QRLed Driver in Magnetic Field Jaroslav Zalesak Institute
- Slides: 15
QRLed Driver in Magnetic Field Jaroslav Zalesak Institute of Physics of the ASCR, Prague Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 1
Calibration Option 2: LED driver • Non-linearity correction, MIP calibration, Correction temperature variations • Two appr. : electrical or optical signal distribution - One LED / one tile or central driver plus fibres UV LEDs – short light pulses Notched fibers Each illuminates 12 tiles HBU CALIB module Option I QRLD board (ASCR Prague): „Quasi Resonant LED Driver Board“, 6 LEDs / 1 PCB Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 2
QR-LED driver • • Option with optical fiber distribution Electronics: multi-channel prototype complete Optical system: uniformity again competitive Multichannel LED driver • 1 PCB with the communication module µC, power regulator, 6 channels of QRLed driver • Communication module to PC via CAN bus or I 2 C • Controlling the amplitude and monitoring temperature and voltages • LED pulse width ~ 5 ns fixed, tunable amplitude up to 50 -100 MIPs is controlled by the V-calib signal • 2 LEDs can be monitored by a PIN photodiode +12 V Power regulator QRLED 1 F I B R E S T-calib µC AT 91 SA M 7 X 256 V-calib QRLED 6 Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field LED 6 3
Magnetic Field Test Setup • week ago tests in mag. field • one week period at solenoid • DESY site up to 4 T available • QRL PCB fixed to movable rod • different positions to measure • 3 LEDs / channels → • 3 optical fibers outside meas. area, LV supply and CANbus wires from r/o area Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 4
Data Readout • 3 r/o Photo detector channels: § 2 APDs @ low-gain § 1 PIN diode + amplifiers • 1 Temp sensor @ APD (automatically in r/o only at the end) • LV + HV supplies • Slow control based on Lab. View • via CAN bus several LV/Temp control points from PCB recorded • Auto-implemented data transfer from scope (3+1 ch. Ampl) • Independent S/C for Magnet Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 5
Magnetic Field Scan #1 - ‘middle’ • 1 st PCB position in the middle solenoid parallel to line of magnet force, horizontally placed, homogeneous Mag. Field • about 2 hours scan 6. 5 up/down magnet + 7 min stable B • Variations in response @ (in) visible level (PIN x APD T- uncorr. ) Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 6
Magnetic Field Scan #2 - ‘slantways’ • 2 nd PCB position in the middle solenoid, placed on oblique surface ‘slantways’ ~25° angle, homogeneous Mag. Field • Variations in response @ (in) visible level (PIN x APD T- uncorr. ) • Overall scan ± 0. 5% difference (a bit more APDs), maybe B steps Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 7
Magnetic Field Scan #3 – ‘outer’ • 3 rd PCB position at the end of solenoid – ‘outer’ position, horizontally placed, no-homogeneous Mag. Field • response seems to rise contrary previous measurements for highest magnetic field B. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 8
Magnetic Field – Long-term • Over 8 hours long-term behavior in constant 4 T magnetic field • Almost (Temp ~0. 1%) constant conditions • Variations in response invisible • Amplitudes < 0. 5%; PIN diodes ~0. 5% noise level, APD less Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 9
Temperature dependence • Only, at the end of data measurement period automatically APD temperature sensor in r/o implemented • Correction formulas determined to be applied to data • 2(? , gain/pos. sensor) diff APD dependence, NO PIN dependence Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 10
Conclusion I q Calibration system – option II: electronic part QR LED driver reasonably works incl. Slow control interfaces can be implemented into EUDET AHCAL prototype q Characteristics and function described in public paper EUDET report 2008 -7 Prague AHCAL group q Optical part – notched fibres in preparation → promising results Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 11
Conclusion II, Outlook q Calibration system – QR LED driver in Magnetic field tests: works very well q meas. system sensitive to < 0. 5% variations in response q During constant magnetic field (standard operation conditions) the measurements are stable (w/o reference to PD temp. ) q Expecting one more measurement period § more precise orientations of PCB in mag. field § to avoid temperature dependence P. S. Thanks to DESY staff to allow to make such measurement Note: these days we have obtained one new notched fiber, which seems to fulfill our request on uniformity (light output ± 10%) Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 12
Backup slides Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 13
Option 2: Optical system • Idea: use one fiber for one row of tiles (72) • Problems: Notched fiber: • uniformity of distributed light • enough intensity of distributed light • concentration of LED light into one fiber • Two fibres: • Side-emitting - exponential fall of intensity • Notched fibre - better uniformity of distributed light - need to mechanize production - R&D • No optical cross talk seen (< 1 -2 %) @ different amplitudes 2 MIPs 10 MIPs 25 MIPs Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 14
Calibration system • • • Non-linearity correction, MIP calibration, Correction temperature variations Use gain monitoring, adjust voltage → see G. Eigen’s talk Many procedures developed during last year’s analysis, but not finally proven yet Stability of saturation still an issue -> need dynamic range Two appr. : electrical or optical signal distribution - One LED / one tile or central driver plus fibres Differences inside the active gap, but same external interfaces Option 2: LED driver • Electronics: multi-channel prototype complete • Optical system: uniformity again competitive • Integration into active layer still an open issue • Multichannel LED driver • 1 PCB with the communication module µC, power regulator, 6 channels of QRLed driver • Communication module to PC via CAN bus or I 2 C • Controlling the amplitude and monitoring temperature and voltages • LED pulse width ~ 5 ns fixed, tunable amplitude up to 50 -100 MIPs is controlled by the V-calib signal • 2 LEDs can be monitored by a PIN photodiode Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 15
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