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

Itzhak Tserruya, BNL, May13, Detector R&D Goals (Feb. 14, 2003) Gain and stability:  demonstrate that the detector can operate at a gain of  demonstrate stability at  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

Itzhak Tserruya, BNL, May13, Detector R&D Goals Detector R&D Goals Gain and stability:  demonstrate that the detector can operate at a gain of  demonstrate stability at  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.

Itzhak Tserruya, BNL, May13, 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.

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 ….

Itzhak Tserruya, BNL, May13, Set-up Mesh GEM1 GEM2 GEM3 PCB Am 241 or Fe mm 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

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

Itzhak Tserruya, BNL, May13, 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

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

Itzhak Tserruya, BNL, May13, 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 Gain Curve: Single GEM with CsI in CF 4 : (II) Effective Gain At 500V *), single GEM effective gain = 20  Expect 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.

Itzhak Tserruya, BNL, May13, 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 !!

Itzhak Tserruya, BNL, May13, CsI Photocathode Stability 5% shadow of Fe 55 support ~15’ Exposure to air 5% shadow of Fe % 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

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

Itzhak Tserruya, BNL, May13, 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

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

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

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

Itzhak Tserruya, BNL, May13, 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 ?

Itzhak Tserruya, BNL, May13, Outlook 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 ….

Itzhak Tserruya, BNL, May13,