GRIMM GLOW-DISCHARGE X-RAY TUBE

A Grimm glow discharge tube was modified to apply high-voltages of up to 10 kV, For this purpose, the cathode is held by a massive support o f PTFE in a new type of glow discharge tube. Consequently, stable high -voltage discharge plasmas were created only in the hollow anode near the cathode under the following discharge conditions: He gas pressures of 10 similar to 100 Pa, and discharge currents of 0.1 similar to 10 mA. Electrons emitted from the cathode surface are accelerated in the cathode fall region. They have high energies corresponding to the appl ied voltage. X-Rays excited by these high-energy electrons were measur ed in two different configurations: the end-window transmission mode a nd the side-window mode. The X-ray transparent thin-film was used as a n X-ray window in the end-window transmission mode. The X-ray spectra measured in this made were very simple because high-energy continuous X-rays were self-absorbed by the thin film itself. However, the X-ray intensities were weak, because a high-discharge current could not be a pplied in order to protect the thin X-ray window. When using the side- window mode, fast electrons bombarded the target at an incident angle of 45 degrees, and the X-rays emitted from the target surface were obs erved at the takeoff angle of 45 degrees through a Be window. A higher X-ray emission intensity could be obtained in the case of the side-wi ndow by applying higher discharge currents and a cooled target. (C) 19 98 Elsevier Science B.V.