Monitoring Vacuum Quality Using A

Residual Gas Analyzer

Julio BarbosaLawrence Livermore National Labs

CFAO Intern 2004

Today’s High Tech Industry

Today’s High Tech Industry• As technology advances the requiredmanufacturing processes becomeincreasingly complex

• Manufacturing must be carried out in strictly controlled environments

• Clean rooms and vacuum systemsare required

The VLOC Project

•VLOC will require operation in a cleanhigh vacuum

•High vacuum doesn’t mean clean vacuum

•Measuring minute amounts of matteris a non-trivial task

Residual Gas Analyzers

How An RGA Works

= A mass spectrometer

• Ion Source+

• Mass Filter+

• Ion Detector

The Test Chamber

Testing Materials

Materials tested:

•O-rings•Wax sealant•Oil from fingerprints

First test conducted with anempty chamber for a baseline

1.825E-143.26E-142.527E-139.42E-15A, Argon40

7.776E-143.52E-132.17467E-131.1178E-12O2, Oxygen32

3.448E-123.01E-127.25867E-123.763E-12N2, CO, Nitrogen, Carbon Monoxide 28

1.251E-131.48E-132.0396E-128.40867E-14C2H3, Vinyl Radical27

1.308E-131.32E-139.26267E-135.92367E-14C2H2, Acetylene26

2.53E-112.21E-114.52767E-114.37733E-11H2O, Water18

7.547E-126.59E-121.29233E-119.50E-12OH, NH3, Water, Ammonia17

1.262E-121.14E-122.013E-122.36933E-12CH4, Methane16

8.936E-141.17E-136.25167E-131.12E-13CH3, Methyl Radical15

2.023E-131.59E-134.10667E-133.54E-13C, Carbon12

2.623E-112.70E-115.63567E-114.17E-11H2, Hydrogen2

Fingerprint(Amps)

Wax(Amps)

w/ O-Ring(Amps)

Baseline(Amps)

Atomic Mass Number

Taking DataMaterial Comparison

0.00E+00

1.00E-11

2.00E-11

3.00E-11

4.00E-11

5.00E-11

2 12 15 16 17 18 26 27 28 32 40Atomic Mass Unit (AMU)

Curr

ent (

Amps

)

BaselineO-ringWaxFingerprint

Rates of Decay

0.00E+00

2.00E-11

4.00E-11

6.00E-11

8.00E-11

1.00E-10

1.20E-10

1.40E-10

0 17 35 52 69 87 104 121

Time (minutes)

Cur

rent

(Am

ps)

MASS( 2 )MASS( 4 )MASS( 8 )MASS( 12 )MASS( 16 )MASS( 18 )MASS( 20 )MASS( 26 )MASS( 28 )MASS( 30 )MASS( 32 )MASS( 34 )MASS( 40 )MASS( 42 )MASS( 44 )MASS( 46 )MASS( 69 )MASS( 71 )

Applying The DataRates of Evacuation

This project is supported by a Research Experiences for Undergraduates (REU) supplement to the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under a cooperative agreement No. AST-9876783.

Acknowledgements

•Center For Adaptive Optics•LLNL Staff

Rick LevesqueJay AyersShannon WardNhan Nguyen