1. CsI/GEM-based RICH for SoLID A RICH Technology Alternative. SoLID Collaboration Meeting 2/3/20121 Thomas K Hemmick Stony Brook University, RHIG

2. 4 months at 11 GeV 2 months at 6.6 GeV statistical error bar σ A /A (%) shown at center of bins in Q 2, x sea quarks standard model test higher twist charge symmetry violation Physics Drivers    /e - is few hundred or less  eID assisted by calorimeter, typical req. on RICH.  Total error ~0.5% in each x,Q 2 bin via 0.3% stats:  Require high efficiency or “bright” RICH. SoLID Collaboration Meeting 6/14/2012 2 CsCs PhysicsContami- nation Precision PVDIS1-2%0.1% SIDIS<1%1%

3. SoLID RICHes:  SoLID Solenoidal Large Intensity Device.  Two varaints:  PVDIS– e threshold device (light RICH)  SIDIS– e/  threshold device (heavy RICH).  Concern principally centers on several issues:  Strength & orientation of B at photo-sensor.  Backgrounds producing false hits (c.p. in window)  CsI photocathode GEM (ala PHENIX HBD)  Windowless promises less (or different) background.  Inexpensive.  Aggressively being developed for other contexts:  EIC Ring-Imaging Development ( ,K,p @ 80 GeV/c)  Medical Imaging (Breskin et. al.) SoLID Collaboration Meeting 2/3/2012 3 PVDIS SIDIS

4. EIC R&D  BNL Administers the program for generic research into detector technologies for EIC.  Multiple applications consider CsI photo- cathode readout:  Central barrel proximity-focus using C 6 F 14 liquid.  End cap ring-imaging for ,K,p @ 80 GeV/c  TPC/HBD for tracking, dE/dx, eID.  SoLID bootstraps from these developments:  UVa funded for GEM planar tracking R&D.  SBU funded for End Cap RICH & Mirror development.  Other opportunities available for collaboration (e.g. heavy gas forward RICH). SoLID Collaboration Meeting 6/14/2012 4

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7. HBD Principle 7 Readout Pads e-e- primary ionization g HV photo electron Readout Pads charged particle or photon primary ionization HV BRIGHT! ~20 photo-electrons in 50 cm of gas: Principle source of photons at LOW WAVELENGTH! dN/d ~ 1/ 2 QE falls linearly as increases. Single electron gain ~10 4 (a bit limited by the CsI). You can see a blob…single p.e. difficult. More GEMs = higher gain…BUT there is a cost in hadron blindness. Reverse Bias (HBD)Forward Bias

8. At slightly negative E d, photoelectron detection efficiency is preserved whereas charge collection is largely suppressed. Background #1: Charge collected from ~150μ layer above GEM. Background #2: Charge deposit in lower layers. With n GEMs, hadron gain reduced from G n to G n-1 Background #3: Scintillation (CF 4 scintillates at 160 nm). Necessary program Hadron Blindness: Hadron “Near-Sighted”

9. Applications  PHENIX HBD (2 yrs):  Windowless, 50 cm, unfocussed.  22 p.e. per blob, N 0 =322 (!)  EIC & sPHENIX:  Develop CsI technology to measure rings.  Mirror technology (reflectivity at low ).  Precision position measurement via charge division.  REQUIRES MUCH HIGHER GAIN!  SoLID (light cherenkov only)  Threshold detector using mirror (background issues)  Less sensitive to neutron and low-E gammas. SoLID Collaboration Meeting 2/3/2012 9 Au+Au

10. Caveats! SoLID Collaboration Meeting 6/14/2012 10  Single photon response varies w/ technology.  Affects efficiency & background rejection.  Gas Avalanche requires more light! SiPM PMT HBD Pulse height Distribution PMT HBD =10 photoelectrons Efficiency vs PMT HBD Cut = 2 p.e.

11. Caveats 2 SoLID Collaboration Meeting 6/14/2012 11  Background rates also as  HBD worse rejection with background below cut.  HBD better rejection with background above cut. SiPM PMT HBD Pulse height Distribution PMT HBD =0.2 photoelectrons Efficiency vs PMT HBD Cut = 2 p.e.

12. December 2011 Hall A Background Studies High purity recirculating gas ~1 ppm H 2 O & O 2 CAMAC DAQ LeCroy High Voltage GEM detector o Divider box allows for 'on the fly' stack size changes Neutron Counters BF 3 10 B + n  7 Li + 4 He o Bare counter (slow) o Wax counter (slow & fast) Scintillators SoLID Collaboration Meeting 2/3/2012 12

13. Neutron Data SoLID Collaboration Meeting 2/3/2012 13 Bare Neutron Counter shows few, if any, counts while beam is on target. Some runs show rates of ~0.6 Hz. Average rate for Fast (plus Slow) neutrons ~35 Hz. Counter sensitivity: 1.9 cps per 1 thermal neutron/cm 2 Typical background = 18 thermal neutron/cm 2 inside wax NOTE: Background up to 50X higher while tuning. 60 Hz

14. GEM Detector SoLID Collaboration Meeting 2/3/2012 14 Legend: Blue = +40 V Teal = +20 V Pink = 0 V Green = -20 V Red = -40 V As the stack has few GEMs, you are able to achieve a better hadron blindness. This is because ionization can occur in the gap between the first and second GEM. For fewer GEMs we were unable to get small signals above the hardware threshold.  Not Blind Blind Solid (threshold)EIC (rings)

15. MIPs When the difference is taken between the forward- most and reverse-most bias, one should see MIPs. Best for fewer GEMs via the G n-1 principle. Normally we expect ~15 p.e. for 1.5mm of CF 4. Here tracks are inclined ~17 o above horizontal. 15/sin(17) ~ 50….SWEET! SoLID Collaboration Meeting 2/3/2012 15 Not Blind Blind Solid (threshold) Not Blind – Blind = MIP

16. Threshold Rates  Reverse Bias always better.  3-GEM stack always better.  Rate 0.07-0.08 Hz/nA with 2 p.e. threshold.  Requiring neighbor coincidence 10X better:  0.008 Hz/nA with 2 p.e. threshold. SoLID Collaboration Meeting 2/3/2012 16 Single Pad Neighbor Coincidence Scale by photon/total

17. EIC HBD  “Beam” consists of scattered electrons & pions.  Particles must be collimated.  Remote table position control.  eID via “TCAL” (PreShower & Shower). SoLID Collaboration Meeting 2/3/2012 17

18. Pad Plane  10x10 cm 2  Pad Plane for Ring Imaging ala FGT  SoLID would use 4 pads in this area (1/4 ring – quad coincidence).  5 GEMs for high gain  SoLID would use 3 GEMs.

19. Optics  Optics defined by GEM size (R ring < 5 cm).  Rad-length for SoLID perfect fit for optics!  Should see 20 p.e. or more.  Better than 0.1 ppm O 2 & H 2 O  Mirror @ 80% by manufacturer spec.  Gain above 70000. SoLID Collaboration Meeting 2/3/2012 19

20. eID works  Local beam dump and other obstacles forced detector to beyond 35 degrees.  During beam tuning, saw nicely separated electron band.  Band disappeared after beam stopped scraping.  Took only a few million triggers:  Two PC deaths; One HV mainframe death; SoLID Collaboration Meeting 6/14/2012 20 e 

21. Rare Signals  Most triggers are false coincidence.  44/80000 events have a collimated track.  A few of those show an HBD hit in reverse bias.  No electrons yet spotted… SoLID Collaboration Meeting 6/14/2012 21

22. Funded R&D Beam  Second Beam Test (FNAL likely).  Ordinary MgF 2 cutoff <140nm.  Overcoat thickness = thin film reflection max!  Develop in house evaporation. SoLID Collaboration Meeting 2/3/2012 22 Interference Maximum 8’ diameter vessel

23. Summary  SoLID benefits from EIC-funded R&D efforts where applicable with small changes:  U.Va funded for planar GEM tracker work.  SBU funded for CsI-RICH && high quality mirrors.  Other opportunities…  CsI photo-cathodes are an interesting alternative to PMT readouts and may offer:  Reduced cost  Reduced background sensitivity.    CsI provides an excellent backup strategy for the SoLID light gas RICH SoLID Collaboration Meeting 6/14/2012 23