VPT Stability Pulser

Note, 22.11.2010
Blue LED pulse heights from Dees  typically 200-300 ADC counts
Blue laser pulse heights                   typically 2000-3000 ADC counts, 600 pulses in calibration sequence
Red-Orange LED                          typically ~20 ADC counts

LEDs used in CMS from July 2008:  specification link
4 BLUE and 3 ORANGE LEDs to each diffusing sphere, via 7 fibres from one PCB
Blue
Luxeon III light emitting diodes (type LXHL-PR09), whose peak emission wavelength is 455 nm.
Very long operating life, to 100k hours (~12 years!)
Typical radiometric power (mW) for 700mA, Tjunction 25oC, = 340mW
Typical radiometric power (mW) for 1000mA, Tjunction 25oC, = 450mW
The LEDs are driven by high output current op-amps (LT6300 from Linear Technology).
The drive pulses have amplitudes of 1.2 A and a widths of 80 ns.
A single light source consists of a cluster of seven LEDs and associated drive-circuits
Red-Orange
Luxeon III light emitting diodes (type LXHL-PH09), whose peak emission wavelength is 617 nm
 Typical radiometric power (mW) for 1400mA, Tjunction 25oC, = 190mW 

Note, 19.11.2010
A new blue LED on the market: the LXHL-PR09 has been replaced by the MR-R0425-10S
Typical radiometric power (mW) for 700mA, Tjunction 25oC, = 740mW,
more than twice the current LEDs in CMS

LED manufacturers/Other experiments
Dmitri LED pulser box writeup

2010
 Blue/Orange LED results, A Ledovskoy  14.10  slides
LEDs, A Ledovskoy  12.10  slides
VPT stability studies at Point 5, A Ledovskoy  23.9  slides
VPT discharges, Eleni Petrakou 17.8 slides
Status report on VPT stability, A Ledovskoy 1.7 slides
Discussion on LED soak light operation in 2010/11, A Ledovskoy 22.4 slides
LED leakage, R Yohay 6.4 slides
LED status, R Yohay 16.2 slides
LED update, R Yohay 26.1 slides

2009
 VPT gain studies, A Ledovskoy 3.12 slides
Status of recent LED data, R Yohay 19.11 slides
Endcaps LED monitoring system, A Ledovskoy 15.10 slides
Progress with LED stability and monitoring studies at CRAFT09, A Ledovskoy 2.9 slides
Report from the endcap performance and stability group, A Ledovskoy 23.6 slides
 EE stability, A Ledovskoy 11.5 slides
Report from the EE performance and VPT stability group, D Cockerill 17.3 slides
Status of VPT related studies, A Ledovskoy 23.1 slides

2008
 VPT studies in situ and at Virginia, A Ledovskoy 9.12 slides
EE LED and VPTs, R Yohay  3.11 slides
UVa Pulser description in "The CMS experiment at the CERN LHC, p98 section 4.3.2"  14.8  pdf
UVa online results (new) 15.7 php  php-old
 Stability pulser discussion document - cabling/wiring/operation/layout R Yohay 3.7 txt doc
 Proposed modification to LED box design, M Scandurra 4.6

2007
 VPT (in)stability impplications for H4, R Yohay, DPG 12.8 ppt
 Test of fibre polishing on light yield, FINAL. P Hobson 23.7 doc
 Diffusing spheres on Dee1, M Scandurra 3.7
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 A possible fibre routing, D Cockerill 20.6 ppt
Space available within ring flange brackets, D Cockerill 21.5 ppt
Results from SC01 at RAL, D Cockerill 6.3 ppt
 Ferrule drawings, M Scandurra 5.3 pdf1 pdf2 pdf3 pdf4
 Possible positions around the ring flange for electronics and fibre termination, D Cockerill 5.3
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Ferrules for 7 fibres, M Scandurra 16.2 ferrule-7fibres  ferrule-3D-view  holder  sphere-3Dview

2006
 Hard clad silica fibres data sheet, B Camanzi 27.10 txt pdf
 Note 1 on single VPT calibration, P Flower 15.6 doc
First draft of specification for VPT stability system, P Flower & B Camanzi 26.5 doc

2005
Some progress with light into rear of SC, P Flower 23.9 doc
                 Fibres from diffusing sphere:
                 Into SC front, signal 29mV ≡ 8.7 GeV,
                 Into SC back, signal 24mV ≡ 7.2 GeV,
                 An off centre fibre into the back, signal 20mV ≡ 6 GeV
Calibration of single channel VPT unit for UVa vs single channel VPT unit at RAL, P Flower 20.9 doc xls
 Draft notes on tests with an LED pulser and a Supercrystal, P Flower, 19.8 doc
 Calibration: VPT+Stephenson preamp 5mV out ≡ 1.5 GeV 15.8 htm
 Photos of the VPT stability pulser test setup at RAL, P Flower/J Williams 9.8
               VPT pulser, fibre direct from LED pulser box:
                - into front of SC: 350mV out of Stephenson preamp connected to the SC, into 50ohm
                - into back of SC: 300mV out of Stephenson preamp connected to the SC, into 50ohm
                => acceptance, front and back more or less the same
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The 2 halves of the integrating sphere plus the fibre bundle (240 fibres) which goes to the crystals,
the closed sphere, showing the entry hole for the 1mm quartz fibre serving the LED signals,
the pre-cast box containing the LED pulser with single 1mm fribre just visible going directly into the front
of the SC onto crystal 25 for pulse height comparisons.
A check on "Setting the scale on the tests of Paul/Joolz", D Cockerill 1.2 htm
Setting the scale on the tests of Paul/Joolz, RM Brown 28.1 htm
J Williams/P Flower LED, drilled at front to take plastic fibre => into sphere at right angles to harness 28.1
             => fibre from harness directly onto VPT => 5mV out of  Stephenson preamp into 50W, equivalent to 1.5GeV

                        
2004
LED pulser tests, RM Brown, L Lintern 16.9 htm
             LED => 10cm quartz rod => into integrating sphere, air gap few mm to fibre harness
             => one fibre of the harness directly onto VPT => 200mV out of Stephenson preamp
Stability discussed in CMS Annual Review, EE Status, D Cockerill 7.9 (  transparencies )
Tests, shining an LED directly into integrating sphere, L Lintern/RM Brown, 3.8 doc
Observations on BTeV approach, RM Brown 5.8 htm
Thoughts on LED services to the Dees, RM Brown 3.8 txt
Light intensity from LEDs (including comments on CREE LEDs), RM Brown 27.7 doc
VPT Rate Dependence, measurements and discussion, RM Brown, M Sproston, Ken Bell 22.7 doc addendum
Towards a light pulsing system for EE, RM Brown 20.7 doc
LED light capture into a fibre, RM Brown 15.7 txt
Sanyo lasers for VPT LED system, RM Brown 15.7 txt
Hamamatsu handbook - hysteresis comments, RM Brown 14.7 txt
Pulse rates/levels for the LED pulser, RM Brown 13.7 txt
Caesium movement the cause of rate dependance? Photonis handbook, RM Brown 9.7 txt handbook ref
Rad damage in GaN LEDs, RM Brown 22.6 htm
VPT Rate Effects, K Bell 6.7 (  transparencies )