1. LED calibration systems for CALICE hadron calorimeter Jiri Kvasnicka (kvas@fzu.cz) Institute of Physics, Prague June 11, 2011TIPP 2011, Chicago1 Under HEAVY CONSTRUCTION

2. Outline Calice prototype SiPM Motivation (SiPM issues, temeperature drift..) AHCAL 1m^2 solution – Electronics solution – performance Embeded solution – Electronics solution – Performance Quasi-resonant LED driver – Electronics solution – Performance Light distribution June 11, 2011TIPP 2011, Chicago2

3. AHCAL 1m 2 Physics prototype The AHCAL 1m 2 - CALICE experiment – built in 2005 – Testbems 2006-2010 at CERN and FNAL. – Now in CERN as WHCAL – Tested together with ECAL (electromagnetic calorimeter) and TCMT (Muon calorimeter) 38 layers, 2cm Fe absorbers 7608 photo detectors (SiPM) in total One layer – 216 scintillator tiles, 3x3, 6x6, 12 x 12 cm2, – Calibrating system (CMB) with 12 LEDs monitored by PIN- Photo Diodes – Optical flash is distributed by fibre bundle individually to each scintillator – 5 temperature sensors per layer - integrated circuits LM35 Scintillating tile – 5mm thick Scintillator – WLS (wavelength shifting fiber), ~380nm  ~500nm) – SiPM photodetector attached to the WLS fiber + mirror SiPM (silicone photomultiplier) – 1156 pixels, each works in Geiger mode – Gain of SiPM ~10 5 to 10 6 June 11, 2011TIPP 2011, Chicago3 ECAL HCAL TCMT 20mm Fe plates and scintillators 3 cm 1 mm 90 cm AHCAL`

4. Calibration Chain: ADC to MIP AHCAL signal chain: Particle  MIPs  Scintillating tile  photons (UV)  Wavelength-shifting fibre  photons (green)  SiPM  Photo-electrons  ASIC readout Calibration task: Convert the detector signal to a number of MIP deposited by the particle The means on calibration: – LED light! – Charge injection – Beam: Muon tracks identification and calibration – Cosmic muons – Other means: Laser, Radioactive material Measured parameters: – SiPM gain (from Single Photon Spectrum) – Temperature (gain factor -2% per 1K) – Saturation function June 11, 2011TIPP 2011, Chicago4

5. MUONS Particle detection LED light June 11, 2011TIPP 2011, Chicago5

6. CMB-ToDo El. Zapojeni, simulace June 11, 2011TIPP 2011, Chicago6

7. CMB-results ToDo Jara’s calibration plots, SPS, etc. June 11, 2011TIPP 2011, Chicago7

8. Integrated LED system LEDs Developed by DESY and Uni Wuppertal Each Tile has its through-hole mounted LED Each LED has its own driver circuitry. – Operation: The current pulse though the LED is generated by discharging of the Capacitor by a fast transistor – V-calib signal range: 3–10 V – System tuned for ~8 ns pulses Choice of the LED is critical for this driver – Several different LED types were tested (see next slide) – The technology of the LED is most important Only Single-quantum-well LEDs work well (usually UV- LED) Usual (multi-quantum-well) LEDs have too big capacitance and produce longer optical pulse. On the other hand, they are very bright Driver circuitry is now optimized and being manufactured on the new HBU for the technological prototype June 11, 2011TIPP 2011, Chicago8 5 ns

9. Integrated LED system – Optimization Pulse of the Blue LED is much wider (~40 ns), than the UV LED (~5 ns) Light pulse width re-measured with a differential driver – In this mode: LED is reverse biased, then for a short pulse forward biased and directly reverse biased again – The reverse voltage helps to discharge the LED – Blue LED stops shining much faster in differential mode June 11, 2011TIPP 2011, Chicago9 Blue LED UV LED Blue LED, differential

10. Integrated LED system – SPS For longer (>30 ns) pulses, both UV and Blue LEDs produce equal optical pulses Observation: UV LED have much steeper rise time Driver circuitry is now optimized and being manufactured on the new HBU for the technological prototype Question: is short pulse necessary? – Answer: Yes, only 15 ns pulses and faster produce decent Single Photon Spectra Single Photon Spectrum (SPS) – Short pulse -> improvement of the quality – Nice spectrum with UV-LED – Spectrum is more smeared with 30 ns blue-LED June 11, 2011TIPP 2011, Chicago10 Blue LED, 30 ns Blue LED, 15ns UV LED, 7ns

11. Integrated LED system – Light Yield Measurements with key components variation Circuitry was finally tuned to deliver up to 17K effective pixels – Light referenced to PMT signal Time behavior of the LED – Measured with PMT – Without tile: sharp pulse – With tile (and Wavelength shifting fibre)  long tail June 11, 2011TIPP 2011, Chicago11 Resistor variation Capacitor variation With Tile 25 ns

12. QMB6-ToDo June 11, 2011TIPP 2011, Chicago12

13. QMB6-ToDo June 11, 2011TIPP 2011, Chicago13

14. Notched Fibre June 11, 2011TIPP 2011, Chicago14 24-notched fibre at the left figure. Illuminated by a green laser Light is emitted from the notches The notch is a special scratch to the fibre, which reflects the light to the opposite direction The size of the notch varies from the beginning to the end of the fibre First notchMiddle notchEnd position notch Emission from the fibre (side view)

15. Optical fibre Measurements of the light yield – Through the 3mm hole on the PCB (FR4 with filled inner layer) – 3 positions of the notch according to the PCB thru- hole June 11, 2011TIPP 2011, Chicago15 “start” position“middle” position“end” position

16. Notched fibers configuration 72 zarezova vlakna – vysledky linearity LED vyzarovaci profil (smolda) Konfigurace 3*24 zarezu June 11, 2011TIPP 2011, Chicago16 HBU6HBU5HBU4HBU3HBU2HBU1

17. Development of new Quasi-resonant driver (QMB1) QMB1 (1-chanel LED driver): – Fixed Topology Communicating bus (CAN) CPU (Atmel AVR) Trigger distribution (LVDS) Trigger delay can be tuned by C trimmer (~10ns) Free to adjust: will be discussed at DESY in July calib meeting – Mounting holes (fixation to support/HBU – Fibre(LED) position Set of notched fibers, semi-automat machine under development – Set: 3*fiber with 24 notches, creating a line of 72 notches. – 3 sets will be delivered June 11, 2011TIPP 2011, Chicago17 HBU6HBU5HBU4HBU3HBU2HBU1

18. Conclusion June 11, 2011TIPP 2011, Chicago18