1

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%

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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%

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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 !

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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

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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)

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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