LED stability pulser tests at RAL
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LED stability pulser tests at RAL Paul, Barbara, Bob, Dave. Diffusing sphere. 1 to 7 fibres in. 240 fibres out 25 into SC01. Nichia NSPB500S LEDs. SC01 read out with 25 stephenson preamps. Fibres to inject into diffusing sphere.

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1 to 7 fibres in

LED stability pulser tests at RAL

Paul, Barbara, Bob, Dave

Diffusing sphere

1 to 7 fibres in

240 fibres out25 into SC01

NichiaNSPB500SLEDs

SC01 read out with 25 stephenson preamps


1 to 7 fibres in

Fibres to inject into diffusing sphere

Quartz fibreSupplied by Applied Photonics, manufactured by Laser Components.

The Laser Components reference is CF01493-43.

The fibre has 550um inner silica core,

600um including silica cladding, 

630um including a 'hard coating' (for mechanical strength)

750um including the plastic buffer.

Note that the plastic is EFTE ETFE (Ethylene TetrafluoroEthylene), a fluorocarbon-based polymer

500m

750m


1 to 7 fibres in

RMB xls, 21.2.07 at 19.08

SC01

Not usedFront fibre data, ABL ch 3 & 4, <0.1 normal sizePlastic fibre data ABL ch 7, appears double normalAll data, ABL ch 18: very high p*g=2.7, g=15.0


1 to 7 fibres in

Stephenson preamp calibration

Indicates preamp gains are all close to each other

Signal from fibres out of diffusing sphere

Narrow width indicates good uniform illumination of fibres with sphere


1 to 7 fibres in

  • Fibre signal versus VPT P*G

  • Into front directly via LED + single fibre only

  • Single Quartz fibre to sphere – fibres from sphere into back of SC01

  • Ditto Single Plastic fibre

  • Ditto Plastic re-measured in Sep


1 to 7 fibres in

  • Fibre signal normalised to VPT P*G

  • Into front directly via LED + single fibre

  • Single Quartz fibre to sphere – fibres from sphere into back of SC01

  • Ditto Single plastic fibre to sphere

  • Ditto plastic re-measured in Sep


1 to 7 fibres in

Slope 0.08 GeV per e/MeV

  • Fibre signal versus VPT signal at 1.8T

  • Into front directly via LED + single fibre

  • Single Quartz fibre to sphere – fibres from sphere into back of SC01

  • Ditto Single plastic fibre to sphere

  • Ditto plastic re-measured in Sep


1 to 7 fibres in

  • Fibre signal normalised to VPT signal at 1.8T

  • Into front directly via LED + single fibre

  • Single Quartz fibre to sphere – fibres from sphere into back of SC01

  • Ditto Single plastic fibre to sphere

  • Ditto plastic re-measured in Sep


1 to 7 fibres in

  • To estimate yield of LED stability pulser system in GeV at 1.8T

  • Assume SC01 stephenson preamps have same gain as those used in testbeam in 1999: Preamp input of 1.4.106 electrons gives 104mV peak O/P into 50To be checked asap

  • That 7 quartz fibres into sphere = 7 times output of one quartz fibre into sphere

  • That the quartz fibres are those for CMS

  • Use measured response with quartz fibre calibrated againstVPT yield at 1.8T of:0.08 GeV per e/MeV

  • Comment

  • Drive pulse via Dmitri box at present – expect to do better in future


1 to 7 fibres in

  • LED stability pulser system. Energyequivalent output in GeV

  • Measured VPT yields at 1.8T at RAL in e/MeV

  • LED signals with one quartz fibre into diffusing sphere

  • LED signals with 7 quartz fibres into diffusing sphere

Target:Mean output 120 GeV

Some way to go!


Conclusions

Conclusions

With 7 quartz fibres into sphere, mean signal size 20 GeV

Want 120 GeV

Must account for crystal and VPT darkening at LHC

Should start with a system capable of delivering 200 GeV


1 to 7 fibres in

University of Virginia offer/contribution, Brad Cox email Feb 3, 2007

Mike A. be named the "VPT Stability system coordinator". This is part of a bigger issue.

Be an ESSENTIAL part of design of the blue LED stability/backup calibration system.

Mike has make a preliminary sketch of the functionality that one needs Hirosky and Andelin are working with him on the design of driving electronics to optimize the blue LED light yield and will take over from Dave Phillips the remainder of the testing as soon as Dave finishes his note on the present results.

Mike's work: in UVa to finish the burn-in boxes for FPIX. We delivered two boxes to Fermilab and they are working fine so he can put systems together.

Plus he has the UVa group already involved with the LED work and feeling that they have some stake in it.

Get support by US CMS for the construction of the system (in addition to the flashers themselves, there is the issue of synching with the beam structure, the slow controls and a host of things to think through).


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