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Tile production and SiPM test facilities at ITEP

Tile production and SiPM test facilities at ITEP. Test of photodetectors – set-up, procedure and results Scintillator detector manufacturing Test of assembled tiles - procedure and results.

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Tile production and SiPM test facilities at ITEP

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  1. Tile production and SiPM test facilities at ITEP • Test of photodetectors – set-up, procedure and results • Scintillator detector manufacturing • Test of assembled tiles - procedure and results CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  2. Test of photodetectors • Aim: - find operating voltage to have 15 pixels per MIP response in 3x3 cm2 tile • - measure response of SiPM in light range 0.1-200 MIP • Test bench • 15 detectors are tested simultaneously. They are illuminated with monitored light produced by UV LED and re-emitted by bundle of WLS fibers • The test set-up includes: • CAMAC random and LED trigger generator with LED driver • 16 channel computer driven power supply • computer read-out digital voltmeter • PMT for LED light monitoring CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  3. CAMAC random and LED trigger generator with LED driver - LED flash amplitude is set by 12-bit DAC - frequency range up to 2 kHz - pulse duration is set by external cable (minimal – 20 ns) SiPM LED pulse seen by SiPM and PMT PMT CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  4. 16 channel computer driven power supply to feed SiPM’s - output voltage range – 0-80 V - stability < 10 mV - maximal output current – 100μA CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  5. computer read-out digital voltmeter • to monitor • - SiPM bias voltage • - SiPM current • - temperature of SiPM’s, LED and PMT during test • - measurement accuracy • voltage – 5 mV • current – 5 nA • temperature – 0.2O CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  6. Test procedure 1.Tune HV in order to have SiPM response equal to 15 pixels/MIP in 3x3 cm2 tiles. The response of a SiPM is measured at various bias voltages. Fit of LED response spectrum results in gain, cross talk and number of photoelectrons. For each value of bias voltages the number of pixels per MIP is calculated and operating bias voltage is chosen from the fit of these points by a power function pix/MIP = A * ( V - Vthr )B At chosen bias voltage the saturation curve of SiPM’s is measured in light range ~0.3-200 MIP CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  7. At chosen bias voltage the following SiPM parameters are controlled: • gain • cross talk • noise • noise at 1/2 MIP threshold • width of single photoelectron peak • response to light in the range 0.1-200 MIP • SiPM average current and its stability • The set-up operation is based at measurements of tiles with Sr90b-source. • First for ~10 SiPM’s bias voltage was tuned to have response to b-particles in 3x3 cm2 tile 15 pixels. • Then these SiPM’s were used in test bench to calibrate LED light. • The amount of LED light is monitored by PMT during measurements and its stability implies the accuracy of SiPM calibration. • So, the special care was taken to PMT gain stability which is deduced from the single photoelectron peak position in PMT spectrum. If the position of single photoelectron peak differs from the reference one then the correction of PMT response is done. CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  8. SiPM test results all detectors CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  9. SiPM selection Ped RMS < 50 ADC channels Gain > 4*105 or 1 pixel > 26 ADC ch., corresponds to 1 pC/MIP Cross talk < 0.35 At HV adjusted 14.25 < Npix/MIP < 15.75 Noise frequency at zero threshold < 2.5 MHz - at higher frequency the fit procedure of LED spectrum fails often Noise frequency at ½ MIP threshold < 500 Hz – this corresponds to 1 extra hit in 8000 channels per event Mean value of SiPM current < 2 mA RMS of SiPM current during test < 20 nA Number of pixels at maximal light (~200 MIP) > 900 CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  10. Summary of SiPM selection for all SiPMs tested CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  11. Most of SiPM’s have been rejected due to high noise Spectra below show the difference between good and typical rejected SiPM’s The left one has noise frequency – 1.5MHz The right has noise frequency 2.8 MHz Note the difference in pe peaks separation and in the slopes of the tail of random trigger spectrum. CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  12. We plotted values of the slope of the random trigger spectrum vs cross talk and found that for each Si wafer points are grouping but for wafer # 481-4-15 (blue points) SiPMs had the smallest value of the slope. This results in higher noise at ½ MIP level. Most of such SiPMs have been rejected.

  13. Software development Developed software allows to perform test of photodetectors as well as make long term measurement of SiPM current, monitor the behavior and calibrate of all set-up components, namely LED, PMT, power supply, digital voltmeter. After SiPM test all results are saved in data base and may be analyzed. CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  14. Analysis of SiPM test data Comparison of data measured at bias voltages closed to the operational one gives average values of response, efficiency, gain, noise, cross talk, number pixels per MIP variation at 0.1 V variation of bias voltage. N pix/MIP 3.9% gain 2.7% response 6.7% efficiency 2.3% noise 4.2% cross talk 4.8% CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  15. Estimate of statistical errors Multiple measurement of the same SiPMs in the same test bench channels allows to estimate statistical errors in determination of parameters which are subject to selection cuts: Operational bias voltage ~0.1% Noise ~2% Cross talk ~3% Number of pixels per MIP ~1.5% Noise at ½ MIP level ~20% SiPM current ~2.5% CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  16. Estimate of measurement accuracy We have measured the reproducibility of test results when a SiPM is placed in various channels of the test bench. We have taken 15 SiPMs and checked them each time in different channel. The distribution of operatinal bias voltages with respect to one reference channel is shown. The value of RMS = 53 mV one can transform to RMS of number of pixel per MIP -> 2%. CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  17. 10k 1k +HV 0.1 1.0 1k Long term stability We have now the set-up to reject SiPM’s after long term test (240 channels). Individual bias voltage setting for each channel, outputs for current and pulse shape monitor 100 k CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  18. Tile production Tile size 3x3 cm2 6x6 cm2 12x12 cm2 To be produced 3500 4000 1000 Mold 3500 4000 1000 Edge mated 3500 4000 1000 Groove milled 3500 4000 500 Shipped to DESY 600 600 120 CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  19. Molded and edge treated tiles are milled at ITEP. Grooves for WLS fiber, mirror and SiPM placing are produced by digital Desktop Engraver ROLAND EGX-300 Accuracy – 10 μm Use mills of 0.04’’ which fit well 1mm fiber diameter CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  20. WLS fiber production Tile size 3x3 cm2 6x6 cm2 12x12 cm2 To be produced 3500 4000 1000 Cut 3500 4000 1000 Installed to tiles 3500 4000 500 Shipped to DESY 600 600 120 CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  21. A special tool was designed and constructed to make fiber cut Cut was made by 2 step milling – first with disk mill and finish with diamond cutter Cutting of thermally bent fibers for 6x6 cm2 tiles was done with use of a special jig. CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  22. Tile test CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  23. Tile test • Up tp 16 tiles are loaded in the same time into box • Computer driven carriage brings the β-source and the trigger counter to a tested tile. Source position is controlled by the computer readout sensor • SiPM bias voltage is set according to SiPM test and temperature measurement • Measurement of MIP response with help of triggered b-particles • LED spectrum gives information about SiPM gain • So, one may deduce the number of pixels in MIP peak • Conditions and results of tile test are saved to data base for further use and analysis CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  24. Light yield for tiles for cassettes 1 - 6 30x30 mm2 60x60 mm2 120x120 mm2 We had ~8% overestimated value of light yield due to wrong determination of SiPM gain in the measurement of the 1st cassette CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

  25. Production schedule • Production and assembly of tile / fiber is almost finished. • SiPM test bench is capable to check more than 500 SiPMs per week. • Test with β-source may keep this rate – measurement with source takes about 4’ per tile. In case of delay we may use the old test set-up too. • Stand for long term stability is designed to test 240 SiPMs at once – the full procedure will take 2 days: Load and unload detectors, set voltages, record initial and final status - 1 day Expose of SiPMs under bias voltage - 1 day • Boxes for tested tiles transport to DESY have been manufactured. • So every part of test chain is capable to maintain the rate 2 cassettes per week CALICE meeting, DESY, October 12-14, 2005 E.Tarkovsky ITEP,Moscow

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