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Vertex Detector Development for the Heavy Flavor Tracker at STAR

Vertex Detector Development for the Heavy Flavor Tracker at STAR. A Heavy Flavor Tracker for STAR. C. Chasman, D. Beavis, R. Debbe, J.H. Lee, M.J. Levine, F. Videbaek, Z. Xu - Brookhaven National Laboratory, Upton, NY 11973 S. Kleinfelder, S. Li - University of California, Irvine, CA 92697

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Vertex Detector Development for the Heavy Flavor Tracker at STAR

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  1. Vertex Detector Development for the Heavy Flavor Tracker at STAR Leo Greiner Vertex 2007

  2. A Heavy Flavor Trackerfor STAR • C. Chasman, D. Beavis, R. Debbe, J.H. Lee, M.J. Levine, F. Videbaek, Z. Xu - Brookhaven National Laboratory, Upton, NY 11973 • S. Kleinfelder, S. Li - University of California, Irvine, CA 92697 • R. Cendejas, H. Huang, S. Sakai, C. Whitten - University of California, Los Angeles, CA 90095 • J. Joseph, D. Keane, S. Margetis, V. Rykov, W.M. Zhang - Kent State University, Kent, OH 43210 • M. Bystersky, J. Kapitan, V. Kushpil, M. Sumbera - Nuclear Physics Institute AS CR, 250 68 Rez/Prague, Czech Republic • J. Baudot, C. Hu-Guo, A. Shabetai, M. Szelezniak, M. Winter - Institut Pluridisciplinaire Hubert Curien, Strasbourg, France • J. Kelsey, R. Milner, M. Plesko, R. Redwine, F. Simon, B. Surrow, G. Van Nieuwenhuizen - Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, MA 02139 • E. Anderssen, X. Dong, L. Greiner, H.S. Matis, S. Morgan, H.G. Ritter, A. Rose, E. Sichtermann, R.P. Singh, T. Stezelberger, X. Sun, J.H. Thomas, V. Tram, C. Vu, H.H. Wieman, N. Xu - Lawrence Berkeley National Laboratory, Berkeley, CA 94720 • A. Hirsch, B. Srivastava, F. Wang, W. Xie - Purdue University, West Lafayette, IN 47907 • H. Bichsel - University of Washington, Seattle, WA 98195 Leo Greiner Vertex 2007

  3. Talk Structure • Context and overview • Mechanical • Sensors • Readout • Development and Prototyping with test results Leo Greiner Vertex 2007

  4. STAR Detector at RHIC Leo Greiner Vertex 2007

  5. Direct Topological reconstruction of Charm • Detect charm decays with small ct, including D0 K  • New physics • Charm collectivity and flow to test thermalization at RHIC • C & B Energy Loss to test pQCD in a hot and dense medium at RHIC Method: Resolve displaced vertices (100-150 microns) Leo Greiner Vertex 2007

  6. Inside the TPC ~1m HFT inside STAR TPC PIXEL SSD IST R1 = 9 ladders @ 2.5cm R2 = 12 ladders @ 6.5cm R3 = 12 ladders @ 7.5cm Active length ~20 cm Leo Greiner Vertex 2007

  7. Tracking Resolution by Layer(simulation with MCS) • Goal: graded resolution from the outside  in • TPC – SSD – IST – HFT (single track pointing, without a vertex constraint) • TPC pointing resolution at the SSD is ~ 1 mm • SSD pointing at the IST is ~ 300 mm • IST pointing at the HFT is ~ 250 mm • PIXEL pointing at the VTX is ~ 30 mm Transverse momentum = 700 MeV/c Leo Greiner Vertex 2007

  8. Conceptual Mechanical Structure Three main requirements drive the design. • 20 µm stability for the location of the pixels. • Very low radiation length (stiff low mass / Z structures). • Fast replacement of detector assemblies without rolling out STAR detector or resurveying. (We will construct 4 full detectors) Leo Greiner Vertex 2007

  9. Conceptual Mechanical Structure 33 ladders on 3 removable sections -1 < eta < 1 (20 cm active length) Initial models for FEA analysis Solid model of one conceptual design ALICE style carriers are currently under analysis Close up (beam pipe removed) of Low mass region and sensor ladders Leo Greiner Vertex 2007

  10. Some Prototype Ladder Candidates 2 candidates Minimize Radiation Length Not to scale Carrier Composition Top layer = 70 µm CFC + adh Middle layer = 3.2 mm RVC Bottom layer = 70 µm CFC + adh Outer shell = 140 µm CFC + adh Fill = RVC APS (50µm) X0 = 0.05 % (thinning to 50µm is a standard industrial process) Cable X0 = 0.09 % (4 layer Al conductors on 25 µm Kapton) Carrier X0 = 0.135 % Ladder Total (with adhesive) X0 ~ 0.3 % Leo Greiner Vertex 2007

  11. Mechanical Prototype Testing 80mW / cm2 Heater cable Air Cooling Position Distribution Histogram 50 um Si Leo Greiner Vertex 2007 preliminary

  12. Leo Greiner Vertex 2007

  13. IPHC Functional Sensor Development All sensor families: • 30 x 30 µm pixels • CMOS technology • Full Sensor = 640 x 640 pixel array ~ 2 cm x 2 cm Mimostar 2 => full functionality 1/25 reticle, 1.7 ms integration time (1 frame@50 MHz clk), analog output. (in hand and tested) Phase-1 and Ultimate sensors => digital output (in development) Data Processing in RDO and on chip by generation of sensor. The RDO system design evolves with the sensor generation. Leo Greiner Vertex 2007

  14. HFT PIXEL Readout Functional Goals • Triggered detector system fitting into existing STAR infrastructure (Trigger, DAQ, etc.) • Deliver full frame events to STAR DAQ for event building at approximately the same rate as the TPC (1 KHz for DAQ1000). • Reduce the total data rate of the detector to a manageable level (< TPC rate). • Reliable, robust, cost effective, etc. Leo Greiner Vertex 2007

  15. Mimostar PIXEL Data Flow Highly parallel system 33 parallel readout paths identical to the one shown System Goal: 10 Sensors / Ladder 33 Ladders 135M Pixel Leo Greiner Vertex 2007

  16. Implemented in FPGA on daughter card Raster scan Data examined Per clock cycle Efficiency and accidental rates are comparable to the traditional ADC sum method. Leo Greiner Vertex 2007

  17. Mimostar PIXEL Data Rates (1 KHz) • Rate @ R1 (2.5cm) = 52.9 / cm2 • Rate @ R2 (6.5cm) = 10.75 / cm2 • Rate @ R3 (7.5cm) = 8.76 / cm2 (at L = 1027) • 4 ms integration time • Average event size = 114 KB • Data Rate = 114 MB/sec at 1KHz • 33 fiber optic links Leo Greiner Vertex 2007

  18. Telescope Electronics / RDO MimoStar2 chips on kapton cables MOTHER BOARD DAUGHTER CARD Control PC (Win) STRATIX Acquisition Server (Linux) Leo Greiner Vertex 2007 RORC SIU

  19. STAR Prototype Run Results Sensor head located 1.45m from interaction diamond center. Typical CDS full frame event in one sensor. Clusters are clearly visible above the noise level. • Measured charged particle flux was ~ 3.9 merged clusters per sensor (1.7 ms integration time, L=81026 cm-2s-1). • Noise level of system in the STAR environment was comparable to laboratory and ALS measurements. • Prototype system integrated with STAR Trigger, slow control and run control sub-systems. Events delivered to DAQ standard RDO PC. • TLD measured dose at head position, 325 rad over running time. This scales to an integrated dose of several hundred Krad / run. (RHIC-2 luminosity) Leo Greiner Vertex 2007

  20. Summary • Focused mechanical design has begun with 2 initial designs undergoing FEA analysis and development. • Three element Mimostar2 telescope has been constructed and coupled to a RDO system with on-the-fly data sparsification. • Prototype Mimostar2 system performed measurements of the detector environment at STAR including induced electronic noise. Interfaces into the existing STAR infrastructure are now functional. Future • Complete mechanical design efforts. • New fast digital RDO system. • 2 sector patch of full mechanical (including new beam pipe) and Phase-1 sensors by 2010 run. Leo Greiner Vertex 2007

  21. BACKUP Leo Greiner Vertex 2007

  22. Position Resolution vs. Pt • R-Phi resolution. Blue is normal HFT rad length (0.28 %) while red is double that. Leo Greiner Vertex 2007

  23. Cluster Finder Efficiency Real Data taken with MIMOSTAR2 detectors by IPHC Traditional ADC Sum Method 2 Threshold FPGA method Cut on the central pixel goes from 14 to 8 ADC counts (left to right) every 1 ADC. 1 ADC = 7.1 e-. Leo Greiner Vertex 2007

  24. Prototype 3 Sensor Telescope We tested the functionality of a prototype MIMOSTAR2 detector at the LBNL ALS and then in the environment at STAR during the last three weeks of the 2006-2007 run at RHIC. Our goal was to gather information on: • Charged particle environment near the interaction region in STAR. • Performance of our cluster finding algorithm. • Performance of the MIMOSTAR2 sensors. • Functionality of our interfaces to the other STAR subsystems. • Performance of our hardware / firmware as a system. • The noise environment in the area in which we expect to put the final PIXEL detector. Leo Greiner Vertex 2007

  25. Mimostar2 Telescope test at the ALS 1.2 GeV electrons at the ALS Booster Test Facility Important Due to un-terminated DAC pads on the sensor, our noise level was double the value achieved under ideal conditions at IPHC in France. IPHC =>11-15 electrons at 30º C LBL => 30-35 electrons at 28º C MPV = 49 (Standard) and 43 (Radtol) ADC counts at ~230 electrons Leo Greiner Vertex 2007

  26. Telescope Installed at STAR Magnet Pole Tip Beam Pipe Electronics Box Telescope head – 1.45 m from interaction point just below beam pipe. Leo Greiner Vertex 2007

  27. Distribution of track angles in Mimostar2 telescope Leo Greiner Vertex 2007

  28. Thermal Test Ladder Leo Greiner Vertex 2007

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