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Vacuum At LLO

Explore the principles of Residual Gas Analyzers (RGA) and their importance in detecting gases in low-pressure settings. Learn about leak detection methods and the operation of an interferometer in ultra-high vacuum conditions. Discover how helium is utilized for leak checking and get insights into RGA parts and calibration.

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Vacuum At LLO

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  1. Vacuum At LLO 2016 SURF Udochu, Ogbonnaya LIGO-T1600389

  2. Introduction • LIGO is a large physics experiment that detects and observes gravitational waves at a cosmic and astronomical level • An interferometer is a device that merges light sources to create interference • The interferometer is operated under ultra high vacuum (UHV) conditions, which is the pressure region less than 10-9 torr • An RGA allows one to know the chemical species involved in gas phase reactions

  3. Residual Gas Analyzers(RGA) • A Residual Gas Analyzer (RGA) allows the user to measure the gases present in low-pressure environments. • The principle of operation is the same for all RGA instruments: A small fraction of the gas molecules are ionized (positive) and the resulting ions are separated, detected and measured according to their molecular masses. www.scitek.com.au

  4. RGA Cont. • Parts of RGA • Filament/ Analyzer • Calibrated leak • O ring valve • All metal bellow valve • Baking of the RGA is to remove hydrocarbons and other impurities. • Baked at 150 degrees Celsius • Baked for 4 days

  5. Leak Detection • Helium is the best choice of tracer gas to find leaks • Due to its small atomic size helium passes easily through leaks. • Methods of Leak Checking are; • Vacuum Testing • Pressure Testing

  6. Leak Check of RGA • Leak checked after manifold was built • Used Helium leak detector • Used Vacuum Testing Method

  7. Pump Down(Roughing Down) • Processed used to take the pressures closer to vacuum pressures from atm. • Scroll pumps used • Used to get to molecular flow in a system

  8. Scans and Trends

  9. RGA pre-bake Scan

  10. References • https://www.ligo.caltech.edu/page/what-is-interferometer • https://www.ligo.caltech.edu/page/ligos-ifo • http://www.heliumleakdetection.net/Helium-Leak-Testing/what-is-helium-leak-detection.html

  11. Questions

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