ICASIPM– the International Conference on the Advancement of Silicon Photomultipliers Physics and Experimental Studies of SiPM Nonlinearity and Saturation Dr. Elena Popova 14th June 2018 National Research Nuclear University MEPhI, Schwetzingen, Germany Moscow, Russia 1 June 14 2018 E.Popova SiPM SiPM Nonlinearity...
Sometimes people use it for very high Silicon Photomultiplier – has been intensity light registration BUT developed for single photon Example : Calorimetry applications V. Andreev et al. / NIM A 540 (2005) 368–380 low intensity light 1000 Number of pixels fired dark 100 576 Light (single photon) 1024 4096 10 1 1 10 100 1000 10000 For short light pulses due to finite number of cells Number of photoelectrons charge signal (counted in number of fired cells) saturates N PDE ⋅ ⎡ − ⎤ photon − N N N 1 e = ⋅ ⎢ total ⎥ Binominal approach: firedcells total ⎢ ⎥ ⎣ ⎦ 2 E.Popova SiPM SiPM Nonlinearity... June 14 2018
Saturation SiPM signal A Monte-Carlo model of a SiPM coupled to a scintillating crystal 2012 JINST 7 P02009 (http://iopscience.iop.org/1748-0221/7/02/P02009) 3 E.Popova SiPM SiPM Nonlinearity... June 14 2018
4 E.Popova SiPM SiPM Nonlinearity... June 14 2018
5 E.Popova SiPM SiPM Nonlinearity... June 14 2018
Shaojun Lu If we are studying SiPM properties we have to think in the coordinates of • fired pixels (together with correlated pixels) – Y • Number of phe assuming ideal conditions with infinite number of pixels inside SiPM) – x 6 E.Popova SiPM SiPM Nonlinearity... June 14 2018
How to normalize the SiPM saturation curve? Amplifier and SPE spectra (low intensity light) K 1e < N phe >= − ln P (0) X i = Mean Mean= Mean(whole Y i = N < >= fired _ pixels distribution)-Ped_position К 1 e Z i = signal from the reference photodetector, units We need several Light intensity points provide us enough value of P(0) Calibration of reference Maybe last intensity 5 SiPM samples photodetctor in number of calibration point (too low P(0)) phe’s K type (1024 pixels) 20 300 1000 Only reference wafer #5 250 Fired pixels <Nphe> ≈ 5 15 photodetector 5 SiPMs 100 200 Number of fired pixels SiPM seed 10 calibration Events 150 10 100 5 1 50 0 0,1 0 20 40 60 80 100 0 0,1 1 10 100 1000 10000 Number of photoelectrons -0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 phe reference photodetector Z, units Area, nVs SiPM Crosstalk is visible Extraction number of seeds Fired pixels>phe 7 E.Popova SiPM SiPM Nonlinearity... June 14 2018
How to study the SiPM saturation? 1. Firstly we need to have a proper experimental setup Example of the setup 50 Ω 1. Light source, operated in stable mode (no changes in an electrical pulse) 2. Light intensity is changed by filters 3. Uniformly distributed light over the SiPM surface * (over surface with desired number of investigated pixels) 4. Reference stable linear photodetector (the best choice is PIN-diode) 5. Amplifier to obtain SPE spectra for low light intensity (bypassed for high intensity light) 6. Temperature and voltage must be stable and better controlled with needed accuracy 8 E.Popova SiPM SiPM Nonlinearity... June 14 2018
The proper experimental setup 1. Light source, operated in stable mode (no changing of electrical pulse) 2. Light intensity is changed by filters Due to changing of electrical pulse light pulse shape, wavelength and distribution of correlated photons might be changed too 3.Uniformly distributed light over the SiPM surface* (over surface with desired number of investigated pixels) Saturation (nonlinearity) depends on pixel load (number of photons/number pixels (think in fraction) 4. Reference stable linear photodetector -the best choice is PIN-diode (dynamic range of about 10 8 ) PMT is not the best choice for the reference detector. It has own nonlinearity, especially for pulse signals (parameters of the specific PMT should be checked)... 9 E.Popova SiPM SiPM Nonlinearity... June 14 2018
7.Then we need to understand what we want to study– amplitude (A) or charge (Q)? A and Q are different and have a different behavior 8. Important – we need to know exactly pulse shape corresponded to our task and the best situation when it can be reproduced exactly in the test setup 9. We need to know real operation conditions of SiPM (applied voltage, light distribution over the SiPM area, load and serial resistances of a connection scheem) 10 E.Popova SiPM SiPM Nonlinearity... June 14 2018
Amplitude (A) or Charge (Q)? Before saturation doesn’t matter. But if you have more then one phe/pixel: 11 E.Popova SiPM SiPM Nonlinearity... June 14 2018
Single stand alone cell. Moderate light (several photons/flash) intensities Focused laser light at the center of the cell, 40ps, 660nm Scope LeCroy WaveRunner 620Zi 2GHz 0 -2 Amplitude, mV -4 -6 -8 25,5 26,0 26,5 27,0 27,5 28,0 28,5 29,0 time, ns MEPHI cell Why so significant dispersion of signals amplitudes? It is exactly one fired cell (stand alone) Suggestion – Geiger discharge starts from several points inside of the cell 12 E.Popova SiPM SiPM Nonlinearity... June 14 2018
Amplitude (exp) 1 2 3 U =35V (U bd=33,35) N pe=0,069 N pe=1,74 200 Events N pe=3,62 0 0 2 4 6 8 10 12 14 Amplitude, mV Charge (exp) 300 U =35V (U bd =33,35) N pixel =0,069 200 N pixel =1,74 N pixel =3,62 Events 100 0 0 1 2 3 4 5 6 7 8 Area, pVs 13 E.Popova SiPM SiPM Nonlinearity... June 14 2018
But what is about cell charge for high intensity light in reality? 14 E.Popova SiPM SiPM Nonlinearity... June 14 2018
Pulse shape for different light Intensities. MEPHI data Hamamatsu S10362-11-100U No.50, Ubreakdown=68.4V, U=69.5V Fast part Normalized pulse shapes Slow part (recovering) 0,20 from 0,14 relative amplitude, a.u. 0.4 phe/cell to 0,12 0,15 30k phe/cell 0,10 Amplitude, V 0,10 0,08 0,06 0,05 0,04 0,02 0,00 0,00 10 15 20 25 30 10 15 20 time, ns time, ns 15 E.Popova SiPM SiPM Nonlinearity... June 14 2018
3.Important – we need to know exactly pulse shape corresponded to our task and the best way – it should be reproduced exactly in the experimental setup The same SiPM type Individual tile energy reconstruction using 5 SiPM samples calibration curve SiPM signal vs energy deposited: K type (1024 pixels) 1000 1000 wafer #5 ,pixels 5 SiPMs Fired pixels 100 1600 Number of fired pixels 250 100 1400 SiPM signal 1200 LED 200 Tile 10 1000 25 150 Counts Counts 800 Laser pulse 600 100 10 400 FWHM 40ps 1 50 200 0 0 200 400 600 800 1000 1200 1ch = 50 ps TDC channel 1 0,1 0,1 1 10 100 1000 10000 1 10 100 1000 10000 Number of phe Number of photoelectrons phe 1 10 100 Energy Deposited, MIP 1 SiPM Crosstalk is visible ~2000 pixels in saturation 1024 pixels in saturation Pulse shape depended – recovery during pulse duration!!! 16 E.Popova SiPM SiPM Nonlinearity... June 14 2018
17 E.Popova SiPM SiPM Nonlinearity... June 14 2018
CALICE MINICAL (preprototype of the tile HCAL) 100 SiPMs individually read out tile+WLS 1024 real pixels inside (agrees with saturation curve for 40ps light) N PDE ⋅ ⎡ − ⎤ photon − N N N 1 e ⎢ ⎥ = ⋅ total firedcells total ⎢ ⎥ ⎣ ⎦ Effective Ntotal is 1650+-150 18 E.Popova SiPM SiPM Nonlinearity... June 14 2018
SiPM Recovery Double light pulses method. 2 short pulses with high intensity to fire all SiPM cells Uniforme illumination over SiPM area y( Δ t)=A2/A1 Fixed intensity Δ t A1(Q1) A2(Q2) But one should be carefull – recovery might depends on light intensity (pixel load) - oversaturation 19 E.Popova SiPM SiPM Nonlinearity... June 14 2018
SiPM recovery time. Pulse shape analysis and double light pulses method for charge Q 140 C harge integration 25 ns C harge of s econd puls e, Q D C channels LIGHT MAX 120 Chi^2/DoF = 0.30513 R^2 = 0.99971 100 y0 153.60823 ± 0.18718 A -154.82526 ± 0.13935 tr 1.23323 ± 0.0034 80 y = A*exp(-x/tr) + y0 60 smaller LIGHT 40 Chi^2/DoF = 0.12033 R^2 = 0.99987 20 y0 138.12579 ± 0.06337 A -138.72352 ± 0.05169 tr 0.87725 ± 0.00121 0 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2 time between pulses, µ s Light MAX τ r=1233±4ns Smaller light (but still with SiPM saturation) τ r=877±2ns Both methods give the same results for recovery time vs light intensity Drawback – no light intensity monitor 20 E.Popova SiPM SiPM Nonlinearity... June 14 2018
We have repeated our measurements with 1x1 mm 2 MEPHI SiPM (pitch 100 µ m) under control of light intensity SiPM pulse for saturation conditions U is fixed Slow part (recovery) Fast part (geiger discharge) SiPM recovery time τ Amplitude, Charge and 1000 τ increase with light intensity Time constant τ , ns 750 500 Question – what is (are) the reason(s) for this? Group effect? 250 SiPM gain ~10 7 0 0 1000 2000 3000 4000 N phel / cell 21 E.Popova SiPM SiPM Nonlinearity... June 14 2018
Recommend
More recommend
