Craig Woody BNL RHIC Detector Advisory Committee Review December 19, 2002 A Fast, Compact TPC for Dalitz Rejection and Inner Tracking in PHENIX

C.Woody RHIC Detector Advisory Committee Review 12/19/022  Physics goals  Description of the combined TPC/HBD detector  Main R&D Issues  Goals, milestones, funding Outline

C.Woody RHIC Detector Advisory Committee Review 12/19/023 Low mass lepton pairs and vector mesons Charm and B physics with resolved secondary verticies - low mass tracking just outside vertex detector - allows measurement in both heavy ion and pp running Improved inner tracking for PHENIX - increased h and f coverage (needed for jet and g-jet physics) - tracking through the magnetic field (improves momentum resolution, the ability to measure real low p T tracks, and to reject high p T background tracks) Physics measurements addressed by this detector

C.Woody RHIC Detector Advisory Committee Review 12/19/024 e+e+ e-e- TPC / HBD e-e- e+e+ p p p V0V0 measured in outer PHENIX detectors (P e > 200 MeV/c) Operate PHENIX with low inner B field to optimize measurement of low momentum tracks Identify signal electrons (low mass pairs, r,w,f, …) with p>200 MeV in outer PHENIX detectors Identify low momentum electrons (p<200 MeV) using Cherenkov light from HBD and/or dE/dx from TPC Calculate effective mass between all opposite sign tracks identified as electrons ( e electron > 0.9, p rej > 1:200) Reject pair if mass < 130 MeV Must provide sufficient Dalitz rejection (>90%) while preserving the true signal Strategy for Low Mass Pair Measurement

C.Woody RHIC Detector Advisory Committee Review 12/19/025 Dalitz Rejection and Vector Meson Survival Probability K. Ozawa Survival probability of  is ~85% for Dalitz rejection ratio of 90%. Central Au+Au collisions e e = 100%, p rej = 1:200 (HBD,RICH)

C.Woody RHIC Detector Advisory Committee Review 12/19/026 PHENIX Tracking a decays conversions B DC - DC only - PC1-PC3 matching - Random background P T distribution of charged tracks Drift Chamber Momentum determined by measuring a angle Tracking through the magnetic field will help eliminate backgrounds from decays and conversion which are problematic at high P T PHENIX presently has no tracking inside magnetic field

C.Woody RHIC Detector Advisory Committee Review 12/19/027 PHENIX Inner Magnetic Field ± Configuration BRBR BZBZ z=20cm Field Integrals Inner Coil creates a “field free” (∫Bdl=0) region inside the Central Magnet Inner field itself is non-uniform Tracking with TPC will aid in electron id in HBD

C.Woody RHIC Detector Advisory Committee Review 12/19/028 Tracking at High Field and Vertex Resolution Momentum resolution Impact parameter resolution V. Rykov ++ Configuration B = 9 KG

C.Woody RHIC Detector Advisory Committee Review 12/19/029 TPC/HBD Detector Fast, compact TPC R<70 cm, L< 80 cm, T drift  4 m sec Serves as an inner tracking detector in both HI and pp, providing tracking through the central magnetic field Df = 2 p, | h |  1.0 D p/p ~.02p Provides electron id by dE/dx  e/ p separation below 200 MeV HBD is a proximity focused Cherenkov detector with a ~ 50 cm radiator length Provides electron id with minimal signals for charged particles  “Hadron Blind Detector” GEMs are used for both TPC and HBD TPC Readout Plane CsI Readout Plane Drift regions Readout Pads

C.Woody RHIC Detector Advisory Committee Review 12/19/0210 Rates and Occupancy 100 MeV e - C.Aidala 35 pad rows, 80K channels D R ~ 1 cm, R Df ~ 2 mm D Z ~ 2.5 mm (140 samples) 11M voxels Innermost pad row ~ 3% occupancy Requirement: The TPC should work at the highest HI and pp luminosities Au-Au : L ~ 8 x cm -2 s -1 L x s = 8 x x 7.2 b = 58 kHz dN ch /dy = 150 (min.bias)  ~ 250 trks/evt, 15 trks/ m sec N hits /evt ~ 100K  occupancy ~ 1% p-p : L ~ 2 x cm -2 s -1 L x s = 2 x x 60 mb ( S s = 500 GeV) = 12MHz  ~ 50 events in 4 m sec drift time dN ch /dy = 2.6  ~ 5 trks/evt, 52 trks/ m sec

C.Woody RHIC Detector Advisory Committee Review 12/19/0211 R & D Issues for the TPC  Performance of GEM detectors Stability, gain uniformity, aging Studies of fast drift gases (CF 4, CH 4, mixtures…) - Drift velocities, drift lengths, diffusion parameters, dE/dx, ion feedback,… - Optical transmission into the VUV for use with HBD Optimize spatial resolution  Detector component design Readout plane Field cage Understand E x B effects for drifting charge in non-uniform magnetic field Understand space charge effects (do we need gating ?)  Electronics  Infrastructure issues Requires engineering and integration study (additional manpower needed)

C.Woody RHIC Detector Advisory Committee Review 12/19/0212 GEM Detectors at BNL Several multistage GEM detectors have been obtained from Sauli’s group at CERN and are currently being used for detector studies at BNL B. Yu High precision (100 m m) scanning x-ray source

C.Woody RHIC Detector Advisory Committee Review 12/19/0213 Double GEM Gas Gain Uniformity 5.4keV collimated x-rays (~1mm 2 ) scanned with a 1mmx1mm grid over 9cmx9cm area. Relative Amplitude Good gain uniformity and energy resolution is important for particle id using dE/dx p k p e P (GeV/c) miniTPC 35 pad rows CH 4 dE/dx (keV/cm ) e/ p separation below 200 MeV N. SmirnovB. Yu

C.Woody RHIC Detector Advisory Committee Review 12/19/0214 GEM Spatial Resolution J.Va’vra et.al., NIM A324 (1993) Diffusion Limit s L ~ 80 m m /  35 cm  ~ 500 m m GEM’s produce inherently good spatial resolution due to direct collection of electron signal Must keep channel count low

C.Woody RHIC Detector Advisory Committee Review 12/19/0215 Interpolating Pad Readout Two Intermediate Strips Single Intermediate Zigzag Overall position error: 93µm rms Including ~ 100µm fwhm x-ray p.e. range, 100µm beam width, alignment errors Fine “Zigzag” pattern B. Yu

C.Woody RHIC Detector Advisory Committee Review 12/19/0216 Test Drift Cell Drift Stack E-Field calculation C. Thorn Joint R&D with LEGS Will be used to study Drift velocities Drift lengths Diffusion parameters Energy loss (dE/dx) Study impurities Readout structures Field cage design

C.Woody RHIC Detector Advisory Committee Review 12/19/0217 TPC Readout Readout Pads 35 pad rows, 5K ch/plane D R ~ 1 cm, R Df ~ 2 mm 200 ch readout card 15 cm 5 cm R&D Issues Need to minimize power Distribution of analog and digital signals Low noise, zero suppression Data volume (triggering) Readout features

C.Woody RHIC Detector Advisory Committee Review 12/19/0218 TPC Readout Electronics Options Commercial ADC + FPGA ALICE ALTRO chip Custom ASIC (may only need for preamp/shaper) Considerations Speed (need ~ 40 Mhz) Power (< 100 mW/ch total) Compatibility w/PHENIX readout Cost and availability AD9289 Serial ADC 4 ch / 65MHz / 8 bit ADC each channel AMU/ADC C-Y. Chi

C.Woody RHIC Detector Advisory Committee Review 12/19/0219 HBD Readout Electronics Options Separate (slow) ADC + TDC Fast ADC used to extrapolate T0 measurement Considerations Low noise (signal ~ 40 p.e.’s) Low mass (inside PHENIX accept.) (signals brought to edge of detector) ~ 5K channels - too few for ASIC Needs time measurement ~ few ns C-Y. Chi

C.Woody RHIC Detector Advisory Committee Review 12/19/0220 FY03 R&D Goals Complete TPC test cell Carry out gas studies of TPC with GEM readout Preliminary design of TPC field cage & readout plane Carry out CsI photocathode studies with GEMs Measure CF 4 scintillation (NSLS Feb ’03) Carry out aging studies (GEMs, CsI, CF 4 ) Measure HBD response to hadrons and electrons Define HBD detector configuration Preliminary engineering design and integration study Preliminary design of TPC and HBD electronics Build test setup for TPC and HBD electronic components Improved Monte Carlo simulations

C.Woody RHIC Detector Advisory Committee Review 12/19/0221 Demonstrate proof of principle of TPC with GEM readout Demonstrate proof of principle of CsI + GEM operation Determine feasibility of operation in pure CF 4 (or choose alternative gas) Demonstrate feasibility of combined TPC/HBD detector concept Decide on ALICE ALTRO chip, commercial ADC+FPGA or ASIC for TPC Decide on slow ADC+ TDC or fast ADC for HBD readout FY03 R&D Milestones

C.Woody RHIC Detector Advisory Committee Review 12/19/0222 R&D Goals & Milestones for FY04 & FY05 FY2004 Construct TPC/HBD prototype detectors Construct gas system for prototype detectors Build prototype HBD and TPC electronics Build test setup for TPC and HBD electronics Carry out detailed engineering design and integration study Carry out further detailed Monte Carlo simulations FY2005 Complete engineering and integration design Complete TPC detector design Complete design of TPC readout electronics

C.Woody RHIC Detector Advisory Committee Review 12/19/0223 R&D Budget Request Related R&D Efforts Joint effort with STAR (includes additional equipment costs) LEGS TPC Detector R&D at FIT* TPC w/GEM readout for NLC/TESLA Additional institutional manpower contributions *Florida Institute of Technology - 2 physicists, 1 student interested

C.Woody RHIC Detector Advisory Committee Review 12/19/0224 Additional Slides

C.Woody RHIC Detector Advisory Committee Review 12/19/ cm 55 cm 70 cm CsI Photocathode C.Aidala Single 100 MeV/c electron track GEANT Simulation of TPC/HBD TPC/HBD detector in PHENIX PISA simulation package

C.Woody RHIC Detector Advisory Committee Review 12/19/0226 Fast drift gases - CH 4 and CF 4 10 cm / m s 12 cm / m s 40 cm drift  ~ 3-4 m s Requires high drift field 1 V / cm / Torr CF 4 -Ar 1 KV / cm C 2 H 6 CH 4 C 2 H 2 P10 CF 4

C.Woody RHIC Detector Advisory Committee Review 12/19/0227 Ion Feedback in GEMs Electrons Ions F.Sauli B.Yu Triple GEM

C.Woody RHIC Detector Advisory Committee Review 12/19/0228 Space Charge Distortions E max ~ 1.7V/cm E max ~ 1.4V/cm Distortion field components in TPC volume. RadialAxial 200 GeV Au+Au Ion feedback 10% q ~ 2.5 x rad D x ~ 0.5 mm for 40 cm drift G ~ 10 3 r ~ C/m 3 B. Yu

C.Woody RHIC Detector Advisory Committee Review 12/19/0229 GEM Aging and Discharge Rates Experience from COMPASS Triple GEM greatly reduces discharge probability rate no discharges over months of operation no loss of gain or resolution due to aging S.Kappler, 2001 International Workshop on Aging Phenomena in Gaseous Detectors S.Bachmann et.al., NIM A479 (2002) 294 Triple GEM Aging rate at RHIC Min bias  1.3 x 10 7 trks/sec dE/dx = 80 ion pairs/cm (CH 4 ) Gain = 2 x 10 3 dQ/dt = 64 C/yr, A= 8247 cm 2 dQ/dA = 0.08 mC/mm 2 /yr Triple GEM ArCO 2, G~8.5x10 3

C.Woody RHIC Detector Advisory Committee Review 12/19/0230 Used for measurements of VUV gas transmission and CsI quantum efficiency VUV Spectrometer B.Azmoun

C.Woody RHIC Detector Advisory Committee Review 12/19/0231 Commercial ADC C-Y. Chi

C.Woody RHIC Detector Advisory Committee Review 12/19/0232 Use of ALTRO Chip in PHENIX Backend of the ALTRO chip 15 write clocks signal L1 trigger (write to buffer) L1 (W) L2 trigger (keep the buffer) Read or drop L2 events L1 (W) L2 (keep) L1 (W) L2 (keep) L1 (W) L2 (keep) ALTRO’s event buffer could be divided to 8 * 512 word blocks or 4 * 1024 words blocks Time C-Y. Chi Problem for PHENIX a) no overlapping event buffers (space between L1 triggers could be as short as 4 beam clocks) b) L1 trigger delay is too short (i.e., 15*25 ns = 375 ns)

C.Woody RHIC Detector Advisory Committee Review 12/19/0233 We need to generate a fake L1 trigger every 512*25ns = 12.8  s. ( used as L1 delay buffer ) Our L1 trigger will become ALTRO chip’s L2 trigger. We read the L1 data buffers to a FPGA/ASIC. We will parse our data blocks from ALTRO data buffers Two overlapping TPC data block ALTRO 512 words buffers TPC data block PHENIX L1 Two PHENIX L1 Use of ALTRO Chip in PHENIX C-Y. Chi

C.Woody RHIC Detector Advisory Committee Review 12/19/0234 Implementation Plan Construction (2 years) Detector: $250K Gas System: $250 K Detector mounted electronics: $4.0M (80K Readout $50/ch) Other readout electronics: $500K Total: $5.0 M FY 2003 FY 2004 FY 2005 FY 2006 FY 2007 FY 2008 HBDTPC R&D Operation Construction R&D Construction Operation R&D (3 years) Total: $1.4M (LDRD for $100K in FY 2001 & FY 2002)