201 likes | 399 Views
Progress in Using Cold Avalanche Photodiodes as Single Photon Detectors J.Swain ,Y.Musienko*, S.Reucroft Northeastern University, Boston With thanks to A.Dorokhov, A.Glauser, C.Regenfus (Physik-Institut der Universitat Zurich) *on leave from INR (Moscow). Motivation.
E N D
Progress in Using Cold Avalanche Photodiodes as Single Photon Detectors J.Swain ,Y.Musienko*, S.Reucroft Northeastern University, Boston With thanks to A.Dorokhov, A.Glauser, C.Regenfus (Physik-Institut der Universitat Zurich) *on leave from INR (Moscow) NIST, 2003 J. Swain (Northeastern University, Boston )1
Motivation • New Hamamatsu APD’s developed for CMS and optimized for radiation hardness can operate at M~3000 (T=300K). Since we have them anyway… • Can they operate at high gains at low temperatures (~100K)? • Low temperature -> low dark current -> low noise count ? • What will be the efficiency for single photon counting, with APD operating in a linear mode? NIST, 2003 J. Swain (Northeastern University, Boston )2
Where they came from: CMS PbWO4 crystal NIST, 2003 J. Swain (Northeastern University, Boston )3
Hamamatsu APDs used in this study Summary of APD parameters APD`s designed for the CMS ECAL NIST, 2003 J. Swain (Northeastern University, Boston )4
Gain NIST, 2003 J. Swain (Northeastern University, Boston )5
Quantum Efficiency NIST, 2003 J. Swain (Northeastern University, Boston )6
Capacitance NIST, 2003 J. Swain (Northeastern University, Boston )7
Set-up • APD was inside evacuated metallic box inside a dewar • It was connected via ~60 cm cable to a preamplifier (Canberra-2003BT), followed by TENELEC TC-205A shaper (3ms shaping time) • APD was illuminated with the blue (470nm) LED through a gray filter • Currents were measured using a Keithley-487 source-meter • Amplitude spectra were measured with the LeCroy LT342L DSO • LeCroy 623B discriminator and 250 MHz scaler were used for signal counting NIST, 2003 J. Swain (Northeastern University, Boston )8
Gain at different temperatures NIST, 2003 J. Swain (Northeastern University, Boston )9
Dark Current (room temperature) What is the dependence of dark current on the temperature? NIST, 2003 J. Swain (Northeastern University, Boston )10
APD irradiated with neutrons (~1013 n/cm2) NIST, 2003 J. Swain (Northeastern University, Boston )11
Dark current vs. temperature Ibulk~T2*Exp(-0.47eV/kT) NIST, 2003 J. Swain (Northeastern University, Boston )12
Dark current vs. temperature Ibulk~T2*Exp(-0.47eV/kT) NIST, 2003 J. Swain (Northeastern University, Boston )13
Excess Noise Factor Does it depend on the temperature? Shape of the gain curve can give some indication. NIST, 2003 J. Swain (Northeastern University, Boston )14
High capacitance APD Full depletion at 80V NIST, 2003 J. Swain (Northeastern University, Boston )15
Voltage coefficient of the gain Shape of the gain curve does not depend on the temperature: ionization coefficients for holes and electrons depend on the temperature, but their ratio (k-factor) remains constant! NIST, 2003 J. Swain (Northeastern University, Boston )16
Light and noise counting rate Electronic noise was 430 el. rms at t=3 ms NIST, 2003 J. Swain (Northeastern University, Boston )17
Single electron spectrum Theory: R.J.McIntyre, IEEE Trans. Electron Devices, vol. ED-19, p.703, June 1972 NIST, 2003 J. Swain (Northeastern University, Boston )18
Photoelectron detection efficiency Gain of the APD was measured at high LED current, then current was significantly reduced to achieve low photon rate (~26 kHz). At M=8000 Iill=34 pA (~4.3 fA primary photocurrent) NIST, 2003 J. Swain (Northeastern University, Boston )19
Summary • At T~100K new Hamamatsu APD’s operate at M~104, • k-factor does not depend on temperature (110K<T<295K) • 25% photoelectron detection efficiency was measured with 1150 el. electronics threshold, APD operated in linear mode (M~8000) • This correspond to ~20% single photon counting efficiency for 470nm light • Noise count <0.1 Hz was measured at 2500 el. Threshold (T=108 K), while efficiency of photoelectron counting was ~20% • Results are in agreement with McIntyre calculations • Reducing electronic noise and k-factor, single photon counting efficiency can be significantly improved, while keeping noise count at very low level NIST, 2003 J. Swain (Northeastern University, Boston )20