Relaxation Studies at UIUC Jacob Yoder February 7 th, 2008.

Relaxation Studies at UIUC

Jacob Yoder

February 7th, 2008

Illinois setup

Polarize 3He at room temperature with MEOP

3He refrigerator reaches 0.35 K

Measure polarization in lower cell by free induction decay

December Cool Down

Cooled down and attempted to run film burner during visit by George Seidel

Cooled cell to ~1.2 K with superfluid in cell Two main problems:

Heat load due to superfluid flow too high (300 W) Thermal link between 3He pot and cell inadequate

Addressing the Problems

Film burner not really necessary, replaced with copper “hat” to facilitate heat transfer

1 mm bore capillary extended up to 1 K anchor to slow film flow

Thermal link improved two ways: copper-copper connections made either by

welding or strong mechanical contact. Wire braid replaced with two .3” X .032” copper

strips Copper strips have good A/L, but are fairly stiff

Copper Hat

January Cool Down

Glass to copper link broke during LHe fill

Contraction of steel pipe during fill pulled on the joint and snapped the capillary

Copper Strips Replaced

1000 36 AWG wires (Alloy 110) used to make thermal link

8” long braids bent into C shape to give maximum flexibility

February (Ongoing) Cool Down Nothing broke Cell reached 0.68 K with ~ 0.1 mol 4He in cell Small FID signal in cold cell, but pumping cell

hasn’t been properly cleaned yet T1 measurement not possible without full

polarization in pumping cell T2 significantly longer than 50 ms

measurement interval

To Do

Continue T1 and T2 measurements after cleaning pumping cell in situ

Reduce length, increase cross section of braid to get ~ 10X improvement in A/L

Construct d-TPB cell All deuterated materials on hand