12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3

BEAM INSTRUMENTATION CHALLENGES FOR HIGH-ENERGY AND
LOW-EMITTANCE BEAM AT SuperKEKB
G. Mitsuka∗ , KEK, 1-1 Oho, Tsukuba, Ibaraki, Japan
Abstract
The SuperKEKB electron–positron collider, which started
the commissioning in February 2016, is a luminosity frontiermachine for the search for new physics. In this presentation,
we review the main challenges we face for the high-energy
and low-emittance beam at SuperKEKB, fast and low-noise
beam-orbit feedback system, X-ray beam-profile monitors
for measurements for the beam size of 10 µm, novel diamondmirrors with extremely high thermalconductivity for extracting synchrotron radiation, and various type’s beam loss diagnostics for the identification orpossibly early detection of
sudden beam losses. This presentation includes future directions of the R&D—X-rayinterferometry for micron-level
beam size measurements and fast optics measurements withthe gated turn-by-turn BPMs—towards next-generation lightsource facilities and high-energy colliders.

OVERVIEW OF SuperKEKB
SuperKEKB is a positron–electron collider with ananobeam scheme [1], which currently achieves the world’s
highest luminosity for producing B meson pairs. SuperKEKB consists of a 4 GeV positron ring (LER) and a 7 GeVelectron ring (HER) [2]. The nanobeam scheme allows thevertical beta function at the interaction point to be muchsmaller than the bunch length. The vertical beta function
and the beam size at the interaction point are the smallest in the world among colliders. The machine operation
started in March 2018 with a test run to verify a nano-beamscheme, and then the physics run began in March 2019. The
vertical beta function at the interaction point, 𝛽∗𝑦 , has beensqueezed down to 1.0 mm during 2019. We tested for further squeezing in 𝛽∗𝑦 down to 0.8 mm for approximately one
week in 2020 and 2022. Adopting a crab-waist scheme forboth rings since the 2020 spring run has increased the luminosity. The crab-waist ratio is 80 % and 40 % in LER
and HER, respectively. The crab-waist scheme at SuperKEKB is combined with the local chromaticity correctionin the interaction region. We achieved a peak luminosity of
4.65 × 1034 cm−2 s−1 with 𝛽∗𝑦 = 1.0 mm in the physics run
and the highest luminosity of 4.71 × 1034 cm−2 s−1 without
data acquisition by the Belle-II detector. The machine parameters that accomplished the peak luminosity and thosefor the target luminosity in 2028 are presented in Table 1.
As of September 2023, we are in a long shutdown to
upgrade the Belle-II detector and SuperKEKB. SuperKEKB
is scheduled to resume operations in December 2023.
∗ gaku.mitsuka@kek.jp

Table 1: SuperKEKB Machine Parameters Achieved on
8 June 2022 and Expected in 2028
Parameters

8 June 2022
LER HER

2028
LER HER𝐼[A] 1.321 1.099 2.75
2.20
𝑛𝑏
2249
2345
𝐼𝑏
[mA] 0.587 0.489 1.17 0.938
𝛽∗𝑥[mm] 80.0
60.0
𝛽∗𝑦[mm] 1.0
1.0
0.6
0.6
𝜉𝑦
0.0407 0.0279 0.0604 0.0431
𝜀𝑦
[pm]
31.7
21
Σ∗𝑦
[µm]
0.252
0.160
𝜎𝑧
[mm] 5.69
6.02
7.23
7.05
Crab-waist ratio [%] 80
40
𝐿[cm−2 s−1 ] 4.65 × 1034
2.4 × 1035

BEAM PROFILE MONITORSThe realization of a low-emittance beam is essential forhigh luminosity in SuperKEKB. Accordingly, accurately
measuring small beam sizes and short bunch lengths is entrusted to beam diagnostic systems.
SuperKEKB operates synchrotron radiation monitors in
the X-ray and visible light regions to measure the beamprofile, say, beam size and bunch length. Here, we report the
recent updates of the X-ray beam size monitors and visiblelight beam profile monitors.

X-ray Beam Size Monitors
The X-ray beam size monitor (XRM) is dedicated to measuring the electron and positron vertical beam size using
X-ray synchrotron radiation and will be capable of singleshot (single bunch, single turn) measurements [3]. The
XRMs are installed one to each main ring. Since the fastsilicon-strip detectors and the fast readout systems developed under the US-Japan collaboration were not in time,
we have measured the vertical beam sizes by analyzing the
X-ray-induced images projected on the scintillator screens.
X-rays produced by the bending magnet pass through thecoded aperture optical mask about 10 m downstream andenter a detector box 30 m further downstream, where thescintillator screen and CMOS camera are housed.
The beam study results, which commenced in May–July
2018, suggest the point spread function 𝜎𝑠 = 6.6 µm, consistent with the simulation-estimated spatial resolution of theimaging system and scattering in the beamline. The overall performances of XRMs in LER and HER are accurate
and satisfy the measurement accuracy presently required bySuperKEKB.

TU1I0101 Overview and Commissioning

131

Content from this work may be used under the terms of the CC-BY-4.0 licence (© 2023). Any distribution of this work must maintain attribution to the author(s), title of the work, publisher, and DOI

IBIC2023, Saskatoon, Canada
JACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0
d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - T U 1 I 0 1

Content from this work may be used under the terms of the CC-BY-4.0 licence (© 2023). Any distribution of this work must maintain attribution to the author(s), title of the work, publisher, and DOI

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3

IBIC2023, Saskatoon, Canada
JACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0
d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - T U 1 I 0 1

As shown in Table 1, we will further squeeze the vertical
𝛽 function to 0.6 mm, and the design beam size at the zerocurrent is 7 µm. Since the current XRM would be insufficient to meet this more demanding requirement, we started
upgrading the XRM to a spatial coherence-based interferometer. Figure 1 shows an overview of the X-ray interferometer.
The interferometer uses the double slit with a spacing of
30 µm instead of a coded aperture optical mask. Accordingly, the measurement method changes from geometricalto wave optics. The width of both slits is 15 µm. The synchrotron radiation generated at the emission point (bending
magnet) passes through the double slit located about 10 m
downstream from the emission point. Then, it enters thedetector box 30 m further downstream.

Figure 1: Schematic view of the X-ray interferometer at
SuperKEKB.
Figure 2 (a) shows the simulated interference fringes witha beam size of 10 µm and X-ray energies of 9 keV and 15 keV.
Figure 2 (b) shows the interference fringes first measured in
March 2022, but nothing is actually visible. When we performed the beam test, the beam size was 25 µm, which was
too large to measure interference fringes (prior to changing
to the double slit, we performed measurements using thenormal XRM with coded aperture). After the SuperKEKB
electron ring resumes operation in January 2024, we will
temporarily switch to the test beam optics to achieve a beam
size of 10 µm and try the beam test again. The following
two points are future challenges for the X-ray interferometer:
1) Limit the X-ray wavelength. As shown in Fig. 2 (a), a
broad X-ray wavelength range causes interference fringes
to overlap, leading to a loss of measurement accuracy. The
most affordable Cu foil filter or a noble gas filter, such as Kr
gas, can pass the X-ray around 10 keV. 2) Introduction of an
X-ray reflection mirror. In order to completely superimpose
the X-rays passing through the double slits each other, a totalreflection mirror, not yet installed, is necessary.

Beam Halo Monitors
The most significant background events to the Belle-IIdetector consist of 1) scattering of the beam by residual gas
in the beam pipe and 2) Touschek scattering, which is thescattering of electrons or positrons within the bunch. Bothof these scattering events create a cloud-like halo around thecentral core of the beam, which comes to a background eventfor the Belle II detector. The beam halo also induces radioactivation of other accelerator components. Since the beam
halo will be a significant problem, especially in high-current
operation toward increasing luminosity, direct measurement
and understanding of the beam halo is necessary.
We developed the coronagraph for measurements of beam
halo in 2020-2021 [4]. The coronagraph consists of threestages of optical systems: objective, re-diffraction, and relay systems. An objective system with a long focal length
was required as we would use the coronagraph 60 m downstream of the synchrotron radiation emission point. Because of the dimension of the diamond extraction mirror(20 mm (W) × 23 mm (H)) installed at 23.6 m downstreamof the emission point, the entrance pupil of the objective
system was accordingly limited. Aiming to achieve enoughresolution in these constraints, we designed a reflective telephoto system based on the Gregorian telescope for the objective system. The focal length was 7028 mm, and the front
principal plane was at the diamond extraction mirror. The
re-diffraction and relay systems were designed based on a
Kepler-type telescope. As a result of initial testing in 2022
using the SuperKEKB electron and positron beams, the performance of the objective system had a diffraction-limited
quality, and we achieved a contrast of six orders of magnitude.
Shown in the left panel of Fig. 3 is a result taken in LER
on 2022 March at the average bunch current 0.61 mA. Although patterns of the beam halos in LER irregularly change
in each shot, the beam halo in LER is radially available
away from the beam core and seems more substantial thanthat in HER. The result in HER in the right panel of Fig. 3
was taken at a comparable bunch current 0.55 mA as in
LER. This tendency may originate in a difference in the
beam collision scheme; we made the LER measurements inbeam-beam collisions, but no beam-beam collision occurred
during the HER measurements. Note that the beam-induced
background to the Belle-II detector is known to be moreabundant in LER than in HER.

Synchrotron Radiation Extraction Mirror Renovation

Figure 2: (a) Simulated interference fringes with a beam
size of 10 µm and X-ray energies of 9 keV and 15 keV. (b)Measured interference fringes with a beam size of 25 µm.

The polycrystalline diamond-based synchrotron radiation
extraction mirror enables precise measurement of beam profiles using visible light, including beam halo measurements.
For correctly measuring the beam profiles, thermal deformation of extraction mirrors must be minimized as low as
possible and thus has been one of the significant issues insynchrotron radiation monitors.

TU1I01132

01 Overview and Commissioning

IBIC2023, Saskatoon, Canada
JACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0
d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - T U 1 I 0 1
Min = -1.316e+02 nm, Max = -1.833e+01 nm at 1049 mA

Min = -1.241e+02 nm, Max = -2.183e+01 nm at 45 mA

200

200

150

5

150

5

50
0

0

−50

100
Horizontal (mm)Horizontal (mm)

100

50
0

0

−50

−100
−5

−10

−150
−5

0

5

10

−200

−100
−5

−10

Vertical (mm)

−150
−5

0

5

10

−200

Vertical (mm)Figure 3: Measurements for beam halos in LER (left) andHER (right).

Figure 5: The surface flatness measured by a Hartmann test
using a square array screen at 45 mA (left) and 1049 mA(right).

We developed platinum-coated diamond mirrors in 2019to obtain better initial flatness and suppress thermal deformation [5]. The diamond mirrors were made with
an optical-quality polycrystalline-diamond substrate withthermal conductivity 1800 W/(mK) and had a size of
20 mm (W) × 31 mm (H) × 1.2 mm (D). In optical testingwith a laser interferometer performed before installation
into the SuperKEKB ring, we confirmed the surface flatness
better than 𝜆/5 (𝜆 is a reference wavelength 632.8 nm, seeFig. 4.) The diamond mirrors were installed in electron andpositron rings in the 2020 summer and 2021 summer, respectively. Though irradiation for a year at the beam current
greater than 1 A, we observed surface flatness better than𝜆/4 at the beam current ranging from 50 mA to 1 A. Figure 5
indicates the surface flatness at 45 mA (left) and 1049 mA(right), measured by a Hartmann test using a square array
screen. We conclude that the extraction mirror has no beam
current-dependent deformation below 1 A.

At SuperKEKB, we usually measure X-Y coupling andvertical dispersion by closed orbit analysis for a beam artificially excited by steering magnets. The two types ofnarrowband detectors are utilized for closed orbit analysis,
508 MHz and 1 GHz, depending on the cutoff frequency ofthe chamber. The 1 GHz narrowband detectors have beenused since the KEKB accelerator, the predecessor of SuperKEKB. The 508 MHz narrowband detectors are newly
installed in LER to deal with lower cutoff frequency. The
beam optics measurements and their correction using thenarrowband detectors need a few tens of minutes.

Figure 4: Measurement for the surface flatness of the extraction mirror with a laser interferometer.

BEAM POSITION MONITORS
SuperKEKB needs to squeeze vertical beam sizes at theinteraction point down to 50 nm and minimize betatron coupling (X-Y coupling) and dispersion function, causing an
increase in beam size. Additionally, betatron function measurements and their corrections are essential since a disturbance of the betatron function leads to a dynamic aperture
reduction and vertical emittance growth.

Gated Turn-by-Turn Monitors
For fast measurements for beam optics, including X-Y
coupling during beam-beam collisions, we utilize the injection kickers or the transverse feedback kickers to excite a
specific non-colliding bunch while leaving colliding bunches
unaffected. Electrode signals from beam position monitors(BPMs) for only a non-colliding bunch are specially processed by the gated turn-by-turn beam position monitors(GTBTs) [6]. The narrowband detector, taking 4 s per measurement, has a positioning resolution of 2 µm, considerably
better than the GTBTs, having several tens of µm resolution.
A GTBT detector has four-channel BPM inputs. Incoming
BPM electrode signals first go to a fast RF gating switch [7]that accepts signals from only a non-colliding bunch (pilot
bunch) and rejects signals from others. Insertion loss owing
to the RF gating is 4 dB and the isolation is 80 dB, bothof which fully meet our requests. Rejected BPM signals
return to four-channel BPM outputs connecting to an external
508 MHz narrow-band detector circuit in charge of a closed
orbit analysis. Accepted pilot bunch signals are processedin a GTBT through 508 MHz bandpass filters, low-noise
amplifiers (total gain 40 dB), log-ratio amplifier (ADL5513),
peak hold circuit, and are finally analog-digital converted by
a 14-bit ADC (ADS850). The Xilinx/AMD FPGA controls atiming signal to synchronize these processes. Table 2 shows
the GTBT specifications.
In Gen1, analog components from the RF switch to the
log-ratio amplifier were mounted on a digital circuit board
with an FPGA, causing digital noise to the analog circuit.
On the contrary, in Gen2, the above analog components are
modularized and housed in an aluminum box to separate

TU1I0101 Overview and Commissioning

133

Content from this work may be used under the terms of the CC-BY-4.0 licence (© 2023). Any distribution of this work must maintain attribution to the author(s), title of the work, publisher, and DOI

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3

Content from this work may be used under the terms of the CC-BY-4.0 licence (© 2023). Any distribution of this work must maintain attribution to the author(s), title of the work, publisher, and DOI

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3

IBIC2023, Saskatoon, Canada
JACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0
d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - T U 1 I 0 1

them from the digital board. The update in the analog circuitin Gen 2 significantly reduced the noise floor and increased
the dynamic range by 5 dB.
Table 2: Gated Turn-by-Turn Monitor Specifications
Parameters
FPGA
Low-noise amp.
Log amp.
ADC
Linearlity
Number of monitors

Gen1

Gen2

Spartan-6
HMC616ADL5513
ADS850> −75 dBm
140

Zynq
PGA-103+
ADL5513
ADS850> −80 dBm2

power controller; one is the kick angle for fast feedback sentfrom the feedback controller at a rate of 32 kHz via opticalfiber. The other is a kick angle with an update rate of about
1 Hz sent via EPICS channel access, which is used to set theslow vertical feedback, horizontal dithering feedback, andhorizontal and vertical DC bump orbits [8].

BEAM-ORBIT FEEDBACK SYSTEM
Beam-orbit Feedback at the Interaction Point
In collider accelerators, beam orbit variation causes alateral distance between the two beam axes at the interaction
point, reducing luminosity. When the quadrupole magnet
near the interaction point vibrates, the beam undergoes adipole kick, and the closed orbit changes, resulting in a shiftof the closed orbit equivalent to the magnitude of the magnet
variation.
The displacement of the quadrupole magnet has been
simulated and measured, resulting in the primary oscillationof several 10 Hz, and the distance between the beams at
the interaction point is about 20 nm. We have developed a
feedback system to compensate for the orbit variation at theinteraction point of several 10 Hz.
Figure 6 shows a schematic diagram of the beam-orbit
feedback system. There are four BPMs, two on the left sideand two on the right side of each ring, across the interaction
point at a distance of about 0.5 m from the interaction point.
A total of eight steering magnets placed at HER control thevertical orbit at the interaction point. The button electrodeis made with a rod with a diameter of 1.8 mm to reduce thebeam power received by the electrodes. We use Alumina forthe vacuum seal and rod support. The body and rod are madeof titanium and brazed to a Cu-Ni flange. The power at thedetection frequency of 509 MHz is −4.3 dBm. The signal
level at the entrance of the signal processing circuit, including cable loss, is −17.5 dBm and −13.3 dBm on the left andright sides, respectively. In the signal processing circuit,the 509 MHz component of the beam signal is analog downconverted to the intermediate frequency of 16.9 MHz. The
analog to digital converted signal is further down-converted
to the baseband frequency by a digital down converter, anda digital filter finally limits bandwidth. The feedback controller receives four BPMs’ position information from thefilter board via the high-speed serial data transfer. The Xilinx/AMD Vertex-5 FPGA calculates the kick angle of thesteering magnets required for beam orbit feedback.
The steering power controller inputs the steering magnet’s
kick angle from the upstream feedback controller, converts
it to an analog signal by a 16-bit DAC, and outputs it to themagnet power supply. There are two inputs to the steering

Figure 6: Schematic diagram of the beam-orbit feedback
system.

Bunch-by-bunch Feedback System
Many bunches must be stored in the SuperKEKB ringwith a 4 ns separation toward a target luminosity. In sucha condition in the storage ring, the beams’ electromagnetic
fields interact with the vacuum components and the ions andelectron clouds in the vacuum chamber, resulting in beam
instability. A bunch-by-bunch feedback system was developed to observe and suppress unwanted beam instability.
See Ref. [9] for details of the system.

CHALLENGES TO
SUDDEN BEAM LOSS EVENTSCurrently, the biggest obstacle to increasing the beam
current in SuperKEKB is the sudden beam loss, which is asudden beam abort that results in the loss of about half ofthe beam charge within 2–3 turns. For more details on thesudden beam loss, refer to Ref. [10].
Although we have not clarified the mechanism of sudden
beam loss, the discharge phenomenon is one of the most
likely scenarios. According to this scenario, metallic dustin the beam pipe or vacuum chamber is plasmaized by theelectromagnetic field caused by the beam. An intensely
grown plasma generates an electric field like an arc discharge
at a certain moment, and the discharge suddenly kicks a partof the bunch train. The kicked bunch loses most of the bunchcharge at the collimator, which has the narrowest aperturein the ring.

Bunch Oscillation Recorder
The bunch oscillation recorder measures the variation in
the position of the kicked bunch. See Ref. [11] for a detailed
description of the bunch oscillation recorder. Figure 7 shows
an example of a bunch oscillation recorder measurement,

TU1I01134

01 Overview and Commissioning

IBIC2023, Saskatoon, Canada
JACoW Publishing
ISSN: 2 6 7 3 - 5 3 5 0
d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - T U 1 I 0 1

where the bunch position has fluctuated rapidly in horizontal
and vertical directions since three turns before the beamaborts.
We currently have only one bunch oscillation recorder ineach ring, so it is impossible to determine where the vibration started in the ring. It is also impossible to determine
whether the betatron phase advance accidentally obscured
the oscillations or whether the amplitude of the oscillations
was indeed small. To solve these problems, we started developing a new bunch oscillation recorder to be utilized inaddition to the existing bunch oscillation recorders. One
plan is a simple bunch oscillation recorder [11], which uses
analog hybrid circuits to process the signals from the button
electrodes and digitally sample them using an oscilloscope.

mounted bandpass filter, and low-noise amplifier will bemade soon. A novel RFSoC bunch oscillation recorder will
be put into commissioning as soon as possible after theSuperKEKB operation resumes in December 2023.

Figure 8: Schematic diagram of the RFSoC-based bunch
oscillation recorder.

REFERENCES

Figure 7: Sudden beam loss event measured with the bunch
oscillation recorder (courtesy of M. Aversano, Nagoya University).

RFSoC-based Bunch Oscillation Recorder
Another idea is the bunch oscillation recorder using the
Xilinx/AMD RF System on Chip (RFSoC), which contains
an 8-channel 12-bit ADC/DAC, FPGA, and Arm processor
in a single chip. This structure has the advantages of easy
handling without the need to design and implement communication lines between the ADC/DAC and FPGA andhigh-speed sampling to obtain bunch-by-bunch information.
The structure of the RFSoC-based bunch oscillation recordershown in Fig. 8 is as follows. First, a bandpass filter (center frequency of 0.5 − 2.0 GHz) placed upstream limits the
bandwidth. Next, a low-noise amplifier amplifies the signal
to compensate for the loss caused by the insertion of the
bandpass filter. The signal is then digitally down-converted
to baseband in RFSoC and decimated at 509 MHz. Finally,
the FPGA and the Arm processor convert the digital signal
to horizontal and vertical positions. The ring buffer memory
is saved after receiving the abort trigger signal and waiting
for a few turns.
We have started the first phase of development of theabove detector using RFSoC evaluation board ZCU111. Asof September 2023, the following two tests are underway:
1) Loop back the pseudo-signal created by RF-DAC to RFADC to test the implementation of digital down-conversion.
2) Create a pseudo-signal using a 125 MHz step recovery
diode and select the bandwidth with a 2 GHz comm-type
bandpass filter. A mezzanine card with a balun, surface-[1] T. Abe et al., “Technical Design Report of SuperKEKB”,
https://kds.kek.jp/indico/event/15914/[2] Y. Ohnishi, “Recent progress of SuperKEKB project andfuture prospect”, in Proc. IPAC’23, Venice, Italy, May 2023,
pp. 1321-1324.
doi:10.18429/JACOW-IPAC2023-TUOGB1[3] E. Mulyani et al., “First measurements of the vertical beam
size with an X-ray beam size monitor in SuperKEKB rings”,
Nucl. Instrum. Methods. Phys. Res., Sect. A, vol. 919, pp. 1–
15. doi:10.1016/j.nima.2018.11.116[4] G. Mitsuka, H. Ikeda, and T.M. Mitsuhashi, “Design andConstruction of Optical System of the Coronagraph for BeamHalo Observation in the SuperKEKB”, in Proc. IPAC’22,
Bangkok, Thailand, Jun. 2022, pp. 769–771.
doi:10.18429/JACoW-IPAC2022-TUOXGD1[5] G. Mitsuka, H. Ikeda, and T.M. Mitsuhashi, “Renovation of
the SR Beam Profile Monitors with Novel Polycrystalline
Diamond Mirrors at the SuperKEKB Accelerator”, in Proc.
IPAC’22, Bangkok, Thailand, Jun. 2022, pp. 313–315.
doi:10.18429/JACoW-IPAC2022-MOPOPT031[6] M. Tobiyama, H. Fukuma, H. Ishii, and K. Mori, “Development of Gated Turn-by-Turn Position Monitor System for the
Optics Measurement During Collision of SuperKEKB”, in
Proc. IBIC2013, Oxford, UK, Sep. 2013, paper MOPF32,
pp. 295–298.
[7] T. Naito et al., “Beam Oscillation Monitor for the Multibunch Beam”, in Proc. IPAC2013, Shanghai, China, May.
2013, paper MOPME018, pp. 506–508.
[8] Y. Funakoshi et al., “Orbit feedback system for maintaining
an optimum beam collision”, Phys. Rev. ST Accel. Beams,
vol. 10, p. 101001, 2007.
doi:10.1103/PhysRevSTAB.10.101001[9] M. Tobiyama et al., “Bunch by bunch feedback systems forSuperKEKB rings”, in Proc. PASJ’16 Chiba, Aug. 2016,
paper TUOM06.
[10] H. Ikeda, “Observation of sudden beam loss in SuperKEKB”,
in Proc. IPAC’23, Venice, Italy, May 2023, pp. 698-701.
doi:10.18429/JACOW-IPAC2023-MOPL072[11] M. Tobiyama, H. Ikeda, and G. Mitsuka, “Development of
Bunch Position Monitors to Observe Sudden Beam Lossof SuperKEKB Rings”, presented at IBIC’23, Saskatoon,
Canada, Sep. 2023, paper TUP002, this conference.

TU1I0101 Overview and Commissioning

135

Content from this work may be used under the terms of the CC-BY-4.0 licence (© 2023). Any distribution of this work must maintain attribution to the author(s), title of the work, publisher, and DOI

12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3