Prestige Si数字透视故障检修

故障现象GE公司Prestige Si数字胃肠机,在正常透视十几个患者后,突然出现图像变暗直至消失,操作面板上触摸屏显示:125kV;0.4mA。故障分析与检修出现故障后关机,间隔半小时重新开机,又能恢复正常使用。后来该故障出现的频率越来越高,逐步发展到透视一两个患者就出现上述故障。     

Use of a Si(Li) detector as β spectrometer

The aim of this work is to demonstrate the capability of a Si(Li) detector for the measurement of β spectra, despite the energy absorption in air and in the Be window. A simple source holder fixes the source on the symmetry axis at 3 mm from the detector window. The β-sources are produced by evaporation on a plastic backing plate. Absorbing materials between the source and the sensitive volume of the detector are 3 mm of air, a Be window, 0.1 μm Si and 20 nm of gold. A model of the detector was created for β spectra simulation using the MCNP 4A code. Experimental spectra of ¹⁴C, ¹⁴⁷Pm, ²⁰⁴Tl, ⁹⁰Sr/⁹⁰Y were compared with simulated spectra.     

The effect of γ-ray irradiation on magnetic properties of electromagnetic Fe–Si (97%–3%) sheets

The effect of γ-ray irradiation on magnetic properties of electromagnetic steel sheets has been investigated. The measurements were carried out using transformer Fe–Si (97%–3%) sheets. The energy losses and the dependence of the relative permeability as well as of the differential permeability on the magnetic field strength before and after irradiation were measured. The measurements show that the energy losses in the electromagnetic sheets, for a maximum magnetic induction of 1.0 tesla at the frequency of 50 Hz, decreased to less than 10% after irradiation in comparison with the energy losses before irradiation. Also the value of the saturation magnetic induction decreased by about 10% after irradiation. However, the values of the relative permeability in the region of rotation of magnetization domains after irradiation decreased on the average by 5%, whereas the values of their differential permeability around each working point remained unchanged.