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Characterization of
Fast Orbit Feedback System
Om Singh, APS, ANL
NSLS-2 Beam Stability Workshop
BNL, April 18-20, 2007
2Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Outline
Bpm & Magnet Layout – One SR Sector
AC Beam Stability
Goals & Present Performance
Orbit Feedback Sub-systems
Resolution & Responses
Digital Process Rate & Orbit Correction Configuration
Summary & Upgrade Plans
Photo
3Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
27.6 Meters
Number of sectors = 40 Circumference = 1104 m
Transverse Tunes νx= 36.2, vy = 19.27 Energy = 7 GeV
Beam Current = 102 mA RF Frequency = 352.194 MHz
Revolution Frequency = 271.554 KHz Harmonic number = 1296
One Sector of the Advanced Photon Source Storage Ring
4Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Beta Functions
5Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
X-Ray Beam Position Monitors
Photo -emission sensory blades Excellent thermal insulation
and vibration damping Beam Position Measurement BW
up to Tens of KHz
One Sector - Cartoon
Bending Magnet
SlowCorrectionMagnet
FastCorrectionMagnet
Monopulse BPM – turn by turn (AM/PM)
Up to 8000 turn-by-turn samples of beam history - @ ~ 271 KHz Averages to 50 Hz, 2 Hz, 0.03 Hz BW
Sector N
Narrowband (Switching) BPM
Small Bunch Pattern & Intensity Dependence (vs Mp bpm) High Reliability and easy maintainability Beam Position Measurements BW up to ~ 5KHz
EllipticalChamber PUEs
ID ChamberPUEs
ID Device
Beam Position Monitors and Dipole Magnets
6Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
AC Beam Stability Goals
SR Emittance εe= 3.1 nm; coupling = 0.8%
1. Presently σx = 280 μm; σy = 10 μm; σ’x = 12 μrad; σ’y = 3 μrad
Beam stability goal and present performance
1. Stability goal* (AC) 5% of the APS beam size/ divergence
Goal / Present Performance
x, y (μm rms ) x’, y’ (μrad rms )
Goal (0.017 – 200 Hz) 14.0, 0.5 0.60, 0.22**
Present (0.017 – 200 Hz) 6.0, 2.0 0.26, 0.34
Broadcast (0.017 – 30 Hz) 0.8, 0.6
*G. Decker presented to 2005 DOE-BES Review at APS** Includes photon divergence contribution, 7th harmonics, APS undulator A
7Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
AC Stability @ ID’s Sources
4um
1.5um
Correction BW
8Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
AC Pointing Stability @ ID’s SourcesPower Spectral Density Sqrt[Integ[PSD]] Sqrt[ReverseInteg[PSD]]
rad2/Hz
rad2/Hz
Horz.
Vert.
radrms
radrms
radrms
radrms
with Feedback
Frequency (Hz)
without Feedback
Frequency (Hz)
Frequency (Hz) Frequency (Hz)Frequency (Hz)
Frequency (Hz)
* G. Decker – DOE-BES Review 2005
220 nrad
Spec
9Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Global 1.5 KHz Processing Architecture
20 Double Sector Processors
1 Master Processor
1 IOC Processor(Datapool) Reflective
MemoryNetwork
10Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Orbit Feedback - Subsystems
Subsystems & Performance Limiting Factors
1. BPM/ Corrector - Resolution 2. BPM/ Corrector - Responses
3. DSP Processing Power - Process Rate & Orbit Correction Configuration
11Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Beam Motion @ ID Source vs Bpm Resolution (Noise)
Cumul RMS 30 Hz band (H & V)
Beam Motion = 0.8 & 0.6 micron RfBpm Noise = 0.3 & 0.35 micron Faster digitization should lower noise floorXBpm Noise = 0.04 & 0.04 micron Low noise level, but so far only in DC orbit feedbackDigitizer Noise = 0.01 & 0.01 micron
30 Hz Band 30 Hz Band
12Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
BPM / Fast Corrector – Responses
BPM Response
One pole low pass filter @ 2KHz
Fast Corrector Response
One pole low pass filter @ 1.5 KHzDelay ζ = 0.2 ms
BPM & Fast Corrector Combined Phase Contribution
@ 100 Hz = 15o
@ 200 Hz = 27@ 300 Hz = 45@ 400 Hz = 57@ 500 Hz = 70
13Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Orbit Feedback - Limitations
Digital Signal Processor -
Present hardware allows to process up to 1.5 KHz sample rate – limits orbit correction BW to 50-90 Hz
Up to 4 Bpms per sector are included due to processing time constraint
Study in progress to include Xbpms
Corrector
Only one corrector (A3) available with fast response – limits orbit correction
A second fast corrector is required for optimal orbit correction – simulation shows further noise reduction by ~ 2.5
RF
Bp
ms
XB
pm
s
Fast Corrector
14Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Optimized Overall O. L. Responses (Vert) – 1.5 KHz vs 15 KHz
Optimized parameters @ 1.5 KHz s.r.
Digital Process Rate = 1.5 KHz Digitization Phase = (f/fs) * (360deg)
Regulator 1 HPF @ 0.07 Hz 1 LPF @ 25 Hz Gain = 4
Orbit Correction Bandwidth 100 Hz
Optimized Parameters @ 15 KHz s.r.
Digital Process Rate = 15.0 KHz Digitization Phase= (f/fs) * (360deg)
Regulator 1 HPF @ 0.105 Hz 1 LPF @ 75 Hz Gain = 6
Orbit Correction Bandwidth 400 Hz
o oUnit gain line
15Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Summary – Stability Goals, Status & Plans
Beam Size/ Divergence
StabilityGoals
Stability Status
Meet Goals (yes/no)
x µm 14 6.0 yes
y µm 0.5 2.0 no
x’ µrad 0.6 0.25 yes
y’ µrad 0.22 0.35 no
Proposed Upgrade Plans
Add 2nd fast corrector per sector - simulation shows noise reduction factor is 2.5 Increase process rate ten-fold > 15 KHz - AC obit correction BW to 400 Hz Improve RfBpm noise floor – increase digitization rate Include Xbpms in fast orbit feedback
AC Beam Stability (0.017 – 200 Hz)
- Horizontal beam stability goals are met- Vertical beam stability requires a factor of ~ 4 improvement
16Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Bpm/ Corrector In-Use Status – Orbit Feedback
RF
BPMs
Xbpms
Fast Corr
Configuration Layout – L. Erwin
HorizontalVertical
17Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Photo
18Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
In Tunnel BPM Hardware (Rf Bpms)
Elliptical Chamber Buttons & Matching Networks
Filter & Comparator
Small Gap Chamber Buttons
Photo – M. Hahne
19Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
In Tunnel BPM Hardware (Xbpms)
* Deming Shu -APS
Xbpm Main Assembly
X-YTranslation
Stages
Mounting Stand
Xbpm Blades Assembly
20Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
BPM Front-End Electronics and Processors – Two Sectors
Patch Panel
Pre-Amps
Filters &Controls
Narrowband RFbpms
AM/PM RFBpms
FDBK Processors
BPM IOC
16 Bits ADCs
X-ray BPMs Interface
RF Bpms & Processors
Photos by M. Hahne
Outside Tunnel Hardware
21Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
Acknowledgement
To
All APS members for contribution
to support ongoing Beam Stability work
22Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
BPM Hardware Development Highlight RF Bpms
1. Mpbpm data acquisition* upgrade in progress, using fast 88 MHz A/D and FPGA
technology; can provide bunch by bunch position data
2. Evaluation of yet another kind BPM in progress from Instrumentation Technology
(Libera) – ALL digital bpm with direct sampling of each button RF signals. Two
units are in hand & evaluation with beam to follow
Photoemission type - Xbpm
1. BM Xbpm – extremely reliable; used in DC Orbit control routinely
2. ID Xbpm – “Decker distortion” has been completed redirecting unwanted stray
radiations away from ID radiations. Provides beam measurement to sub-micron
level at fix gap. When gap varies, photon beam measurement held to tens of
microns with feedforward algorithm
Xbpm – hard X-ray type Bpm under development; to resolve to sub-micron level even
with ID gap change; has potential for beamline alignment gold standard
23Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
ID photons
77 mrad
1 mrad
Stray radiation from upstream dipole, quadrupoles, sextupoles and correctors
Stray radiation from down-stream dipole, quadrupoles, sextupoles and correctors
Re-direction of Stray Photons by Girder Alignment*
Phys. Rev. ST Accel. Beams 2, 112801 (1999)* (G. Decker)
24Characterization of Fast Orbit Feedback System – APS, ANL Om Singh NSLS-2 Beam Stability Workshop, April 18-20, 2007
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
* G. Rosenbaum & G. Decker
*