1

Preparation for the 3He Injection Test

05/2008 Duke

D. Dutta*, H. Gao, M. Busch, Q. Ye, X. Qian, W.

Zheng, X. Zhu (Duke University)

ASU, BU, Caltech, LANL, MIT, MSU, NCSU, SFU

And others in nEDM collaboration

*Mississippi State University.

2

Outline

• Introduction• Safety • Magnets• Glassware• Cryogenics • pNMR• Summary

3

Dilutionrefrigerator

tricoil

Helium bath vesselHelium gasFilling pipe

To ABS 50K

4k

Film burner

Helium @0.35k

Pyrex cell

Heat exchanger

1.3k

0.7k

0.24k

4

Update• Problem with jacket pyrex cell

– Seal <1K and safety when boil off

• Cool the cell with OFHC copper foil

Measurement cell @.35K

Copper foil to cool the cell

DR MX at 0.24K

To ABS

DR 1K pot

Cs ring

Filling pipe for L-He

5

Safety I: Boil off of LHe within pyrex cell

• 23.58 cc LHe within pyrex cell• boil off rate: ~1 mol/s

– Heat rate: 60000 W/m2, in worst case• Effuse through ABS beamline, pressure

difference ~25.2 Pa– Gas density at 273 K and 1 atm – Id: 0.04 m, L=1.0 m– Flow velocity: 17.8 m/s– Reynold constant: Re = 6842.4– Resistance coefficient, K=0.9

– From T. Ito and Applied Fluid Dynamics Handbook

– Effect of thermal baffles not included

6

Protection for ABS vacuum system

Vacuum

Gauge and

pump

ABS low Beam lin

e

Gate

valve

ABS

Non-magnetic

Pneumatic

valve

Rupture disk/

Pressure re

lief

If P>10-5 torrActivate the Pneumatic valve

• A pneumatic valve to protect ABS beamline

• A rupture disc for pressure relief

5”

5”

2”

2”

Catastrophic Boil off

7

Safety II: boil off of LHe within Tricoil can

• Siphon pipe to fill LHe into tricoil can

• Pipe for safety venting– Heat rate: 2 kW/m2

– Pressure drop: 5.5 psi• Gas

density@50K,1atm– By J. Long

• Venting velocity: 97m/s

• 1.375” ID, 45” length• Reynold number:

5.7x105

• resistant coefficient: 0.49

– Rupture disc@4K• Avoiding Taconis

resonance

Siphon pipe

Vacuumvent pipe

8

Safety III: No problem with superconductor

quench • Energy within tri-coil:

714.15J– Energy within transport

solenoid coil: 6.3mJ, negligible

• Quench will evaporate 2.84 liter of He gas at 4K

– Amount to 8.67 mol He• The volume of tri-coil

container: ~17 liter – Bottom :14 lit, top: 3 lit.

• The pressure will increase by <50%

– Assume space of coil : 7 lit• Acceptible to tricoil vessel

• FEA analysis done by E. Iholff

Pressure<2atm

9

Tricoil Magnet system

• Tricoil current lead– 300K to 50K: copper wire, #11 AWG– 50K to 4K: silver wire with

filaments of HTS ceramic (BiPbSrCaCuO)

• Low thermal conductivity– From American Superconductor

• Solder with eutectic InAg with no flux

10

Cryogenics• Heat load to DR mix:~ 5mW

– ~2.5mW from superfluid film burner

– By G. Seidel

– 0.5mW for pNMR and support

– 1.1mW for gas introduction tube

– 13.8mW cooling power @0.24K

• Cs ring to slow down superfluid flow rate

– Torch to chase Cs vapor– Dry ice to condense Cs

effectively • Sealing test undergoing

– Pyrex to copper adapter– After fail and try, kapton

gasket seals well with copper flange

Kapton gasket

Epoxy2850GT

Cs ringMade by dry ice

11

pNMR system

• Faraday cage– Two tunable capacitor – Resonant coil– Copper enclosure@1.3K

• Semi-rigid coax– Center: Ag coated BeCu– Dielectric: teflon– Sheath: BeCu

• From D. G. Crabb, UVA

• Weakly magnetized SS

• Tosca simulation by Tim, ASU

Faraday cage

12

Wire connection for temperature sensors

• Thermometer leads: twisted pair , Phosphor bronze– Suggested by S. Williamson

• Noninductive winding scheme– Minimizing induced voltage due magnetic flux

change• Voltage wires and current wires thermal

anchor separately• Wire lengths for thermal anchoring (300K

to 4K)– 1.1cm for #32 AWG – 3.8cm for #24 AWG Heat

sinkpost

13

Summary

Design work is almost done, ready for fabrication and assembling. Injection test will be ready in

the end of July

14

Thanks!