No.7（2012）3.Cross-section observation and development of the PTFE electrode foil for a GEM

Masaki Wakabayashi, Kazuki Komiya, Kohei Fujiwara, Takeshi Kobayashi

  The gas electron multiplier (GEM) is a detector for capturing X-rays and charged particles through gas multiplication. Problems faced by the GEM are that the yield rate is approximately 75% and the GEM foil is easy damaged by abnormal discharges. Thus, improving both the processing method and the reliability is necessary. At first, to analyze the causes for failure, we tried three methods for making the cross-section of the GEM foil. Of the three methods, the ultra-microtome is the most effective method for obtaining the cross-section of the GEM foil. Next, we evaluated both candidate materials for the GEM foil and the micro-fabrication method used for the through-holes in the GEM. As a result, we selected PTFE as the insulator material for the GEM foil and fabricated copper electrodes on the PTFE film by magnetron sputtering. We succeeded in fabricating through-holes with no short-circuits by using femto-second laser processing.

Keywords
Gas electron multiplier, Detector, Electrode foil, Failure analysis technique, Magnetron sputtering, Laser microfabrication

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