Radiation Physics and Chemistry (1977)最新文献

The high-dose gamma ray response (10³ - 5×10⁵ Gy) of radiochromic film dosimeters, with ten kinds of plastic matrices (polychlorostyrene containing 1 or 25% C

The responses and stabilities of the polyhalostyrene and nylon films were only slightly affected by the different atmospheres of irradiation, but there were marked differences of response for the other film types. The dyed cellulose triacetate films and polyvinylchloride films are generally more sensitive in N₂O and O₂-deprived atmospheres than in air or in O₂, but the opposite is true for the dyed polyvinyl butyral and aromatic nylon films. The dyed cellulose triacetate and dyed polychlorostryrene with 1% C

Irradiation of silicon power rectifiers with electrons of 12 MeV energy has been carried out. Minority carrier lifetime τ, forward voltage V_F, reverse recovered charge Q_RR, reverse recovery time t_RR for the diodes, circuit commutated turn-off time t_q, and on-state voltage V_T for the thyristors are measured as a function of dose. Power diodes and thyristors obtained from 〈111〉 neutron transutation or phosphorus doped float-zone silicon slices having 120Ωcm and 65Ωcm starting resistivity respectively and Ga-diffused are irradiated at room temperature. A linear relationship between carrier lifetime of irradiated diodes and electron dose is found and the calculated damage coefficients are k_τ = 1.1x10^-8 cm²/s and 7.2x10^-9 cm²/s for the low-level and high-level lifetimes respectively at 25°C. For irradiated thyristors the linear relationship between turn-off time and dose yields k_tq = 3x10^-9 cm²/s at 125°C. Electron irradiation also affects the resistivity of the starting n-type silicon, increasing it of ≈ 15Ωcm for radiation doses > 1×10⁴ Gy. A dose rate effect on the electrical characteristics of the devices using pulses of different duration is analyzed. Annealing studies are carried out at 150 °C, 200°C and 360°C to assess the stability of the defects produced by the electron bombardment by monitoring the variation of the electrical characteristics of the irradiated devices in the temperature range of interest. DLTS measurements performed on electron irradiated power rectifiers have revealed a complex defect pattern. The E₁ defect level (E_c-0.17 ev) is the principal recombination center that controls lifetime following room temperature irradiation. The energy levels and capture cross sections of these irradiation induced-defects are reported. This study confirms that lifetime control in silicon power devices is feasible by high energy electrons. The major advantages of this technique over metallic diffusion or ⁶⁰Co γ-irradiation methods are: better quality, lower processing cost and higher device yields. Annealing after irradiation is important to ensure long-term device stability.

The addition of polyfunctional monomers when compounding radiation cured polymers increases the crosslinking efficiency of the radiation. Various monomers were added to a flame retarded base formulation to investigate their crosslinking efficiency. These samples were then crosslinked by electron beam irradiation and their physical properties were measured. Variations were noted in tensile strength, elongation, and gel/swell tests. The monomers studied were di^-, tri^-, and tetra-functional, and represented a wide range of effects on the physical properties.

In 1981 Kronenberg, McLaughlin, and Siebentritt proposed measurement of radiation dosage using optical waveguides with leuco dye solutions. Based on this work, an opti-chromic system was proposed at the Fourth International Meeting on Radiation Processing. This opti-chromic system has been evaluated by McLaughlin and Radak. The opti-chromic waveguide system may be even more valuable for other applications which involve measurements with special requirements and configurations.

The linearity of the radiation response can be enhanced by proper selection of leuco dye concentration, waveguide materials, organic activator solvents, and trace chemical additives. This paper presents experimental data resulting from an examination of the organic solvents TEP, DMSO, and n-propyl alcohol in relationship to stability, temperature characteristics, and radiation chemistry.

The experimental data indicates that by varying the types and combinations of organic solvents, special opti-chromic waveguides can be fabricated to measure various radiation ranges under a variety of temperature ranges which have stability over time.

This report describes the latest informations of the utilization of electron processing systems in Japan and electron processing systems for cross-linking of wire insulations and curing of plywood coating in Asian countries and the latest features of electron processing systems.

The rate of the reaction of the radiolytically produced reduced species in acetonitrile with various protic solutes (alcohols and water) was measured by the competition method and by directly following the rate of disappearance of the reduced species in pulse radiolytic experiments. The rate constants thus obtained were correlated with the pK_a of the protic additives. This correlation leads to the conclusion that the reaction occurs via a proton transfer. Temperature effect studies on the rate of this reaction lead to the conclusion that the reactive species is the dimer anion radical (CH₃CN)^-₂.

From the decrease of yield of solvent fluorescent excited states in cyclohexane by the electron scavenger CO₂ the efficiency of formation of this excited state from ion recombination is found to be 0.4 ± 0.1. Energy transfer studies using cis-decalin as a solute seem to provide evidence for the formation of higher excited states in irradiated cyclohexane with a yield of 0.8 (100 eV)^-1. These states are capable of fast energy transfer to the solute.

The gamma irradiator GBZ 81 is a specific onion irradiator and easy to use for all types of bulk-cargo irradiation. It largely works automatically. The irradiator may be integrated into the storing line of onions from the field to the warehouse. Its output is about 7.5–8.0 ton/h, corresponding to 2000–3000 ton per harvest period. The efficiency of the gamma irradiator is about 13%. Considering the low building cost, the simple design and the automatic operation of the irradiation plant this comparatively low efficiency is acceptable, especially if the cobalt-60 sources are used during the remaining times of the year in another facility, e.g. a multipurpose irradiator of a higher efficiency. This programme is realized at present by the combination of a new multipurpose gamma-irradiation facility and some onion irradiators of the type GBZ 81.