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