LED calibration systems for CALICE hadron calorimeter June 11, 2011TIPP 2011, Chicago1

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

Calice 1m 2 prototype ToDo ECAL HCAL TCMT 20mm Fe plates and scintillators 90 cm HCAL 3 cm 1 mm June 11, 2011TIPP 2011, Chicago3

SiPM Issues – need for Calibration ToDo Obrazek – vysec snimace, Danilov- experimenty?? Jara vlivy na saturacni prubeh – cas, zpozdeni svetla, cas do nabiti… June 11, 2011TIPP 2011, Chicago4

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

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

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

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) Other (multi-quantum-well) LEDs have too big capacitance and produce longer optical pulse (with low-intensity “tail”) Driver circuitry is now optimized and being manufactured on the new HBU for the technological prototype June 11, 2011TIPP 2011, Chicago8 5 ns

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 June 11, 2011TIPP 2011, Chicago9 Blue LED UV LED Blue LED, differential

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, 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 blue- LED Light yield of the integrated LED June 11, 2011TIPP 2011, Chicago10 Blue LED, 30 ns Blue LED, 15ns UV LED, 7ns

Integrated LED system – Light Yield Measurements with key components variation Circuitry was finally tuned to deliver ~2K (12K???) effective pixels – Light referenced to PMT signal – ~500 pixels were fired (saturation) Time behavior of the LED – 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

QMB6-ToDo June 11, 2011TIPP 2011, Chicago12

QMB6-ToDo June 11, 2011TIPP 2011, Chicago13

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)

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

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

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 canbe 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, semiautomat machine under development – Set: 3*fibre with 24 notches, creating a line of 72 notches. – 3 sets will be delivered June 11, 2011TIPP 2011, Chicago17