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Optical System for HCAL calibration Notched fiber prototype Optical X-talk Distance Tile-Fiber

Optical System for HCAL calibration Notched fiber prototype Optical X-talk Distance Tile-Fiber. Jaroslav Zalesak Institute of Physics, Prague. We consider 2 scenarios of calibration system for technical prototype of AHCAL. QR driver + LED 24*3cm ² area needed at the main PCB. 24 fibers

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Optical System for HCAL calibration Notched fiber prototype Optical X-talk Distance Tile-Fiber

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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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