Proceedings of IBIC2012, Tsukuba, Japan

TUPA01DIAGNOSTICS UPDATE OF THE TAIWAN PHOTON 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
Taiwan Photon Source (TPS) is a 3 GeV synchrotron
light source which is being construction at campus of
NSRRC. Various diagnostics are in implementation andwill deploy to satisfy stringent requirements of TPS for
commissioning, top-up injection, and operation. These
diagnostics include destructive monitors, beam intensity
observation, trajectory and beam positions measurement,
synchrotron radiation monitors, beam loss monitors, orbit
and bunch-by-bunch feedbacks, filling pattern andmiscellaneous devices. Current status will summarize inthis report.

INTRODUCTION
The TPS is a latest generation of synchrotron lightsource featuring high brightness with extremely low
emittance [1]. Civil construction and installation will befinished in 2013. Machine commissioning is scheduled in
2014. The accelerator system consists of a 150 MeV Sband linac, linac to booster transfer line (LTB), 0.15–3
GeV booster synchrotron, booster to storage ring transfer
line (BTS), and 3 GeV storage ring. The diagnostics will
help TPS to achieve its design goals. Major diagnostics
related parameters for the booster synchrotron and thestorage ring are summarized in Table 1. Beam size anddivergence angle is summary in Table 2.
Diagnostics for the TPS accelerator system weresummary in reference [2]. Diagnostics of linear
accelerator and transfer lines will help to generate anddelivery high quality electron beam to booster and storage
ring. Booster diagnostics will provide beam parameters
include orbit, working tunes, circulating current, filling
pattern, beam size, bunch length, emittance, and derived
parameters. The diagnostics are designed to provide acomplete characterization stored beam in the storage ring,
including averaged beam current, fill pattern, beam
lifetime, closed orbit, working tunes, chromaticity, beamsize, beam loss pattern, beam density distribution,
emittance, bunch length, and etc. To utilize the benefits of
the high brightness and small beam sizes of TPS sources,
photon beams must be extreme stable both in position andangle to the level of better than 10% of beam sizes anddivergence. Table 2 provides the electron beam sizes andangular divergences for the selected TPS sources. The
most stringent beam measurement and stability
requirement will be for the vertical position at the 7 m
straight for ID source (y = 5.11 m); this will require
special consideration for measuring both electron andphoton beams.

Table 1: Major Parameters of the Booster Synchrotron
and the Storage Ring
Booster Synchrotron

Storage Ring

Circumference (m)

496.8

518.4

Energy (GeV)

150 MeV – 3 GeV

3.0

Natural emittance (nm-rad)10.32 @ 3 GeV

1.6

1656

1729.2

Revolution period (ns)
Revolution frequency (kHz)603.865578.30Radiofrequency (MHz)499.654499.654

Harmonic number

828

864

SR loss/turn, dipole (MeV)

0.586 @ 3 GeV

0.85269

Betatron tune

14.369/9.405

26.18 /13.28

ν /ν
x

y

Synchrotron tune s

-

α,α)

Momentum compaction (1

Damping partition Jx/Jy/Js

τ /τ /τ (ms)Natural chromaticity ξ /ξDipole bending radius ρ(m)
x

y

s

x

0.00611

×

2.4 10-4, 2.1 10-3

9.553 10-4

8.86 10-4

×Natural energy spread

Damping time

×

-

2

×

1.82/1.00/1.18

0.9977/1.0/ 2.0023

9.34/ 16.96 / 14.32

12.20/ 12.17 / 6.08

-16.86/-13.29-75 / -26

17.1887

8.403383-yRepetition rate (Hz)

Table 2: The Electron Beam Sizes and Divergence
Source point
12 m straight center7 m straight center
Dipole (1o source point)

σ

x

μm)

σ

μ

x’

σ

y

μm)

σ

μ

y’

(

( rad)(( rad)

165.10120.81
39.73

12.49
17.26
76.11

9.85
5.11
15.81

1.63
3.14
1.11

BEAM INTENSITY MONITORINGThe TPS 150 MeV linac system was contracted to the
RI Research Instruments GmbH [3]. The schedule fordelivery and commissioning is in early of 2011 at test site.
The linac will move to the TPS building in late 2012 after
TPS building available. Beam instrumentation comprises
five YAG:Ce screen monitors for beam position andprofile observation, two fast current transformers (FCT)
to monitor the distribution of charge and one integrating
current transformer (ICT) for monitoring total bunch train
charge. Wall current monitors (WCM), which is formedby equally spaced broadband ceramic resistors, mounted
on a flexible circuit board and wrapped around a shortceramic break, will give information on beam charge aswell as longitudinal profiles of electron bunches. All of
mentioned diagnostics were provided by the vendor
except the profile measurement data acquisition andanalysis [4].

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Integrating current transformer will provide
information of beam charge pass LTB and BTS and henceon the beam losses during the injection cycle.
At booster synchrotron, circulating current will bemeasured with Bergoz’s NPCT, while bunch pattern will
be monitored with a fast current transformer.
A high precision averaged current measurement at thestorage ring will be performed by Bergoz’s NPCT. The
NPCT device provides a resolution of better than 1
A/Hz1/2 and has large dynamic range and bandwidth to
make itself a versatile device for measuring lifetime andinjection efficiency.
All sensors were acquired form Bergoz [5]. Finaldesign and implementation for all vacuum chambers tohost various current transformers are in proceeding.
Two approaches will be used to measure individual
bunch current or filling pattern. Fill pattern of the storage
ring observed from the sum signal of BPM buttons by
wide bandwidth oscilloscope or fast digitizer sampling at
RF or a multiple of RF frequency will enablemeasurement of the bunch current to better than 0.5%
accuracy. This information is sufficient for filling patterncontrol or feedback applications for top-up operation andvarious studies. The other method is used time correlated
single photon counting (TCSPC) for high dynamic
population measurement. Avalanche photodiode detector(APD) is used to detect scattered X-ray photon or visible
light and count by the HydraHarp 400 TCSPC system [6].
More than six order of dynamic range (106) can beachieved easily.

DESTRUCTIVE PROFILEMEASUREMENTThe YAG:Ce fluorescence screens will provide
information on beam position and profile for the LTB
amd BTS. The OTR screens are also considered to be
used for high precision of beam emittance and energy
spread measurement at the diagnostic branch of the LTB
and at the selected position of the BTS to avoid saturation
of YAG:Ce screens. There are six cells of booster
synchrotron. Each cell will install a YAG:Ce screens.
Fluorescent screens will be installed at injection andextraction section and at the other lattice cells to facilitate
booster commissioning, troubleshooting and psychology
needing – to see is to believe. The screen material will be
YAG:Ce, which has good resolution of the beam image
and exhibits high sensitivity and high radiation hardness.
There are screen monitor at just after the injection septumof the storage ring for injection condition adjustment.
Design and implementation of the screen monitor
assembly is in proceeding. Data acquisition and analysis
solution is developing [7].

BEAM POSITION MONITORING
The beam trajectory for the LTB/BTS will bemonitored with button type beam position monitors

equipped with Libera Brilliance Single-Pass [8], its
functionality is similar with the BPM electronics for thebooster and the storage ring but equipped with high gain
analogue board to improve its performance for single passmeasurement. Preliminary beam measurement was doneat TPS linac test transport line. Better than 50 m
resolution can be achieved for a bunch train with total
charge of 0.5 nC [4].
Booster orbit will be monitored with 60 BPMs with
turn-by-turn capability. The BPM electronics will be thesame as those in the storage ring. The sum signal from thereceivers can be used to monitor fast history of the beam
current. Booster BPM block is shown in the upper left
corner of Fig. 1. All BPM blocks were received.
Integrated with vacuum chamber is in proceeding.
The storage ring has 24 DBA lattices cells with 6-foldsymmetry configuration [1]. Each cell will have fivestandard RF BPMs mounted on elliptical chambers, two
primary RF BPMs located in the ID straight section
mounted on racetrack chambers. To achieve the highest
level of orbit measurement resolution, the optimization of
the button geometry to obtain a high resolution for bothstandard and primary BPMs is in progress. Prototype
BPM equipped with 7.4 mm button diameter and 17.7mm separations on the 60x30 mm elliptical chamber has
been implemented. The BPM constant is around 13 mmin both planes were achieved with adequate linearity. The
primary BPM will install in 20 mm height racetrackchamber with monitor constants around 9 mm, both side
have bellows to ensure stability of the BPM. BPM blockfor the storage ring arc is shown in upper right corner in
Fig. 1, while the BPM block of straight is shown in thelower left corner. Photo of the arc BPM flange is shownin the lower right corner.
Booster and BTS BPM clock

Cross section of the arc BPM

Button diameter10.7 mm

Button diameter

Gap

0.3 mmGap

0.4 mm

Button separation

17.5 mm

Chamber dimension

30 x 68 mm

Button separation-

Chamber dimension

20 x 35 mm

Cross section of the straight BPM

Button diameter

7.4 mmPhoto of the arc BPM button flange

7.4 mmGap

0.4 mm

Button separation

13.5 mm

Chamber dimension

16 x 64 mm

Figure 1: BPM block for the TPS project.
BPM electronics was award to Instrumentation
Technologies in 2011 to delivery Libera Brilliance+ [8]for TPS project. The BPM electronics platform is in
microTCA form factor. The crate can host up to four
BPM modules in AMC form factor. The new BPM

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platform enhanced functionality and performance. All
BPM platforms are received in 2012. Acceptance test offunctionalities and performance are summary in thereference [9]. Installation for acceptance is shown in Fig.
2.
Up to two X-ray photon BPMs (XBPM) will be
installed at each beamline. The electronics consists
functionalities such as current to voltage conversion,
range selection, bias, ADC, local signal processing,embedded EPICS IOC, delivery slow data (~ 10 Hz rate)
for control system access and fast data (~ 10 kHz rate) for
feedback purpose. The fast data is compatible with orbit
feedback infrastructure. It can seamlessly be integrated
with the orbit acquisition system and feedbacks. The
BPM electronics will be embedded with EPICS IOC forslow access form the machine control system side andbeamline control system side. Commercial products like
Libera Photon [8] or its successor will be used.

diodes beam loss monitor (BLM) for loss patternmeasurement. Revised version of Bergoz’s PIN BLM [5]will be adopted to improve its connectivity. Cat 5/5e
twisted cable will be used to connect of BLM to dataacquisition electronics and EPICS IOC. The twisted paircables provide power to the BLM module and send backsignal from the BLM. It plans to install 6 PIN BLM percell and total number is 144 on the TPS storage ring. New
design simply the cabling and installation. At the control
rack side, an in-house made adapter will equip withpower supplies and receiver to convert the count signal
into TTL pulse. Several scintillator and photomultiplier
combine detectors will also be used for high counting rateapplications, such as loss mechanism selective
experiments. Both the PIN type and scintillation type
BLM will be working in counting mode. A scaler inindustry pack (IP) form factor [11] with history buffer andshadow register will installed in cPCI IP carrier module
which will install on the EPICS IOC. The data acquisition
will be performed by the nearby EPICS IOC and can be
performed in synchronous way by the help of timing
system.
Some novel BLM are possible to adopt for some
applications. Scintillation fiber based BLM with Silicon
Photomultiplier (SiPM) might also adopt for beam loss
detection [12]. Glass rod based Cerenkov radiator with
SiPM is also in evaluation for beam loss detection.
Distributed dosage is measured on-line by using
RADFET [13] is also in study.

Figure 2: Acceptance test for the BPM electronics.

ORBIT FEEDBACKSTUNE MEASUREMENT
Tune measurement at the booster synchrotron, theelectron beam will be excited with narrow bandwidth
white noise using striplines. The beam response will beobserved with a to the dedicated BPM buttons with thefront-end amplifier. Turn-by-turn data acquired by BPM
electrons can also use as input for Fourier analysis. Realtime spectrum analyzer is an alternative solution. There
will be an extra set of striplines for a bunch cleaningsystem and for users who need a specific filling pattern inthe storage ring. Prototype test at the TLS booster
synchrotron is described in reference [10].
There are several methods available for tune
measurement at the storage ring. In the instance ofinjection kicker(s) fire, turn-by-turn data from BPM
electronics can be further processing to get tune easily. In
the stored beam case, if the beam is unstable, tune by-turndata from the BPM can be used to extract tune. If thebeam is stable, shaker by transverse kicker by white noise
is needed. Another using the notch in the averaged
spectrum of selected bunch or all bunch bunch-by-bunchdata can also be used as tune monitor.

BEAM LOSS MONITORING

Slow orbit acquisition will perform by channel accessto the BPM platform embedded EPICS IOC up to 10 Hz
rate. Fast orbit beam position will circulate around all
BPM platforms at 10 kHz rate by using BPM grouping
scheme. Orbit of the whole ring can be accessed from any
BPM platform. Fast data of XBPM is also possible to be
integrated with BPM system for feedback purpose later..
The TPS will adopt modularized high performancecorrector power supply which was developed in-house[14]. The power supply will use analog regulator, adopt
biased analogue PWM scheme to improve zero current
crossover problem. The current sensing element is theLEM Danfysik Ultrastab 868-20I DCCT for slow
corrector and shunt for fast corrector. Combining all ofthese schemes improves integrated noise level from DC to
1 kHz down to a few parts per million of the output fullscale corresponding to nano-radian level kick for slow
corrector with maximum ±600 rad kick. Control of eachcell’s corrector will be through a custom designed 20 bits
DAC in corrector power supply controller (CPSC) [15].
This module will provide EPICS CA interface via
embedded EPICS IOC for configuration, setting andstatus monitoring. Two fast setting ports support 10 KHz
sustain setting stream. Two fast setting ports might
configure as AURORA and Gigabit Ethernet for different

TPS storage ring plans to adopt coincidence type PIN

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Proceedings of IBIC2012, Tsukuba, Japanapplications. The AURORA is suitable for fast orbit
feedback application with less overhead. The gigabit
Ethernet interface is supported to receive unidirectional
UDP packet via private network. The CPSC embedded an
waveform generator, it can serve various beam excitation
scheme for beam response observation, fast transfer
matrix measurement, …etc.
The DAC modules design will be also supported feedforward applications as well, such as, global feed-forward
orbit control and global skew quadrupoles feed-forward
coupling control for elliptical polarized insertion devices
operation. These feed-forward setting can be issued fromEPICS IOCs or dedicated computers more than 200 Hz
rate are feasible.
The feedback calculation [16] will be performed by the
FPGA module installed in the BPM platform. Twofunctionalities of this FPGA module will perform: one isgrouping the whole ring BPM data by using two counterrotating redundant links around the ring, the other is usedas feedback engine. BPM data grouping provides a way to
distributed all BPM around the TPS storage ring at all
BPM platforms in 10 kHz rate. Orbit feedback
computation will distribute to the all 48 FPGA modules
and install at the BPM platform. Half will serve. HalfFPGA module will serve for horizontal plane and theother half serve vertical plane. One or two sniffer nodes(eavesdropping) will be setup to capture orbit information
with 10 kHz rate for more than 10 sec record time anddecimated data at lower rate with much longer record
time will be supported for various applications andanalysis. The functional block diagram of the orbit
feedback infrastructure is shown in Fig. 3.
toCell N-1 BPM
platforms

Cell NBPM platforms

6.5 Gbps BPM
Grouping Link

Corrector Power Supply Rack
(up to 8 power supply module/rack)
2.5 Gbps Corrector
Setting Link
(AURORA)
Horizontal Fast
Correction

Vertical Fast
Correction
toCell N+1 BPM
platforms

Grouping and fast orbit feedback FPGA module

Horizontal
Fast Corrector

VerticalFast
Corrector

20 bits
DACs

FPGA

24 bits
ADCs

EPICS IOCplatform will serve for the horizontal plane fast orbit
feedback, the other will serve for vertical plane. The
control rule will apply on the eigenmode space rather thanon real space directly This will delivery robust andinsensitive to single or a few BPMs reading error andpossible to apply different control parameters fordifference eigenmodes.
There are two difference schemes for the slow orbit
control. The first option is to implement an independentslow orbit feedback loop and communication with the fast
orbit feedback loop – move DC component of fast
corrector to slow corrector regularly in the second order.
The second option is move the DC component of fast
corrector to nearby slow corrector. Both scheme were
simulated can achieve desired performance.

BUNCH-BY-BUNCH FEEDBACKS AND
DIAGNOSTICS
Transverse coupled-bunch instability mainly caused by
the resistive wall impedance and other sources will
deteriorate beam quality. Bunch-by-bunch feedback
system is planned to suppressed instabilities to ensure
TPS to achieve its design goals. The system will be
implemented in vertical plane and horizontal plane.
Transverse feedback kickers are planned to adopt the
SLS/ELETRA design and compatible with TPS vacuum
vessel. Transverse signals pick-up will be used as an extra
BPM and installed at location of high beta function.
Beside feedback functionality, the feedback electronics
and software also support bunch oscillation data capture
for analysis to deduce rich beam information, tune
measurement, bunch clearing, and beam excitation andetc. Features of the planned system include the latest highdynamic range ADC/DAC (12/16 bits), high performance
FPGA, flexible signal processing chains, flexible filter
design, bunch feedback, tune measurement, bunchcleaning, various beam excitation scheme, flexible
connectivity, and seamless integrated with the control
system. On-line control interface to operate feedback
system and off-line analysis tools should be included.
Functional block diagram of the planned bunch-by-bunch
feedback system is shown as Fig. 4. Commercial
feedback processor iGp12 from Dimtel [17] will serve for
the TPS. Prototype test is ongoing.

Corrector Power Supply Controller, CPSC

Figure 3: Functional block diagram of the fast orbit
feedback infrastructure on each cell.
There are 4 fast correctors per cell and total 96 fast
correctors in each plane. All fast correctors are mounted
at bellow site with maximum 30 rad kick angle. The
FPGA responsible to fast orbit feedback using fast
correctors as actuator. Seven BPM electronics are hosted
in two BPM platforms, so 48 BPM platform in total. To
simply the system configuration, the FPGA of one BPM

Figure 4: Prototype electronics for bunch-by-bunch
feedbacks.

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Proceedings of IBIC2012, Tsukuba, Japan

Synchrotron radiation from a dipole will be used toobserve the beam profile during energy ramping andemittance measurements. Beam size of the booster
synchrotron during the ramping will shrink from (x= 0.7mm, y= 1.5 mm) at 150 MeV to (x= 0.15 mm, y= 0.1mm) at 3 GeV due to radiation damping. It will measureby two synchrotron radiation monitors working in center
wavelength of 400 nm or less. Short wavelength can
reduce diffraction contribution slightly. The capability tomonitor bunch length with a streak-camera will be also
provided.
Beam size of the storage ring bending magnet 1o source
point (x = 39.73 m, y = 15.81 m) is small. It prevents
conventional imaging method at visible light wavelengthfor precision beam size measurement is possible due to~50 m diffraction contribution which is about threetimes of the vertical beam size. So, X-ray imaging system
is needed for precision beam size measurement. The
visible light is still need for temporal, longitudinal andtransverse dynamic observation. Since the beam size is in
the small prevent imaging method in visible light region
useless. However, interferometer and p-polarization beam
size measurement will implement as complementally tool
for the x-ray pin-hole camera.
Two X-ray pinhole cameras imaging of the electron
beam from bending magnets is the baseline design for the
TPS emittance measurement. As they offer the required
resolution and the dynamic range to measure the electron
beam size accurately at all currents from below 1 mA to
500 mA stored beam current range. Optimization of the
X-ray pinhole system will give possibility to measurevery small beam sizes in a few microns typically. Its mainfunction will include measurement of the electron beamenergy spread and vertical beam size.
The filling pattern measured by TCSPC will usedavalanche photodiode detector (APD) to detect scattered
X-ray photon or visible light. The APD will mound on thesynchrotron radiation monitor station also.
Visible light beamline will be built to measure various
beam parameters include longitudinal and transverse
parameters. Streak camera operates at 250 MHz
synchroscan mode is preferred to observe beam behaviorof the consecutive bunches. Integrating the streak camera
system with EPICS is planned. The contract was award to
the Hamamatsu newly delivery C10910 universal streak
camera [18] system and accompany with necessary
sweep units and accessories with 1 psec temporal
resolution. It will available in 2013. Beam size
measurement by visible light interferometer and polarization method is also considered.

include scraper, stripline kicker, synchrotron diagnostics,
data acquisition for specific diagnostic application which
are not includes in this report are still on the way. Control
system supports and applications are in development
phase. Refining of interfaces among different systems andgroups is underway. Efforts to dig out insufficient parts
and avoid last minute wonder are continue watch. Prepare
for installation is the current focus. Installation andintegration of accelerator system are scheduled in 2013.

ACKNOWLEDGEMENT
Authors thank helps from Vacuum Group and Precision
Mechanical Group for their efforts on design andimplement of various diagnostics devices.

REFERENCES[1] TPS Design Handbook, version 16, June 2009.
[2] K. T. Hsu, “Design Status of the diagnostic system
for the Taiwan Photon Source project”, Proceedingsof BIW2010, TUPSM101.
[3] K. L. Tsai, et al., “Beamline design and beammeasurement for TPS linac”, Proceedings of
IPAC2011, WEPC038, San Sebastián, Spain.
[4] C. Y. Liao, et al., “Diagnostics for the 150 MEV
linac and test transport line of Taiwan Photon
Source”, Proceedings of DIPAC 2011.
[5] Bergoz Instrumentation: http://www.bergoz.com.
[6] PicoQuant: www.picoquant.com.
[7] C.Y. Liao, et al., “Image profile diagnostics solution
for the Taiwan Photon Source”, these proceedings.
[8] Instrumentation Technologies: http://www.i-tech.si.
[9] P. C. Chiu, et al., “TPS BPM electronics
performance measurement and statistics”, theseproceeding.
[10] C. H. Kuo, “Modernized of the booster synchrotron
diagnostics in the Taiwan Light Source”, theseproceedings.
[11] MCS8522 Multi-channel Scaler – Industry Pack
User’s Manual, Hytec Eelectronics Ltd., 2012.
[12] uBLM: http://www.microsensor.it.
[13] RADFET: http://www.radfet.com/id4.html.
[14] Y. D. Li, K, B, Liu, “TPS Fast Corrector Magnet
Power Converter”, Proceedings of IPAC2011, San
Sebastián, Spain.
[15] D-TACQ: http://www.d-tacq.com.
[16] P. Leban, at al., “Fast orbit feedback calculation
implementation for TPS”, these proceedings.
[17] Dimtel, Inc.: http://dimtel.com.
[18] http://sales.hamamatsu.com/en/products/systemdivision/ultra-fast/streak-systems/part-c10910.php.

SUMMARY
Update of diagnostics system for TPS are summarisedin this report. Detailed engineering design of various
diagnostics devices and electronics are in proceedingISBN 978-3-95450-119-9
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