Track Registration Efficiency Research Articles

Alpha track registration and revelation in CR-39 using new etching method for ultratrace alpha radioactivity quantification in solution media

Abstract A CR-39 based method was developed for measuring the ultra-trace alpha radio activities in aqueous samples having curie levels of γ/β-radio activities. The chemical etching method was optimized to reveal the alpha tracks in CR-39. This new chemical etching method involved the use of a phase transfer catalyst tetraethylammonium bromide which reduced the track revelation induction time without deteriorating the track-etch parameters. The alpha track-etch parameters such as bulk-etch rate, track-etch rate, induction time, and the critical angle of alpha track registration were measured at 60 and 70 °C, with and without using a phase transfer catalyst in the chemical etching for the comparison and optimization. The track registration efficiency of CR-39 in the solution medium was measured using the samples having known alpha activity of mixPu, and value obtained was found to be (4.42 ± 0.12) × 10−4 cm. The registration efficiency value thus obtained was corroborated with the expected efficiency expected from the calculated range of alpha particles in the solution. This CR-39 based method was employed to quantify the alpha activity, as low as 0.2 Bq mL−1, in the aqueous radiopharmaceutical samples having the curie levels of γ/β radio activities.

Impact of infrared radiation on track etching parameters of Lexan track detector to fission fragments from 252Cf source

In this research work, the impact of infrared (IR) radiation on the etching parameters like bulk etch rate VB, track etch rate VT, Sensitivity S, Critical angle of etching θC and track registration efficiency η of Lexan track detector, irradiated to fission fragments from 252Cf source, were investigated. The changes in etching parameters due to infrared radiation for 0, 12 and 24 h at different temperatures (328–348 K) are discussed based on chain scission and cross-linking mechanisms. Bulk and track etch rates increase with infrared radiation in case of post-exposed as compared to un-exposed while sensitivity slightly decreases for 12 h exposure with infrared radiation but slightly increases for 24 h exposure with infrared radiation as compared to un-exposed. On the other hand, bulk and track etch rates decrease with infrared radiation in case of pre-exposed as compared to un-exposed while sensitivity slightly increases. Critical angles increase and track registration efficiency decreases with etching temperatures. Activation energies for bulk and track etching rates have been determined by fitting Arrhenius equation to the experimental data of bulk and track etch rates which show a decrease in bulk activation energies in case of post-exposed but slightly increase in case of pre-exposed as compared to un-exposed Lexan track detectors. Track activation energies show the same trend as for bulk etch rate.

Track revelation and optical properties of pentaerythritol tetrakis (allyl carbonate) plastic for application as nuclear track detector: effects of gamma radiations

ABSTRACTThe etching conditions of an indigenously prepared thin film of pentaerythritol tetrakis(allyl carbonate) (PETAC) were standardised for the use as a nuclear track detector. The optimum etching times in 6 N NaOH at 70°C for the appearance of fission and alpha tracks recorded in this detector from a 252Cf solid source were found to be 30 min and 1.50 h, respectively. The experimentally determined values for the bulk and track-etch rates for this detector in 6 N NaOH at 70°C were found to be 1.7 ± 0.1 and 88.4 ± 10.7 µm/h, respectively. From these results, the important track etching properties such as the critical angle of etching, the sensitivity and the fission track registration efficiency were calculated and compared with the commercially available detectors. The activation energy value for bulk etching calculated by applying Arrhenius equation to the bulk etch rates of the detector determined at different etching temperatures was found to be 0.86 ± 0.02 eV. This compares very well with the value of about 1.0 eV reported for most commonly used track detectors. The effects of gamma irradiation on this new detector in the dose range of 200–1000 kGy have also been studied using bulk etch rate technique. The activation energy values for bulk etching calculated from bulk etch rates measurements at different temperatures were found to decrease with the increase in gamma dose indicating scission of the detector due to gamma irradiation. The optical band gap of this detector was also determined using UV–visible spectrometry and the value was found to be 4.37 ± 0.05 eV.

Monte Carlo simulation experiments on box-type radon dosimeter

Epidemiological studies show that inhalation of radon gas (222Rn) may be carcinogenic especially to mine workers, people living in closed indoor energy conserved environments and underground dwellers. It is, therefore, of paramount importance to measure the 222Rn concentrations (Bq/m3) in indoors environments. For this purpose, box-type passive radon dosimeters employing ion track detector like CR-39 are widely used. Fraction of the number of radon alphas emitted in the volume of the box type dosimeter resulting in latent track formation on CR-39 is the latent track registration efficiency. Latent track registration efficiency is ultimately required to evaluate the radon concentration which consequently determines the effective dose and the radiological hazards.In this research, Monte Carlo simulation experiments were carried out to study the alpha latent track registration efficiency for box type radon dosimeter as a function of dosimeter’s dimensions and range of alpha particles in air. Two different self developed Monte Carlo simulation techniques were employed namely: (a) Surface ratio (SURA) method and (b) Ray hitting (RAHI) method.Monte Carlo simulation experiments revealed that there are two types of efficiencies i.e. intrinsic efficiency (ηint) and alpha hit efficiency (ηhit). The ηint depends upon only on the dimensions of the dosimeter and ηhit depends both upon dimensions of the dosimeter and range of the alpha particles. The total latent track registration efficiency is the product of both intrinsic and hit efficiencies. It has been concluded that if diagonal length of box type dosimeter is kept smaller than the range of alpha particle then hit efficiency is achieved as 100%. Nevertheless the intrinsic efficiency keeps playing its role.The Monte Carlo simulation experimental results have been found helpful to understand the intricate track registration mechanisms in the box type dosimeter. This paper explains that how radon concentration from the experimentally obtained etched track density can be obtained. The program based on RAHI method is also given in this paper.

A new method for detection of alpha particles in 1 mm thick polycarbonate detectors using 50 Hz – HV ECE method

Recent studies in our laboratory have proved that electrochemical etching (ECE) of polycarbonate track detectors (PCTD) under 50 Hz – high voltage (HV) field conditions has potentials for time-integrated heavy charged particle detection and dosimetry applications. The rationale in the study is the ECE process of alpha particle tracks in 1 mm thick PCTDs by a 50 Hz – HV generator at optimized ECE conditions. Tracks of 3.2 MeV alpha particles from a collimated beam of an 241Am source degraded in air and background tracks were registered. The effects of HV and ECE duration on alpha track registration efficiency and track diameters were studied for 3 sets of 50 Hz – 4, 5 and 6 kV field conditions in a PEW solution (potassium hydroxide, ethanol and water) at 26 °C. The optimized ECE conditions obtained at this stage of development for 1 mm thick PCTDs are 50 Hz – 4 kV in PEW solution at 26 °C for 10 h. Alpha track registration efficiency at 3.2 MeV is about 30% with 37 ± 6 μm mean track diameter. The mean background track density at the above stated optimized conditions is about 571 ± 16 tracks.cm−2 with a mean diameter of 65 ± 5 μm. All tracks are observable by the unaided eyes. The mean background track diameter is near two times larger than that of alpha particle tracks at the optimum conditions applied; they are easily distinguished against each other. This high background track density while at this stage of development seems a drawback for low dose and low fluence particle applications, it has minimal effects on high fluence ion detection applications. The simple 50 Hz – HV generator used proved to be convenient for efficient alpha track amplifications. Studies are underway for improvement of the method in particular for reducing background track density.

Use of fission track analysis technique for the determination of MicroBequerel level of 239Pu in urine samples from radiation workers handling MOX fuel

Fission track analysis (FTA) technique for the determination of (239)Pu excreted through urine has been standardized using blank samples, tracer and (239)Pu spikes. Double stage anion exchange separation protocol has been applied and an average radiochemical recovery of (239)Pu of 18% was obtained. An average track registration efficiency of 11 tracks per μBq of (239)Pu, irradiated to 0.35×10(17) neutron fluence was established. Reagent blank urine samples from 11 controlled subjects were analyzed by FTA and an average of 149±14 tracks was obtained. Minimum detectable activity of 34μBqL(-1) of urine sample was obtained and will be useful for monitoring chronic exposure cases handling MOX fuel.

Study of gamma irradiation effects on the etching and optical properties of CR-39 solid state nuclear track detector and its application to uranium assay in soil samples

The gamma irradiation effects in the dose range of 2.5–43.0 Mrad on the etching and optical characteristics of CR-39 solid state nuclear track detector (SSNTD) have been studied by using etching and UV–Visible spectroscopic techniques. From the measured bulk etch rates at different temperatures, the activation energies for bulk etching at different doses have also been determined. It is seen that the bulk etch rates increase and the activation energies for bulk etching decrease with the increase in gamma dose. The optical band gaps of the unirradiated and the gamma -irradiated detectors determined from the UV–Visible spectra were found to decrease with the increase in gamma dose. These results have been explained on the basis of scission of the detector due to gamma irradiation. The present studies can be used for the estimation of gamma dose in the range of 2.5–43.0 Mrad and can also be used for estimating track registration efficiency in the presence of gamma dose. The CR-39 detector has also been applied for the assay of uranium in some soil samples of Jammu city.

Estimation of track registration efficiency in solution medium and study of gamma irradiation effects on the bulk-etch rate and the activation energy for bulk etching of CR-39 (DOP) solid state nuclear track detector

The fission track registration efficiency of diethylene glycol bis allyl carbonate (dioctyl phthalate doped) [CR-39 (DOP)] solid state nuclear track detector (SSNTD) in solution medium (Kwet) has been experimentally determined and is found to be (9.7 ± 0.5) × 10−4 cm. This is in good agreement with the values of other SSNTDs. The gamma irradiation effects in the dose range of 50.0–220.0 kGy on the bulk etch rate, Vb and the activation energy for bulk etching, E of this solid state nuclear track detector (SSNTD) have also been studied. It is observed that the bulk etch rates increase and the activation energies for bulk etching decrease with the increase in gamma dose. These results have been explained on the basis of scission of the detector due to gamma irradiation.

Determination of track registration efficiency and radiation chemical yield for loss of ester bonds due to gamma rays in Cellulose Acetate Butyrate (CAB) nuclear track detector

The fission track registration efficiency of an indigenously prepared Cellulose Acetate Butyrate (CAB) solid state nuclear track detector (SSNTD) has been determined and is found to be (0.89 ± 0.04). Radiation chemical yield, G-value for loss of ester bonds in this detector exposed to gamma rays from a Co-60 source has also been determined by FT-IR spectrometry. The amount of ester bonds lost due to the exposure was estimated from the change in absorbance of C=O and C–O–C bonds with the gamma dose. The G-value for breaking of ester bonds in CAB detector is found to be about 37/100 eV.

Study of fission track registration efficiency of γ-irradiated polyester track detector in solution medium

The fission track registration efficiency (Kwet) of the Garware polyester track (GPF) detector in solution has been determined with respect to the Lexan detector whose Kwet is very well known in the literature. The Kwet is found to be (1.2 ± 0.1) 10−3 cm. The track registration efficiency of the GPF detector in solution is better than the efficiencies of other nuclear track detectors reported in the literature. This implies that the threshold energies for track registration are different for different detectors and that GPF detector has a lower threshold-energy value. The effects of gamma irradiation in the dose range of 5–51 Mrad on the fission track registration efficiency (Kwet) of this track detector from the solution medium are also investigated. The results show that the Kwet values for the gamma-irradiated detectors in the above dose range in 2M HNO3 solution medium decreases by ∼7–15%. The changes induced in the gamma-irradiated detectors as a function of gamma dose have also been studied by bulk-etch rate measurements.

Study of a deposition-based direct thoron progeny sensor (DTPS) technique for estimating equilibrium equivalent thoron concentration (EETC) in indoor environment

A study has been carried out to examine the suitability of a passive, deposition-based technique for estimating the time-integrated equilibrium equivalent thoron concentration (EETC) in indoor environment using a direct thoron progeny sensor (DTPS). DTPS is an absorber-mounted LR-115-type nuclear track detector tuned to respond only to the 8.78 MeV alpha particles emitted from the deposited activity of 212Po on the absorber surface. The study has been carried out in two steps, the first step comprising the estimation of track registration efficiency ( η ) and the second step comprising the estimation of effective deposition velocity of thoron progeny aerosols on the detector surface in natural and laboratory environments. The track registration efficiency is found to be 8.3% for 212Po and less than 0.02% for all other alpha emitters including 222Rn (radon) progeny, thereby enabling a precise discrimination of thoron progeny. The deposition velocity of thoron progeny aerosols on DTPS surface has been measured in conjunction with active air sampling techniques for different orientations of the deposition surface. The geometric mean deposition velocity was found to be 0.077 m h - 1 having a narrow spread (geometric standard deviation of 1.35). Upon combining these factors, the overall sensitivity factor is estimated to be 0.94 Tr cm - 2 d - 1 / EETC ( Bq m - 3 ) , which indicates ∼ 45 times higher sensitivity as compared with conventional bare detector techniques (which register alpha particles emitted directly from air). The results obtained have been compared with currently used aerosol deposition models and progeny equilibrium models by using the aerosol number size and progeny activity distributions measured with scanning mobility particle sizer (SMPS) and low-pressure cascade impactor, respectively. The results are in good agreement with each other. A sensitivity analysis of the response characteristics of DTPS with respect to room ventilation rate and aerosol concentrations has been carried out to assess the variability of the sensitivity factor in the context of indoor dosimetry. The results are further discussed.

Study of the anode self-trigger ability of the ME1/1 CMS Endcap Cathode Strip Chamber

The influence of the high background rates on the Cathode Strip Chamber (CSC) anode trigger ability has been studied. The investigation has been made with a P3 prototype of the CSC of ME1/1 Endcap muon station of the CMS experiment (CERN). The work has been done at the Gamma Irradiation Facility (GIF, CERN). P3 has been installed at the SPS X5c muon beam line in a background field of 137Cs source. The CSC timing resolution and the track registration efficiency as a function of gamma rate are presented.

Neutron-irradiation effects on track etching characteristics of polyester nuclear track detector

The effects of reactor neutron irradiation on the etching characteristics of a locally available Garware polyester film have been studied. The effects in the neutron fluence range of 4.57×1015–1.83×1016 n/cm2 on the fission track registration efficiency and the bulk etch rate are investigated. From the results, it is found that the bulk etch rates increase with the increase in neutron fluence. The increase in etch rates can be explained on the basis of scission of the detector due to neutron irradiation which enhances the dissolution rates. From the measured bulk etch rates at different temperatures, the activation energies for bulk etching at different values of neutron fluence have also been determined. The changes induced by neutron irradiation in the polyester detector have also been studied by UV-visible spectroscopic technique. The neutron irradiation enhances the UV absorbance of the detector, which is a direct consequence of the formation of new chemical species due to scission of the detector.

Spontaneous fission decay constant of 238U determined by SSNTD method using CR-39 and DAP plates

This paper presents a simple method for determining the spontaneous fission decay constant ( λ f) of 238U using a combination of CR-39 and diallyl phthalate (DAP) plates as solid-state nuclear track detectors (SSNTD). In this method, thin U-sources were prepared by depositing natural uranium onto 10-cm 2 stainless steel plates. Alpha-particle tracks originated from 238U were detected in the 2π geometry of CR-39 detectors that had been attached to U-sources for 120–426 min. Spontaneous fission tracks, on the other hand, were detected using DAP detectors in the same geometry that had been attached to U-sources for 50–238 days. Based on precise measurements of bulk-etching and track-etching rates of the two detectors, track registration efficiencies and critical angles were determined to be 0.740±0.072 and 15.1° for CR-39, and 0.995±0.035 and 0.26° for DAP, respectively. Using these correction values and specific activities (or track densities) measured for each detector, a mean value of λ f was calculated to be (8.51±0.18)×10 −17 yr −1 in proportion to the alpha emission decay constant of 1.55±1.25×10 −10 yr −1.

Absolute measurements of the uranium concentration in thick samples using fission-track detectors

We propose an improved equation for calculating the uranium concentration in thick samples based on induced fission-track counts in an external detector that takes into consideration (1) the fission-fragment ranges in the sample and external detector, (2) the etchable track length and (3) the track counting efficiency in the external detector. The values of these parameters have been determined by calculation and experiment and are shown to have a significant effect on the calculated uranium concentrations. The new equation was tested by calculating the uranium concentrations in standard uranium glasses (CN-5; IRMM-540R) and apatite samples (Durango; horse tooth) in which the uranium content was also determined with independent methods (INAA; ENAA; TIMS). The results show that: (1) accurate measurements with the fission-track method are feasible within a broad range of uranium concentrations and (2) uranium determinations based on standards are only accurate if the standard and sample are made of the same material. Because the absolute fission-tack dating method is also based on accurate thermal neutron fluence measurements and similar correction factors for the track registration and counting efficiencies, this study provides a strong endorsement for the fact that absolute fission-track ages are accurate.

Gamma-irradiation on a Tuffak polycarbonate solid state nuclear track detector

Abstract The effects of gamma-irradiation at a dose range of 5-56 Mrad on the fission track registration efficiency of the Tuffak polycarbonate track detector from dry (K dry) as well as the solution media (K wet) are investigated. Fission tracks were recorded in the gamma-irradiated detectors along with the unirradiated ones by an electrodeposited source of 252Cf and also separately from a 252Cf solution. The fission track registration efficiencies for the irradiated detectors were determined in comparison with those of the unirradiated detectors. The results show that while the K dry values for the irradiated detectors decrease by about 2-10%, the corresponding K wet values decrease by about 3-20% as compared to unirradiated detectors . Further, the bulk etch rates were found to increase with the increase in gamma dose. The changes induced in the gamma-irradiated detectors as a function of dose have been studied also by thermogravimetry (TG).

Studies of CR-39 etch rates

A series of chemical etching experiments have been carried out on CR-39 detectors irradiated with fission fragments of 252Cf to study the bulk and track etching characteristics. Experimental data has been analyzed to find out important track etch parameters. Both bulk and track etch rates are found to follow the Arrhenius equation which gives the variation of etch rate with temperature for a specific set of etching conditions. Activation energies for bulk and track etching have been determined by fitting Arrhenius equation to the experimental data. Other track etch parameters, e.g. critical angle of etching and track registration efficiency have also been determined using experimental data. Track etch parameters depend on properties of incident ion and etching conditions. Results describing the dependence of track etch parameters on etching conditions have been presented. These results are useful in the interpretation of track data.

Studying the response of CR-39 detectors using the Monte Carlo technique

A computer code based on Monte Carlo technique has been developed to study the response of CR-39 detectors to fast neutrons. The code is written in the C++ programming language and uses a tested pseudo random number generator and neutron cross-section data library ENDF/B-VI. H, C and O recoils as well as nuclear reactions have also been taken into account. The calculated track registration efficiency of CR-39 is found to be dependent on the neutron energy and detector thickness.

Measurement of fast neutron induced fission cross section of thorium using Lexan plastic track detector

Fission-track registration characteristics of Lexan solid state nuclear track detectors have been used to measure the fast neutron induced fission cross section of232Th. The fast neutrons (≅14.2MeV) were produced with the help of an AN-400 model Van-de-Graaff accelerator at Banaras Hindu University laboratory using3H(2H,n)4He reaction and were used to irradiate the fissile target deposited on the plastic detector. The track densityT, registered on the plastic detector is related to the fission cross sectionσ f, through the relationT=knσ fot wheren is the number of fissile atoms per cm2 in the deposit, o is the neutron flux,k is fission track registration efficiency andt is the time of irradiation. The fission cross sectionσ f of232Th, relative to the well measured fission cross section of238U, was found to be 0.36±0.04 barn.

Spin coating technique for the preparation of thin nitrocellulose films for solid state nuclear track detection

Thin and uniform nitrocellulose (CN) films were prepared over a supporting polyester film by the spin coating technique. The paper describes the first systematic approach to the application of the spin coating technique for the preparation of thin nitrocellulose films of required thickness and discusses the effects of solvent, concentration and viscosity of the nitrocellulose solution on the characteristics of the film. The method was used to prepare composite nitrocellulose-polyester films which can be used as solid state nuclear track detectors (SSNTDs). The etching conditions were optimized and the films were found to be comparable with the commercially available LR 115 Type II films with respect to background track density and the alpha track registration efficiency.