[en] A laser charge-exchange device (LCED) for a mass spectrometer is described. Charge exchange is realized during ion beam transmission through a plasma-vapour cloud, produced under pulsed laser radiation interaction with the surface of a solid target. The LCED is placed inside the chamber of an ion laser source between the end electrode of the ion-optical system and inlet slit of the mass spectrometer. Technical ebonite is used as a target in the LCED. The values of charge-exchange coefficients make up ∼ 60% and ∼ 20% for 2⁺-1⁺ and 3⁺-1⁺ ionic components respectively

[en] Ethylene-propylene diene ter-monomer (EPDM) filled with asbestos are widely used as thermal insulation in space vehicles because of its low specific gravity, low temperature flexibility, high ozone and oxygen resistant, superior thermal and ablation characteristics. However, asbestos has been banned worldwide because of its carcinogenic nature. This study was aimed to replace asbestos by environmental friendly and low specific gravity filler, cork in thermal insulation for space vehicles. Various batches of cork filled EPDM were obtained by compounding 0, 10, 20, 40, 50, 60, 70 and 100 Phr (parts per hundred parts of rubber) of cork powder with EPDM in Two-roll-mill in presence of other necessary compounding ingredients. The resulted vulcanizates were characterized for mechanical, thermal and ablation performances. It was observed that cork loadings significantly enhanced tensile strength and hardness of EPDM. However, elongation at break of EPDM decreased with the increase of cork concentration. Moreover, no significant reduction in density of EPDM was obtained instead of compounding with lower specific gravity cork powder. Temperatures cures in Thermo-gravimetric analysis shifted to lower temperature with increasing of cork percentage in the formulation. Furthermore, char formation of the EPDM composites decreased with the increase of cork Phr in the composition which was the indication of degrading thermal stability of EPDM by cork powders. It can be concluded that on the basis of mechanical properties asbestos can be replaced by cork powder however, cork filled EPDM exhibited inferior thermal properties as compared to asbestos filled EPDM. (author)

[en] In case of criticality accident, the characteristics of the radiation produced (photons and neutrons) must be determined in order to specify the risks to an exposed individual. The SNAC2 area dosemeter, an improvement of SNAC50, makes it possible to restore neutron spectrum shapes from the integral data of a few activation detectors, and to calculate the useful dosimetric quantities with the appropriate conversion factors. The thermal and epithermal components of the spectral distribution are determined by means of 1) bare copper and 2) cadmium shielded gold and copper. The fast component of the spectrum is obtained with three threshold detectors, viz indium, nickel and magnesium allowing to assess the parameters of a representative mathematical function. The spectrum indexes make it possible to find out the variations of the spectral di stribution in order to obtain the dosimetric quantities ranges. An ebonite disk (sulfur activation) is included for the assessment of the dosimetric quantities to an exposed individual. The measurements of the sample activity are carried ou t by gamma spectrometry, except for ebonite which requires beta activity countin g. Data processing is carried out on a microcomputer. The BASIC programme is lis ted in appendix

[en] The geometrical patterns of dielectric breakdown like electrical trees, surface discharges and lightning are known to be fractal in nature. These fractal patterns can be analysed numerically using fractal dimensions and lacunarity. Surface tracking occurring in high voltage insulation systems is a very complex phenomenon and more so the shapes of tracking patterns. It has been fairly well established that the shapes and the underlying parameters causing tracking have a one-to-one correspondence and therefore methods to describe and quantify these patterns must be explored. This contribution reports preliminary results of such a study wherein two-dimensional (2D) tracking patterns of gamma irradiated ethylene propylene diene monomer (EPDM) were analysed and found to possess fairly reasonable pattern discriminating abilities. This approach appears promising and further research is essential before any long-term predictions can be made. It is also interesting to note that the ac tracking resistance of EPDM decreases with an increase in the radiation dose. The erosion depth affected by radiation was also studied

[en] This paper presents the results of experimental studies of the mechanical characteristics of base isolation systems for secondary equipment. The Friction Pendulum System (FPS), Natural Rubber Bearing (NRB) and High Damping Rubber Bearing (HDRB) were selected for the isolation systems. 400kg design loads were selected and 10 ton actuators are used in vertical and horizontal direction in this test. Finally, it is noted that the shape factor and damping characteristics of rubber bearing and length of curvature of the concave surface of FPS are the important factor of the isolation systems

[en] Among the complaints to the foods that consumers bought, the proportion of the mixing of alien substances is more than 20%. The number of the cases classified by the kinds of alien substances, and that of minerals and animal substances are shown. The causes of the mixing of alien substances are classified into those due to the mixing in raw materials, production places, processing machines and workers. In case of using primary products as raw materials, the alien substances closely related to those raw materials are difficult to detect, such as bones and hairs in animal meat, fish bones, egg shells and fruit seeds. There are problems and limitation in the inspection of alien substance mixing by visual or touching inspection, metal detectors and the visual inspection of X-ray radiographs. The judgement of the presence of alien substances by automatically processing X-ray radiograph information has been tried one or two-dimensionally. The X-ray alien substance detector KD901G adopted the one-dimensional line sensor type, and its features are shown. The effective introduction of the X-ray alien substance detector, its comparison with metal detectors, and the safety of workers against radiation exposure and the safety of inspected foods are discussed. (K.I.)

[en] An experimental device and the method for measuring thermal conductivity in solids at low temperatures are described. The electric circuit of temperature stabilization and control of the investigated object is studied along with possibilities for avoiding complementary thermal fluxes. The results on measuring thermal conductivity in ebonite and the Cenusil silicon rubber in the temperature range from 4.5 up to 20 K are presented as an example. The unit is constructed on the base of commercial helium cryostat. The maximum thermal flux power through a sample is 0.1 W. Maximum sample dimensions are: length-50 mm, diameter-30 mm. Temperature measuring is performed using semiconductor resistance thermometers. Measurement error of the T₁-T₂ value constitutes about 7.5% when using sensors gauged with an accuracy of not less than 0.2% and choosing temperature difference on a sample about T₁-T₂=0.08 T₁+T₂/2. Thus, the unit permits to measure thermal conductivity of solid bodies at low temperatures with an error < 10% in the 4.2-20 K temperature range

[en] Rubber compounds may be sensitized to cure or partially cure when subjected to irradiation. If certain layers of a rubber laminate are treated with sensitizing materials and other layers wth densensitizing materials a composite is produced having cured and uncured layers after it has been subjected to irradiation. This technique enables the production of composite laminates in which predetermined layers have predetermined physical characteristics which are desirable in the manufacture of the ultimate end product, for example, automotive tires. Several chemicals have been found to accelerate the cure of rubber compounds by irradiation and several have been found which inhibit the cure. Paradichlorobenzene (PDCB) and certain of the thioetherpolythiols are effective cure promotors. Effective retarders include aromatic oils, sulfur, sulfur cure accelerators and some rubber antioxidants and/or antiozonants of the substituted diphenylamine type. The dosage of irradiation is dependent upon several variables: the type of rubber, the promotor or retarder utilized, the level of the promotor or retarder, the thickness of the layer of material, the thickness of adjacent layers of materials, the sequence of the layers of material, the number of the layers of material and whether the irradiation is applied to one or both sides of the composite strip. The dosage may be controlled by the amount of energy employed so that the electrons do not completely penetrate the entire strip. This results in the irradiaton of part of the strip, but not the entire strip. (LL)

[en] Ablatives are heat-shielding materials used to protect aerospace substructures. These materials are sacrificial in nature and provide protection primarily through the large endothermic transformation during exposure to hyper thermal environment such as encountered in re-entry modules. The performance of certain ablatives was reported in terms of their TGA/DTA in Advanced Materials-97 (pp 57-65). The focus of this earlier research resided in the consolidation of interface between the refractory inclusion and the host polymeric matrix to improve thermal resistance. In the present work we explore the scope of transpiration cooling in ablative performance through flash evaporation of liquid incorporated in the host EPDM (Ethylene Propylene Diene Monomer) matrix. The compression-molded specimens were exposed separately to plasma flame (15000 C) and oxyacetylene torch (3000 C) and the back face transient temperature is recorded in situ employing a thermocouple/data logger system. Both head on impingement (HOI) and parallel flow (PF) through a central cavity in the ablator were used. It is observed that transpiration cooling is effective and yields (a) rapid thermal equilibrium in the specimen, (b) lower back face temperature and (c) lower ablation rate, compared to conventional ablatives. SEM/EDS analysis is presented to amplify the point. (author)

[en] An ebonite is a hard rubber containing 30% of sulphur and has been widely used as insulation materials. Sulphur has been also well known as an activation detector. Induced³²P from the reaction of ³²S(n,p) ³²P emits the beta particle with a half-life of 14.27d and a maximum energy of 1.71 MeV. In this study, ebonite discs with 50 mm in diameter were irradiated to ²⁵² Cf neutrons and 2.1 Sv neutron doses were delivered. After irradiation, beta particles emitted from activated ebonite discs were directly measured with the shielded end-window GM counter. Measured counts per 30 minutes were up to 1,200 counts. It could be concluded that the ebonite discs could be useful as a fast neutron dosemeter for radiological protection purposes, principally in criticality dosimetry