sPHENIX GEM Tracker R&D at BNL

1. sPHENIX GEM Tracker R&D at BNL Craig Woody BNL sPHENIX Design Study Meeting September 7, 2011

2. Basic Guidelines • Want a low mass gas tracking system that can provide multiple coordinate measurements with a resolution ~ 50-100 mm • Use in conjunction with the silicon tracking system to provide additional track finding capability (particularly in heavy ion collisions) as well as improved momentum resolution • Probably want a cylindrical geometry in the central region and a planar geometry in the forward direction • Low mass is especially important for eRHIC (particularly in the electron direction) C.Woody, sPHENIX Design Study, 9/7/11

3. Two Approaches • Design and build a cylindrical GEM detector capable of working in heavy ion collisions (readout can also work for planar chambers) • Cylindrical GEM trackers have been built and operated ( KLOE). However, KLOE cylindrical GEM tracker was designed for very low multiplicity e+e- collisions (XV strips read out only on ends) • sPHENIX detector must work in high multiplicity HI collisions  Readout must deal with high local occupancy • Want to provide multiple layers of coordinates with lowest possible mass “MicroTPC” configuration can provide multiple coordinates with a single readout plane. Need to study various types of readout planes. • Investigate the design of a fast, compact TPC that could be used in either the central region and/or possibly the forward direction (depending on the configuration of the magnetic field) • TPC would provide the most number of tracking coordinates with the lowest possible mass  Important for measuring low energy electrons in the forward direction at eRHIC C.Woody, sPHENIX Design Study, 9/7/11

4. Cylindrical GEM Tracker for KLOE-2 Cylindrical tracker • Rinner = 12.7 cm, Router = 23 cm • srf ~ 200 mm, sz ~ 500 mm • 5 KHz/cm2 rate capability Prototype has been built with small (200x240 mm2) double-mask foils C.Woody, sPHENIX Design Study, 9/7/11

5. XV readout A second prototype (same dimensions) will be assembled with the final KLOE-2 readout: XV strips-pads with 650 μm pitch on a kapton substrate. 25 May 2010 C.Woody, sPHENIX Design Study, 9/7/11

6. Y X Line and Pad 2D Readout R.Majka (Yale) Concept: Have both X & Y readout on the same single layer Normal strips in one direction on top Connect pads to strips on bottom with vias for other direction Can also do with 3 coordinates 300 mm line-pad produced by Tech Etch C.Woody, sPHENIX Design Study, 9/7/11

7. Chevron Readout with Floating Strips Provides good precision coordinate in one direction (e.g., r-f) and allows for coarser segmentation in other direction (e.g., z) to minimize channel count Floating strip patterns No floating strips ~ 100 mm C.Woody, sPHENIX Design Study, 9/7/11

8. MicroTPC Operation of MPGDs ATLAS Muon Tracker Trigger Upgrade V.Polychronakos, G.De Geronimo (BNL) • Problem with Inclined Tracks • Resolution degrades with tan(theta) • Fine for tracks at small angles (detectors can be inclined to mitigate the effect) • Impractical for larger coverage • Furthermore • Induced charge footprint rather large, need better double track resolution • Construction of large area chambers is labor intensive • Use time of arrival of ionization to reconstruct track • Need both amplitude and time measurement MicroMega Edrift 300V/cm Vdrift ~2cm/ms Vmesh 570 V Can do the same with GEMs ! C.Woody, sPHENIX Design Study, 9/7/11

9. VMM1 ASIC for MicroMegas for ATLAS • 64 channels • adj. polarity, adj. maximum charge (0.11 to 2 pC), adj. peaktime (25-200 ns) • derandomizing peak detection (10-bit) and time detection (1.5 ns) • real-time event peak trigger and address • integrated threshold with trimming, sub-threshold neighbor acquisition • integrated pulse generator and calibration circuits • analog monitor, channel mask, temperature sensor • continuous measurement and readout, derandomizing FIFO • few mW per channel, chip-to-chip (neighbor) communication, LVDS interface BNL Instrumentation Division (G.DiGeronimo) C.Woody, sPHENIX Design Study, 9/7/11

10. VMM1 Chip Design Design nearing completion First submission anticipated by Nov 2011 C.Woody, sPHENIX Design Study, 9/7/11

11. Beta Source Test Stand 6 mCi 90Sr source Brass collimator with 0.8 mm hole • Use Sr-90 source to produce collimated beam of electrons • Emax = 2.3 MeV (enough to pass through many cm of gas) • Can produce sub-millimeter collimated beam • Need to suppress background from b’s and g’s • Can rotate to various angles • Easier and faster than cosmic rays • Use for preliminary studies before going to test • beam for higher precision measurements C.Woody, sPHENIX Design Study, 9/7/11

12. CERN Scalable Readout System (SRS) Crate with one Front End Card and one ADC arrived at BNL in July - Capable of reading out ~ 2000 channels 10x10 cm GEM detector with COMPASS readout also arrived in July Currently setting up to to run in Gas Detector Lab at BNL 10x10 CM GEM with COMPASS readout Hybrid card with APV25 chip SRS crate in Martin’s office.... C.Woody, sPHENIX Design Study, 9/7/11

13. Fast Drift TPC Development GEM Readout TPC for the Laser Electron Gamma Source (LEGS) at BNL Double GEM Readout Designed and built by BNL Instrumentation Division GEM TPC Test Stand in BNL Gas Detector Lab Custom ASIC • 32 channels - mixed signal • 40,000 transistors • low-noise charge amplification • energy and timing, 230 e-, 2.5 ns • neighbor processing • multiplexed and sparse readout • Basis for ATLAS VMM1 chip G. De Geronimo et al., IEEE TNS 51 (2004) C.Woody, sPHENIX Design Study, 9/7/11