bsc clean room procedures riccardo desalvo

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BSC CLEAN ROOM PROCEDURES

Riccardo DeSalvo

• These notes are based in part on Input and experience from LMA-Lyon

• The lesson learned are applied to the LIGO BSC chambers that house by far the most sensitive mirrors

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Cleaner mirror installation for Ad-LIGO

• The ITM and BS of the 2k have been contaminated, showed anomalous absorption and thermal lensing.

• This contaminant was easy to remove (drag-wipe)• The contaminant turned out being particles, possibly

soot, that entered the BSC during maintenance.• Ad-LIGO will be >>10 times more sensitive to thermal

lensing effects• Need to establish better defense against contaminants

See also T050068-00-R

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Cleaner mirror installation for Ad-LIGO

• Strippable paints, suggesting by Helena are a good start

• The main contaminant though, may be the operator that strips the paint and later performs the alignment

• Need an additional defense line• Laminar flow clean chamber is the

answer

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SCHEME OF A CLEAN ROOMSCHEME OF A CLEAN ROOM

Filtres

Air Propre

+ Flux

Laminaire

Laminar flow Screen

Clean Air

+ LaminarFlow

Absolute Filtres99,999 %

FANSRecycle

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Laminar Flow Turbulent Flow

Particles

The particles, are dragged away by the flow before they can diffuse on the

optics.Low polluting probability

The turbulent flow actually helps diffusing the particles

from the source to the optics High polluting probability.

Importance of air flow regimeImportance of air flow regimeImportance of air flow regimeImportance of air flow regime

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CORRECT MANIPULATIONCORRECT MANIPULATION

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INCORRECT MANIPULATIONINCORRECT MANIPULATION

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49

4

5

2

2

0

0

0

0

0

1

1

1

1

143

368

123

58

70

48

39

30

46

50

25

74

64

58

-350 -300 -250 -200 -150 -100 -50 0 50 100

0,2

0,3

0,4

0,5

0,6

0,7

1,0

1,5

2,0

3,0

4,0

5,0

7,0

10,0

Taille des particules en µm

Nombre de particules

InitialAprès 48 H sous flux turbulent"équivallent " Classe 100

Flux Turbulent « équivalant » Classe 100

Many large particlesMany large particles

Particle count on silicium waferParticle count on silicium waferParticle count on silicium waferParticle count on silicium wafer

10

1

0.1

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Flux Laminaire Classe 10

49

4

5

2

2

1

1

1

1

0

0

0

0

0

1

1

1

0

0

2

0

0

0

6

12

31

100

0

-120 -100 -80 -60 -40 -20 0 20 40 60

0,2

0,3

0,4

0,5

0,6

0,7

1,0

1,5

2,0

3,0

4,0

5,0

7,0

10,0

Taille des particules en µm

Nombre de particules

InitialAprès 48 H sous flux laminaireClasse 10

small significative small significative changechange

Particle count on silicium waferParticle count on silicium waferParticle count on silicium waferParticle count on silicium wafer

10

1

0.1

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the CLEAN ROOM WE NEED TO ESTABLISHthe CLEAN ROOM WE NEED TO ESTABLISH

Filtres

Air Propre

+ Flux

Laminaire

Laminar flow Screen

Clean Air

+ LaminarFlow

Absolute Filtres99,999 %

FANSRecycle

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BSC Volume and flow parametersBSC Volume and flow parametersBSC Volume and flow parametersBSC Volume and flow parameters

BSC cross section

Maximum

Laminar air speedFlow

6 m2 0,45 m/s ~ 3 m3/s

BSC heightReplacement

timeReplacement rate

~3 m ~1.5 s 2400 vol/hour

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How to implement laminar flowClean room facilitiesIn the BSC chambers

Pressurize optical benchUse threaded and additional holes as

laminar flow diffusersCollect the clean air with a sieved

floor

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Air inletGate valve

Drive bellow

Seismically isolatedOptical bench

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2.0 m3/s For annular

LaminarFlow

Curtain

1.0 m3/s For core ~laminar

flow

2.8m3/sSuction

7-8% outflow

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Laminar Flow curtains

Particles

The particles, are dragged away by the flow before they can diffuse in the turbulent flow

volume.But high turbulence induced in the optics region

can still generate particulate contaminationDiminished but not negligible polluting probability

Importance of air flow regimeImportance of air flow regimeImportance of air flow regimeImportance of air flow regime

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Laminar Flow curtains plussemi-laminar flow core

Particles

The suspension mechanics disturbs the otherwise laminar flow. Particles from outside are screened off by the laminar

flow curtain. Particles injected by the operator in the semi-laminar volume are still dragged away by the flow although

less effectively.Minimized polluting probability

Importance of air flow regimeImportance of air flow regimeImportance of air flow regimeImportance of air flow regime

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Due to the quad suspensionStructures it is impossible toEstablish pure Laminar Flow in the test mass region

Importance of air flow regimeImportance of air flow regimeImportance of air flow regimeImportance of air flow regime

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Detailed Flow conditions To be simulatedExample: Flomerics.com

Importance of air flow regimeImportance of air flow regimeImportance of air flow regimeImportance of air flow regime

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Flow conditions to be simulated

Examples of clean room air flow simutationExamples of clean room air flow simutationExamples of clean room air flow simutationExamples of clean room air flow simutation

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The Laminar Flow curtains plussemi-laminar flow core seem to be the best solution for the BSC chambers andGuarantee a reasonable Protection against contaminants

Importance of air flow regimeImportance of air flow regimeImportance of air flow regimeImportance of air flow regime