1. Progress in the Development of a B-Factory Monolithic Active Pixel Detector Samo Stanič for the Belle Pixel Group M. Barbero 1, A. Bozek 4, T. Browder 1, F. Fang 1, M. Hazumi 3, J. Kennedy 1, N. Kent 1, S. Olsen 1, H. Palka 4, M. Rosen 1, L. Ruckman 1, S. Stanič 2, K. Trabelsi 1, T. Tsuboyama 3, K. Uchida 1, G. Varner 1 and Q. Yang 1 1 University of Hawaii, 2 University of Tsukuba, 3 High Energy Accelerator Research Organization (KEK), 4 H. Niewondiczanski Institute of Nuclear Physics SVD Upgrade Meeting 2005/04/12

2. Samo Stanič for the Pixel Group - 2005/4/12 1 Conventional solutions (Si strips) will not work… 2. Improve impact parameter resolution? ~10%~4% ~2% Present Belle SVD2 Motivation SuperKEKB luminosity increase: L~1.5 x 10 34 → L~5 x 10 35 cm -2.s -1 1. Reduce SVD occupancy Present : layer 1 of SVD ~10% occupancy / 200 Krad.yr -1 Upgrade: Super-Belle ~ 20 – 50 x (?) expected background increase

3. Samo Stanič for the Pixel Group - 2005/4/12 2 70mm Solution at hand: “Striplet” New type of short DSSD sensors: “Striplets” –Shorter strip length, strips arranged at 45 degrees –Small triangle dead region exists (about 7 % in layer1) –Readout by APV25 chip developed for CMS @ CERN –Occupancy is reduced to ~5% @L= 10 35 /cm 2 /s –Operation confirmed in beam-test @ KEK by the Vienna Group … Higher luminosity than that requires pixel type sensor! Z rφ Dead region 14mm 10mm U V From T. Kawasaki-san, Niigita-U, 6 th HL WS, 2004/11

4. Samo Stanič for the Pixel Group - 2005/4/12 3 1.Low occupancy 2.Fast Readout Speed 3.Radiation Hardness 4.Thin Sensor 5.Full-sized detector prototype Natural alternative - Pixel type sensor Technology Choice CAP1 – basic functionality CAP2 – pipelined readout CAP3 – full-size/speed PVD1.0 Jun. 2004 @ KEK T943 Dec. 2004 @ FNAL MAPS XTEST2, LHC hybrid pixels T569 ~ Jun. 2005 @ KEK  Near Term (SVD2 Layer 1 drop-in)  IR upgrade Preliminary Design Report Requirements R&D steps Prototypes

5. Samo Stanič for the Pixel Group - 2005/4/12 4 Belle Pixel Sensor Evolution PVD1.0 CAP3 CAP2 pipelined readout full-size/speed CAP1 basic functionality 2005 2004 2003 time final detector technology choice

6. Samo Stanič for the Pixel Group - 2005/4/12 5 Candidate: Monolithic Active Pixel Sensor Current DSSD Because of large Capacitance, need Thick DSSDs -- APS can be VERY Thin 300  m MAPS 10  m Key Features Thermal charge collection (no HV) Thin - reduced multiple-scattering,  conversion, background  target NO bump bonding – fine pitch possible (8000x geometrical reduction) Standard CMOS process - “System on Chip” possible

7. Samo Stanič for the Pixel Group - 2005/4/12 6 Continuous Acquisition Pixel (CAP) Concept ADC & storage Pixel Array: Column select – ganged row read High-speed Analog read-out Low power – only significant draw at readout edge Pixel Array of pixels time Vreset Δv typ α I leak Δv sig α Q signal Integration time t fr2 t fr1 reset M1 M2 M3 Bus Output Reset Collection Electrode Based on 3 transistor cell V_Q_integr

8. Samo Stanič for the Pixel Group - 2005/4/12 7 CAP1 – Basic operation confirmed TSMC 0.35  m Process Column Ctrl Logic 1.8 mm 132col x 48row ~6 K pixels CAP1: simple 3-transistor cell Pixel size: 22.5  m x 22.5  m CAPs sample tested: all detectors (>15) function. Source follower buffering of collected charge Restores potential to collection electrode Reset Vdd Collection Electrode Gnd M1 M2 M3 Row Bus Output Column Select

9. Samo Stanič for the Pixel Group - 2005/4/12 8 Correlated Double Sampling (CDS) ( - ) Frame 1 - Frame 2 = 8ms integration - Leakage current Correction ~fA leakage current (typ) ~18fA for hottest pixel shown Can readout/process @ 20Hz ~ 16% live time (CAP1!) Self-Triggering mode Hit candidate!

10. Samo Stanič for the Pixel Group - 2005/4/12 9 Hit resolution measurement L3 L4 L2 “ hit ” Residuals for 4GeV/c pions: < 11  m (in both planes) (in mm) 250  m Si 1mm plastic 1mm Alumina substrate 3.4 cm 3.6 cm4.6 cm x-plane z-plane

11. Samo Stanič for the Pixel Group - 2005/4/12 10 Radiation damage Belle CAP1 Prototype IEEE Trans. Nucl. Sc. 48, 1796- 1806,2001 Fully annealed

12. Samo Stanič for the Pixel Group - 2005/4/12 11 Peak pixel S/N prediction Extrapolation from upper edges of Eid et al.

13. Samo Stanič for the Pixel Group - 2005/4/12 12 CAP2 – Pipelined operation 8 deep mini-pipeline in each cell Pixel size 22.5  m x 22.5  m 3-transistor cell 132x48=6336 channels 50688 samples TSMC 0.35  m 132 x 48 10  s frame acquisition speed achieved!

14. Samo Stanič for the Pixel Group - 2005/4/12 13 CAP3 – Full scale pipelined prototype 36 transistors/pixel 5 metal layers 5 sets CDS pairs TSMC 0.25  m Process 5-deep double pipeline

15. Samo Stanič for the Pixel Group - 2005/4/12 14 CAP3 - sensor layout 928 x 128 pixels = 118,784 ~4.3M transistors ! 21 mm Active area 20.88 mm >93% active without active edge processing

16. Samo Stanič for the Pixel Group - 2005/4/12 15 CAP3 readout However: Some parts still missing CAP3 firmware still under development May be a few weeks delayed F3 board CAP3 F3 frontend readout board manufactured, laboratory testing is under way…

17. Samo Stanič for the Pixel Group - 2005/4/12 16 CAP3 based full detector concept e-e+ # of Detector / layer ~ 32 End view 128 x 928 pixels, 22.5  m 2 ~120 Kpixels / CAP3 0.25  m process CAP3 5-layer flex PIXRO1 chip Pixel Readout Board (PROBE) Side view Half ladder scheme Double layer, offset structure r~8mm Length: 2x21mm ~ 4cm 17 o 30 o r~8mm

18. Samo Stanič for the Pixel Group - 2005/4/12 17 “Fast” Belle SVD2 L1 upgrade option ~10%~4% ~2% Replace Layer 1 with CAP3 pixels Mechanically identical (drop in) CAP3 Flex

19. Samo Stanič for the Pixel Group - 2005/4/12 18 Belle SVD L1 upgradeCAP3 Flex 4 x 9 = 36 CAP3 / L1 ladder 6 ladders/L1 layer ~26M Channels total Scaling current SVD L1 * 4 background ~ few kBytes/event R=7mm configuration: 6.6M channels SVD L1 * 40 background ~ few 100kBytes/event With L3 track match: ~few 10kBytes/event

20. Samo Stanič for the Pixel Group - 2005/4/12 19 CAP3 Beam-test at KEK Possibility of CAP3 beam test in the end of June 2005 as the last experiment at the KEK PS before its permanent shut-down We are fighting against the tight schedule and looking forward to new results!

21. Samo Stanič for the Pixel Group - 2005/4/12 20 Summary: Critical R&D Milestones 1.Readout Speed 2.Radiation Hardness 3.Thin Detector 4.Full-sized detector 100kHz frame rate, 10kHz L2 accept >= 20MRad <= 50  m, double layer Span acceptance (reticle limit) 10  s frame acquisition OK (CAP2), CAP3 to test 100  s frame readout Leakage current OK (CAP2), q collection efficiency TBD 50  m mechanical dummies, CAP3 to be thinned (SNF) CAP3 fabricated – performance evaluation

22. Samo Stanič for the Pixel Group - 2005/4/12 21