1 / 10

Diffusive Transport of 3 He in the EDM Experiment

Diffusive Transport of 3 He in the EDM Experiment. Steve Lamoreaux. Basic Idea. Superfluid Helium at sufficiently low “looks like” a perfect mechanical vacuum We are working with low 3 He density so 3 He- 3 He collisions will not hinder diffusive/ballistic flow

burian
Download Presentation

Diffusive Transport of 3 He in the EDM Experiment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Diffusive Transport of 3He in the EDM Experiment Steve Lamoreaux

  2. Basic Idea • Superfluid Helium at sufficiently low “looks like” a perfect mechanical vacuum • We are working with low 3He density so 3He-3He collisions will not hinder diffusive/ballistic flow • Flow in pipes: Knudsen’s formula

  3. What W do we need? • We have two cells, 10000 cm3 volume. We need an emptying time constant of about 50 seconds (4 time constants to get to 98% clean) • So W=1/(200 cm3/sec) • m=2.2 m3 • For 50 cm length, T=0.3 K, d=2.3 cm • For 100 cm length, d=2.9 cm

  4. What is the time constant to empty the cell through a 2 cm diameter hole? For v= 50 m/s, A=3.14 cm2, V=10000 cm3 t= 2.5 sec Or, for 10000 sec, A=10-3 cm2 This is a 1 micron gap around a 6 cm circumference

  5. Overall Scheme Collection Volume Helium Level Cell valve Selection Valve charcoal Exp. Cells

  6. The Pressurization Problem • What if we have to run with the superfluid pressurized to get a high dielectric strength? • Then we can’t have a free liquid surface • Possible to have the ‘main bath’ pressurized, the cells at low pressure?

  7. Gradient Requirements Holding Cells: See hreq.pdf for details

  8. Charcoal Conveyor Belt Charcoal coated “conveyor belt” periodically moves charcoal to hot region for cleaning Purification volume

  9. Electrical Detection of Scintillations I+ 5000 ion pairs??? per capture I- About 1 pA if collected in 1 msec; 1 fA/rtHz amp provides s/n of 25

  10. ~ 2.0 K Ion Mobility in SFHe E > 104 V/cm ions detach from vortices

More Related