Recent MIA Results

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Recent MIA Results
PEP-II MAC meeting April 16, 2004

• Yiton T. Yan
• Stanford Linear Accelerator Center

Acknowledgement Y. Cai, F-J. Decker, S.
Ecklund, J. Irwin, J. Seeman, M. Sullivan, J.
Turner, U. Wienands, etc.
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Outline

• Part I. MIA review
• Buffer data acquisition
• Four independent orbits
• phases, beta functions, Greens Functions, Eigen
  ellipses
• Enhanced SVD-enhanced fitting fast fitting
  process
• Typical MIA results (plots) - some shows current
  LER optics
• Virtual and wanted accelerators MIA flow chart
• Part II. Recent Application to PEP-II
• HER Beta Beat studies
• Dynamic Beta from Beam-Beam effect
• Optics study on LER steering machine
• Summary

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Buffer data acquisition

• Resonance excitation to offset radiation damping
  by a shaker at the horizontal betatron (eigen)
  tune and then at the vertical tune, each for
  about 1000 turns to get a complete set of data.
• Buffer data are stored in two sets of matrices,
  each set has two matrices, one for the x data and
  the other for y data.

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4 independent orbits determines the linear optics.
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Phase Advances
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This is before MIA fitting
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Preliminary beta function survey
by
bx
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The linear Greens functions
They, along with the phase advances are used for
SVD-enhanced fitting to obtain a virtual
accelerator
Where, in the measurement frame, R is a function
of BPM gain and BPM cross-plane coupling.
Q12 and Q34 are the two invariants representing
the excitation strength
MIA does not trust the BPM accuracy MIA figures
out BPM gain and cross coupling errors.
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MIA can figure out BPM errors(recall Steve
Smiths morning talk
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Summary of the measurable quantities (derivable
from the 4 orbits)

• The phase advances among BPMs.
• Greens functions R12, R34, R32, R14 among BPMs.
  Use of 6, , 18, 30 greens
• Eigen Ellipses parameters for all double-view
  BPMs tilt angles and axis ratios.
• Form these measurable quantities into a sequence
  (a single vector) for easier Least-squares
  fitting.
• Linear coupling are completed treated without any
  discount.
• Eigen ellipses parameters may not be used in
  fitting but be reserved for checking fitting
  accuracy.

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Summary of variables

• All quad families normal components.
• All skew (global and local) quads skew
  components.
• All sextupole feed-downs normal and skew
  components.
• All BPM gains and cross couplings.
• Additionally, all quad skew components and all
  skew quad normal components.
• Also form all these variables into a sequence (a
  single vector with data-structure pointers).

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Enhanced SVD-enhanced Least Square fitting
Need about two iterations of enhanced
SVD-enhanced fittings.
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Typical MIA results (plots)

• In the next pages we show the following plots
• Phase advance comparison plots
• Beta function plots
• Linear coupling plots at IP
• eigen ellipse tilt angles and axis ratios plots
  for fitting accuracy checking
• Linear coupling appraisal plots

This is a complete set of linear optics (10
degrees of freedom) parameters. You can NOT get
any more than this.
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(No Transcript)
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A typical ?-function plots from MIA close to
the current PEP-II LER
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A typical linear coupling plots near IP current
PEP-II LER
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Check MIA fitting accuracyAre eigen ellipse
tilt angles and axis ratios automatically matched?
Yan/mia/ler/2004/OCT28/1
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A complete appraisal of the LER linear coupling
LER/2004/OCt28/1
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MIA flow chart
10 - 15 minutes collecting MIA data, 3 minutes
Phase advances and Beta function, dispersion
measured and bad BPMs identified
6 minutes MIA fitted with 6 greens for more
accurate beta functions
20 minutes virtual accelerator obtained with 18
greens
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MIA was applied to improve PEP-II
MIA came to work at the right time when SLAC
PEP-II B-factory desperately needed advanced
optics improvement in order to meet the promised
performance progress.
MIA successfully brought LER to a half integer
working tune and improve LER beta beats and
linear coupling. Instantly, LER beam became the
stronger one of the two (LER and HER beams).
Indeed LER became way too strong for the HER.
Nonetheless, consequently, PEP-II achieved its
record peak luminosity at 6.5 X 1033 /cm2/s in
June 2003. It is still a single-bunch luminosity
record.
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HER optics after adjusting to match the very
strong LER
One can see a strong ?X beat that is over 100
with a small ?X at about 27 cm.
The ?X beat can be fixed by tune trombone
global skews with MIA, but the ?X will be
restored to 50 cm.
We want the ?X be small while the large beta
beat be fixed.
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Part II Recent application to PEP II

• A knob for adjusting HER beta beat while changing
  IP beta.
• Tried to fix the HER beta beat with beta bumps.
• Optics study on LER steering machine

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HER virtual machine before dialing in MIA knob of
only the trombones and the global skews on Nov. 4
Beta beat has increased by additional 100
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Dialing the MIA knob into the virtual machine
showed that the HER could be brought back to low
beta beat but restored to near the original
design ?X value of 50 cm.
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HER virtual machine after dial-in of the MIA beta
beat knob.
It shows very much the same as predicted by
dialing the knob into the MIA virtual machine
Proving MIA is a very accurate optics measurement
tool.
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HER Beta Beat fixes based on virtual HER of 3
Feb. 2004
Beta Beats on 4 of the 6 arcs are completely
fixed while the remaining 2 arcs adjacent to IP
are set up with beta bumps to offset the extra
chromaticity generated by the large doublet
betas. Sextupole strengths may need to be
adjusted slightly to optimize the chromaticity.
But we need to understand why the beam life time
is not good.
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We have Much improved HER BPMs

• Excellent MIA data for excellent measurement
  and reliable MIA virtual machine

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Beta Y function directly measured by MIA without
fitting, showing that PEP-II HER BPMs have been
much improved.
It takes a couple of minutes to get this plot
after MIA data taken.
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Beta X function directly measured by MIA without
fitting can immediately show the quality of beta
beating. This plots can be obtained within a
couple of minutes once MIA data are obtained.
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Virtual HER obtained from 3 Feb, 2004 MIA data
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MIA fitting is very good and HER linear coupling
is very good.
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MIA knob for fixing HER beta beat while keeping
IR region the same (low Beta X) and chromaticity
Ok with beta bumps.

Trombone
QDS0XSR1 -2.1010 QFS1SR01
5.5864 QDS1SR01 -0.1576 QFS2SR01
-3.3181 QDS2SR01 1.0638 QFS3SR01
0.1786 QF5L -0.0991 QF5R
-0.1454 QFS3SR03 1.3990 QDS2SR03
-0.1545 QFS2SR03 -1.3835 QDS1SR03
-1.3727 QFS1SR03 6.7953 QDS0XSR4 -3.2147
QFP9R04 1.7714 QDP8R04 -1.0815 QFP7R04
1.1231 QDP6R04 -0.9091 QFPL
-0.4119 QDPR 1.2902 QFP9R06
-3.0042 QDP8R06 -0.1718 QFP7R06
-1.3743 QDP6R06 0.2992 SQG2
-0.5097 SQG1 0.8352 SQG4
0.1265 SQG3 -0.0556
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Wanted HER approachable from the Real HER with a
MIA konb
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MIA knob generated wanted HER keeps linear
coupling the same if not better.
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Comparing the IP Betas
Top plots the virtual HER on 3 Feb. 2004
Bottom plots after dialing in the knob.
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Comparing IP region
Top plots the virtual HER on 3 Feb. 2004.
Bottom plots after dialing in the knob
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Comparing Beta functions
Top plots the virtual HER on 3 Feb. 2004
Bottom plots after dialing in the knob
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Virtual HER after 75 dialed-in of the knob
Beta beats in 4 arcs are almost fixed while beta
bump is kept
Linear coupling is improved
Unfortunately, there is no 100 dial-in MIA data.
Martin Donald got his data for 100 dial-in that
show very much as expected results as predicted
by the virtual dial-in.
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Summary for MIA HER beta bump knob

• This knob seems to go in the right direction. Do
  not give it up easily.
• Indeed, this is the kind of solution we have been
  looking for (a) keeps the same small Beta X at
  IP (b) beta beat fixes (c) Chromaticity is all
  right.
• Need to understand why beam life time is not good.

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Dynamic Beta from Beam-Beam effect

• John Seeman suggests putting a lens at IP to
  represent beam-beam effect in MIA virtual HER.
  Here are the results.

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Beta beats ----Adding beam-beam effect lens on
Virtual HER of 3FEB2004
No Beam beam
2/7 Beam beam
Full Beam beam
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Dynamics Beta ----- Adding beam-beam effect lens
on the Virtual HER of 3FEB2004
No beam beam
2/7 beam beam
Full beam beam
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Optics study for the LER Steering, MD data on
2-11-2004
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Virtual machine of the steering LER, MD on
2-12-2004
gt200 beta beat
Large IP waist shift
Bad Coupling shown on the right
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Work in progress for LER steering machine optics
improvement
Beta beat much improved
IP waist shift left alone tentatively
Knob involves trombone quads, global skews, and 4
pairs of local skews (SK2,3,4,5 R,L)
Coupling improved. Need further improvement
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Summary

• MIA has been used in weekly basis for studying
  the PEP-II accelerators optics IP betas, linear
  couplings, beta functions (beta beats) etc.
• MIA has helped PEP-II improve the machines
  optics, bringing LER working tune to near half
  integer while fixing its beta beat and reducing
  its coupling, to reach a record single peak
  luminosity.
• MIA has been tested very positively for HER.
  Hopefully soon or later HER super large beta beat
  will be fixed. However, PEP-II is fine with this
  high beta beat in HER not in a hurry.