User's Requirements for Orbit Stabilization (2.2MByte)
T. Ishikawa /SPring-8
Stable SR beams are essential for most of the users' activities.
In this talk are discussed some examples (i) why the beam stability is
important for users' activity, (ii) how the better stability improve users'
results, and (iii) what kinds of sciences proceed with further stability
of the beam.
Status of Beam Stabilization at ESRF (1.3MByte)
L. Farvacque /E.S.R.F
Orbit Stabilization at SPring-8 (2.6MByte)
H. Tanaka /SPring-8
SPring-8 is a third generation X-ray source and hence beam orbit
stability is one of the most crucial issues for the best use of spatially
sharp photon beams. Since the beam commissioning year of 1997, we have
been making various efforts to stabilize beam orbit in the SPring-8 storage
ring.
However, good stability of sub-micron level is not easily obtained
due to the complexity of beam orbit variations. Various kinds of sources
widely distributed over the ring mainly cause this complexity. To overcome
this, it is essential that equipment, utility systems, beam controls, a
building structure and so on are improved and reintegrated from the total
viewpoint of orbit stability. We thus started a project on beam orbit stabilization
in the storage ring aiming at sub-micron stability at the beginning of
year 2001. Many members having different specialties joined to the project
team to tackle with this difficult task. We have not reached to our destination
yet, but with the activities during these two years, we made a big progress
on the stabilization of fast orbit variation. Especially vertical orbit
variation around 30 Hz and horizontal one from 50 to 100 Hz are drastically
reduced by suppressing vibration of the vacuum chamber. At present, the
horizontal and vertical fast orbit variations are respectively 4 and 1
micron levels at insertion devices. In my talk, I will show the brief summary
of SPring-8 orbit stabilization activities focusing on our original approach.
Advanced Photon Source Storage Ring Orbit Correction Overview (0.2Mbyte)
L. Emery /A.P.S.
At APS, the orbit correction system consists of a EPICS-based
fast orbit feedback operating with a DC block and a "slow" orbit feedback
operating from a workstation. We present one-day stability data and power
spectrum density data. The main features of each correction system is given.
Orbit noise from correctors is characterized. The beam stability is improved
by increasing in the rate of DC orbit feedback from presently 0.8 sec to
0.1 sec, and implementing a correction to the frequency band overlap between
the two systems.The efforts in doing feedforward compensation of pulsed
magnets are
mentioned.
Orbit Stability at the SLS (3.4MByte)
M. Boege /S.L.S.
Orbit Stability and Orbit Feedback Development at the ALS (1.3MByte)
C. Steier, G. Portmann, A. Biocca, E. Domning, T. Scarvie, E. Williams,
S. Jacobson /Lawrence Berkeley National Laboratory, Advanced
Light Source
Facility Report of the Pohang Light Source (3.3MByte)
S. H. Nam /Pohang Accelerator Laboratory
Design current and energy of the PLS are 300 mA at 2.0 GeV and 150 mA
at 2.5 GeV. The design values had been achieved. The PLS storage ring (SR)
now regularly ramps the electron beam energy to 2.5GeV from the 2.0GeV
injected beam. At 2.5GeV, the stored beam current is limited to about 180mA
by the SR RF power, but no serious instabilities are detected. There have
been many improvements in the PLS performance, such as beam availability,
beam position monitor resolution, SR cooling water and air temperature,
etc. There are numerous active upgrade plans to improve the PLS performance
further, including the RF power. To increase the RF power, we replaced
one out of present four 60kW klystrons with a 75kW klystron. Others will
be also replaced step by step. From the year 2001, the stability of the
closed orbit has been monitored carefully. Major orbit-drift is caused
by the temperature variation during the energy ramping in the storage ring
tunnel. The technical strategies to improve the orbit stability will be
introduced. The control and diagnostic system will be also upgraded with
the EPICS system and a temperature-stabilized diagnostic-station. Low-level
control system of the RF was upgraded in 2001 and it greatly improved the
PLS SR performance. Global orbit feedback system and beam based alignment
are under progress.
Optimizing Orbit Correction Configuration - Method and Applications (0.8MByte)
Yu-Chiu Chao /Thomas Jefferson National Accelerator Facility
This will be a report on a method developed recently that applies a
comprehensive set of
quantitative criteria on an orbit correction system to evaluate its
performance in almost all
aspects. Based entirely on analytical formulation, the method can answer
questions much more
efficiently and rigorously than simulation, as well as offer more insight.
Complementary
methods on optimization, failure mode and critical element studies
will also be discussed.
Application to the LHC transfer lines and the CNGS line, as well as
extension of this method
to more complicated systems such as the CERN PS Booster Extraction,
the CLIC Test Facility
EPA Ring, and possibly the LCLS and storage rings, will be discussed.
Reference: Y. Chao & V. Mertens, CERN-LHC-Project-Report-470,
http://documents.cern.ch/cgi-bin/setlink?base=preprint&categ=cern&id=lhc-project-report-470
"Activities on Beam Orbit Stabilization at BESSY II" (8.5MByte)
J. Feikes, K. Holldack, P. Kuske, R. Mueller /BESSY
Operational modes at BESSY require continuos orbit drift control with
a very high precision.
A general overview is given covering diagnostics (electron and photon
BPM systems),
corrector schemes, software components as well as general performance
characteristics.
Orbit Stabilization at SPEAR2 and Future Stabilization Plans for SPEAR3 (2.0MByte)
J. Safranek /SSRL
The SPEAR storage ring will be replaced with an entirely new accelerator
in a shutdown starting in April, 2003. I will discuss orbit stability
issues in SPEAR2, including BPM and orbit feedback performance, improvements
in LCW and air temperature, and rf chamber mode's effect on BPM performance.
Then I will discuss plans for SPEAR3, including stability specifications,
our program for mitigating sources of orbit motion, and plans for orbit
measurement and feedback.
Orbit Stabilization at ELETTRA (0.7MByte)
Emanuel Karantzoulis /Sincrotrone Trieste - ELETTRA
The orbit stability, its problematics and the ways to control it are
presented and discussed
STUDY OF ORBIT STABILITY IN THE SSRF STORAGE RING (2.0MByte)
Z.M. Dai, G.M. Liu and N. Huang /Shanghai Institute of Nuclear Research, Chinese Academy of Sciences
Analysis of the beam orbit stability and conceptual study of the dynamic
orbit feedback in the SSRF storage ring are presented. It is shown that
beam orbit motion at the photon source points is smaller than the orbit
stability requirements in horizontal plane, but exceeds the orbit stability
requirements in vertical plane. A dynamic global orbit feedback system,
which consists of 38 high-bandwidth air-coil correctors and 40 high-stable
BPMs, is proposed to reduce the vertical orbit motions. Numerical simulations
show that this dynamic orbit feedback system can stabilise the vertical
orbit motions in the frequency up to 100 Hz.
The Electron Equilibrium Orbit Adjustment and the Closed Orbit Correction in Hefei Electron Storage Ring (0.8MByte)
XU Hongliang, SUN Baogen, WAMG Yong, Liu Gongfa /National Synchrotron Radiation Laboratory, University of Science & Technology of China
Both the magnet field center of quadrupole magnet measurement results
and the closed orbit distortion correction measurement result of Hefei
electron storage ring are introduced in this paper. Especially, in the
process of closed orbit correction, the electron beam equilibrium orbit
is shifted to the center orbit of Hefei storage ring by monitoring the
closed orbit distortion due to momentum spread. And the electron injection,
accumulating and operation on the center equilibrium orbit are realized.
Digital BPMs - Experience and Vision from Our Perspective (0.1MByte)
R. Ursic /Instrumentation Technologies
Digital BPM became a common name for the beam position monitoring systems
that implement direct sampling of intermediate (IF) or radio frequency
(RF) signals with downstream processing in digital domain. This technology
holds great promise to be the foundation of the high performance and easy
to use (integrate) position monitoring systems of the future. In this presentation
we would like to share our experience and vision of digital BPM systems
with the emphasis on the following topics: accuracy, gain control scheme
and system architecture.
Experience with Damping Links at ESRF (0.6MByte)
L. Farvacque /ESRF
Orbit Fluctuation of Electron Beam due to Vibration of Vacuum Chamber in Quadrupole Magnets (Part 1 :9.6MByte , Part2: 2.9MByte)
Sakuo MATSUI, Masaya OISHI, Hitoshi TANAKA, Tetsuhiko YORITA, Koji TSUMAKI, Noritaka KUMAGAI,Toshiharu NAKAZATO /SPring-8
The fluctuation spectrum of electron beam orbit in the SPring-8 storage
ring had broad peaks around 40 Hz vertically and from 80 to 100Hz horizontally.
Fourier analysis identified these fluctuation source not as magnet vibration
but as chamber one due to the disturbance of cooling water. When the chamber
vibration was reduced by fixing the chamber rigidly, the orbit fluctuation
was also reduced in the same way. The magnetic field caused by induced
current loop in the thick chamber, where the impedance by inductance is
relatively larger than the real resistance, is equivalent to the field
when quadrupole magnet vibrates wit h the same amplitude in the region
above a few tens of Hz. The calculated fluctuation based on this model
agreed with the measured one.
Activities of Source Suppression for Improving Orbit Stability in PLS (2.9MByte)
S. J. Park and all PAL staffs /Pohang Accelerator Laboratory, POSTECH
In this presentation, we divide orbit drifts into two kinds - real and
apparent ones.
The real orbit drifts are caused by drifts and ripples of magnet power
supplies, variation of cooling-water and air temperatures, ground settlement,
and many other factors. Efforts devoted to suppress these sources of orbit
drfits are described. Apparent orbit drifts are largely due to instabilities
of BPM's. BPM instability is especially important when the BPM's are involved
in active orbit feedback systems. Details of efforts for overcoming BPM
instabilities in the PLS are reported.
Magnet Power Supply Stabilization and Checking system development (3.7MByte)
Hideki TAKEBE /SPring-8
A various monitoring system of high precision magnet current was developed.
High precision DCCT, scanner, differential recorder and FFT were installed.
Automatic measuring system and program using PC and the LabView were
developed.
QP current ripple and stability in 1 to a few Hz and long term drift
was improved.
Slow Orbit Feedback (SOFB) at the SLS (0.9MByte)
M. Boege /SLS
Slow Orbit Correction in the SPring-8 Storage Ring (1.1MByte)
K. Soutome /SPring-8
Since the beam commissioning started in March 1997, much efforts
have been done to reduce the S/N of BPMs and to suppress slow drifts of
the orbit. In the early stage of the commissioning the COD correction
was done by filtering measured COD data to get main harmonic components
of the distortion around the betatron tune. To reduce the S/N of
BPM data and go further in COD corrections we then calibrated the imbalance
of voltages from four button pickups of each BPM by using a stored beam.
We also estimated BPM offsets from high-harmonic components of measured
COD data. After these we could come close to the "golden" orbit without
using harmonic components in COD corrections. The S/N of BPMs was
further reduced by taking the average of repeatedly measured data on VME.
We determined the most suitable value for averaging by using a beam.
The estimated resolution now is better than 0.6um for horizontal and 0.5um
for vertical directions. For routine COD corrections in user operation
we first used steering magnets with iron yoke. However the jump of
orbit of the order of a few um was observed in each correction step.
This is due to the lack of setting accuracy of power supplies of steering
magnets. We then introduced new steering magnets with higher precision.
These magnets are of air-core type and hysteresis-free. The orbit
correction has now become smooth and RMS deviation from a reference orbit
is about 5um/day or better. The energy drift due to earth tide is
also corrected by adjusting RF frequencies. The amount of change
is calculated from a DC-component of measured COD data. The relative
energy deviation is now suppressed to the order of 0.001%.
Slow Orbit Feedbacks at the ALS: Recent Upgrades and Future Plans (0.8MByte)
C. Steier /ALS
Slow-Orbit FB and the performance of the new 7-bump algorithm at ELETTRA (0.6MByte)
Emanuel Karantzoulis /Sincrotrone Trieste - ELETTRA
The special operating conditions of ELETTRA have strongly influenced
the orbit correction philosophy. A hybrid orbit correction scheme is presented
whereby local orbit corrections at arbitrary positions and angles at three
different light source points of each of the eleven user dedicated sections
are performed that also maintain the global orbit stable. The method, the
stability and the implications are presented and discussed.
APS High Level Orbit Correction Software (0.1MByte)
L. Emery /APS
At APS we have long adopted the philosophy of using toolkit programs
and single-purpose applications that communicate through data and configuration
files. We have developped since 1995 an orbit correction "system" of applications
that manage data and communicate to the control system following the above
principles. The presentation will focus on the interrelated components
and ideas rather than the actual software implementation.
Specifics of the BESSY II 0.3Hz Orbit Correction System (4.9MByte)
J. Feikes, K. Holldack, P. Kuske, R. Mueller /BESSY II
In addition to a `good' minimization of orbit deviations the orbit control
procedures have to fulfill a number of boundary conditions: reproducibility,
minimal induced noise, constant beam energy, robustness against systematic
changes or spurious hardware failures etc. Implemented solutions as well
as available options are presented that improve the balance of the different
figures of merit.
Sources of Slow Orbit Movement and Orbit Feedback Systems in PLS Storage Ring (1.4MByte)
H. S. Kang /PLS
Slow orbit movement in the horizontal and vertical planes in the Pohang
Light Source (PLS) storage ring is analysed with the accumulated data of
BPMs, the tunnel floor elevation survey and the weather condition. The
slow change of the horizontal orbit is dominant during the change of season,
and the vertical orbit change is due to the differential ground settlement
and the rapid change of weather conditions like hard rainfall and temperature
change. Facts and causes of slow orbit movement are described, and the
requirements and scheme of the orbit feedback system are discussed.
APS Orbit Correction Hardware (3.8MByte)
Om Singh /APS
Orbit correction hardware at Advanced Photon Source Storage Ring consists
of three types of beam position monitors, two types of corrector systems
and two types of orbit feedback systems. Upgrades of the hardware, performances
of the orbit correction systems and future plans will be discussed.
Fast Orbit Feedback (FOFB) at the SLS (2.9MByte)
T. Schilcher /SLS
Operations with Fast Digital Orbit Feedback Systems at NSLS (1.1MByte)
Boris Podobedov /NSLS Brookhaven National Laboratory
Orbit feedbacks at the NSLS are very important to maintain user beam
stability in both the X-ray and the VUV storage rings. To improve this
stability even further we have replaced the analog orbit feedback systems
with new digital ones. Key advantages of digital systems include a) trivial
expansion to a larger number of beam position monitors and correctors b)
more sophisticated correction algorithms and c) effective use for machine
diagnostics. To build an economical and yet effective system we have implemented
an original architecture using commercially available VME boards. For every
feedback cycle, it digitizes analog orbit signals, calculates new corrector
strengths, converts them to analog form, and sends them to the correctors.
To perform a basic correction cycle this system doesn't need to communicate
with the rest of the NSLS control system and can therefore run at a very
high rate (presently 5 kHz). This high digitizing rate allowed us to achieve
a correction bandwidth in excess of 100 Hz limited only by the bandwidth
of the correctors. In this paper we review the system architecture and
algorithms, describe the performance achieved, and comment on operating
experience in both rings.
High Resolution and Stability Beam Position Measurements with Digital BPM Electronics (0.7MByte)
J. Denard /SOLEIL
Soleil is a third generation light source in construction near Paris,
in France. The Beam Position Monitoring (BPM) system is going to operate
in four main modes: orbit display and slow feedback, fast closed orbit
feedback, first turns, and turn-by-turn for machine studies. We intend
to use only one system that provides all four modes. The major difficulty
is to fulfil at the same time the sub micron requirements of the fast feedback
mode at less than 10 KHz with the more relaxed precision but higher speed
(1 MHz) of the turn-by-turn mode. The only system close to our requirements
is the SLS system commercialized by the I-tech company. A new calibration
scheme should allow to achieve all the SOLEIL requirements.
Exploiting
Digital BPMs at ELETTRA: a fast local orbit feedback and the feedforward
system
for the compensation of an Electromagnetic Elliptical Wiggler dynamic orbit
distortions
(0.6MByte)
D. Bulfone, R. De Monte, M. Ferianis, V. Forch, G. Gaio, M. Lonza /Sincrotrone Trieste
Two new-type electron beam position monitors (BPMs) located either side
of an Insertion Device (ID) have been recently installed in a long straight
section at ELETTRA. These BPMs are based on a new mechanical design of
the sensor, which takes full advantage of the 14 mm low gap ID chamber,
and on digital detector electronics. By combining high resolution and readout
rate, the new BPMs have been adopted in a fast local orbit feedback system
stabilizing the electron beam orbit and angle at the centre of the ID.
The two BPMs provide also the basic measurements that are used by the
feedforward correction system compensating for the orbit distortion produced
by an Electromagnetic Elliptical Wiggler (EEW) operated at high switching
frequencies (up to 100 Hz) of the horizontal field. The main results achieved
are presented.
Orbit Stability in PLS Storage Ring (10.0MByte)
E. S. Kim /PLS
We investigate the main sources of orbit drift in the PLS storage ring.
We investigate influence of machine turn on, energy ramping-deramping,
undulator gap height on the beam orbit drift. Global orbit feedback system
and the effects of full energy injection on the orbit stabilization will
be also presented.
X-ray Beam Stabilization by MOSTAB (0.8MByte)
Y. Nishino /SPring-8
Stability of optical elements as well as electron beam is essential
to obtain stable x-ray beam of synchrotron radiation. The MOSTAB (monochromator
stabilization) module is used to obtain stable x-ray beam in many synchrotron
radiation facilities. It is a feedback module to achieve stable x-ray intensity/position/energy.
A talk will be given on performance tests of MOSTAB at SPring-8.
Grobal Orbit Stabilization System for Photon Factory Electron Storage Ring (3.7MByte)
T. Obina /KEK
Strategies for Achieving Sub-micron Orbit Stability at SLS (4.5MByte)
T. Schilcher /SLS
Strategy for achieving sub-micron orbit stability at the APS (3.3MByte)
Om Singh /APS
The orbit stability at the Advanced Photon Source Storage Ring has been
achieved routinely to the level of 1 to 2 micron rms at the source points.
To achieve sub-micron level orbit stability, the performances of existing
BPMs and orbit correction systems need to be improved further. Recent upgrades
and future plans are discussed. The results, showing a reduction in orbit
distortion due to ID steering with a fast DC orbit feedback, are presented.
Strategy for Soleil Beam Position Stability at Submicron Level (1.3MByte)
M. Level /SOLEIL
In order to profit from the very high brilliance of SOLEIL, it is critical
to maintain a very high degree of orbit stability. Many precautions have
been taken in the early stage of the design and concern a large range of
time scales (from years to milliseconds). Several vibration measurement
campaigns on the site have been made and showed that the level of the natural
site noise is within the specifications. A new solution for the foundations
has been proposed and accepted. The magnetic elements of the storage ring
are grouped and rigidly mounted on girders which has been carefully designed
in order to push the eigenfrequencies at high values. In addition,
in order to reduce thermal variation effects, the temperature of
the ring tunnel and the cooling water will be stabilized within 0.1q-.
Finally, feed-forward local compensation of dipolar effects due to
variable field insertion devices and global real time feedback system are
also foreseen.
SPring-8 Closed Orbit Feedback System, a Challenge for Suppression of the Closed Orbit Vibration Down to Sub-micron Level (1.0MByte)
S. Sasaki /SPring-8
The feedback system for the closed orbit of the SPring-8 storage
ring will be presented. The discussion will be concentrated on the
feasibility of the BPM electronics to achieve the requirements of the feedback
system. The target of the feedback is to suppress the vibrations
of the closed orbit down to sub-micron order with the frequency range up
to 100 or 200 Hz. The requirements from the feedback target are signal
to noise ratio should be larger than 80dB, 100dB is desirable, with the
bandwidth of 10kHz or more. The wide bandwidth with large S/N ratio requires
large signal amplitudes, which bring some difficulty from the non linearity
of the electronics for the large amplitude signals. These requirements
will be compared with the data of the prototype electronics which is under
development.
H. Tanaka / SPring-8