1. Itzhak Tserruya, BNL, May13, 20031 HBD R&D Update: Demonstration of Hadron Blindness A. Kozlov, I. Ravinovich, L. Shekhtman and I. Tserruya Weizmann Institute, Rehovot May 13, 2003

2. Itzhak Tserruya, BNL, May13, 20032 Detector R&D Goals (Feb. 14, 2003) Gain and stability:  demonstrate that the detector can operate at a gain of 10 4.  demonstrate stability at 10 4.  operate at 10 4 in presence of highly ionizing particles. Aging effects  aging of GEM.  aging of CsI. Ion back-flow (feed-back)  Response to mip and electrons * demonstrate hadron blindness. * optimize detector operation.  Other issues * CsI quantum efficiency and bandwidth. * CF 4 scintillation.  “Prototype” in-beam test Last missing milestone

3. Itzhak Tserruya, BNL, May13, 20033 Detector R&D Goals Detector R&D Goals Gain and stability:  demonstrate that the detector can operate at a gain of 10 4.  demonstrate stability at 10 4.  operate at 10 4 in presence of highly ionizing particles. Aging effects  aging of GEM.  aging of CsI. Ion back-flow (feed-back)  Response to mip and electrons * optimize detector operation.  Other issues * CsI quantum efficiency and bandwidth. * CF 4 scintillation.  “Prototype” in-beam test  demonstrate hadron blindness.

4. Itzhak Tserruya, BNL, May13, 20034 What happened since Feb. 14, 2003? What happened since Feb. 14, 2003? First attempt to demonstrate hadron blindness using the cosmic trigger failed: we observed only a very small difference in the detector response between a mip and a high energy cosmic muon trigger. Decide to first demonstrate the principle using UV lamp, Am 241 alpha source and Fe 55 x-ray source. System modified to have UV lamp and sources inside the radiator detector box.

5. Itzhak Tserruya, BNL, May13, 20035Outline Measurements with UV lamp  Photoelectron detection efficiency vs. E D  Single and triple GEM gain curve  CsI Photoelectron emission  CsI photocathode stability  UV-photon absorption vs. water content in CF 4 Measurements with Am 241  Charge collection in drift gap vs. E D  Am 241  -spectra vs. E D Conclusions and Outlook  Proof of Principle R&D completed. But ….

6. Itzhak Tserruya, BNL, May13, 20036 Set-up Mesh GEM1 GEM2 GEM3 PCB Am 241 or Fe 55 1.5mm 2mm Detector Box (9 3x 3 cm 2 pads) Powering scheme Independent powering of the mesh R R R R R R = 10M  HV R 2R Resistive chain Powering of triple GEM 50 cm long CF 4 Radiator Detector box D 2 UV Lamp Overall Set-up

7. Itzhak Tserruya, BNL, May13, 20037 CsI Photoelectron Emission HV(+) EDED pA HV(-) EDED pA ( 14.04) ( 24.04) ( 14.04)

8. Itzhak Tserruya, BNL, May13, 20038 Gain Curve: Triple GEM with CsI in CF 4 : (I) Current at PCB pA ETET EDED ETET EIEI G G G TT TT II DD I PE I PE  D Measurements done at E D = 0 I PCB = I PE  D (G  T. G  T. G  I ) = (I PE  D ) G eff  G eff  (G  T ) 3

9. Itzhak Tserruya, BNL, May13, 20039 Gain Curve: Triple GEM with CsI in CF 4 : (II) Effective Gain  V of 20 V  gain increase of factor 3

10. Itzhak Tserruya, BNL, May13, 200310 Gain Curve: Single GEM with CsI in CF 4 : (I) Current at PCB pA E T =500V/1.5mm E D = 0 G TT DD I PE I PE  D I PCB = I PE  D (G  T ) = (I PE  D ) G eff  G eff  (G  T )

11. 11 Gain Curve: Single GEM with CsI in CF 4 : (II) Effective Gain At 500V *), single GEM effective gain = 20  Expect 8 10 3 for triple GEM  Consistent with measurement *) The single and triple GEM effective gains can be compared only at  V GEM =500 since the single GEM gain curve was determined at a fixed E T = 500 V.

12. Itzhak Tserruya, BNL, May13, 200312 Photoelectron Detection Efficiency measure detector response vs E D at fixed gain pA ETET E D (+) ETET EIEI G G G TT TT II DD I PE Very efficient detection of photoelectrons even at negative drift fields !!

13. Itzhak Tserruya, BNL, May13, 200313 CsI Photocathode Stability 5% shadow of Fe 55 support ~15’ Exposure to air 5% shadow of Fe 55 + 6% shadow of Am 241 supports No shadow HV(-) EDED pA Current on mesh measured under vacuum, almost every day, at  V GEM-mesh = 600 V  CsI photocathode is very stable

14. Itzhak Tserruya, BNL, May13, 200314 UV Photon Absorption in H 2 O (in 40 cm of CF 4 ) ~ 10% UV absorption per ppm of water!!!

15. Itzhak Tserruya, BNL, May13, 200315 Charge Collection in Drift Gap: (I) Am 241  -spectra ETET E D (+) ETET EIEI G G G TT TT II DD Am 241 NPNP

16. Itzhak Tserruya, BNL, May13, 200316 Charge Collection in Drift Gap : (I) Mean Amplitude At E D = 0 charge signal drops dramatically as anticipated in our proposal

17. Itzhak Tserruya, BNL, May13, 200317 Charge Collection in Drift Gap : (II) Rate Rate also drops dramatically at E D =0. This was not expected and is not fully understood

18. Itzhak Tserruya, BNL, May13, 200318 Hadron Blindness At slightly negative E D, photoelectron detection efficiency is preserved whereas charge collection is largely suppressed.

19. Itzhak Tserruya, BNL, May13, 200319 Outlook (Feb. 14, 2003) The original goal of completing the detector R&D before the end of 2003 is well within reach. Our TDL:  Last milestone: demonstrate HBD properties of the detector  Start detector design  Repeat all measurements under much better controlled conditions (monitor gas density, monitor oxygen and water content of gas).  Measure the QE of CsI  Measure CF 4 scintillation  Endurance tests  Study gas mixtures: CF 4 – Ne or CF 4 – Ar ?

20. Itzhak Tserruya, BNL, May13, 200320Outlook The original goal of completing the detector R&D before the end of 2003 is well within reach. Our TDL:  Last milestone: demonstrate HBD properties of the detector  Start detector design  Repeat all measurements under much better controlled conditions (monitor gas density, monitor oxygen and water content of gas).  Measure the QE of CsI  Measure CF 4 scintillation  Endurance tests  Study gas mixtures: CF 4 – Ne or CF 4 – Ar ? But ….

21. Itzhak Tserruya, BNL, May13, 200321