Proceedings of IBIC2012, Tsukuba, Japan

MOPB52STATUS AND ACTIVITIES OF THE SPRING-8 DIAGNOSTICS
BEAMLINES
S. Takano*, M. Masaki, A. Mochihashi, H. Ohkuma, M. Shoji, and K. Tamura
JASRI/SPring-8, Hyogo 679-5198, Japan
H. Sumitomo, and M. Yoshioka, SPring-8 Service Co. Ltd. (SES), Hyogo 679-5165, JapanAt SPring-8 synchrotron radiation (SR) in both the Xray and the visible bands is exploited in the two
diagnostics beamlines. The diagnostics beamline I has adipole magnet source. Recently, the transfer line of thevisible light has been upgraded. A new in-vacuum mirror
was installed to increase the acceptance of the visible
photons. A new dark room was built and dedicated to thegated photon counting system for bunch purity
monitoring. To improve the performance, the input opticsof the visible streak camera was replaced by a reflective
optics. Study of the power fluctuation of visible SR pulse
is in progress to develop a diagnostic method of shortbunch length. At the diagnostics beamline I, the size ofthe electron beam is measured by imaging with the zone
plate X-ray optics. The diagnostics beamline II has an
insertion device (ID) light source. To monitor stabilitiesof the ID photon beam, a position monitor for the white
X-ray beam based on a CVD diamond screen was
installed. A turn-by-turn diagnostics system using themonochromatic X-ray beam of the ID was developed toobserve fast phenomena such as beam oscillation at
injection for top-up and beam blowups caused byinstabilities. Study of temporal resolution of the X-ray
streak camera is also in progress at the diagnostics
beamline II.

INTRODUCTION
Synchrotron radiation (SR) is a nondestructive probe todiagnose relativistic electron beams in high-energy
accelerators. At SPring-8 SR in both the X-ray and thevisible bands is exploited in the two diagnostics
beamlines [1]. The diagnostics beamline I has a dipole
magnet source, and the diagnostics beamline II has an
insertion device (ID) light source. In this paper we willreport present status and activities of the SPring-8
diagnostics beamlines.

DIAGNOSTICS BEAMLINE I (BL38B2)
The diagnostics beamline I (BL38B2) has a bending
magnet light source with critical photon energy of 28.9
keV. In 2011, the transfer line of the visible light was
upgraded. The schematic layout of the beamline after the
upgrade is shown in Fig. 1. The beamline has an optics
hutch and two dark rooms on the experimental hall. The
visible synchrotron light is separated from the X-ray
beam by two in-vacuum mirrors in the optics hutch. The
mirror below the photon beam axis is the original one andthe other one above the photon axis has been added in the
upgrade. The X-rays pass through the gap of the twomirrors. The separated visible light is transported in abent shielded pipe out of the optics hutch to thedarkrooms. The visible light separated by the lower

Figure 1: The schematic layout of the SPring-8 diagnostics beamline I (BL38B2).
____________________________________________*takano@spring8.or.jp

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Proceedings of IBIC2012, Tsukuba, Japan

original mirror is delivered to the second dark room,
which has been constructed in the upgrade and dedicatedto the bunch purity monitor. The light separated by theupper new mirror is delivered to the first dark room,
where the bunch length is measured by streak cameras
and studies of incoherent fluctuation of SR pulse areunder way. The X-ray line of the beamline is enclosed in
the optics hutch. It has a double crystal monochromatorthat covers the energy range of 4 to 14 keV by (111)reflection of silicon crystals. The X-ray transport line aswell as the front end has no windows, which obstructs
soft X-ray and visible/UV light and potentially could
distort wave front of X-ray SR. Therefore, all thecomponents of the X-ray transport line as well as the
monochromator are in bakeable ultra-high vacuum
chambers. The X-ray line includes the optical system of
the X-ray Beam Imager (XBI), implemented for beamemittance diagnostics.

focusing lens to the APD. The output signals of the APD
were analyzed by a fast digital oscilloscope. Fig. 2 showsc 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○Streak Cameras
For bunch length measurements, a dual-sweep streak
camera (C5680, Hamamatsu) has been operated in thefirst dark room. In the test studies of generation of shortpulsed SR by kicker magnet, we obtained images of thebunch from the side view with the streak camera andevaluated the tilt of the bunch to optimize the kicker
magnet [2]. Turn-by-turn behaviors of the bunch after
injection were observed by the streak camera to study
longitudinal dynamics of injected beam in the storage
ring [3]. In 2011, the input refractive optics of the streak
camera was replaced by reflective input optics. The
replacement has enabled us to eliminate the narrow
bandpass filter and to increase the input photons to thestreak camera. The performance of the streak camera forshorter bunch lengths and at lower currents is being
studied in low-alpha operation of the storage ring.
Recently, a high-resolution steak camera (FESCA-500,
Hamamatsu) has been introduced in the first dark room.

Incoherent Fluctuation Experiment
Feasibility study of the so-called fluctuation method forbunch length measuements is in progress in the first darkroom. When the radiation pulse with narrow spectral
bandwidth Δω has coherence length (τ c ~1/Δω)comparable to the source bunch length, its pulse-to-pulse
intensity fluctuations have a strong correlation with thebunch length [4]. The required spectral bandwidth toobtain short enough coherence length for sub-ps shortbunch is moderate compared to those for longer bunches,making the method advantageous for short bunch length
measurement. In the present study, an interferometricfilter with a center wavelength of 632.8 nm selected
photons within a bandwidth (FWHM) of 1 nm. A siliconavalanche photodiode (APD) module with an effective
diameter of 0.5 mm and an embedded amplifier (C5658,
Hamamatsu) was used to detect filtered radiation. To
reduce the number of transverse coherent modes
contributing to the signal fluctuations, the angular
acceptance was limited by a 4-jaw slit in front of the

Figure 2: An example of a set of histograms ofintensities in the signal region (red) and the baseline(blue) obtained by a oscilloscope (see text). The inset
shows a temporal bunch profile measured simultaneouslywith a visible light streak camera (circles) and a fitted
Gaussian curve (line).
an example of a set of intensity histograms for 5000
measurements of a single bunch beam. In the experimentto obtain shorter natural bunch length, the storage ring
was operated at a lowered energy of 7 GeV withincreased RF voltage of 18 MV. The bunch current was
0.2 mA. The intrinsic fluctuation of power of synchrotron
radiation pulse Δ I/I is calculated by subtracting thefluctuation of the baseline originating from electronicnoise. The bunch length deduced by further taking
account of contributions of photon shot noise andtransverse beam emittance was 11.3 ps (r.m.s.), consistent
with that of 10.8 ps measured simultaneously with avisible light streak camera. The observd fluctuation
showed a tendency to decrease for longer bunch length
obtained by increasing the bunch current. Further
experiment of single-shot bunch length measurements isplanned by using a single-shot visible lightmonochromator.

Bunch Purity Monitor
The bunch purity monitor in the second dark room isbased on the gated photon counting system of visible
synchrotron light [5]. It uses a microchannel plate typephoto-multiplier tube as a single photon detector. The
time spectrum of detected single photons representing thebunch fill pattern is accumulated by a multi channel
analyzer (MCA). In order to gate the photons emitted byISBN 978-3-95450-119-92

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Figure 3: The schematic layout of the bunch purity
monitor.
purity monitor can successfully detect parasitic satellite
bunches as low as 10-9 times the intensity of the mainbunches. It is continuously monitoring the purity of
isolated main bunches in several-bunch user operation
modes under topping-up injection. Upgrade of the bunch
purity monitor is in preparation in order to execute
immediate measurement of every replenished bunch intopping-up operation. A fast time measurement system
for the bunch purity monitor has been developed by
employing a time to digital conversion (TDC) VME
module (V1290N, CAEN) [6], which will be combinedwith a hybrid photo detector (HPD) capable of highphoton counting rate.

X-ray Beam Imager
For emittance diagnostics of the SPring-8 storage ring,
we have implemented the XBI in the optics hutch [7]. The
schematic layout of the optical system of the XBI isshown in Fig. 1. The XBI is based on a single Fresnel
zone plate (FZP) and an X-ray zooming tube (XZT)(V4410, Hamamatsu). An X-ray image of the electron

beam in the bending magnet source of the beamline is
obtained by the FZP. To eliminate the effect of thechromatic aberration of the FZP, monochromatic X-rays
are selected by the double crystal monochromator. The
magnification factor of the FZP is 0.274. To enlarge thereduced X-ray image of the electron beam the XZT is
employed as an X-ray camera. The combined
magnification of the XBI is 13.7 when the magnificationof the XZT is set at 50. The observing photon energy of
the XBI is 8.2 keV, which was determined by considering
the spatial resolution and the efficiencies of the FZP and
the XZT. The spatial and time resolution of the XBI are
4.1 µm (1σ), and 1 ms, respectively.
To further increase the brightness of SPring-8,
persistent efforts towards reduction of the beam emittancehave been made. Recently, extensive study of
optimization of storage ring optics is in progress to
reduce the natural emittance of nominal 3.4 nm.rad to 2.4
nm.rad [8]. We have measured the beam size with the
XBI in the study and have confirmed that the emittance issuccessfully controlled.

DIAGNOSTICS BEAMLINE II (BL05SS)
The diagnostics beamline II (BL05SS) has an ID as thelight source. The edge magnetic fields of the two bending
magnets at the both ends of the ID straight section are
also available as the light sources. The out-vacuum type
ID is mounted on a girder which can be slid on guiding
rails embedded in the floor. The sliding mechanism of the
ID enables us to remove it off the electron beam axis andto change its permanent magnets in the accelerator tunnel.
The magnet array of the ID is presently of Halbach typewith 51 periods of 76 mm long. The maximum value ofthe deflection parameter K is 5.8 [9]. The layout of thediagnostics beamline II is shown in Fig. 4. It has two

Figure 4: The SPring-8 diagnostics beamline II (BL05SS).
optics hutches and one experimental hutch. The X-slit andthe Y-slit in the front end are employed to shape the white
X-ray beam of the ID. The optics hutch I has theadjustable graphite and metal filters with moving
mechanisms, which are employed to fit the intensity andthe spectrum of white X-ray beam for beam diagnostics
purposes and SR irradiation experiments planned todevelop accelerator components such as photon absorbers[1]. The optics hutch II has a cryogenic double crystal

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monochromator that covers the energy range of 4 to 38
keV by (111) reflection of silicon crystals. The transportline of the monochromatic X-ray beam shielded by leadconnects the optics hutch II and the experimental hutch.
In 2011, we installed a position monitor for the white Xray beam in the optics hutch I to monitor stabilities of the
ID photon beam. A turn-by-turn diagnostics system basedon a fast fluorescence screen was developed in theexperimental hutch, to observe fast phenomena such asISBN 978-3-95450-119-9

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c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○the intense main bunches and to increase the detection
efficiency of photons emitted by parasitic satellite
bunches a fast light shutter system consisting of two
Pockels cells is employed (Fig. 3). The SPring-8 bunch

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Proceedings of IBIC2012, Tsukuba, Japan

beam oscillation at injection for top-up and beam
blowups caused by instabilities. The experimental hutch
has beryllium exit windows for monochromatic X-ray.
Precise measurement of the flux density of the ID X-ray
beam and study of temporal resolution of the X-ray streak
camera are also in progress in the experimental hutch.

c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○Photon Beam Position Monitor
In 2011 we installed in the optics hutch I a position
monitor for the white X-ray beam to watch the stability ofthe photon beam axis of the ID. Stability of the photon
beams of the IDs is one of the most important issues to beachieved at SPring-8. In 2006, the signal processing
electronics of the beam position monitors (BPMs)
included in the periodic orbit correction loop were
replaced by new one that have the resolution as small as
0.1 µm [10]. Recently, to further stabilize the photon
beams against perturbations to the electron beam orbit
caused by changes of magnet gaps of the IDs and by
operations of ID elements for switching of polarizationsof output photons, the cycle time of the orbit correction
loop has been reduced from the former seven seconds toone second.
The photon beam position monitor employs a thin
CVD diamond screen, which visualizes the X-ray beam.
Though the screen is destructive to the photon beam, it
enables us to observe directly the peak of the white ID
beam and to measure precisely the position of the beam,
rendering the monitor a promising tool to watch thestability of the ID photon beam axis. The setup of thephoton beam position monitor is shown in Fig.5. The(piA2400-17gm, Basler), which is connected to thecontrol network of SPring-8. The camera is controlled bya dedicated personal computer on the network. We
developed a control software of the camera, which
periodically captures the image of the photon beam,
analyzes the image of the beam spot on the screen, andstores the analyzed position of the beam to the databaseof the SPring-8 control system.
In 2012, we started continuous measurement of thephoton beam position except for the periods when otheractivities occupy the beamline II and are evaluating theperformance of the monitor.

X-ray Flux Measurement
Recently, at SPring-8 extensive study of optimizationof storage ring optics is in progress to reduce the naturalemittance of nominal 3.4 nm.rad to 2.4 nm.rad [8]. To
verify the benefit of emittance reduction to the photon

Figure 6: Flux density of 10 keV X-ray of the ID of thediagnostics beamline II for the present optics (blue) andthe new low-emittance optics (red). The measured results(circles) are in good agreement with theoretical
calculation by SPECTRA (lines).

Figure 5: Photon Beam Position Monitor.
screen is mounted on a copper holder, which is watercooled. The thickness of the CVD diamond screen is 50µm. The holder of the screen is actuated by an air
cylinder, which has two operating positions for 1) beamobservation and 2) retraction for other activities of thebeamline. The screen is set at an angle of 45° with respect
to beam direction and the beam profile on the screen isobserved by a precision CCD camera. The camera is ahigh resolution (2448 x 2050) gigabit ethernet camera

flux of IDs as theoretically predicted, we measured theflux density of 10 keV photons from the ID of thediagnostics beamline II. We put an ion chamber near the
beryllium exit window in the experimental hutch. We set
an angular aperture at 4 µrad x 4 µrad by putting a 4-jaw
slit in front of the ion chamber. We measured the spectral
flux density by changing the output energy of themonochromator in the optics hutch II. The magnet gap of
the ID was fixed so that the energy of the third harmonic
radiation is 10 keV. The measured flux density of the new
2.4 nm.rad optics was 1.3 times higher than that of thepresent (Fig. 6), and it is consistent with theoretical
calculation by SPECTRA [11].

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Turn-by-turn Beam Diagnostic System
In the experimental hutch, we have developed a turnby-turn beam diagnostic system by observing spatial
profile of the monochromatic X-ray radiation of the ID. It
has a fast fluorescence screen (YAG:Ce) with decay timeof several tens of nanoseconds in a vacuum chamber ofthe beamline, which converts the X-ray beam profile into
a visible light image. The two-dimensional visible image
on the screen is further transformed into two line images
corresponding to the horizontal and the vertical profile,
respectively, by an optical system implemented on a
optical table in the atmosphere. A fast-gated CCD camera
with an image intensifier simultaneously captures the twoline images. With this system studies of the stability ofthe storage ring beam are in progress, such as oscillationsof the stored beam excited by injection bumps for
topping-up, and variations of beam size and energy
spread in instabilities of a high current single bunch beam.
The details of the experimental setup of the system aswell as its working principles, and results of beamobservations will be presented in a separate paper [12].

X-ray Streak Camera
We installed an X-ray streak camera (C5680-06,
Hamamatsu) in the experimental hutch. In the test studies
of generating short X-ray pulse with a vertical kicker at
SPring-8, we measured with the X-ray streak camera thelength of X-ray pulse sliced by a narrow horizontal slit
and successfully demonstrated the reduction of the pulse
length [2]. One of the key technical issues of theexperiment is the temporal resolution of the X-ray streak
camera, which is dominated by effects of velocity spreadof the secondary electrons from the photocathode thatconverts the X-ray photons into the electrons. To evaluate
the effects on the temporal resolution quantitatively, we
have studied temporal spread of single X-ray photons asmeasured by the X-ray streak camera. Detailed results ofthe single photon experiment will be given in a separate
paper [13].
We installed an FZP in the experimental hutch to focus
the photon beam on the input photocathode of the X-ray
streak camera for single-shot measurements of faintbunches such as injected beams. Tuning of the FZP and
the X-ray streak camera for single-shot measurements isunder way.

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IPAC2011, San Sebastián, September 2011,
THPC031, p. 2978 (2011); http://www.JACoW.org[4] M. S. Zolotorev and G. V. Stupakov, SLAC-PUB7132, March 1996.
[5] K. Tamura and T. Aoki, “Single Bunch Purity during
SPring-8 Storage Ring Top-Up Operation,“ Proc. 1st
Annual Meeting of Particle Accelerator Society ofJapan 2004 (2004) p.581;http://www.pasj.jp/web_
publish/pasj1_lam29/WebPublish/5P50.pdf[6] A. Kiyomichi et al., “Upgrade of Time Measurement
System for Bunch Purity Monitor at SPring-8,”
WEPS106, to appear in Proc. 9th Annual Meeting ofParticle Accelerator Society of Japan, Toyonaka,
August 2012 (in Japanese).
[7] S. Takano, et al., Nucl. Instr. and Meth. A556 (2006)
p.357.
[8] Y. Shimosaki et al., “Optimization of Lower
Emittance Optics for the SPring-8 Storage Ring,”
TUPPC013 , to appear in the proceedings of
IPAC2012, New Orleans, May 2012.
[9] M. Masaki et al., “Characterizations and Applicationsof the Insertion Device of the SPring-8 Diagnostics
Beamline II,” SRI2009, Melbourne, September –October 2009, AIP Conf. Proc. 1234 (2010) p.560.
[10] T. Fujita et al., “Commissioning and Status of New
BPM Electronics for COD Measurement at theSPring-8 Storage Ring,” PAC2007, New Mexico,
June
2007,
FRPMN031,
p.3997(2007);
http://www.JACoW.org[11] T. Tanaka and H. Kitamura, SPECRA code ver. 9.02
(2012);
http://radiant.harima.riken.go.jp/spectra/index.html[12] M. Masaki et al., “Development of Turn-by-turn
Beam Diagnostic System using Undulator
Radiation,” TUPB63 , these proceedings.
[13] A. Mochihashi et al., “Measurement of Temporal
Resolution and Detection Efficiency of X-ray Streak
Camera by Single Photon Images” MOPA48 , theseproceedings.

REFERENCES[1] S. Takano et al., “Overview of the SPring-8
Diagnostics Beamlines,” SRI2009, Melbourne,
September – October 2009, AIP Conf. Proc. 1234
(2010) p.399.
[2] C. Mitsuda et al., “Current Status of Short X-ray
Pulse Generation with a Vertical Kicker in the
SPring-8 Storage Ring,” WE-D-P-28 , to appear in
the proceedings of SRI2012, Lyon, July 2012.
[3] T. Watanabe et al., “Measurement of Longitudinal
Dynamics of Injected Beam in a Storage Ring,”

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