nEDM Collaboration Meeting, May 25-26, He Relaxation Steve Williamson UIUC

nEDM Collaboration Meeting, May 25-26, The 3 He Services (He3S) Subsystem 6.6 Volume Displacement Volume Displacement Interconnect Plumbing

nEDM Collaboration Meeting, May 25-26, The 3 He Services (He3S) Subsystem 6.6 Volume Displacement Volume Displacement Interconnect Plumbing Cell Isolation (V1) Valve Actuators and Interfaces 6.5 Purifier Purifier isolation (V6) Valves 6.1 3He Atomic Beam Source (ABS) 6.2 ABS Interface 6.3 Polarized 3He Collection System 6.8 Pressurizer Purifier Control (V5) Valve Collection Isolation (V4) Valve Pressurizer Standoff (V3) Valve Pressurizer Isolation (V2) Valve Collection/ Purifier Interconnect Plumbing Pressurizer/Cell Interconnect Plumbing 3 He Friendly Materials

nEDM Collaboration Meeting, May 25-26, What Materials are 3 He 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, 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,  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, 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 3 He).

nEDM Collaboration Meeting, May 25-26, Cooldown  Cell cooled – early May  New record low for 3 He 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 3 He evaporated Turbo Off

nEDM Collaboration Meeting, May 25-26, 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, 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, He Dressed Spin Studies  3 He dressed-spin effect observed at LANL with ABS beam. Now try in a cell.  Normal “optical NMR”:  Once the cell is polarized, B x 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 B x

nEDM Collaboration Meeting, May 25-26, Results  Polarization rotation frequency  =  3He B x  An additional high-frequency field (dressing field) can modify the effective moment. 30% Change in effective magnetic moment