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AD E-Cooler Meeting: ADEC Powering and Interlock

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865/1-D17 (CERN)

865/1-D17

CERN

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Adriana Rossi (CERN)
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Present:
 Adriana Rossi; Alexandre Frassier; Christophe Machado ; Luke Von Freeden; Yves Thurel; Davide Gamba; Lars Varming Joergensen; Gunn Khatri; Ole Marqversen; Todor Todorcevic 
Excused:
Alessio Bollazzi
 
Adriana introduced the meeting explaining that the production and testing of mechanical components is going well, and that we should now finalise what we need to do on Interlocks and electron current modulations (to be able to measure with the BPM)
 
DAVIDE: recalls specs for the power converters
References: Specifications detailed in EDMS 3014577 and in 2479971 for PC 
 
  • Cartoon on how the e-cooler works from the point of view of powering
  • Values of current during magnetic measurements will be fixed for field quality
  •       “                  “          for orbit corrector of course will be varied with orbit/energy (and correctors for field quality might have to follow, will see during measurements). It is hoped/expected that correctors will not affect field quality.
  • Curves (from EDMS 3014577) shows the cooling (emittance) vs time, for different field quality. We aim at the ‘green curve’
  • Solenoid of e-cooler and compensation solenoid must have correct current direction: polarity test of installed magnets and polarity test after installation to be foreseen.
  • Measurement of the electron orbit is very beneficial to tuning of the cooler (BPM)
    • ==> modulation on electron current necessary ==> modulation on extraction voltage.
  • Energy drift of pbars (due to electron space charge or to HV power supply ) is clearly observable. 
    • ==> Vcathode stability and reproducibility needs to be in the 10-5 ==> 
    • Todor: Power supplies are well regulated, but cables can pick-up noise (temperature and electron-magnetic noise)
  • Change of V level with time also observed (on pbar energy) believed to depend on age of converters. Note that to debug such problems would require measurement of V up to the e-cooler and we do not have measuring systems accurate enough at these voltages.
  • We cannot recuperate this time now, because ramping earlier would perturb pbar (losses)
    • Switch would be necessary now because power supply would not be fast enough.
    • Current switch not used because there are problems with it since the gun was changed (date).
    • New e-cooler will have the grid voltage that can be regulated to switch on/off the e-current fast enough (specifications). even if not ideal, will be much better than now. tests will be done to verify and in worse come to the worse we think of installing a switch.
  • Need of switching the electron beam off completely (see later)
  • Interlock system necessary to avoid damage if e-beam is lost.
 
YVES for Alessio: status of DC power convertor procurement and testing
  • COMBO: all material is at CERN, assembly ongoing, tests ongoing. 1 to 2 months to completion (to be verified with Alessio)
  • SMILE converters available have been re-qualified, those in use will be done after de-installation during LS3.
  • Todor writing an ECR for all bldg. 193.
  • Interlock boxes at magnets should be procured
  • Richard Mompo needs to do the DIC for the cables 
     
CHRISTOPH:
  • All power supplies arrived, tested to specs OK
  • Power supply bought with in mind the cable impedance as now (~40-50m) that MUST NOT be increased.
    Adriana and Gunn explained that we are going to reuse HV cables where possible and buy spares only if something breaks during de-installation and installation. Access on May 21, 2026 to cress check.
  • Tests of voltage ramp in < 1s OK
  • Ability of going negative (grid) to completely suppress e-beam pending.
  • Cage size is fine, no additional equipment but the PS and the Pearson transformer are needed.
  • Agreed that cage is SY-BI responsibility and equipment inside cage SY-EPC responsibility
 
ALEX:
  • Electron beam current modulation
    • Currently done with Pearson transformer for the modulation of the Vgrid to modulate Ibeam.
      • This works with the grid connected to ground. Not compliant with EPC standard
      • To be rediscussed if we can work with additional power supply or find an equivalent transformer. 
      • Requirements on modulation:
        • +/- 5V at ≥ 100kHz, possibly with frequency as multiple of AD revolution frequency. (if possible, add -200V so that grid can completely suppress electron emission)

  • Interlocking system: 
    • Alex showed the table for WIC-modified interlocks. What should be switched off under which condition.
    • NOTE from Luke/Yves: Magnet power converter time constant is ~ ms.
    • Self-protection, as soon as there is I_loss to ground, the power supply will switch off.
    • Do we want to switch off the magnets X sec after the HV is switched off? No because the I_loss is only few mA. If there are current losses of few mA they can run for few sec without risk of damage of vacuum chambers or NEG coating.

  • Electrical safety: Cage modifications to be done to comply with CERN safety standards, paid on safety budget.
 
AOB: Davide: Filament power supply that is in the cage should never switch off if not needed because it takes hours to be switched on again, and the filament current should be set in a controlled way. Ideally would be nice to have a UPS.
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