species) project. The neutron source will be produced via the 9Be(p,xn) reactions by a 5 MeV, 30 mA proton beam into a thick beryllium target. The resulting neutron spectrum is slowed down using a beam shaping assembly (BSA), for which modeling is in an advanced neutronic design stage. An overview on the BSA current status, based on the Be neutron converter prototype designed and already constructed, is reported.

Angle and energy differential neutron spectrometry for the SPES BNCT facility

An accelerator-driven thermal neutron facility for boron neutron capture therapy of skin melanoma is currently under construction at the Legnaro National Laboratories, Italy. The installation relies on the production of neutrons from a thick beryllium target bombarded with 5 MeV protons. A complete set of double differential data, i.e. angle- and energy-differential neutron spectra produced by the beryllium target, is necessary for the Monte Carlo-based design of the installation. For this purpose, double differential fluence measurements are currently performed with the “BINS” neutron spectrometer using 5 MeV protons at the “CN” Van de Graaf accelerator. This spectrometer uses a superheated emulsion of dichlorotetrafluoroethane which is sequentially operated at 25, 30, 35, 40, 45, 50 and 55 °C and thus provides a series of seven sharp thresholds covering the 0.1–10 MeV neutron energy interval. Deconvolution of the data is performed with the code “MAXED”, which is based on the maximum entropy principle. The analysis of our first neutron spectrometry measurements at angles of 0°, 40°, 80° and 120° supports the viability of the BINS spectrometry method for the generation of the required double differential data.

Development and test of high efficiency WSF fluorescent converter for fast neutron radiography

A fluorescent converter used for fast neutron radiography (FNR) was developed by using the Chinese made wavelength-shifting fibers (WSFs) and mixture of hydrogen rich epoxy resin with ZnS(Ag). The performance of the WSF converter compared with that of the epoxy resin converter (ER converter) was tested at the 4.5 MV Van de Graaff accelerator of Peking University as fast neutron source. Quasi-monoenergetic and continuous energy fast neutrons were derived through the D(d,n) 3He and 9Be(d,n) 10B reactions by using a deuterium gas target and a thick beryllium target, respectively. Experiments show that the luminosity of the WSF converter is 6–7.8 times as high as that of the ER converter we used before, and the statistics of the image is much better. The relationship between the luminosity and the thickness of the WSF converter was obtained from which the saturation thickness is about 25 mm. The smallest defect that can be detected by the WSF converter is about 2 mm.

Neutron spectrometry with a monolithic silicon telescope

A neutron spectrometer was set-up by coupling a polyethylene converter with a monolithic silicon telescope, consisting of a DeltaE and an E stage-detector (about 2 and 500 microm thick, respectively). The detection system was irradiated with monoenergetic neutrons at INFN-Laboratori Nazionali di Legnaro (Legnaro, Italy). The maximum detectable energy, imposed by the thickness of the E stage, is about 8 MeV for the present detector. The scatter plots of the energy deposited in the two stages were acquired using two independent electronic chains. The distributions of the recoil-protons are well-discriminated from those due to secondary electrons for energies above 0.350 MeV. The experimental spectra of the recoil-protons were compared with the results of Monte Carlo simulations using the FLUKA code. An analytical model that takes into account the geometrical structure of the silicon telescope was developed, validated and implemented in an unfolding code. The capability of reproducing continuous neutron spectra was investigated by irradiating the detector with neutrons from a thick beryllium target bombarded with protons. The measured spectra were compared with data taken from the literature. Satisfactory agreement was found.

Direct mass measurements of neutron-deficient 152Sm projectile fragments at the FRS-ESR facility

The FRS-ESR facility at GSI provides one of the most efficient methods for direct mass measurements. In the present experiment, exotic nuclei were produced via fragmentation of 152Sm projectiles in a thick beryllium target at 500-600 MeV/u, separated in-flight with the fragment separator FRS, and injected into the storage-cooler ring ESR. Time-resolved Schottky Mass Spectrometry was applied for mass measurements of stored and electron-cooled bare and few-electron ions. 373 different nuclides were identified by means of the spectra of their revolution frequencies. Masses for 18 nuclides (84Zr, 92Ru, 94Rh, 107,108,110Sb, 111,112,114I, 118Ba, 122,123La, 124Ce, 127Pr, 129Nd, 132Pm, 134Sm, 137Eu) have been determined for the first time. Masses for 111,112I and 113Xe have been obtained via known α-decay energies. The experiment and first results will be presented.

Radiation damage study of GaAs detectors irradiated by fast neutrons

Abstract We investigated the radiation hardness of GaAs pad detectors irradiated by fast neutrons. The main goal was to determine the degradation of the charge collection efficiency (CCE) of the irradiated detectors and to measure the charge transport properties in terms of the μτ-product. Several GaAs pad detectors have been irradiated by fast neutrons (2–37 MeV) with varying fluence (1012–1015 n/cm2). Neutrons were produced at a cyclotron by means of the (p,n) reaction on a thick beryllium target. Alpha spectra and I–V curves were obtained before and after irradiation. Basic parameters for description of charge-carrier transport were determined as dependent on radiation damage. The measurements prove a degradation of the CCE and the disappearance of the rectifying junctions of the detectors as result of radiation damage.

Measurements of fast-neutron-induced signals in silicon pad detectors

The aim of this work was to understand possible fast neutron contribution to background signals in the Semiconductor Tracker (SCT) of the ATLAS detector which is built on LHC at CERN. We measured current pulses induced by fast-neutron reactions in silicon pad detectors. Neutrons were produced at the Rez cyclotron by means of the (p,n) reaction on a thick beryllium target. Current pulses were stored by a fast digital oscilloscope for off-line analysis. Pulse-height spectra, corresponding to neutron interactions in the detector mainly due to (n,p) and (n,α) reactions, were obtained by integration of the pulses. The sensitivity of the detector against neutrons was estimated from analysis of the distribution of time intervals between two subsequent pulses. The neutron-induced signals correspond to an average energy deposition of several MeV and arise in the silicon detector of 1 cm 2 area with an average time spacing of about 575 μs. Results are compared with Monte-Carlo simulations.

β-decay of the neutron-rich nucleusN18

The β-decay of N18 has been studied using β−n and β−γ coincidence methods. The N18 ions were produced by the fragmentation of the E/A=68.8 MeV Ne22 beam on a thick beryllium target. A newly constructed neutron detector system with wide energy detection range and low-energy detection threshold was used. The 619 ± 2 ms half-life of the N18 β-decay was found to be in very good agreement with the previous measurements. Transitions to 11 β-delayed neutron emitting states in O18 have been observed with a total branching ratio of 6.98 ± 1.46%. The Gamow-Teller β-decay strengths of N18 to these levels were deduced and compared with the shell model calculations. The intensities of the strong γ-ray transitions in O18 were found to be consistent with recent work.Received 2 September 2005DOI:https://doi.org/10.1103/PhysRevC.72.064327©2005 American Physical Society

Secondary photon fields produced in accelerator-based sources for neutron generation

Neutrons can be produced with low-energy ion accelerators for many applications, such as the characterisation of neutron detectors, the irradiation of biological samples and the study of the radiation damage in electronic devices. Moreover, accelerator-based neutron sources are under development for boron neutron capture therapy (BNCT). Thin targets are used for generating monoenergetic neutrons, while thick targets are usually employed for producing more intense neutron fields. The associated photon field produced by the target nuclei may have a strong influence on the application under study. For instance, these photons can play a fundamental role in the design of an accelerator-based neutron source for BNCT. This work focuses on the measurement of the photon field associated with neutrons that are produced by 4.0-6.8 MeV protons striking both a thin 7LiF target (for generating monoenergetic neutrons) and a thick beryllium target. In both cases, very intense photon fields are generated with energy distribution extending up to several MeV.

Performance of a neutron spectrometer based on a PIN diode

The neutron spectrometer discussed in this work consists of a PIN diode coupled with a polyethylene converter. Neutrons are detected through the energy deposited by recoil-protons in silicon. The maximum detectable energy is -6 MeV and is imposed by the thickness of the fully depleted layer (300 microm for the present device). The minimum detectable energy which can be assessed with pulse-shape discrimination (PSD) is -0.9 MeV. PSD is performed with a crossover method and setting the diode in the 'reverse-injection' configuration (i.e. with the N+ layer adjacent to the converter). This configuration provides longer collection times for the electron-hole pairs generated by the recoil-protons. The limited interval of detectable energies restricts the application of this spectrometer to low-energy neutron fields, such as the ones which can be produced at facilities hosting low-energy ion accelerators. The capacity to reproduce continuous neutron spectra was investigated by optimising the electronic chain for pulse-shape discrimination. In particular, the spectrometer was irradiated with neutrons that were generated by striking a thick beryllium target with protons of several energies and the measured spectra were compared with data taken from the literature.

Neutron irradiation field produced by 25 MeV deuterons bombarding on thick beryllium target for radiobiological study

A fast neutron irradiation field for biological studies was established at the cyclotron facility in the National Institute of Radiological Sciences. Neutron spatial distributions and absorbed dose distributions were measured to characterize the neutron field. By using a simple technique that an aluminum plate activated by neutrons was exposed to the imaging plates, the width of the neutron-irradiated area was measured to be 23.6 cm with 2.5 mm spatial resolution. The absorbed dose distributions of neutrons and γ rays were obtained separately by using a tissue-equivalent plastic- and a graphite-walled low-pressure proportional counter. The neutron absorbed dose in a tissue-equivalent plastic was measured to be 144.6 (Gy/C). It was confirmed that this neutron field has only 1.8% contamination of γ -ray dose and has good quality for neutron irradiation to biological samples.

Biological effects of radioactive 9C-ion beams on cells

The distinguishing feature and current technique progress of tumor treatment with heavy-ion beams is introduced in the paper. Additional superiority to tumor treatment from a radioactive ion beam (RIB) is emphatically discussed. The experimental research of the radioactive 9C-ion beams aimed at tumor treatment at Heavy Ion Medical Accelerator in Chiba (HIMAC), National Institute of Radiological Sciences (NIRS), Japan is described in detail, including production of the beams, optimization of parameters, distribution of depth dose, survival effect of cell and comparison of RBE between 9C- and 12C-beams. Results show that under 40 mm thick Beryllium target and 10 mm thick aluminum degrader at full (5%) momentum acceptance, the production rate and purity of the produced 9C-beams are 9.07×l06 and 82.88% respectively with the primary 12Cbeams of 430 MeV/u and 1.8×l09 pps. A uniform irradiation field with homogeneity up to 89.6% inside central area 10 mm in diameter is obtained by using spot scanning. In this case, the dose rate at the entrance is 0.5 Gy/h. In survival experiment of cells, the average relative biological effectiveness (RBE) of 9C-beams is 5.28 and 2.93 for 12C-beams in the region around Bragg peak. The RBE of 9C-beams is 1.8 times higher than that of 12C-beams. It indicates that cell-killing efficiency of 9C-beams is stronger than that of {u12}C-beams. 9C-beams are more efficacious for tumor treatment than 12C-beams.

Neutron spectrometry with a recoil radiator-silicon detector device

A neutron spectrometer consisting of a commercial p–i–n diode coupled with a polyethylene converter was developed and tested. The spectra of the energy deposited by recoil-protons in the silicon detector were measured with mono-energetic neutron beams. The spectra of deposited energy were also calculated analytically and with Monte Carlo simulations using the FLUKA code. The effect of secondary charged particles produced by thermal and fast neutron interactions in the silicon diode was also investigated. Further measurements were made for neutrons generated by 5MeV protons striking a thick beryllium target. The derived neutron spectrum was compared with spectra from the literature. Satisfactory agreement was found. The use of the spectrometer is limited by the effect of photons.

Experimental results on RPC neutron sensitivity

RPC neutron sensitivity has been studied during two tests done with different neutrons energies. In the first test, neutrons from spontaneous fission events of 252Cf were used (average energy 2MeV); while in the second test neutrons were produced using a 50MeV deuteron beam on a 1cm thick beryllium target (average energy 20MeV). Preliminary results show that the neutron sensitivity in double gap mode is (0.52±0.03)×10−3 at about 2MeV and (5.3±0.5)×10−3 at about 20MeV.

Total cross sections for 4,6He + 28Si reactions measured at 10–28 MeV/A

New results on the energy dependence of the total cross section (σ R) for 6He scattering on 28Si in the incident energy range 10–28 MeV/A are obtained. The α-particle-production cross sections for the 28Si(6He, 4He)X channel are measured as well. The secondary beam of 6He with an intensity of up to 5×104 particle/s was generated by bombarding a thick beryllium target with ∼32-MeV/A 7Li ions. In the energy region below 17 MeV/A, σ R increases sharply. The experimental dependences of the total cross sections are compared with the results of σ R calculations using the double-folding potential within the optical model. The energy dependence of σ R for 6He differs from that for the neighboring nuclei, which can be associated with the structural features of the former nucleus. The energy spectra of α particles produced in the 6He interactions with silicon indicate two mechanisms of their production: transfer reaction and 6He breakup in the field of the 28Si nucleus.

Fast neutron activation analysis—FNAA using d(13 MeV)+Be reaction for archaeometrical research at Bucharest cyclotron

In the last ten years the Bucharest U-120 classical variable-energy Cyclotron was employed as an intense source of fast neutrons produced by 13.5 MeV deuterons on a thick beryllium target [1], mainly for radio-biological and archaeometrical studies. To characterize this fast neutrons field, energy spectra, yields and average energy were determined using the time-of-flight (TOF) and multiple foils (activation detectors and fission chambers) methods. The potential for elemental analysis using FNAA (Fast Neutron Activation Analysis), especially for archaeological objects, is presented and illustrated with some results on coloured Byzantine glass bracelets found in Romania (receipts of pigments related to various glass elemental composition).

Improved activation tests of fusion structural materials with a deuteron–beryllium neutron source

In the framework of the European Activation File (EAF) task of the European Fusion Technology Programme, the EAF data relevant to the steel types F82H-mod and MANET-2 were benchmarked experimentally. Samples were activated in an intense neutron field produced in a thick beryllium target by a 19-MeV deuteron beam of the Karlsruhe Isochron-Zyklotron. The irradiated samples were investigated by γ spectrometry. The results were compared with calculations using the FISPACT code, the EAF-4.1 library and the source neutron spectrum as measured by activation foil dosimetry. Calculation-over-experiment ratios between 0.96 and 1.19 are found for the more important medium-halflife radionuclides produced in F82H-mod. Similar values are found for MANET-2.

Characterisation of neutron and gamma-ray emission from thick target Be(p,n) reaction for boron neutron capture therapy

Low energy accelerator-based neutron sources have promising potential for use in a clinical treatment of cancer with boron neutron capture therapy (BNCT) and boron neutron capture synovectomy (BNCS). Such sources often utilise a thick target Be(p,n) reaction using incident proton energies from several hundred keV to 1–2 MeV above the reaction threshold of 2.06 MeV. The resulting neutron and gamma-ray beams require considerable moderation and filtration in order to obtain thermal and epithermal neutron fluxes for therapy. The detailed knowledge of neutron and gamma-ray spectra, yield and angular distribution are necessary in order to design effective moderators and filters to be used for the treatment. Thick and thin beryllium target neutron and gamma-ray spectra have been investigated in detail using the time-of-flight (TOF) technique, for incident proton energies from above threshold to 4 MeV. The results show characteristics of neutron and gamma-ray production of importance for the application of this neutron source for BNCT and BNCS.

Measurements of the neutron yield and the neutron energy distribution from the 9Be(d,n) 10B reaction on a thick Be target at an incident deuteron energy of 20.2 MeV

A fast neutron irradiation facility has been set up at the SARA cyclotron located in Grenoble. This facility provides the possibility to carry out fast neutron irradiation tests at both cryogenic and ambient temperatures. Neutrons are produced by stopping a 20.2 MeV deuteron beam in a 3 mm thick beryllium target. The angular distribution of the neutron flux and the energy spectra from 0° to 40° with respect to the deuteron beam axis were measured. A neutron fluence in the range of 10 14 cm −2 is available per day, with a small gamma contamination and a small thermal neutron flux.