Radiation Damage Passive Components

ATLAS/CMS Opto WG March '10

Tony Weidberg 1

Radiation Damage Passive Components

• Versatile Link WP 2.3– Todd Huffman, Mark Jones, Nick Ryder & Tony Weidberg

• Summary radiation tolerance GRIN and SM fibres– Qualified for warm operation

• RIA variation with Temperature• Plans for RIA measurements at -25C.• Fibre Bandwidth after irradiation.• Other passive components being studied

– PLC splitters @Radiatio 1310 nm– LC & MT connectors.


Tony Weidberg 2

GRIN Fibres

VCSEL @ 850 nm source

Brigitte Co60 source up to full SLHC dose (kGy)

Also performed tests at lower doses, Rita and BNL.


Tony Weidberg 3

SM Fibre• SMF-28 SM fibre, 1310 nm EEL source.

• SMF-28 better radiation tolerance than GRIN fibres (as expected for longer ).


Tony Weidberg 4

Summary Fibre RIA

• Assume plausible fibre routing based on ATLAS SCT

• Conservative calculation of total RIA at end of SLHC ignoring long term annealing– Predicts 0.4 dB for RIA for Infinicor SX+ fibre.– Infinicor SX+ fibre qualified for SLHC if operated

warm.– Draka RHP-1 and SMF-28 better than Infinicor SX+

fibre also qualified for warm operation. – 2 candidate fibres for SM (also have Fujikura fibre

for LHC machine) and MM.


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Cold Operation

• Inner Detectors will be operated cold @ SLHC (~ -25C).

• Will this affect the fibre radiation damage?

• Limited information available in the literature …


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Previous research on RIA in fibreMulti-mode

Single-mode

850 nm GRIN fibre at room temp (curve C) and -17 C (curves A & B)credit: Thériault Radiation effects on COTS laser-optimized graded-index multimode fibers exposed to intense gamma radiation fields

Single-mode RIA as fcn of temp.credit: Kanamori et al. Transmission Characteristics and Reliability of Pure Silica-Core Single-Mode Fibers

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RIA is temperature-dependent!


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Cold Irradiation of Fibres• First tests at Rita low dose rates

• Use Peltier coolers -25C.

4 Peltiers take heat from Al spool and dump it into water outside the cylinder.

Worked ok for low dose but can’t work for high dose because heat load too big and radiation resistance of Peltiers not good enough.


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Comparisons, InfinicorSX+

T = +300 CDose = 65 kGy(Si)

T = -23.30 CDose = 30 kGy(Si)

Gamma sourceat room temperature.Variation is from prev.Stability limitations.


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Draka RHP-1 SRH fibre

T = -250 C

T = -40 CTotal Dose ~ 15 kGy(Si)


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Cold Irradiation Status

• Clear evidence that RIA for GRIN fibres is significantly larger at low T than room T.

• Need compact, rad-hard cooling system that can operate ~ -25C…


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Blow-off Evaporative CO2 System

CO2 bottle (50bara, 20°C)

vent

Service tube

Hex

Control room

Test vessel

capillaryEvaporator

Electrical heater

Return & feed pipe ¼” OD SS

Some flexible SS tubing needed here

Some flexible SS tubing needed here

Ice is likely to form in this tube!

Back pressure regulator (BPR)


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CO2 Cooling

• The C02 blow-off cooler progresses!

• Passed first safety test in Oxford (water).

• Start to test it as cooling system iterate lengths of capillary to achieve required pressure drops.

• Further safety tests and approval from SCK safety commission before it can be operated at SCK.


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Bandwidth Studies

• Many studies of fibre radiation tolerance but none (?) of fibre bandwidth after irradiation.

• Perform before/after radiation comparisons of the fibre bandwidth.

• First measurements (Annie Xiang)

• Draka measurements


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Fibre Bandwidth Summary• Draka MMF-RH(1) is optimised for bandwidth

but should have same RIA as Draka MMF(1).• No evidence for significant degradation with

radiation but precision limitted.• Better measurements to be performed by Draka

on long fibre sample.

2 m 50m unirradiated 50 m irradiated

Rise (ps) 68 66 68

Fall (ps) 54 84 86


Tony Weidberg 18

Splitters (1)

• Fused taper splitters– Radiation damage is simply equal to

length of fibres used but devices are bulky.

• PLC Splitters– More compact– Radiation tolerance needs to be verified.– First samples from Leoni with active tests

gave inconclusive results (effects of temperature and radiation combined).


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Splitters (2)• Obtained samples 1*4 splitters from different manufacturers

– Browave (Taiwan): 10 devices– Huihong Technologies (China): 4 devices– Fibrenet packaging of 2 devices from WUHAN YILUT OPTICAL

COMMUNICATION CO.,LTD (Taiwan)– Fibrenet package of 1 device from Cololr-Corp: glass substrate

(not Si).– (Promised new samples from Leoni)

• Measure insertion loss before irradiation with multiple mate/demate cycles (all devices look ok).

• Study temperature effects with thermal cycling in environmental chamber.

• Irradiate at room temperature to 500 kGy(Si) using Mega Curie source in Taiwan.

• Repeat measurements after irradiation.

Radiation Damage Passive Components

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