We have produced thick-foil and fine-pitch gas electron multipliers (GEMs) using a laser etching technique. To improve production yield we have employed a new material, Liquid Crystal Polymer, instead of polyimide as an insulator layer. The effective gain of the thick-foil GEM with a hole pitch of 140 um, a hole diameter of 70 um, and a thickness of 100 um reached a value of 10^4 at an applied voltage of 720 V. The measured effective gain of the thick-foil and fine-pitch GEM (80 um pitch, 40 um diameter, and 100 um thick) was similar to that of the thick-foil GEM. The gain stability was measured for the thick-foil and fine-pitch GEM, showing no significant increase or decrease as a function of elapsed time from applying the high voltage. The gain stability over 3 h of operation was about 0.5%. Gain mapping across the GEM showed a good uniformity with a standard deviation of about 4%. The distribution of hole diameters across the GEM was homogeneous with a standard deviation of about 3%. There was no clear correlation between the gain and hole diameter maps.
@article{arxiv.0910.0406,
title = {Development of Thick-foil and Fine-pitch GEMs with a Laser Etching Technique},
author = {T. Tamagawa and A. Hayato and F. Asami and K. Abe and S. Iwamoto and S. Nakamura and A. Hayato and T. Iwahashi and S. Konami and H. Hamagaki and Y. L. Yamaguchi and H. Tawara and K. Makishima},
journal= {arXiv preprint arXiv:0910.0406},
year = {2010}
}