Straw Leak Rate Testing: Black Seamless Straw

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Straw Leak Rate TestingBlack Seamless Straw

• J.Popp, B.Christensen, C.Chen, W.Molzon
• University of California, Irvine

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Outline

• Equipment layout
• Protocol in brief design under review
• Results for one black seamless straw
• Discuss MECO vacuum load

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Equipment Layout

• Pump
• Ultimate pressure 10-4 torr
• Oil Filters
• Inlet Zeolite mineral
• Outlet paper
• Chamber
• Stainless steel
• R 1.0 cm, L 1 m
• Chamber heater
• T ? 300 C
• Cooling fans
• Hardware
• QF (NW) flanges, fittings, etc.
• Diaphragm type isolation valves
• Pirani pressure gauge
• Range 0.001 760 torr

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Empty Chamber Protocol, R0

• Chamber prep Bake chamber at T 300 C for 12
  hrs and cool.
• Measure empty chamber outgas rate, dP/dt.
• Open chamber to atmosphere and close.
• Measure outgas rate periodically.
• Open chamber and close.
• End test.
• Test duration lt 24 hours
• Yields 3 4 dP/dt measurements

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Results Empty Chamber

• Open and close chamber at t 0
• Data represents 5 R0 tests
• Before atmosphere 0.0014 torr/hr
• After 3 hrs 0.0022 torr/hr

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Open Straw Protocol R1

• Chamber prep Bake chamber at T 300 C for 12
  hrs and cool.
• Equilibrate straw at STP 24 hrs.
• Measure empty chamber outgas rate, dP/dt.
• Open chamber to atmosphere, insert straw, and
  close.
• Continue pumping.
• Measure dP/dt periodically.
• Open chamber, remove straw, and close.
• End test.
• Test duration 24 hrs
• yields 10 12 dP/dt measurements

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Closed Straw Protocol, R2

• Chamber prep Bake chamber at T 300 C for 12
  hrs and cool.
• Equilibrate straw at STP 24 hrs.
• Epoxy (high vacuum) straw ends closed and cure
  (24 hrs).
• Measure empty chamber outgas rate, dP/dt.
• Open chamber to atmosphere, insert straw, and
  close.
• Continue pumping.
• Measure dP/dt periodically.
• Open chamber, remove straw, and close.
• End test.
• Test duration 1 - 2 days
• yields 15 dP/dt measurements

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Results Raw Data Comparison

• Data represents
• - 5 R0 tests
• 3 R1 tests
• 5 R2 tests

Consistency Check

• Using PVnRT and Dt elapsed time

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Contribution to MECO Vacuum Load

• Convert rates to equivalent pumping speeds at
  10-4 torr, assuming
• - N ? 2848 straws
• - L 300 cm
• - Ls test straw length
• - Vchamber 373 cm3
• - PMECO ? 10-4 torr

1 cfm .472 l/s

• Improper handling
• Res. 1.0x10-3 torr
• Dt between P
• measurements too
• short
• Different personnel

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Conclusion

• Currently reviewing and finalizing protocol.
• Continue testing straws
• Wound carbon-loaded
• Others
• More black seamless
• Kapton/Copper
• MECO vacuum system
• 3 stages roots, booster, diffusion or
  turbomolecular pump
• Continue inquiries Lesker, BOC Edwards, Varian,
  Leybold,