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Commissioning Comments

Commissioning Comments. Dr. Carol Johnstone EMMA workshop Daresbury Laboratory Dec. 1 – 4 2009. Pre-commissioning. ALICE Emittance measurements as a function of energy Energy settings measured and verified Injection line Commissioning Shake-down of BPMs, screens,

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Commissioning Comments

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  1. Commissioning Comments Dr. Carol Johnstone EMMA workshop Daresbury Laboratory Dec. 1 – 4 2009

  2. Pre-commissioning • ALICE • Emittance measurements as a function of energy • Energy settings measured and verified • Injection line • Commissioning • Shake-down of BPMs, screens, • Optics and tomography verification • Independent, manual scans don’t find solutions unless the optics are trivial • When the line is understood, mults to control different optical parameters can be implemented • Emittance measurements out of ALICE in injection line DON’T UNDERESTIMATE THE DIFFICULTY OF UNDERSTANDING BOTH THE OUTPUT OF ALICE AND GETTING THE MATCHING AND TOMOGRAPHY SECTION WORKING!

  3. Commissioning EMMA • Inject into EMMA – • Set EMMA up for 90 degrees of phase advance at chosen injection energy and centered as much as possible in EMMA • Minimizes lattice defects, steering and optics errors • Energy and emittance should be chosen based on stable ALICE operation • Kickers are orthogonal, one in phase with septum, hopefully dialing kickers will allow initial circulation of beam without moving or changing septum magnet • Find the beam immediately downstream of septum • Won’t see it on the controls system; • Timing, possibly intensity, gating and acquisition will have problems. • If these have been pre-resolved in injection line you stand a chance • Most likely - scope plugged into BPM will be the first indication of beam – you will see garbage even if the beam does not make it through the septum, but no position information • Loss monitor is also useful to see which wall you are hitting

  4. First turn • Boot-strap it around ring – hopefully if the septum is close, the two orthogonal kickers will place it on a reasonable orbit • Getting it around the ring is the first order of business. • You will find serious problems in this exercise – reversed magnet, for example • Identify reference orbit • The problem is to identify the operational reference orbit – this will be a minimization problem using all available BPMs compared against ideal BPM values from lattice simulation. • With no changes in quadrupole strengths or location attempt to reach uniform solution which is repetitive and minimizes deviation from ideal orbit calculation • We have programs which will identify bad BPMs, calibration problems, and measure phase advances.

  5. Correction of orbit/optics • Fix calibration offsets, eliminate or fix bad BPMS from data analysis • Re-take data and re-check phase advances • Do “local” bump through problem cells to verify/correct cell problems • In the final analysis the operational reference orbit will deviate from all simulations – • This is where you hopefully improve the accuracy of the EMMA model to match reality • Stabilize orbit over a few turns (may have to change magnet strengths slightly to move off a resonance, for example) • Tune measurements • Initial aperture scans • Steering with “bumps” or tune increase/decrease to move orbit across aperture • Find locations of restrictions

  6. Multi-turn commissioning • Tune measurements over stable circulating orbits • Check lattices for different magnet settings • Verify BPM calibrations over large dynamic range and with changing beam sizes • TOF • Change energy out of ALICE • Scale currents in EMMA to keep 90 optics • YOU WANT THE SAME REFERENCE ORBIT AND BEAM SIZES- you do not want to fight systematics • Measure TOF from BPMs – same and consecutive ones • Compare against predicted TOF changes from the change in energy out of ALICE • We should know the orbit pathlength fairly accurately from the simulations and verified BPM positions • Develop algorithm to reduce TOF data from BPMs and understand accuracy against the different energy benchmarks

  7. Just the Beginning • Get screens, wall current monitors, etc. working • Commission extraction line • Partial turn - minimize emittance blowup to compare injection and extraction tomography results. • Keep the 90 lattices to assist in constant extraction performance and study extraction line as a function of energy • If we are really brilliant we might be ready for RF at this point

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