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Developing Optical System for AHCAL Calibration with Notched Fiber Prototype

Explore two calibration scenarios for AHCAL technical prototype involving QRLed driver and LED for light distribution. Utilize notched fibers for improved light output and uniform distribution across tiles. Investigate optical X-talk effects on MIP beta sources and LED light triggering. Assess distance fiber-tile coupling for stability and amplitude monitoring. Conclude with insights on fiber performance and the importance of precise measurements and setup improvements.

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Developing Optical System for AHCAL Calibration with Notched Fiber Prototype

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  1. Optical System for HCAL calibration • Notched fiber prototype • Optical X-talk • Distance Tile-Fiber Jaroslav Zalesak Institute of Physics, Prague CALICE, Manchester Sep 9, 2008

  2. We consider 2 scenarios of calibration system for technical prototype of AHCAL QR driver + LED 24*3cm² area needed at the main PCB 24 fibers Each for ~ 70tiles • Fiber emmiting light for one row of tiles, QRLed driver sitting outside of module (endcap)  development of the light distribution system • QRLed driver is sitting at HBU above the scintillator CALICE, Manchester Sep 9, 2008

  3. Light distribution system • Side-emitting fibres Thin fibres (~1mm) needed, unknown parameters, not common →FiberTech (SLS600 series) • ’Notched’ fibres Making notches on fibres requires a specialized firm → Safibra comp. • Focusing LED light into fibre → Optical lab of the CU Prague Notched fibres appear promissing: • Response over 2.2m length drops linearly by 40%, RMS ~ 14% • Light output from notched fibers > ~ 3 times higher CALICE, Manchester Sep 9, 2008

  4. Notched fiber prototype #3 • Light output from fiber via notches uniform over all 70 points • Approaching ±20% proposed limit of light variation • New (better) notched fiber is expected soon CALICE, Manchester Sep 9, 2008

  5. Optical X-talk on MIP β-source with fiber Β spectrum • Sr beta source to SiPM1 • triggered by coinc. w/PM • notched fiber SiPM 1→2 • at length of 9 cm • ½ MIP on position 135 w/o fiber • ➢ Normalized spectra w/ and w/o fiber are same • NO optical X-talk visible for MIP beta spectra CALICE, Manchester Sep 9, 2008

  6. Optical X-talk on LED light • Much more light to tile (up to 25 Mips) • not particle but tunable amplitude • better triggering 2 MIPs 10 MIPs • LED light to SiPM1 • notched fiber SiPM 1→2 • at length of 9 cm • ½ MIP on position 135 25 MIPs CALICE, Manchester Sep 9, 2008

  7. Optical X-talk on LED light results Noise ½ MIP detail 2 MIPs 10 MIPs 25 MIPs • No differences in response from various amplitudes • NO optical X-talk visible for large amount of light in tile • no dependence on chosen pair of notches and light input direction CALICE, Manchester Sep 9, 2008

  8. Distance Fiber-Tile • variable sheet width in space of coupling (air) • of fiber notch and tile • two intensities of input led light from LED driver • one tile w/ SiPM direct coupling • → monitoring of stability (yellow and green) • second measure amplitude (blue and red) Preliminary results: • not so good reproducibility (10%) • significant drop in response • decrease with bigger distance (30%) • visible even on small widths • some additional reflections in case direct coupling wrt. some materials? • better geometrical setup? CALICE, Manchester Sep 9, 2008

  9. Conclusion • we have got and measured promising fiber with notches wait for new prototype w/ uniformed light distribution within ranges ± 20% • we do not expect (or less 1-2%) optical X-talk between tiles from notch coupling even on high light intensity • we observed significant drop in response from tiles with not directly coupled fibers → need more precise measurement, better couplings and geometry setup Btw: in 1 week new designed PCBs for QR-Led driver go to production CALICE, Manchester Sep 9, 2008

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