CERN Accelerating science

Injection - intermediate intensity

Intensity of the pilot will not provide the required sensitivity in the BPMs to properly position the collimators, say. Therefore this additional mode will be required. We dump the pilot, keeping pilot as witness beam and dumping it on the TDI, and take intermediate beam. Here intermediate is something like 2.5x10^12 protons (total).   12 nominal-ish bunches

See beams for details of proposed intensities.

Clearly would like to avoid having to repeat this phase every fill if at all possible. Clearly dependent on the reproducibility of orbit at collimators.

See collimators

See JJ Gras write-up at Chamonix

Prerequisites

The injection collimators must be in to at least coarse positions and possibly some auxiliary collimators (2 secondary betatron and 2 secondary momentum). The TDI must be in position.

Orbit

Orbit control in the injection region will be extremely important. To be controlled with intermediate beam:

• Separation at IP: orbit bumps �
• Separation at parasitic crossings: crossing angle
• Compensation of spectrometer magnets. ALICE's spectrometer magnet will be off at injection � However IP2 will need a vertical crossing angle � 210 mrad plus a possible need for orbit offset at MKI - additional 3 bump plus a horizontal parallel separation bump �
• LHCb's spectrometer magnet on & it can change polarity, the foreseen compensation produces large crossing angle in horizontal plane, combined with horizontal crossing angle bump parallel vertical separation bump.

Sequence

1. Intermediate blue ring, fine positioning of collimators, TDI. Orbit optimisation. Keep beam.
2. Intermediate yellow ring, fine positioning of collimators, TDI. Orbit optimisation. Keep beam.
3. Check crossing angles. And everything else before dumping beams, freezing everything. Minimise time between dump of intermediate beams and injection of full intensity.