Poly Allyl Diglycol Carbonate Research Articles

Control technique of personal dosemeter response to fast neutrons with multi-layer radiator

Abstract An ideal radiator structure has been discussed for perfectly constant energy dependence of PADC (poly-allyl-diglycol carbonate) based neutron dosemeter. A contribution of a hydrogen atom to the dosemeter sensitivity was numerically evaluated as a function of both depth in the radiator and neutron energy. The energy dependence of the sensitivity can be expressed by the integral of the product of this function and depth-dependent density of hydrogen atoms. The distribution of hydrogen density was obtained by unfolding the integral equation. It was found that the deviation in relative sensitivity of the dosemeter consisting of PADC and a designed radiator could be reduced within 5.4% in the energy range of 1–20 MeV.

Fabrication of pseudo three-dimensional PADC cell culture substrates for dosimetric studies

Abstract Pseudo three-dimensional (3D) polyallyldiglycol carbonate (PADC) cell culture substrates were fabricated by creating micrometer-size pores on thin PADC films by alpha-particle irradiation and subsequent chemical etching. Our results showed comparatively fewer 53BP1 foci in alpha-particle irradiated as well as bystander HeLa cells cultured on pseudo 3D PADC substrates than in those cultured on two-dimensional substrates.

SU‐E‐I‐69: Development of An Automatic System for the Readout of Etch‐Track Neutron Dosimeters

Purpose: To simplify and accelerate the readout of etch‐track neutron dosimeters made of poly‐allyl diglycol carbonate (PADC) by automating the process of counting ion tracks caused by neutrons in the detector material. Methods: A LabVIEW application and an ImageJ macro were developed for the analysis of images of the detector surface which were taken by a camera mounted onto a microscope. The LabVIEW application is used to control the microscope, to start the ImageJ macro and to adjust different parameters such as the format of the image to be analyzed. The ImageJ macro is used for the analysis of the images. After a background correction an edge filter is used in order to enhance the tracks. Afterwards an appropriate threshold is determined. All tracks with a certain minimum size were counted with ImageJˈs Analyze Particles function. False positives due to surface defaults or other artefacts such as dust or scratches on the detectors were eliminated according to their circularity, solidity and distribution in the image. All results are saved in a log file. A warning is displayed if surface defaults are detected. Results: The developed ImageJ macro is able to analyze most images correctly. The number of tracks (± 1) was determined correctly in 98 % of the images. Artefacts due to dust or scratches are not counted as tracks. Surface defaults are sometimes not detected which results in a higher number of tracks. In most of those cases the number of tracks and therefore the corresponding dose is still under the reporting limit. Conclusions: The LabVIEW application and the ImageJ macro developed in this work simplify the readout of PADC etch‐track neutron dosimeters. The number of correctly analyzed images is in the same range or even higher as that from a trained operator who counts the tracks manually.

Influence of variation of etching conditions on the sensitivity of PADC detectors with a new evaluation method

At the Paul Scherrer Institut, a personal neutron dosimetry system based on chemically etched poly allyl diglycol carbonate (PADC) detectors and an automatic track counting (Autoscan 60) for neutron dose evaluations has been in routine use since 1998. Today, the hardware and the software of the Autoscan 60 are out of date, no spare components are available anymore and more sophisticated image-analysis systems are already developed. Therefore, a new evaluation system, the 'TASLIMAGE', was tested thoroughly in 2009 for linearity, reproducibility, influence of etching conditions and so forth, with the intention of replacing the Autoscan 60 in routine evaluations. The TASLIMAGE system is based on a microscope (high-quality Nikon optics) and an ultra-fast three-axis motorised control for scanning the detectors. In this paper, the TASLIMAGE system and its possibilities for neutron dose calculation are explained in more detail and the study of the influence of the variation of etching conditions on the sensitivity and background of the PADC detectors is described. The etching temperature and etching duration were varied, which showed that the etching conditions do not have a significant influence on the results of non-irradiated detectors. However, the sensitivity of irradiated detectors decreases by 5 % per 1°C when increasing the etching temperature. For the variation of the etching duration, the influence on the sensitivity of irradiated detectors is less pronounced.

Micro-collimators fabricated by chemical etching of thin polyallyldiglycol carbonate polymer films exposed to oxygen ions

One approach for α particle radiobiological experiments is to use solid-state nuclear track detectors (SSNTDs) as support substrates to record the α particle hit positions on the targets. To facilitate accurate characterization of the hit positions as well as the incident α particle energies, micro-collimators are required in these experiments to restrict the incident α particles to those with small deviations from normal incidence with respect to the collimator. In the present paper, we fabricated micro-collimators, which restricted α particles to those with deviations as low as 12°. Specially etched polyallyldiglycol carbonate (PADC) films, which are a kind of SSNTD, with a thickness 70 μm were prepared from commercially available PADC films. These were then irradiated by 4.83 MeV/n oxygen ions generated from the heavy-ion medical accelerator in Chiba (HIMAC), Japan. The irradiated films were chemically etched for at least 2.7 h to achieve etched-through air channels to form the micro-collimators. The micro-collimators formed by etching the irradiated films for 2.7, 3.0 and 4.0 h were experimentally shown to be able to restrict α particles to those very close to normal incidence. In contrast, the micro-collimator formed by etching the irradiated film for 4.5 h started to allow α particles with larger deviations from normal incidence to pass through, which is likely due to overlapping of air channels from excessive etching.

Neutron dosimetry device using PADC nuclear track detectors

A device consisting of poly allyl diglycol carbonate (PADC) foils with a polyethylene and polyvinyl chloride (PVC) radiator was calibrated in order to perform the dosimetry of an 241Am-Be source covering a dose range from 0 to 3.1 mSv. Working conditions were established for a good visualization and counting of tracks: chemical attack was made in two steps with different solutions and etching times. A good fit was obtained for the dose as a function of the number of tracks per unit surface area. The calculated decision threshold was 0.12 mSv.

Ion beam modification of surface properties of CR-39

The effects of ion-beam bombardment on the physical and chemical properties of poly(allyl diglycol carbonate) (CR-39) polymer have been investigated. CR-39 samples were bombarded with 320 keV Ar and 130 keV He ions at fluences ranging from 1 × 1013 to 2 × 1016 ions/cm2. The nature and extent of radiation damage induced were studied by UV–VIS spectrometry, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, as well as Vickers' hardness measurements. In addition, the effect of ion fluence on the wetting properties of ion-beam bombarded CR-39 polymer was determined by measuring the contact angle for distilled water. UV–VIS spectra of bombarded samples reveal that the optical band gap decreases with increasing ion fluence for both Ar and He ions. In the FTIR spectra, changes in the intensity of the bands on irradiation relative to pristine samples occurred with the appearance of new bands. XRD analyses showed that the degree of ordering of the CR-39 polymer is dependent on the ion fluence. Changes of surface layer composition and an increase in the number of carbonaceous clusters produced important change in the energy gap and the surface wettability. The surface hardness increased from 10.54 MPa for pristine samples to 28.98 and 23.35 MPa for samples bombarded with Ar and He ions at the highest fluence, respectively.

Neutron area monitoring at storage bunkers of density/moisture gauges

Previous studies remarked the need of performing neutron personal dosimetry, together with gamma dosimetry, when using portable density/moisture gauges that are normally equipped with gamma and neutron sources. The convenience of our Poly-Allyl-Diglycol-Carbonate (PADC) based neutron dosimeter to perform long-term routine survey of all workers involved in the transport, maintenance and usage of these gauges was also corroborated in the past. This complete dosimetric control offers the possibility to quantify simultaneously individual neutron and gamma doses of workers operating such devices, especially in the most frequent cleaning and maintenance (shutter lubrication) operations of the gauges or in emergency situations that may lead to radiological risk of the persons involved. Another aspect to be considered, from the radioprotection point of view, is the optimization of the occupational and public exposure in the storage bunkers of the gauges. In this work, three storage bunkers, located at three different factories of the PAYMA Cotas S.A.U company, have been monitored for three months using several units of our PADC based neutron dosimeter. Special care has been taken to study also offices near the bunkers with high occupancy rates and passage zones, such as toilets and access areas. Results for all monitored points inside and around the three storage bunkers are presented. Neutron doses inside the bunkers could be relatively high depending on the specific conditions (geometry configuration, localization and shielding composition) of the considered bunker and the number of portable gauges stored.

Cone evolution on VUV laser ablated polymers

We report on conical microstructures formed on polycarbonate and polyallyl di-glycol carbonate (CR39) ablated using 157-nm F2 laser radiation. These are distinguished by having smooth, straight walls and, for CR39, sharp tips, together with interference and diffraction fringes around their base. Etch-rate modelling of a non-planar surface and diffraction-modulated fluence is used to explore how cones may evolve, and an estimate is made of thermal loading on microcones.

Practical consequences for the use of a personal dosemeter for fast neutrons at high-energy accelerators based on PADC detectors exposed up to one year

Abstract Since 1998, Paul Scherrer Institut has employed the routine use of a personal neutron dosimetry system based on chemically etched PADC (poly allyl diglycol carbonate) detectors and automatic track counting. In 2004, a new concept for individual monitoring at high-energy accelerators was implemented. In this concept the photon dosemeter of a combined photon/neutron dosemeter is evaluated monthly. The neutron dosemeter is only evaluated if the personal photon dose exceeds 2 mSv, or if the exposition period of the neutron dosemeter exceeds one year. Significant consequences for the evaluation of the neutron dosemeter in the dosimetry service were evidenced in the new concept. The wearing period of the neutron dosemeter can range from 1 to 12 months, potentially longer. Therefore, the long-term behavior of background track density and variation of response to Am–Be within 17 months was studied. The effects of “fading” and “aging” that influence the response of PADC detectors are determined. The application of an algorithm for neutron dose calculation takes into account long-term behavior and is described. Furthermore, repeated field calibrations were performed at the CERN-EU high-energy reference field (CERF) facility.

Investigation of the fluorescence emitted from polyallyl diglycol carbonate modified by gamma-ray radiation excited by UV radiation

The fluorescence emitted from the gamma-ray-irradiated polyallyl diglycol carbonate upon illumination by the 346 nm UV radiation is studied. The fluorescence spectra show two distinct phenomena, the variation of fluorescence wavelength and intensity with received irradiation dose. These variations are found to be correlated to the change in the dielectric constant and the change in absorption. The dielectric constant is measured at three guiding frequencies, while the absorption is predicted with the reflected first and second diffractions of the excitation monochromator. The results support the donor-bridge-acceptor molecular origin of the fluorescence.

High gamma-ray dose measurement using nuclear track detector

Three dosimetric properties of poly allyl diglycol carbonate (PADC) and their response to gamma irradiation are put forth. The variation of the optical absorption edge with the received dose can be used as a dosemeter for doses >500 kGy. The variationdielectric function is, to some extent, linear with dose logarithm but has a low precision. The fluorescence emitted from the irradiated PADC upon illumination by the 346-nm UV radiation intensifies the changes in the dielectric properties and shows an excellent dosimetric behaviour in response to gamma ray in both precision and simplicity of procedure. Results showed that this property could be used as a dosimetric properties for measuring doses between 100 Gy and 6 MGy.

Positron Annihilation Doppler Broadening Spectroscopy as Convenient Method to Detect Radiation Effect on CR-39 Track Detector

Positron Annihilation Doppler Broadening Spectroscopy (PADBS) is a characterization technique that is sensitive to damage of radiation in polymers. A damage zone or defect will be created due to the irradiation of Polyallyl diglycol carbonate (CR-39) with α-particles. It is convenient to study this defect caused by α-particle energies using both PADBS and track diameter measurements. An abrupt change in the S and W line-shape parameters has been observed at 3.75 Mev of αparticle energy, while the track diameter shows a continuous decrease for samples irradiated at more than 2.5 MeV of the αparticle energies.

Convenient fabrication of three-dimensional cell-culture substrates through introduction of micrometer-size pores on polyallyldiglycol carbonate polymer films

We explored the fabrication of three-dimensional (3D) substrates by creating micrometer-size pores on polyallyldiglycol carbonate (or PADC) polymer films through irradiation of the film by alpha particles and subsequent chemical etching. HeLa cells cultured on these 3D substrates were observed using scanning electron microscope. Multiple directions and multiple layers of HeLa cells were observed to have grown in the pores, with normal nuclei and cell membranes as well as good cell spreading. For the cells cultured in 3D substrates with or without additional small pores, no significant differences were observed between their vinculin expression profiles, which were in contrast to the observation made for cells cultured on 2D substrates showing that small pores could enhance vinculin expression. The presence of the large pores and/or the enhanced biocompatibility of the substrate in the present experiments might be the reasons. The protrusions of cells were confined by the small pores, which was similar to the observation made for cells cultured on 2D substrates.

Micro-collimator fabricated by alpha-particle irradiation of polyallyldiglycol carbonate polymer film and subsequent chemical etching

In the present paper, we propose a method to fabricate a “micro-collimator” with a thickness of 15 μm. A commercially available PADC film with a thickness of 100 μm was first chemically etched with NaOH/ethanol solution to obtain a thin PADC film. This thin PADC film was then irradiated by 5 MeV α particles through a “macro-collimator” with a thickness of 5 mm and a hole diameter of 1 mm. This PADC film with latent tracks was then further etched in aqueous NaOH solution to form the micro-collimator with a thickness of 15 μm and etched-through air channels were all confined to a circular area with 1 mm diameter. Verifications were performed by checking the etched α-particle tracks formed on a test PADC film from α particles having traveled through a 20 μm support substrate attached to the 15 μm micro-collimator (both substrate and micro-collimator also made of PADC). The results are discussed.

A comparative study of gamma radiation effects on track properties of different PADC detectors

Track properties of gamma-irradiated polyallyldiglycol carbonate (PADC) detectors (Homalite, Pershore and Trastrack) are studied in the dose range of 101–106 Gy. Results show that the bulk and track etch rates of all three types of PADC detector increase at doses higher than 104 Gy. This increase is more pronounced in post-gamma exposed detectors. The change in etch rate ratio (S) for post-gamma exposed PADC–Homalite detectors is more significant when compared with the other detectors. The critical angle for etching shows that etching at a low temperature of 60 °C is more effective, and the critical angle value is decreased to a significant extent for all three types of PADC detectors. Etching efficiency of post-gamma exposed samples is found to be much higher than the pre-gamma exposed sample at the highest dose of 106 Gy. When compared, it was found that of the three PADC detectors, PADC–Homalite detectors seem to be more sensitive to gamma irradiation.

Overview of PADC nuclear track readers. Recent trends and solutions

The development of automated track readers dates back to the first routine dosimetry applications of solid state nuclear track detectors. Many research-laboratory track readers and a few commercial systems were introduced in the past 25 years. The traditional application area for high-throughput track readers is radon testing in buildings and fast neutron dosimetry. The latter application, in particular, has considerably increased the need for efficient polyallyldiglycol carbonate (PADC) track reader systems with high throughput. The paper provides an overview of recent trends in the development of high-throughput PADC track readers and it gives a glimpse into the practice of designing this category of devices. A general overview is provided of the technical aspects relating to the optics, the hardware and the track recognition approaches. Ultimate theoretical limits in the performance as well as promising new approaches are addressed. Requirements and practical solutions are illustrated with reference to a commercially available system.

Nationwide survey of radon levels in indoor workplaces in Mexico using Nuclear Track Methodology

This report presents the preliminary results of an indoor workplace radon survey conducted during 2006–2007. Monitoring was carried out in 24 of the 32 federal entities of Mexico, incorporating 26 cities and 288 locations. The area monitored was divided into 8 regions for the purposes of the study: Chihuahua (a state with uranium mines), North-Central, South-Central, Southeast, South, Northeast, Northwest, and West. These regions differ in terms of geographic and geological characteristics, climate, altitude, and building materials and architectonic styles. Nuclear Track Methodology (NTM) was employed for the survey, using a passive closed-end cup device with Poly Allyl Diglycol Carbonate (PADC), known by its trade name CR-39 (Lantrack ®), as detector material. Well-established protocols for making continuous indoor radon measurements were followed, including one-step chemical etching in a 6.25 M KOH solution at 60 ± 1 °C with an etching time of 18 h. The track densities were determined with an automatic digital system at the Instituto de Física de la Universidad Nacional Autónoma de México (IFUNAM) (Physics Institute of the National Autonomous University of Mexico), and calibrated in facilities at the Oak Ridge National Laboratory (ORNL). The importance of this survey lies in the fact that it represents the first time a nationwide survey of radon levels in indoor workplaces has been carried out in Mexico. Mean indoor radon levels from continuous measurements taken during and after working hours ranged from 13 Bq m −3 (the lower limit of detection) to 196 Bq m −3. Analogous official controls or regulations for radon levels in indoor workplaces do not exist in Mexico. The survey described here contributes to knowledge of the natural radiological environment in workplaces, and will aid the relevant authorities in establishing appropriate regulations. The survey was made possible by the efforts of both a private institutions and the Dosimeter Application Project of the IFUNAM.

A measurement of the angular distribution of the diffuse optical transmittance of etched nuclear tracks in CR-39

This paper presents a device to measure the angular distribution of the diffuse optical transmittance produced by etched nuclear tracks in polyallyl diglycol carbonate (PADC) detector. The device makes use of a stepper motor to move an array of four photodetectors around the sample in 1.8° steps. The integrated transmitted light was observed to increase monotonically with the etched track density in a range from zero to 2.8 × 10 5 cm −2, using a neutron Am–Be source.

Population vulnerability due to the exposure to radon and airborne particulate matter (PM 10), in Mexico City

Exposure to indoor radon and suspended particulate matter (SPM) is considered a high risk in lung cancer aetiology. In this paper indoor radon and SPM concentration measurements and their correlations, associated with lung cancer cases are given. Mexico City suffers high concentration of SPM as well as other photochemical pollutants such as ozone. During the last decade in Mexico City, radon and SPM have been monitored. The indoor radon measurements were done using the Nuclear Track Methodology, basically the close-end-cup device with polyallyldiglycol carbonate as detector material, followed of an established chemical etching protocol, and automatic digital image analyzer system for counting. SPM size and concentration were obtained from monitoring stations located along the city. The results show that the central–north part of Mexico City has a large concentration of SPM and the vulnerable population (older than 65 years and younger than 14 years) is located essentially in the same region. In this area, a large number of lung cancer cases were found, even if indoor radon levels were below the recommended limits.