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The ICCHIBAN-2 experiment, the first dedicated to the ground-based intercomparison of passive space dosemeters, was carried out between 23 May and 28 May 2002 at the National Institute of Radiological Sciences in Chiba, Japan. The primary objective of the ICCHIBAN-2 experiment was to intercompare the response of passive dosemeters used in space crew dosimetry to monoenergetic heavy ions of charge and energy spanning a significant portion of the galactic cosmic ray (GCR) spectrum. During the ICCHIBAN-2 experiment, dosemeters from 12 different laboratories in 9 countries were irradiated under identical conditions to heavy ion beams of 150 MeV n(-1) (4)He, 400 MeV n(-1) (12)C, 490 MeV n(-1) (28)Si and 500 MeV n(-1) (56)Fe at the NIRS Heavy Ion Medical Accelerator.

To investigate effects of low dose heavy particle radiation to CNS system, we adopted mouse neonatal brain cells in culture being exposed to heavy ions by HIMAC at NIRS and NSRL at BNL. The applied dose varied from 0.05 Gy up to 2.0 Gy. The subsequent biological effects were evaluated by an induction of apoptosis and neuron survival focusing on the dependencies of the animal strains, SCID, B6, B6C3F1, C3H, used for brain cell culture, SCID was the most sensitive and C3H the least sensitive to particle radiation as evaluated by 10% apoptotic criterion. The LET dependency was compared with using SCID and B6 cells exposing to different ions (H, C, Ne, Si, Ar, and Fe). Although no detectable LET dependency was observed in the high LET (55-200 keV/micrometers) and low dose (<0.5 Gy) regions. The survivability profiles of the neurons were different in the mouse strains and ions. In this report, a result of memory and learning function to adult mice after whole-body and brain local irradiation at carbon ion and iron ion.

Eker rat known as a model of hereditary renal carcinoma (RC) is an example of Mendelian dominantly inherited predisposition to a specific cancer in experimental animals. We investigate the effects of simulated space radiation on carcinogenesis using HIMAC. We estimated RBE from the Eker rats exposed to the heavy-ions, C (290 MeV/u) and Fe (500 MeV/u) ions, comparing to the effects of X-ray irradiation. Pregnant rats were exposed to C and Fe ions and X-rays with a single dose of 1 Gy, 2 Gy, 3 Gy on day 19 of gestation. The offspring were sacrificed at 8 weeks of age. We evaluated organ weights and tumor genesis. The weights of thymus, lung, liver, spleen were found to be no difference from the control at 1 Gy irradiation but 50% decrease at 3 Gy irradiation. We found in the irradiated animal that kidney, brain and testis were very sensitive organs of which the weight decreased to approximately 80% at 1 Gy and to 40% at 3 Gy irradiations. Based on the dose-response relationship of the radiation-induced carcinoma, averaged RBE ware calculated to be 1.1 for C-ion, 1.6 for Fe-ion.

The relative electron density resolution was discussed by the Wiener spectrum in the heavy ion CT image. The two-dimensional (2D) Wiener spectrum in the CT image was obtained from the one-dimensional (1D) Wiener spectrum of the measured residual range distribution of the water phantom for a single projection angle, and the relative electron density resolution in the CT image was calculated from the 2D Wiener spectrum. To examine the usefulness of this method, the relative electron density resolution was also estimated by other two methods; the calculation using the Wiener spectrum of the reconstructed image of the water phantom, and the estimation by the reconstructed image of the electron density resolution phantom. The result of the first method was similar to those of the other two methods. Therefore, it is useful to estimate the relative electron density resolution by the 1D Wiener spectrum of the measured residual range distribution of the water phantom for a single projection angle.

Computer code calculations based on biophysical models are commonly used to evaluate the effectiveness of shielding in reducing the biological damage caused by cosmic radiation in space flights. Biological measurements are urgently needed to benchmark the codes. We have measured the induction of chromosomal aberrations in human peripheral blood lymphocytes exposed in vitro to 56Fe-ion beams accelerated at the HIMAC synchrotron in Chiba. Isolated lymphocytes were exposed to the 500 MeV/n iron beam (dose range 0.1-1 Gy) after traversal of 0 to 8 g/cm2 of either PMMA (lucite, a common plastic material) or aluminum. Three PMMA shield thickness and one Al shield thickness were used. For comparison, cells were exposed to 200 MeV/n iron ions and to X-rays. Chromosomes were prematurely condensed by a phosphatase inhibitor (calyculin A) to avoid cell-cycle selection produced by the exposure to high-LET heavy ion beams. Aberrations were scored in chromosomes 1, 2, and 4 following fluorescence in situ hybridization. The yield of chromosomal aberrations per unit dose at the sample position was poorly dependent on the shield thickness and material. However, the yield of aberrations per unit ion incident on the shield was increased by the shielding. This increase is associated to the increased dose-rate measured behind the shield as compared to the direct beam. These preliminary results prove that shielding can increase the effectiveness of heavy ions, and the damage is dependent upon shield thickness and material.

Abstract: We studied the track response of CR-39 plastic nuclear track detectors (PNTD) for low (<6 MeV/n) and high (>100 MeV/n) energy heavy ions using the atomic force microscope (AFM). CR-39 PNTD was exposed to several heavy ion beams of different energy at HIMAC (Heavy Ion Medical Accelerator in Chiba). For AFM measurement, the amount of bulk etch was controlled to be ∼2 μm in order to avoid etching away of short range tracks. The response data obtained by AFM for ∼2 μm bulk etch was in good agreement with data obtained by the conventional optical microscope analysis for larger bulk etch. The response data from low energy beams (stopping near the surface) was also consistent with the data from high energy beams (penetrating the detector) as a function of REL (restricted energy loss) with the δ-ray cut off energy of ω 0 = 200 eV. We experimentally verified that REL (ω 0 = 200 eV) gives a universal function for wide energy range in CR-39 PNTD. This work has been done as part of a basic study in the measurement of secondary short range tracks produced by target fragmentation reactions in proton cancer therapy fields. [Copyright &y& Elsevier]

Abstract: The two-step etching method using PEW (Potassium hydroxide + Ethanol + Water) and NaOH solutions was applied to the control of the response of CR-39 plastic nuclear track detectors for the measurement of high LET (linear energy transfer) particles. CR-39 detectors were exposed to several heavy ion beams covering the LET∞H2O range of 30–750 keV/μm from HIMAC (Heavy Ion Medical Accelerator in Chiba) at NIRS (National Institute of Radiological Sciences), Japan. The detectors were pre-etched in PEW solutions with 3 different ethanol concentrations at the temperature of 70 °C for 30–60 min. Then, the detectors were post-etched in 7N NaOH solution at the same temperature for 4–28 h. We found that the response curves and the detection thresholds of the detectors smoothly shifted to higher LET regions as the ethanol concentration increases in PEW solution. [Copyright &y& Elsevier]

Gas electron multipliers with a liquid crystal polymer insulator (LCP-GEMs) can be employed as X-ray polarimeters in several satellite missions in low-earth orbit. To evaluate their resistance to radiation, LCP-GEMs were exposed to Fe ion and proton beams from the heavy-ion accelerator facility HIMAC, and the gas gain was monitored. The LCP-GEMs survived 14.4-year-equivalent irradiation by fully stripped Fe ions with an energy of 500 MeV\ nuc^-1, which simulated galactic cosmic-ray ions. We also studied the degradation of the insulator layer of the LCP-GEMs by irradiation with 160 MeV protons to simulate geomagnetically trapped protons. After irradiation with protons for 31.6 years equivalent, no significant change in gain was observed. [ABSTRACT FROM AUTHOR]

Abstract: The charge resolution (δZ) for heavy ions (nuclear charge: Z <40) of 0.1–1GeV/n energy in CR-39 plastic nuclear track detector (PNTD) and its dependence on etching time, and on projectile Z and energy were investigated and optimized as part of an effort to make precise measurements of projectile charge-changing cross sections. Two types of CR-39 PNTD, HARZLAS TD-1 and BARYOTRAK, were exposed to heavy ion beams with seven values of Z behind thick targets to produce projectile fragments. Following chemical etching (7N NaOH at 70°C) for varying etch times, δZ of the projectiles was determined for each detector type. A strong dependence of δZ on the amount of bulk etch (B) was seen. It was also observed that δZ can be remarkably improved with longer etching time as a function of B −1/2, in accordance with the trend seen in other types of track detector such as glass nuclear track detector. However, for B ⩾60μm (30h etching), saturation occurs and there is no further improvement in δZ. Analysis of the correlations between projectile Z, energy, detector response, and fluctuation of the response make it possible to develop a model to predict the δZ for projectiles of given Z and energy. The predicted and measured values of δZ show good agreement within 10%. We conclude that 4⩽ Z ⩽30 at intermediate energy can be identified with good δZ in these detectors. The predictive model will be used in designing future cross section measurement experiments. [Copyright &y& Elsevier]

We report experimental results from a heavy ion CT system based on the measurement of residual range distribution using an X-ray intensifying screen and a charged coupled device (CCD) camera system. This technique was first investigated by Zygmanski et al. (2000) for proton beams, and they reported that the spatial resolution was significantly degraded by multiple Coulomb scattering (MCS) effects in the irradiated medium. Experiments were done on the spatial resolution phantom by using helium and carbon beams accelerated up to 120 MeV/u and 230 MeV/u by the Heavy Ion Medical Accelerator in Chiba (HIMAC), installed in the National Institute of Radiological Sciences (NIRS) in Japan, using a high performance intensified CCD (ICCD) camera. We show that the MCS blurring effect can be significantly reduced in the reconstructed image by using a carbon beam with this technique. Our results suggest that heavier particles such as carbon would be more useful if this technique is envisioned as a clinical tool to obtain data that would aid proton and/or heavy ion treatment planning. [ABSTRACT FROM AUTHOR]

Abstract: We verified the angular dependence of track registration sensitivity for four types of CR-39 plastic nuclear track detectors using heavy ion beams. These detectors have been launched with several types of luminescence detectors on the Russian segment of the International Space Station (ISS) to intercompare passive radiation dosimeter components from several institutions. CR-39 detectors were irradiated by several kinds of heavy ions with several hundred MeV/n. All the etched tracks were analyzed using a high-speed microscope (HSP-1000) with ellipse fitting software (PitFit). Reduction of sensitivity was observed near the region of the critical angle. Corrections were made using an empirical method based on the known structure of the galactic cosmic ray spectrum. [Copyright &y& Elsevier]

This paper is focused on the improvement of the heavy charge particle charge resolution of Fluorescent Nuclear Track Detector (FNTD) technology. Fluorescent intensity of individual heavy charge particle tracks is used to construct the spectrum. Sources of spectroscopic line broadening were investigated and several fluorescent intensity correction procedures were introduced to improve the charge resolution down to δZ = 0.25 c.u. and enable FNTD technology to distinguish between all projectile fragments of 290 MeV carbon ions. The benefits of using FNTD technology for fragmentation study include large dynamic range and wide angular acceptance. While we describe these developments in the context of fragmentation studies, the same techniques are readily extended to FNTD LET spectroscopy in general. [ABSTRACT FROM AUTHOR]

Abstract: N-4 stacks of nuclear emulsion were exposed to 500AMeV 56Fe ions at the HIMAC NIRS. Particle production was investigated in 56Fe–Em interactions. The multiplicity distribution of projectile fragments was done in this paper and compared with interactions induced by 56Fe and other heavy ions in nuclear emulsion at other energies. The variation of characteristics of the heavy ion interactions with the mass and energy of the projectile is studied. [Copyright &y& Elsevier]

Abstract: Measurements of fragment emission angles for 57 and 93 MeV/nucleon 12C and 95 MeV/nucleon 16O projectiles in graphite, Plexiglas and polyethylene targets were performed using trajectory tracing technique with CR-39 detectors. The results were compared with calculations with the fragment emission angle model (FRANG). The angular resolution of the measurements was achieved to be <0.1°. The measured fragment emission angles imply that the generally accepted straight-ahead approximation of fragment emissions in nuclear collisions is oversimplified as the fragments are clearly emitted at different angles related to the primary particles. The calculated values were in agreement with the experimental ones within the margin of a few degrees for most of the examined projectile-target systems. However, some discrepancies were observed. Thus a new calculation was performed with a modified version of the model M-FRANG. For both FRANG and M-FRANG, chai-square values were calculated to test the degree of agreement with our measurements. It was confirmed that the M-FRANG showed better agreement despite its simplicity, and it was established it can be successfully used in several applications, including simple and fast test of more complicated 3D particle and heavy ion transport codes. [Copyright &y& Elsevier]

Abstract: A new method to trace heavy ion trajectories in a stack consisting of interleaved CR-39 plastic nuclear track detectors and target material layers was developed and tested for use in the measurement of projectile charge changing cross-sections of heavy ion fragmentation reactions. A high speed imaging microscope with sophisticated track analysis software was utilized to extract the charge information from multiple ion tracks belonging to a single fragmentation event. The systematic error of trajectory tracing was verified for the measurement system. In order to verify the validity of system, the projectile total charge changing cross-sections for Fe ions on carbon target was estimated and compared with previous experiments at initial beam energy of 1GeV/n. The result is in good agreement with results obtained by other investigators. This method allows precise and fast measurement of the projectile charge changing cross-section with higher statistics on a level compatible to that of silicon spectrometer measurements. [Copyright &y& Elsevier]

Abstract: Mixtures of allyl diglycol carbonate (CR-39) and diallyl phthalate (DAP) were cast into resin plates under same polymerizing conditions. The copolymer plates were irradiated with many kinds of ions at the medium energy beam irradiation room or biological irradiation room of National Institute of Radiological Sciences (NIRS)-Heavy Ion Medical Accelerator in Chiba (HIMAC). After etching in an aqueous solution of KOH, whether enlarged ion tracks exist or not was determined by using an optical microscope. It was found that every plate has a characteristic value in LET as threshold for track formation. The threshold increases with the concentration of DAP. It has been shown that the threshold is adjustable by changing the ratio of CR-39 and DAP. It is expected that the copolymers can be used for the discrimination of heavy ions in cosmic rays. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: A PAssive Dosimeter for Life-science Experiments in Space (PADLES) has been developed for measuring total absorbed dose and dose equivalents in the radiation environments of the International Space Station (ISS) where the Linear Energy Transfer (LET) of radiation ranges from 0.2 (ionization minimum) to 103 keVμm−1 or more. PADLES consists of two types of passive and integrating radiation detectors: MSO-S (Mg2SiO4:Tb) ThermoLuminescence Dosimeters (TLDs) and antioxidant-doped CR-39 plastic nuclear track detectors. In this paper, we first describe a method to obtain a water-equivalent absorbed dose by combining data from these two types of detector. In order to increase the reliability of PADLES for ISS space radiation dosimetry, we investigated the following characteristics of MSO-S TLDs: calibration of our ThermoLuminescence (TL) readout system for high-energy protons and gamma rays from 60Co and 137Cs sources; dose responses for high-energy heavy ions (He, C, Si, Ar, Fe); response variation of different manufacture batches; directional response for the high-energy protons; the initial variations and long-term fading effects of the TL response for high-energy protons and heavy ions at temperatures from −80 °C to 60 °C; and LET response. [Copyright &y& Elsevier]

Abstract: Total charge-changing cross sections and cross sections for the production of projectile-like fragments were determined for fragmentation reactions induced by 370MeV/n 20Ne ions in water and lucite, and 490MeV/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. [Copyright &y& Elsevier]

Abstract: In radiation cancer therapies using energetic charged particles such as proton/heavy-ion therapy and boron neutron capture therapy (BNCT), studies on radiation-induced biological response at cellular level are important because the radiation damage from energetic charged particles is highly localized along their paths and the radiation sensitivity is quite different in each cellular organelle. In such studies the information on the position of charged particle impact in biological cells is necessary. A novel method for high-resolution nuclear track mapping in detailed cellular histology has been developed. In this technique, biological specimens mounted on CR-39 plates are exposed to energetic charged particles. The irradiated samples are exposed to UV, and then etched for a short time. Both etch pits of nuclear tracks and relief for transmission UV image of the specimen can be observed on the CR-39 surface with an atomic force microscope (AFM) at about 100nm resolution. [Copyright &y& Elsevier]

Abstract: Calculations on the formation of a linear track of a heavy ion in bubble detector have been carried out based on a theoretical model considering the minimum energy (including bubble surface energy, internal energy, evaporation energy, expansion energy, kinetic energy and viscous energy) required during the formation of a critical bubble at the cost of the ionization energy of the heavy ion. The calculated minimum energy is 8.99keV for dichlorodifluoromethane (R-12) at 25°C. The results of calculations have been combined with those of calibrations of bubble detectors with heavy ions at accelerator. The threshold (1.510.04) MeVmg cm is obtained in the calibration with heavy ions for the above liquid and temperature. It shows that the distance over which the heavy ion traverses and transfers energy to the superheated liquid to produce a critical bubble is 4.67 times the radius of the seed bubble. The radius of the cylinder along which the heavy ion deposits energy to form a seed bubble is about 5.2nm. This dimension indicates that the process of track formation in bubble detectors is consistent with the model of thermal spike. [Copyright &y& Elsevier]

Different stacks of tissue equivalent targets interleaved with CR-39 nuclear track detectors were irradiated with 135 MeV/u 12C and 16O ions. After track etching and measurement by an automatic image analysis system, a method of trajectory tracing was applied. The trajectories of particles were reconstructed using a pattern-matching method based on a comparison of relative track coordinates.Fragmentation products have a lower charge and can be clearly distinguished by their smaller track sizes. The track positions within the individual trajectory are additionally fitted to a straight line, from which we can determine the direction of the traversing ion within a path of a few mm. We performed an angular distribution study of the fragments, which we compared to simulation results obtained by a simple particle emission model. For the fitted parameters the model showed agreement within the margins of error but failed to describe the energy dependence and thus should be further improved and upgraded. [Copyright &y& Elsevier]

Abstract: Observation of trans-iron nuclei in galactic cosmic rays () requires a high performance cosmic ray detector telescope with a large exposure area because of their extremely low fluxes. A solid-state track detector such as CR-39 has the advantage of easy extension of exposure area, but it is necessary to raise the detection threshold in order to suppress background tracks produced by galactic cosmic rays with . The track registration sensitivity and detection threshold for heavy ions with various were verified by using track detectors of copolymers of CR-39 and DAP (diallyl phthalate) with various DAP concentration. We found that it is possible to control the detection threshold of copolymers by changing DAP concentration. In order to detect heavy ions with , the optimum DAP concentration was found to be approximately 50%. [Copyright &y& Elsevier]