Radiation chemical yield for loss of carbonate ester bonds in PADC films exposed to gamma ray

Radiation chemical yield, G value, for loss of carbonate ester bonds in PADC films, exposed to gamma ray from intense Co-60 source, has been determined by means of FT-IR spectrometry. The obtained value of 20 (scissions/100 eV) is fairly higher than that from heavy ion irradiations. It was found the density of hydroxide group in the film significantly increased by the exposure in air but hardly changed in vacuum.     

Radiation chemical yields for loss of ether and carbonate ester bonds in PADC films exposed to proton and heavy ion beams

Chemical modification along ion tracks in PADC films has been studied by means of FT-IR spectrometry, which was exposed to proton and heavy ions of He, C, Ne, Ar, Fe, Kr and Xe with energies around the Bragg peaks. This study covers a wide region of the stopping power ranging from 10 to 10,000 keV/μm. Removal cross sections for the loss of ether and carbonate ester bonds are assessed for each ion, as a function of the stopping power. Chemical damage parameters like the damage density, the effective track core radius and the radiation chemical yields, G values (scissions/100 eV), for each bond are also derived. We have found anomalous dependence of these parameters on the stopping power. The G value for the loss of carbonate ester bond decreased from 20 for proton down to 5 for C and Ne ions, and then increased with atomic number of heavy ions up to 8 for Xe ion. Radial dose distribution for each ion has been also calculated. Results are discussed from the viewpoint of polymeric structure of PADC that consists of two parts with different radio-sensitivities.     

Radiation chemical yields for the losses of typical functional groups in PADC films for high energy protons registered as unetchable tracks

A series of FT-IR spectrometric studies has been performed to understand the latent track structure in poly(allyl diglycol carbonate), PADC, which were exposed to proton beams with energies of 20, 30 and 70 MeV. These energies are too high to register etchable tracks in PADC. Chemical damage parameters, such as damage density, effective track core radius and radiation chemical yields, for losses of ether bond, carbonate ester bond and CH groups in PADC are evaluated as a function of the stopping power, which were compared to the previous results for 5.7 MeV proton and heavy ions, between He and Xe. Graphs of the chemical damage parameters are given at the wide stopping powers ranging from 1 to 12,000 keV/μm. The decreasing behaviors of the ether and carbonate ester bonds are on the almost identical trends with those of the heavy ions. On the contrary to this, the reducing behavior of CH groups is similar to that of the gamma rays. Different dependence of the chemical damage parameters for the loss of CH groups is found on the stopping powers between the both sides of the detection threshold as an etched track detector.     

Further studies on ageing and fading of CR39 PADC track detectors used as air radon concentration measurement devices

PADC detectors are commonly used both as radon detectors and as personal dosemeters for neutron radiation. In both cases the measurement in workplace fields are characterized by long term irradiations, lasting up to several months. During this period the detectors undergo to uncontrolled and unmonitored environmental conditions. In a recent work the same authors demonstrated that the environmental conditions, mainly temperature, can seriously affect the detector sensitivity. The temperature effect is to reduce the V ratio by decreasing the track etching velocity V_t. This causes a decrease in limit angle and efficiency.This paper describes the same ageing/fading test made with CR39 from a different supplier. In this case it seems that the temperature has a negligible effect, so no compensation algorithm is needed.     

On the mechanism of the sensitization of PADC (poly(allyl diglycol carbonate)) track detectors by carbon dioxide treatment

The sensitization effect of carbon dioxide treatments with 0.6 MPa on poly(allyl diglycol carbonate) (PADC) etched track detectors is confirmed for protons and He, C, and Fe ions, where the stopping powers range from 10 to 600 keV/μm. Based on the FT-IR study for the PADC films that were maintained at room temperature and at elevated temperatures, the diffusion coefficient of carbon dioxide, is determined as D = 14,670exp(−9030/T(K)) cm²/s. The sensitivity is enhanced when carbon dioxide is released toward the chemical etching solution that passes through the detector surface. Segmented PADC polymer chains are washed away by the flow of carbon dioxide along the latent tracks in PADC, which results in a higher track etch rate.     

Photocatalytic decomposition of methylene blue and 4-chlorophenol on nanocrystalline TiO2 films under UV illumination: A ToF-SIMS study

The photocatalytic degradation of methylene blue and 4-chlorophenol on nanocrystalline TiO₂ (nc-TiO₂) under UV irradiation was investigated by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Nanocrystalline TiO₂ films were prepared from suspensions containing TiO₂-crystallites of different average sizes, the smallest one being 12 nm. The organic substances (either methylene blue or 4-chlorophenol) were applied to these films. The specimens were studied in the pristine state and upon UV exposure. The UV illuminations were carried out both under atmospheric conditions and in situ under ultrahigh vacuum in the ToF-SIMS instrument. Distinct mass signals from the parent molecules and from fragment ions are observed for the as-prepared samples. Upon irradiation with UV light under atmospheric conditions, the surface composition is significantly changed, an observation ascribed to photocatalytic reactions induced by UV photons: the parent molecule signals are strongly diminished whereas fragmentation products are identified to be present at the TiO₂ surfaces. UV irradiations carried out under different vacuum conditions in the ToF instrument (ultrahigh vacuum, air or oxygen adsorption) indicate that varying ambient conditions may influence the photocatalytic reaction on the nanocrystalline TiO₂ films.     

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.     

Effect of gamma rays on PADC detectors

The effect of Gamma radiation in Polyallydiglycol carbonate (PADC) detectorrs has been studied in the dose range of 10⁰–10⁶ Gy. Some of the properties like bulk-etch rate, track-etch rate, activation energy for bulk and track-etching have been found out for different gamma doses from ⁶⁰Co Source in PADC. The experimental results are presented and discussed.     

Chemical cross sections induced by ions in solid organic detectors: Experimentation and simulation

Chemical ester bond scission induced by incoming ions in polyethylene terephthalate (PET), bisphenol A polycarbonate (PC), polyallyl diglycol carbonate (PADC), have been systematically determined by FT-IR transmission measurements. The studied ions (H, He, C, Ne, I, Ar, Fe, Kr, Xe) have LET ranging from 10 to 10 000 keV μm⁻¹. We discuss the opportunity to simulate the experimental chemical cross section obtained with an approach based on the dose deposited by the secondary electrons removed by the incoming ion. Such an approach has been already successfully applied for LR115.     

Microstructural evolution in metals during helium and proton irradiations

Abstract

Recent investigations of helium-implanted and proton irradiated metals at medium temperatures (T≤100°C) have demonstrated the importance of high energy cascade effects for the microstructural evolution. They can effect the formation and the evolution of He densities in small bubbles formed by He implantation and are important also for the formation of periodic walls of defect clusters, a phenomenon observed under proton irradiations. Experimental results obtained by transmission electron microscopy and differential dilatometry for MeV irradiations of Cu and Ni are summarized and compared with observations after heavy-ion and neutron irradiations.     

Gamma effect on track properties of PADC detector

Effect of high gamma irradiation on track properties of PADC (Homalite) has been studied in the dose range of 10¹–10⁶ Gy. The properties like bulk-etch rates and track-etch rates of the detector are found to increase due to gamma exposure. Etching efficiency of the detector increases due to exposure and it is significant at the dose higher than 10³ Gy. Another track property, the critical angle, is also influenced by gamma exposure and is found to decrease with increasing dose. In all cases it is observed that the post-gamma exposure has greater effect than the pre-gamma exposure. The experimental results are presented and discussed in details.     

Tuning the properties of tin oxide thin films for device fabrications

Tin oxide thin films were deposited on well cleaned glass substrates by thermal evaporation in vacuum and were annealed at 500?^°C in the open atmosphere inside a furnace for 90 min for promoting the sensitivity of the films. The X-ray diffraction studies revealed that the as-deposited films were amorphous in nature and the annealed films showed appreciable crystalline behavior. The annealed thin films were then irradiated using ⁶⁰Co gamma source. The radiation induced changes were then studied by X-ray diffraction, scanning electron microscopy, UV–vis spectroscopy and I–V characterization. The remarkable increase in the average grain size, the decrement in the energy band gap and resistivity due to the gamma irradiations up to a certain dose and the reversal of these properties at higher doses are the important observations. The large changes in the conductivity and energy band gap of the annealed thin films due to gamma irradiation make these films quite important device material for the fabrication of gamma sensors and dosimeters.     

Modification induced by proton irradiation in polyallyldiglycol carbonate (PADC)

Swift heavy ions interact predominantly through inelastic scattering while traversing through any polymeric medium producing excited/ionised atoms. Beyond a certain threshold, they affect the lattice structure leading to remarkable flexibility in engineering many physical and mechanical properties of the polymer. Polyallyldiglycol carbonate (PADC) is a class of polymeric detectors which finds its applications in various fields. In the present work, PADC samples were irradiated by four different fluences (≈10¹²–10¹³ cm⁻²) of 62 MeV protons from heavy ion accelerator (ISL) at HMI, Berlin. The modifications in the proton irradiated polymers as a function of fluence have been studied through different characterisation techniques such as Fourier Transform IR, UV-Vis, Electron Spin resonance, Thermogravimetric analysis, Differential Scanning Calorimetry and Track studies. The optical band-gap was found to be constant while a decrease in transmittance of PADC was observed with the increase in proton fluence. The thermal stability of PADC was found to be an inverse function of fluence. Further, these proton irradiated PADCs were exposed to fission fragments from ²⁵²Cf source and the bulk etch-rate was improved with the increase in proton fluence and was found to be increased by 90% for the PADC irradiated at the highest fluence as compared to the pristine. Thus, proton irradiation has led to degradation of the polymer by chain scission converting it into an easily etchable material.     

Surface modifications of PADC polymeric material by ion beam bombardment for high technology applications

Surface modification of Poly (allyl diglycol carbonate) (PADC) is induced by 150 keV Ag ions of different fluences. The pristine as well as bombarded samples were investigated by UV–Vis spectroscopy, Fourier transform-infrared analysis (FTIR) and micro-hardness tester. The variations of wettability and surface free energy were determined by the contact angle measurements. The obtained results showed that ion beam bombardment induced increase in the absorption spectra of the UV–Vis with increase of ion fluence as well. The direct and indirect optical band gap decreased from 4.2 to 3.6 eV for pristine sample to 3.2 and 2.5 eV for those bombarded with Ag ion beam at the highest fluence, respectively. Changes in chemical properties were observed by Fourier transform infrared spectroscopy. Increase in the wettability, surface free energy and work of adhesion with increase the ion fluence were observed. Ion bombardment inducing increasing in a micro-hardness surface due to the high carbon surface concentration and cross-linking effects in the polymeric chains. The bombarded PADC surfaces may find special applications to the field of the micro-electronic devices and printing process.     

Energy dependence of the secondary ion yield of metals and semiconductors

Relative secondary ion yields of 12 metals and 2 semiconductors have been determined under ultrahigh vacuum conditions as a function of the primary argon ion energy between 2 and 15 keV. The ion yields were found to exhibit a strong energy dependence which cannot be accounted for by the energy dependence of the sputtering yield. Very pronounced effects are found with elements for which kinetic ionization is important. The relative secondary ion yields vary by less than two orders of magnitude, aluminium showing the largest and gold the smallest yield. Above about 10 keV the results can be described to within a factor of two by a recently developed ionization model if reasonable assumptions are made with respect to the physical parameters of the bombarded surface.     

Feasibility study for the use of PADC as a radiation detector for living cell cultures

In the framework of an ESA project, a microbiological experiment in space is planned. In this experiment a cell culture will be exposed to cosmic radiation onboard a spacecraft. Because the living cell culture will be directly on a nuclear track detector stack, this detector will be submitted to a different environment than normally used. The temperature will be 37°C and the culture will be in a biological growth medium. Tests have been conducted to assess the possible use of PADC in these conditions. For this, a series of alpha irradiated detectors have been exposed for different periods of time (up to 1 month) to these ‘biological’ conditions. The radiological properties as well as the mechanical properties (swelling…) have been investigated. Results show no influence of the biological environment on the PADC, which makes it useable under these circumstances.     

Effect of high gamma dose on the PADC properties

The effect of the properties of PADC nuclear track detectors after exposure to high doses of gamma absorbed doses up to 5×10⁵ Gray (50 Mrad) were studied. The gamma source was a 9.03 PBq (244 KCi), Co-60 source. Results indicate that each of the bulk etch rate (V_b), the tracks etch rate (V_t) and the sensitivity (V) of the detectors increases with the high gamma absorbed dose, but there is a drop in these parameters at the low gamma absorbed dose. Signs of surface roughness were observed by increasing the gamma absorbed doses and changes in color observed for doses larger than 2×10⁵ Gray. The temperature of detectors during irradiation time reached 41°C. The fission fragment tracks (from Cf-252 source) disappeared quickly within the etching time (minutes) for total absorbed doses greater than 3×10⁵ Gray due to their high bulk etch rate.     

Combined high pressure and heavy‐ion irradiation: a novel approach

Swift heavy‐ion irradiations of a wide variety of materials have been used to modify and manipulate the properties of solids at the nanoscale. Recently, these high‐energy irradiations have been successfully combined with high‐pressure experiments. Based on results obtained for zircon (ZrSiO₄), this paper introduces this new experimental approach involving diamond anvil cells and large ion‐accelerator facilities. This technique provides a wide spectrum of geoscience applications from nanoscale simulations of fission‐track formation under crustal conditions to phase transitions of radiation‐damaged minerals resulting from meteorite impact.     

Secondary ion emission from Si bombarded with large Ar cluster ions under UHV conditions

Si was bombarded with size-selected 40 keV Ar cluster ions and positive secondary ions were measured using the time-of-flight technique under high and ultra-high vacuum (HV and UHV respectively) conditions. Si⁺ ions were main species detected under the incidence of 40 keV Ar cluster ions, and the yields of Si cluster ions such as Si₄⁺ were also extremely high under both conditions. On the other hand, oxidized secondary ions such as SiO⁺ were detected with high intensity only under the HV condition. The yield ratios of oxidized ions decreased in UHV to less than 1% of their values in HV. The effect of residual gas pressure on Si cluster ion yields is relatively low compared to oxidized ions, and the UHV condition is required to obtain accurate secondary ion yields.