Contribution of cadmium to the total amount of positron creation in a reactor-based slow positron beamline

In the slow positron beamline at the Kyoto University Research Reactor (KUR), positron creation was enhanced by increasing the gamma-ray intensity at the positron source via the reaction of¹¹³Cd(n, γ)¹¹⁴Cd. To achieve this, a cadmium (Cd) cap was attached to the positron source, surrounding it, and thus, without intentional cooling, the temperature was able to reach near the melting point of Cd via nuclear heating. In this study, the degree to which the Cd cap contributes to the quantity of positron creation was estimated by using the Monte Carlo calculation code PHITS (Particle and Heavy Ion Transport code System), which simulates radiation transportation and interaction with matter. As a result, the number of positrons created was found to become 2.0 ± 0.1 times higher by using the Cd cap at the KUR slow positron beamline. The use of the Cd cap was confirmed to be significantly effective for enhancing positron creation

Slow-positron beamline temperature rise reduction at Kyoto University Research Reactor

Temperature rises of a reactor-based slow-positron beamline at Kyoto University Research Reactor (KUR) were measured during reactor operation and solenoid-coil excitation. During KUR operation at 5 MW, the temperature of the top of the beamline reached 300 °C. This temperature which is close to the melting point (321 °C) of Cd was used to enhance positron generation. On the other hand, the temperature of the flange supporting the beamline was approximately 50 °C and it was sufficiently low in terms of the strength of the beamline. The temperature of the top of the beamline was successfully reduced to 240 °C by introducing a He gas flow around the vacuum duct of the beamline. Beamline temperatures calculated using a finite element method were in agreement with measured temperatures. Such calculation is useful for future experiments with longer or irregular KUR operation

<Advanced Energy Conversion Division> Advanced Energy Structural Materials Research Section

3-1. Research Activities in 202

Effect of self-ion irradiation on hardening and microstructure of tungsten

AbstractThe irradiation hardening and microstructures of pure W and W–3%Re for up to 5.0 dpa by self-ion irradiation were investigated in this work. The ion irradiation was conducted using 18 MeV W6+ at 500 and 800°C. A focused ion beam followed by electro-polishing was used to make thin foil specimens for transmission electron microscope observations. Dislocation loops were observed in all the irradiated samples. Voids were observed in all of the specimens except the W–3%Re irradiated to 0.2 dpa. The hardness was measured by using nanoindentation. The irradiation hardening was saturated at 1.0 dpa for pure W. In the case of W–3%Re, the irradiation hardening showed a peak at 1.0 dpa. The correlation between the microstructure and hardening was investigated

Use of imaging plates at near saturation for high energy density particles

Copyright 2008 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Review of Scientific Instruments, 79(10), 10E910, 2008 and may be found at http://dx.doi.org/10.1063/1.298767

Thermodynamics of the superconducting state in Calcium at 200 GPa

The thermodynamic parameters of the superconducting state in Calcium under the pressure at 200 GPa were calculated. The Coulomb pseudopotential values ($\mu^{\star}$) from 0.1 to 0.3 were taken into consideration. It has been shown, that the specific heat's jump at the critical temperature and the thermodynamic critical field near zero Kelvin strongly decrease with $\mu^{\star}$. The dimensionless ratios $r_{1}\equiv \Delta C(T_{C})/C^{N}(T_{C})$ and $r_{2}\equiv T_{C}C^{N}(T_{C})/H^{2}_{C}(0)$ significantly differ from the predictions based on the BCS model. In particular, $r_{1}$ decreases from 2.64 to 1.97 with the Coulomb pseudopotential; whereas $r_{2}$ increases from 0.140 to 0.157. The numerical results have been supplemented by the analytical approach.Comment: 7 pages, 6 figure

Calibration of imaging plate for high energy electron spectrometer

Copyright 2005 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Review of Scientific Instruments, 76(1), 013507_1-013507_5, 2005 and may be found at http://dx.doi.org/10.1063/1.182437