- Very low lifetime (few tens
of turns)
- Causes: Thin obstacle (a
"phantom" valve or other objects with thickness in the mm range,
pressure bumps), poor optics control, strong non-linear effects
(e.g. MS not powered properly).
- Diagnostic tools: check
performance with probe pilot beam (with small transverse and
longitudinal emittances), BLMs, mobile BLMs and display, BPM
intensity mode, radiation survey piquet, systematic optics
measurements from orbit response analysis
- Remedies: Obstacle
removal, optics correction, leak fixes
- Issues: Activation of components
at problem location - cool-down times
- Large coupling
- Causes: Magnet model uncertainty,
wrong MQS settings, polarity/cabling errors, calibration errors
- Diagnostic tools: Cross-plane
orbit response with local bumps at the MQS
- Remedies: Correction from
measurements
- Issues: Analysis tools
- Large chromaticity
- Causes: Magnet model uncertainty,
wrong MS settings, polarity/cabling errors, calibration errors
- Diagnostic tools: Phase
advance along the ring versus momentum offset
- Remedies: Correction from
measurements
- Issues: Analysis tools
- Large path-length difference
(> 5mm) between beam 1 and beam 2, leading to large offsets after
capture
- Causes: Differences in Bdl among
apertures larger than expected
- Diagnostic tools: Measure the
revolution frequency of the 2 beams with RF off
- Remedies:
- Need to have different SPS extraction magnetic fields for beam 1 and beam 2 (2
different cycles) if we want to keep the same RF frequency.
- We can run with two different
frequencies in the 2 LHC rings and resynchronize at high energy.
In which case the two beams might slide with respect to each
other. This is however not a problem in this Phase, while the
beams are still separated.
- Low capture efficiency
- Causes: RF voltage
might be smaller than expected, if there is wrong phasing of the
cavities (preadjustment problem)
- Remedies: Perform step
A.2.7.3 (check phasing of the cavity sum)
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