CR-39 Plastic Track Detectors Research Articles

Dosimetry of 40 and 70 MeV/n 16O beams

Using CR-39 plastic track detectors the range values of 16O ions at two different energies (initially in the beam line, 39.97 MeV/n and 69.98 MeV/n) were measured after escaping the beam pipe and found to be (3050 ± 40) μm and (8210 ± 90) μm, respectively. The longitudinal and projected angular spread of oxygen ions of an initial energy of 69.98 MeV/n in the region of the Bragg peak was derived from the measured geometrical parameters of tracks. Based on a calibration curve (etch rate ratio vs total linear energy transfer in CR-39) and the measured track length distribution at the range end of oxygen ions, the complete depth dose profile of a 67.7 MeV/n 16O beam in CR-39 (plateau, extended Bragg peak and residual ionization caused by projectile like fragments) was obtained.

Experimental and simulation study of neutron dosimetry at various neutron energies

A Monte Carlo Neutron Photon (MCNP) transport code has been employed to simulate CR-39 plastic track detector as neutron dosimeter at various neutron energies. In each simulation a monoenergetic neutron source of a particular energy was embedded in the center of a sphere made of CR-39. Surrounding the source there were concentric shells of 2 μm CR-39 track detectors. The code, MCNP, was run on personal computer for 7.5×10 6 histories. The number of proton recoils in each shell of 2 μm of CR-39 were determined. The simulation results show that apart from proton recoils (for E n > 1.0 MeV), about 50% recoils are due to heavy charged particles i.e. Oxygen and Carbon in CR-39. This indicates that etched tracks are not only due to recoil of protons but also due to recoil of heavy charged particles. The upper limits of the track registration efficiencies have been determined as a function of neutron energies. These simulation results have been experimentally verified using CR-39 track detectors at various known energies of neutrons. The proton and heavy charged particle recoil tracks in CR-39 were made visible by etching in NaOH solution, at 70±1°C for 1.75 hours.

Measurement of LET distribution and dose equivalent on board the space shuttle STS-65

Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called “Real-time Radiation Monitoring Device (RRMD)” utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 μSv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit for space radiation with a small inclination (28.5°) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15–200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks.

Intercomparison of experimental and theoretical ranges of heavy ions in plastic track detectors

In the present study, CR-39 and Lexan polycarbonate plastic track detectors have been exposed to various heavy ion beams, i.e. 238U, 208Pb, 197Au, 139La, 132Xe and 93Nb (energy range from 5.6 to 18.0 MeV/u), from the UNILAC accelerator at GSI, Darmstadt. After exposure, the irradiated samples were etched under optimum etching conditions. The total etchable ranges of these heavy ions have been determined experimentally using a Carl Zeiss binocular microscope. In order to check the validity of the various stopping power and range formulations in this energy range, the experimentally determined range values have been compared with theoretically computed values from the Benton and Henke [Nucl. Instr. and Meth. 67 (1969) 87], Mukherjee and Nayak [Nucl. Instr. and Meth. 159 (1979) 421], Ziegler et al. [Stopping power and range of ions in solids, vol. 1 (Pergamon, New York, 1985); Nucl. Instr. and Meth. B 35 (1988) 215] and Hubert et al. [Nucl. Instr. and Meth. B 36 (1989) 357] formulations.

The effect of environmental treatment on the track response of the CR-39 plastic detector

The bulk-etch rate has been investigated for samples of CR-39 plastic track detectors unannealed and annealed at 90, 110, 130 and 150 °C in dry air after α-particle irradiation. It was found that the bulk-etch rate of unannealed CR-39 has a constant value with dissolved layer thickness from the detector surface. However, it seemed to increase as the annealing time and temperature for the annealed sample increase. The sensitivity V ( ≡ V T V B ) of CR-39 was determined after annealing in dry air at temperatures 90, 110 and 130 °C. The results showed that there is a decrease in the sensitivity of the detector as the annealing time increases. The response of the CR-39 track detector, V( R), has been determined in environmental oxygen, nitrogen and also under vacuum. The results obtained in this study confirmed previous reports that the environmental oxygen causes a remarkable increase in the sensitivity of CR-39. The environmental nitrogen and the evacuation have nearly the same effect on the response of CR-39 and the values of the sensitivity are about 5% less than the corresponding values measured in air under 1 atm pressure.

Alpha particle radiography with the CR-39 nuclear track detector

This work studies the alpha particle radiography technique, in conjunction with the CR-39 plastic track detector. The irradiations were made in the CV-28 cyclotron at IEN/CNEN/RJ, using a 7 MeV/nucleon alpha particle beam. All etches were performed by using a 6.25 N NaOH solution, at 70°C. The best etch time to obtain radiographs was determined. A calibration curve (Gray Levels x Energy Loss)was obtained, so as to permit a quantitative interpretation of the images. Its behavior was checked against several experiments with other energy degrading materials, namely, aluminum, mylar and CR-39 itself. The error propagation on energy resolution was also investigated. Several radiographs of in vitro biological specimens were obtained. The results showed the potential capability of this technique for studies in paleontology.

Passive track detectors for radon determination in the indoor environment

Solid-state nuclear track detectors are increasingly being used for the measurement of time-integrated radon levels in dwellings under different conditions. This paper presents the results of Rn measurements in the indoor atmosphere of Manzini Town and the University of Swaziland campus using CR-39 plastic track detectors. The results show that radon concentrations in the indoor atmosphere vary with the ventilation conditions. The books present in a library can also serve as Rn emitters and thus may increase health risks. The equilibrium factor ( F) and the effective dose equivalent ( Hg) were determined. The recorded values lie below the international guidelines.

Estimation of dose equivalent in STS-47 by a combination of TLDS and CR-39

Using the LET distribution obtained by CR-39 plastic track detectors and the total absorbed dose obtained by TLDs, whose response for relativistic heavy ions is proportional to the absorbed dose, the dose equivalents at various locations inside the Space Shuttle (STS-47) have been estimated. The results show a large difference in the effective quality factor compared with the results obtained from a tissue equivalent proportional counter. The reason for this discrepancy is discussed.

Natural radiation background of the Leninabad region in Tadjikistan

The -ray and activity background territory was measured with electronic and CR-39 plastic track detectors for a number of locations.

136Xe and 197Au ion track registration response in CR-39 and CR-39 (DOP) detectors

Samples of CR-39 and CR-39 (DOP) plastic track detectors were exposed to 136Xe ions (11.56 MeV n ) and 197Au ions (13.92 MeV n ) at an angle of 45° from UNILAC, GSI, Darmstadt, Germany, to study the track registration parameters, viz. variation of track length ( L) with etching temperature (55°, 65°, 70° and 80°C) using 6N NaOH as etchant, and bulk and track etch rates ( V G and V T ) and respective activation energies ( E G and E T ). It is observed that the slope ( dL dV T ) of the c etching temperature under given etching conditions and the relative track etch rate decreases with increasing temperature. In the temperature range used in the present experiment, the variations of etching rates V G and V T with temperature were found to be exponential and followed the Arrhenius equation. The activation energies for bulk and track etching have been calculated for these ions in both detectors.

CR-39 plastic track detector for field investigations ofa-active soils

CR-39 plastic track detector for field investigations ofa-active soils

Interaction of 15.9 MeV/u 197Au ions with natAu and 209Bi as targets on CR-39 plastic track detectors

A 2π -geometry has been employed for studying the interactions of 15.9 MeV/u 197Au ions with natAu and 209Bi targets using CR-39 detectors. The detectors have been scanned for binary and multiprong reaction products produced as a result of the projectile target interaction. The partial and total reaction cross sections have been measured and compared with the theoretical values. Attempts have been made to separate the elastic and inelastic events from the total set of two prong events.

Target fragmentation in 3.65 GeV 12C + 208Pb reaction

The light fragment emission from 3.65 A GeV 12C+208Pb reaction was investigated by using CR-39 plastic track detector. It was observed that the light fragments can be produced by the two different mechanisms.

High-energy neutron spectrometry with CR-39 SSNTDs

Spectrometric measurements of high-energy neutrons have been made, employing CR-39 plastic track detector. Triple-α tracks, produced by the reaction 12C(n,n′)3α have been used to measure the energy and angular distributions of the three α-prongs. Applying the energy and momentum conservation rules, the energy spectra of neutrons have been obtained.

Measurement of radon exhalation rate from some building materials

Passive integrating CR-39 plastic track detectors were used to measure the radon exhalation rate from building materials used in our region. It was found that the radon exhalation rate varies from 12.6 to 169 mBq m -2 h -1 in 10 different building materials.

An evaluation of the radical life-time in CR-39 track detectors outgassed under vacuum

The property of latent track registration for CR-39 plastic track detectors outgassed in vacuum has been examined. It was found that the sensitivity of CR-39 detectors recovered partially when exposed to air after α-particle irradiation. The life-time of radicals produced by the irradiation could be evaluated from the dependence of recovery on the time between irradiation and air exposure. At least two components of radicals with life-times of about 40 min and a few min were found to be formed.

Sensitivity study of CR-39 plastic track detectors

Abstract With the goal of increasing the sensitivity of CR-39 plastic track-recording detectors, samples of plastics that contain antioxidant additives were made by Tastrak (Bristol, U.K.) and evaluated by us with a Bevalac exposure at the University of California, Berkeley. The results show that CR-39 containing 100 ppm Naugard additives but no plasticizer DOS has higher sensitivity than standard CR-39 plastic in the tested range of Z eff /β = 7–12. However, no nuclei with Z ≦5 were recorded in any of the samples, indicating that the detection threshold of the calibrated CR-39 samples ( Z eff /β) threshold was ≧6.1.

Plastic nuclear track detection methods for estimation of thorium to uranium ratio in thick natural materials

Two methods have been presented to estimate thorium to uranium ratios in thick samples, assuming that the thorium and uranium are in secular equilibrium. The registration sensitivities of CR-39 and LR-115 solid state nuclear track detectors exposed in close contact with the sample, have been calculated. The registration sensitivity of a CR-39 plastic track detector for non-contact alpha-autoradiography at different absorber thicknesses has also been calculated. The registration sensitivity is expressed in α-tracks cm −2 per 30 days exposure for one ppm parent nuclide concentration in the sample.

Intermediate mass fragment production in interaction 40Ar+208Pb at E/A=19.6 MeV.

The intermediate mass fragment production in the interaction {sup 40}Ar+{sup 208}Pb at {ital E}/{ital A}=19.6 MeV was studied using a CR-39 plastic track detector. Exit channels with up to three intermediate mass fragments were observed. It seems that events having at least one intermediate mass fragment originate from central collisions. The relative velocity correlation functions were determined for these events and discussed.

Inactivation of C3H 10T1/2 cells by monoenergetic high LET alpha-particles.

Inactivation of mouse C3H 10T1/2 cells in plateau-phase (7.8 x 10(4) cells/cm2) was studied by using alpha-particles from the irradiation facility installed for radiobiological experiments at the 3 MV Tandem accelerator, University of Naples. Silicon detectors and CR39 plastic track detectors were employed for dosimetric purposes. The cells were exposed to high LET monoenergetic alpha-particles (energy of 1.8 MeV at the centre of the cell nucleus, track-averaged LET of 177 keV/micron and dose-rate of 1.1 Gy/min) and low-LET 80 kVp X-rays. The X-ray survival curve showed a significant shoulder (alpha/beta = 9 Gy) while the survival curve for alpha-particles was close to exponential. The mean lethal dose of alpha-particles was 0.77 +/- 0.02 Gy and the RBE was 5.2 at 80% survival and 3.0 at 5% survival. Survival of exponentially growing cells (2 x 10(4) cells/cm2) following irradiation with the alpha-particle beam is also reported. The nuclear areas of 10T1/2 cells were measured as 299 +/- 9 micron 2 and 250 +/- 8 micron 2 for cells in log phase and plateau phase, respectively. The inactivation cross-section, obtained from the mean lethal dose, was 34 micron 2 and 37 micron 2 for cells in log phase and plateau phase, respectively. These values appear to be the maximum measured values for the inactivation cross-section of 10T1/2 cells as a function of the alpha-particle LET. This saturation cross-section is very similar to the saturation values reported in the literature for other mammalian cell lines.