Counter Telescope Research Articles

Double-differential cross sections for charged particle emissions from α particle impinging on Al at 230 MeV/u

ABSTRACT Charged particle production from α particle fragmentation reactions was investigated experimentally by measurement of 230-MeV/u α particles bombarding an aluminum target. Double differential cross sections were measured for each ejectile of p, d, t, 3He, and 4He using counter telescopes composed of Si surface barrier detectors and crystal scintillators, which were located at laboratory angles between 15° and 60°. The obtained data were analyzed for comparison with data observed at lower incident energies. The results found the following common characteristics: (1) spectra of proton- and neutron-emission are similar in high energy region at forward angle, (2) triton-to-3He ratio of α-breakup yield is 1:2, which is similar to lower incident energy experiment, and (3) the shape of broad peak formed by 3He and α particles could be explained by the process with collision between induced α particle and target nucleus.

Emissions of Hydrogen Isotopes from the Nuclear Muon Capture Reaction in natSi

The energy spectra of protons, deuterons and tritons produced by the nuclear muon capture reaction in natSi were measured at the M1 beam line of Muon Science Innovative Channel (MuSIC) in Research Center for Nuclear Physics (RCNP) using a counter telescope consisting of a Si detector and a CsI(Tl) scintillation detector. The measured energy spectra were consistent with the previous ones. The experimental energy spectra were compared with theoretical model calculations using the Particle and Heavy Ion Transport code System (PHITS). In PHITS, both the dynamical and statistical processes in the nuclear muon capture reaction are described by the Quantum Molecular Dynamics (QMD) or the modified QMD and the Generalized Evaporation Model (GEM), respectively. The PHITS simulation reproduced generally well the measured proton spectrum at emission energies below 20 MeV, while underestimation was seen at emission energies above 20 MeV. The PHITS simulation underestimates remarkably the measured energy spectra of light complex particles (deuterons, tritons, and alpha particles) in the high energy region.

Performance Study of a Time-of-Flight Method Used for Cosmic Ray Detection

Time of Flight methods have been rapidly developed and used in many experiments recently for determination of particle direction, identification of particles and energy resolutions. This paper describes a method of time-mark determination on the reconstruction algorithm, based on the sampled signal, used for time-of-flight measurements. This method was developed for distinguishing the signals by fitting to pulse shape which were received from scintillator detector with a silicon photomultiplier readout have been developed for a cosmic ray counter telescope. The method was verified using experimental data taken in the location $40^{o}54'52"N$ and $38^{o}19'26"E$ with the elevation of 30 m above the sea level. The data samples were acquired by the counters which have a scintillator with dimensions of 20$\times$20$\times1.4~cm^3$, optically coupled from one side to silicon photomultiplier, then the signals readout by fast sampling digitizer board Domino Ring Sampler Board version 4. The method can reconstruct each pulse even for multiple events without losing the count within the small time window. Using this method 4.969 ns time-of-flight value were established and the rise times for scintillation counters, named Tile 1 and Tile 2, were measured about $6.27 \pm 0.16~ns$ and $4.979\pm0.165~ns$, respectively.

Temperature Effect Observed for the Muon Component in the Yakutsk Cosmic-Ray Spectrograph

The temperature effect is studied for the muon detectors of the Yakutsk cosmic-ray spectrograph, which consists of an ionization chamber and ground-level and undergroundmuon counter telescope deployed at depths of 0, 7, 20, 40, and 60 mwe. This array makes it possible to study muon fluxes over a wide energy range (from 2 to 200 GeV). The dependence of the temperature effect for muon component on the depth and on the zenith angle (that is, on the energy of detected particles, as well as on the solar-activity cycle) is studied. A brief description of the muon detector database (mddb) created at IZMIRAN is given. This database includes observational data from muon detectors and data on the atmospheric pressure and vertical profiles of the atmospheric temperature at standard isobaric levels.

Light ion production in 175 MeV quasi mono-energetic neutron induced reactions on carbon, oxygen, and silicon

Double-differential cross sections of light ions (p, d, t, 3 He, and α) from carbon, oxygen, and silicon induced by 175 MeV quasi mono-energetic neutrons were measured using the Medley setup at the The Svedberg Laboratory (TSL) in order to benchmark evaluated nuclear data and nuclear reaction models. The Medley is a conventional spectrometer system which consists of eight counter telescopes. Each telescope is composed of two silicon surface barrier detectors as the ΔE detectors and a CsI(Tl) scintillator as the E detector for particle identification. The telescopes are placed at angles from 20° to 160° in steps of 20°. The measured double-differential production cross sections of light ions for oxygen and silicon are compared with PHITS calculations using the following nuclear reaction options: the high-energy nuclear data library (JENDL/HE-2007), the quantum molecular dynamics (QMD) model, the modified quantum molecular dynamics (MQMD) model, and the intra-nuclear cascade (INC) model based on the Bertini Model.

Development of the Quasi-monoenergetic Neutron Calibration Fields of Several Tens of MeV at TIARA

Development of three calibration fields for 45, 60 and 75 MeV neutrons has been in progress at Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) of JAEA-Takasaki. Achievement of the neutron calibration fields requires establishment of both measurement of neutron fluence and its monitoring technique. In order to measure the neutron fluence of main energy peak especially at a reference point on low fluence condition, a proton recoil counter telescope with high efficiency has been developed. The design of relatively large telescope components brought a high detection efficiency at the reference point with wide irradiation area at a long distance. Effective and precise measurement of the neutron fluence could be performed with uncertainties less than 6.5 % (standard deviation). For detecting neutrons without scattering near the target, a transmission type neutron fluence monitor has been newly developed to measure the neutron fluence directly at the collimator exit. Its performance such as counting rates was tested for various beam intensities.

Development of highly efficient proton recoil counter telescope for absolute measurement of neutron fluences in quasi-monoenergetic neutron calibration fields of high energy

Precise calibration of monitors and dosimeters for use with high energy neutrons necessitates reliable and accurate neutron fluences being evaluated with use of a reference point. A highly efficient Proton Recoil counter Telescope (PRT) to make absolute measurements with use of a reference point was developed to evaluate neutron fluences in quasi-monoenergetic neutron fields. The relatively large design of the PRT componentry and relatively thick, approximately 2 mm, polyethylene converter contributed to high detection efficiency at the reference point over a large irradiation area at a long distance from the target. The polyethylene converter thickness was adjusted to maintain the same carbon density per unit area as the graphite converter for easy background subtraction. The high detection efficiency and thickness adjustment resulted in efficient absolute measurements being made of the neutron fluences of sufficient statistical precision over a short period of time. The neutron detection efficiencies of the PRT were evaluated using MCNPX code at 2.61×10 −6, 2.16×10 −6 and 1.14×10 −6 for the respective neutron peak energies of 45, 60 and 75 MeV. The neutron fluences were determined to have been evaluated at an uncertainty of within 6.5% using analysis of measured data and the detection efficiencies. The PRT was also designed so as to be capable of simultaneously obtaining TOF data. The TOF data also increased the reliability of neutron fluence measurements and provided useful information for use in interpreting the source of proton events.

Multi-elemental characterization of organic liquid samples by use of a 13 MeV 6Li 3+ beam

Evaporated amniotic fluid (AF) targets have been bombarded with a 13 MeV 6Li 3+ beam. Forward angle data have served to identify the 1H( 6Li, 1H) 6Li reaction as an alternative for hydrogen characterization of such organic samples. Detected 6Li ions elastically scattered from C, N, O, Na and Cl can also be used to determine the concentrations of these elements in AF. The analyzed AF samples have been diluted with distilled water. The effect of sample dilution on the improvement of spectrum energy resolution has been observed, confirming previous reports. The hydrogen concentration determined in the studied AF targets is shown to vary linearly with sample dilution. Two detector arrangements have been used to find out which detection scheme is the most convenient. The combination of a counter telescope and a single detector, set up at the same polar angle on the opposite side of the beam, seems to be the best choice to have a reliable particle identification and an adequate energy resolution simultaneously.

Levels in 13N examined by 12C+p elastic resonance scattering with thick target**Supported by National Natural Science Foundation of China (10445004, 10575136, 10735100) and Major State Basic Research Development Program (2007CB815003)

The elastic resonance scattering of 12C+p has been studied in inverse kinematics via a novel thick target method at GIRAFFE facility of HI-13 tandem accelerator laboratory, Beijing. The recoil protons were measured by a ΔE-E counter telescope based on a large area double-sided silicon strip detector at laboratory angles around θ0 = 15°. The excitation function for 12C(p,p) elastic scattering has been obtained over a wide energy range of Ec.m.=0.31–3.45 MeV, which was explained quite well by the R-matrix calculation with known resonance parameters of the first three levels in 13N nucleus. Thus it is demonstrated that the present setup can be directly applied to the study of elastic resonance scattering with secondary radioactive beams.

N13+pelastic resonance scattering via a thick-target method

The {sup 13}N+p elastic resonance scattering has been studied in inverse kinematics via a thick-target method. A {sup 13}N secondary beam of 47.8{+-}1.5 MeV produced by the {sup 2}H({sup 12}C,{sup 13}N)n reaction was used to bombard a 9.33 mg/cm{sup 2} (CH{sub 2}){sub n} target. The recoil protons were detected by a {delta}E-E silicon counter telescope at {theta}{sub lab}=15 deg. The performance of the setup was checked by {sup 12}C+p elastic resonance scattering with the same (CH{sub 2}){sub n} target. The excitation function for the {sup 13}N(p,p) elastic scattering was obtained in the energy interval of E{sub c.m.}{approx}0.5-3.2 MeV and was analyzed by using a multilevel R-matrix code MULTI7. Several low-lying excited states in {sup 14}O were surveyed. Our results confirm a very recent 2{sup -} assignment to the 6.8 MeV level and agree with the observation of a new 0{sup -} level at 5.7 MeV with a width of 400(45) keV.

Differential cross sections of neutron-induced fragment-emission reactions for a microdosimetry study

Experimental differential cross sections of fragment emission (p, d, t, alpha, Li, Be and B), which were obtained for tens of mega electron volt neutrons on carbon and aluminum, using a counter telescope array and a Bragg-curve counter specially developed for neutron-induced reactions, are presented and compared with theoretical calculations using various reaction models. A calculation with the ISOBAR and GEM models was found to reproduce the experimental data except for an underestimation in non-vaporation processes. Calculations of the energy deposition by neutrons in a thin silicon layer show significant differences among the model employed.

Energy dependence of proton induced fission cross sections for heavy nuclei in the energy range 200–1000 MeV

Total cross sections for proton induced fission of ${}^{\mathrm{nat}}\mathrm{Pb}$, $^{209}\mathrm{Bi}$, $^{232}\mathrm{Th}$, $^{233}\mathrm{U}$, $^{235}\mathrm{U}$, $^{238}\mathrm{U}$, $^{237}\mathrm{Np}$, and $^{239}\mathrm{Pu}$ nuclei were measured in the range 200--1000 MeV with an energy step of 100 MeV. The experiment was carried out at 1 GeV in a PNPI synchrocyclotron. Complementary fragments of the binary fission from a thin target were detected in coincidence by two parallel plate avalanche counters (PPAC) located close to the target. An assembly of the two PPACs and with the target in between them was placed directly into the beam, which provided a large solid angle acceptance. The beam monitoring system employed a scintillation counter telescope that was used for direct proton counting as well as for registration of the elastic $\mathit{pp}$-scattering events from the auxiliary (${\mathrm{CH}}_{2}){}_{n}$ target. The measured energy dependence of the total fission cross sections is presented. The results are compared with other available experimental data as well as with calculations in the frame of the cascade-evaporation model.

Charged-particle spectrometry using a pencil-beam DT neutron source for double-differential cross-section measurement

Measurement of double-differential cross-sections of charged-particle emission induced by 14 MeV neutrons is quite important for estimating the nuclear heating and material damage of a fusion reactor. However, there are few experimental data available in spite of the importance of the nuclear reactions of light nuclei in fusion reactor development. In order to accurately measure differential cross-sections, especially of light nuclei, we propose a refined spectrometry system and a data processing method. The employment of a pencil-beam neutron source overcomes the fundamental difficulty of the measurement. As a result, a system with a counter telescope consisting of silicon surface barrier detectors satisfies high energy resolution and angular resolution, a wide detection energy range and adequate particle discrimination. To correct the energy loss of the emitted charged particles in the sample, a rigorous correction method by means of the unfolding procedure is applied. The validity and the capability of this spectrometry technique are confirmed from three basic measurements: the measurements of charged particles emitted from Teflon, α-particles emitted from the 27Al( n, xα) reaction and the protons recoiling from the 1H( n, n) reaction. This technique can be applied to the detailed DDXc measurements of various materials, especially of lighter materials, for fusion reactor modeling.

The experimental investigation of the neutron energy response of the thin ST-401 scintillator

Using the 5SDH-2 Accelerator at the Radiation Metrology Center of CIAE, the experiment of neutron energy response of the thin ST-401 scintillator has been performed. Two T(p,n)3 He and D(d,n)3He reactions are chosen for generating the neutrons. The neutron beam is collimated with the multiplex shielding system. The source intensity is monitored by the proportional counter or semiconductor proton recoil telescope. The neutron response curves of ST-401 scintillators with thickness from 0.16mm to 2.00mm are measured versus neutron energy. The uncertainties of experimental results are discussed in detail. The results show that the sensitivity increases with the scintillator thickness, and for the same thickness, the slope of energy response curve does not change greatly with the increase of neutron energy.

High energy X-ray observations of NGC 5506

We have a continuing programme of spectral and temporal studies of a variety of galactic and extragalactic sources in the 20–200 keV band using a large area scintillation counter telescope. The observations of NGC 5506, a Seyfert type 2 galaxy, taken on three occasions during the 1998–2000 period suggest that not only source luminosity varies by a factor of ∼10, but also there is a marked change in the spectral index. The data is consistent with a systematic long-term periodic variation. Our analysis of the all sky monitor light curve suggests a 41.12-day period in the source intensity. This paper presents the spectral parameters in the hard X-ray region and proposes that the observed behaviour of the source can be explained on the basis of a binary black hole model for the core activity of the source.

Search for Enhanced D+D+D Reactions under D<sup>+</sup> Beam Irradiation into TiDx Targets

To search possible enhancement of three-body D+D+D fusion reaction in condensed matter, we have studied for 10 years about emitted charged particle spectra from titanium-deuterate (TiDx) samples under low energy D+ beam irradiation. By gas loading technique with changing temperature, we prepared TiDx samples with x = 1.4 - 1.8. A TiDx sample was mounted in a vacuum chamber with cooling and irradiated with 70 – 300 keV D+ beam. A delta-E and E type counter telescope using two Si-SSD detectors was used for charged particle spectroscopy. Charged particles from D+D fusion reactions, e.g., 3MeV protons and 1MeV tritons were observed in every case, as usually expected. Sometimes, in addition, we observed “unknown” peaks at about 4.8MeV, which were identified to be two kinds of particles, i.e., helium and triton. We could not find any candidate reaction channels in two-body nuclear reactions of D+ beam and possible target nuclei (H, D, T, He-3, Li-6, Li-7, Be-9, C-12, N-14, N-15, Ti, etc.) including impurity reactions. We concluded that the 4.8MeV particles were from the D+D+D fusion to the out-going reaction channel of He-3 (4.75MeV) + T(4.75MeV). The yield ratios of [3D]/[2D] were obtained as a function of D+ beam energy in the range of 50 to 300 keV, revealed the increasing trend in the lower energy range than 100 keV and were on the order of 1E-4 which was anomalously large compared with the estimated values on the order of 1E- 30 based on the conventional random nuclear process for the cascade reactions of three-body interaction, i.e, D+D to He-4* and He-4* + D reactions.

Spatial fragment distribution from a therapeutic pencil-like carbon beam in water

The latest heavy ion therapy tends to require information about the spatial distribution of the quality of radiation in a patient's body in order to make the best use of any potential advantage of swift heavy ions for the therapeutic treatment of a tumour. The deflection of incident particles is described well by Molière's multiple-scattering theory of primary particles; however, the deflection of projectile fragments is not yet thoroughly understood. This paper reports on our investigation of the spatial distribution of fragments produced from a therapeutic carbon beam through nuclear reactions in thick water. A ΔE–E counter telescope system, composed of a plastic scintillator, a gas-flow proportional counter and a BGO scintillator, was rotated around a water target in order to measure the spatial distribution of the radiation quality. The results revealed that the observed deflection of fragment particles exceeded the multiple scattering effect estimated by Molière's theory. However, the difference can be sufficiently accounted for by considering one term involved in the multiple-scattering formula; this term corresponds to a lateral ‘kick’ at the point of production of the fragment. This kick is successfully explained as a transfer of the intra-nucleus Fermi momentum of a projectile to the fragment; the extent of the kick obeys the expectation derived from the Goldhaber model.

Modified method for registration of particle deflection by a bent crystal

A modified method for registration of particle deflection by a bent crystal was proposed and studied at the external proton beam of the Nuclotron. A telescope of scintillation counters was placed at an angle that was smaller than the crystal bending angle. The count dependence of the telescope on the crystal orientation was formed by the particles, which passed in channeling states only some part of the crystal length. Two maximums were observed in the dependencies due to particles captured into the channeling states at the crystal surface and in the crystal volume. This allows to receive, using the telescope and high-intensity beams, a useful data about the particle channeling and the crystal what usually demands more complicated registration by means of coordinate detectors. The proposed method can be useful for the investigation of particle deflection by the crystals, in which the particle channeling length is small because of some lattice defects.

Measurement of differential cross sections for evaluation of radiation dose of ten’s of MeV neutrons

Double differential cross sections of several ten’s of MeV neutron induced reactions for elements composing the human tissue were measured using specially designed spectrometers at TIARA 7Li(p,n) neutron source. In spectroscopy of particles from neutron induced reactions, a large solid angle and particle acceptance detector is indespensable. For particles from 5 MeV a to 70 MeV proton, a spectrometer consisting of three counter telescopes and a vacuum chamber was used. For heavier particles, a Bragg curve spectroscopy technique was adopted to neutron field. Double differential cross section of p,d,t,a emission for N and O were obtained using the former spectrometer. In the later method we fabricated a test spectrometer to check applicability and signal to noise ratio in neutron field. Using the spectrometer, energy spectra of heavier particles (Li, Be, B, C) from carbon were observed.

Influence of fragment reaction of relativistic heavy charged particles on heavy-ion radiotherapy

The production of projectile fragments is one of the most important, but not yet perfectly understood, problems to be considered when planning for the utilization of high-energy heavy charged particles for radiotherapy. This paper reports our investigation of the fragments' fluence and linear energy transfer (LET) spectra produced from various incident ions using an experimental approach to reveal these physical qualities of the beams. Polymethyl methacrylate, as a substitute for the human body, was used as a target. A ΔE–E counter telescope with a plastic scintillator and a BGO scintillator made it possible to identify the species of fragments based on differences of various elements. By combining a gas-flow proportional counter with a counter telescope system, LET spectra as well as fluence spectra of the fragments were derived for each element down from the primary particles to hydrogen. Among them, the information on hydrogen and helium fragments was derived for the first time. The result revealed that the number of light fragments, such as hydrogen and helium, became larger than the number of primaries in the vicinity of the range end. However, the greater part of the dose delivered to a cell was still governed by the primaries. The calculated result of a simulation used for heavy-ion radiotherapy indicated room for improving the reaction model.