CR-39 Plastic Nuclear Track Detectors Research Articles

The total and the partial charge-changing cross sections of 40Ar fragmentation on elemental targets at 500 A MeV

The total and the partial charge-changing cross sections of 40Ar fragmentation on CH2, C, Al, Cu and Pb targets at the highest energy of 495 A MeV were investigated using CR-39 plastic nuclear track detector. The total charge-changing cross-section for hydrogen target was calculated based on the results of polyethylene and carbon targets. It was found that the total charge-changing cross sections for fragmentation of 40Ar on H, C, Al, Cu and Pb targets were independent on the beam energy in our studied energies, and were consistent with the predictions of Bradt-Peters semi-empirical formula. Nilsen semi-empirical formula, NUCFRG2 and PHITS simulation codes given an underestimation of experimental data. The partial cross sections for projectile fragment production were independent on the beam energy in our studied energies for each target and do not show a significant odd-even effect. The partial cross sections for projectile fragment production were also compared with different empirical parametrization formulas, such as different version of Cummings, Nilsen, FRACS and EPAX3. Generally, EPAX3 and FRACS empirical parametrization can give a reasonable estimation of data within 25% relative errors.

Measurement of therapeutic 12C beam in a water phantom using CR-39

The motivation for this study was to explore a new method to test the particle spatial distribution for a therapeutic carbon beam. CR-39 plastic nuclear track detectors were irradiated to a 276.5 MeV u−1 mono-energy carbon beam at the heavy ion facility in the Shanghai Proton and Heavy Ion Center. The spatial distribution of the primary carbon beam and secondary fragments in a water phantom were systematically analyzed both in the transverse direction (perpendicular to the projection direction of the primary beam) and at different depths in the longitudinal direction (along the projection direction of the primary beam) with measured tracks on the CR-39 detectors. Meanwhile, the theoretically spatial distribution and linear energy transfer (LET) spectra of the primary beam and secondary fragments were calculated using the Monte Carlo (MC) toolkit Geant4. The results showed that the CR-39 detectors are capable of providing high lateral resolution of carbon ion at different depths. In the range of the primary carbon beam, the beam width simulated with MC is in good agreement with that of experimental measurement. The track size registered in the CR-39 has a good correlation with the particle LET. These findings indicate that the CR-39 can be used for measuring both the particle flux and its spatial distribution of carbon ions.

Shielding effectiveness: A weighted figure of merit for space radiation shielding

The risk to space crew health and safety posed by exposure to space radiation is regarded as a significant obstacle to future human exploration missions to the Moon, Mars, and beyond. Engineers developing future spacecraft or planetary surface habitats can benefit from detailed knowledge of a broad range of possible materials that could provide improved protection to space crews from the deleterious effects of prolonged exposure to the space radiation environment. As one step towards providing this knowledge base, we have developed an empirical weighted figure of merit, referred to as shielding effectiveness, that quantifies the ability of a candidate material to shield space crews from the space radiation environment. The shielding effectiveness, as formulated in this study, accounts for the competing physical aspects of target and projectile fragmentation to provide a comprehensive assessment of radiation protection with regard to passive shielding for space applications. The empirical data used in determining shielding effectiveness was obtained from proton and heavy ion accelerator-based experiments wherein Al2O3:C optically stimulated luminescence dosimeter and CR-39 plastic nuclear track detector were irradiated behind candidate space radiation shielding materials of varying composition and depth. As a test case, the experimental setup was exposed to nominal beams of 1 GeV protons, and 1 GeV/n 28Si and 56Fe heavy ions, the latter serving as a sample of the high linear energy transfer portion of the galactic cosmic ray spectrum. Established radiation dosimetry techniques were used to obtain linear energy transfer spectra, absorbed dose, and dose equivalent as a function of depth. Based on the measurement results, a shielding effectiveness value was computed, quantifying the efficacy of the candidate material as a function of depth, with cumulative weighting factors accounting for the measured percent composition of baryonic matter in the galactic cosmic ray spectrum, and the measured percent contribution to absorbed dose and dose equivalent. The methodology for shielding effectiveness was tested using the common materials of aluminum, copper, graphite, and water, with polyethylene serving as the standard reference. The preliminary shielding effectiveness values for these materials confirm the low Z principle for effective space radiation shielding, and, furthermore, these values tend to be lower when the effectiveness calculation is based on dose equivalent. Of the common materials studied here, at a bulkhead depth of 5 g/cm2, all materials provide a similar level of radiation protection to within standard error. In addition, this method can be used to supplement and/or verify similar findings obtained from transport models.

Detection of alpha and 7Li particles from 10B(n, α)7Li reactions using a combination of CR-39 nuclear track detector and potassium hydroxide-ethanol-water solution in accelerator-based neutron fields

We investigated the optimum etching condition for potassium hydroxide-ethanol–water solution (PEW) to detect only alpha and 7Li particles from 10B(n, α)7Li reactions registered in a CR-39 plastic nuclear track detector. The background recoil protons, which are induced by fast neutrons with energies of <2 MeV produced by 9Be(p, n)9B reactions in accelerator-based neutron sources, were discriminated by the desensitization effect with PEW. We found that an ethanol concentration of ≥15 wt% in a PEW solution discriminated recoil proton tracks with energies of <2 MeV. The optimized conditions will be applicable for evaluating dose distribution in tissue in accelerator-based boron neutron capture therapy.

Projectile fragment emission in the fragmentation of $$^{\bf 56}\mathbf{Fe}$$ on Al, C, and $$\mathbf{CH}_{\mathbf{2}}$$ targets

The emission angle distribution of projectile fragments (PFs) and the temperature of PF emission sources for fragmentation of $$^{56}\hbox {Fe}$$ on polyethylene, carbon, and aluminum targets at the highest energy of 497 A MeV are investigated on the basis of corrected data, using a CR-39 plastic nuclear track detector. It is found that the average emission angle of PFs increases with the decrease in PF charge for the same target, and no obvious dependence of angular distribution on the mass of the target nucleus is found for the same PF. The cumulative squared transverse momentum distribution of PFs can be well represented by a single Rayleigh distribution. The temperature of PF emission sources is extracted from the distribution, and it is about 1.0–8.0 MeV and does not depend on the mass of the target for PFs with charges of $$9\le {Z}\le 25$$.

The total charge-changing cross sections and the partial cross sections of 56Fe fragmentation on Al, C and CH2 targets

The total charge-changing cross sections and the partial cross sections of 56Fe fragmentation on polyethylene, carbon and aluminum targets at the highest energy of 496 A MeV are investigated using CR-39 plastic nuclear track detector. The total charge-changing cross-section for hydrogen target is calculated based on the results of polyethylene and carbon targets. It is found that the total charge-changing cross sections for fragmentation of 56Fe on hydrogen, carbon and aluminum targets are independent on the beam energy in our studied energies, and are consistent with the predictions of Bradt–Peter semi-empirical formula, Nilsen parameterized formula, NUCFRG2 and QMSFRG theoretical simulation codes. The partial cross sections for projectile fragment production are independent on beam energy in our studied energies for each targets and do not show a significant even-odd effect.

Contribution to dose in healthy tissue from secondary target fragments in therapeutic proton, He and C beams measured with CR-39 plastic nuclear track detectors

The linear energy transfer (LET) spectrum, absorbed dose and dose equivalent from secondary particles of LET∞H2O ≥15 keV/μm deposited within the plateau of the Bragg curve in primary particle-induced nuclear target fragmentation reactions in tissue during proton and heavy ion radiotherapy were measured using CR-39 plastic nuclear track detectors and analyzed by means of atomic force microscopy. It was found that secondary target fragments contributed 20% to dose equivalent for primary protons (157 MeV), 13% for primary helium ions (145 MeV/n) and 4% for primary carbon ions (383 MeV/n), respectively. Little research has been done on the contribution from these particles to primary given dose. The smaller contribution measured for energetic carbon ion beams compared to proton beams can be considered an advantage of carbon ion radiotherapy over proton radiotherapy.

DISCRIMINATION METHOD FOR GAMMA RAY DOSES IN NEUTRON FIELDS USING AN IONIZATION CHAMBER WITH ATTENUATION FILTERS.

Neutron fields produced by an accelerator-driven neutron source are generally mixed radiation fields that consist of fast neutrons and gamma rays. To estimate the biological effects of fast neutrons precisely, the gamma ray dose contamination must be evaluated in neutron fields. In this work, we developed a discrimination technique for absorbed doses (60Co gamma-ray equivalent) of fast neutrons and gamma rays using an ionization chamber. The filter thickness dependences of the absorbed doses of fast neutrons and gamma rays are different for a given filter material. Thus, the absorbed doses of each type of radiation were distinguished by fitting the dose attenuation curve, which was measured with an ionization chamber and attenuation filters, with a two-component exponential function. The absorbed dose of fast neutrons and gamma rays with no attenuation filter was evaluated from the y-intercept of the fitting function. This technique was demonstrated in two neutron fields produced by 4 MeV proton and deuteron bombardment of a 9Be target. The thicknesses of the polyethylene attenuation filters were 0-350 mm. The dose attenuation coefficients of fast neutrons obtained by the two-component exponential fitting function for the 9Be(p,n)9 and 9Be(d,n) reactions showed differences of 1.5 and 1.7%, respectively, from the reference measurements using a CR-39 plastic nuclear track detector. The absorbed dose contributions of gamma rays in neutrons fields of the 9Be(p,n)9B and 9Be(d,n) reactions were evaluated as 30.2 ± 3.24% and 20.4 ± 5.16%, respectively, without polyethylene filters.

Measurement Radon Gas Concentration in Selected Soil Samples of The of Al-Nada District in Najaf

In this study fifty (50) of soil samples of AL-Nada district-Najaf Governorate –Iraq have been collected randomly and studied using solid state nuclear track detectors (CR-39) to determined 226Ra through counting the number of radon tracks by using CR-39 plastic nuclear track detector ,a long- term measurement technique has been considered using special tube of mean (2.5cm) diameter .The detector was placed at (5cm) height and irradiated for 90 days. The chemical etching performed by using (NaOH) solution of 6.25 normality at etching temperature (70C°)for etching period of (7 hrs ).Concentration of radon 222Rn has ranged from (171.237±0.0062) Bq/m3 to (31.982±0.0027) Bq/m3with average value (99.222±0.2476) Bq/m3 while the specific activityof radon has been ranged from (0.471±1.794) Bq/kg to (0.090±7.682) Bq/kg with average value (0.277 1.320)Bq/kgThe results were found to be comparable or lower than similar global reporting data. Accordingly, this area of soil can be considered to have normal levels of natural background radiation.

IMAGING URANIUM DISTRIBUTION ON RAT KIDNEY SECTIONS THROUGH DETECTION OF ALPHA TRACKS USING CR-39 PLASTIC NUCLEAR TRACK DETECTOR.

Uranium is renowned as a global contaminant, and attracts major concern with regards to the health risks involved because its nephrotoxicity. This paper discusses the development of a simple method to identify accumulated regions or localized sites of uranium within kidneys using the CR-39 plastic nuclear track detector. To demonstrate the proposed method, renal cryo-sections (5 μm-t) from Wistar male rats, subcutaneously administered with uranyl acetate (2 mg/kg), were prepared on day one after administration. Concerned sections were subsequently placed on CR-39, stored for 1.25 years, and then etched in a 7 M NaOH solution at 70°C for 3 h. α-tracks were then detected in the form of etch pits, corresponding to uranium, and also the tissue shape and structure were transferred as a roughness on the surface of CR-39. As observed, the proposed method served to facilitate simultaneous detection and identification of localized regions of uranium accumulation within kidneys.

Evidence of Local Concentration of α-Particles from 211At-Labeled Antibodies in Liver Metastasis Tissue.

We investigated the local concentration of α-particles from 211At-labeled trastuzumab antibodies against human epidermal growth factor receptor type 2 antigens in liver metastasis tissue of mice. Methods: Mice carrying metastatic cancer in their liver were injected with 211At-agent. After 12 h, the liver was removed and sliced, and 2 tissue samples of liver tissues without lesions and one containing metastatic lesions were mounted on the CR-39 plastic nuclear track detector. Microscope images of the tissues on the CR-39 were acquired. After irradiation for 31 h, the tissues were removed from the CR-39. A microscope image of α-particle tracks on the CR-39 was acquired after chemical etching. The positions of each tissue sample and the emitted α-particle tracks were adjusted to the same coordinates. Results: The positional distribution of α-particle tracks emitted from 211At was consistent within the tissue. The α-particle tracks were mainly allocated in the tumor region of the tissue. The absorbed dose in individual cells segmented by 10-μm intervals was obtained by the spectroscopic analysis of the linear-energy-transfer spectrum. The concentration efficiency—the track density ratio of α-particle tracks in the necrotized tissue, which was the tumor region, to the normal tissue—was found to be 6.0 ± 0.2. In the tumor region, the high–linear-energy-transfer α-particles deposited a large enough dose to cause lethal damage to the cancer cells. Conclusion: The total absorbed dose ranged from 1 to 7 Gy with a peak at around 2 Gy, which would correspond to a 2–3 times higher biologically equivalent dose because of the high relative biological effectiveness of the α-particles emitted from 211At.

A LiF and BeO TLD based microdosimeter for space radiation risk assessment of astronauts

The ratio of thermoluminescence glow curve area of BeO and LiF dosimeters was found to be proportional to average LET and quality factor (Q) of impinging mixed radiations. Using this phenomenon and widely available Thermoluminescence Dosimeter TLD-700 (7LiF: Mg,Ti) and BeO (Thermolux 995) chips a TLD-Microdosimeter (LiBe-14) emulating a much larger gas-filled Tissue Equivalent Proportional Counter (TEPC) was developed. The TEPC is an essential device of space radiation dosimetry widely used by international space agencies. The LiBe-14 is capable of assessing the LETTissue (5–300 keV/μm), quality factor Q (1–30) and associated dose equivalent H (0.1–1000 mSv) of any mixed radiation fields of interest, including space radiations predominant in Low Earth Orbit (LEO) environment. The TLD microdosimeter was calibrated using the secondary radiation fields produced by bombarding a 25 cm × 25 cm × 35 cm polystyrene phantom with 81, 119, 150, 177, 201 and 231 MeV protons from a Proton Therapy Medical Cyclotron. The TLD pair (BeO/LiF) was attached to the TEPC and placed lateral to the proton beam. The characteristics of space radiation inside the spacecraft are complex. Hence, personal dosimetry of astronauts in the space habitat is performed using “multi-element” dosimeters made of different types of TLD and CR-39 plastic nuclear track detector (PNTD). The TLD and PNTD are used to assess the sparsely (low LET) and densely (high LET) ionising radiation component respectively. This report elucidates the feasibility of LiBe-14 microdosimeter for the estimation of overall dose equivalent and “risk of exposure induced death” (REID) of astronauts working in LEO space stations.

Charge-Changing Cross Sections of 736 A MeV 28Si on Carbon Targets**Supported by the National Natural Science Foundation of China under Grant Nos 11075100, 11347198 and 11565001, and the Shanxi Provincial Science Foundation under Grant No 2011011001-2.

The total and partial charge-changing cross sections of 28Si on carbon targets at 736 and 723 A MeV are studied by CR-39 plastic nuclear track detectors using the HSP-1000 microscope system and the PitFit track measurement software. The values of the total charge-changing cross section are and at 736 and 723 A MeV, respectively. The result is compared with the ones obtained by other experimental and theoretical results. The odd–even effect of the partial charge-changing cross section is observed.

Validating α-particle emission from 211At-labeled antibodies in single cells for cancer radioimmunotherapy using CR-39 plastic nuclear track detectors.

Recently, 211At has received increasing attention as a potential radionuclide for cancer radioimmunotherapy. It is a α-particle emitter, which is extremely effective against malignant cells. We demonstrate a method to verify the efficiency of 211At-labeled trastuzumab antibodies (211At-trastuzumab) against HER2 antigens, which has not been determined for radioimmunotherapy. A CR-39 plastic nuclear detector is used for measuring the position and the linear energy transfer (LET) of individual 211At α- particle tracks. The tracks and 211At-trastuzumab-binding cells were co-visualized by using the geometric information recorded on the CR-39. HER2-positive human gastric cancer cells (NCI-N87), labelled with 211At-trastuzumab, were dropped on the centre of the CR-39 plate. Microscope images of the cells and the corresponding α-tracks acquired by position matching were obtained. In addition, 3.5 cm × 3.5 cm macroscopic images of the whole plate were acquired. The distribution of number of α-particles emitted from single cells suggests that 80% of the 211At-trastuzumab-binding cells emitted α-particles. It also indicates that the α-particles may strike the cells several times along their path. The track-averaged LET of the α-particles is evaluated to be 131 keV/μm. These results will enable quantitative evaluation of delivered doses to target cells, and will be useful for the in vitro assessment of 211At-based radioimmunotherapeutic agents.

Uncertainty evaluation of fluorescent nuclear track detectors (FNTDs) for neutron dose measurements

Fluorescent nuclear track detectors (FNTDs) developed by Landauer Inc. are used as passive dosimeters for neutron dose measurements. Commercial FNTD readers are operated in a track counting mode for low dose neutrons (up to 50 mSv). In order to evaluate the ability of the reader to detect recoil proton tracks, the relationship between track densities of FNTDs and etch pit densities of CR-39 plastic nuclear track detectors (PNTDs) for 241Am-Be neutrons was compared. The relationship was linear in the range of the measured doses from 0.63 mSv to 13.30 mSv. The correlation indicates that both neutron dosimeters similarly detect the recoil proton tracks. The low limit of detection (LLD) using the reader was 1.44 tracks/mm2. In this measurement, the uncertainty of track counting was also evaluated. The relationship between track counts and coefficients of variation (CVs) agreed well with the Poisson distribution. According to the theoretical estimation and the LLD, more than 11.11 counts per 2.08 mm2 are needed to obtain CVs below 30%. In addition, decreasing the CV value was demonstrated by expanding the scan area. Therefore, there is a possibility to improve the measurement accuracy for the LLD with a wider scan area.

Measurement and simulation of secondary neutrons from uniform scanning proton beams in proton radiotherapy

It has long been known that exposure from secondary neutrons in proton radiotherapy can lead to increased risk of secondary cancers later in a patient's life. The assessment of secondary neutrons is, therefore, important to the overall quality of the treatment. In this study, we investigated the neutron dose equivalent outside of the primary proton treatment field as a function of distance to the isocenter and angle relative to the central axis. CR-39 plastic nuclear track detectors (PNTD) were exposed to uniform scanning proton beams at the ProCure Proton Therapy Center, Oklahoma City, OK. The contribution of neutron dose equivalent was investigated for two different experimental configurations, namely hollow-phantom, and cylindrical-phantom. Numerical simulations were performed using the Monte Carlo code FLUKA for similar experimental conditions. Three proton beams of range 5 cm, 18 cm, and 32 cm with 4 cm modulation width, 38 cm snout to phantom surface distance and a 5 cm diameter aperture were used for the study. The measured ratio of neutron dose equivalent to the primary proton dose (H/D) fell off with distance and ranged from 2.1 mSv/Gy to 50.1 mSv/Gy. The contribution of internal neutrons to the overall neutron dose equivalent were found to be up to 64% near the treatment field.

A performance test of a new high-surface-quality and high-sensitivity CR-39 plastic nuclear track detector – TechnoTrak

We have studied the performance of a newly-commercialized CR-39 plastic nuclear track detector (PNTD), “TechnoTrak”, in energetic heavy ion measurements. The advantages of TechnoTrak are derived from its use of a purified CR-39 monomer to improve surface quality combined with an antioxidant to improve sensitivity to low-linear-energy-transfer (LET) particles. We irradiated these detectors with various heavy ions (from protons to krypton) with various energies (30–500MeV/u) at the heavy ion accelerator facilities in the National Institute of Radiological Sciences (NIRS). The surface roughness after chemical etching was improved to be 59% of that of the conventional high-sensitivity CR-39 detector (HARZLAS/TD-1). The detectable dynamic range of LET was found to be 3.5–600keV/μm. The LET and charge resolutions for three ions tested ranged from 5.1% to 1.5% and 0.14 to 0.22c.u. (charge unit), respectively, in the LET range of 17–230keV/μm, which represents an improvement over conventional products (HARZLAS/TD-1 and BARYOTRAK). A correction factor for the angular dependence was determined for correcting the LET spectrum in an isotropic radiation field. We have demonstrated the potential of TechnoTrak, with its two key features of high surface quality and high sensitivity to low-LET particles, to improve automatic analysis protocols in radiation dosimetry and various other radiological applications.

Fragmentation cross section of 800 A · MeV silicon ions on polyethylene target

The total charge-changing cross sections and the partial cross sections of projectile fragment production of the fragmentation of silicon ions on polyethylene target at 800 A · MeV are measured using CR-39 plastic nuclear track detector. The total charge-changing cross sections of silicon ions on polyethylene targets at 800 A · MeV is 761 ± 24 mb, which agree well with the prediction of Bradt-Peters semi-empirical formula using parameter r0 = 1.31fm and b = 0.94 within experimental errors. The obvious even-odd effect is observed for the partial cross sections in present investigation.

Optical and chemical behaviors of CR-39 and Makrofol plastics under low-energy electron beam irradiation

In this study, CR-39 and Makrofol plastic nuclear track detectors were irradiated with low-energy electron beams to study the effect of the induced changes on their optical and chemical properties. Surface chemical changes were recorded by Fourier transform infrared (FTIR) spectroscopy, which showed successive degradation and crosslinking for CR-39 and decomposition for Makrofol. The optical band gap was determined by UV–vis spectroscopy. Also, the parameters of carbon cluster formation and disordering (Urbach’s energy) occurring on plastic surfaces were examined. The intrinsic viscosity changes were investigated as well. As a result, low-energy electron beams were found to be useful for the control of many properties of the surfaces of the investigated detectors.

Fragmentation cross sections of 788A MeV 28Si on carbon and polyethylene targets

The total charge-changing cross sections and the partial cross sections of silicon ions on carbon and polyethylene targets are studied at 788 A MeV by using CR-39 plastic nuclear track detectors. The results are compared with other experimental and theoretical results. The obvious even-odd effect for partial cross sections is observed.