Target Update – Mico Meeting Monday 21 st April 2008 General

1. Target Update – Mico Meeting Monday 21st April 2008 • General • Expect to obtain new coils for stators anytime • New Shafts at RAL for metrology. Will be back at Sheffield soon (This week?) • Other?

2. Thermal Tests • 24 coils in each stator – In the ‘current’ design there are 6 copper shims (25um) between each pair of coils to extract the heat from the coils. The heat flows from the shims into a copper water cooled Jacket where it is extracted. All of the heat extraction components have to be earthed. • A metallic bore that runs through the centre of all the coils and separates the stator from the ISIS vacuum is also earthed • Last two ‘demonstrator’ stators failed due to electrical breakdown between the coils and earth. Cause is due to insufficient insulation between live and earthed parts. • We built a new test stator out of the coils we rescued from the two damaged stators.

3. New stator • We built in two ‘parts’ to test two different materials. Bottom half of the stator we used a pair of Mica washers to separate the coils from the copper. shims – Mica 50um Thick, so we could only use 2 copper shims • Top half of the stator we used Kapton to separate the coils from the copper shims – Kapton 25um Thick, so we could only use 4 copper shims. • Centre Bore Insulated with several wraps of 25um Kapton. • All coils Insulation Tested to > 1000 Volts. • Put pairs of T/C in on both sides of insulation. Mica Coils Kapton Copper Shims Top half of Stator Bottom half of Stator

4. Coils and Coil Varnish are both rated to a maximum of 200 deg C. • Kapton Rated to 400 deg C • Exact Mica Rating is unknown but will be >>200 deg C • T/C connected to: • Between coils 6/7 (Kapton Insulation) • Between coils 12/13 (Kapton/ Mica Interface) • Between coils 18/19 (Mica Insulation) • Water In • Water Out • Actuator has been run for about 45 minutes • Old Actuator use to run at about 65-70 deg C with water temp in of ~15 deg C

5. Coil / Insulation Temp MICA T/C Insulation / Shim Temp ~0.5 Hz ~1.0 Hz Cooling Water In

6. Coil / Insulation Temp KAPTON T/C Insulation / Shim Temp ~0.5 Hz ~1.0 Hz Cooling Water In

7. MICA & KAPTON Results Combined ~0.5 Hz ~1.0 Hz

8. Conclusions • Adding Insulation Increases the operating temperature of the stator (as expected!) but is within specification of the components • The added Insulation also appears to provides adequate electrical protection. (Insulation tested to >1KV) Normal running is at ~200V with spikes up to ~600V expected. • Only done a single short run! We would like to run the actuator for an extended period to show long term reliability. • Water temperature at ISIS is ~30 deg C as opposed to the ~12 deg C we used. Expect operating temperature at ISIS to be even higher than illustrated here. • Higher temperature may impact upon the life of the permanent magnets. This is currently unknown • If running at a higher temperature does reduce the life of magnets then the target can be run at a slower rate – but clearly impacts upon MICE running. If this is the case then future development could reduce power consumption of actuator but would need significant development. (Not for now!)