UIUC Test System (Beck, Chandler, Hertzog, Kammel, Newman, Peng, Sharp, Williamson, Yoder; Blackburn, Kenyon, Thorsland)

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UIUC Test System(Beck, Chandler, Hertzog,
Kammel, Newman, Peng, Sharp, Williamson,
YoderBlackburn, Kenyon, Thorsland)

• Goal Provide cooled environment to test
  experiment components at operating temperature
• ½ scale cells
• ¼ scale magnet assemblies

• Two stage cooling
• pumped L4He cools to T 1.3 K, liquifies 3He
• pumped L3He cools to T lt 0.5 K
• experimental platform on L3He vessel
• main advantage is short turnaround time

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3He Refrigerator LHe Vessels
Vacuum flange
L4He pot (1.3 K)
L3He pot (0.5 K)
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3He Refrigerator First test

• First cooldown Troom to 0.54 K in 11 hours

Start L3He forepump
Start L3He turbopump
L3He vessel empty

• maximum 6 h at 0.5 K valve on turbo pump?
• replacing instrumentation leads with
  superconductor to reduce heat leak
• preparing for first cooldown with glass cell
• SQUID noise test?

4
UIUC Polarized 3He Development

• Goal test trelax with dTPB surface at operating
  temp
• Metastability optical pumping
• commission new diode laser system at 1083 nm

23p0
23p1
23p2
4He
Flourescence signal (V)
Laser Temperature (oC)

• splitting of lines gives dl/dT 0.076 nm/oC
  (spec 0.08 nm/oC )
• width of lines is 2.8 GHz FWHM consistent with
  experience

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UIUC Polarized 3He Development

• Metastability optical pumping
• 3He flourescence seen? ? gas may be
  contaminated

23p1/2
23p0
23p1
23p2
C8?
1083.031 nm C9
3He (3/30)
1083.057 nm C8
23p1/2
23p3/2
23p3/2
23p5/2
23s1/2
23s3/2
3He excited states

• preparing NMR system and 668 nm polarimeter for
  room temperature test

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UIUC Polarized 3He Development

• Glassware and holding field for cryostat
• start with simple double cell system to reproduce
  Duke 4 K results

• 5 G holding field with minimum gradients (Hayden
  design)
• 13 coils uniform field (ltdB2gt1/2/B 10-4)
• volume 7 cm dia x 2.8 m
• completing coil shunts

dBz,RMS/Bz
z (radii)
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UIUC Polarized 3He Development

• Circulating system
• a la Candela, Hayden Nacher
• force 3He to circulate past pumping cell
• aid entrainment of 3He into L4He with HEVAC
  effect
• detailed model developed
• measure relaxation
• test SQUID pickup with very low concentrations?

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nEDM Cryostat Layout E

• Elements

D. Beck 4 Jun 03
Variable capacitor
300 mK vessel (incl. graphite HV plane, BNx or
Gd paint neutron shielding)
1.79 m o.d.
Possible 1K shield
Inner coil for Brf, flip
y
Outer coil for Brf, flip
z
B0
4K vessel
x
Coil for B0 field
Brf
Metglas (inner) ferromagnetic shield
Superconducting shield
4K vessel
Mu-metal (outer) ferromagnetic shield
Liquid nitrogen shield
Cryostat wall
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nEDM Cryostat Layout E

• Elements

D. Beck 4 Jun 03
Variable capacitor
300 mK vessel (incl. graphite HV plane, BNx or
Gd paint neutron shielding)
1.79 m o.d.
Possible 1K shield
y
Inner coil for Brf, flip
Outer coil for Brf, flip
x, B0
z
4K vessel
Brf
Coil for B0 field
Metglas (inner) ferromagnetic shield
Superconducting shield
3.06 m long
4K vessel
Mu-metal (outer) ferromagnetic shield
Liquid nitrogen shield
Cryostat wall
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Dressed Spins Principle

• interacting system of magnetic moment and photons
• effective moment is reduced (dressed)
• precession rate is reduced depending on bare
  magnetic moment

• adjust dressing parameter, x, to critical value,
  given by

• field for wrf 2p1kHz is 0.41 G

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Dressed Spins Practice

• use cosq coils for bothB0 and Brf
• use 2 opposed cosq coils for Brf
• reduces power dissipatedin ferromagnetic shield
• rf frequency
• because for small changes in B0, dE (w0/wrf)2
  dw0,
• wrf 100 w0, or wrf 2p ? 1 kHz
• also use Brf coil for p/2 pulse

y
Inner coil for Brf, flip
Outer coil for Brf, flip
z
B0
x
Coil for B0 field
Brf
Metglas (inner) ferromagnetic shield
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Cosq Coils
Central field 0.41 G
Number of turns 20
Inner radius 0.45 m
Inner length 2.5 m

• note ends not shaped (for these results) to do

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Outer Cosq Coil

• minimum power dissipated in shield soft
  function of outer coil size
• tshield 10 layers Metglas 2705M

200 integration points
450 integration points
1800 integration points
Dissipated Power (W)
Outer radius (m)
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Field Distributions

• For ri 0.45 m (4.5 A), ro 0.6 m (-2.4 A),
  rshield 0.66 m