Details of activities:
PART 1 : commissioning of the solenoids
A.12.1: Commissioning at injection level with Alice solenoid
ON.
1.
Inject beam1 and beam 2.
2.
Orbit measurements and corrections
o
For both beams, measure the orbit
o
Flatten orbits if necessary
o
Save a reference for both beams
3.
Coupling measurements and corrections
o
For both beam measure the machine coupling
o
Correct if necessary (this should have been done already,
the machine coupling should be correct).
o
Save a reference for both beams
4.
Switch ON Alice solenoid (Standby current)
o
The control of Alice solenoid can be done from Alice control
room or from CCC.
o
Call Alice control room and ask the operator if it's OK to
switch ON the solenoid.
5.
Orbit measurements and corrections
o
Measure the orbit for each beam
o
Display the difference with the reference that has been
saved previously.
o
Apply a correction if necessary:
the solenoid shouldn't
have any visible effect on the orbit.
6.
Coupling measurements and corrections
o
If the beam life time is correct, their is no need to
measure the coupling as the effect of the solenoid is expected
to be negligible. Go directly to the next point.
o
If the beam seems to be affected by the solenoid, perform the
following steps:
o
For each beam, measure the coupling
o
Compare with the reference, the difference gives the
coupling effect of the solenoid at standby current.
o
Correct if necessary, using the knob to trim the machine
coupling.
o
Iterate until the coupling is correct for the 2 beams.
A.12.2: Commissioning at injection level with Alice solenoid
ramped to nominal current.
1.
Start Alice solenoid ramping
o
Call Alice control room and ask the operator to start the
solenoid ramping.
o
dI/dt=15A/s Inom = 30 000A , ramping time around 1 hour.
o
During the ramping, check the beam losses, beam size and
life time
2.
Coupling and orbit measurements at nominal current
o
When the solenoid current has reached the nominal current,
measure and correct the orbit and coupling for both beams as
described in steps
A.12.1.5 and A.12.1.6.
3.
Alice solenoid stays ON for the rest of the procedure.
A.12.3: Commissioning at injection level with Atlas solenoid
ON.
1.
Inject beam1 and beam 2.
2.
Orbit measurements and corrections: see
A.12.1
3.
Coupling measurements and corrections : see
A.12.1.3
4.
Switch ON Atlas solenoid (Standby current)
o
The control of Atlas solenoid is done from Atlas control
room
o
Call Atlas control room and ask the operator to switch ON
the solenoid.
5.
Orbit measurements and corrections : see
A.12.1
6.
Coupling measurements and corrections : see
A.12.1.6
A.12.4: Commissioning at injection level with Atlas solenoid
ramped to nominal current.
1.
Start Atlas solenoid ramping
o
Call Atlas control room and ask the operator to start the
solenoid ramping.
o
dI/dt=1.7A/s Inom = 7730A , ramping time around 1/2 hour.
o
During the ramping, check the beam losses, beam size and
life time
2.
Checks and corrections at nominal current: see
A.12.2.3
3.
Atlas solenoid stays ON for the rest of the procedure.
A.12.5: Commissioning at injection level with CMS solenoid
ON.
1.
Inject beam1 and beam 2.
2.
Orbit measurements and corrections: see
A.12.1
3.
Coupling measurements and corrections : see
A.12.1.3
4.
Switch ON CMS solenoid (Standby current)
o
The control of CMS solenoid is done from Atlas control room
o
Call CMS control room and ask the operator to switch ON the
solenoid.
5.
Orbit measurements and corrections : see
A.12.1.5
6.
Coupling measurements and corrections : see
A.12.1.6
A.12.6: Commissioning at injection level with CMS solenoid
ramped to nominal current.
1.
Start CMS solenoid ramping
o
Call CMS control room and ask the operator to start the
solenoid ramping.
o
dI/dt=1.7A/s Inom = 19 500A , ramping time around 3
hours.
o
During the ramping, check the beam losses, beam size and
life time
2.
Checks and corrections at the middle of the ramp :
o
When the solenoid current has reached half of the nominal
current, measure and correct the orbit and coupling for both
beams as described in steps
A.12.1.5 and A.12.1.6.
There is no need to stop the solenoid ramping given the slow
ramping rate.
3.
Checks and corrections at nominal current: see
A.12.2.3
4.
CMS solenoid stays ON for the rest of the procedure.
A.12.7: Ramp the LHC with the three solenoids ON.
1.
Incorporate the coupling correction into ramp settings, so that
the correction smoothly goes to null. (One could also
incorporate so that it scales with the inverse of the momentum),
2.
Start ramp, the solenoid coupling effect is decreasing with
energy
3.
Perform a last measurement and correction of the coupling
at high energy.
Note 1 : For Alice and Atlas solenoid, the coupling effect will be
very small, it may even be smaller than the resolution of the
coupling measurement. In addition the coupling will also vary
with other effects like orbit drifts during the solenoid
ramping.
Note 2 : the orbit measurements and corrections has to be repeated
with the crossing angle ON, in phase B of the beam commissioning
: CMS magnet will create an orbit distortion that will not be
negligible.
PART 2 : commissioning of the spectrometers.
A.12.8: Orbit reference for beam 1 and beam 2.
1.
Inject beam 1 and beam 2.
2.
Measure the orbit for both beams, correct if necessary
2.
Save a reference for both beams.
A.12.9: Dump Beams and ramp down.
A.12.10: Switch ON Alice dipole and the compensators.
1.
In
equip state select the power converters
o
RBLWV.R2 (spectrometer)
o
RBWMDV.L2 (central compensator)
o
RBXWTV.L2 and RBXWTV.R2 (outer compensators)
2.
Switch ON.
A.12.11: Drive LHC to injection level.
1.
Check the settings for the spectrometer and the compensators.
A.12.12: Commissioning at injection level with Alice bump ON, one
beam in LHC.
1.
Inject Beam 1.
2.
Check the beam losses.
3.
Measure the orbit and check the bump closure.
There should be no orbit distortion due to the Alice bump.
In case that the bump is not closed, correct the closure by
applying kicks at the compensators or at the spectrometer. (the
correction shouldn't involve external correctors)
4.
In case of non-closure, check the transfer function and the knob definition.
5. If no error is found on the
knob, the transfer function will have to be corrected with beam
based values.
6.
Dump beam1, inject beam 2 and repeat the measurements.
A.12.13: Commissioning at high energy with Alice bump ON, one beam
in LHC.
1.
Prepare ramp:
o
If any doubt on the bump closure, the knob LHCBEAM/on_Alice
can be trimmed so that we don't accelerate with the full bump.
o
Incorporate the trims into the ramp settings.
o
Check the ramp settings for the main dipole and the
compensators
2.
Start ramp.
3.
Measurements at high energy
o
Switch OFF the Alice bump by trimming the knob LHCBEAM/on_Alice
to zero
o
Take a reference orbit.
o
Switch ON Alice bump by trimming the knob LHCBEAM/on_Alice
to 1.
o
Measure the orbit again, the difference with the reference
shows the bump, and the distortion due to the bump if it is not
closed properly.
o
Correct the bump closure if necessary (only using kicks on
main magnet and compensators)
o
When the bump is checked and corrected, dump the beam ramp
down.
4.
Recycle LHC and prepare for injection
A.12.14: Commissioning at injection level with Alice bump ON, two
beams in LHC.
1.
Inject the 2 beams.
2.
Repeat the steps
A.12.12.2 to A.12.12.4 for both beams.
A.12.15: Commissioning at high energy with Alice bump ON, two
beams in LHC.
1.
Repeat step
A.12.13
for both beams.
A.12.16: Polarity change.
1.
Switch OFF the main magnet and the compensators
2.
From equip state, change the polarity of the main magnets
and the compensator
Note 3: the FGC should always get a positive function, whatever
the polarity. The read current is always positive as well.
positive polarity : RBLWV.R2 -> positive polarity
RBWMDV.L2 -> negative polarity
RBXWTV.L2 -> positive polarity
RBXWTV.R2 -> negative polarity
For the negative polarity, the polarity of the main dipole and
the three compensators has to be inverted.
A.12.17: Repeat the procedure from A.12.10 to A.12.15 with the new
polarity.
A.12.18: Use the same procedure to commission beam with LHCb.
LHCb dipole and compensators power converters :
RBLWH.R8 (spectrometer)
RBXWH.L8 (main compensator)
RBXWSH.L8 and RBXWSH.R8 (outer compensators)
positive polarity : RBLWH.R8 -> positive polarity
RBXWH.L8 -> negative polarity
RBXWSH.L8 -> positive polarity
RBXWSH.R8 -> negative polarity
Note : The commissioning at injection level and at high energy is
done with the standard injection optics that is also used for
ramping.
|