Relaxation Studies at UIUC Jacob Yoder February 7 th, 2008

Illinois setup Polarize 3 He at room temperature with MEOP 3 He 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 3 He 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 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 T 1 measurement not possible without full polarization in pumping cell T 2 significantly longer than 50 ms measurement interval

To Do Continue T 1 and T 2 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