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Online Models for PEP-IIStatus and Plans

• online modeling process and procedure

• “Twiss” parameters in highly coupled systems

• recent updates to the LER model

• continuing work

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PEP Online Modeling: ProcessMCC (VMS) pepoptics (linux)

Database

SCP

LERmodelHERmodel

MatlabTwiss,RMATs

Model Files

DIMAD

MAD,DIMADinput

ReferenceFiles

MAD

AT

LEGO

BMAD

InputFiles

Magnets,Orbit

ConfigurationFiles

Magnets,Orbit

ConfigurationFiles

Twiss,RMATs

Model Files

SCP,SSH

11

1

2

3

4

5

6

78

9

10

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PEP Online Modeling: Procedure• read reference input files; set magnets to configuration file values• [MAD] use XCORs and YCORs to steer to measured absolute orbit• [MAD] compute coupled Twiss parameters• [DIMAD] compute transfer map about the closed orbit• generate model files for MCC

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Twiss parameters in highly coupled systems

• MAD finds coupled Twiss from eigenmodes of transverse motion (“Mode 1” and “Mode 2”); association of these modes with the horizontal and vertical planes can become ambiguous when the coupling is large, leading to “mode flipping” and negative (or infinite) beta functions

• so far this effect has only been observed in the LER model

• Andy Wolski has suggested an alternative representation, based on normal form analysis1, that is directly related to the horizontal and vertical projections of beam distributions and betatron oscillations; defined in this way, the beta functions remain “well behaved” (positive and finite) under all circumstances

• “Wolski” coupled Twiss parameters are computed from DIMAD’s fully coupled transfer matrices and returned to MCC

1See http://www-library.lbl.gov/docs/LBNL/547/74/PDF/LBNL-54774.pdf

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Recent Updates to the LER Model• interaction region element positions (Precision Alignment Group meets

machine physicists with tape measures)

• QD1/QF2 interaction with BaBar solenoid

• we now use DIMAD v2.9, which has a more MAD-like input syntax → allows us to use minimally modified reference decks as input to both programs (applies to the HER model, as well … )

create LER-200403.mad from ler-200307.mad and ler-200309.mad

- suppress TITLE, ASSIGNs, OPTIONs, and BEAM definition- change: "BB+" to BBplus; "BB-" to BBminus; "BW1+" to BW1plus; "BW1-" to BW1minus; "BW2+" to BW2plus; "BW2-" to BW2minus; "LL*" to "LLstar"- set BCC1LC[E2]=0, BCC1LB[E1]=0, BBA[E2]=0, BBB[E1]=0- split BBM1L, BCC4L, BCC4, and BBM1 in half; move THCOR to center of each; add soft fringe definitions- add THCOR at center of HK1 and HK1L- define TVCOR- add THCOR and TVCOR to QD1L and QD1R (between "A" and "B" slices)- add TVCOR to BM1, BM2, BM1L, and BM2L (center)- add DBMARK66 (center of region 8 straight), MSTEER (center of BM1R), and DBMARK51 (at IP)

create LERcorbpm.mad and rLERcorbpm.mad from corbpm.ler.mad

- add THCOR and TVCOR replacement lists

create HER-200307.mad from her-jul03.50-1.25.mad

- suppress TITLE, ASSIGNs, OPTIONs, and BEAM definition- define THCOR and TVCOR- split BLF and BLFM in half; add THCOR at center of each; remove BLFMCOR and BLFCOR- add THCOR and TVCOR to QD1L and QD1R (between "A" and "B" slices)- add DBMARK56 (center of region 10 straight), DBMARK23 (at SYNCSRC[2]), and DBMARK51 (at IP)- change QF5(L/R) from zero-angle SBENDs with nonzero K1s to QUADRUPOLEs- add TVCOR to BM2L, BM1L, BM1R, and BM2R

create HERcorbpm.mad from corbpm.her-nov02.mad

- add THCOR and TVCOR replacement lists

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device delta S distance from (mm) IP (m)-------------- ------- -------------QUAD SK4 -97.0 -50.492QUAD QDCY2 -8.0 -30.966YCOR PR02 3072 70.0 -23.240XCOR PR02 3064 -60.0 -21.133BPM PR02 3041 38.8 -9.438QUAD SK2 -55.0 -9.203XCOR HK1B -32.4 -8.041YCOR PR02 3024 -2.4 -5.643BPM PR02 3024 -2.4 -5.513QUAD SK1 -2.4 -3.491QUAD SK1L -0.4 3.519BPM PR02 2203 -0.4 5.513YCOR PR02 2202 -0.4 5.840XCOR HK1AL 29.6 8.039YCOR PR02 2186 6.9 8.986QUAD SK2L 33.9 9.219BPM PR02 2185 -37.8 9.438YCOR PR02 2152 39.9 23.459SEXT SCX2L -5.1 27.005QUAD SK3L 15.9 27.510YCOR PR02 2092 -118.1 44.687QUAD QDCY2 -8.1 45.129QUAD SK4L 83.9 50.482BPM PR02 2062 -7.1 50.697QUAD QFBM1L -7.1 51.045QUAD QDBM2L -7.1 51.875BPM PR02 2056 -7.1 52.238YCOR PR02 2056 -7.1 52.496

LER IR Element Positions

1. Generate “online” model (config/orbit) using original element positions; compute beta functions

2. Paste magnet/corrector strengths into a deck with updated element positions; compute beta functions

3. Plot the ratio βnew / βold

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QD1/QF2 interaction with BaBar solenoid

Detectorsolenoid

(old)

(new)

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Extent of BaBar Solenoid Field

ABC A B C

“LEFT” side “RIGHT” side

strength of QD1 permanent magnet blocks suppressed by ~1% in the solenoidal field

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Continuing work• Andy Wolski and Marco Venturini at LBL have implemented an integrator for a

combined solenoid/dipole/quadrupole element (presently available only for Andrei Terebilo’s AT simulation code … )

• steering to absolute orbits when generating the model requires accurate knowledge of BPM-to-magnet-center offsets → BBA; many offsets for HER have been measured and are being routinely removed from measured orbits; LER BBA is ongoing (see Marc Ross’ talk … )

• MIA and ORM analyses are finding errors in our models of HER and LER (see talks of Yiton Yan and Christoph Steier … ); need to fold these results back into the models to make the models more predictive of actual beam behavior

• David Sagan’s BMAD program has been ported to SLAC and is now running in both our linux and Windows environments; we are setting BMAD up to do real-time analysis and correction of dispersion and coupling in both rings (see Martin Donald’s talk for related details … )

• automated generation of LEGO input files from the online models is being tested; AT is already able to use the online models

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• in the presence of the BaBar solenoid field, the element sequence at the IP in the LER model:

(QF2R,D2R,QD1R,D1R,B1R,D0R,D0L,B1L,D1L,QD1L,D2L,QF2L)

requires 1131 MAD PARAMETERs, 178 SOLENOIDs, 98 MULTIPOLEs, 46 HKICKs, 178 VKICKs, and 80 BEAMLINEs

• use of the SOLDIPQUAD element reduces this to a total of 18 definitions (!)• need to integrate this new element into MAD and DIMAD

Combined Solenoid/Dipole/Quadrupole Element

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BMAD (Windows, HER lattice)

BMADMAD

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Acknowledgements & thanks!

Andy Wolski, Christoph Steier, Marco Venturini

James Safranek, Andrei Terebilo, Jeff Corbett

CESRDavid Sagan, Mark Palmer

Yuri Nosochkov, Yunhai Cai, Yiton Yan

Uli Wienands, Mike Sullivan, Martin Donald, Jim Turner, Gerry Yocky, Artem Kulikov

Tor Raubenheimer, Peter Tenenbaum, Marc Ross