Proceedings of IBIC2012, Tsukuba, Japan

TUPA02

MODERNIZED OF THE BOOSTER SYNCHROTRON DIAGNOSTICS IN
THE TAIWAN LIGHT SOURCE
C. H. Kuo, K. H. Hu, P. C. Chiu, C. Y. Liao, C. Y. Wu, Y. S. Cheng, S.Y. Hsu, Jenny Chen,
K. T. Hsu, NSRRC, Hsinchu 30076, Taiwan
Abstract
Taiwan Light Source (TLS) is a 1.5 GeV synchrotron
based light source which was dedicated 20 years ago.
After several major and minor upgrades, the TLS now
operated in top-up mode since late 2004. A new 3 GeV
Taiwan Photon Source (TPS) is in construction to provide
more x-ray users. To provide a test bed for the diagnostic
devices in booster synchrotron for the TPS project, thediagnostics of the TLS booster synchrotron is revised
recently. It can also provide up-to-date diagnostics for the
TLS booster to help to achieve a better operation of theinjector for the TLS storage ring. Efforts of these
upgrades and modifications are summary in this report.

one location is used as a photon port. The BPM locationon the booster is shown in Fig. 1. Past efforts to measureclosed orbit and turn-by-turn position of in the TLS
booster synchrotron during ramping from 50 MeV to 1.3
GeV are summarized in references [2, 3, 4]. Energy
ramping of the TLS storage ring from 1.3 GeV to 1.5
GeV was done in 1995 to enhance x-ray emission. The
booster synchrotron was raised from 1.3 GeV to 1.5 GeV
in 1999 to provide full energy injection for the storagering.

The TLS booster synchrotron was delivered in 1992 [1].
Some diagnostics of the TLS booster revised in recently
by borrow components for the TPS project before its
commissioning in 2014. Two goals of these revised
efforts, the first goal is as test bed for the TPS project to
do hardware, software, and application development. The
second goal is to provide better understanding its
characteristics of the TLS booster synchrotron. The major
parameters of the TLS booster synchrotron aresummarized in Table 1. This study focus on BPM
electronics, tune monitor, synchrotron radiation monitor,and perform some preliminary test to check functionality
and performance.
Table 1: Major design parameters of the TLS booster
synchrotron relate to diagnostics.
Parameters
EnergyCircumference
Periodicity
Energy spread
Momentum compaction factor
RF frequency
Harmonic number
Tune
Chromaticity
Betatron function (max)Repetition rate

Value
1.5 GeV(operated at 1.3 GeV
before 1999)
72 m
12
5 x 10-4
0.058
499.654 MHz
120
Qx ~ 4.4, Qy ~ 2.43
[x ~ -6.5, [y ~ -2.8
Ex ~ 11.9 m, Ey ~ 11 m
10 Hz

BPM ELECTRONICS
Beam position monitor (BPM) in the TLS booster
synchrotron was mounted 45 degrees on the chamber at
between the dipole and the quadrupoles. The lattice of thebooster synchrotron is FODO type with periods of 12.
There are 23 BPMs used around the synchrotron, because

Figure 1: BPM layout of the TLS booster synchrotron.
The BPM cabling and electronics were completely
modified during shutdown in August, 2012. BPM
electronics borrow from the TPS project. These BPM
electronics will available before TPS commissioning in
2014. The four buttons of each BPM were connected to a
Libera Brilliance+ [5] BPM module directly. The BPM
electronics provide turn-by-turn data for x, y, and sum
signals. Further processing include spectral analysis,
decimated raw data to reduce amount of data, data
averaging, etc. are easy to do by various software
applications after data readout from BPM electronic.
Validation checking and preliminary measurement are
in proceeding since the accelerator startup from shutdown
in the early September. The preliminary measured orbit isshown in Fig. 2. The extraction is disabled, so, the beam
can survive almost full booster cycle (100 msec).

ISBN 978-3-95450-119-9
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1c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○INTRODUCTIONTUPA02

Proceedings of IBIC2012, Tsukuba, Japan500Hor. Position (mm)-5Hor. Position (mm)

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Figure 3: Horizontal beam position variation during beam
extraction bumper magnets triggered. Each curve
represents one BPM readings; vertical data of consecutive
BPM is offset -1 mm for visualization purpose.

TUNE MONITOR

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Copyright ○

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(b) Vertical beam position
Figure 2: Beam position variation during the booster
energy ramping. Extraction is disabled. Each curve
represents one BPM reading, consecutive BPM data
vertical offset is -2 mm for clear visualization. The first
BPM trace is in the injection straight, the last tracecorresponding on the last BPM just at upstream of
injection straight.
The extraction of the TLS booster done by threebumpers excited by 2 msec half-sine current, a septum
excited by 500 Psec half-sine and a extraction kicker by
an PFN type pulser. Bumpers were excited for 1 msec
before extraction. The septum is triggered 250 Psec
before extraction. The orbit excursion during theextraction process proceed is started about 44.5 msec andend at 45.5 msec is clear visible in Fig. 3. The maximum
beam excursion should appear at BPM within the threebumper magnet bump. However, the measurement showsthat the extractions bump is not a closure bump. The BPM
reading will help to adjust extraction condition setting of
the booster synchrotron.

Efforts to measure working tune for the TLS booster
synchrotron were described in reference [1, 6, 7]. Early
efforts adopt extraction kicker as beam excitation withshift timing and strength adjustment setting at different
energy and use digital oscillator to capture demodulated
signal and perform FFT analysis to extract tune. The
method can only capture single tune value at specificenergy during the ramping; it needs many booster cycles
to construct the tune variation along ramping. Excitationof booster magnets system should stable enough toachieve useful measurement. This pulsed kicker is awindow framed, two-turn, ferrite magnet capable ofproviding 1.4 mrad horizontal kick to the extractionenergy. Since the accelerating electron beam covers awide range of energy change, the kicker strength has to befinely tuned so as not to over-kick and loss the electron
beam. Since the excitation kicker produces only
horizontal deflection to the electron beam, it is difficult to
identify the vertical component. However, there is a small
coupling between horizontal and vertical tune signals canbe identified successfully.
In the latest effort [7], a dedicated diagnostic kicker was
installed over a ceramic chamber. This kicker can provide
horizontal and vertical kick simultaneously and adopt logratio BPM electronics to extract beam oscillation
information. The stored electron beam in the booster was
excited with a magnetic pulse from the kicker. While theelectron beam executed betatron oscillation along thebooster ring, the transverse motion of the beam signal was
picked up by the stripline through a log ratio amplifier.
The associated turn-by-turn information was recordedwith a transient digitizer where the length of the recording
data was defined. The raw data was then saved to thecontrol console where the FFT analysis and peakidentification were performed. It still need many booster
cycles for measurement to construct full cycle tune
variation.
There are two stripline electrodes on the TLS booster,
however, small shut impedance due to large aperture
prevent its in-effective as beam excitation in higher
energy portion. It was decided to modify the diagnostic

ISBN 978-3-95450-119-92

Accelerator Technology

Proceedings of IBIC2012, Tsukuba, JapanX-Y kicker as magnetic shaker [8, 9]. Single turn coil of
X-Y kicker was removed. Multi-turn coils are mound on
the existed ceramic chamber of the diagnostic kicker.
There are two coils in each plane enclosed surrounding
ferrite box with ceramic chamber surrounding them. The
kickers with 50Ω terminated load have calibration factorof 3 mG/A. The kickers are driven by a 50W amplifier ineach plane. The input signal is a band-limited white noise
in a bandwidth from 1 MHz to 2 MHz. The turn-by-turnbeam oscillation data is observed by the Libera
Brilliance+ [5] BPM electronics. The functional block
diagram of this new tune monitor system is shown in Fig.
4. A digital step attenuator is used to control the
excitation level [10].

TUPA02(a) Horizontal tune variation during ramping cycle.

Horizontal
coil pairs
Verticalcoil pairs

Digital Step
Attenuator
1 ~ 2 MHz
Narrow
Band
White Noise
Generator

f rev= 4.167 MHz
50 W Power Amplifiers
Attenuation
Control
Circuitry

10 Hz
Trigger

BPM
orStriplines
Libera Brilliance+

Figure 4: Functional block diagram of the new tune
monitor for TLS booster.
Vertical coils(b) Vertical tune variation during ramping cycle
Figure 6: Spectrogram of the turn-by-turn beam position
data. Tune shift in the booster ramping can be observed
clearly.
Tune information was obtained by spectra analysis of
the FFT of turn-by-turn beam position data. Tune
variation during ramping was observed in current routine
operation setting. The fractional tune drift can be as large
as 0.2. It is related to the tracking errors among
focusing/defocusing quadrupoles and dipole. In
cooperating with the monitoring system of FQ and DQ todipole magnet strength, optimization of the booster
working point can be efficiently achievable in tuning thebooster synchrotron.

SYNCHROTRON RADIATION MONITOR
Horizontal coils

Figure 5: Magnetic shaker.
Preliminary test show that the beam can be excitedeffectively during the whole ramping cycle. A digital
stepping attenuator is added to adjust the attenuation
excitation level to prevent too large excitation at low
energy which will cause beam loss. The BPM canobserved betatron sideband with acceptable signal tonoise ration. Figure 6 shows the spectrogram of thehorizontal and vertical of BPM turn-by-turn data. The
spectra line is clean visible. We excite the beam
oscillation using magnetic shaker. Owing to the fast dataacquisition and calculation capability, the tune drift
during ramping can be observed in cycle to cycle basis.

The synchrotron radiation monitor of the booster
synchrotron has been replaced the original Firewire
camera [11] by GigE Vision camera. Data acquisition andanalysis is done by an EPICS IOC which embedded
Matlab [12]. The layout of the synchrotron radiation
monitor is same as reference [4]. The two axes translation
stage is added to easy align the light to enter the CCD
camera as shown in Fig. 7 (b). The monitor contains acomputer, GigE Vision CCD camera, lens, molybdenum
mirror, band-pass filter (centre wavelength at 550 nmwith 10 nm spectral width) and motion stage. In this new
design, a CCD camera comply with GigE Vision standard
allows maximum data bandwidth 125 Mbytes/s over Cat
5e/6 cables up to 100 m, and a motorized translation stage
moves the camera in XZ directions to adjust the CCD
position. The photons of synchrotron radiation emitted by
the electron bunches passing through a bending magnet in
the booster ring are reflected by a molybdenum mirror
and passed through a convex lens (f = 500 mm) to form
image at CCD image sensor. The magnification factor is
2:1 to save for current setup.

ISBN 978-3-95450-119-9
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Copyright ○Magnetic Shaker

TUPA02

Proceedings of IBIC2012, Tsukuba, Japan40

Molybdenum Mirror

Hx
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BPF

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Bending Magnet

X axis

U = 4.584 m

Z axisLens
f = 500 mm

Orbit Height : 1250 mm

Camera Server

Gigabit Ethernet (GigE)

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Figure 7: Layout of the synchrotron radiation monitor andphoto of the CCD camera mounted on two axes
translation stage.
The display GUI for the booster synchrotron radiation
monitor is shown in Fig. 8, which has been developed andhas the same features as previously. The CCD exposure
time and trigger delay are set to 1 ms and 30 ms(corresponding to energy about 0.8 GeV); as a result, thebeam size is 0.74 mm (Vx), 0.34 mm (Vy). Raw data andfitted parameters are published as EPICS PV such that
EPICS clients can readily access for further usage.

Figure 10: Deduced beam emittance from measured beam
size variation during energy ramping.

PRELIMINARY EXPERIMENTS
When good diagnostics are available, parameters of thebooster can be check routinely. We performed several
simple experiments in a limited available time of thebooster synchrotron in machine start up and summarized
in this paragraph.

Tune Stability
It can monitor the tracking stability of dipole andquadrupole power supplies, when tune variation data ofeach booster cycle available. Figure 11 shows the 5continuous tunes measured in an interval of 100 booster
cycles (10 seconds). There is no sensible tune variation.
The difference of these measured tunes is shown that therepeatability of tune is good for 5 times measurement.
The fractional tune difference is less than 0.005. The
difference looks like form the data fluctuation rather thanform the contribution of power supplies. Long-term
stability for hours will be further studies.
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Figure 8: User interface for the booster synchrotron
radiation monitor.

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A beam profiles during energy ramping is shown in
Fig. 9; Extracted variation of the beam emittance isshown in Fig. 10. The emittance decreases when theenergy increases due to radiation damping. A significant
shift of position occurs near 45 msec in ramping cycle inhorizontal is due to the extraction bumpers are excited.

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Ver. tune differencec 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○100Polarizer
BPF, 550 nm, 10nm FWHM
Control Network

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0
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Figure 11: Reproducibility of tune is good for 5 times
measurement. The fractional tune difference is less than
0.005.

Chromaticity Measurement
Figure 9: synchrotron radiation profiles at several
different energy during energy ramping, the CCD
exposure is 1 ms (energy scan mode).

The chromaticity of booster has been calculated as RF
frequency and measured tune change during the ramping.
For a small variations, the chromaticity should be a linear
function of the tune shift, [x,y = -Dx fRF 'Qx,y/'fRF. The
momentum compaction factor ac is normally a constantdepending on the lattice. The measurement result isISBN 978-3-95450-119-9
4

Accelerator Technology

Proceedings of IBIC2012, Tsukuba, Japanthe TPS booster synchrotron and software development.
The schedule of TPS is still for one year, a plan to test
hardware and software supporting are in proceeding. Plan
to study the TLS booster synchrotron is also launched.

shown in Fig. 12.
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ACKNOWLEDGEMENT

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The authors thank injection group for their supports ofthis study. Help from the staffs of the operation group to
operate the booster synchrotron for experiments arehighly appreciated.

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REFERENCES

Figure 12: Measured uncompensated chromaticity.

Turn-by-turn Data Analysis
Independent component analysis (ICA) [13] method isused to analyze turn-by-turn data to calculate horizontal
beta function as Fig. 13. The spatial and temporalfunction of ICA shows the integer part and the fractionalpart of horizontal tune are 4 and 0.31 respectively. The
lattice is symmetric where odd BPMs location have low
beta value and even’s BPMs are located at high beta
section. The ICA analysis result shows that they are
consistence from model. There is a little bit nonlinearityand distortion effect that are contributed in the high beta
BPM location. Systematic study to improve reliability of
BPM data by the usage of ICA that is a short-term effort.
0.03

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Mode 1 Spatial Function

4

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model Ex

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E function (m)

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s position (m)[1] K. K. Lin et al., “Performance of SRRC 1.3 GeVelectron booster synchrotron”, Nuclear Instruments
and Methods in Physics Research, Section A 361(1995).
[2] T. S. Ueng et. al., “The closed orbit measurement of
SRRC booster during ramping”, Proceedings of 1995
Particle Accelerator Conference (1995).
[3] T. S. Ueng et. al., “Turn-by-turn beam position
measurement for 1.3 GeV booster synchrotron”,
Proceedings of 1995 Particle Accelerator Conference(1995).
[4] K. H. Hu, et al., “Closed Orbit Measurement System
for the Booster Synchrotron in SRRC”, Proceedingsof the 1999 Particle Accelerator Conference, New
York, 1999.
[5] Instrumentation Technologies: http://www.i-tech.si.
[6] K. T. Hsu, et. al., “Tune Measurement of SRRC
Booster During Ramping”, Proceedings of EPAC
2000, Vienna, Austria.
[7] C.S. Fann, et al., “Electron Beam Excitation at SRRC
Booster During Ramping by Using a X-Y Kicker”,
Proceedings of EPAC 2002, Paris, France.
[8] J. M. Koch, “New Tune Measurement System for the
ESRF Booster”, Proceedings of the DIPAC 2005,
Lyon, France.
[9] E. Plouviez and J. M. Koch, private communication.
[10] U. Iriso, et al, “Tune Measurement System at the
ALBA Booster”, Proceedings of the BIW10,
TUPSM01, Santa Fe, 2010.
[11] C. H. Kuo, et al., “Status of the Synchrotron
Radiation Monitor at TLS”, Proceedings of EPAC
2006, Edinburgh, Scotland, UK.
[12] C. Y. Liao, et al, “Image Profile Diagnostics Solution
for the Taiwan Photon Source”, these proceeding.
[13] Xiaobiao Huang, et al., “Application of independent
component analysis to Fermilab Booster”, Phys. Rev.
ST Accel. Beams 8, 064001 (2005).

Figure 13: Preliminary results to apply ICA to calculate
horizontal beta function using BPM turn-by-turn data.

SUMMARY
In this report, we are performed some minor
modification of the TLS booster synchrotron tomodernize orbit, tune, synchrotron radiation monitor. The
system can be used as test bed for the similar system forISBN 978-3-95450-119-9
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