1 HF Laser/LED Calibration Studies L. Almeida, M. Baarmand, L. Caraway, M. Hohlmann, T. Qureshi, I. Vodopianov FLORIDA TECH 1->9 light splitter w/ pulsed LEDs, input for UV laser pulses, and PIN diode light monitoring 1->4 light splitter Electronic pulser for ~100 ns LED pulses w/ single-shot and external trigger capability 10 m jacketed optical fiber

2 N 2 Laser 300  QQ 75m CLI ROBox 3 CALIB Box 1  4 Counting Room HF Calibration Optical Path Test Beam  J 337 nm  QP 18m 300  QQ 9m

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4 LED 2 MIXER 50mm  15mm  15mm Polystyrene PIN3 ADC  QP 300  QQ Blue Scintilator 8mm  4mm  8mm Calibration Box - 1 x 9 splitter To CLI in PMT Box PIN Diode 4mm  4mm Pulser PIN1 PIN2 LED 1

5 Calibration Light Injector (CLI) Empty PMT TUBE Light Guide Non-reflective coating Light Guide 600  QP PMT BOX SHIELDING 600  QP 40cm Light Guide PMT Some PMTs have more or fewer than 5 fibers !!!

6 Calibration Light Injector (CLI)

7 SMA Connector Fiber 600  QP Jacket SMA Connectors Holographic Diffuser Plate 2Plate 3 SMA-SMA connector Fiber Ferrule Calibration Light Injector in R O Box 3 Calibration Tube 9cm Aspheric Lens 11mm Focal Length Collimation Assembly ±4% Non uniformity

8 HF Laser/LED Calibration Issues Test Beam 2002 Insufficient light intensity –low laser output power  laser used at test beam misaligned or badly focused? –attenuation of UV in fibers  move laser downstairs / use DYE (blue) laser –small efficiency in 1  4 splitter, CALIB Box, CLI  improvements under investigation – see below –low LED light  use brighter LEDs and drive at higher bias voltage? Non-uniformity as seen by PMTs (~20%) –mostly due to light guides and calibration fibers downstream of CLI

9 PMT fibers!!! R O Box 3

10 N 2 Laser 75m/150m/20m 300  QQ CALIB Box 1  4/8 Counting Room 300  J 337 nm 0m/20m/20m 300  QQ Attenuation of UV in 300  QQ Atten. Length = 60m length (m)attenuation Test beam CMS UV Laser upstairs CMS UV Laser downstairs CMS DYE Laser upstairs without splitter attenuation

 QQ  QQ (Silica) 300  QQ SMA connectors Splitter 1 × 4 (1 × 8) efficiency 75 mm cross section ratio  11 (9%) Lab, red/blue 4.5% Test beam, UV 2.5% 1 × 8 (calc. UV) 1.3%

12 laser Mixer 50  15  15 mm 3 PIN 10 × 600  fiber bundle Ø3mm (7mm 2 ) Light collection: 0.1% by bundle, 0.004% by each fiber Scintillator 8  4  8 mm 3 ε = 10% Total efficiency = 4  10  6 per output fiber Present Calibration Box ) 22° 10 × 600  fiber bundle Ø3mm (7mm 2 )

13 20  7  4 mm 3 Max light collected within 22° = 3.6%  max efficiency for this mixer+bundle = 1.4  10  5 per output fiber LED ~10 times better efficiency ~ 4  10  5 Calibration Box with smaller mixer to be tested laser PIN 10 × 600  fiber bundle Ø3mm (7mm 2 )

14 SMA Connector Holographic Diffuser Present C L I → Calibration Bundle Light guide Lens (F=11mm Ø=6mm) Efficiency = 1.9 × 10  4 per PMT CALIB Bundle 120 × 600  lens  = 16% 5 fibers  = 0.12% with non-uniformity of 4%

15 Modified Calibration Light Injector (to be tested) SMA fiber 60°diffuser 10°diffusers Lens Ø = 16mm F = 20mm current Estimated efficiency ≈ 1.7 × 10  3 per PMT ~ 10 times better !

16 Results from 2002 test beam Estimated total efficiency = 2.2  10  10 –attenuation of UV in fibers = 3.5 –CALIB Box efficiency = 4  10  6 –CLI → bundle efficiency = 1.9  10  4 Attenuation (bundle → PMT) ≈ 2 * Hamamatsu: QE(PMT) = 27% Test beam: (laser → PMT) = 74 PE (wish 750 PE!)  2.5  laser photons 200  J is 3.3  photons (~100 times higher!) * Obtained by combining LEDs power output and test beam measurements – in agreement with measured light guide attenuation

17 Outlook (laser calibration) Improvements: –UV laser downstairs or DYE laser   1.8 –Better CALIB Box efficiency   10 –Better CLI efficiency   10 Efficiency of 1  8 splitter = 1.3%  overall efficiency increased by ~ 2 Possible laser power recovered up to ~10 times (to be confirmed with measurements)

18 Outlook (LED calibration) LED subsystem is independent of splitter efficiency and UV attenuation Improvements: –use more powerful LEDs assume this to be compensated by gate 100ns → 25ns –improve CALIB Box and CLI as above  overall efficiency increased by ~ 100