Development of thick-foil and fine-pitch GEMs with a laser etching technique

Abstract

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 µm, a hole diameter of 70 µm, and a thickness of 100 µm 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 µm pitch, 40 µm diameter, and 100 µm 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.

The gas electron multiplier (GEM): Operating principles and applications

“…23 is cross-section through a mechanically drilled, one mm thick fiberglass sheet with 300 mm holes at one mm pitch [52]. Other groups have developed technologies to produce hole patterns on a variety of supports [53][54][55][56][57].…”

Performance verification of the Gravity and Extreme Magnetism Small explorer (GEMS) x-ray polarimeter

“…Ionization electrons created along the photoelectron track drift with a constant velocity in a uniform electric field between the drift electrode and the micro-pattern Gas Electron Multiplier (GEM). 20,21 Drifted charge is then amplified in the GEM holes, and collected on the read-out strips located beneath the GEM. Two-dimensional images of photoelectron tracks are formed from a one-dimensional strip readout using the strip location and arrival time multiplied by the drift velocity.…”

Properties of the flight model gas electron multiplier for the GEMS mission

“…Figure 4 shows the setup for the test described in §3. 3 not a vacuum sealed chamber, we selected Ar/CO 2 (70%/30%) gas mixture, with which many GEM studies have been done. 3 We confirmed that the gain variability did not change with gas, although the absolute value of gain changed.…”

“…3 not a vacuum sealed chamber, we selected Ar/CO 2 (70%/30%) gas mixture, with which many GEM studies have been done. 3 We confirmed that the gain variability did not change with gas, although the absolute value of gain changed. Note that the gas was continuously flowing in this test, so the detector pressure followed the ambient environment.…”

“…Each hole has a pitch is 140 µm and diameter of 70 µm. We have reported the basic performance of our GEM in 1 atm Ar/CO 2 (70%/30%) mixture gas: 3,4 it has the maximum gain as high as 10 4 , small time variability of gain with a standard deviation of less than 0.5% for 3 hours, and a two-dimensional gain uniformity in the area of 9 × 9 mm 2 with a standard deviation of ∼ 4%.…”