hybrides à pixels et à leurs applications

Transcription

1 FACULTÉ DES SCIENCES Section de physique Département de physique nucléaire et corpusculaire Séminaire du mercredi 5 novembre 2003 Introduction à la technologie des photodétecteurs hybrides à pixels et à leurs applications Thierry Gys CERN, Genève,, Suisse 1

2 Outline of the talk The hybrid photon detector Basic principles Comparison with PMTs Description of various types The pixel-hpd development framework The LHCb detector, the RICH 2 counter, and overall LHCb-RICH system requirements LHCb pixel-hpd description and the various prototype generations Custom anode developments Pixel chip performance New high T bump-bonding developments Quantum efficiency aspects Test beam measurements Gamma imaging examples HPMT with YAP:Ce window ISPA tube with YAP:Ce window Conclusions T. Gys DPNC seminar Uni Genève November

3 Basic principle of the hybrid photon detector Combination of state-of of-the-art solid-state state technology and image intensifier technology Optical input window Photon Typical performance: Focusing electrodes Photocathode Photoelectron DV G = σ G = V Vth ~ V=20kV 3.6 ev F G σ el ~ VACUUM with V th ~ 1kV (for 0.5mm dead layer) F ~ 0.12 (Fano factor) Silicon sensor n+ n p+ dominated by electronics noise T. Gys DPNC seminar Uni Genève November

4 Principle of the HPD (cont d) Typical photoelectron pulse height distribution: 30% QE HV=20 kv VA2 external readout (1.2 ms peaking time) (DEP 61-pixel HPD, cross-focussed) 200nm 800nm Typical QE curve: multialkali S20, quartz window (DEP 61-pixel HPD, proximity-focussed) T. Gys DPNC seminar Uni Genève November

5 Energy release of a 20keV photoelectron in Si XY profile +5mm 150nm n+ layer thickness Z profile 5mm -5mm FLUKA simulations performed by B. Mikulec T. Gys DPNC seminar Uni Genève November

6 Energy release of a 20keV p.e. in Si (cont d) Total released energy profile Back-scattering energy profile M. Alemi et al. NIM A 449 (2000) 48 T. Gys DPNC seminar Uni Genève November

7 Back-scattering and charge sharing effects Back-scattering n+ n p+ 18% probability <E> E 0 /2 Reduced effect if low cut Charge sharing n+ n Photoelectron Photoelectron p+ 7µm RMS lateral spread (300 µm-thickness, 90 V bias) Not significant if E cut <E 0 /2 T. Gys DPNC seminar Uni Genève November

8 Comparison with Hamamatsu multi-anode PMT Compact dynode construction (fine machining technique called metal channel dynode ) Photo-cathode Anode Focussing grid Dynode Typical performance: G = g 1 g 2.. g N ~ 3 10 V=800V σ G = with ENF = (ENF -1) G σ 1+ 1 g + g el ~ g g1 g2... gn dominated by 1st dynode(s) gain fluctuations T. Gys DPNC seminar Uni Genève November

9 Comparison with multi-anode PMT (cont d) Typical photoelectron pulse height distribution: HV=900 V APVm readout (50 ns peaking time) (Hamamatsu R M64) Typical QE curve: bialkali pk, UV-glass window (Hamamatsu R M64) LHCb-RICH group T. Gys DPNC seminar Uni Genève November

10 HPMT design Characteristics: HV=10-15 kv Cross-focussing e-optics pk-anode gap ~50 mm mm input active single-diode anode external readout T. Gys DPNC seminar Uni Genève November

11 Proximity-focussed design (commercially available at DEP) E. Albrecht et al. NIM A 411 (1998) 249 Photon Specific features: pk Photo-electron Compact structure Immunity to large B // fields 1:1 mapping geometry + - n+ + - n p+ Characteristics: HV=12 kv pk-anode gap ~12mm 18 mm active (35 mm total ) 61-pixel anode external readout Optical cross-talk reduced by AR coating on Si e - back-scattering at Si surface (max. range=2d) (18 % with <E>=E/2) Charge sharing within bulk Si important for detection efficiency d + - n+ + - n n+ n Photo-electron p+ pk Photo-electron + - p+ pk T. Gys DPNC seminar Uni Genève November

12 Cross-focussed design (LHCb prototype from DEP) M. Alemi et al. IEEE TNS Vol. 46, No. 6 (Dec. 1999) 1901 E. Albrecht et al. NIM A 442 (2000) 164 Characteristics: HV=20 kv pk-anode gap ~110 mm 75 mm active (83 mm total ) 61-pixel anode external readout Specific features: tetrode e - optics 50 µm PSF 80 % area ratio 5:1 mapping geometry T. Gys DPNC seminar Uni Genève November LHCb-RICH Group

13 The LHCb detector (top view) LHCb is a single-arm spectrometer with a forward angular coverage from 10 to 300 mrad, dedicated to precision studies of CP asymmetries and of rare decays in the B-meson system Particle identification over the momentum range GeV/c will be achieved by two Ring Imaging Cherenkov counters T. Gys DPNC seminar Uni Genève November

14 Schematic view Photo detectors The RICH 2 counter Mechanical design studies Flat mirror Spherical mirror rich2_schematic.gif RICH2 EDR LHCb EDR March 2002 T. Gys DPNC seminar Uni Genève November

15 Overall LHCb-RICH system requirements Photon detection ~2.9 m 2 total surface Granularity: mm 2 Active area coverage 70 % (~ channels) Single-photon sensitivity (λ = nm) Environment Magnetic stray field: Radiation dose: 300 gauss (RICH1) 100 gauss (RICH2) 3 krad/year Read-out Maximum occupancy: 10 % BCO identification (τ p 25 ns) High L0-trigger rate (1 MHz) Photo-detector options Pixel-HPDs: cross-focussing geometry binary pixel readout Multi-anode PMTs: metal channel dynodes analogue readout Final choice! (October 2003) T. Gys DPNC seminar Uni Genève November

16 LHCb pixel-hpd description Schematic view super-pixel sensor array (500µm 500µm each) Encapsulated binary electronics readout chip 16mm 16mm active area 40MHz readout clock ~800ns readout time complying with LHCb L0 trigger rate (1MHz) ~gys/lhcb/pixelhpds.htm T. Gys NIM A 465 (2001) 240 T. Gys DPNC seminar Uni Genève November

17 Binary front end electronics (baseline specifications) Pixel chip design and bump-bonding are organized as joint developments between ALICE and LHCb Full readout chip Super-pixel 500µm 500µm area 8 sub-pixels ORed together reduced occupancy seen by analogue FE and lower noise tight requirements on bump-bonding Digital FE electronics: 16 delay lines (4µs) 16-deep FIFO de-randomizing buffer Sub-pixel 62.5µm 500µm area Analogue FE electronics: Differential amplifier (250 e noise) Shaper (25 ns peaking time) Discriminator (2000 e aver.) See contribution of K. Wyllie to the Pixel 2002 workshop T. Gys DPNC seminar Uni Genève November

18 Expected photoelectron detection efficiency Pedestal Cut Signal Pedestal: 250 e RMS noise Cut: 2000 e aver., 30 e RMS spread Signal: 5000 full energy + 18 % back-scattering + charge sharing 90 % photoelectron detection efficiency T. Gys DPNC seminar Uni Genève November

19 Full-scale pixel-hpd prototypes (1) Manufactured by DEP B.V. (The Netherlands) First generation (completed in 1999) Phosphor screen anode CCD readout check of active area, electron-optics, photo-cathode uniformity, magnetic field sensitivity and shielding options. 61-pixel HPD prototype M. Alemi et al., IEEE Trans. Nucl. Sc. 46,6 (1999) Second generation (completed in 1999) Commercial 61-pixel anode External analogue VA2 readout LHCb/PixelHPDs.htm check of response to Cherenkov light, installation of a cluster in the RICH prototype. T. Gys DPNC seminar Uni Genève November

20 Full-scale pixel-hpd prototypes (2) Laboratory measurements Pulsed LED spectrum Signal-to-noise ratio 20kV with external analogue VA2 readout (τ p =1.2 µs) Beam tests in LHCb RICH 1 prototype E. Albrecht et al. NIM A 442 (2000) 164 Tube figure of merit: N cm -1 HPD cluster T. Gys DPNC seminar Uni Genève November

21 From a commercial to a custom HPD anode Commercial anode: 61 hexagonal pixels 2mm flat-to-flat 500mm In bump-bonds External analogue readout (τ p = 1.2µs) ~65 feed-throughs Custom anode: Custom anode: 8192 sub-pixels 62.5mm 500mm in size 30mm Sn-Pb bumpbonds Encapsulated binary readout (τ p = 25ns) ~250 feed-throughs T. Gys DPNC seminar Uni Genève November

22 Custom anode requirements HPD manufacturing Tube body assembly: mechanical compatibility and high T (850 C) brazing Vacuum tightness Low outgassing Bake-out cycle: 300 C (ramping up and down times 6h) Multi-alkali photocathode processing: required residual vacuum of 10-9 T Pixel chip packaging Die cavity size vs tube body size Chip I/O and electrical performance Power dissipation (1.8W for LHCBPIX1) Compatibility with LHCb integration scheme Overall carrier size Carrier pinout and ZIF socket T. Gys DPNC seminar Uni Genève November

23 Semi-custom ceramic carrier for ALICE1LHCB chip Manufactured by Kyocera (Japan) Design based on existing carrier to minimize development costs Semi-custom Pin Grid Array carrier for the ALICE1- LHCb chip ALICE1LHCb chip within carrier cavity ~100 finger bond pads (out of 360) used Resistive losses on power lines Detector offset Long wire bonds T. Gys DPNC seminar Uni Genève November

24 Full-scale pixel-hpd prototype (3) Third generation (completed in 2002) ALICE1LHCB single assembly anode on semi-custom ceramic carrier PGA ceramic carrier Bump-bonded assembly with ALICE1LHCB chip Kovar ring ALICE DAQ (software+hardware) readout To ALICE DAQ check of response to pulsed LED light. Pixel-HPD Pulsed LED T. Gys DPNC seminar Uni Genève November

25 Full-scale pixel-hpd prototype (4) Firing pixels per LED pulse Back-pulse spectrum Poisson fit Photoelectron detection efficiency 88% Differential number of firing pixels as a function of HPD HV (detector bias 80V) 6.20kV m = 6.19kV (1718e-) s = 0.91kV (250e-) M. Campbell et al. NIM A 504 (2003) 286 These distributions reflect the comparator threshold distribution of the ALICE1LHCB chip (without and with 2 different threshold adjust procedures) 4.9kV T. Gys DPNC seminar Uni Genève November

26 LHCBPIX1 chip performance 10-layer carrier design optimized for LHCBPIX1 chip operation K. Wyllie et al. Submitted to NIMA Bare chip performance in carrier: Threshold: ~1000e- Noise: ~130e- T. Gys DPNC seminar Uni Genève November

27 Full-custom carrier and packaging aspects Carrier manufactured by Kyocera (Japan) Full-custom design based on Pentium I footprint to minimize integration costs Packaging performed in industry by HCM (France) Silver-glass die attach: minimize outgassing and withstand bake-out cycle; cured in belt furnace for ~2h with peak T 410 C for 10. LHCBPIX1 chip within carrier cavity 242 finger bond pads used (+4 for pixel detector), additional pins used for heat dissipation T. Gys DPNC seminar Uni Genève November

28 Packaging aspects Gold ball wire-bonding LHCBPIX1 chip packaging detail Fully automated W/B compatible with HDCM mechanical tolerances Detail of carrier W/B on lower deck Detail of chip W/B Double row of pads: Upper one for probing Lower one for W/B T. Gys DPNC seminar Uni Genève November 2003 Detail of carrier W/B on upper deck 28

29 New high T bump-bonding process Standard eutectic solder: 37%Pb-63%Sn, melting point 183 C. New high T bump-bond from VTT (Finland) High temperature solder: 90%Pb-10%Sn, melting point 300 C Compatible with HPD heat cycles T. Gys DPNC seminar Uni Genève November

30 Quantum efficiencies of full-scale pixel-hpd prototypes Commercial anodes Custom anodes Standard pk (thick S20): QE de 0.70 ev Can be tuned for enhanced UV response (thin S20): QE de 0.77 ev Quartz window cut-off ~optimized for LHCb Photon energy threshold 1.5eV Dark counts few khz/cm 2 T. Gys DPNC seminar Uni Genève November

31 Test beam measurements: air radiator PS T9 test beam area UK RICH 1 prototype 40MHz HPD prototype T. Gys DPNC seminar Uni Genève November

32 Test beam measurements: air radiator (cont d) M. Moritz et al. Proceedings of NSS 2003 T. Gys DPNC seminar Uni Genève November

33 Test beam measurements: aerogel radiator Pixel-HPD cluster Expected q c = 234mrad HPDs α Aerogel mirror Aerogel n»1.03 t=4cm Spherical mirror R=94.9cm T. Gys DPNC seminar Uni Genève November

34 Test beam measurements with aerogel (cont d) +10 GeV p/p Angular resolution ~4mrad -10 GeV p T. Gys DPNC seminar Uni Genève November

35 g detection with a YAP:Ce Ce-window HPMT-tube YAP:Ce window HPMT prototype: Light yield linearity: DEP multialkali S20 pk cross-focussed, single diode and external readout (τ s = 100ns) Quantum Efficiency Q.E YAP-window Q.E Quartz-window YAP:Ce window C. D Ambrosio et al. NIMA 431 (1999) 455. Number of photoelectrons total absorption peaks of various γ sources y = x Am g R 2 = Cd g 57 Co g 109 Cd X 203 Hg g 203 Hg K Wavelength [nm] Hg L Energy [kev] T. Gys DPNC seminar Uni Genève November

36 g imaging with a YAP:Ce Ce-window ISPA-tube YAP:Ce window ISPA prototype: DEP multialkali S20 pk proximity-focussed internal binary readout (τ s = 100ns) YAP:Ce window Height [A.U.] Intensity profile mean1 = 2.80 mm sigma1 = mm mean2 = 3.70 mm sigma2 = mm c.o.g. coordinate projection x [mm] 241 Am image through a 2-hole Pb collimator (1mm dist., 0.35mm ) F. Cindolo et al. IEEE TNS Vol. 50, No. 1, (Feb. 2003) 126. Counts Compton edge (11 kev) 60 kev FWHM ~ 26.5% ~105 p.e Number of photoelectrons 241 Am spectrum T. Gys DPNC seminar Uni Genève November

37 Conclusions Hybrid photon detectors feature: excellent photon counting and location capabilities design flexibility for what regards: input window type (quartz, fiber-optics, scintillating crystal) electron optics (proximity or cross-focussing) anode (single diode or multi-pixel) electronics readout (external or encapsulated) Their future is bright! Acknowledgements Many thanks to the DPNC for the invitation, and to Mariane Brinet for the seminar organization T. Gys DPNC seminar Uni Genève November