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HF Laser/LED Calibration StudiesL. Almeida, M. Baarmand, L. Caraway, M. Hohlmann, T. Qureshi, I.
VodopianovFLORIDA 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 pulsesw/ single-shot andexternal triggercapability
10 m jacketed optical fiber
2
N2 Laser
300 QQ 75m
CLI ROBox 3
CALIB
Box
1 4
Counting Room
HF Calibration Optical Path
Test Beam 2002
200 J 337 nm
9
600 QP 18m
300 QQ
9m
3
4
LED 2
MIXER 50mm 15mm 15mm
PolystyrenePIN3
ADC
9600 QP
300 QQ
Blue Scintilator 8mm 4mm 8mm
Calibration Box - 1 x 9 splitter
To CLI in PMT Box
PIN Diode 4mm 4mm
Pulser
PIN1PIN2
LED 1
5
Calibration Light
Injector (CLI)
Empty PMT TUBE
Light GuideNon-reflective coating
Light Guide
600 QP
PMT BOX
5
120
SHIELDING
600 QP
40cm
Light GuidePMT
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% Nonuniformity
8
HF Laser/LED Calibration IssuesTest 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 14 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 1548-10 fibers!!!
R O Box 3
10
N2 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
75 + 0 3.5
CMS UV Laser upstairs
150 + 20 17
CMSUV Laser downstairs
20 + 20 2
CMSDYE Laser upstairs
150 + 20 2
without splitter attenuation
11
300 QQ
QQ (Silica)
300 QQSMA 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 mm3
PIN
10 × 600
fiber bundle
Ø3mm (7mm2)Light collection:
0.1% by bundle, 0.004% by each fiber
Sc
inti
llato
r 8
4
8
mm
3
ε =
10%
Total efficiency = 4106 per output fiber
Present Calibration Box
) 22°
10 × 600
fiber bundle
Ø3mm (7mm2)
13
20 7 4 mm3
Max light collected within 22° = 3.6%
max efficiency for this mixer+bundle
= 1.4105 per output fiber
LED
~10 times better
efficiency ~ 4105
Calibration Box with smaller mixerto be tested
laser
PIN
10 × 600
fiber bundle
Ø3mm (7mm2)
14
SMA Connector
Holographic Diffuser
Present C L I → Calibration Bundle
Light guide
Lens (F=11mm Ø=6mm)
Efficiency = 1.9 × 104 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)
SMAfiber
60°diffuser
10°diffusers
Lens Ø = 16mm F = 20mm
current
Estimated efficiency
≈ 1.7 × 103 per PMT
~ 10 times better !
16
Results from 2002 test beam
• Estimated total efficiency = 2.21010 – attenuation of UV in fibers = 3.5
– CALIB Box efficiency = 4106
– CLI → bundle efficiency = 1.9104
• Attenuation (bundle → PMT) ≈ 2*• Hamamatsu: QE(PMT) = 27%• Test beam: (laser → PMT) = 74 PE (wish 750 PE!)
• 2.51012 laser photons • 200J is 3.31014 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 18 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