The UV-Vis spectroscopy has been found suitable for fluence measurement with CR-39 track detector when the track counting with optical microscope is difficult due to huge overlapping of tracks. In this work, the optimum etching duration has been determined for alpha particle measurement using CR-39 as detector and UV-Vis spectroscopy as characterisation technique. For this purpose, CR-39 detectors were irradiated to alpha particles with known fluence followed by stepwise chemical etching. The track images were captured as well as UV-Vis spectra were recorded after etching. The transmission values in the UV-Vis spectra were found to be decreasing with etching time and fluence. The optical absorbance at a particular wavelength, i.e., 600 nm was found to increase with the fluence. The saturation effect was observed at higher fluence when the etching time was above 4 h. The optimum etching time was determined to be 4 h based on the linear response in wide fluence range from 8.56 x 10(4) to 1.93 x 10(7) cm(-2). Linear relation for the absorbance (at 600 nm) and fluence was derived which can be used as multiplication factor to estimate the fluence in the range of 8.56 x 10(4)-1.93 x 10(7) cm(-2), after performing 4 h etching.

Neutron dosimetry and spectrometry with a Ta target is of concern in an accelerator environment considering its enormous use in a proton accelerator. The Ta target has a unique advantage considering the generation of short half lived radionuclides upon interaction with protons. This advantage extends its use as the beam stopping material at various locations of an accelerator. However, this target has a varied range of reactions to produce neutrons and prompt gammas depending on proton energies. So in the present work, the neutron spectra were generated at various incident proton energies and neutron ambient dose equivalents were estimated close to the target projectile interaction at 90°with respect to the incident beam direction. A comparison of the spectral nature and doses were also done with measurements made by our earlier studies carried out at 0°. The comparison clearly showed that, apart from an increase in the low energy neutron yields at 90°, the overall yield distribution remains similar at both 0°and 90°angles with respect to the incoming beam direction. The ratio of the ambient neutron dose equivalent is found to reduce by a factor of 3–4 at 90°compared to 0°over the entire incident proton energy range. So, the dose equivalent ratio at two angles can be considered as independent of the incident projectile energy.

Positive ion accelerators have gamma and neutrons as prompt radiation. Though neutron yield is less but due to high energy and penetrability it becomes of concern for radiation protection [1]. The information however is important for radiation protection practices. In radiation therapy, the secondary particles generated during the treatment are anticipated to further interact with the surrounding tissues and is now found to be a cause for manifestation of latent cancer. The study of the secondary particle yield is thus critical in heavy ion treatment planning. Since heavy ions, (particularly carbon) are being widely used in therapy, such information becomes important. Also, the data available on neutron yield from heavy ion interaction in thick targets is limited. Organic scintillator detectors have been long recognized for their very good n- separation and are being extensively used in neutron measurements in positive ion accelerator facilities, which have mixed field where gammas are always present with neutrons. This work discusses the integrated neutron yield with its angular distribution and integrated dose from thick Al and C targets bombarded by C with kinetic energy ~ 10 MeV/A and F projectiles at ~ 7.6 MeV/A on thick Al target. The energy integrated yields from the different target projectile systems is compared and presented. Thick targets were studied as it represents any accidental or controlled beam loss situations in the accelerator component, drift tubes or beam dump. The thickness taken is such that the projectile particle loses its complete energy into the target before being completely stopped inside the target.

Tauc analysis is popularly used for the determination of optical band gap by extrapolating the linear portion of the Tauc's plot and finding its intersection point at energy axis. In most of the studies, the data points in the linear portion of the Tauc's plot are selected manually, which is time-consuming and the reproducibility in the selection process gets affected. To overcome this, an automated determination of band gap has been proposed for ensuring the reproducibility as well as for faster selection process. In this work, we report the development of an efficient algorithm which can provide the information of the optical band gap by Tauc analysis. The algorithm is based on finding the linear portion around maximum slope of the Tauc's plot. A computer program (autoTauc) based on the algorithm was written and was validated through CR-39 irradiated to four different alpha fluences. The extrapolated linear line obtained through linear regression (using the program) was observed to pass through the linear portion of the Tauc's plot. The optical band gap was found to be decreasing linearly with the alpha fluence for both direct and indirect transitions. Also the direct band gap was found to be higher than the indirect band gap.

Cement is an important component of concrete used as a shielding material in nuclear accelerators and reactors. Hence cement samples should be analysed for the presence of certain trace elements that may get activated by neutrons emitted during the production of radioisotopes in an accelerator, so as to minimize the low level radioactive waste to be handled during decommissioning. With this motivation the present work was undertaken and 44 samples of five broad classes of cements were analysed for natural radioactivity (226Ra, 232Th & 40K) and trace elements capable of generating long lived gamma radioactivity due to neutron activation.

Current research in the accelerator technology is focused towards achieving high energy, intense beams by minimizing conversion losses during beam acceleration. In such high current facilities, induced activity in structural materials become primary concern for radiation protection and materials like Ta and Nb, with low induced activity generation, high corrosion resistance characteristics are preferred along with conventional structural materials. In view of significant use of elements like Nb, Ta and Fe in the proton accelerators, a dose rate measurement and decay study has been carried out. The prompt γ- and neutron doses with residual activity profile from short and long lived isotopes were estimated using γ-ray spectrometric method.

Rock aggregates are major ingredient of concrete used for shielding against ionising radiation generated during the operation of nuclear particle accelerators. Their analysis for trace elements which may lead to neutron activation products during prolonged operation becomes important. Proper selection of ingredients helps in minimizing the radioactive concrete waste requiring disposal at the time of decommissioning.This work involves the collection of 42 samples of seven broad types of rock aggregates and their assessment for natural radioactivity (226Ra, 232Th and 40K), lithium and other trace elements that may lead to the formation of gamma emitting, long lived neutron activation products.

The neutron spectral yields from the Li(p,n) reaction has been considered as an important study due to its potential use as mono-energetic fast neutron source. This reaction has been studied at energies nearing Coulomb barrier for mono-energetic neutrons from Be-7 ground state emissions and at energies beyond few tens of MeV to get the quasi mono-energetic fast neutrons, depending on their specific applications such as cross section studies, calibration of neutron detectors, etc. However, the number of measurements at proton energy of 8-20 MeV is sparse in the literature. In this energy range, the mono-energetic neutrons are strongly interfered by emissions from other excited states distorting the emission neutron spectra. Majority of the earlier measurements were carried out using carbon as the backing material during evaluation of neutron yields to minimize the interference of neutrons from the backing material. Here, a commonly used thick Ta target was explored as the backing material for the thin Li target and the neutron yields were measured with solid polymeric neutron track detector, CR-39. This is a passive technique and does not require any associated instrumentation during the irradiation process. This work presents the estimation of thin target neutron yields from Li target by subtracting the neutron yields contributed by the supporting material (Ta), which was separately measured in the same physical conditions.

The quantification of induced activity in the accelerator structures and their decay profiles are required to be studied for planning the maintenance operations and the disposal procedures. This paper studies in detail the yield of radioactivity generated in the common beam dump materials, like copper and tantalum irradiated with proton beams of 10 and 20 MeV and their decay profiles using Fluka Monte Carlo simulations. The neutron yields and ambient dose equivalent rates generated from the target materials are also estimated using Fluka Monte Carlo code and are presented. Few of the estimated neutron ambient dose equivalent rates are experimentally validated.

To overcome the limitation of CR-39 at high dose region where large number of tracks are overlapped, the FTIR spectroscopic technique can be implemented for dose estimation. In the present work, CR-39 detectors were irradiated with alpha particles from 239Pu source having known doses up to 5.12 Gy. The detectors were subjected to chemical etching in steps of 1 h and subsequently FTIR spectra were recorded. Three strong bands i.e., 1800–1675 cm−1, 1350–1150 cm−1 and 810–760 cm−1 in the FTIR spectra were analysed to study the effect of etching and dose on the peak absorbance of these bands. The peak absorbance was found to decrease with the dose as well as with etching duration and the saturation effect in the peak absorbance was observed above 3 h etching. Etching duration of 2 h was found to be optimal etching time where the linear response was observed up to 5.12 Gy. Furthermore, the threshold for dose estimation by the FTIR spectroscopic technique was observed to be 0.41 Gy, above which this technique can be used. Empirical relations correlating the peak absorbance and dose were generated which can be used as calibration factors for dose estimation in the range 0.41–5.12 Gy using the peak intensity in FTIR spectrum of CR-39 detector.

Microwave induced chemical etching (MICE) has been successfully employed in reducing the etching duration using NaOH etchant. In this work, the MICE technique has been studied with KOH etchant to investigate the effect on the track development. Chemical etching (CE) has also been performed at different temperatures for a comparison purpose. Neutron irradiated CR-39 track detectors were subjected to stepwise MICE at 4 microwave powers after generating the temperature profile with 200 ml of 6 N KOH. The rate of increase in temperature before attaining the saturation temperature was found to be 3.28, 5.78, 8.2 and 16°C/minute for 300, 450, 600 and 900 W respectively. The image analysis showed the increase in track size with the increase in etching duration in both MICE and CE. The rate of growth of track diameter in MICE was observed to be higher than that of CE. The bulk etch rate as determined by the gravimetric method was found to be higher in MICE than CE. The maximum bulk etch rate in CE at 90°C was 11.81 μm h−1 which was lower than the minimum bulk etch rate 16.92 μm h−1 in MICE at 300 W. The bulk etch rate was found to increase with microwave power in MICE and with temperature in CE. Study on the variation of bulk etch rate with microwave power (in MICE) has been carried out and an empirical relation was generated. From the variation of bulk etch rate with temperature, the activation energy of CE for 6 N KOH was found to be 0.70 eV.

While measuring the neutron dose in accelerator radiation environment using CR-39 detector for radiation protection purpose, LET (linear energy transfer) spectrometry method is implemented when the information about the radiation source term is unknown. In this work, the neutron dose has been measured for p+181Ta reaction at different proton energies i.e. 8–20 MeV by LET spectrometry method using CR-39 detectors. The track density in CR-39 was found to increase exponentially with the proton energy and an empirical relation has been established. The dosimetric quantities viz. absorbed dose (DLET) and dose equivalent (HLET) were determined from the LET spectra and both these quantities were found to be increasing with the proton energy. Empirical relations were generated, which will be useful for predicting dose in similar radiation environment. The dosimetric data generated in this study would be useful for radiation protection of occupational workers working in the accelerator radiation environment.

Presently accelerator facilities emphasizes on generating charged particles with enhanced energy and flux. The radiation protection practices at these facilities are considered in civil engineering designs and strictly implemented through different administrative, access control measures (Sarkar in Radiat Meas 45:1476–1483, 2010). However, concern arises from induced activities, during maintenance and decommissioning stages, when sections of accelerator and shielding materials become highly radioactive. Major contribution of induced activity arises from stainless steel (SS-304) beam enclosures and Cu-dumps. Present work focuses on the generation of induced radioactivity profiles with delay counting of SS-304 and Cu along with instantaneous gamma and neutron dose rate measurements at various proton energies for source term estimation.

181Ta is a commonly used backing material for many targets in nuclear reaction studies. When the target thickness is less than the range of bombarded projectiles, the interaction via Ta(p,n) reactions in the backing can be a significant source of background. In this study, the neutron spectral yields from the reaction of protons of different energies (between 6 to 20 MeV) with a thick Ta target were determined using CR-39 detectors. The results from this study can be used as a correction factor in such situations. The parameters of registered tracks in CR-39 were analysed using an in-house image analysing program autoTRAK_n and then to derive the associated dose values. The spectral yields obtained experimentally were compared with those obtained from the theoretical calculations. The neutron yield was found to increase with increase in projectile energy mainly due to the opening of reaction channels from (p, n) to (p, 3n).

In this work, electron induced modifications on the bulk etch rate, structural and optical parameters of CR-39 polymer were studied using gravimetric, FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) techniques, respectively. CR-39 samples were irradiated with 10 MeV electron beam for different durations to have the absorbed doses of 1, 10, 550, 5500, 16 500, and 55 000 kGy. From the FTIR analysis, the peak intensities at different bands were found to be changing with electron dose. A few peaks were observed to shift at high electron doses. From the UV-vis analysis, the optical band gaps for both direct and indirect transitions were found to be decreasing with the increase in electron dose whereas the opacity, number of carbon atoms in conjugation length, and the number of carbon atoms per cluster were found to be increasing. The bulk etch rate was observed to be increasing with the electron dose. The primary objective of this investigation was to study the response of CR-39 to high electron doses and to determine a suitable pre-irradiation condition. The results indicated that, the CR-39 pre-irradiated with electrons can have better sensitivity and thus can be potentially applied for neutron dosimetry.

Effects of the duration of chemical etching on the transmittance, absorbance and optical band gap width of the CR-39 (Polyallyl diglycol carbonate) detectors irradiated to high neutron doses (12.7, 22.1, 36.0 and 43.5Sv) were studied. The neutrons were produced by bombardment of a thick Be target with 12MeV protons of different fluences. The unirradiated and neutron-irradiated CR-39 detectors were subjected to a stepwise chemical etching at 1h intervals. After each step, the transmission spectra of the detectors were recorded in the range from 200 to 900nm, and the absorbances and optical band gap widths were determined. The effect of the etching on the light transmittance of unirradiated detectors was insignificant, whereas it was very significant in the case of the irradiated detectors. The dependence of the optical absorbance on the neutron dose is linear at short etching periods, but exponential at longer ones. The optical band gap narrows with increasing etching time. It is more significant for the irradiated dosimeters than for the unirradiated ones. The rate of the narrowing of the optical band gap with increasing neutron dose increases with increasing duration of the etching.

Neutron dose for proton induced reactions on the combination of 7Li and 181Ta target was measured using CR-39 detector and a neutron rem meter, at five different proton energies (8–24 MeV). In case of CR-39, the dose equivalent (H LET) was measured via linear energy transfer (LET) spectrometry method using the major, minor radii of each track and thickness of removed surface, whereas the rem meter provided the direct reading of ambient dose equivalent [H*(10)]. Both these quantities per incident proton were found to increase with the proton energy. The response ratio of H LET to [H*(10)] was found to be in the range of 0.15–0.3 with an average 0.20 ± 0.09.

Effects of high-dose neutron irradiation on chemical and optical properties of CR-39 were studied using FTIR (Fourier Transform Infrared) and UV-vis (Ultraviolet-Visible) spectroscopy. The primary goal was to find a correlation between the neutron dose and the corresponding changes in the optical and chemical properties of CR-39 resulted from the neutron irradiation. The neutrons were produced by bombarding a thick Be target with 22-MeV protons. In the FTIR spectra, prominent absorbance peaks were observed at 1735cm(-1) (C=O stretching), 1230cm(-1)(C-O-C stretching), and 783cm(-1)(=C-H bending), the intensities of which decreased with increasing neutron dose. The optical absorbance in the visible range increased linearly with the neutron dose. Empirical relations were established to estimate neutron doses from these optical properties. This technique is particularly useful in measuring high doses, where track analysis with an optical microscope is difficult because of track overlapping.

Monte Carlo simulations have been carried out using the FLUKA code to improve the neutron ambient dose equivalent [H*(10)] response of the ZReC (zirconium-lined portable neutron counter responding satisfactorily to neutrons up to 1 GeV) by introducing various neutron absorbers in the system such as cadmium, gadolinium, natural boron, enriched B and borated polythene. It was found that ZReC can be effectively used as a portable neutron monitor by introducing any one of the following perforated layers: 5 mm thick natural boron, 0.5 mm thick enriched B or 1 cm high-density polythene mixed with 50 % boron by weight. The integral response of the instrument was also calculated for some typical reference neutron fields. The relative ambient dose equivalent response of the said system is also found comparable with that of the existing LINUS neutron monitor.

This study is carried out to establish a correlation between optical absorbance and track density in CR-39 detectors exposed to different fluences of D-T (14 MeV) neutrons. This can be useful in estimating the neutron fluence and hence the dose without involving the tedious track counting procedure, especially when the track density is extremely high. Variation in the optical properties is studied using UV-VIS-NIR (ultraviolet-visible-near infrared) spectroscopic technique. The neutron-induced recoil tracks are developed by chemical etching and the track density is determined. The optical transmission spectra are obtained for pristine and neutron irradiated detectors before and after etching. A linear relationship is obtained between the track density and the optical absorbance with increasing neutron fluence. Another objective of this work is to study the effect of etching on the optical properties such as transmittance and absorbance of irradiated CR-39 detectors. The optical properties are found to be changing due to the development of tracks in the detector.