dhb, nedm collab. mtg, 15/16 apr 04 uiuc test system (beck, chandler, hertzog, kammel, newman, peng,...

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


3He Refrigerator: LHe Vessels

3He gas storage

L4He pot (1.3 K)

L3He pot (0.5 K)

Vacuum flange


- 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


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


- 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?



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)



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



4K vessel

Coil for B0 field


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


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


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



Coil for B0 field

y

xzB0

Brf


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


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

dhb, nedm collab. mtg, 15/16 apr 04 uiuc test system (beck, chandler, hertzog, kammel, newman, peng,...

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