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

2. C.Woody, sPHENIX Design Study, 9/7/112 Basic Guidelines Want a low mass gas tracking system that can provide multiple coordinate measurements with a resolution ~ 50-100  m 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)

3. C.Woody, sPHENIX Design Study, 9/7/113 Two Approaches 1.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. 2.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

4. C.Woody, sPHENIX Design Study, 9/7/114 Cylindrical GEM Tracker for KLOE-2 Cylindrical tracker R inner = 12.7 cm, R outer = 23 cm  r  ~ 200  m,  z ~ 500  m 5 KHz/cm 2 rate capability Prototype has been built with small (200x240 mm 2 ) double-mask foils

5. C.Woody, sPHENIX Design Study, 9/7/115 25 May 2010 XV readout A second prototype (same dimensions) will be assembled with the final KLOE-2 readout: XV strips-pads with 650 μ m pitch on a kapton substrate.

6. C.Woody, sPHENIX Design Study, 9/7/116 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  m line-pad produced by Tech Etch X Y

7. C.Woody, sPHENIX Design Study, 9/7/117 Chevron Readout with Floating Strips No floating strips Floating strip patterns PatternResolution Fine Chevron (no Floating Strips)128.2 μm Coarse Chevron (no Floating Strips)183.8 μm Fine Chevron (with Floating Strips)97.6 μm Coarse Chevron (with Floating Strips)104.5 μm Intermediate- Straight Strips113.3 μm Provides good precision coordinate in one direction (e.g., r-  ) and allows for coarser segmentation in other direction (e.g., z) to minimize channel count ~ 100  m

8. C.Woody, sPHENIX Design Study, 9/7/118 MicroTPC Operation of MPGDs E drift 300 V/cm V drift ~2cm/  s V mesh 570 V ATLAS Muon Tracker Trigger Upgrade V.Polychronakos, G.De Geronimo (BNL) Can do the same with GEMs ! Problem with Inclined Tracks o Resolution degrades with tan(theta) o Fine for tracks at small angles (detectors can be inclined to mitigate the effect) o Impractical for larger coverage Furthermore o Induced charge footprint rather large, need better double track resolution o Construction of large area chambers is labor intensive Use time of arrival of ionization to reconstruct track Need both amplitude and time measurement MicroMega

9. C.Woody, sPHENIX Design Study, 9/7/119 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 VMM1 ASIC for MicroMegas for ATLAS BNL Instrumentation Division (G.DiGeronimo)

10. C.Woody, sPHENIX Design Study, 9/7/1110 VMM1 Chip Design Design nearing completion First submission anticipated by Nov 2011

11. C.Woody, sPHENIX Design Study, 9/7/1111 Beta Source Test Stand Use Sr-90 source to produce collimated beam of electrons E max = 2.3 MeV (enough to pass through many cm of gas) Can produce sub-millimeter collimated beam Need to suppress background from  ’s and  ’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 6 mCi 90 Sr source Brass collimator with 0.8 mm hole

12. C.Woody, sPHENIX Design Study, 9/7/1112 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 Hybrid card with APV25 chip SRS crate in Martin’s office.... 10x10 CM GEM with COMPASS readout

13. C.Woody, sPHENIX Design Study, 9/7/1113 GEM TPC Test Stand in BNL Gas Detector Lab Fast Drift TPC Development Double GEM Readout Designed and built by BNL Instrumentation Division GEM Readout TPC for the Laser Electron Gamma Source (LEGS) at BNL 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)