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  • Users: meekg
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  1. meekg

    Titanium Alloy Dimensional Stability

    We didn't think of that. If we can't hit the main modes, we can always weigh it down. Thanks.
  2. meekg

    Titanium Alloy Dimensional Stability

    ah.
  3. meekg

    Titanium Alloy Dimensional Stability

    yes - that's my thinking too. (Mine was a WAG - what does the S stand for?)
  4. meekg

    Titanium Alloy Dimensional Stability

    is it amorphous? (out of curiosity... we're not changing the material to glass right now... machining too complex, too late..)
  5. meekg

    Titanium Alloy Dimensional Stability

    Storage is -20C to 80C - nothing crasy. Forces are light. I'm worried about internal stresses. We'll be gping through several heat treatment cycles and other tricks. Since internal stresses are a function of (also) microstructure, choice of alloy can be important.
  6. meekg

    Titanium Alloy Dimensional Stability

    The fabrication tolerance is much looser than that. After fabrication, the piece is measured, and other calibration is performed. However, material creep in excess of 0.5um will take the instrument out of alignment. Ti was chosen for other reasons, among them strength-to-weight and non-magnetism.
  7. meekg

    Titanium Alloy Dimensional Stability

    I'm looking to choose a Ti alloy for a reference structure for a physics experiment. The structure is about 15"x6"x6" and is relatively heavily gutted by machining. The reference surfaces should not move more than 0.5um during 1 year. Temperature will be stable. We will heat treat as much as...
  8. meekg

    finishing Ti surfaces for UHV

    my omission. The target base pressure is 1E-7 Torr. The concern is about the total quantity absorbed in the walls (as opposed to the outgassing rate), since after initial pump-down to 1E-3 torr, only a getter is available to pump it down to and maintain to 1E-7 torr. I guess the question was...
  9. meekg

    finishing Ti surfaces for UHV

    Anyone familiar with best practices for finishing Ti surfaces for a UHV enclosure? Mechanical polishing to what level? any chemical or electro-chemical processes?
  10. meekg

    leak rates for pinch-off tubes

    Has to be non-magnetic. A hot-cathode gauge can be added, though will probably break on launch. (but will work during storage)
  11. meekg

    leak rates for pinch-off tubes

    ok - so I undrstand the the issue is not leak rate, but success (or failure) rates. With high volume applications, if there's a certain chance of the procedure not sealing, it translates directly into yield numbers. For this design, if the procedure fails, the experiment won't work, so it...
  12. meekg

    leak rates for pinch-off tubes

    I have a chamber that houses a getter pump and nothing else. The chamber is closed with a gate valve and a pinch-off tube. I plan to pump it down, activate the getter, seal the gate valve, and then look for leaks using an RGA. When satisfied, I'll close the pinch-off, and the whole assembly...
  13. meekg

    leak rates for pinch-off tubes

    I'm looking for numbers on leak rates using pinch-off tubes. Thanks, Ben.
  14. meekg

    structural UHV-compatible insulator

    I'm building a mechanism that should be compatible with a 1E-7 Torr environment. (The chamber is sealed, and is pumped by a Getter) There are a number of parts (e.g. a 4mm diameter by 15mm long push-rod, an M4 nut and washer) that need to be insulating. I'm looking for a few good materials...
  15. meekg

    Non-magnetic all-metal spring-energized vacuum C-seal

    I meant Beryllium... :)
  16. meekg

    Non-magnetic all-metal spring-energized vacuum C-seal

    I'm looking for a spring-energized seal, similar to the one referenced below, but with a non-magnetic spring (this one is Nickel based) http://www.helicoflex.com/catalogs/uhpuhv.pdf A Beryllium Copper or Phosphor Bronze spring will do the trick. The seal should be designed for 10-7 Torr Thanks.
  17. meekg

    Non-magnetic all-metal spring-energized vacuum C-seal

    I'm looking for a spring-energized seal, similar to the one referenced below, but with a non-magnetic spring (this one is Nickel based) http://www.helicoflex.com/catalogs/uhpuhv.pdf A Berrylium Copper or Phosphor Bronze spring will do the trick. The seal should be designed for 10-7 Torr...
  18. meekg

    Shakeable vacuum chamber

    I figured as much. Leak rates for gate valves are acceptable, but the valve may not stay sealed under the vibe conditions. I'm thinking the slide-type gate valves may be more resilient then the butterfly ones. Manually operated, probably. I'm looking in particular on information regarding the...
  19. meekg

    Shakeable vacuum chamber

    I'm trying to put together a vacuum chamber that is both rigid enough and light enough to be placed of a shake table. The operating pressure is 10-7 torr. Shake load peaks at 20g between 20hz and 60hz The actual experiment is relatively light, but we're trying to fit the chamber and...
  20. meekg

    calculate backflow (leak rate) through closed reed valve

    I'm looking to calculate the steady backflow (leak rate) through a closed reed valve, given the pressure difference and the viscosity of the fluid. For simplicity, the reed is circular with radius R, and is sitting over a hole with radius r. The reed remains flat and so contacts the flange over...

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