Transcript Faraday Cup Award: High Sensitivity Tune - Indico

Tune excitation systems at CERN
Marek Gasior, Rhodri Jones, BE-BI
Introduction:
- A harmonic resonant excitation is much more efficient than a single kick.
- Today almost all CERN machines have or will have transverse damper systems, which can be used for
tune excitation.
- The same hardware can be used for “AC dipole” excitation for optics and beam transfer function
measurements.
- Long term strategy: harmonic excitation on all CERN machines.
Beam Instrumentation Group
Tune excitation systems at CERN
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LHC and SPS
LHC:
- Harmonic excitation with the transverse feedback amplifiers (ADT), signals generated and controlled
from the tune system itself.
- Chirp excitation for tune measurement and single frequency AC-dipole style for BTF and coupling/optics
measurement with DOROS
- No more than some 1 % of the ADT amplitude (i.e. 0.01 % of the power) is used for all measurements;
this is an arbitrary hardware limit put on the BI side.
- Everything works fine, stable situation.
- There is a tune/aperture kicker which is not used for tune measurement.
The kicker is not the BI responsibility.
SPS:
- Chirp excitation with the transverse feedback amplifiers, similarly to the LHC.
- Tune kicker operational but not the BI responsibility.
- Everything works fine, stable situation.
Beam Instrumentation Group
Tune excitation systems at CERN
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The PS and PSB
PS:
- Tune kicker removed completely a few years ago due to reliability issues and to gain space
on the vacuum chamber.
- Replaced by chirp excitation generated and controlled by the tune system itself.
- Power part of the transverse damper system used to put the excitation on the beam.
- Chirp excitation successfully operated for quite a few years now.
- Stable situation.
PSB:
- Kick excitation used for operation.
- Chirp and AC-dipole excitation with the transverse damper used for beam studies only.
- The kicker is a huge 25 ohm magnetic structure excited with one turn pulse.
- Typically the kick voltage is 500 V, giving very nice measurements.
The voltage can go up to 5 kV, but then there are reliability issues.
- The PSB chirp excitation is already connected to the transverse damper.
However, as the damper is not fully operational yet, the old kick excitation is used for operation.
- The chirp and AC-dipole excitation has been successfully used for MDs. It was demonstrated that this
way much larger amplitudes can be achieved than even with 5 kV kicks.
- Plan:
wait until the transverse damper is fully operational and then chirp excitation can be used operationally.
Beam Instrumentation Group
Tune excitation systems at CERN
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LEIR, AD and ELENA
LEIR:
- One turn kick excitation, typically 500 V into 50 Ohm, the same kick generation hardware as
on the PSB.
- Kicker: a short stripline, only one electrode used per plane to keep it simple, very nice excitations.
- The future:
The kicker system was installed when LEIR did not have a transverse damper.
Now there is a damper system and potentially it can be used for chirp excitation.
The excitation signals can be generated in the tune system, as it is done for the PS.
Good time to start discussing with the RF an option of using their amplifiers for chirp excitation.
AD:
- Chirp excitation only with the transverse feedback amplifiers, as there is no tune kicker.
- No need for changes.
ELENA:
- Plan to use chirp excitation, but there is no transverse damper foreseen.
- BI plans to install small RF amplifiers for chirp excitation. As the beam energy is very low, only simple
amplifiers are needed.
Beam Instrumentation Group
Tune excitation systems at CERN
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