1. 1 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news New THGEM test in the COMPASS hall New THGEM test in the COMPASS hall Preparation of the test Preliminary check with Fe source The LED light sources The test area in the COMPASS hall Measurements with analog r/o Measurements with digital r/o

2. 2 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Motivations for this test From: - CsI photoelectron extraction and backscattering measurements - first indications from simulation of fields and trajectories - THGEM performances with different gases we concluded that a methane based gas mixture is needed We experienced difficulties in reaching high gains without sparks  Decision to build a quadruple THGEM  Test it with light source  Obtain authorization to use flammable gas  Try to characterize the time response The COMPASS RICH test area seemed to be the easiest choice

3. 3 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Preparation of the test Design and build a new chamber with: -9 HV connectors and 2 gas connectors, - anode segmented in 16 pads, - a fused silica window (Heraus Suprasil II) - a flange for light source mounting Design and build mechanics for: - testing the LED light source behavior - interfacing the light source to the chamber Find low wavelength LED and best possible driver Most important: involve many COMPASS colleagues for the test

4. 4 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Choice of THGEM “Standard geometry”: -Thickness = 0.4 mm - Hole diameter = 0.4 mm - Pitch = 0.8 mm - Rim = 10 μm Production: - Laser + etching - First set from ELTOS Second best after “global etching”

5. 5 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news The chamber anode drift THGEM 1 THGEM 2 E induction E transfer 2.0 mm CsI THGEM 3 THGEM 4 2.0 mm

6. 6 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news 55 Fe source: rate ~ 200 Hz, primaries: ~ 200 Fields: Drift = Induction = 1.5 kV/cm Transf.1 = Trasnf.2 = 1.0 kV/cm THGEM voltages: ΔV2 = ΔV3 = 1400 V First test: triple THGEM, Ar-CH4 50-50 ΔV1 (V) largest gain with 55 Fe source so far THGEM: 30x30; 0.4, 0.4, 0.8, 10 μm Spacings: 2.0 mm (drift sp. = 4.0 mm)

7. 7 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news 55 Fe source: rate ~ 200 Hz, primaries: ~ 200 Fields: Drift = Induction = 1.5 kV/cm Transf.1 = Trasnf.2 = 1.0 kV/cm THGEM voltages: ΔV2 = ΔV3 = 1400 V First test: triple THGEM, Ar-CH4 50-50 THGEM: 30x30; 0.4, 0.4, 0.8, 10 μm Spacings: 2.0 mm (drift sp. = 4.0 mm) Drift: + 160 pA Top1: + 30 pA Bottom1: 0 pA Top2: + 110 pA Bottom2: - 50 pA Top3 : + 710 pA Bottom3: - 610 pA Anode: - 340 pA Very interesting currents:

8. 8 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news CsI deposited on one half only CsI deposited by Miranda Van Stenis (A. Braem’s lab.) on 17/02/2009 8 pads corresponding to the CsI coated half 8 pads corresponding to the uncoated half CsI coated halfuncoated half

9. 9 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news We bought 2 LED’s of 255 nm from “Laser 2000” company, Paris

10. 10 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news First test of “255 nm LED” Check that the LED is properly working (no specifications available) -power DC mode direct/inverse and check current - try to see glow from UV light on fluorescent liquid - characterize the LED emission spectra - estimate and tune the LED light output in pulsed mode with PM We then mounted it on the chamber with CsI coated THGEM: - no measurable photocurrent seen - with multiplication both signals and currents are seen Conclusion: we can use it for the test Colleagues from Freiburg bought a “270 nm LED” able to provide pulses of 600 ns length, up to 40 MHz

11. 11 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Mechanics for the LED LED quartz window THGEM

12. 12 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Study of the LED with a MAPMT LED quartz window THGEM MAPMT 50 μm pin-hole

13. 13 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Both seem to emit in a region where CsI has extremely low Q.E., if any. Using an Avantes spectrophotometer we measured the emission spectra for both “255 LED” and “270 laser LED” Emission spectra for LED “255” nm and “270” nm

14. 14 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Methane Detection Head Methane Leaks Collector Gas Distribution rack Bottle of Ar/CH 4 50/50 THGEM Detectors Emergency Button Power plugs Electronics Racks Sliding door Bottle of Ar/CO 2 70/30 Safety box for radioactive sources COMPASS RICH THGEM TEST AREA We have been authorized to use flammable gas: Ar-CH 4 50-50 or pure CH 4 for two weeks, after some interactions with the safety officers and filling of a finite number of safety papers.

15. 15 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news “255 nm” LED continuous current: Voltages: 7150 7150 5525 5325 3775 3575 2150 1950 620 Amplitude spectra with “255 nm LED” For high rates the analog r/o piles up the signals; lowering the rate we reach a minimum slope and lowering it further the event rate changes without changes in the slope of the spectra => single photon

16. 16 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Voltages: 7150 7150 5525 5325 3775 3575 2150 1950 620 Amplitude spectra from pulsed LED Pulsed LED provides single photoelectrons with probability between 0.1% and 1%

17. 17 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Estimate of the gain: ~ 100,000 The chamber was very stable in these conditions

18. 18 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Random pulses – high frequency Fixed frequency: 9kHz Voltages: 7100 7100 5500 5300 3750 3550 2150 1950 620 Amplitude spectra with “Freiburg LED”

19. 19 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Voltages: 7100 7100 5500 5300 3750 3550 2150 1950 620 Using FREIBURG pulsed LED:

20. 20 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Delta V1 increased by 30V

21. 21 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news Saturation of Amplifier Changing the GAIN of the Amplifier Zooming the low amplitude part There is no clear evidence of “Polya” shape

22. 22 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news First look at timing properties

23. 23 Fulvio TESSAROTTO GDD meeting, CERN, 01/10/2008 Trieste THGEM news First look at timing properties