International Workshop on New Photo-Detectors (PD07) @ Kobe University Geiger-mode APD as a RICH Photodetector Toru Iijima Nagoya University June 28, 2007
Collaborators Toru Iijima, PD07 @ Kobe Koji Hara, Toru Iijima, Yuri Mazuka, Mio Yamaoka Department of Physics, Nagoya University Rok Dolenec, Samo Korpar, Peter Krizan, Rok Petotnik, Andrej Petelin Jozef Stefan Institute, Ljubljana Special Thanks to; Belle-ACC group, KEKDTP RD-photon group Hamamatsu Photonics, Yuri Kudenko
Talk Outline • RICH w/ Aerogel radiators • Why Geiger-mode APD for RICH ? • Characterization of G-APD • Light collection system • Expected performance • Summary/Prospect Can we use Geiger-mode APD (SiPM / MPPC) as a RICH photosensor ? Toru Iijima, PD07 @ Kobe
Proximity Focusing Aerogel RICH • Aerogel radiator (n~1.05, ~2cm) + photodetector (Dx ~ 5mm) • >4s K/p for 0.7 < p < 4.5 GeV/c • Proximity focusing geometry • No mirror complex. • Suitable for collider and space experiments. • Rayleigh scattering dominates in aerogel. Demand for positioning of a single photon in the visible wave length region. Design values for Belle upgrade Toru Iijima, PD07 @ Kobe
Belle PID Upgrade Option • Barrel TOP (Time-Of-Propagation) Counter • Endcap Proximity Focusing Aerogel-RICH Barrel PID TOP Endcap-PID Aerogel-RICH Talk by K.Inami • Photodetector options • HAPD (baseline) • Poster by I.Adachi • MCP-PMT • Talk by S.Korpar • G-APD Toru Iijima, PD07 @ Kobe
RICH with Multiple Radiators NIM A548(2005)383 • Demonstration of principle • 4×4 array of H8500 (85% effective area) sc=22.1mradNpe=10.7 Conventional 4cm thick aerogel n=1.047 sc=14.4mradNpe=9.6 Multiple Radiators 2 layers of 2cm thick n1=1.047, n2=1.057 p/K separation with focusing configuration ~ 4.8s @4GeV/c Toru Iijima, PD07 @ Kobe
RICH with Precision Timing Fast photon detector enables Aerogal RICH to have TOF info. photosensor @ 4GeV/c In case of Belle… Cherenkov lights from aerogel aerogel DTring(p/K) ~37ps p/K 4GeV DTwindow(p/K) ~47ps IP 1.8m 0.2m Beam test result w/ Burle 85011-501 p/K separation w/ TOF Positive ID of K/p below thereshold. swindow = 34 ps w/ glass hit Toru Iijima, PD07 @ Kobe
Why SiPM/MPPC for RICH ? • Cons. • Noize • Size • Rad. hardness ? • Pros. • High PDE • B field immunity Toru Iijima, PD07 @ Kobe Comparison to other photodetctors
Possibility of G-APD for RICH To improve S/N … • Increase the number of signal hits/sensor by using light collectors (with optimization of pad size to the ring thickness). • Reduce the noise by a narrow time window (<10ns). Light collector serves as a light emitter for TOF measurement. SiPM / MPPC + Optics (Light-guide. Lens…) Light collector □3~5mm (IN) □1-2mm(OUT) Cherenkov Photons (17deg max. for n=1.05) Aerogel-RICH n1 n2 G-APD □1~3mm
G-APD Characterization New Old Measured Items • Photon-counting performance • Timing property • Use of timing for random noise rejection • + also for TOF measurement • Photo-Detection Efficiency • As a function of l • Noise Performance 20mm We report basic performance using 1 x 1 mm2 samples Measured samples MPPC from HPK MRS-APD (CPTA) 1710 series 1.1mm2 556 pixels. + SiPM (MePhI/PULSAR) 1710 series 1.1mm2 556 pixels.
Performance: Photon-counting H100-old, Vbias=71.5V, noise～1.0MHz meanped: 98.9mean1pe: 137.1sped: 3.0 H100-old. Pulse laser HPK PLP-02 (410nm) ALS PiL063 (636nm) • Excellent resolution to separate 0 and 1 photon (and more). • Gain = 1.8 x 106 at Vbias=71.5V • S/N = Dmean/s = 12
Light dielding box Quantum efficiency Geometrical efficiency Geiger efficiency xy-stage Performance: PDE filter A Ref. PD A Geiger mode APD pin holef200mm Photo spectrometer 45% at peak (460nm) P.D.E. (%) • Higher efficiency at peak and long wave length, compared to conventional PMT’s. • Our result is consistent with HPK. • Need confirmation by photo-counting to disentangle the effects of cross talks and after-pulses. Photo Detection Efficiency
Noise (kHz) Gain (x 103) Performance: Gain vs Noise 100 pixel 400 pixel 2007/1/16 Recent HPK products have much lower noise rate < 1/3 at the same gain.
Performance: Time Resolution Sample ＭＰＰＣ Bias -71.5V Threshold 0.5pe Only Single photon data Measured w/ pulse laser 636 / 410nm MPPC (HPK) 636nm 410nm s~110ps s~103ps Time walk corrected. MRS-APD s~140ps s~70ps Depend on internal structure ? Can be used for TOF measurement as well.
Time resolution(MRS-APD) Single photon, threshold ~0.4pe l=635nm l= 405nm long tail(~4ns) Short tail(~0.5ns) s~69ps s~142ps 43.0 39.5 40.0 40.5 41.0 41.5 41.5 42.0 42.5 43.5 TDC(ns) TDC(ns) Toru Iijima, PD07 @ Kobe
Setup for Surface Scan @ Jozef Stefan Inst. Toru Iijima, PD07 @ Kobe
SiPM surface sensitivity Size: ~1mm Scanned with laser, resolution ~5 mm Single photon response SiPM (MePHY/Pulsar) MRS APD by CPTA (Moscow) Toru Iijima, PD07 @ Kobe
Micro Structure SiPM (MePHY/Pulsar) MRS APD by CPTA (Moscow) Toru Iijima, PD07 @ Kobe
Hamamatsu MPPCs 400 pixels 100 pixels 1mm
Light Guide • Possible design • Trapezoid • Winston Cone • Lens • … Ex.) Trapezoid, incident at 0.3rad (max. in case of Super-B) □5mm □1mm □5mm □2mm CE=95% CE=37% Toru Iijima, PD07 @ Kobe
Simulation conditions • Incident angle = 0.3rad • Wave length = 400nm • No internal absorption • n=1.47 acryl ic material Light Guide • Trapezoid • Lens (half-sphere) +Trapezoid length 5mm 5mm 2mm length 2mm L>12mm to obtain max. eff. L>9mm to obtain max. eff.
Light Guide (2) Toru Iijima, PD07 @ Kobe
2mm 5mm Expected RICH Performance Arbitrary The simulation is adjusted to reproduce beam test results with multi-anode PMT. Should be corrected for cross talk / after-pulse contribution (because PDE based DC current measurement is used here). A photosensor based on Light-guide + Geiger-mode APD can give x 4 Npe (number of detected photons).
Effect of Noise Kaon ID efficiency at 1% pion mis-ID probability 0.8% 0.8% 1.6% 1.6% 3.2% 3.2% Pad size = 4mm2 Momentum = 4 GeV/c Pad size (mm2) Momentum (GeV/c) Noise rate (HPK-100) = 200KHz/mm2 @ 106 gain. 0.8MHz for 4mm2 pad and 10ns time window Random background embeded in a simulation. Assume Npe = 20 / ring (conservatively)
Summary • Geiger-mode APD is very attractive device as a photosensor for a RICH with aerogel radiator. • High PDE Significant increase in Npe (x 4 possible). • Good time resolution (s~100ps /p.e.) RICH w/ TOF • Free from magnetic field Large advantage ! • Noise rate has been reduced significantly and in a tolerable region (<1MHz/pad) for recent products from HPK . Very encouraging ! • Light colletction based on tapered lightguide (+lens) will be useful to increase the detection area, and hence improve S/N. • Devices with larger size (□3~5mm) are highly welcome. We are starting to measure □3mm sample from HPK. Toru Iijima, PD07 @ Kobe
Backup Toru Iijima, PD07 @ Kobe
g e- e- e- e- e- e- h h h h h h n+ p+ p- g Light absorption in silicon Electric field in SiPM Light absorption length a = f (l) This is plot of SiPM, not MRS-APDreference: ICFA Instrum.Bull.23:28-41,2001 Red(l=635nm): absorbed in Geiger region→make prompt signals absorbed in drift region→make slow signals, long tail Blue(l=405nm) : absorbed before reach to Geiger region→TDC has short tail, worse resolution in Geiger region (mm) Toru Iijima, PD07 @ Kobe
Temperature Dep. of Noise • ０℃では室温の20～30％になった ＭＲＳ－ＡＰＤ ＭＰＰＣ ～300ｋＨｚ@ 0℃ ～200ｋＨｚ @ 0℃ MRS-APD MPPC Geiger mode APDが並んでいる 青リング チェレンコフリング 赤 チェレンコフ光による信号 緑 ノイズによる信号 （deg.）
Performance: Gain vs Noise (MRS-APD) Noise (kHz) Gain (x 103)
Plan Photo from the talk by Sato-san (HPK) at the photosensor WS (Dec.7-8,2006). • Further measurements of samples • HPK starts to provide 3x3mm2 samples. • Better understanding of critical properties. • Feedback to producers. • Light-guide design • Measurements with a test sample. • Method to produce the assembly. • How to make the light-guide (LG) array. • Optical connection between LG and SiPM/MPPC. • Readout Electronics