BEAM COMMISSIONING WITH EXPERIMENTAL MAGNETS PROCEDURE

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BEAM COMMISSIONING WITH EXPERIMENTAL
MAGNETSPROCEDURE
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Layout

• Entry exit conditions
• Solenoid commissioning
• Dipoles commissioning
• Conclusions

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Entry Exit conditions

• Entry conditions
• Beam 1 and 2 commissioned at 450 GeV
• 2 beams circulating
• Good life time, reasonable intensity
• Orbit measured and corrected for both beams
• Tunes corrected, machine coupling corrected
  (deltaQ ltlt 0.01)
• Ramp commissioned, stable beams at 7 TeV.
• Machine coupling has been measured and corrected
  at 7 TeV.
• No crossing angle, no separation bump
• 1 bunch per beam Pilot or Pilot
• Exit Conditions
• The coupling effect of the solenoids is corrected
  (deltaQ ltlt 0.01).
• No orbit distortion due to spectrometer bumps.

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Beam commissioning with experiments solenoids

• Commissioning at injection
• Inject both beam, measure a reference orbit for
  each beam, get a coupling reference for both beam
• For each solenoid (Alice, then Atlas (toroids ON
  already), and CMS)
• Switch magnet ON (Standby current).
• For each beam, check the orbit against reference
  and correct if necessary (correction shouldnt be
  needed)
• Measure the coupling, correct if necessary (trim
  the coupling knob).
• Ramp the magnet to nominal current, measure and
  correct the coupling during the solenoid ramping.
• At nominal current, measure again, apply
  correction if necesary
• Stronger coupling correction should be needed for
  CMS. Atlas and Alice effect should be smaller.

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Beam commissioning with experiments solenoids

• Commissioning at high energy
• The machine coupling is expected to change a lot
  during the ramp. At this stage of the beam
  commissioning it has been already measured and
  corrected along the ramp and at 7 TeV.
• Extrapolate the corrections for the solenoid
  coupling into the ramp.
• Start LHC ramp, the effect of the solenoids is
  decreasing with beam energy.
• Check again the coupling and the orbit at 7 TeV.

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Beam commissioning with experiments spectrometers
(Alice then LHCB)

• Commissioning at injection
• Get a reference orbit for beam 1 and beam 2 at
  450 GeV. Then dump both beams.
• Switch ON the experiment magnet and the 3
  compensators.
• Drive LHC to injection level and inject beam 1.
• Check the orbit against the reference, there
  should be no distortion.
• If the bump is not closed properly, this can be
  corrected by applying kicks at the main magnet or
  the compensator.
• The bump closure has to be corrected locally,
  without using external correctors.
• The reason of the non closure has to be
  investigated (could comes from knob definition or
  transfer function)
• Dump beam 1, inject beam 2 and repeat the
  previous steps.

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Beam commissioning with experiments spectrometers
(Alice then LHCB)

• Commissioning during ramp
• Incorporate the corrections into the ramp if
  needed.
• Check the settings of the main magnet and the
  compensator for the ramp .
• Load ramp settings into Hardware, start LHC ramp.
• During the ramp and at 7 TeV, check the bump
  closure
• The orbit has to be logged along the ramp
• If the closure is not stable along the ramp, it
  will have to be investigating before going on.
• Dump beam and recycle.
• Inject both beams and repeat the procedure.

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Beam commissioning with experiments spectrometers
(Alice then LHCB)

• Polarity change
• The magnets have to be switched OFF for the
  polarity change.
• The complete procedure has to be repeated (at
  injection and during ramp) with the new polarity.
• We need clear description and references for the
  magnets polarity.

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Crossing angle commissioning

• With the crossing angle ON, CMS spectrometer
  creates an orbit distortion. It should be
  switched OFF during the crossing angle
  commissioning, and the orbit has to be corrected
  when it will be ramped again.
• Alice and LHCb spectrometers have to be
  commissioned again with the crossing angle ON, as
  the bump amplitude and angle are different.

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Conclusions

• LHCb spectrometer has already been commissioned
• It has been ramped together with the compensator
  following the LHC ramp.
• We learned that we have to deal with magnets and
  power converter limitations
• Minimum power converter current gives the minimum
  possible bump amplitude at injection.
• Maximum di/dt of LHCb magnet has to be taken into
  account to generate the ramp function.

LHCb ramp function.