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MICE Solenoid Magnetic Field Measurement

Ziptrack magnetic field mapping system MICE solenoid

Terry Hart, MICE CM 21, June 6, 2008

MICE Analysis Considerations

- MICE goal to measure emittance difference

(before and after cooling section) to one part in 10-4.

- Solenoid magnetic field must be mapped to enable this.
- Verify that 4 Tesla field is uniform in tracker region to 1%
- Map fringe field out to where it drops to 400 Gauss

(about 1 meter beyond ends)

- Fit measured points to functions consistent with Maxwell’s equations
- Understand effect of shields

Terry Hart, MICE CM 21, June 6, 2008

Spectrometer Solenoid Field Mapping

Ziptrack:

- Long metal beam passes through or perpendicular to magnet bore
- Special beam insert for MICE solenoid
- Ends translatable under computer control using LabView interface
- Cart w/carriage holding Hall probe rides on beamcontrolled & read out via LabView
- Position resolution: x,y – 10 µm; z – 10 µm
- Position repeatability:* x,y – 10µm; z – 10µm
- current performance goals – R&D in progress

Terry Hart, MICE CM 21, June 6, 2008

Rough Schedule

- Solenoid cool down underway
- Early July - Arrival of solenoid, shields
- August – Start of mapping
- Have to wait for MIPP Jolly Green Giant (JGG) magnet mapping currently scheduled for July
- Long setup makes going from MICE-JGG-MICE impractical

Terry Hart, MICE CM 21, June 6, 2008

Data Analysis Work to Do

- Add interactive MIPP event display to existing Ziptrack package
- Put useful FORTRAN routines in Ziptrack package

Want to make analysis of Ziptrack data easier through comfortable

interactive interface with data.

IIT graduate students Ben Freemire and Michael Wojcik to work on these.

Terry Hart, MICE CM 21, June 6, 2008

Considerations and Discussions

- Solenoid cold mass position accuracy
- Can determine cold mass position to better than 0.5 mm through external measurements
- Want to add survey targets to accessible magnet areas; would have to be done by FNAL or RAL
- Survey and alignment of Ziptrack system before and after field scans
- Measure roll, pitch, and yaw
- Moving cart along beam
- Moving beam to horizontal and vertical limits
- Measure offsets by moving cart in 27 point grid
- NIKHEF Hall probe
- Orthogonality imperfections calibrated away
- Level is at ‘a few times 10-4’ according to Frank Filthaut

Terry Hart, MICE CM 21, June 6, 2008

Field Measurement Configurations

- Map interior field
- No shields
- One coil on at a time
- All coils on
- With shields, all coils on
- ¼ nominal current densities
- ½ nominal current densities
- Nominal current densities
- 1.1 times nominal current densities
- Map fringe field with shields
- Ziptrack beam outside and perpendicular to solenoid

Terry Hart, MICE CM 21, June 6, 2008

ZipTrack beam

- Moves up/down, in and out of page

Solenoid/shields

Smaller beam insert for solenoid

- Holds carriage with 6 positions for Hall probe

- Carriage moves along beam insert

3

2

1

4

5

6

Cross section of beam insert with carriage

- Hall probe can be placed in any of 6 locations

- Most points accessible by multiple probe locations

Measure field inside solenoid

Red dots show reach of6 probes.

Blue dotsshow points to be mapped.

Grid spacing is 3 cm.

Measure grid every 3 cm along z.

Bold circles mapped with probe in 2

different locations

Measure field outside solenoid, downstream

Red dots show reach of6 probes.

Blue dotsshow points to be mapped.

Grid spacing is 3 cm.

Measure grid every 12 cm along z to

36 cm beyond spectrometer ends.

Bold circles mapped with probe in 2

different locations

Measure field outside solenoid, upstream

Red dots show reach of6 probes.

Blue dotsshow points to be mapped.

Grid spacing is 3 cm.

Measure grid every 12 cm along z to

36 cm beyond spectrometer ends.

Bold circles mapped with probe in 2

different locations

Measure field outside solenoid, ZipTrack beam outside solenoid

Blue dotsshow points to be mapped

(twice with probes in different locations).

Grid spacing is 12 cm.

Measure grid every 12 cm along z to

108 cm beyond spectrometer ends

All circles to be mapped with probe in

2 different locations

Bold circles also mapped with

ZipTrack beam inside solenoid

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