ABT/BTP and BLM

1. Long Collimators Angular Beam Based Alignment and Injection LossesThursday May 5th from 0:00 until 8:00 ABT/BTP and BLM

2. MD Motivation: Long Collimators • Machine safety depends critically on the correct setup of the protection elements. Injection and extraction protection collimators (TDI and TCDQ) are constituted by exceptionally long carbon based jaws (4 m and 6 m respectively). For these elements, an angular offset of the jaws could affect significantly the measured beam size and, as a consequence, their correct setup. • Loss behavior, during the beam based alignment, might be influenced by instabilities induced by the long jaws impedance. • Dedicated studies and cross-calibrations have to be performed to quantify the effect of tilts, offsets and impedance on the collimators setup and following provided passive protection. • For the TCDQ, these effects have to be analysed at injection and top energy.

3. MD overview: Long Collimators Angular scan for TCDQ collimators (TDI already checked): • Define beam edge with primary collimator (blow up beam with MKQ until seeing losses at the TCPH) • Set left jaw angle to +1 mrad • Move the jaw, with the fixed angle, in steps (0.25 s) into the beam, record losses at the TCDQ and jaw corners position • The beam centre is given by the position corresponding to losses going to zero (full beam scraped) • Repeat with a different angle (0.250 mrad steps until -1 mrad) • Plot beam centre as a function of applied angle  the jaw should be parallel when beam centre is minimum

4. Beam Requirements: Long Collimators • 1 pilot bunch circulating • Beam 1 and Beam 2 • 450 GeV injection optics • No special requirements for emittance • Move collimators: TCP and TCDQ (open position and energy thresholds) • Mask all maskable BLMs and BPM in IP6 • Check effect of transverse damper ON/OFF on beam losses during alignment (impedance? How do losses change as a function of collimator half gap?) • MKQ used to blow up the beam

5. MD Motivation: Injection Losses • Two main sources of losses which could limit the intensity of the injected beam are observed: 1) Showers of particles which are generated by the TCDI intercepting the beam tails in the transfer lines and are detected by the ring Beam Loss Monitors (BLM). 2) Un-captured beam, from the SPS and the LHC, that is spread onto the TDI jaws. • Possible solutions are considered to mitigate these losses and need to be tested. In particular we have to measure: • The effect of shielding on showers from TCDI and TDI collimators (experiment BCM sunglasses)  check effect of shielding in TI 8. • Injection/abort cleaning. Measure number of injections possible w/o injection and abort gap cleaning and the dependency on the time spent between injections and on the intensity • Further optional studies: • Effect of BLM sunglasses on triggering beam dump on injection losses (if implemented and commissioned )

6. MD overview: Injection Losses • Check effect of shielding in TI 8 on LHC ring BLM response during injection: • Open all TCDI to +/- 15 mm (mask jaw position and energy interlocks) • Close left jaw of the first TCDI to -3 s • Extract the beam on the TCDI closed jaw (3 shots) • Set the TCDI left jaw back to + 15 mm • Repeat for the following TCDI (in total 6 jaws: 18 shots) • Offline analysis and comparison with measurements before shielding installation

7. Beam Requirements: Injection Losses • 1 pilot bunch, inject and dump (turn 0) • Only Beam 2 • 450 GeV injection optics • No special requirements for emittance • Move collimators: TCDI (mask position and energy interlocks) • Mask all maskable BLM and BPM in IP6 • Mask SPS BQM

8. MD Plan No measurements in parallel to avoid BLM cross-talks during measurements. • From 0:00 until 7:00 long collimator angular scan • From 7:00 until 8:00 injection losses