# Presentation: 310968

## Steve Williamson
UIUC

- Steve Williamson
- UIUC

## The 3He Services (He3S) Subsystem

- 6.6 Volume Displacement

- 6.11.1 Volume Displacement Interconnect Plumbing

## 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

**3****He Friendly Materials**

## 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. ...

## 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?

## 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?

- Good signal, reasonable T1, T2
- But signal decline and eventual loss after about 10 days.
- Leak? Outgassing?

- Glass Valve

## 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).

## Cooldown

- Cell cooled – early May
- New record low for 3He pot temperature

- D:1.64K

- C:0.82K

- B:0.55K

- A:1.36K

- E:0.33K

- F:0.31K

- 0.4K anchor

- 1.2K anchor

- 3He evaporated

- Turbo Off

## 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.

## 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

## 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

## Results

- Polarization rotation frequency  = 3HeBx
- An additional high-frequency field (dressing field) can modify the effective moment.

- 30% Change in effective magnetic moment