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Vacuum tests

Vacuum tests. Problem description Valve presentation Test setup Measurements & Results Conclusions. Problem description. Secondary vacuum. Separated primary and secondary vacuum to obtain good ring vacuum Thin foil required because of multiple scattering

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Vacuum tests

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  1. Vacuum tests • Problem description • Valve presentation • Test setup • Measurements & Results • Conclusions

  2. Problem description Secondary vacuum • Separated primary and secondary vacuum to obtain good ring vacuum • Thin foil required because of multiple scattering • Intrinsically safe solution is desired Thin foil Electronics, cables, etc. Primary vacuum

  3. Valve presentation • Valves that react to differential pressure • Electric/Pneumatic, but… • Fail-safe solution required • Proposal: Gravity controlled valve

  4. Test setup • Leak rate during normal operation (with/without pump) • Preliminary: • Dynamic response to sudden pressure changes (leaks) • System behavior during pump down Removed picture of vacuum test setup

  5. Test setup (2) Sander Klous 24-11-2000

  6. Measurements & Results • Conductance (H2O): • 10-3 liter/sec without dedicated pump • 10-5 liter/sec with dedicated pump • Expected secondary vacuum pressure: 10-4 mbar This would result in 10-9 mbar l/s leak-rate Pumping slots

  7. Measurements & Results (2) • Dynamic response • Maximum differential pressure over the valve is 6 mbar • Measurement is dominated by the bellow configuration (see picture) • More realistic measurements are required with faster gauges Removed picture of tandem (gravity-controlled) valves

  8. Measurements & Results(3) Secondary vacuum • Pump down time • Conductance between primary and secondary vacuum: Bellows (L = 1 m, d = 20 mm) • Maximum pressures in range of the gauges: 500 mbar, calibrated with a baratron. • 3 hours to around 1 mbar (p = 9 mbar at 500 mbar) • 3 hours to 10-5 mbar Bellow Primary vacuum Restriction Valve 2 Valve 1 Primary pump Turbo pump

  9. Conclusions • All measurements indicate the gravity controlled valve can work • For the correct dynamic pressure analysis a more realistic setup is required

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