1. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 1 QRLed Driver in Magnetic Field Jaroslav Zalesak Institute of Physics of the ASCR, Prague

2. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 2 QRLD board (ASCR Prague): „Quasi Resonant LED Driver Board“, 6 LEDs / 1 PCB Notched fibers Each illuminates 12 tiles Calibration Option 2: LED driver CALIB module Option I 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 HBU

3. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 3 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 I2C 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 QRLED 1 T-calib V- calib Power regulator QRLED 6 LED 1 LED 6 +12V FIBRESFIBRES µC AT91SA M7X256

4. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 4 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

5. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 5 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 LabView 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

6. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 6 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 2hours scan 6.5 up/down magnet + 7min stable B Variations in response @ (in) visible level (PIN x APD T- uncorr.)

7. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 7 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

8. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 8 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.

9. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 9 Magnetic Field – Long-term Over 8 hours long-term behavior in constant 4T magnetic field Almost (Temp ~0.1%) constant conditions Variations in response invisible Amplitudes < 0.5%; PIN diodes ~0.5% noise level, APD less

10. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 10 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

11. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 11 Conclusion I  Calibration system – option II: electronic part QR LED driver reasonably works incl. Slow control interfaces  can be implemented into EUDET AHCAL prototype  Characteristics and function described in public paper EUDET report 2008-7  Optical part – notched fibres in preparation → promising results Prague AHCAL group

12. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 12 Conclusion II, Outlook  Calibration system – QR LED driver in Magnetic field tests:  works very well  meas. system sensitive to < 0.5% variations in response  During constant magnetic field (standard operation conditions) the measurements are stable (w/o reference to PD temp.)  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%)

13. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 13 Backup slides

14. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 14 Option 2: Optical system Idea: use one fiber for one row of tiles (72) Problems: 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 Notched fiber:

15. Feb 20, 2009 CALICE meeting, Daegu, Korea QRL in Magnetic Field 15 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 I2C 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