DHB, nEDM Collab. Mtg, 15/16 Apr 04
UIUC Test System(Beck, Chandler, Hertzog, Kammel, Newman, Peng, Sharp, Williamson, Yoder;
Blackburn, 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 < 0.5 K- experimental “platform” on L3He
vessel- main advantage is short
turnaround time
3He gas storage
LHe Dewar
DHB, nEDM Collab. Mtg, 15/16 Apr 04
3He Refrigerator: LHe Vessels
3He gas storage
L4He pot (1.3 K)
L3He pot (0.5 K)
Vacuum flange
DHB, nEDM Collab. Mtg, 15/16 Apr 04
- 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?
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
22:19 22:33 22:48 23:02 23:16 23:31 23:45 0:00 0:14
Time (20-21 Feb 04)
T (
K)
p (
mT
)
T_3He (K)T_4He (K)p_3He (mTorr)
3He Refrigerator: First test
Start L4He pump
Start L3He forepump
Start L3He turbopump
L3He vesselempty
• First cooldown: Troom to 0.54 K in 11 hours
DHB, nEDM Collab. Mtg, 15/16 Apr 04
UIUC: Polarized 3He DevelopmentGoal: test trelax with dTPB surface at operating temp
I. Metastability optical pumping- commission new diode laser system at 1083 nm
2s0
23s1
23p2
23p1
23p0
1083.034 nm
1083.025 nm
1082.908 nm
4He excited states
23p0 23p1 23p2
- splitting of lines gives d/dT = 0.076 nm/oC (spec 0.08 nm/oC )- width of lines is 2.8 GHz FWHM: consistent with experience
30 31 32 33 34
Laser Temperature (oC)
Flo
ures
cenc
e si
gnal
(V
)
0.09
0.10
0.114He
DHB, nEDM Collab. Mtg, 15/16 Apr 04
- preparing NMR system and 668 nm polarimeter for room temperature test
UIUC: Polarized 3He Development
I. Metastability optical pumping- 3He flourescence – seen? → gas may be contaminated
23s3/2
23p3/2
23p1/2
23p1/2
1083.031 nm“C9”
3He excited states
23p0 23p1 23p2
1082.8 1083.0 1083.2 1083.4Laser Wavelength (nm)
3He (3/30)
Flo
ures
cenc
e si
gnal
(V
)
0.069
0.070
0.071
0.072
0.073
23s1/2
23p3/2
23p5/2
1083.057 nm“C8”
C8?
DHB, nEDM Collab. Mtg, 15/16 Apr 04
UIUC: Polarized 3He Development
II. 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 (B21/2/B10-4
- volume ~ 7 cm dia x 2.8 m
- completing coil shunts
Pumping cell
Vacuum seal
Mirror
The Quantity Minimized For RMS Optimization
0
0.00002
0.00004
0.00006
0.00008
0.0001
0.00012
0.00014
-5.00 -4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00 5.00
Z (radii)
Bz,
RM
S/B
z
z (radii)
DHB, nEDM Collab. Mtg, 15/16 Apr 04
UIUC: Polarized 3He Development
III. 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?
nEDM Cryostat Layout E
300 mK vessel (incl. graphite HV plane, BNx or Gd paint neutron shielding)
ElementsVariable capacitor
Possible 1K shield
Inner coil for Brf, flip
Outer coil for Brf, flip
4K vessel
Coil for B0 field
Metglas (inner) ferromagnetic shield
Superconducting shield
4K vessel
Mu-metal (outer) ferromagnetic shield
Liquid nitrogen shield
Cryostat wall
y
xzB0
Brf
1.79 m o.d.
D. Beck
4 Jun 03
nEDM Cryostat Layout EElements
300 mK vessel (incl. graphite HV plane, BNx or Gd paint neutron shielding)
Variable capacitor
Possible 1K shield
Inner coil for Brf, flip
Outer coil for Brf, flip
4K vessel
Coil for B0 field
Metglas (inner) ferromagnetic shield
Superconducting shield
4K vessel
Mu-metal (outer) ferromagnetic shield
Liquid nitrogen shield
Cryostat wall
y
x, B0 z
Brf
D. Beck
4 Jun 03
1.79 m o.d.
3.06 m long
DHB, nEDM Collab. Mtg, 15/16 Apr 04
Dressed Spins: Principle
• interacting system of magnetic moment and photons- effective moment is reduced (“dressed”)- precession rate is reduced depending on “bare” magnetic
moment
barerf
rf
baredressed
Bx
xJ
0
• adjust dressing parameter, x, to critical value, given by
n
cc xJxJ
3
00
for
→ field for rf = 2*1kHz is 0.41 G
DHB, nEDM Collab. Mtg, 15/16 Apr 04
Dressed Spins: Practice• use cos coils for both
B0 and Brf
- use 2 opposed cos coils for Brf
- reduces power dissipatedin ferromagnetic shield
- “rf ” frequency- because for small
changes in B0, E ~ (0/rf)2 0,
→ rf ~ 100 0, or rf ~ 2 1 kHz
- also use Brf coil for /2 pulse
Inner coil for Brf, flip
Outer coil for Brf, flip
Coil for B0 field
y
xzB0
Brf
Metglas (inner) ferromagnetic shield
Cos CoilsCentral field 0.41 G
Number of turns 20
Inner radius 0.45 m
Inner length 2.5 m
1
0
1
z0.50
0.5x
0.40.2
00.20.4
y
1
0
1
z0.40.2
00.20.4
y
- note: ends not shaped (for these results) – to do
0.5 0.55 0.6 0.65
0.5
1
1.5
2
2.5
3
3.5
4
Outer Cos Coil• minimum power dissipated in shield “soft” function of outer coil
size- tshield = 10 layers Metglas 2705M
Dis
sipa
ted
Pow
er (
W)
Inner coil Shield
Outer radius (m)
1800 integration points450 integration points200 integration points
DHB, nEDM Collab. Mtg, 15/16 Apr 04
Field Distributions
• For ri = 0.45 m (4.5 A), ro = 0.6 m (-2.4 A), rshield = 0.66 m
0.02 0.04 0.06 0.08 0.1 0.12 0.14
0.993
0.994
0.995
0.996
0.997
0.998
0.999
Brf (
y)/B
rf,0 y (m)
Brf (
y) (
G)
0.1 0.2 0.3 0.4 0.5 0.60.15
0.250.3
0.350.4
0.02 0.04 0.06 0.08 0.1 0.12 0.14
1.0005
1.001
1.0015
1.002
1.0025
1.003
Brf (
x)/B
rf,0
x (m)
Brf (
x) (
G)
0.1 0.2 0.3 0.4 0.5 0.6
0.80.60.40.2
0.20.4