orbit stabilization at the advanced photon source · horizontal: 5.0 microns / 1.0 microradians p-p...

Argonne National Laboratory DOE-BES ReviewGlenn DeckerMay 24, 2005

Orbit Stabilization at the AdvancedPhoton Source

Glenn DeckerDOE-BES Review

May 24, 2005

DOE-BES ReviewGlenn DeckerMay 24, 2005

er Distortion”)

tion upgrade

Argonne National Laboratory

Beam Stability Outline

• New beam stability specification

• Orbit control system overview

• DC Beam stability status and plans- Completion of girder displacement project (“deck- “Gold standard” hard x-ray bpm project

• AC Beam stability status and plans- Monopulse rf beam position monitor data acquisi


cation

s rmsns rms

nce / low coupling lattice

dians rms <----dians rms

f the source point in the

citly stated in the past.)

cification, PAC ‘95§


APS AC Beam Stability Specifi

Original Stability SpecificationEquivalent to 5% of Particle Beam Dimensions*:

Vertical: 4.4 microns / 0.45 microradianHorizontal: 16 microns / 1.2 microradia

Translating this 5% requirement to the present low-emittaresults in**:

Vertical: 0.42 microns / 0.22*** microraHorizontal: 3.0 microns / 0.53 microra

This specification gives the allowable rms beam motion ofrequency band 0.016 to 200 Hz.

(Note: The frequency band has typically never been expli

* Y.C. Chae, G. Decker, “APS Insertion Device Field Quality and Multipole Error Spe

** http://www.aps.anl.gov/asd/oag/SRSourceParameters/sourcePointResults/*** Includes photon angular divergence contribution, 7th harmonic, APS Undulator A


Data from Monochromatic X-ray BPM, 13ID


cationith period ranging from

adians p-p <----adians p-p

ory reproducibility speci-

--------------------------------ser at the 2004 user’s


APS DC Beam Stability SpecifiThe allowable amount of peak-to-peak source point drift w1 minute to 1 week (168 hours) is

Vertical: 1.0 microns / 0.50 microrHorizontal: 5.0 microns / 1.0 micror

This is also to be interpretted as the week-to-week trajectfication, e.g. following a machine studies period.----------------------------------------------------------------------------Compare this with dc stability “goals” stated by an APS umeeting:• Short term:

angular: vertical 1 µrad, horizontal 2 µrad,position: 5 µmover duration of run;

• Mid-term:angular: vertical 0.3 µrad, horizontal 1 µradposition: 3 µmover 1 year


C C

2 X2

X1

e-ID

C

x x

in One Sector

16m

20m

x

) (Turn-by-Turn)4) (~ 300 Hz)ical Only) (~165 Hz)Hz)


C C CCBMBM

X

X1

FC

Beam Position Monitors and Magnets

11m

18m

x

Q

x : Broad-band RF Beam Position Monitors (7 : Narrow-band RF Beam Position Monitors (

: BM X-ray Beam Position Monitors (2 - Vert : ID X-ray Beam Position Monitors (2) (~165 FC : “Fast” Corrector Magnet (1) (~ 1000 Hz)C : “Slow” Corrector Magnets (7) (few Hz)Q : Quadrupole Magnets


DC Beam Stability

• All sectors have now been realigned to reduce id x-bpm stray radiation back-ground, completing a 7-year effort.

• Photon bpm’s are used in DC feedback at all 19 bending magnet beamlines,and 17 out of 29 insertion device beamlines.

• Every insertion device straight section has 4 channels of narrowband rf bpmelectronics. Two have very high resolution using pickup electrodes mounted onsmall aperture ID vacuum chamber, the other pair are used for the missteeringinterlock.


ID photons

from down- quadrupoles,d correctors

er Alignment*


77 mrad

1 mrad

Stray radiation from upstreamdipole, quadrupoles, sextupolesand correctors

Stray radiationstream dipole,sextupoles an

Re-direction of Stray Photons by Gird

Phys. Rev. ST Accel. Beams 2, 112801 (1999)*


µrad

One-Week Angular Drift, ID Source Point*

Local Steering

* angles calculated from vertical ID xbpm readbacks, fixed gap.

500 nradSpecification


Correction of Residual ID Photon BPM Gap-dependent Systematic Errors

ID 20 Gap (mm) ID 20 Gap (mm)

ID 20 Gap (mm) ID 20 Gap (mm)

Background Subtraction Only Background + Exponent Corrections

∆x / Σ(Absolute)

∆x / Σ(Relative)

100 microns

approx. 40 microns

∆x / Σ(Absolute)

∆x / Σ(Relative)


Insertion Device Field Integrals vs. Gap(Rotating Coil Data)

500 nrad


Pointing Stability

rs

non-colinearity

used to generate lookup

tion, causing significant

problems, e.g. electron

particle beam is indeter-

ary to solve this problemesign to be tested at

to follow in 2006.


Summary of Factors Limiting Long-term

• Tunnel temperature +/- 0.1 degrees C is mandatory.

• ID photon bpm residual gap-dependent systematic erro

- Internal trajectory errors cause particle / x-ray beam

- RF bpm’s (measuring particle beam trajectory) aretables for ID photon bpm offset vs. gap

- Photon bpm’s are sensitive to bending magnet radiabackground signal, important at large ID gap.

- Sensitivity to ultraviolet radiation halo causes othercloud effects.

• The direction of the x-ray beam centroid relative to the minate at the few-µrad level using present technology.

- A diagnostic sensitive only to hard x-rays is necess- Funding has been approved to move forward on a d19ID in CY05, with a refined first production article


Beam-definingAperture

Water-cooledMoveable Scrapers

Shielded X-ray Detectors (4),Beryllium Filter

(Target: Cu or W)

X-rayFluorescence

Plan View of Hard X-ray Beam Position Monitor Concept

White ID X-ray Beam

InsertableFilter Array(C)(Fixed)

Above and Below Plane of Beam


AC Beam Stability

• The real time feedback system has been in operation since 1997.

• Makes use primarily of original monopulse rf bpm electronics.

• Provides powerful diagnostic of ac beam motion - 1.5 kHz sample rate, withaccess to virtually all beam position monitors and corrector magnet power sup-plies.


0.01 - 767 Hz

0.01 - 100 Hz

0.01 - 30 Hz

Horizontal RMS Motion Vertical RMS Motion

µmrms

µmrms

βx = 22 m βy = 6.9 m

~4 days

Long Term Stability of AC Beam Motion

Top-up operation, 24 singlet fill pattern

0.4 µmSpec.

3 µm H. Spec.

APS Real-time feedback system allows simultaneous acquisition of 40 waveforms


Power Spectral Density Sqrt[Integ[PSD]] Sqrt[ReverseInteg[PSD]]

µrad2/Hz

µrad2/Hz

Horz.

Vert.

µradrms

µradrms

µradrms

µradrms

with Feedback

Frequency (Hz)

AC Pointing Stability

without Feedback

Frequency (Hz)

Frequency (Hz) Frequency (Hz)Frequency (Hz)

Frequency (Hz)


s

rocessing technologies.5 kHz), a larger

tion of BH4 corrector toctor of two according to

re ongoing.

e narrowband and pho-precludes their effectiveed (CY05). ID photonn a user opens his gap).

l processing is archaic.enhance functionalityoise. Strategy is tokaged separately from


AC Beam Stability Plan

• A lot of relatively inexpensive fast network and signal pare available. This could allow a faster update rate (> 1response matrix, or some optimal combination.

• The addition of a second fast feedback corrector (relocaG3 spool piece) could improve noise rejection up to a fasome older simulation results. Further investigations a

• An over-aggressive design in the analog front end of thton beam position monitors (6-pole anti-aliasing filters)use in realtime feedback. These filters are being modifibpm gap dependence still an issue (e.g. what to do whe

• The monopulse rf bpm data acquisition and digital signaFunding has been approved to upgrade one sector, to (e.g. fast beam history feature), and reduce electronic nretain existing monopulse receiver front ends, to be pacthe new data acquisition (VXI format).


ary

/ week demonstrated,together with ID photon

d to overcome residualrad p-p / week goal.

rade options are underunds.

. Tunnel temperature iser the dominant source, e.g. low-level mechani-


APS Beam Stability - Summ

• DC beam stability is world-class, with sub-microradian and not unusual. High-resolution narrowband rf bpm’s,bpm’s have been critical in this effort.

• New technology (“gold standard hard x-bpm”) is needegap-dependent systematic errors, to achieve true 500 n

• AC beam stabilization hardware is showing its age, upginvestigation, with some efforts proceeding with ARIM f

• Passive source identification and mitigation will continuebecoming a limiting factor. Power supplies are no longof ac noise. Search for other mechanisms will continuecal vibration.


Backup Viewgraphs


Air Temp (deg. F)

8ID V. Angle (µrad)

8ID H. Angle (µrad)

Local Tunnel Air Temperature Impacts Pointing Stability


Variation of Particle Trajectory Through Insertion Device vs Gap

(Derived from Second Field Integral of Magnetic Measurement Data)

X (

mic

rons

)X

(m

icro

ns)

X (

mic

rons

)X

(m

icro

ns)


Power Spectral Density Sqrt[Integ[PSD]] Sqrt[ReverseInteg[PSD]]

µm2/Hz

µm2/Hz

Horz.

Vert.

µmrms

µmrms

µmrms

µmrms

APS

APS,SPring-8*

Frequency (Hz)

Normalized toβx = 20 meters

Normalized toβy = 5 meters

AC Beam Stability

(No Feedback)

Frequency (Hz)

Frequency (Hz) Frequency (Hz)Frequency (Hz)

Frequency (Hz)

*Spring-8 DataCourtesy H. Tanaka

orbit stabilization at the advanced photon source · horizontal: 5.0 microns / 1.0 microradians p-p...

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