Vertical emittance minimization update and low energy set-up

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Vertical emittance minimization update and low energy set-up. Andreas Streun, SLS, PSI. Vertical emittance minimization. presentation Wednesday 12:05 TIARA-REP-WP6-2012-008, specification of emittance knobs, May 2012. VET Methods . SLS developments 2000 - 2012.
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Vertical emittance minimization update and low energy set-upAndreas Streun, SLS, PSIVertical emittance minimization
  • presentation Wednesday 12:05
  • TIARA-REP-WP6-2012-008, specification of emittance knobs, May 2012
  • VET Methods SLS developments2000 - 2012
  • Prerequisite: stability and precision
  • orbit correction, feedback, top-up
  • Machine preparation
  • [beam assisted] girder alignment
  • optics correction (LOCO, QV, TBT...)
  • BPM roll error measurement
  • Model dependent methods
  • vertical dispersion suppression
  • betatron coupling suppression
  • Model independent methods
  • Random walk, minimization of beam size
  •  repeat, iterate, automate ....“LET” algorithm(S. Liuzzo)3 MD shifts!New beam size monitor
  • SLS vertical emittance values
  • limitation from existing monitor ~1 pm
  • design of new monitor  0.5 [  0.3 ] pm
  • quantum limit 0.2 pm
  • Budget & Time schedule
  • WP6 hardware budget 215 k€
  • design ~finished: TIARA report due June‘12
  • installation: July‘12 & Dec.’12 – Jan.’13
  • commissioning: Jan. – Mar. [?] ’13
  • measurements: Jan. – June ’13
  • SLS low energy operation
  • 1.6 GeV instead of 2.4 GeV
  • Ring setup problem
  • 3 normal conducting super bends, 3 T
  • fully saturated center pole, I = 500 A
  • center pole at 1.6 GeV: I  135 A !
  • orbit correction difficult
  • problem to get injection/accumulation
  • not well reproducible
  • Energy matching
  • booster extraction on 2.4 GeV ramp
  • energy from booster 1.617 GeV
  • energy from ring dipole cur. 1.569 GeV
  • energy from ring quad cur. 1.573 GeV
  • at nominal energy:
  • booster extraction 2.4 GeV
  • ring from spin depolarization 2.41100 GeV
  • ring dipole current 2.399 GeV
  • ring quad currents 2.411 GeV
  •  believe in quads Instabilities
  • nominal RF @ 2.4 GeV: 2.1 MV (4 x 525 kV)
  • 1.6 GeV:
  • 1 x 300..500 kV, 3 detuned  bad
  • 4 x 150...350 kV  better
  • Instabilities: long/hor/vert (mode 71, 136, ...)
  • best result (2010) for users:
  • up to 325 mA (400 bunches)
  • 4 x 320 kV and 3HC at 430 kV (1/3 Vtot)
  • recent (May’12) for IBS:
  • few mA (1 or 3 bunches): 4 x (100..500 kV)
  • 40 mA in aperiodic filling of 80 bunches
  • Energy spread measurementsessential for analysis of IBS data
  • Decoherence signal <x(t)>
  • fragile fit, many parameters
  • problem of BPM turn mixing
  • Sideband heights (FFT of decoherence signal)
  • unequal m peaks due to res.wall impedance
  • refined model including impedance ?
  • better data using MBFB ?
  • measurement of beam size
  • at dispersive and non-dispersive location
  • using scrapers and/or pinhole arrays
  • SLS: 2 scrapers at 0 and max. dispersion
  • SLS: pinholes only at low dispersion (bend)
  • horizontal scraper measurement: fit of lifetime to scraper position.quantum lifetime  beam sizepolarized light monitor at 1.6 GeVconfirms e = 2.4 nm  to be explored...(from ESRF)
  • undulator line width
  •  beamline 11M (the 1.6 GeV user) was asked...SLS shift plan (MD = ,)
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