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Brief summary of run #7 (30 August – 3 September)

Brief summary of run #7 (30 August – 3 September). Shinji Machida o n behalf of the beam commissioning team ASTeC /STFC/RAL 3 September 2010. Aims. Inject lower equivalent momentum beam. Find rf phase dependence of time of flight. Reduce beam loss.

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Brief summary of run #7 (30 August – 3 September)

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  1. Brief summary of run #7 (30 August – 3 September) Shinji Machida on behalf of the beam commissioning team ASTeC/STFC/RAL 3 September 2010

  2. Aims • Inject lower equivalent momentum beam. • Find rf phase dependence of time of flight. • Reduce beam loss.

  3. ALICE beamfirst time to change momentum • 12 MeV kinetic energy (12.5 MeV/c momentum). • Gives a similar performance of a 15 MeV beam. • 20 – 40 pC, depends on tuning. • 1 Hz, can be 3 Hz. • 1 bunch, can be 5 bunches.

  4. Hardware restrictionssame as before • Only analog signal is available from BPM. Still 7 pairs (E-W or N-S) at one time. • Main quadrupole magnet is up to 350 A, enough for the present operation. • Maximum control voltage of septum is 8 V. • Up to 6 Hz due to the heating of septum. It is also enough. • If you change kicker amplitude, kicker timing also shifts. Difficult to adjust kicker strength at crest.

  5. Limited variables and diagnosticsalmost same as before • QD and QF strength and position. • Septum and kicker strength and timing. • Septum translation and angle. • Q and B at injection line. • BPM-EPICS card is not ready yet. • YAG in cell 5 and cell 22. • kicker-1 is in E02 and kicker-2 is in E03.

  6. Injection line • Magnet strength is not 12.5/15.5 ratio, but close. • Orbit and optics matching with try and error.

  7. Septum (1)translation and angle • Change septum angle. • It was 0.4928 deg. Now 0 deg. • Change septum translation. • It was -4.5 mm. Now -2 to 2 mm. • More physical aperture? • (When angle is not zero, which direction the septum moves?)

  8. Septum (2)Horizontal position at E01-EBPM-01 • Septum setting voltage (x-axis) vs position [mm] (y-axis). • No data in this run. Jul&Aug Jun Aug23

  9. Kicker (1)strength • Kicker 1 kicks at crest. Use the maximum strength (8 V), which should be 5.2 [mTm]. • Almost no kick by kicker 2. • Jitter of about 10 to 20 ns was solved. • “Quantum trigger box” did not synchronize with internal clock since 13 August. • Additional delay of ~500 micro sec introduced in the middle of August was removed. • Remaining jitter is 1 to 2 ns.

  10. Kicker (2)polarity • Kicker 1 kicks a beam outward and kicker 2 kicks inward. • Two questions. • Do we need to change the polarity of the second kicker? • Do we need to increase the limit of kicker?

  11. Full ring (1)lower momentum injection • Lower momentum injection (12.5 MeV/c ALICE beam and 12.5 MeV/c equivalent momentum lattice.) seems still difficult.

  12. Full ring (2)BPM signals for a few 100s turns • Decoherence due to finite chromaticitiyis observed. • Closed orbit distortion within 7 cells is observed. • Slow shift of orbits (not always negative) is observed. • David Kelliher’s analysis on Analysis folder.

  13. Full ring (3)shift of radius • Mean radius was controlled by the shift of all the quadrupoles either inward or outward (Scott Berg). • Moving inward helps to enlarge aperture. • Moving outward helps better orbit matching. • Any compromise?

  14. Transverse tunewhen a beam circulating more than 1 turn • We expect better measurement when a beam is circulating more than 1 turn. • Momentum dependence is not clear yet. Least square fit NAFF fit

  15. Time of flightwithout rf • Problem of 50 ps offset, often happens. • Trigger mode is not correct? • Internal clock is not accurate??? • Measurement with rf waveform helps.

  16. Next step (1)synchrotron oscillation inside bucket • We should identify a synchrotron oscillation with time of flight measurement with rf signal. • Parameters are global rf phase and rf frequency. • Easy to move phase, but takes more time to change frequency. • Need a check of individual phase. • Rf voltage does not have to be high. • EMMA frequency is the same as ALICE, 1.3 GHz.

  17. Next step (2)injection • Understand injection orbit for difference momentum. • If the kicker setting we found working reasonably understood by model. • Establish a strategy of optics matching. • Model (MAD-X or Zgoubi) fitting. • Practical way using two YAGs at E05 and E23. • Increase momentum acceptance.

  18. Next step (3)different lattice configuration • Further study of enlarging aperture. • Find other QD/QF configuration which gives beam circulation. • Measure tune and time of flight once we found one.

  19. Next step (4)slow loss • Can we explain the slow loss by scattering with residual gas?

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