Online Models for PEP-II Status
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Transcript of Online Models for PEP-II Status
PEP-II MAC December 2004 Mark Woodley (ILC) 1
Online Models for PEP-IIStatus
• brief review of PEP modeling• fully coupled “normal form” optics representation• Orbit Response Matrix (ORM) model calibration:
“fudge factors” for quadrupole strengths• continuing work
PEP-II MAC December 2004 Mark Woodley (ILC) 2
PEP Online Modeling: Procedure
• prepare input files for MAD
–read reference input files–set magnets to configuration file values–apply ORM-derived fudge factors to quadrupole strengths
• run MAD
–use XCORs and YCORs to steer to measured absolute orbit–compute “effective” transfer matrices (RMATs)
• generate model files for MCC
–extract coupled lattice functions from RMATs
PEP-II MAC December 2004 Mark Woodley (ILC) 3
PEP Online Modeling: ProcessMCC (VMS) pepoptics (linux)
Database
SCP
LERmodelHERmodel
Matlab
MADinput
ReferenceFiles
MAD
AT
LEGO
AT
InputFiles
Magnets,Orbit,
Fudges
ConfigurationFiles
Magnets,Orbit,
Fudges
ConfigurationFiles
RMATs,Twiss,nij
Model Files
SCP,SSH
11
1
2
3
4
5
6
78
9
10
DIMADnot usedanymore
MADupdated tov 8.51/15
RMATs,Twiss,nij
Model Files
PEP-II MAC December 2004 Mark Woodley (ILC) 4
Lattice parameters in highly coupled systems
• MAD (v 8.51/15-SLAC) has been modified to output “effective” transfer matrices (first order expansion about the closed orbit; includes “feed down” effects from sextupoles)
• Andy Wolski’s normal form analysis1 is used to extract coupled lattice parameters from the transfer matrices
• 10 coupled lattice parameters (μ, β, α, η, η΄ for modes 1 & 2) and 8 elements of the normalizing transformation (n13, n14, n23, n24, n31, n32, n41, n42) at each element are returned to be loaded into the MCC database
1See http://www-library.lbl.gov/docs/LBNL/547/74/PDF/LBNL-54774.pdf
PEP-II MAC December 2004 Mark Woodley (ILC) 5
ORM analysis: LER• ORM analysis begins with the “config” lattice (actual magnet strengths,
steered to the measured absolute orbit)
• only quadrupole strength errors are fitted (no sextupole strength errors)
• errors are assigned to quadrupole families (power supplies)
• sextupole “feed down” effects are not explicitly fitted (even though they are important for LER) … the assumption is that the BPMs are correct (BBA) and that steering to the measured orbit is sufficient to model the feed down effects
• “fudge factors” are computed by comparing the fitted quadrupole strengths with their config values; normal quadrupole fudge factors are multiplicative; skew quadrupole fudge factors are additive (since most skew quads should nominally be at or near zero)
• the actual ORM analysis for LER is performed by Cristoph Steier (LBNL) using the Matlab-based version of the LOCO program
See PT’s presentation on Recent ORM Results for further details …
PEP-II MAC December 2004 Mark Woodley (ILC) 6
ORM-derived fudge factors: LER (1)
•normal quadrupoles
•skew quadrupoles
1
1
1ORM
config
Kf
K
1 1ORM configf K K
QDBM6L
ORM data taken on December 11, 2003
PEP-II MAC December 2004 Mark Woodley (ILC) 7
( )( )calcxmodelx
fudgedunfudged
ORM-derived fudge factors: LER (2)
fudgedunfudged
( ) ( )meas modelx x
PEP-II MAC December 2004 Mark Woodley (ILC) 8
( )
( )
calcymodely
fudged
unfudged
ORM-derived fudge factors: LER (3)
fudged
unfudged
( ) ( )meas modely y
PEP-II MAC December 2004 Mark Woodley (ILC) 9
ORM-derived fudge factors: LER (4)
PEP-II MAC December 2004 Mark Woodley (ILC) 10
ORM-derived fudge factors: HER (1)
•normal quadrupoles
•skew quadrupoles
1
1
1ORM
config
Kf
K
1 1ORM configf K K
ORM data taken on June 10, 2004
PEP-II MAC December 2004 Mark Woodley (ILC) 11
( )( )calcxmodelx
fudgedunfudged
ORM-derived fudge factors: HER (2)
fudged
unfudged
( ) ( )meas modelx x
PEP-II MAC December 2004 Mark Woodley (ILC) 12
( )
( )
calcymodely
fudgedunfudged
ORM-derived fudge factors: HER (3)
fudgedunfudged
( ) ( )meas modely y
PEP-II MAC December 2004 Mark Woodley (ILC) 13
ORM-derived fudge factors: HER (4)
PEP-II MAC December 2004 Mark Woodley (ILC) 14
Continuing work• steering to absolute orbits when generating the model in order to properly
account for sextupole feed down effects requires accurate knowledge of BPM offsets → BBA1; many offsets for both HER and LER have been measured and are being routinely used to correct measured orbits; LER BBA is ongoing (more on this in a minute …)
• continue to fine tune the ORM analysis setup to avoid degeneracy in the variables
• fudge factors for individual magnets (?)
• develop more robust steering algorithms for model generation to take into account bad BPMs (especially for LER)
• create “fudged” design configs … move toward design optics in both rings
• participate in the ILC design1See Tonee Smith’s presentation on New BBA Hardware for further details …
PEP-II MAC December 2004 Mark Woodley (ILC) 15
BBA at PEP-IIStatus
• large unexplained LER BPM offsets from BBA → uncoupled analysis of orbits in a highly coupled machine
• new analysis algorithm• BPM offsets revisited
PEP-II MAC December 2004 Mark Woodley (ILC) 16
Unexplained large (~1 cm) LER BPM offsets from BBA
… from Marc Ross’ summary at April MAC …
PEP-II MAC December 2004 Mark Woodley (ILC) 17
• orbit fitting lies at the heart of our BBA analysis algorithm
• move the beam in a quadrupole (using a closed bump), change the strength of the quadrupole, and look at the orbit change
• if the orbit doesn’t change when the quadrupole strength is changed, the beam is passing through the center of the quadrupole; the reading on a nearby BPM under these conditions is the “BPM offset”
• if you’re moving the beam in X, you look at the change in the X orbit, which should be proportional to the distance (in X) between the beam and the quadrupole center … in an uncoupled ring
• if you’re moving the beam in X, and the beam happens to be offset in Y to begin with, the previous statement remains true … in an uncoupled ring
• if you’re moving the beam in X, and the beam happens to be offset in Y, and your ring is highly coupled, you have to pay attention to what’s happening in both planes simultaneously (well duh)
BBA Analysis
PEP-II MAC December 2004 Mark Woodley (ILC) 18
QDBM3 simulated X data-10 mm Y offset
uncoupled orbit fit
Δx
(mm
)
blue – o = MADred - - = orbit fit
PEP-II MAC December 2004 Mark Woodley (ILC) 19
PEP-II MAC December 2004 Mark Woodley (ILC) 20
BBA Analysis
PEP-II MAC December 2004 Mark Woodley (ILC) 21
Change in closed orbit (Δxco,Δyco) due to a change in strength (K→K(1)) of a
misaligned quadrupole (xbq,ybq):
†A. Wolski and F. Zimmerman, “Closed Orbit Response to Quadrupole Strength Variation”,
http://www-library.lbl.gov/docs/LBNL/543/60/PDF/LBNL-54360.pdf
bq
bq
co
co
y
xssCKssCKssCK
sy
x 1
0000)1()1( ;1;;
quadrupoleskew
quadrupolenormal
,
,
;
;1;;
3234
1214
3432
1412
0
10000
CC
CC
CC
CC
ssC
ssRssRssC
includes closed orbit effects of ΔK (both kick and position shift) includes optics effects of ΔK (change in closed orbit response matrix) fits both planes simultaneously, including any known coupling
Coupled BBA Analysis Algorithm
PEP-II MAC December 2004 Mark Woodley (ILC) 22
Δx
(mm
)Δ
y (m
m)
QDBM3 simulated X data-10 mm Y offsetcoupled orbit fit
PEP-II MAC December 2004 Mark Woodley (ILC) 23
LER BPM X Offsets: Then and Now
PEP-II MAC December 2004 Mark Woodley (ILC) 24
LER BPM Y Offsets: Then and Now
PEP-II MAC December 2004 Mark Woodley (ILC) 25
Acknowledgements & thanks!
Andy Wolski, Christoph Steier
James Safranek, Andrei Terebilo
Yuri Nosochkov, Yunhai Cai, Yiton Yan
Uli Wienands, Jim Turner, Martin Donald, Gerry Yocky
Peter Tenenbaum, Marc Ross, Janice Nelson, Tonee Smith