Double Thick Copper THGEM First Measurements Gabriele Croci

Double Thick Copper THGEM: First Measurements Gabriele Croci, Elena Rocco, Matteo Alfonsi April, the 23 rd 2010 GDD Meeting

Thick Copper THGEM • The idea is to use a thicker copper (400 µm) on bottom THGEM electrode in order to have the converter directly on the GEM. • Geometrical Parameters – – – Thickness = 0. 8 mm Hole Diameter = 0. 5 mm Pitch = 1 mm Top Copper Thickness = 0. 035 mm Bottom Copper Thickness = 0. 4 mm • Square Pattern • This THGEM should have a very high real gain but a unitary effective gain Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Experimental Parameters • 3 x 3 cm 2 Thick. Cu GEM (mounted on a 10 x 10 cm 2 metallic plate) • Gas Mixture: Ar/CO 2 70%/30% • Radioactive Sources: Cu 8. 9 Ke. V X-Rays & Fe 55 5. 9 ke. V X-Rays • Ortec 142 i. H Preamplifier and Ortec 450 research amplifier Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Detector Setup Drift Thick Cu THGEM Top Thick Cu THGEM Bottom A ED X-Rays Bottom Read. Out B 2. 8 mm 3. 1 mm 5. 1 mm Bottom Read. Out EI 3. 1 mm 100 p. F 1 MΩ Ortec 142 IH Preamplifier Gabriele Croci (GDD-CERN) - Thick Copper THGEM Drift Gap Transfer 1 Gap Induction Gap

Qualitative Studies of Signals on Thick. GEMTop Bottom and on the anode: THGEM Leakage Field ET 1 Gap = 3. 1 mm Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Yellow Anode Blue THGTBottom • • • Inverted ET 1 Field Ed = 585 V/cm VTHGT = 2478 V ET 1 = - 51 V/cm VTHGB = 1886 V Eind = 322 V/cm Anode Trigger Bottom. Trigger Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Yellow Anode Blue THGTBottom • • • Zero ET 1 Field Ed = 585 V/cm VTHGT = 2478 V ET 1 = 0 V/cm VTHGB = 1870 V Eind = 322 V/cm Anode Trigger Bottom. Trigger Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Yellow Anode Blue THGTBottom Anode Trigger • • • Correct ET 1 field Ed = 585 V/cm VTHGT = 2478 V ET 1 = 64 V/cm VTHGB = 1850 V Eind = 322 V/cm Bottom. Trigger Neg Bottom. Trigger Pos Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Yellow Anode Blue THGTBottom • Zero ET 1; Low VTHGB • Ed = 585 V/cm • VTHGT = 2478 V • ET 1 = 0 V/cm • VTHGB = 500 V • Eind = 322 V/cm Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Zero ET 1 Field: Try to increase VTHGB until we are be able to see a signal on the anode • • • Zero ET 1 Ed = 585 V/cm VTHGT = 2478 V ET 1 = 0 V/cm VTHGB = 1570 Eind = 1290 V/cm Yellow Anode Blue THGTBottom Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Zero ET 1 Field: Try to decrease Eind until we lose the signal on the anode • • • Zero ET 1 Ed = 585 V/cm VTHGT = 2478 V ET 1 = 0 V/cm VTHGB = 1570 Eind = 258 V/cm Yellow Anode Blue THGTBottom Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Zero ET 1 Field: Try to increase VTHGB up to see a signal on the anode • • • Zero ET 1 Ed = 585 V/cm VTHGT = 2478 V ET 1 = 0 V/cm VTHGB = 1736 V Eind = 258 V/cm Yellow Anode Blue THGTBottom Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Zero ET 1 Field: Put Higher Induction field • • • Zero ET 1 Ed = 585 V/cm VTHGT = 2478 V ET 1 = 0 V/cm VTHGB = 1736 V Eind = 1290 V/cm Yellow Anode Blue THGTBottom Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Inverted ET 1 Field: Put Higher VTHGB • • • Zero ET 1 Ed = 585 V/cm VTHGT = 2478 V ET 1 = -83 V/cm VTHGB = 2098 V Eind = 322 V/cm Yellow Anode Blue THGTBottom Gabriele Croci (GDD-CERN) - Thick Copper THGEM

ET 1 Gap Increased to 5. 1 mm Parameters of plots of the following slide: Ed = 357 V/cm VTHGT = VTHGB = 2500 V ET 1 = -60 V/cm Eind = -65 V/cm Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Study of the signals: Yellow THGBot_Bot – Blue THGTop_Bot Trig THGT_Bot; Conversion ED Trig THGB_Top; Conversion ET 1 Trig THGB_Bot; Conversion ED Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Considerations • Triggering on THGT_Bot we always see a signal on THGB_Bot (Photon converted in the Drift Gap) • Triggering on THGB_Bot we have two situations: – Conversion in Drift Gap We see a big and long negative signal on THGB_Bot and a smaller negative one (~5 times) on THGT_Bot – Conversion in ET 1 Gap we see a small and short signal only on THGB_Bot and a small positive signal on THGT_Bot • THGB_Bot signal is about 5 times higher than THGT_Bot signal unitary condition not satisfied • If I put Et 1 < -60 V/cm, I immediately lose the signal on the bottom THGEM Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Timing Studies (1) Delay ~ 15 µs Total Distance between THGT_Bot and THGB_Bot = 5. 1 + 0. 8 + 0. 4 = 6. 3 mm <v. Drift> = 420 µm/µs Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Timing Studies (2) THGT_Bottom Signal Duration ~ 4 µs; Rise Time ~ 500 ns Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Timing Studies (2) THGB_Bottom Signal Duration ~ 15 µs; Rise Time ~ 5. 2 µs Gabriele Croci (GDD-CERN) - Thick Copper THGEM

PH Spectra: THTB_Bot Signal with and without ion tail Att=20 db Gabriele Croci (GDD-CERN) - Thick Copper THGEM

PH Spectra: THGB_Bot Att=40 db Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Voltage Scan: THGB_Bot Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Voltage Scan: THGT_Bot ? ? ? Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Voltage Scan: Energy Resolution Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Voltage Scan: Ratio Gabriele Croci (GDD-CERN) - Thick Copper THGEM

Conclusions • Strange behaviour of THGT Voltage Scan analyze the data in a more detailed way • It seems that the unitary condition is not satisfied • With such a high voltages, the detector is very unstable we need to reduce the FR 4 thickness • We can try to go for Ar/CO 2 90%/10% but I guess that the detecor will become even more unstable • In order to get the unitary condition, we can try to reduce the hole diameter Gabriele Croci (GDD-CERN) - Thick Copper THGEM