The trapping effect of sulfur sensitization center Ag_2S cluster on T-grain AgBrI microcrystals

Chemical sensitization is a widely adopted technique that improves the photo-graphic sensitivity of silver halide crystals with basic emulsion. Sensitization centers,which can save photoelectrons in the process of latent-image formation, have beenformed on microcrystals after chemical sensitization. Therefore, chemical sensitizationwas widely adopted for many years. Sulfur sensitization is an important chemical sen-sitization technique in all chemical sensitization methods. First, in 1925, Sh…     

The trapping effect of sulfur sensitization center Ag<Subscript>2</Subscript>S cluster on T-grain AgBrI microcrystals

The microwave absorption dielectric-spectrum technique was used to study the decay kinetics of photoelectrons in sulfur-sensitized silver halide crystals. The time-resolution spectrum of free electrons and shallow-trapped electrons generated in sulfur-sensitized AgBrl crystals has been obtained. The relationship of the trapping effect of sensitization centers Ag₂S and sensitization time or temperature in emulsions has been duscussed. With the increase in the sensitization time and temperature, the trap effect of sulfur sensitization centers varies from hole trap to shallow electron trap, and deep electron trap.     

Results of the development of the technique for using nuclear photoemulsions in the experiment on the search for double neutrinoless beta decay

The last results on the preparation of the experiment on the search for double neutrinoless decay using emulsion chambers with molybdenum filling are presented. The results of testing emulsions prepared by the OJSC “Slavich Company” are presented. Algorithms for recognizing electron tracks in rectilinear and curvilinear portions are described.     

Risk evaluation and protection against ionizing radiation

The advent of nuclear reactors ushered in an era of increasing number of sources of ionizing radiations. However, the potential of ionizing radiations to cause harmful effects was recognized soon after the discovery of x-rays and radioactivityi.e. long before the building of nuclear reactors. Therefore, protection against ionizing radiations has been of paramount concern and has guided the development of atomic energy and related fields. The advances in technology in general resulted in an increase in accidents causing injury and death. It was realised that even medicines, food additives and a host of other substances of daily use had injurious side effects. Smoking was found to be extremely harmful. From these emerged the concepts of quantitative and relative risks. This article discusses briefly the concept of riskvis-a-vis ionizing radiations and approaches to protection against them.     

UV- and γ-sensitization of latent tracks in polyethylene terephthalate

Photosensitization of polymer polyethylene terephthalate (PET) bombarded with swift heavy ions (Xe) was studied. Ultraviolet (UV)- and γ-irradiation were used for sensitization. Infrared spectroscopy (IR) and reversed-phase high-performance liquid chromatography (HPLC) were used to study the radiolysis products in latent tracks (directly in the sample or in the etching solution). It was found that the exposure of the sample to ultraviolet light results in the transformation of the radiolysis products formed in the tracks into terephthalic acid. Surface defects, detected by AFM, were found to correspond to tracks; their form (cavities and hillocks) and size changing reflect the changing of latent track state. It was found that UV irradiation destroyed the cross-linked regions in the tracks. This process (photodecomposition) was shown to be the key stage of the UV sensitization and the main cause of etching rate increase. The γ-irradiation effect on track etching was found to be almost the same.     

Das Ansprechvermögen eines NaJ(Tl)-Szintillationskristalls im Energiebereich derK- undL-Absorptionskante des Jods (33,2 bzw. 5,2 keV) für Röntgenstrahlen

The response of a Na I(Tl)-crystal to x-rays is measured in the energy region from 3 to 46 keV with a single channel pulse-height analyser. The x-rays of the different photon-energies are produced by excitation of fluorescence radiation of the elements potassium to dysprosium. A proportionality with energy results only in approximation. For photon-energies which correspond to the excitation level of theL- or theK-shell of iodine a minimum of the average pulse-height per unit energyH/E which is proportional to the scintillation efficiency occurs in the energy dependence. The response to electrons is deduced from the response to x-rays. The behaviour ofH/E for x-rays is attributed to the energy dependent scintillation efficiency of the Na I(Tl)-crystal for electrons.     

Modifications in track registration response of PADC detector by energetic protons

It has been well established that different ionising radiations modify the track registration properties of dielectric solids. In an effort to study the response of Polyallyl diglycol carbonate (PADC Homalite) detector towards fission fragment, PADC detectors were exposed to 10⁴ Gy dose of 62 MeV protons and then one set of samples were exposed to fission fragments from a ²⁵²Cf source. Two of these detectors were containing a thin layer of Buckminsterfullerene (C₆₀). The study of the etched tracks by Leitz Optical Microscope reveals that the track diameters are enhanced by more than 70% in the proton irradiated zone as compared to that in the unirradiated zone. Scanning Electron Microscopy was performed after etching the sample in 6 N NaOH at 55°C for different etching times, to study the details of the surface modifications due to proton irradiation of PADC detectors with and without C₆₀ layer. Our observations revealed that the diameters and density of proton tracks have increased with etching time on the surface facing the fullerene layer as well as the other surface. However, a relatively more open structure of the etched surface containing C₆₀ as compared to the bare one may be an indication of the extra damage caused by the energy released upon the destruction of C₆₀ molecules by energetic protons.     

Micro‐Raman spectroscopy and SEM/EDX applied to improve the zircon fission track method used for dating geological formations

The zircon mineral is widely studied in geochronology. In the case of the fission track method (FTM), the age is determined by the density of fission tracks at the zircon surface, which can be observed with an optical microscope after an appropriate chemical treatment (etching). The etching must be isotropic at the zircon grain surface to be used in the FTM, which leads those zircon grains whose etching is anisotropic to be discarded. The only reason for this discarding is the nonuniform morphology of the surface grain seen by optical microscopy, that is, no further physicochemical analysis is performed. In this work, combining micro‐Raman and scanning electron microscopy (SEM) to study the etching anisotropy, it was shown that zircon grains that present at least one area at the surface where the density of fission track is uniform can be used in the FTM. The micro‐Raman showed characteristic spectra of the standard zircon sample either from the areas where there are tracks or from where there are not. The only difference found was in the Raman bandwidths, which were broader for the areas with higher density of fission tracks. This suggests simply a decrease in the relative percentage of the crystalline/amorphous phases at these areas. The SEM/energy dispersive spectrometry (EDX) showed that there were no significant differences in the principal chemical composition at the areas with and without fission tracks. Copyright © 2008 John Wiley & Sons, Ltd.     

Anisotropic etching of charged-particle tracks in crystals

It is well-known that highly-energetic heavily charged particles arising both from the fissioning of heavy elements and from cosmic and solar radiations leave tracks which have been found in glasses and crystal-line minerals recovered from lunar and meteoritic material. It has been shown that an appropriate analysis of these tracks can provide informationabout periods since solidification and the thermal and dynamic history of the specimen, as well as insight into the nature and temporal variation of the cosmic ray flux.^1-2 An understanding of the track registration characteristics of crystals is clearly an important pre-requisite to an appropriate interpretation of the natural tracks. ^3-6 This letter describes briefly some observations we have recently made on one particular aspect of this-the anisotropy in track distributions which seems to result from the inherently anisotropic structure of crystals. This effect seems so far to have received little attention.     

原子核乳胶核-2、核-2载硼、核-2载锂、核-3、核-4、核-5的制备方法和特性

本文简述对质子、α粒子、裂片等灵敏的乳胶核—2、核—3,对所有带电粒子(包括电离本领为最小电离值的电子)灵敏的乳胶核—4、核—5和探测慢中子用的乳胶核—2载硼、核—2载锂的制备方法。鉴定了以上各种乳胶的主要性能并与目前世界水平的原子核乳胶(英国和苏联的乳胶)作了相应的比较。     

Automatic analysis of microscopic photo-pictures of undeveloped and developed nuclear emulsions

Methods of automatic computer analyses of images have large impotence in numerous physical problems with different kinds of radiations, which use such solid-state detectors as nuclear photographic emulsions, plastics and others. We described a method of expanding boundaries of dark areas for such computer analyses of micro-pictures. We demonstrated effectiveness of this method by the example of the search of microcrystals size distributions in two undeveloped nuclear emulsions and similar distribution of background grains in the developed emulsion.     

Radiostability of Allantoin by Using Electron Spin Resonance Spectroscopy

The radiosterilization potential and dosimetric feature of allantoin were investigated through the molecular degradations produced after ultraviolet and gamma irradiation using electron spin resonance, infrared, and ultraviolet spectroscopies and thermal measurement techniques (differential thermal analysis and the glass transition temperature). Although ultraviolet-irradiated allantoin presents no electron spin resonance signal, gamma irradiation exhibited an electron spin resonance signal of triplet appearance. Room temperature and high-temperature line intensity and spectrum area data and their variations with applied microwave power, storage time, annealing time, annealing temperature, and applied radiation dose were analyzed by assuming the production of two different types of radicals having different spectroscopic and decay characteristics. Based on its relatively stable nature toward gamma and ultraviolet radiations, it was concluded that allantoin itself and the products containing it can be sterilized by gamma and/or ultraviolet radiations without creating a great loss in its beneficial effects in the allowed radiosterilization dose limits.     

Nonlinear Analysis of Relativistic Motion of Electrons in Self-Amplified Spontaneous Emission Free-Electron Laser in Ultraviolet and X-Ray Spectral Regions

The free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) is an effective candidate of the coherent optical sources at wavelengths in ultraviolet and x-rays. It requires a relativistic electron beam with extremely high quality and extremely stable transmission. In this paper we analyze the dynamic behavior of the relativistic electron in that device by calculating the entropy-like quantity. Results show that if there is no adiabatic field of the wiggler, the electron beam may have great fluctuation in velocity space and diverge in configuration space.     

Radiation-enhanced and thermostimulated hydrogen release from palladium and zirconium

The results of a mass-spectrometric analysis of hydrogen release from palladium and zirconium samples under the action of accelerated electrons (with an energy of 40 keV and a current density of 3 to 30 μA/cm²) and x-rays (with energies of 40 and 120 keV) are presented. The amount of hydrogen removed from these samples and the residual hydrogen content are monitored via the methods of mass-spectrometry and thermodesorption. The conclusion is made that substantial removal of hydrogen (up to 90% of the initial content) from the analyzed materials can be achieved under the action of electrons and x-rays. It is found that x-ray irradiation can ensure more efficient removal of hydrogen than electron bombardment.     

Avalanche Phenomenon of Superthermal Electrons Measured by SDD with New SPHA during ECRH

Two high performance silicon drift detectors （SDD） are installed at the equatorial port with z = 0 and z = -16.4 cm on HL-2A tokamak, respectively. These SDDs combine with the new and non-conventional software pulse height analyser （SPHA ） successfully developed more recently by us to measure the time evolution of soft x-rays spectra, the thermal and superthermal electron temperatures. The high-quality three-dimensional figure of time evolution for soft x-rays energy spectra is easily obtained by combination of a new SPHA and computer. Therefore, the measurement accuracies and the time resolutions of thermal and superthermal electron temperatures are also improved. The enhancement phenomenon of superthermal electron during electron cyclotron resonance heating （ECRH） can be explained by the combination of superthermal electron avalanche theory and experimental parameters.     

Estimation of chemical abundance of primary cosmic-ray nuclei over Alice Springs using balloon-borne passive detectors

Summary A stack consisting of CR-39 (HCB 0.5%), nuclear emulsions and X-ray films was exposed to primary cosmic rays by a balloon lauched from Alice Springs in 1983 and was flown for 32 hours at an atmospheric depth 9.8 g cm⁻² air. The recovered plastic plates were etched in 7.5 N NaOH solution at 80°C for 96 hours. The major and minor axes of the elliptic etch pits were analysed. About 1112 elliptic etch pits were scanned. The measured integral flux of very heavy (VH) and Fe nuclei above 3.5 GeV/n are in approximate aggreement with the earlier survey of Dokeet al., but yield a flatter energy spectrum when compared to the recent high-energy extrapolated spectrum of Zatsepinet al. The charges of the detected heavy nuclei were also confirmed from delta-ray counting of heavily ionized tracks in nuclear emulsions. The energy of the incident heavy nuclei has been measured from the distribution of opening angles of alpha fragments initiated by heavy nuclei in nuclear emulsions.     

Anomalous electron emission spectra and polarization phenomena in a lead magnesium niobate single crystal

The time dependences of the intensity and the energy positions of fine-structure of the spectra of anomalous electron emission from a polarized lead magnesium niobate (PMN) single crystal irradiated with soft x-rays are investigated experimentally. It is shown that the relaxation time of the electret charge can be determined from the graphs of these dependences, and the depth distribution of the potential in the surface layer of the sample can be determined from the profile of the anomalous electron emission spectrum. Estimates of the fields in the surface layers of a polarized PMN single crystal, obtained from the characteristics of the anomalous electron emission spectra, agree with data obtained by electrophysical research techniques. Fiz. Tverd. Tela (St. Petersburg) 39, 1446–1451 (August 1997)     

Effect of vacuum, oxygen and carbon dioxide on the track registration in SR-90 and CR-39

The molecular structure of SR-90 and CR-39 is very similar except that the average length of carbonate linkages in SR-90 is 1.6 times longer than in CR-39. However, the effect of vacuum and carbon dioxide (CO₂) on the track registration of these two detectors is very different: 1) the sensitivity of CR-39 becomes very low in vacuum; the sensitivity of SR-90 does not go down to zero even after storage in vacuum for a long time; 2) the sensitivity of SR-90 decreases both in air and in vacuum but the original sensitivity can be restored by storing it in CO₂ of 13 atm for several days. We also found that the sensitization of latent tracks by oxygen (O₂) is effective only at the time of irradiation but the sensitization by CO₂ is effective after irradiation.     

On the formation of heavy ion latent tracks in polymeric detectors

Three kinds of polymeric track detectors have been examined by ESR spectroscopy following heavy ion or energetic electron bombardment: (1) Typical nuclear track detectors: makrofol, kapton, terphane; (2) Polymers whose radiolysis under γ-rays or electron beams is well established: PMMA, PE, PP; (3) Polymers in which etchable tracks have not so far been observed e.g. teflon. The influence on the various ESR spectra of the radiation dose, of annealing or chemical etching treatments leads us to suggest that existence of heavy ion latent tracks might be correlated with the formation of “carbon-like” radicals such as produced in polymer pyrolysis.