Target Status Report

1. Target Status Report Chris Booth Sheffield 4th June 2008

2. Status at February CM: • Target installed in ISIS • Operated for few hundred pulses (without beam) • Demonstrator system almost ready for installation in R78 • Problem discovered with stepper motor • Could not reliably raise or lower target frame Since then (in brief): • Wiring faulton stepper motor discovered and fixed (thanks Steve Griffiths!) • Electrical problems with demonstrator actuators • Successful runs of target in ISIS – particles in beam-line! University of Sheffield

3. Demonstrator Target • Required by ISIS to run ahead of installed actuator (3× no. of pulses) • Actuator assembled, tested in Sheffield • 50,000 pulses (14 hours) ok • But cooling jacket not earthed! • Arrived RAL R78 13th February • Failed after few hundred pulses • Coil shorted to ground, burnt out. • Returned to Sheffield & dismantled • Evidence of breakdown from coil to cooling jacket • See photos • Note: fault would not have been seen in Sheffield test due to missing earth connection. University of Sheffield

4. Demonstrator Target (continued) • Assumed to be one-off coil fault. • Insufficient new coils to build new stator from scratch • Coil assembly salvaged from actuator removed from ISIS in January • This had run in November 2006, at 35 V • Taken to Daresbury for re-welding of seal, then direct to RAL on 19th February. • Note! Untested since reassembly. • This actuator also failed after very few pulses. • Short on inside of coil to earthed central vacuum tube. • See photos. University of Sheffield

5. Demonstrator Rebuild Programme • Visits to coil manufacturers • Improved insulation (coils double-dipped in resin). • Insulation-tested after assembly by manufacturers to 1 kV. • Tests in Sheffield with mica and kapton insulation • New stators under construction, with kapton sleeve over vacuum pipe, kapton separators between coils and cooling shims. • New shafts (Oxford) and bearings obtained, DLC-coated, ready to complete two new actuators. • Further investigation of insulation in progress in parallel. • What insulation strength is required? • DC supply at 220 V – plus switching spikes with inductive load? • Measured at ISIS, but only PSU end accessible (>20 m cable) • Overshoot only 20 V • Will measure at actuator end when new actuator available • Measured old coils, with/without mica & kapton insulators. Breakdown at 1-2 kV • Will construct test assembly with new coils & insulators, and test that. • Could modify supply to ±110 V – halve voltage to earth. (Cost?) • Could put coils in parallel – again halve voltage, improved future control? University of Sheffield

6. Demonstrator Rebuild (continued) • Two complete drives under construction • First stator should be complete this week • Initially using existing magnets • New magnet assemblies due mid-June • Includes Sm-Co for comparison, spares for radiation tests • Installation in ISIS during August shut-down • Before that, thorough testing of both complete units • Tests in Sheffield (both actuators) • Demonstrator system run in R78 • Improved cooling to be installed in shutdown • Chiller in catacombs • Must include flow meter for protection! University of Sheffield

7. Operation in ISIS • Several successful runs in ISIS • See table • Mainly running in MD periods, one “parasitic” shift • Target position, ISIS beam loss, ISIS current digitised and stored pulse-by-pulse • Good stability over many pulses • Small spread in dip-depth • No target drops • Several scans of dip-depth and timing performed • Aim to explore beam profile, find optimum settings • Analysis very difficult • Noisy beam-loss signal – fits performed to extract value • Only have overall ISIS beam-loss signal (not local) • Dominated by injection losses early in cycle University of Sheffield

8. Pulse Statistics University of Sheffield

9. Beam loss Beam on Target trajectory Fitted beam loss University of Sheffield

10. Parameters of target scan • Dip travel at maximum • Time at maximum depth • Estimated beam loss University of Sheffield

11. Preliminary!! University of Sheffield

12. Conclusions (to end May) – preliminary • Delay scan shows we can successfully run parasitically with ISIS at 50 Hz • Scan about extraction  plenty of room for adjustments • No interference with next injection • Good rapport with ISIS control room • Beam loss greater earlier in cycle (as expected) • Some correlation with increased counts in scintillators • But hard to see target-induced beam loss at early times • For “optimum time” (last 2 ms), maximum dip depth only just reached 50 mV beam loss • Intervention 20th May to lower target frame • Lower limit switch moved • Target now ~8 mm lower than previous University of Sheffield

13. Thanks Eddie & Jim! University of Sheffield

14. Run Monday night … • New delay & depth scan with revised target frame position • Increase depth beyond previous limit (at optimum time) • ~3 mm deeper, beam loss increased ~×4 • (3.6 mm deeper. ISIS not so happy!) • Improved estimate of new target position? • Beam loss nicely peaked in last ms (tail to earlier times) – see photo • Correlations with counts in GVA1 • Scans at earlier times. Increases in losses and counts (analysis in progress) • More running due Tuesday night … University of Sheffield

15. University of Sheffield

16. Increased beam loss!! Thanks Eddie & Jim! FWHM only 0.6 ms University of Sheffield