u. wienands, y. cai, f.-j. decker, m. donald, w. kozanecki, yu. nosochkov, t. raubenheimer, j....

U. Wienands, Y. Cai, F.-J. Decker, M. Donald, W. Kozanecki, Yu. Nosochkov, T. Raubenheimer,

J. Safranek, D. Sagan., A. Seryi, K. Sonnad, C. Steier, P. Tenenbaum, A. Terebilo, J. Turner, M. Venturini, A. Wolski, M. Woodley, Y. Yan,

G. Yocky, M. Zelazny

PEP-II Lattice & Optics Progress

U. Wienands, SLAC-PEP-IIPEP Run 4 WS: Optics, 4-Aug-04

2

Progress: New Tools

• Model lattice for given config about measured orbit

• Updated Online Phase-Advance Package

• Online Coupling (C12) Analysis

• Orbit-Response-Matrix Analysis• Fudge-Factor Configurations


3

Progress: Ring Optics

• The HER got steered!

• Coupling in both rings monitored routinely– appears to be ok in LER– global coupling wave in HER

• ßy* got reduced in both rings to ≈1 cm

• ßx* in LER got reduced to 33 cm, match HER

• A 90° lattice for the HER is designed– ps parameters known, working on implementation


4

Online Phase Advance

• MHD interpolation algorithm now standard– Good results for HER and LER– much more robust against noisy data

• C12 analysis integrated with package

• Wave fits possible for ß and for C12,

• Together with Colocho’s macros, this measurement is now vastly faster than before– important for machine characterization


5

HER Coupling… raw C12(bar)HER Coupling… raw C12(bar)

HER Coupling… C12(bar) – fit wave

Note how Solenoid comp. is non-closed

HER Coupling… C12(bar) – fit wave

Note how Solenoid comp. is non-closed

Data of 10-Jun


6 HER C12… DesignM. Donald


7

LER Coupling… raw C12(bar)LER Coupling… raw C12(bar)

LER Coupling… C12(bar) – fit wave

Note better closure of solenoid compens.

LER Coupling… C12(bar) – fit wave

Note better closure of solenoid compens.

Data of 10-Jun before ß change


8 LER C12… DesignM. Donald


10

Ring Characterization

• Ph.-Advance, , ∑, Orbits about once/3 weeks– When indicated add MIA, ORM, CTA– Historical trend for these variables

• Monitor & correct (if applicable) lattice– Get idea about significance of changes

• Guidance to schedule ß changes etc.


11 HER ßy* HistoryHER ßy* HistoryLER ßy* HistoryLER ßy* History

LER ßx* HistoryLER ßx* History HER ßx* HistoryHER ßx* History

G. Yocky


12

∑x History∑x History

∑y History∑y History

Steering

Knob Recalib.


13

ORM Data Analysis

• We have HER and LER models in AT (LOCO)

• We have data sets for both rings for reasonably current configurations, together with phase-advance & MIA data

• The analysis gives ß functions & tunes in agreement with phase-advance

• We have derived magnet values from ORM


14

HER Magnet FactorsP. Tenenbaum


15

Fudge-Factor Configurations

• We have now Fudge-Factor Configs.

• They modify the magnet-family strengths before handing them to the model

• Goal is to get config. model to agree with measurement


16

Fudge-Config Example


17

HER Steering

• The HER was steered in Jan. right after the xmas break

Steered HER; - target = flat everywhere (incl. Str. 10 on-axis, IR2 sexts), except: PR12 collimators, HTFB (reset to hitorical values) IP parameters (X = 1000 mu, Y = 3000 mu, XP = -16600 murad, YP = 1500 murad) - achieved: etay rms 19-20 mm, etay* = -1.7 mm. coupling = 1.5 kHz after restoring sym. component of IR2 sexts + decoupling w/ global skewsuads low-current collisions: CapSigMax * CapSigmin = 167 * 6.3 mu (23% gain in IP spot size)

PEPlog excerpt:


18


19

ßy* Reduction• In the HER, used quads at the far ends of Arcs 1

& 3 (Yuri knobs)– local chromaticity correction preserved

• In the LER, we cannot do that– Use Q{F,D}BM & fix chromaticity (MHD, JLT)

• Both worked successfully

• Both rings now close to ßy*=1 cm

• There is a question about the HER global ßy behavior: not as predicted from knob test.


20

HER before May-4 ßy* reduction

Note ßy* is 1.26 cm

HER before May-4 ßy* reduction


HER after May-4 ßy* reduction


HER after May-4 ßy* reduction



21

HER ßy* Knob—DesignM. Donald


22

Tune knob & ß beat

• HER tune knobs were characterized – calibration, ßx beat

• Calibration & orthogonality are good

• ßx beat changes significantly with x

– follows 1/(x-0.5)

• ßy beat does not change

-0.0200 -0.0150 -0.0100 -0.0050 0.00000.5000

0.5050

0.5100

0.5150

0.5200

0.5250

nu_x

nu_x Knob value

200 400 600 800 1000

5

10

15

∂ß/ß

1/(nu_x-0.5)

-0.0200 -0.0150 -0.0100 -0.0050 0.00000.5000

0.5050

0.5100

0.5150

0.5200

0.5250

nu_x

nu_x Knob value

200 400 600 800 1000

5

10

15

∂ß/ß

1/(nu_x-0.5)


23

90° HER Lattice

• Reduce bunch length to 83% comp. to 60°– momentum compaction .00241 -> .00168….0017

• Put beat back in => x=48 nmr

– Can probably be taylored to bunch current

• May keep µy at 60° => lower magnet strength

• Dynamic aperture is acceptable

• Power supply parameters determined


24

HER 90° Lattice Dispersion Yu. Nosochkov


25HER 90° Lattice Dynamic ApertureYu. Nosochkov


26

Some Open Issues

• HER coupling not quite right, needs fixing– (or is it needed to make vertical emittance?)

• HER ßy does not look like it should, why?

– QDS0XS appear to be able to fix this

• Where does the drift in ß(y) come from?

– given that we control the orbit well…

• Config model & ORM model in MAD get coupling wrong


27

More Issues…

• Once the config & ORM lattices are right(i.e. we have good fudge factors)– assess effect of the optics on beam emittance

• coupling, dispersion

– assess dynamic aperture of actual lattices– use these lattices to design knobs


28 (Pre-) Run 5 Optics Tasks

• I’d like to be in a position to– Steer the LER successfully

• => need strategy to deal with effect on ßx

– Fix ß beats in both lattices• probably essential to lower x -> 0.5

• may allow increased beam-beam tune shift

• requires a useable set of fudge factors

• We need ß*=33 cm/1 cm design lattices

• We need working x emittance knobs– no side effect on coupling or other plane

u. wienands, y. cai, f.-j. decker, m. donald, w. kozanecki, yu. nosochkov, t. raubenheimer, j....

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