Preliminary Experiments of Coherent Cherenkov Radiation Matched to the
Circular Plane at KURRI-LINAC

N. Sei, T. Takahashi1
Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial
Science and Technology
1
Research Reactor Institute, Kyoto University

INTRODUCTION: The coherent Cherenkov radiation(CCR) is one of the intent light sources in the terahertz(THz) region. However, it is difficult to concentrate the
CCR beam efficiently because the CCR propagates in a
conical shape. Then, one of the author proposed a new
method for matching the wave front of the CCR beam tothe basal plane of a hollow conical dielectric by turning
the apex of the hollow conical dielectric toward the incident electron beam [1]. When the angle between the generatrix and the rotation axis is half of the radiation angleof the CCR generated on the inner surface of the hollow
conical dielectric, the CCR undergoes total reflection
from the conical surface and the CCR phase is matchedto the basal plane. We challenge to demonstrate the intent
THz wave source using the CCR matched to a circularplane wave (CCR-MCP) at a linac at the Kyoto University Research Reactor Institute (KURRI-LINAC).
EXPERIMENTS: In order to generate the CCR-MCP
beam, we use hollow conical dielectrics made of the highdensity polyethylene (HDPE). The refractive index andthe absorption coefficient of the HDPE are 1.53 and 0.02
cm-1 at the wavelength of 1 mm. Because the absorption
coefficient is low, an intent CCR beam can be expected touse the long hollow conical dielectric. Then, we prepared
two hollow conical dielectrics with the lengths of 40 and
80 mm. The inner diameter of the hollow conical dielectrics was 10 mm. The angle between the generatrix androtation axis was set to approximately 25, which was ahalf of the Cherenkov angle for the HDPE. Figure 1
shows the photograph of the hollow conical dielectricused in the experiments. An aluminum collimator, whose
length and inner diameter were 150 and 8 mm, was set infront of the hollow conical dielectric not to expose it to
the electron beam. A kapton film with a thickness of 50
m, which was located at 0.4 m from the hollow conicaldielectric downstream, was used to separate the CCR
beam and the electron beam. Because coherent transition
radiation was not generated at the kapton film, it could
reduce the background in the THz region. The CCR beam
was transported in the vacuum, and observed with a Martin-Puplett-type interferometer and a Si bolometer [2].
RESULTS: We performed experiments using an electron beam with the energy of 42 MeV at the KURRI-LINAC. The beam current passed the aluminum collimator was approximately 35 nA. Figure 2 shows interferograms measured with the Martin-Puplett-type inter-

28030

ferometer. It is noted that satellite pulses appeared awayfrom the zero pass difference (ZPD). The distance between the satellite pulse and the ZPD was proportional to
the length of the hollow conical dielectric, and the proportionality coefficient was the refractive index of the
HDPE. Therefore, these pulses were generated by theinterference between the CCR beam and coherent diffraction radiation generating at the exit of the aluminum collimator. The intensity of the CCR beam can be measured
by the increment of the base of the interferogram. The
measured CCR intensity indicated that the absorption
coefficient of the HDPE was 0.02 cm-1. We plan to measure the two-dimensional spatial distribution of the CCR
beam and to demonstrate the CCR beam to be the
CCR-MCP.

Fig. 1 Photograph of the hollow conical dielectric.

1.0
L = 80 mm
L = 40 mm
none

0.8

Intensity [ a.u. ]CO12-1

0.6

0.4

0.2

0.0
0

25

50

75

100

125

Optical length [mm]Fig. 2 Interferograms measured with the Martin-Puplett-type interferometer.

REFERENCES:[1] N. Sei et al., Phys. Lett A, 379 (2015) 2399-2404.
[2] T. Takahashi and K. Takami, Infrared Phys. & Technol. 51 (2008) 363-366.

CO12-2

Structural Analysis of Solid-Liquid Interface for Tribological Studyby Means of Multi-Analytical Methods Involving Neutron Reflectometry

T. Hirayama, N. Akamatsu1, H. Hattori2, F. Takagi2, M.
Hino3, N. Yamada4
Dept. of Mechanical Eng., Doshisha University1
Dept. of Mechanical Eng., Graduate School of Doshisha
University
2
Idemitsu Kosan Co., Ltd.
3
Research Reactor Institute, Kyoto University
4
Institute of Materials Structure Science, KEK

INTRODUCTION:
In recent years, reduction offriction and wear in machines is one of the mostimportant subjects from the viewpoint of global
environmental issues, energy conservation and resourcesaving. Especially, the development of materials having
excellent tribological properties is required to extend thelife of machine parts by reducing friction loss.
Particularly, under the boundary lubrication regime,
oiliness additives and extreme pressure agents are used toreduce friction and wear.
Sodium carboxylate is one of the most common additives
for friction reduction and anticorrosion, for example. This
report shows the structure of sodium carboxylate on themetal surface estimated by neutron reflectometry (NR)and its nanotribological properties measured by atomic
force microscope (AFM) with a colloidal probe.
EXPERIMENTAL RESULTS:
To investigate thestructure of sodium decanoate as one of sodium
carboxylates on Fe surface in water, NR experiment was
conducted. The obtained reflectivity profiles andestimated structure are shown in Fig. 1. From the fitting
operation, it was confirmed that the molecules of sodium
decanoate formed multilayer structure shown in Fig. 1(b)when the concentration of sodium decanoate wascomparatively large. On the other hand, when disodium
sebacate was used as a target additive, the fitting
operation for the NR profile presented the existence of
higher-concentrated molecule layer on the Fe surface, but
multilayer structure was not seen.
The friction forces measured by AFM with SiO2 colloidal
probe were shown in Fig. 2. We can see that the friction
forces decreased when the additives were mixed into
water. The friction force when the sodium decanoate was
mixed into water was smaller than that when the
disodium sebacate was used. The reason why was due tothe formation of multilayer structure obtained by thesodium decanoate molecules. It was confirmed that theformation of multilayer structure of molecules brings
large friction reduction, and we finally succeeded tomake a correlation between the interfacial additive
structure and the trend of friction force.

28060(a) NR profile(b) Estimated structure
Fig. 1. NR experimental result of sodium decanoate
on Fe surface in water(a) With sodium decanoate(b) With disodium sebacate
Fig. 2. Friction forces measured by AFM
with SiO2 colloidal probe in waterCO12-3

Effective Measures on Safety, Security, Hygiene andDisaster Prevention in Laboratories

T. Iimoto, R. Hayashi, Y. Seki, A. Fujimoto, M. Ishida, T.
Takahashi1 and S. Takahashi1
The University of Tokyo
1
Research Reactor Institute, Kyoto University

INTRODUCTION:
Important research aspects can be found in thefollowing keywords such as safety, security, hygieneand disaster prevention. Nuclear research reactor is
one of representative facilities together with these
keywords under their operation. It is effective toinvestigate the latest status on practical measures onthese keywords in various facilities including nuclear
research reactors, to compare each other among
facilities, and to discuss more optimized ones for our
positive safety management. Through this process, it isalso essential to investigate the latest international
and/or national regulations and the movement ofrevision of them. This total discussion contents and its
fruit are directly useful for all relating laboratories.
RESEARCH APPROACH:
General research approach is as follows.
- Measures of safety management during operation or
standstill status of the real facilities would be
investigated. This information would be used for our
research discussion on the positive and more
optimized safety management.
- It would not be a single year research, but maybe twoto three years research for one theme.
- Information source of facilities would not be only
KUR, KUCA or the other facilities in Kyoto
University, but also the Kinki university research
nuclear reactor or the facility of National Institute of
Fusion Science, etc. This research is an active
joint-research with these relating facilities andpositive researchers on safety management.
- One of the distinctive features of this research is to
involve office staffs as cooperators as well as
researchers and technical staffs. In The University ofTokyo, most of the members in Division forEnvironment, Health and Safety are office staffs who
knows real situation of safety management inlaboratories very well.
Discussion target in FY of 2016 was determined as
two items; “education framework, curriculum andtextbooks for safety managers and users as well as
relating officers to fill up the nuclear material
controlling sheet for the use of small amount of U andTh” and “safety culture improvement in radiation

28064

facilities” through our member discussion.
EDUCATION FRAMEWORK FOR SMALLAMOUNT OF URANIUM AND THORIUM
Safety education for the users of small amounts of U
and Th is not legally required. According to our survey
in the universities in Japan, most of the universities
use small amount of U and Th without education
and/or training to staffs and students. However, since2012, when new regulatory standards are applied, it
has been required to establish an organizational
structure, which ensures both user's technology
securing and safety management for the use of U and
Th. Currently, each university tries to establish a new
system of education and has begun to examine thecontents of education.
LATEST SITUATION ON RADIATION SAFETY
CULTURE IMPROVEMENT:We started to gather the real activities information on
the improvement of safety culture in international anddomestic radiation or chemical facilities. Here areexamples in The University of Tokyo.
- As a university headquarters, there is a mechanism togather information on accidents and incidents
occurring inside the university and to horizontallyshare the information. We are discussing
countermeasures etc. for them at regular meetings.
- We publish a mail-magazine as a university
headquarters and distribute it once a month for the
purpose of making it easy for all members tounderstand the content of accidents or troubles
occurring inside the university and the domestic trends
related to it. It is also possible to browse back issues atthe environmental safety portal website of theuniversity.
Good practices will be listed up, and how to sustain
and improve the motivation, skill and knowledge ofthe radiation safety officers will be the next target.
NEXT RESEARCH TARGETS:
We started to discuss on various activities for
improvement of safety culture in radiation facilities.
Related international and/or domestic investigationand discussion should be continued next year.
We express our gratitude for their strong support andactive discussion of Dr. K. Yasuda (Kyoto University),Dr. M. Takahashi, T. Saze (National Institute of Fusion
Science) and Dr. H. Yamanishi (Kinki University) andothers.

CO12-4

Development of a Micro-cell MWPC for a Muon-electron Conversion
Search Experiment, DeeMe

H. Natori, N. Abe1, M. Aoki2, Y. Furuya3, S. Mihara, F.
Morimoto3, D. Nagao2, Y. Nakatsugawa, T. M. Nguyen2,
H. Nishiguchi, Y. Seiya3, T. Takahashi1,Y. Takezaki3, N.
Teshima3, K. Yamamoto3
High Energy Accelerator Research Organization (KEK)1
Research Reactor Institute, Kyoto University
2
Department of Physics, Osaka University
3
Department of Physics, Osaka City University

INTRODUCTION: Discovery of Higgs boson filled
the last piece of the Standard Model (SM) of elementary
particle physics. The next coming issue is the physics
beyond the SM (BSM). A discovery of mu-e conversion
may be a clear clue to the BSM. DeeMe is going tosearch for mu-e conversion in J-PARC. The detector isrequired to tolerate to prompt burst pulses with an instantaneous hit rate of approximately 100GHz/mm2 andwidth of 200ns and to detect electron signal with delay
time of O(μs) from the burst pulse. We have invented a
new technique of dynamic gain control of wire chamber
to avoid a long dead time by space charge effect.
EXPERIMENTS: Experimental setup is shown schematically in Fig. 1. Electron beam collimated to 18mm x
20mm penetrates a Multi-Wire Proportional Chamber(MWPC) and beam counters. Beam rate is tuned changing current of electron gun heater.
Intensity control byheater power
Accelerator

e- gunPulse electron Field emission electrons
200ns width
Flat time distribution
within 4us of RF injection

Acrylic board& PMTsCherenkov light

MWPC

Accelerator

Collimator

ND filter
Attenuate 10-3

Plastic
scintillator& PMT

bles sweeping electrons generated by a burst pulse without giving avalanche multiplication and enables thechamber to give avalanche multiplication for delayed
signal electron without suffering gain reduction by spacecharge effect. This, on the other hand, induce large current on the cathode strip readouts by the rapidly changing
voltage on the potential wires. Amplifier should copewith this input. Fig. 2 shows the circuit of our amplifier.
We tuned the circuit elements not to make the amplifier
saturated by the large current input. Pole zero cancelation
circuit is implemented between 2-staged amplifiers tocompensate slow tail by ion movement. We have manufactured the final version of the chamber and the amplifier. This experiment was planned to be a test of the final
detector system under the condition equivalent to thefinal DeeMe condition.

Fig. 2. Circuit diagram of the amplifier
RESULTS: The DeeMe MWPC with HV switching
worked stably under the DeeMe final experiment compatible condition, electron pulse with instantaneous hit
rate of 100GHz/mm2 , width of 200ns and repetition of
25 Hz. Delayed electron from field emission electrons
was observed by the MWPC without gain reduction by
space charge effect. We also performed tuning of
Pole-Zero Cancellation circuit in our amplifier. We could
confirm our final chamber works well in the final experiment compatible condition.

Fig. 1. Experimental setup
The pulsed electron beam with tuned beam rate generated
from the beam gun emulates the prompt burst pulse. Delayed electron signals are emulated by field emission
electrons.
DC high voltage (HV) is applied to anode wires.
MOSFET based switching module makes a pulsed HV to
be applied to potential wires of the MWPC. During amain pulse comes, HV is applied to potential wires tomake voltage difference between wires 0V. Soon after themain pulse passes the MWPC, potential wires are
switched to ground level to make large voltage difference
between anode-potential wires to detect delayed electrons.
We developed this HV switching technique, which ena-

28067

REFERENCES:[1] H. Natori, et al., Prog Theor Exp Phys (2017) 2017(2): 023C01.
“A fast high-voltage switching multiwire proportional
chamber”

CO12-5 Electron Beam Test of Avaranche Photodiode for Ganymede Laser Altimeter ofJovian Icy Satellite Exploerer
M. Kobayashi, O. Okudaira, K. Ishibashi, M. Fujii1, T.
Takahashi2 and N. Abe2
Planetary Exploration Research Center, Chiba Instituteof Technology
1
FAM science2
Research Reactor Institute, Kyoto University

INTRODUCTION: The Ganymede Laser Altimeter(GALA) as part of the JUICE (Jovian Icy Satellite Explorer) payload is one of the instruments focusing on aspects related to the presence and characterizations ofsubsurface water oceans [1] [2]. For the first time thetime-variability of the global figure of a moon due totides exerted by Jupiter will be detected by altimetry
measurements.
Japan team of GALA has a responsibility forback-end optics, optical sensor and analog electronics
module of the receiver part of GALA instrument. We
adopted an avalanche photo diode (hereafter APD) product manufactured by Excelitas Technologies, Montreal in
Canada. Their APD product that are customized for space
use have been adopted for many space missions due to its
compactness and heritage in space.
The APD has also sensitivity to radiation that induceshole-electron pair in the depression layer. In space environment, the induced signal may affect light detection as
background noise, called radiation noise. Jupiter has astrong magnetosphere and previous studies revealed energetic electrons are trapped in the magnetosphere andmajor component among the other ionizing radiation like
proton and the other energetic ion. The APD will beshielded up against to the Jovian radiation environment
however some of electrons can penetrate the shield into
the APD. In this study, we used KURRI-LINAC as anelectron beam source to emulate electrons irradiating the
APD to investigate how energetic electron induces signals and interferes the returning laser pulse signal.
EXPERIMENTS: As device under test, we used acommercial APD module, LLAM-1060-R8BH of Excelitas Technologies, on which the flight APD module isbased. The module is designed as commercial product but
the sensor used in the module is one from a sensor chip
lot selected as the flight lot. The APD sensor has a diameter of 0.8 mm and an enhanced sensitivity in infrared
range, about 0.4 of quantum efficiency at 1064 nm. They
commercially manufacture APD product particularly ahybrid module of APD which contains an APD sensor, apreamplifier, a thermo-electric controller and a temperature sensor in a package.
We performed twelve runs of the LINAC and electrons was accelerated to six different energies for irradiation to the DUT, 3, 5, 10, 20, 30 and 40 MeV. Irradiation
angle is changed to be 0º (straight forward), 60º and 180º(backward). For a run with 40MeV, stainless steel plate28071

was set in the front of the DUT, simulating the structureof focal lane assembly in which multiple scatter of electron was expected to occur. The output signals of the amplifier were recorded with a digital oscilloscope.
RESULTS: The pulse shape of radiation induced noise
might be similar to the stop pulse of GALA, the pulse
width ranges 10 – 200 nsec. If radiation induced noisefeatures such pulse shape as that, RFM (range Finder
Module) may detect it as false detection.
In the test, the single short pulse per electron hit on
the APD sensor has a rise time of 2 – 3 nsec and a falltime of 2 – 3 nsec for any energies and any incident angleof electrons. The DUT of LLAM-1060-R8BH has a system bandwidth of 200MHz, so the rise time and fall timeare expected to be 1 – 2 nsec, while the results in this test
show slower rise and fall times.
Fig. 1 shows examples of signal waveform of typicalsignal events from the test. In the figure, the signal heightof 5 MeV and 0deg is almost same as one of 40MeV and0deg, while the signal with 5MeV and 60deg has a higher
signal height that the others. For 0deg irradiation, mostevents for typical 0deg incident (whatever its energy is)show short width, 2nsec for rise time and 2nsec for falltime. The slower rise and fall times than expected would
be caused by signal delay in a cable connecting the APD
module output to the oscilloscope for readout, the cable
length was 50 cm. GALA APD has a system bandwidthof 100MHz, and the cable length between the APD module output and the following amplifier will be 15cm at
maximum, therefore, radiation induced noise on GALA
APD has similar pulse shape to the results of this test.
The pulse shape of radiation induced noise is typicallysimilar to one of the start pulse of GALA laser, but notstop pulse (receiving from the Ganymede). The timing ofreal start pulse is known, so the false start pulse can be
distinguished by timing.

Fig. 1. An example of output signal pulse from the
APD.
REFERENCES:[1] Althaus, C. et al., LPI Contribution No. 1980, id.4015,(2016).
[2] Steinbrügge, G. et al., Planet. Space Sci. 17, 184-191(2015).

CO12-6

Single Event Test using 252Cf for On-board Computer used in Lean Satellite

H. Masui, H. Fukuda, S. Kawano, A. H. Kafi, M. Cho and
K. Takamiya1
Laboratory of Spacecraft Environment Interaction
Engnieering, Kyushu Institute of Technology
1Research Reactor Institute, Kyoto University
INTRODUCTION: Kyushu Institute of Technology(Kyutech) has been developing nano satellites since 2010.
Kyutech are developing the suitable radiation test methodfor Lean satellite as nano/micro satellite. In the Lean satellite, it is more important to evaluate the reliability of thesystem than to evaluate the reliability of chips and parts.
In other words, the implementation of the reliable reset
system is important for the Lean satellite. In the radiation
effect on the microprocessor, Single Event Latchup (SEL)
is the most critical problem. The bas system such as onboard computer (OBC), electrical power system (EPS) andcommunication (COM) of Horyu-4[1] developed by
Kyutech was tested in Kyoto University in 2015.
However, the radiation effect on the mission part was nottested. In order to guarantee a long time mission, theradiation test on the mission part is essential. In FY2016,
we conducted the checking reset system during mission
part operating. In addition, Kyutech are developing
cubesat as “BIRDS-1”[2]. BIRDS-1 has on-board
computer almost similar to Horyu-4. The purpose of thistest is to improve the stability of satellite system under theeffects of radiation. This doc-ument reports the detailof testing and test results of Horyu-4 .
EXPERIMENTS: Figure 1 shows the experimental setup. Circuit boards used in this test were Engineering
Model for Horyu-4 and BIRDS-1. These boards have two
H8 microprocessors (H8-1 and H8-2). The plastic
package of microprocessors was removed so that thecore of the microprocessors was directly exposed to 252Cf
source. The circuit boards were set in a vacuum chamber.
The pressure during the test was approximately 30 Pa.
The voltage and current fed from the power supply were
measured by a DAQ and oscilloscope and the operationof the micropro-cessors was verified by a PC with RS232
communication. An over-current protection (OCP) was
implemented in the power line between each sub-system
and EPS in the circuit boards. Once OCP detects overcurrent due to SEL on the OBC, OCP sends a reset signal
to EPS. To recover from the hang-up state of OBC by
SEL, EPS automatically cuts the current from EPS to
OBC. In this experiment, 252Cf source was mounted on
XYZ stage. According to Horyu-4, we found that thesatellite system operation becomes unstable during
operating Attitude and Orbit Determina-tion System(AODS) in preliminary test results. We spe-cificallychecked that the operation of the reset system whenmain mission, sub-system and AODS were operated. In
the test, 252Cf source was moved above microprocessors
and radiation was irradiated to two microprocessors after
operating each system. We investigated whether the satel-

28085

lite system can automatically be recovered or can be recovered by the reset command from the PC from the SEL
state.
RESULTS: Table 1 shows the summary of test resultsfor Horyu-4. Horyu-4 system could automatically recoverfrom SEL state during operating main mission and AODS.
However, the satellite system could not recover when SEL
occurred during simultaneous operation of AODS and subsystem (camera etc.). In addition, the satellite could not recover when SEL occurred during operating some sub-systems. Therefore, it was found that simultaneous operationof the main mission and AODS for a long time is possible.
On the other hand, we must take into account of the highpossibility of SEL failure for simultaneous operation of
AODS and sub-system.

Fig. 1 Test setup of Horyu-4 and BIRDS-1
Table 1 Summary of Horyu-4 test results
Operating part

H8-1

H8-2

1

Main mission

Pass

Pass

2

AODS

Pass

Pass

3

Main mission + AODS

Pass

Pass

4

AODS + Sub-system

Fail

Fail

5

Sub-system

Fail

Fail

6

Main mission + Subsystem

Fail

Fail

“Pass” means that satellite could recover from SEL state
by automatically or command.
REFERENCES:[1] T. Shimizu et al., J. Spacecraft and Rockets. 54, 2497499 (2016).
[2] G. Maeda et al., 67th International Astronautical Congress IAC-16.B4.1.4 (2016).