Thick Copper GEM Gabriele Croci and Matteo Alfonsi

Thick Copper GEM Gabriele Croci and Matteo Alfonsi on behalf of GDD Group January, the 21 st 2010

Thick Copper GEM Pictures • The idea is to use a thicker copper (100 µm) on bottom GEM electrode in order to have the converter directly on the GEM. • This GEM has both top and bottom copper 100 µm thick • This GEM should have a very high real gain but a unitary effective gain Close to Kapton Copper Hole Diameter = 200 µm ; Away form Kapton Copper Hole Diameter = 260 µm Kapton Hole Diameter = 145 µm; Pitch = 500 µm Square Hole Pattern Gabriele Croci (GDD-CERN) - Thick Copper GEM 2

Experimental Parameters • 10 x 10 cm 2 Thick. Cu GEM • 2 x (10 x 10 cm 2 Std. GEM) (biconical, kapton hole diameter 50 μm, copper hole diameter 70 μm, pitch 140 μm, thickness 50 μm) • Gas Mixture: Ar/CO 2 70%/30% • Radioactive Sources: Cu 8. 9 Ke. V X-Rays • Ortec 142 i. H Preamplifier and Ortec 450 research amplifier Gabriele Croci (GDD-CERN) - Thick Copper GEM 3

Detector Setup 8. 9 ke. V Copper X-Rays Drift A 13 mm Drift Gap ET 1 = 2. 5 k. V/cm 2 mm Transfer 1 Gap ET 2 = 2. 5 k. V/cm 3 mm Transfer 2 Gap ET 2 = 3 k. V/cm 2 mm Induction Gap ED = 0. 1 k. V/cm Thick Cu GEM GThick. Cu. GEM B Bottom GEM 1 C Bottom GEM 2 GAmplification Anode 1 MΩ G: effective gain Ortec 142 IH Preamplifier Gabriele Croci (GDD-CERN) - Thick Copper GEM 4

First Simulations The aim would be to have a very high real gain and a unitary effective gain. In order to obtain this, almost all secondary electrons should be collected by the thick Bottom copper GEM and it should be possible to see a signal from a single thick copper GEM. Gabriele Croci (GDD-CERN) - Thick Copper GEM 5

Thick Cu GEM Gain Measurement We tried to see signal only from Th. Cu GEM, by reading the bottom electrode, But we did not manage. In order to measure its gain we used the amplification stage after it. The maximum voltage that this GEM can stand is 420 V and its maximum gain was less than 5 It is possible to get an unitary effective gain but not a very high real gain!!! Gabriele Croci (GDD-CERN) - Thick Copper GEM 6