J. Turner 02/07/05 SLAC PEPII Accelerator Physics LER WIGGLER PLAN J. Turner, M. Donald, M....

J. Turner02/07/05

SLAC PEPII Accelerator Physics

LER WIGGLER PLANJ. Turner , M. Donald, M. Sullivan, U. Wienands, J. Yocky

Motivation and ConcernsDetails of Concerns

The Plan


J. Turner02/07/05

Motivation and Concerns

• For putting more current into LER with reasonable lifetime once we’ve filled all the buckets, the horizontal emittance will be raised by turning on the Wiggler. Added benefit is some bunch length shortening in HER from the necessary frequency change.

• Concerns– Matching IP Beam Size (Uli study)– Getting energies right (M. Sullivan’s slides)– β match


J. Turner02/07/05

Uli’s Dynamic Beta Calc

• Uli checked, and it appears that for our present beam parameters, under full dynamic beta, the IP beam sizes are as follows in X: – LER:76.8 µm, HER:93.6 µm. – So the LER would be somewhat smaller than

the HER and the wiggler would help equalize the two. The calculation starts form our standard conditions (beta_x=28 cm (HER), 50 cm (LER), epsx=51 nmr (HER) and epsx=26 nmr (LER)), but these get rather heavily modified by the dynamic beta.


J. Turner02/07/05

Summary of last Wiggler/Energy change to the LER From Mike Sullivan

Martin Donald says that the wiggler changes the path length by +1.485 mm

Using this equation: = 1.23e-3 for the LER

We should get a f of 320 Hz and a p of -1.71 MeV

According to my plots the LER changed energy by +3.57 MeV when the wiggler was turned off on March 1, 2000. This would correspond to a frequency change of 670 Hz.

In looking at some of the frequency scans we did around that time, I see about a +360 to +530 Hz change in the central frequency for the LER and no significant change in the central frequency for the HER.

The present RF frequency is set to 475999685 Hz

f

f

p

p

C

C


J. Turner02/07/05

Summary of last Wiggler/Energy change to the LER From Mike Sullivan


J. Turner02/07/05

The Plan

• In general we want to go from ~24nm to ~35nm in the initial step which will raise the wiggler. After that we hope to be able to inch from ~35nm to ~48nm using the wiggler and tune quads.

• Preparatory (before MD) work:– Establish Wiggler Polynomial and Field confidence

• in progress Turner/Yocky

– Make Matching Knobs • done: Martin Donald: at 1.58T he can do ~35nm to ~48nm

with the quads and they look pretty linear.

• http://www.slac.stanford.edu/~mhd/050202/wiggler-at-1.58.pdf


J. Turner02/07/05

The Plan continued (#1)

• In the Control Room– Take Preparatory data: full characterization including

phase advance, MIA, and single ring orbits, injection orbits including NIT with HER and SIT with LER for later energy diagnosis, and orbit versus frequency scan.

– With non-colliding beam in both rings, raise wiggler to 1.58T

– Change the LER Match and Tunes simultaneously– Change (lower) the Linac and PEP frequency looking at

LER energy fit to difference to initial data.• In simulation Martin finds 1.485mm path length change for

wiggler full on (1.8T). See Mike’s slide.

– Change the Energy knob in HER to recover energy fit to difference to initial data


J. Turner02/07/05


– Steer in the Wiggler region using only magnets in the Wiggler region area in both rings

– Establish injection into both rings, compare injected orbits with saved orbits as far as energy

– Take LER phase advance and MIA data to evaluate whether β match correction is necessary (start calc of new match if indicated)

– Standardize if necessary from HER change– If standardize, re-steer as necessary, and

recheck injected beam energy comparison


J. Turner02/07/05


– Save orbit versus frequency data– Save magnets and orbits and go to collisions – Unless the luminosity is higher than before,

turn off all orbit control in HER except in the IR and briefly try putting in a horizontal dispersion wave thereby modulating the IPX beam size with dispersion.

– Implement new beta match if indicated


J. Turner02/07/05

Tunnel Wiggler wiring

J. Turner 02/07/05 SLAC PEPII Accelerator Physics LER WIGGLER PLAN J. Turner, M. Donald, M....

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