1. Jason Kamin May 17 th, 2006 1 Title Slide!! HBD

2. Jason Kamin May 17 th, 2006 2 Di-lepton Physics Diverse Physics: –Vector Mesons –Dalitz –Correlated semi- leptonic decays. –Chiral Restoration?? Staple in High Energy Physics. Arguably the most difficult measurement in Heavy Ion Physics

3. Jason Kamin May 17 th, 2006 3 Invariant Mass Spectrum from e + e - Major problem: Huge combinatorial background mostly due to: γ- conversions & π 0 Dalitz decays. We need a new detector, that can ID e’s from these two sources. Full ID of background: eID & chargeID & (m inv < m π ) Good enough: eID & P-hat (two e’s with small opening angle) Hadron-Blind Detector: Cherenkov for eID. Field free region of PHENIX (p-hat) All Pairs Combinatorial Pairs Signal Pairs Lighter particles have smaller opening angles!! Field can be canceled in a small region around beampipe. >100x photoelectron blob relativistic electrons φ π

4. Jason Kamin May 17 th, 2006 4 Unfocused Cherenkov “Blobs” (r,phi) – bins grow with radius (x,y) – uniform bins Cherekov Radiation e-e- No room for traditional optics (ie. focusing mirror). Cherenkov light collected as an unfocused blob. 1.5 m^2 photosensitive region Low radiation length: minimize photon conversions. Charged particles from collision will pass through: ionization must not interfere with photoelectron detection. Can YOU design this detector???

5. Jason Kamin May 17 th, 2006 5 Gas Electron Multiplier (GEM) Two copper layers separated by insulating film with regular pitch of holes Just add the photocathode HV creates very strong field such that the avalanche develops inside the holes By the way: no photon shine back onto photocathode 150μ The original idea by F.Sauli (mid 90s) US Patent 6,011,265 Traditionally CHARGED PARTICLE detectors (not photons)

6. Jason Kamin May 17 th, 2006 6 The concept Get a GEM Put a photocathode (CsI) on top photoelectron from Cherenkov light avalanches in the high density E-field Use more GEMs for larger signal Pick up the signal on pads What about ionizing particles (hadrons)? We need a mesh with a reverse voltage on it to blow electrons away!!! HV We have a detector sensitive to UV and blind to ionizing particles! ~150 μ m

7. Jason Kamin May 17 th, 2006 7 At slightly negative E d, photoelectron detection efficiency is preserved whereas charge collection is largely suppressed. Charge collected from ~150μ layer above top GEM Hadron Blindness: UV photons vs charged particles

8. Jason Kamin May 17 th, 2006 8 Dilepton pair Beam Pipe HBD Gas Volume: Filled with CF 4 Radiator (n CF4 =1.000620, L RAD =50 cm) Cherenkov light forms “blobs” on an image plane (r BLOB ~3.36cm) Triple GEM detectors (12 panels per side) Space allocated for services Windowless Cherenkov Detector Radiator gas = Avalanche Gas Electrons radiate, but hadrons with P < 4 GeV/c do not Pcb pad readout (~ 2x2 cm 2 ) 5 cm 55 cm e-e- e+e+  Pair Opening Angle The HBD Detector CsI photocathode covering GEMs

9. Jason Kamin May 17 th, 2006 9 The Clean Tent at USB Entrance Foyer Level of Clean Room evaporator glove box GEM storage vessel laminar flow hood

10. Jason Kamin May 17 th, 2006 10 The Evaporator Evaporation Chamber Quantum Efficiency Station Magnetically coupled driver for moving the GEMs inside the vacuum. on loan from INFN Roma

11. Jason Kamin May 17 th, 2006 11 The Evaporation Chamber ~24 hrs to pump down vessel vacuum ~10 -8 mbar no water!! Evaporate 4 GEMs simultaneously Molybdenum boats GEM GEM mounting box w/ wheels on track Harpoon for moving mounting box CsI AC Boats are in series so they must be brought up to temperature slowly (~10 min) 250 – 450 nm layer of CsI at rate of ~2 nm/sec

12. Jason Kamin May 17 th, 2006 12 The Quantum Efficiency Station GEM with CsI Molybinum boats GEM mounting box w/ wheels on track Harpoon for moving mounting box AC γ e-e- e-e- ~ 100 V ~ 2mm ampmeter GEM w/ CsI mirror reference PMT mesh (e - collection) Xe lamp MgF 2 window (λ=160,185,200 nm)

13. Jason Kamin May 17 th, 2006 13 Quantum Efficiency Excellent QE. Comparable to best in the world. QE constant across GEM. It’s crucial to maintain high QE after production. x-coordinate across GEM Relative QE (%) 40 0

14. Jason Kamin May 17 th, 2006 14 55 Fe

15. Jason Kamin May 17 th, 2006 15 Summary JasonTom Bill Liz Hadron Blind Detector is crucial to the low-mass dielectron spectrum. Excellent QE is achieved at the Stony Brook production facility. The HBD prototype is installed in PHENIX and being tested. We have seen the light!! (it’s working). Final HBD is scheduled to be installed in late Aug 2006.

16. 16 The PHENIX HBD Collaboration A.Dubey, Z. Fraenkel, A. Kozlov, M. Naglis, I. Ravinovich, D.Sharma, I.Tserruya Weizmann Institute of Science B.Azmoun, D.Lynch, R.Pisani, C.Woody Physics Dept., Brookhaven National Lab J.Harder, P.O’Connor, V.Radeka, B.Yu Instrumentation Division, Brookhaven National Lab W. Anderson, A. Drees, J. Franz,T. Hemmick, R. Hutter, B. Jacak, J. Kamin, M.McCumber, A. Milov, A. Sickles, A.Toia Stony Brook University C.-Y. Chi Nevis Labs, Columbia University H. Hamagaki, S. Oda, K. Ozawa University of Tokyo L.Baksay, M.Hohlmann, S.Rembeczki Florida Institute of Technology D. Kawall Riken M. Grosse-Purdekamp University of Ilinois

17. Jason Kamin May 17 th, 2006 17 Conclusions (not mine, stolen. Needs work. )  Strong hadron rejection can be achieved with good photoelectron efficiency  High gain/stable GEM operation can be obtained in pure CF 4  A windowless Cherenkov detector can in principle achieve a very high N 0 when used in conjunction with a with deep VUV transmitting gas such as CF 4 However, impurities such as O 2 and H 2 O can cause a significant loss of Cherenkov light (O 2 and H 2 O must be kept at the few ppm level)  GEM detectors work in the high multiplicity environment at RHIC  No significant aging effects are observed in either GEMs or CsI photocathodes for intergated charges well in excess of what is expected to be reached at RHIC  Need to meaure N 0 in a realistic detector and test a fully functional prototype in the PHENIX

18. Jason Kamin May 17 th, 2006 18 Final HBD Design parameters: Acceptance at nominal position: |  | ≤0.45,  =135 0 Acceptance at retracted position: |  | ≤0.36,  =110 0 GEM size: 22 x 27 cm 2 # of detector modules per arm: 12 GEM frame: 5 mm wide, 0.3mm cross Hexagonal pad size: a = 15.6 mm Number of pads per arm: 1152 Dead area within acceptance: 6% Rad. length within acceptance: box: 0.92%, gas: 0.54% Weight per arm: <10 kg Exploded view

19. Jason Kamin May 17 th, 2006 19 HBD Response Simulation Total signal: 62 e = 29 dE/dx + 33 Cherenkov Blob size: single pad 12%, more than one pad 88% Normal case, no absorption in CF 4, no lamp shadowing, realistic losses and conservative N 0 = 840 cm -1 Total signal: 38 e = 29 (dE/dx) + 9 (Cherenkov ) Blob size: single pad response =78%  very similar to data Includes 20 cm absorption length in CF 4, lamp shadowing, realistic losses and conservative N 0 = 840 cm -1

20. Jason Kamin May 17 th, 2006 20 Illuminate photocathode with UV lamp, measure DC current to mesh Measure gain with 55 Fe source Keep I mesh < 1 nA/cm 2, gain ~ 5-10 x 10 3 Continuously irradiate photocathode, measure gain periodically No significant aging effects of either the GEM or CsI photocathode were observed up to ~ 150  C/cm 2 (~ 10 years at RHIC) Gain was found to increase with exposure time (Possible charging effect in GEM foils ?) Aging Tests Test both GEM and CsI photocathode

21. Jason Kamin May 17 th, 2006 21 Clean Room Survey Laminar Table Better than Class 1Laminar Table Better than Class 1 Foyer could be better (improve seal to main tent) Dirty spot in the back (Air Conditioner filters!!!) FoyerLaminar Table ??? Outside

22. Jason Kamin May 17 th, 2006 22

23. Jason Kamin May 17 th, 2006 23 AC

24. Jason Kamin May 17 th, 2006 24

25. Jason Kamin May 17 th, 2006 25 Hadron Blindness: Response to Electrons detector response vs E D at fixed gain Efficient detection of photoelectrons even at negative drift fields E D = 0 pA ETET E D (+) ETET EIEI G G G TT TT II DD Charge collected from 150μ layer above GEM

26. Jason Kamin May 17 th, 2006 26 Pad Dimensions 3.16 cm 2.74 cm3.36 cm photoelectron blob WHAT ABOUT A PICTURE OF A GEM HERE TOO!!