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Abstract This review paper intends at identifying the early processes arising during the formation of a latent ion track in Poly Allyl Diglycol Carbonate (PADC). We briefly summarize the physical and chemical processes specific to the description of the interaction of ionizing radiation with matter. Then we gather published information in relation to PADC response regarding energy absorption and further transient species formation. Emphasis is given to the chemistry of radicals. Due to a lack of available data in relation with clearly identified unpaired electron carriers in PADC, we use data stemming from surrogate molecules. Based on such data we suggest mechanisms for the decomposition of PADC during the early times of ion track formation. The α-sites of ether functional groups in PADC appear undoubtedly as critical targets which during further decomposition behave as the most probable origin of Carbon dioxide release. All suggested mechanisms are multi-step processes. Combining different concepts and data in relation with the dynamics of transient species formed in the ion track of a polymer material, we propose that the effective track radius may be described as the radial extension of reactive species formed rather than the maximum distance at which δ-rays escape out of ion's trajectory. Lastly, generalization of the different processes collected allows two major pathways to be proposed for describing the fate of damaged ether moieties in PADC. This way, evidence is given for a higher sensitivity of ether functional groups compared to ester carbonate ones. The latter generally being destroyed as a consequence of prior damaging of the ether group. Discussion presented here is of interest to the nuclear track community. Highlights • The physical and chemical phases of an ion track formation are recalled. • The chemistry of radicals in PADC surrogate molecules is described. • α-sites of ether functional groups in PADC appear as critical targets. • The dynamics of transient species formed in the ion track is described. • Main pathways for PADC degradation by ionizing radiations are suggested. [ABSTRACT FROM AUTHOR]

The Ag + -doped phosphate glass which is commonly employed as the radiophotoluminscence (RPL) dosimeter has been applied as a nuclear track etch detector. The glass is etchable in the NaOH solutions and forms clear nuclear etch pit. The etching performances and track parameters vary as a function of the concentration of NaOH solution. The most sensitive normality was confirmed to be 7 N. The track response is controllable with NaOH concentration at the range of Z ∗ / β ≥ 80 ( Z ∗ : effective charge, β : velocity). The charge spectroscopic resolution for Xe ( Z ∗ / β = 107) was found to be 0.23 cu (charge unit), which would allow to identify individual nuclear charge of ultra heavy nuclei around Actinides in the cosmic rays. The Ag + -doped phosphate glass would be a promising detector for high Z spectroscopy for cosmic ray and nuclear physics fields and has the potential to operate not only RPL dosimeter but also nuclear track etch detector. [ABSTRACT FROM AUTHOR]

Abstract: The average absorbed dose and dose equivalent rates from space radiation were observed using passive dosimeters with same material and configuration at the same location onboard the International Space Station (ISS) over four different occasions (I–IV) between 2007 and 2008. The passive dosimeters consisted of a combination of thermoluminescent detectors (TLDs) and plastic nuclear track detectors (PNTDs). Total average absorbed dose rate increased by 68 ± 9% over two years. The observed increase was due to the incremental increase in the altitude of the ISS over the course of the experiment and the corresponding increase in trapped proton flux encountered during passage of the ISS through the SAA (South Atlantic Anomaly), which was confirmed with the results monitored by DB-8 active dosimeter on the ISS. The PNTD data showed that the average absorbed dose and dose equivalent rates from particles of LET∞H2O ≥ 100 keV/μm were 28 ± 2% and 51 ± 3% of ≥10 keV/μm during Periods I–III, while the dose contributions of particles ≥100 keV/μm during Period IV were 36 ± 5% and 59 ± 10%, respectively. The integral dose equivalent distribution during Period IV shows significant enhancement from particles ≥100 keV/μm. These facts suggest that a significant fraction of the high LET component is due to short-range recoil nuclei produced in target fragmentation reactions between primary protons and the nuclei of the passive dosimeters and surrounding materials. [Copyright &y& Elsevier]

To reduce or eliminate fluctuations in fluorescence intensity due to optical absorption and spherical aberration of a focused laser beam, and variations in color center concentrations between individual Al 2 O 3 :C,Mg-based fluorescent nuclear track detectors (FNTDs), we adopted the intensities of F 2 2+ (2 Mg) and F 2 + (2 Mg) color centers corresponding to green and near-infrared (NIR) colorations, respectively. These intensities were used to develop coloration-dependent correction methods to improve accuracy of the FNTD-based heavy ion measurements. The FNTDs were irradiated with He, C, Ne, and Fe ions to prepare mono-energetic and multi-energetic specimens and then the performance of the correction methods was evaluated. Both the green and NIR coloration-dependent correction methods eliminated fluctuations in fluorescence intensity with depth, reducing the coefficient of variation (CV) by 36.6% and 35.9%, respectively. The green coloration-dependent correction method also reduced fluctuations of fluorescence intensity due to color centers by decreasing CV w by 45.3%. The NIR coloration-dependent correction method was ineffective for correcting fluctuations due to color centers compared to the green coloration-dependent correction. The fluorescence intensities of He, C, and Fe tracks corrected by green and NIR colorations in the multi-energetic specimen coincided with those of mono-energetic specimens. Hence, these methods provide reliable and standardized approaches for heavy ion measurements and have the potential to be applied in determining the LET of heavy ions. • Green and NIR coloration-dependent correction methods were developed. • Green and NIR corrections reduced fluorescence fluctuations by ∼36% in FNTDs. • Green correction cut CV w by 45.3%, outdoing NIR for fluctuations due to color center. [ABSTRACT FROM AUTHOR]

Silver-activated phosphate glass (Ag+-glass), which is commonly employed as a radiophotoluminscence (RPL) dosimeter, was applied as a fluorescent nuclear track detector (FNTD). The heavy ions from C to Fe ions were detected as fluorescent nuclear tracks under a confocal microscope. The detection linear energy transfer (LET) threshold was estimated to be 5 keV/μm in water. The fading effect was observed in which the fluorescent intensity decreases with repeated laser scans. The Ag+-glass has good potential applicability as the FNTD for the high LET range (5–200 keV/μm) in radioimmunotherapy and space radiation dosimetry uses. • Silver-activated phosphate glass operated as a fluorescent nuclear track detector. • Fluorescent tracks of heavy ions from C to Fe ions were observed with a confocal microscope. • Detection threshold of linear energy transfer was 5 keV/μm in water. • One-time scanning is recommended due to the fading effect by repeated laser scanning. • Ag+-glass FNTD is applicable for radioimmunotherapy and space radiation dosimetry uses. [ABSTRACT FROM AUTHOR]

Abstract In hadron therapy, it is important to evaluate how sensitive a detector is upon radiation with varying ionization densities, i.e. linear energy transfer (LET), as the LET changes when penetrating through material. For solid-state detectors, it is therefore essential to characterize the luminescence efficiency ( η HT , γ) of the detector as a function of LET. In this work, we investigate the radiophotuminescence (RPL) response from Al 2 O 3 :C,Mg 2D films and crystals exposed to various high LET beams (1H, 4He, 12C, 28Si and 56Fe). The measured η HT , γ curve from RPL films and crystals as function of the particle LET is compared with the η HT , γ curve from Al 2 O 3 :C OSL samples. Furthermore, a 2D RPL image, from Al 2 O 3 :C,Mg films irradiated with a 61.3 MeV 40 mm diameter broad proton beam, depicts a 2D depth dose distribution of the Bragg peak and demonstrates similar LET dependence as from the luminescence efficiency curve. The η HT , γ curves are consistent with Birks' law, where we observe expected quenching for increasing LET. Highlights • 2D films and single crystals of Al 2 O 3 :C,Mg irradiated with charged particle beams. • Luminescence efficiencies curves. • 2D image along the Bragg curve is acquired with a proton beam. [ABSTRACT FROM AUTHOR]

This paper reports the relation between latent track structure and the detection threshold of etch pits formation in UPILEX-S® and Kapton. At the similar stopping power value, effective track core radii and G values for heavier ions are lower than those of lighter ions. These results would be due to the difference of the radial dose distribution for low- and high-velocity ions. The G value starts more rapidly rising above 600 and 1000 keV/μm for Kapton and UPILEX-S®, respectively. The detection threshold of UPILEX-S is 4000 keV/μm for Ar ions, at which effective track core radii of all functional groups are larger than 2 nm. Since the length of a molecule unit of UPILEX-S® is about 1.4 nm, at least more than two molecule units have to be damaged for the etch pit formation. A similar discussion is applicable to Kapton, whose detection threshold is significantly lower than UPILEX-S®. • The latent track structure of UPILEX-S ® irradiated with heavy ions is investigated. • The G values of C and Ne ions around Bragg peak energies are higher than that of Kr and Xe ions with high-energies. [ABSTRACT FROM AUTHOR]

This paper reports the variation of track registration sensitivity as a function of the stopping power of heavy ions in UPILEX-S ® films, which is known as the most radiation tolerant polyimide (PI). The detection thresholds in the stopping power for etch pit formation are determined as 4,000, 4,100, 4,800, and 5600 keV/μm for 40Ar, 84Kr, 132Xe and 238U ions, respectively. Furthermore, we investigate the latent track structure in two kinds of PI films (UPILEX-S® and Kapton) by means of FT-IR spectroscopy. At the similar stopping power value, the radiation chemical yields (G value) for heavier ions are lower than those of lighter ions. This is due to the difference of the radial dose distribution for low and high velocity ions. • The track registration property of UPILEX-S ® irradiated with heavy ions is investigated. • The detection thresholds of UPILEX-S ® for heavy ions are determined in the stopping power. • The obtained results are compared with those of other PNTDs. [ABSTRACT FROM AUTHOR]

Standardization of the concentration of gaseous 222Rn based on a multi-electrode proportional counter (MEPC) is under development as a primary standard in Japan. In this study, the concept and evaluation of its performance are reported. The latter consists of a preliminary result for the uncertainty budget associated with the measurement of the MEPC and compensation of the electric field distortion in the MEPC. Moreover, an ionization-chamber-based gas circulation system was added for the calibration of radon monitors in the air. • Highlights paper 70 Furukawa et al.: • Standardization of the concentration of gaseous 222Rn based on a multi-electrode proportional counter (MEPC) is under development. • The relative standard uncertainty associated with the measurement of the MEPC was evaluated preliminarily to be 1.4%. • A new calibration system was devised that includes an inner-through-type ionization chamber as a transfer standard. [ABSTRACT FROM AUTHOR]

Abstract: Production of target fragments from reactions of 160 MeV proton beams in aluminum and polyethylene was measured with CR-39 plastic nuclear track detectors (PNTD). Due to the detection limit of PNTD, primary protons cannot be detected; only low-energy short-range target fragments are registered. As a feasibility study, a so called “two step etching method” was employed to get the linear energy transfer (LET) spectra, absorbed dose, and dose equivalent. This method is discussed in this paper, together with the measured results. [Copyright &y& Elsevier]

Real-time radioluminescence two-dimensional coatings have potential as dosemeters in proton and carbon therapeutic beams. We investigated coatings made of nano and micro-(C 44 H 38 P 2)MnCl 4 and (C 38 H 36 P 2)MnBr 4 crystals mixed with a water-equivalent substrate. The response of the radioluminescence signal of the coatings along the Bragg curves presented an ionization quenching effect, but less prominent than what has been observed in our previous works using Al 2 O 3 :X (X = C and C,Mg) coatings. We hypothesize that this results from their lower crystal sizes and effective atomic number (Z eff). Combined experimental results and Monte Carlo simulations resulted in correction factors to address the linear energy transfer dependence and restore the constant response for particle therapy beams. The quenching correction method was applied to the studied proton and carbon ion beams and yielded the best results for the nano-(C 44 H 38 P 2)MnCl 4, coating, followed by the micro-(C 44 H 38 P 2)MnCl 4 , nano-(C 38 H 36 P 2)MnBr 4 , and micro-(C 38 H 36 P 2)MnBr 4. • Real-time RL coatings developed for proton and carbon ion dosimetry, using nano and micro crystals. • Quenching effects in RL coatings less prominent than Al 2 O 3 :C and Al 2 O 3 :C,Mg due to lower crystal sizes and Zeff. • Quenching correction best in nano-(C44H38P2)MnCl4 coating, followed by other tested coatings. [ABSTRACT FROM AUTHOR]

The alpha-particle targeted radionuclide therapy (TRT) has been actively investigated for cancer treatment, and astatine-211 (211At) is one of the promising alpha-particle emitters. To evaluate the efficacy of radioactive pharmaceuticals, it is necessary to understand the 211At distribution in a body to accurately assess radiation dose in the targeted cells. In this study, an X-ray imaging camera was developed to investigate an in vivo 211At imaging technique for the alpha-particle TRT, especially to apply for small animal investigations. The design of the X-ray imaging camera was optimized to measure Po K X-rays (77–92 keV) emitted during 211At decay. It comprised a monolithic NaI(Tl) scintillator, a position-sensitive photomultiplier, and a tungsten pinhole collimator. The intrinsic performance evaluation of the position-sensitive X-ray detector exhibited good energy resolution, spatial resolution, and response uniformity. Using point-like 211At sources, the 211At distribution was successfully obtained by the X-ray camera with a useful field-of-view of 20.4 × 20.4 mm2, a system spatial resolution of 1.6 mm, and a sensitivity of 2.4 × 10−4, equivalent to 101 cps/MBq, on the collimator axis at a 12.5 mm distance. This study demonstrated the imaging capability of 211At with high sensitivity and spatial resolution by the X-ray imaging camera with a pinhole collimator. • An X-ray imaging detector was investigated for 211At imaging in alpha-particle TRT. • 211At distribution was obtained using a scintillator-based X-ray pinhole camera. • A spatial resolution of less than a few mm was achieved for close targets. • The proposed system is applicable to 211At imaging in small animal experiments. [ABSTRACT FROM AUTHOR]

Referring to the observed results on the source composition of galactic cosmic rays, a possible mechanism for the formation of this composition is proposed by taking into account the fractionation of elements in dust grains formed in the interstellar molecular clouds. These dust grains become enriched with the elements whose condensation temperature is higher than about 1000K. Most of these nuclei enhanced in the source composition are identified as heavy and ultra-heavy ones, which must have been synthesized in the r-process initiated with the explosions of type II supernovae in the OB-association. The dust grains in the superbubble are later ionized and then accelerated through their interactions with shock waves of supershell formed from multiple explosions of nearby supernovae. This may mean that cosmic rays are significantly generated from the dust grains drifting in the local interstellar space. [Copyright &y& Elsevier]

In this work, pellets of CaSiO 3 have been produced for investigation as gamma radiation, proton, and carbon ions detector. They were then irradiated to gamma radiation using 137Cs and 60Co sources. Furthermore, pellets of CaSiO 3 were exposed to 160 MeV proton and 290 MeV/n carbon ion beam from an upper synchrotron. Thermoluminescence (TL) responses of these pellets presented the same prominent peak at about 170 °C, and two possible high-temperature peaks at 270 and 320 °C when irradiated to gamma, proton, and carbon ion beam. Dose-response curve, minimum detectable dose (MDD), energy dependence, and dependence on the dose rate when irradiated with gamma radiation were evaluated in this material. Linear dose-response curves for proton and carbon ion irradiation have been compared to that of the gamma dose-response. In this way, the dose read out in Harshaw TL reader presented a good agreement with doses found using ion chamber in the case of proton beams and slightly less in the case of carbon beam due to the LET dependency. Furthermore, relative efficiencies of CaSiO 3 for beam irradiation of proton and carbon ion display no dependence in the analyzed particle doses range. • Pellets of CaSiO 3 have been produced for high-energy gamma and particle detection. • MDD for CaSiO 3 pellets was calculated using the gamma dose-response calibration curve. • Energy and dose rate dependences for CaSiO 3 pellets were studied. • Proton and carbon dose-response curves were compared to that of gamma irradiation. • Relative efficiencies for ion beam irradiation are independent of the particle dose. [ABSTRACT FROM AUTHOR]

We report the loss of carbonate ester and the creation of embedded CO 2 molecules and OH groups in poly (allyl diglycol carbonate) (PADC) irradiated with C (11 MeV/u) and O ion (7.5 MeV/u) beams under vacuum at low temperatures (11, 100 and 200 K) and at room temperature (RT) using in-situ FT-IR spectrometry. For comparison with these experiments, the behavior under O ions (6 MeV/u) irradiations in ambient air is examined by off-line FT-IR spectrometry. The radiation chemical yield for loss of carbonate ester (G-carbonate) in PADC irradiated with O ions at 11 K is lower than that obtained at RT. Furthermore, the G value of embedded CO 2 molecules (G-CO 2) under O ion decreases with decreasing temperature. As CO 2 molecules have been said to be formed from the fragmentation of carbonate groups, G-CO 2 is compared to G-carbonate. For given temperatures, G-CO 2 is significantly lower than G-carbonate. These findings imply that the molecular and radical mobility is crucial for CO 2 formation after damage to carbonate groups. As for OH groups, their formation under vacuum is suppressed at low temperatures and a tenuous formation is observed at RT. Oxygen and potentially water molecules, which are present in ambient air, play important roles in the formation of OH groups as new end-points. • The G-CO 2 decreases with decreasing temperature. • The G-CO 2 gas is smaller than G-carbonate in PADC. • The creation of OH groups after the irradiations is completely suppressed at low temperatures. [ABSTRACT FROM AUTHOR]

Abstract We aim to elucidate the chemical damage structure in poly(allyl diglycol carbonate), PADC, exposed to UV photons with a wavelength of 222 nm using FT-IR spectrometric method. The number density of carbonyl (C˭O) in PADC, which composes carbonate ester, is hardly affected by the UV photons below the critical fluence of 3.0 × 1019 photons/cm2. The number density of carbonyl decreases only above the critical fluence, while those of ether and C-O-C in carbonate ester are monotonically cleaved. These findings corroborate the previous result using 28 MeV electron beams, in which the carbonate ester is lost only above the critical fluence of 1.6 × 1015 electrons/cm2, where the overlapping of electron tracks becomes significant. We extend the conventional track overlapping model to clarify the spatial distribution of point-like defects after the UV exposure. The discrete damage is seen at the critical condition, based on the extended track overlapping model. Highlights • The quantum yields in PADC exposed to UV photons are evaluated. • The carbonyl in PADC begins decreasing only above the critical fluence. • The conventional track overlapping model is extended. • The noncontiguous damage distribution in PADC is found. [ABSTRACT FROM AUTHOR]

The main obstacle to applying aluminum oxide doped with carbon and magnesium (Al 2 O 3 :C,Mg)-based fluorescent nuclear track detectors (FNTDs) in radionuclide therapy with alpha emitters is that it has not been known how to achieve an accurate and in situ dose assessment for in vitro cellular experiments. In this study, we developed an automatic 3D track reanalysis algorithm (ATRA) to analyze the alpha energy spectra in FNTDs. The algorithm provides an excellent track identification rate and an excellent track linking rate (0.961) without significant variations in various track densities. The algorithm also achieves a reliable track detection rate exceeding 0.927 for track densities at the level of in situ measurement, and it successfully measures the alpha energy spectra for obtaining the absorbed dose. We also confirmed that the track overlap clearly interferes with accurate track reconstruction for track densities beyond 1.5 × 106 tracks cm−2. We provided a correction equation that can be used to obtain the actual alpha tracks for high track densities; the equation may also correct estimations of absorbed doses due to alpha particles. • Automatic 3D track reanalysis algorithm (ATRA) was developed. • The track detection rates of ATRA exceeded 0.927 at in situ measurement level. • The effect of track overlap on ATRA was quantified with various track densities. • Correction equation was provided for correcting absorbed dose due to alpha particle. [ABSTRACT FROM AUTHOR]

Abstract Lithium fluoride thermoluminescent radiation detectors with different dopant concentrations (7LiF:Mg,Ti and 7LiF:Mg,Cu,P) were exposed to 1H and 4He ions at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in order to investigate their response to energetic light charged particles. Computer simulations with the Monte Carlo code PHITS were performed for a better interpretation of the experimental data. The results were compared with literature efficiency data and with the results of a recently developed microdosimetric efficiency model. In case of the main peak signal of 7LiF:Mg,Ti detectors, the determined efficiency values are in good agreement with previous investigations. Discrepancies in the efficiency of high temperature signal due to well-known non-linearity effects are reported. For 7LiF:Mg,Cu,P detectors, an anomalous thermoluminescence behavior in the low temperature part of the signal was found and discussed. Depending on the light quantification process, differences up to 30% in the dose assessment can be obtained, affecting also the relative efficiency determination process. An explanation of this phenomenon as a consequence of local migration of the charged carriers between the low temperature peaks and the main peak is presented. The implications of these findings on the use of LiF:Mg,Cu,P detectors in radiation environments characterized by the presence of 1H and 4He ions (i.e. space and proton therapy) are discussed. In order to avoid the occurrence of this anomalous behavior, it is advised to pre-heat the detectors after energetic light particle exposures. Highlights • LiF:Mg,Ti and LiF:Mg,Cu,P thermoluminescent detectors were exposed to 1H and 4He ions. • An anomalous low temperature behavior was found for LiF:Mg,Cu,P detectors. • This can affect the dose assessment process with LiF:Mg,Cu,P detectors up to 30%. [ABSTRACT FROM AUTHOR]

Abstract The detection threshold of poly(allyl dyglycol carbonate), PADC, for C ions is determined as 55 eV/nm in stopping power, which is significantly higher than that for proton and He ions. The stopping power is not a universal parameter for expressing the detection threshold of PADC. A new physical parameter of Radial Electron Fluence around Ion Tracks, REFIT , is proposed to describe the detection threshold of PADC. It is defined as the number density of electrons passing through the surface of a cylinder of a certain radius that is co-axial with the trajectory. Furthermore, preliminary calculations are presently being performed using the Monte Carlo simulation code of Geant4-DNA. The values of the REFIT at the detection thresholds for each ion are of the same order. Several issues affecting implementation of the REFIT paramter are discussed. These include the effects of impact parameter relating to the initial locations of secondary electrons, the effects of electron attachment below the cut off energy of 7.4 eV and the necessity of a more physically realistic medium than water for Monte Carlo simultaions. Highlights • Radial Electron Fluence around Ion Tracks, REFIT, is proposed as a new physical parameter for the detection threshold of PADC. • First calculation is made using Geant4-DNA toolkit. • Several future issues are discussed to improve the REFIT. [ABSTRACT FROM AUTHOR]

Abstract To compare the response to high energy neutrons and protons of the space bubble detectors in use aboard the International Space Station (ISS), three series of experiments were conducted with high energy protons and neutrons. The first series of experiments was conducted with high-energy neutrons in the energy range expected for neutrons encountered during space flight (0.6–800 MeV) at the Los Alamos Neutron Science Center (LANSCE) using the spallation neutron source. The second series was conducted with high energy protons from 30 to 70 MeV using the cyclotron at the National Institute of Radiological Science NIRS in Japan, and the third series of experiments was performed with high energy protons from 60 to 230 MeV at the ProCure proton therapy facility, Oklahoma, USA. The bubble detectors were exposed to different fluences in different experiments and the number of bubbles was counted using a bubble detector reader. The proton response of the bubble detector (sensitivity), as a function of energy, was determined and compared to the neutron sensitivity. In addition, to adjust the neutron sensitivity of the bubble detector determined in an AmBe field, a calibration factor was obtained for space applications. Highlights • Experimental investigation of the bubble detector response to space-like neutrons at LANSCE. • Experimental investigation of the bubble detector response to high energy protons at NIRS in Japan. • Experimental investigation of the bubble detector response to high energy protons at ProCure. • Comparison of the space bubble detector sensitivity to high energy protons and neutrons. [ABSTRACT FROM AUTHOR]

G values of the losses of typical functional groups in PET films along boron ion tracks have been determined using FT-IR spectrometry. G value for the loss of aromatic-ring clearly increases above 270 eV/nm. Those of ester and ethylene increase around the slightly lower stopping power of 250 eV/nm. The detection thresholds are defined by determining the original points from which the evolution of etch pit starts along the latent track, when the chemical etching was progressing starting from the front surface of each incident ion trajectory. The thresholds for B, C, N, O, Ar and Kr ions have been determined for other kind of PET sheets. Values of the sensitivity at the thresholds are fairly higher at heavy ions with smaller atomic number. [ABSTRACT FROM AUTHOR]

A low 134 Cs/ 137 Cs ratio anomaly in the north-northwest (NNW) direction from the Fukushima Dai-ichi Nuclear Power Station (FDNPS) is identified by a new analysis of the 134 Cs/ 137 Cs ratio dataset which we had obtained in 2011–2015 by a series of car-borne surveys that employed a germanium gamma-ray spectrometer. We found that the 134 Cs/ 137 Cs ratio is slightly lower (0.95, decay-corrected to March 11, 2011) in an area with a length of about 15 km and a width of about 3 km in the NNW direction from the FDNPS than in other directions from the station. Furthermore, the area of this lower 134 Cs/ 137 Cs ratio anomaly corresponds to a narrow contamination band that runs NNW from the FDNPS and it is nearly parallel with the major and heaviest contamination band in the west-northwest. The plume trace with a low 134 Cs/ 137 Cs ratio previously found by other researchers within the 3-km radius of the FDNPS is in a part of the area with the lower 134 Cs/ 137 Cs ratio anomaly that we found. Our result suggests that this lower 134 Cs/ 137 Cs ratio anomaly is the area which was contaminated before March 13, 2011 (UTC) in association with the hydrogen explosion of Unit 1 on March 12, 2011 at 06:36 (UTC) and it was less influenced by later subsequent plumes. [ABSTRACT FROM AUTHOR]

A series of FT-IR spectrometric studies has been performed to understand the latent track structure in poly(allyl diglycol carbonate), PADC, which were exposed to proton beams with energies of 20, 30 and 70 MeV. These energies are too high to register etchable tracks in PADC. Chemical damage parameters, such as damage density, effective track core radius and radiation chemical yields, for losses of ether bond, carbonate ester bond and CH groups in PADC are evaluated as a function of the stopping power, which were compared to the previous results for 5.7 MeV proton and heavy ions, between He and Xe. Graphs of the chemical damage parameters are given at the wide stopping powers ranging from 1 to 12,000 keV/μm. The decreasing behaviors of the ether and carbonate ester bonds are on the almost identical trends with those of the heavy ions. On the contrary to this, the reducing behavior of CH groups is similar to that of the gamma rays. Different dependence of the chemical damage parameters for the loss of CH groups is found on the stopping powers between the both sides of the detection threshold as an etched track detector. [ABSTRACT FROM AUTHOR]

A fluorescent nuclear track detector (FNTD) is a single crystal of aluminum oxide doped with carbon and magnesium (Al 2 O 3 :C,Mg). We report calibration method of difference in the fluorescence intensity depending on the color center concentration (coloration) using a confocal microscope. The fluorescence intensity ratio of 510–530 nm due to the excitation at 488 nm to the reflection intensity of 483–493 nm is used for the coloration correction. The fluorescence track intensity of alpha particles increases monotonically with the color center concentration. From the relation between values of coloration concentration and the fluorescence track intensity of alpha particles, we have made a correction function. Consequently, the standard deviation of the detection of alpha particles with the coloration correction becomes six times smaller than without it. Additionally, the track response curve is properly made in a wide LET range from 1 to 200 keV/μm. • We have corrected the difference of the sensitivity between FNTD chips. • The deviation becomes six times lower by the correction. • The track response curve of FNTD is made in a wide LET range. [ABSTRACT FROM AUTHOR]

Modified structure along ion tracks in poly(allyl diglycol carbonate), PADC, films exposed to protons and heavy ions, He, C, Ne, Ar, Fe, and Xe, in air has been examined by means of FT-IR spectroscopy, covering the stopping power ranging from 10 to 12,000 keV/μm. The damage density for the loss of CH groups and the amount of formed OH groups along each tracks are estimated and compared to the previous results on the ether and the carbonate ester bonds. The CH groups are lost in the center region of the track core with other functional groups and the OH groups are created as new end-points of the polymer network. We obtained the molar absorption coefficient for OH of water absorbed in PADC films as 9.7 × 10 3 M −1 cm −1 . It has been assumed that the coefficient is applicable to the OH groups on the polymer. The amount of OH groups are almost equivalent to the damage density of the ether bonds. [ABSTRACT FROM AUTHOR]

Fluorescent nuclear track detectors (FNTDs) based on Al 2 O 3 :C,Mg crystals are luminescent detectors that can be used for dosimetry and detection of charged particles and neutrons. These detectors can be utilized for imaging applications where a reasonably high track density, approximately of the order of 1 × 1 0 4 tracks in an area of 100 × 100 μ m 2 , is required. To investigate the reusability of FNTDs for imaging applications, we present an approach to perform optical bleaching under the required track density conditions. The reusability was assessed through seven irradiation-bleaching cycles. For the irradiation, the studied FNTD was exposed to alpha-particles from an 241Am radioactive source. The optical bleaching was performed by means of ultraviolet laser light with a wavelength of 355 nm. Three dedicated regions on a single FNTD with different accumulated track densities and bleaching conditions were investigated. After every irradiation-bleaching cycle, signal-to-noise ratio was calculated to evaluate FNTD performance. It is concluded that FNTDs can be reused at least seven times for applications where accumulation of a high track density is required. • FNTDs can be used for the micrometer scale neutron imaging applications under high accumulated track density condition. • The optical bleaching of the FNTDs was investigated using a UV laser light of 355 nm. • The re-usability of the FNTDs was investigated through seven repeated iterations of the irradiation of alpha particles. • FNTDs can be re-used at least seven times for the applications where accumulation of high track density is required. [ABSTRACT FROM AUTHOR]

We constructed a new car-borne survey system called Radi-Probe with a portable germanium gamma-ray spectrometer onboard a cargo truck, to identify radionuclides and quantify surface contamination from the accident at Fukushima Dai-ichi Nuclear Power Station. The system can quickly survey a large area and obtain ambient dose equivalent rates and gamma-ray energy spectra with good energy resolution. We also developed a new calibration method for the system to deal with an actual nuclear disaster, and quantitative surface deposition densities of radionuclides, such as 134 Cs and 137 Cs, and kerma rates of each radionuclide can be calculated. We carried out car-borne survey over northeastern and eastern Japan (Tohoku and Kanto regions of Honshu) from 25 September through 7 October 2012. We discuss results of the distribution of ambient dose equivalent rate H ∗ (10), 134 Cs and 137 Cs surface deposition densities, spatial variation of 134 Cs/ 137 Cs ratio, and the relationship between surface deposition densities of 134 Cs/ 137 Cs and H ∗ (10). The ratio of 134 Cs/ 137 Cs was nearly constant within our measurement precision, with average 1.06 ± 0.04 in northeastern and eastern Japan (decay-corrected to 11 March, 2011), although small variations from the average were observed. [ABSTRACT FROM AUTHOR]

Abstract: The sensitization effect of carbon dioxide treatments with 0.6 MPa on poly(allyl diglycol carbonate) (PADC) etched track detectors is confirmed for protons and He, C, and Fe ions, where the stopping powers range from 10 to 600 keV/μm. Based on the FT-IR study for the PADC films that were maintained at room temperature and at elevated temperatures, the diffusion coefficient of carbon dioxide, is determined as D = 14,670exp(−9030/T(K)) cm2/s. The sensitivity is enhanced when carbon dioxide is released toward the chemical etching solution that passes through the detector surface. Segmented PADC polymer chains are washed away by the flow of carbon dioxide along the latent tracks in PADC, which results in a higher track etch rate. [Copyright &y& Elsevier]

Abstract: In order to understand the vacuum effects on the sensitivity of PADC detectors from the viewpoint of molecule structural modification along nuclear tracks, a series of FT-IR spectrometric studies has been made for PADC films exposed to He and C ions at energies below 6 MeV/n, as well as to gamma rays from an intense Co-60 source, under the both conditions of in air and in vacuum. The radiation chemical yields for the losses of ether and carbonate ester bonds are hardly affected by the environmental conditions in the cases of He and C ion irradiations. For gamma ray, the yields are about half in vacuum compared to those in air. The formation of OH groups is fairly suppressed in vacuum in all cases. Recombination of free radicals resulted in modified polymeric network formation would be enhanced in heavy ion irradiations rather than in that of gamma irradiations. [Copyright &y& Elsevier]