Poly Allyl Diglycol Carbonate Research Articles

Relaxational behavior of CR‐39 polycarbonate used as nuclear track detector

AbstractThe relaxational behavior of CR‐39 (poly allyl diglycol carbonate) nuclear track detectors was determined over a large temperature range (−100 to 125°C) including the glassy, glass transition, and ionic conduction regions by means of dynamic mechanical and dielectrical measurements, differential scanning colorimetry, linear coefficient of expansion, and especially thermally stimulated current methods owing to their high sensitivity and resolving power. This investigation was carried out as a first step aimed, on the one hand, at finding possible correlations between dosimetric performances, polymer morphology, and intrinsic or extrinsic relaxations and, on the other hand, at determining the origin of the inconsistent background and response properties, which are still a serious obstacle to the use of this material as a personnel dosimeter in spite of its high sensitivity and wide response range. Six distinct relaxation regions have been evidenced, most of which being to some extent dependent on the sample investigated and its thermal history. From higher to lower temperatures, these various relaxations have been ascribed to charge carrier migration over macroscopic distances (ρ), glass transition (α), nonequilibrium precursor motions of the glass transition (ά), and local mode motions of the diethylene‐glycol dicarbonate links (β), diethylene glycol segments (γ), and carbonate groups (δ). In addition to these intrinsic relaxations, the as‐received samples are also characterized by small‐scale residual stresses that relax out irreversibly at temperatures lower than the glass transition temperature Tg. The systematic study of the influence exercized by the position of a specimen in a given sheet, and, for a given sample, by annealing, thermal cycling, and physical aging on relaxation properties shows that, besides spatially inhomogeneous internal stresses, cross‐linking density, and cluster morphology, marked structural modifications and nonequilibrium processes can occur by heating the polymer above Tg. These phenomena deserve a great deal of consideration because they could be key points for identifying the sources of the troublesome fluctuations of dosimetric response. Relaxation studies thus appear as useful and sensitive tools for a deeper understanding of the performance of CR‐39 polymer as a track recorder.

Optical waveguide fabrication by ion beams in the PADC-polymer

Ion beams and γ rays are used to modify refractive index of polyallyldiglycol carbonate (PADC). Ion irradiations (H, Li, B) lead to optical waveguides the properties of which depend on the kind of ions, ion fluences and energy. Radiation damage consistently increases the refractive index. Measured variations of refractive index are given as function of deposited energy density (by ions or γ rays). It appears that index variations are principally linked to structural modification due to deposited energy.

Track-size distribution of electrochemically etched CR-39

The track densities and track size distributions of polyallyl diglycol carbonate (PADC) track detector for various neutron energies under different etching conditions are presented. The etching regimes are the combination of chemical etching (CE) and electrochemical etching (ECE) at low and high frequencies (LF, HF) with different electric field strengths and etching times. The results show that the two-step regime (CE+HFECE) produces larger tracks (about 2 to 3 1 2 times, depending on neutron energy) than the three-step (CE+LFECE+HFECE), while the track densities are almost the same.

Response and background study of various PADC materials

The results of response and background study of polyallyl diglycol carbonate (PADC) are presented. In this study, the commercially available polymeric detectors supplied by five different manufacturers were used. For each type/thickness of material, two of three sheets were sampled. Each sheet divided into six equal areas and from each, 3 or 4 background and 2 sensitivity detectors were taken and the total of 512 samples were tested. The sensitivity determined for normally incident bare 252 Cf neutrons. The highest sensitivity of 0.2 cm -2 .μSv -1 with the lowest average background of about 150 μSv for a single sheet was found. The minimum detectable dose equivalent (three standard deviations) obtained was 153 μSv.

On the SSTD calibration simulation by sparsely ionizing radiation

Two types of cellulose nitrate, CN 85 and CA 80-15 (Kodak Pathé, France) and polyallyldiglycol carbonate CR 39 (Pershore Mouldings, U.K.) were calibrated by different ions for the purpose of the linear energy transfer (L) spectrometry. The calibration curves in the form of track-to-bulk etch-rate ratio vs L were experimentally established within the L ∞ limits from 150 MeV cm 2 g -1 to 19740 MeV cm 2 g -1 . The experimental calibration curves are compared with the curves obtained by calculation using the detector bulk etch rate dependence upon the electron dose. An encouraging agreement between calculated and experimental calibration curves was noted for CR 39. The possibility of the high electron or gamma dose irradiation for the periodical SSTD calibration updating is discussed.

Energy loss and mean ranges of 93Nb in nickel and tantalum

A versatile nuclear track technique has been employed to measure energy loss and mean ranges of 18.04 MeV/u 93Nb ions in nickel and tantalum. A polyallyldiglycol carbonate (CR-39) track detector has been calibrated and used in the present work to determine the energy of the transmitted heavy ions through metal targets. The passage of 93Nb in nickel and tantalum was studied in terms of energy-loss rate and mean ranges. The experimental values are also used to check the validity of theoretical data obtained from a few commonly used theories and data tables. The experimental technique is also briefly discussed.

The NRPB radon personal dosimetry service

A radon personal dosemeter has been developed. The dosemeter is simple, cheap, robust, disposable and indelibly numbered. The operation principle is that of a radon diffusion chamber, which principle has been established both experimentally and theoretically. The dosemeter is an enclosure which excludes radon progeny and detritus whilst allowing access of radon gas. The alpha particles from the decay of radon gas, and from radon progeny, which are, in the main, plated out on the detector and on the dosemeter walls, are registered in a piece of poly allyl diglycol carbonate (PADC). The number of alpha particle tracks recorded is proportional to the time integral of the radon gas concentration external to the dosemeter. Since December 1986, NRPB has been offering a dosimetry service approved by the appropriate UK authorities.

The NRPB PADC neutron personal dosimetry service.

The UK National Radiological Protection Board has been operating a successful contract neutron personal dosimetry service based on poly-allyl diglycol carbonate (PADC, also known by the trade name CR-39) since 1986, covering about 1500 workers and serving major nuclear sites in the UK and abroad. In that time approximately 100,000 dosemeters have been issued. Since the service was launched, a number of aspects have undergone evolution and it is therefore worthwhile to give an updated summary of how the service operates and performs today. The description covers the choice of plastic and of etching technique, the design of the dosemeter, the features of the automated image analysis, and the characteristics of the control software. Also described are the approaches to calibration and traceability and to compensation for energy and angle dependence, with particular mention of the ability of the service to estimate the quantity Hp(10) in accordance with the requirements of the European Council Directive 96/29/Euratom.

The NRPB PADC Neutron Personal Dosimetry Service

Since July 1986 NRPB has been operating an approved neutron personal dosimetry service using poly-allyl diglycol carbonate (PADC or CR-39). The PADC dosemeter has an improved energy range over the previously used nuclear emulsion and is expected to be increasingly preferred. Description is here given of the complete operating system, with some discussion of operational experience to date.

A modified adenosine polyphosphatase histochemical method to demonstrate Langerhans cells in fragile epidermis.

Adenosine polyphosphatase enzymes provide useful markers for epidermal Langerhans cells. Established adenosine polyphosphatase histochemical methods were refined and applied to demonstrate Langerhans cells in thin sheets of murine dorsal epidermis. The skin was supported during staining by attaching the keratinized surface to polyallyl diglycol carbonate "plastic" slides with cyanoacrylate adhesive and flattening it with pressure from a glass slide on the dermal surface. Optimal specific staining of dendritic Langerhans cells occurred after fixation of ethylenediaminetetraacetic acid-separated epidermal sheets in cacodylate buffered formaldehyde for 20 min and incubation, in the presence of magnesium and lead ions, with 9.36 X 10(-4) M adenosine diphosphate (ADP) for 45 min. Better definition of the cells was obtained with ADP as a substrate than with any concentration of adenosine triphosphate.

The Performance of the NRPB Radon Personal Dosemeter

Abstract The NRPB has developed a radon personal dosemeter for use in mines. The dosemeter is being introduced into operational service subject to approval by the appropriate authorities. The principle of operation of the dosemeter is established both experimentally and theoretically. The dosemeter acts as a radon diffusion chamber, excluding radon progeny and detritus, limiting access of moisture but allowing relatively free access of radon gas. The alpha particles from the decay of radon and its progeny are recorded in a piece of polyallyl diglycol carbonate (PADC). The net density of the electrochemically etched pits is proportional to the time integral of the radon gas concentration external to the dosemeter. Prior to its introduction, trials of the dosemeter have been carried out in various mines in the United Kingdom. These trials were in addition to laboratory investigations of the performance of the dosemeter under simulated miners' conditions. The performance of the dosemeter is reported in terms of its ability to measure the time integral of the radon gas concentration unaffected by the environmental condition.

Development of a single element neutron personal dosemeter for thermal, epithermal and fast neutrons

A single element neutron personal dosemeter has been developed which has an approximately dose equivalent response to thermal, epithermal and fast neutrons. The detection element consists of 500 μm thick rectangle of poly allyl diglycol carbonate (PADC). The PADC used is that commercially available from Pershore Mouldings Limited. The rear surface of the PADC detector is in contact with a piece of polyamide plastic. The rear surface of the PADC detector is electrochemically etched. The fast neutron response results from development of the tracks of recoil protons produced mainly by interactions of neutrons in the PADC, with a contribution from interaction in the packaging and dosemeter holder for neutrons of energies greater than about 7 MeV. The thermal and epithermal neutron response is from protons (initial energy 600 keV) produced in capture reactions on nitrogen in the polyamide plastic.

A radon personal dosemeter for miners

A radon personal dosemeter has been developed for use in mines. The dosemeter is simple, cheap, robust, disposable and indelibly numbered. The operation principle is that of a radon diffusion chamber, which principle has been established both experimentally and theoretically. The dosemeter is an enclosure which excludes radon progeny and detritus whilst allowing access of radon gas. The alpha particles from the decay of radon gas, and from radon progeny, which are, in the main, plated out on the detector and on the dosemeter walls, are registered in a piece of poly allyl diglycol carbonate (PADC). The number of alpha particle tracks recorded is proportional to the time integral of the radon gas concentration external to the dosemeter.

Properties and applications of CR-39 polymeric nuclear track detector

The objective of this paper is to provide an overview of the current status in neutron personal dosimetry based on poly allyl diglycol carbonate (PADC), also commonly known by the commercial name CR-39, to summarize the best practices in the field, and to point future research directions. An overview of the fundamentals of the technique is given, including a discussion on the PADC material, main parameters and characteristics, practical considerations, dosimetry approaches, and relevant standards. This work also summarizes the best practices adopted by individual monitoring services (IMSs) and discusses the research needed to improve the performance of this type of neutron dosimetry technique, as well as the challenges that make progress difficult. This work is based on the knowledge and experience of several laboratories and investigators and is part of the activities of the European Radiation Dosimetry Group (EURADOS) Working Group 2 –Harmonization of Individual Monitoring in Europe (WG2).