LED stability pulser tests at RAL
Paul, Barbara, Bob, Dave
Diffusing sphere
1 to 7 fibres in
Nichia
NSPB500S
LEDs
240 fibres out
25 into SC01
SC01 read out with
25 stephenson
preamps
Fibres to inject into diffusing sphere
Quartz fibre
Supplied 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
SC01
RMB xls, 21.2.07 at 19.08
CRISTAL
Not used
Front fibre data, ABL ch 3 & 4, <0.1 normal size
Plastic fibre data ABL ch 7, appears double normal
All data, ABL ch 18: very high p*g=2.7, g=15.0
ABL #
1
5
2
6
3
11
4
16
5
21
6
4
7
7
8
12
9
17
10
22
11
3
12
8
13
13
14
18
15
23
16
2
17
9
18
14
19
19
20
24
21
1
22
10
23
15
24
20
25
25
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
Fibre signal versus
VPT P*G
1) Into front
directly via LED
+ single fibre
only
2) Single Quartz
fibre to sphere
– fibres from
sphere into
back of SC01
3) Ditto Single
Plastic fibre
4) Ditto Plastic remeasured in
Sep
Fibre signal
normalised to
VPT P*G
1) Into front
directly via LED
+ single fibre
2) Single Quartz
fibre to sphere
– fibres from
sphere into
back of SC01
3) Ditto Single
plastic fibre to
sphere
4) Ditto plastic remeasured in
Sep
Slope 0.08 GeV
per e/MeV
Fibre signal
versus VPT
signal at 1.8T
1) Into front
directly via LED
+ single fibre
2) Single Quartz
fibre to sphere
– fibres from
sphere into
back of SC01
3) Ditto Single
plastic fibre to
sphere
4) Ditto plastic remeasured in
Sep
Fibre signal
normalised to
VPT signal at
1.8T
1) Into front
directly via LED
+ single fibre
2) Single Quartz
fibre to sphere
– fibres from
sphere into
back of SC01
3) Ditto Single
plastic fibre to
sphere
4) Ditto plastic remeasured in
Sep
To estimate yield of LED stability pulser system in GeV at 1.8T
1) 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
2) That 7 quartz fibres into sphere = 7 times output of one quartz fibre
into sphere
3) That the quartz fibres are those for CMS
4) Use measured response with quartz fibre calibrated against
VPT 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
LED stability pulser
system. Energy
equivalent output in
GeV
a) Measured VPT
yields at 1.8T at RAL
in e/MeV
b) LED signals with one
quartz fibre into
diffusing sphere
c) LED signals with 7
quartz fibres into
diffusing sphere
Target:
Mean output 120 GeV
Some way to go!
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
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).