Stage B 50 ns: outline
Prerequisites:
50 ns. clearly marks a move to higher intensities
- Machine protection needs to be fully commissioned
- Parameter control needs to be well mastered
- The squeeze, only partially commissioned at this stage, needs to be pushed
to 2 m, with the associated control of key beam parameters.
- Associated beam instrumentation for said parameter control has to be
operational: orbit feedback, tune PLL (at least), robust feedforward control
of chromaticity and coupling.
Operations
Parameter tolerances will necessarily tightened up. Optics/beta beating under
reasonable control (and measured)
- Commission crossing angles. Re-commission ramp and squeeze
- Injection: long range beam-beam, effect on dynamic aperture, need for
tighter parameter control
- Need for feedback (orbit at least) plus adequate control of tune and
chromaticity through snapback.
- Lifetime and background optimization in physics with a crossing angle and
reduced aperture needs to be mastered.
- Bunch train bunch-to-bunch variations, implications for beam
instrumentation.
- Emittance conservation through the cycle has to be well under control & we
have to be able to measure it. Associated BI has to be fully commissioned.
- The squeeze, only partially commissioned up to now, needs to be well
mastered including the implications of crossing angle and long-range
beam-beam.
Machine Protection
BLMs: extensive range of monitors connected to MPS will appropriate
thresholds set.
Beam dump: commission with multi-bunch batches, verify dump kicker timing
versus beam
Collimators: collimator efficiency starts to be critical, relative retraction
of secondary collimators with respect to primaries established throughout complete cycle.
Lock-in of collimator settings at high energy (above threshold intensity).
Reduced aperture in the triplets, possible need to commission triplets.
TDI: positioning with respect to primaries know critical at injection
TCDQ: has to track collimators through cycle.
Absolute critical that above procedures are mastered before attempting
higher intensities. This can't be rushed.
RF
Injection capture of multi-particle batches. optimisation of capture
efficiencies. Timing in of LFB and TFB gain function, tuning etc.
Injection
Check extraction and injection timing
Other justification for 50 ns
- Possible multipacting/e-cloud with 25 ns - vacuum
- Smaller emittance from injectors with 50 ns - more room for maneuver
- CMS timing checks - explicit request