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ALICE Magnets

ALICE Magnets. Ben Shepherd MaRS Group ASTeC STFC Daresbury Laboratory. Overview. Magnet settings table Calibration / field maps for energy measurements Degaussing Controls Online field measurements. ALICE Magnets.

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ALICE Magnets

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  1. ALICE Magnets Ben Shepherd MaRS Group ASTeC STFC Daresbury Laboratory

  2. Overview • Magnet settings table • Calibration / field maps for energy measurements • Degaussing • Controls • Online field measurements

  3. ALICE Magnets • 66 magnets – a combination of new magnets (Danfysik) and some donated by Jefferson Lab + air core magnets (solenoids, correctors) QA QA QA QA DA DA QA QA DA QA QA QD DD QD DD QD S QD QD QD QD S QE QD QD QE QE QD QD DD DD QD QD QD QD S S DD DD

  4. Magnet Table • Hall probe and integrating coil tests have been carried out on all the new magnets • Field map produced for one of each type of the JLab magnets • Results summarised in a table relating model magnet strengths to required currents • http://projects.astec.ac.uk/ERLPManual/index.php/Magnet_table

  5. Magnetic hysteresis • At the low fields used in these magnets, hysteresis can have an effect • The field produced by a magnet will be slightly different depending on whether the current is being increased or decreased field current • e.g. for INJ-MAG-DIP-01 (field directly measured): • typical difference is about 8G (1% of nominal field) • 0.3° change in angle: 7mm at the OTR screen • The PSUs in use do not have the capability to bring the magnets to saturation • For a reproducible field: • Always increase the current • If you need to reduce it, take it back to zero first • A simple tool will be written to encapsulate this procedure • Worst case is probably the JLab quadrupoles

  6. Online field measurements • Three dipoles are important for energy measurements: • INJ-MAG-DIP-01 (first after booster) • AR1-MAG-DIP-01 (first after main linac) • ST1-MAG-DIP-01 (dump dipole) • A Hall probe is attached to the pole of each of these • Calibration has been carried out with respect to central field • This provides a check on the field • Should result in more accurate energy measurements

  7. Energy measurements (1) • INJ-MAG-DIP-01 • Used for measuring energy after the booster • We have a complete field map of this magnet • Take measurements of: • Initial angle and position (from YAG-03 and BPM-03 or YAG-02) • Central field (pole-mounted Hall probe) • Final angle (from YAG-03 and -04)

  8. Energy measurements (2) • AR1-MAG-DIP-01 • Measure energy after the main linac • For this magnet, we have integral fields along the nominal beam path and central fields • To measure energy: • Ensure the beam is going through the centre of ST1-OTR-04 andAR1-OTR-01 • Measure the field (pole-mounted Hall probe)

  9. Energy measurements (3) • ST1-MAG-DIP-01 • Measure energy post-deceleration • Two beams go through this dipole • When dumping the decelerated beam: • DON’T change the dump dipole current! • Record the field (pole-mounted Hall probe) • Record the position on DMP-OTR-01

  10. Magnet Controls • Control panel on the control room Linux consoles • Main Menu  Commissioning  Magnets • Magnet controls for the entire machine

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