As a feasibility study, gas chromatography–mass spectrometry (GC–MS) and matrix-assisted laser desorption ionization–mass spectrometry (MALDI–MS) have been applied to analyze etch products of CR-39 ...plastic (one of the most frequently used solid states nuclear track detector) for the understanding of track formation and etching mechanisms by heavy ion irradiation. The etch products of irradiated CR-39 dissolved in sodium hydroxide solution (NaOH) contain radiation-induced fragments. For the GC–MS analysis, we found peaks of diethylene glycol (DEG) and a small but a definitive peak of ethylene glycol (EG) in the etch products from CR-39 irradiated by 60MeVN ion beams. The etch products of unirradiated CR-39 showed a clear peak of DEG, but no other significant peaks were found. DEG is known to be released from the CR-39 molecule as a fragment by alkaline hydrolysis reaction of the polymer. We postulate that EG was formed as a result of the breaking of the ether bond (C–O–C) of the DEG part of the CR-39 polymer by the irradiation. The mass distribution of polyallylalcohol was obtained from the etch products from irradiated and unirradiated CR-39 samples by MALDI–MS analysis. Polyallylalcohol, with the repeating mass interval of m/z=58Da (dalton) between m/z=800 and 3500, was expected to be produced from CR-39 by alkaline hydrolysis. We used IAA as a matrix to assist the ionization of organic analyte in MALDI–MS analysis and found that peaks from IAA covered mass spectrum in the lower m/z region making difficult to identify CR-39 fragment peaks which were also be seen in the same region. The mass spectrometry analysis using GC–MS and MALDI–MS will be powerful tools to investigate the radiation-induced polymeric fragments and helping to understand the track formation mechanism in CR-39 by heavy ions.
The annual effective doses of aircrew members often exceed the limit of 1 mSv for the public due to the increased level of cosmic radiation at the flight altitudes, and thus, it is recommended to ...monitor them. Aircrew dosimetry is usually performed using special computer programs mostly based on results of Monte Carlo simulations. Contemporary, detectors are used mostly for validation of these computer codes, verification of effective dose calculations and for research purposes. One of such detectors is active silicon semiconductor deposited energy spectrometer Liulin. Output quantities of measurement with the Liulin detector are the absorbed dose in silicon D and the ambient dose equivalent H*(10); to determine it, two calibrations are necessary. The purpose of this work was to develop a calibration methodology that can be used to convert signal from the detector to D independently on calibration performed at Heavy Ion Medical Accelerator facility in Chiba, Japan.
Ionizing radiation is recognized to be one of the main health concerns for humans in the space radiation environment. Estimation of space radiation effects on health requires the accurate knowledge ...of the accumulated absorbed dose, which depends on the global space radiation distribution, solar cycle and local shielding generated by the 3D mass distribution of the space vehicle. This paper presents an overview of the spectrometer–dosimeters of the Liulin type, which were developed in the late 1980s and have been in use since then. Two major measurement systems have been developed by our team. The first one is based on one silicon detector and is known as a Liulin-type deposited energy spectrometer (DES) (Dachev et al., 2002, 2003), while the second one is a dosimetric telescope (DT) with two or three silicon detectors. The Liulin-type instruments were calibrated using a number of radioactive sources and particle accelerators. The main results of the calibrations are presented in the paper. In the last section of the paper some of the most significant scientific results obtained in space and on aircraft, balloon and rocket flights since 1989 are presented.
•Different modifications of Liulin type spectrometers are presented.•The high scientific values are coming mainly from the extensive calibrations.•The data analysis procedure allows characterization of the different radiation sources.•The main advantage is their low weight, low power consumption and low cost.
A significant obstacle to long duration human space exploration such as the establishment of a permanent base on the surface of the Moon or a human mission to Mars is the risk posed by prolonged ...exposure to space radiation. In order to keep mission costs at acceptable levels while simultaneously minimizing the risk from radiation to space crew health and safety, a judicious use of optimized shielding materials will be required. We have undertaken a comprehensive study using CR-39 plastic nuclear track detector (PNTD) to characterize the radiation shielding properties of a range of materials—both common baseline materials such as Al and polyethylene, and novel multifunctional materials such as carbon composites—at heavy ion accelerators. The study consists of analyzing CR-39 PNTD exposed in front of and behind shielding targets of varying composition and at a number of depths (target thicknesses) relevant to the development and testing of materials for space radiation shielding. Most targets consist of 10
cm
×
10
cm slabs of solid materials ranging in thickness from 1 to >30
g/cm
2. Exposures have been made to beams of C, O, Ne, Si, Ar, and Fe at energies ranging from 290 MeV/amu to 1 GeV/amu at the National Institute of Radiological Sciences HIMAC and the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory. Analysis of the exposed detectors yields LET spectrum, dose, and dose equivalent as functions of target depth and composition, and incident heavy ion charge, energy, and fluence. Efforts are currently underway to properly weigh and combine these results into a single quantitative estimate of a material's ability to shield space crews from the interplanetary galactic cosmic ray flux.
In this paper, we present the measurement of the energy spectra of carbon and oxygen in cosmic rays based on observations with the Calorimetric Electron Telescope on the International Space Station ...from October 2015 to October 2019. Analysis, including the detailed assessment of systematic uncertainties, and results are reported. The energy spectra are measured in kinetic energy per nucleon from 10 GeV/n to 2.2 TeV/n with an all-calorimetric instrument with a total thickness corresponding to 1.3 nuclear interaction length. The observed carbon and oxygen fluxes show a spectral index change of ∼0.15 around 200 GeV/n established with a significance > 3σ. They have the same energy dependence with a constant C/O flux ratio 0.911 ± 0.006 above 25 GeV/n. The spectral hardening is consistent with that measured by AMS-02, but the absolute normalization of the flux is about 27% lower, though in agreement with observations from previous experiments including the PAMELA spectrometer and the calorimetric balloon-borne experiment CREAM.
Cosmic radiation represents possible risk for the astronauts. For estimation of the radiation onboard the spacecraft in space flights, it is necessary to obtain the data on dose distribution in real ...space flight conditions. This contribution deals with the study of absorbed dose and dose equivalent due to space radiation in different compartments of the International Space Station (ISS) using passive detectors. Luminescent detectors (LD) and CR-39 plastic nuclear track detectors (PNTD) were exposed onboard of Russian Service Module on ISS from August 2004 to October 2005 (425
days); they were placed at SPD boxes and positioned at 6 various locations inside the Russian Service Module. LD were used to measure absorbed doses, particularly from low-LET particles and photons, PNTDs were used to measure the spectra of linear energy transfer (LET), absorbed dose, and dose equivalents from particles with LET
∞H
2O >5
keV/μm. Results from both types of detectors (LD and PNTD) were then combined together to obtain total values of absorbed doses and dose equivalents. Distribution of absorbed doses and dose equivalents measured with passive detectors, as well as LET spectra of registered particle fluxes, are presented as the function of position of SPD boxes (shielding thickness). Also the influence of position of detectors inside the SPD boxes (top and bottom wall) will be discussed. The dose characteristics depend on the location inside the Service Module; their variation has been observed to be up to factor of almost 2.
We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 yr period by ...the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20degrees radius circles. The hotspot has a Li-Ma statistical significance of 5.1sigma, and is centered at R.A. = 146degrees.7, decl. = 43degrees.2. The position of the hotspot is about 19degrees off of the supergalactic plane. The probability of a cluster of events of 5.1sigma significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7 x 10 super(-4) (3.4sigma).
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