Cryostat and Magnet Status Report UIUC

EDM Collaboration Meeting

LANL

June 20, 2005

Summary

• Cryostat Goals• Progress• To Do

• Magnet Goals• Current Field

Measurements• Future Field

Measurements

Crysostat goals

• Ensure no cryostat materials spoil magnetic field uniformity.

• Minimize heat load.

Cryostat Progress

• Large 3He cell constructed, cleaned and purity-tested with a spectrometer

• Silicon-Bronze selected as replacement for inner vacuum vessel flange.

• Indium seals selected to replace conflat seals

Long 3He cell

Cryostat to Do

• Replace dewar (currently being ordered)

• Completely rework outside plumbing

• Build new inner vacuum vessel

• Pumping lines (3He and 4He) must be replaced with thinner walled steel to reduce heat load

• Test/Install large 3He cell

Magnet Design

• Ensure B/B <5E-5 cm-1 over VOI by optimizing coil currents and spacings.

• Coil currents determined by number of windings and shunt resistors.

• Coil diameters are identical.

First measurement with Gantry

•First attempted to map coils with “gantry” from G0 project

•Long term variation of order 0.1 G in the probe offsets rendered this data useless for determining gradient information

Current center field measurement

-0.08-0.07-0.06-0.05-0.04-0.03-0.02-0.01

00.010.02

0 50 100 150 200 250 300 350

Position (cm)

Fie

ld D

evia

tio

n (

G)

Deviation from 5 Gauss, measured with Fluxgate magnetometer

Current field measurement• Several gradients appear in the data, one of

order 2*10-5 cm-1 and one of order 10-4 cm-1.• Location of change in gradient value

corresponds with junction of two PVC tubes used to position fluxgate.

• Fluxgate has time dependences that could not be completely removed.

• More accurate positioning and a more precise field measurement are necessary.

Next field uniformity measurement

• ~0.1 mG magneto-resistive sensor purchased

• To be mounted on boom of G0 mapper