steve williamson uiuc
DESCRIPTION
3He Relaxation. Steve Williamson UIUC. 6.2 ABS Interface. 6.5 Purifier. 6.1 3He Atomic Beam Source (ABS). 6.3 Polarized 3He Collection System. 6.10.1 Cell Isolation (V1) Valve Actuators and Interfaces. 6.11.3 Pressurizer/Cell Interconnect Plumbing. 6.10.6 Purifier isolation (V6) Valves. - PowerPoint PPT PresentationTRANSCRIPT
nEDM Collaboration Meeting, May 25-26, 2006
3He Relaxation
Steve WilliamsonUIUC
nEDM Collaboration Meeting, May 25-26, 20062
The 3He Services (He3S) Subsystem
6.6 Volume Displacement
6.11.1 Volume Displacement Interconnect
Plumbing
6.10.1 Cell Isolation (V1)
Valve Actuators and Interfaces
6.5 Purifier
6.10.6 Purifier isolation (V6)
Valves
6.1 3He Atomic Beam Source
(ABS)
6.2 ABS Interface
6.3 Polarized 3He
Collection System
6.8 Pressurizer
6.10.5 Purifier
Control (V5) Valve
6.10.4 Collection
Isolation (V4) Valve
6.10.3 Pressurizer
Standoff (V3) Valve
6.10.2 Pressurizer
Isolation (V2) Valve
6.11.2 Collection/
Purifier Interconnect
Plumbing
6.11.3 Pressurizer/Cell
Interconnect Plumbing
nEDM Collaboration Meeting, May 25-26, 20063
The 3He Services (He3S) Subsystem
6.6 Volume Displacement
6.11.1 Volume Displacement Interconnect
Plumbing
6.10.1 Cell Isolation (V1)
Valve Actuators and Interfaces
6.5 Purifier
6.10.6 Purifier isolation (V6)
Valves
6.1 3He Atomic Beam Source
(ABS)
6.2 ABS Interface
6.3 Polarized 3He
Collection System
6.8 Pressurizer
6.10.5 Purifier
Control (V5) Valve
6.10.4 Collection
Isolation (V4) Valve
6.10.3 Pressurizer
Standoff (V3) Valve
6.10.2 Pressurizer
Isolation (V2) Valve
6.11.2 Collection/
Purifier Interconnect
Plumbing
6.11.3 Pressurizer/Cell
Interconnect Plumbing
3He Friendly Materials
nEDM Collaboration Meeting, May 25-26, 20064
What Materials are 3He Friendly? We have focused on dTPB in the cell But for seals, interconnections, and valves, we
also need to characterize other materials. Nylon – Big CTE, good for seals Teflon – Remains ductile at low temperature, good for
valve bellows Kapton – proposed for seals dStyrene – cheaper than dTPB coating, for pipes? DryFilm – Could be used to coat unfriendly materials Composite Carbon or G10 – 1200 l volume end-caps etc. etc. …
nEDM Collaboration Meeting, May 25-26, 20065
An Example
Copper
Acrylic
Nylon(LARGE CTE)
H-gasket Seals on
outside on cool-down
H-gasket Seals on inside on warm-up
But is Nylon 3He Friendly?
nEDM Collaboration Meeting, May 25-26, 20066
Single cell with valve like that used in Duke experiments.
Good signal, reasonable T1, T2 But signal decline and eventual loss
after about 10 days.
Leak? Outgassing?
Glass Valve
Good Bad
nEDM Collaboration Meeting, May 25-26, 20067
Double Cell: Install in Cryostat 2.8 m double cell Glass thermal links:
Few hundred strands of ~ 32 gauge Cu wire twisted under tension around glass. Links at 4, 1.2, 0.4 K Thermal contact improved with Apiezon N vacuum grease.
Just vacuum, (no 3He).
nEDM Collaboration Meeting, May 25-26, 20068
Cooldown Cell cooled – early May New record low for 3He
pot temperature
D:1.64K
C:0.82K
B:0.55K
A:1.36KE:0.33K
F:0.31K
0.4K anchor
1.2K anchor
3 He
evap
orat
ed
Turbo O
ff
nEDM Collaboration Meeting, May 25-26, 20069
Cooldown Glass temperature distribution seems odd.
Poor thermal contact of lowest sensor? More effective radiation heating of bottom
from IVV? “Baked Potato” effect?
Improve thermal connection to glass using Cu foil, GE varnish
smoothly, despite departure of refrigerator designer/operator for greener pastures.
nEDM Collaboration Meeting, May 25-26, 200610
Next Steps Solve valve contamination problem
Build new 3 m double cell with valves Valve for pumping Valve for filling In-line valve to release Polarized 3He into
measurement cell Measure NMR at 300 K with “standard” coils Build new flip and pickup coils for cryostat Cooldown and measure NMR at 0.3K Cold test with 3 m double cell (glass) Cold test with 3 m double cell (acrylic cold cell)
Room temperature testing (relaxation) of key materials acrylic Cu-Ni? Si-Bronze?
Cold testing of materials
Fill
Vacuum
Release
Pump Cell
Measure.Cell
nEDM Collaboration Meeting, May 25-26, 200611
3He Dressed Spin Studies 3He dressed-spin
effect observed at LANL with ABS beam. Now try in a cell.
Normal “optical NMR”: Once the cell is
polarized, Bx is applied at the Larmor frequency to rotate the ensemble polarization
Flourescence optical signal intensity varies with z-component of the polarization.
Modulation reveals the spin precession about Bx
nEDM Collaboration Meeting, May 25-26, 200612
Results Polarization rotation frequency = 3HeBx
An additional high-frequency field (dressing field) can modify the effective moment.
30% Change in effective magnetic moment