20
Bull. Soc. Photogr. Imag. Japan. (2019) Vol. 29 No. 2: 20–26

Original Paper

Desensitized Nuclear Emulsion Films for Measuring the Chemical Compositionof Cosmic-ray Nuclei
Saya Yamamoto*, Shigeki Aoki***, Atsushi Iyono**, Keita Ozaki***, Satoshi Kodaira****, Misato Yabu***

Abstract:

Highly sensitive nuclear emulsion films and high-speed imaging technology have been developed for recording tracks of minimum ionization particles such as cosmic-ray muons and electrons. The ionization energy of the heavy ions in cosmic rays is too high to identify the individual nuclear charges because the signal of pulse-height volume for tracks is saturated on this system. We have developed desensitized nuclear emulsion films by adding a rhodium compound (Na3RhCl6∙5H2O). This modification reduces the film's sensitivity to heavy ions by 37%,
resulting in better linearity between ionization energy and the signal of the tracks. The signals due to heavy ions were compared with the signals recorded on a CR-39 nuclear track-detector. The desensitized nuclear emulsion films successfully distinguished adjacent nuclear chargesof heavy ions.

Key words:

Nuclear emulsion film, Cosmic-ray nuclei, CR-39, Rhodium compound, Nuclear track detector

1. Introduction
Recent innovations in producing nuclear emulsion have enablednovel experiments in particle physics. Emulsion gels have been produced with various grain sizes and various types of silver-halide
weight-content (in the emulsion) 1). Films coated with these gels canrecord charged particle tracks with sub-micrometer spatial resolution2) and diminish the prevalence of latent image specks under thehighly humid environments1) (refreshing process). The swelling process was also well operated to restore the original thickness of emulsion layer3). These processes are used to image neutrinos in the OPERA4) and NINJA5) experiments, search for MeV cosmic gamma
rays in the GRAINE experiment6), 7), and for muon tomographic
imaging of volcanoes, blast furnaces and the pyramids at Giza8). Furthermore, these applications also depend on the high-speed
track-recognition system that is used to analyze tracks recorded innuclear emulsion films. The Hyper-Track Selector (HTS) instruments has increased the scanning speed for digitizing images of
emulsion film to recognize track information without huge image
data set. Owing to this development, nuclear emulsion films havebeen used in several experiments in which spatial resolution and angular resolution are required to be less than one micrometer and lessthan milliradians, respectively. In these high-performance track
analyses, the read-out systems are adjusted to detect minimum ionized particles (MIP). Signals by high atomic-number (Z) particles

like heavy nuclei would be saturated and such particles cannot be
identified each other.
Emulsion technologies are used to detect cosmic gamma rays
with new nuclear emulsion films in the GRAINE balloon flight experiments6), 7). In these experiments, the tracks of electron and positron pairs formed by gamma-ray conversion in the detector must be
distinguished among the huge number of noise tracks. These films
are very useful for recognizing the trajectories efficiently. Detection
performance for cosmic-ray nuclei with these films is limited, however, because the HTS analyses are optimized for detecting MIP
tracks like those left by electrons.
The majority, 99%, of cosmic-ray nuclei are composed of hydrogen and helium. Only one percent of cosmic-ray nuclei are heavier
nuclei like C, N, O or Fe. These heavier species provide information
about the origin, acceleration mechanism and propagation of cosmic-ray nuclei. The elemental abundance of cosmic-ray nuclei above
Z = 30 can reveal the origin of the cosmic ray, which may include
supernova explosions, rapid-process and slow-process neutron capture, neutron-star mergers9), stellar nucleosynthesis or the chemical
evolution of the galaxy. The emulsion films lifted up to the height of
40 km above sea level in the GRAINE experiment recorded cosmic-ray nuclei. Highly ionized particles such as high atomic number(Z) particle or low energy particle, however, are eliminated by the
HTS algorithm during image analysis. To bring out the best abilityof HTS system, we have decided to produce desensitized nuclear
emulsion gels by controlling the chemical compounds added. The

Received 25th July 2019; Accepted 14th December 2019
*Graduate School of Science, Okayama University of Science, 1-1, Ridai-cho, Kita-ku, Okayama-shi, Okayama 700-0005, Japan**Faculty of Science, Okayama University of Science, 1-1, Ridai-cho, Kita-ku, Okayama-shi, Okayama 700-0005, Japan***Faculty of Human Development, Kobe University, 3-11, Tsurukabuto, Nada-ku, Kobe-shi, Hyogo 657-8501, Japan****
National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba-shi, Chiba 263-8885, Japan

Saya Yamamoto, Shigeki Aoki, Atsushi Iyono, Keita Ozaki, Satoshi Kodaira, Misato Yabu

tracks made by heavy cosmic-ray nuclei in these desensitized films
behave as if they are MIP tracks in HTS analysis.
To calibrate the extent to which various chemical compounds desensitize the nuclear emulsion gels, we performed the heavy-ion irradiation experiments with several nuclei. We also compared the
HTS results against the etched pit size of solid-state track-detectorof CR-39 whose sensitivity is lower than that of the original nuclear
emulsion.

2. Methods and material
2.1 Automatic nuclear emulsion readout system
To obtain data about ion tracks such as positions, angles and ionization loss in nuclear emulsion film, microscopic measurements
have to be taken after the films are developed with chemicals. Although this analysis was once done manually with a microscope andwas consequently very time-consuming, the development of theHTS2) allows us to obtain track data in extremely short times.
The HTS readout system has a very wide field of view and reaches a scanning speed of 4700 cm2/h in recognizing single tracks. To
utilize the HTS abilities for detecting highly ionized particles, thesetracks must be made to resemble the tracks by MIPs. The pulse
height volume (PHV) data output by HTS scanning can be used to
identify nuclear species via the total amount of ionization energy
loss along the tracks. The PHV signal by highly ionized particles
such as relativistic heavy ions is saturated in typical high-sensitivity
nuclear emulsion film because many knock-on electrons lay along
them and the field of view (FoV) of HTS filled up with them. Delta-rays also make the PHV fluctuate because some delta-rays go out
the FoV of HTS. The PHV in desensitized nuclear emulsion films
are therefore utilized for measuring ionization losses along the
tracks, similar to classical track-width measuring methods11).
PHV values can be used to detect heavy ions with three modifications: (1) higher illumination in image analysis, (2) shorter chemicaldeveloping time or (3) desensitized nuclear emulsion film. The
HTS's light intensity is limited by the uniformity of the wide FoV
and changing the chemical development process might have unpredictable results. We therefore selected the third option for testing.

Desensitized nuclear emulsion films for measuring the chemical composition of cosmic-ray nuclei

2.2 Desensitized nuclear emulsion films and solid-state track detector
We tested two types of nuclear emulsion gel with different silver-halide weight-content in the emulsion gel. This follows the difference of volume-occupancy by silver-halide in the gel. High-volume-occupancy gels have silver bromide crystals taking up
approximately 55% of the gel's volume (abbreviated as H). Middle-volume-occupancy gels have silver bromide crystals taking up
approximately 45% of the gel's volume (abbreviated as M).
To desensitize the nuclear emulsion film, sodium hexachlororhodate (III) 5-hydrate (rhodium compound, Na3 RhCl6 ∙5H2 O) was
added when producing the nuclear emulsion gel or 2,3-bis (4-methoxyphenyl)-5-phenyltetrazolium chloride (tetrazolium compound, C21 H19 ClN4 O2) was added to the nuclear emulsion gel
before applying it on a film base. The sensitivity can be controlled byadjusting the total amount of each additive. We prepared three typeof desensitized emulsion films for testing. We added rhodium compound into the no ripening samples to achieve a rhodium concentration of 2.5 μmol/Ag mol (abbreviated as NRHRhS in the following section) and 5.0 μmol/Ag mol (abbreviated as NRHRhL),
respectively. The tetrazolium compound was added into the ripening
sample at a concentration of 20 μmol/Ag mol (abbreviated as
NRHTz). These samples are summarized in Table 1.
We applied a nuclear emulsion gel consisting mainly of silver bromide to both surfaces of a plastic film base to make samples of nuclear emulsion film. The thickness of the nuclear emulsion layer was
designed to be 60 μm on both sides of the plastic films, whose thickness was 180 μm. Therefore, the total thickness of each nuclear
emulsion film was nominally 300 μm. These emulsion films wereprepared at Nagoya University in Japan1), 7).
CR-39 plate (Sun9 produced by Sunlux Co. ltd.) was deployed at
the furthest downstream side of the chamber. CR-39 is a solid-state
nuclear track detector that allows us to determine energy loss ofbeam by measuring the size of the pits formed on the detector due
to incident ions.

3. Irradiation experiment of heavy ion beams
3.1 Irradiation experiment
To calibrate the sensitivities of the desensitized emulsion film
samples, we irradiated each emulsion film with heavy ion beams ofTable 1 L
 ist of nuclear emulsion films used here with numbering and abbreviations.
Number Abbreviation
1

2

RM

NRH

21

Type of nuclear emulsion films

Ripening and middle-volume occupancy

No ripening and high-volume occupancy

3

NRHTz

No ripening and high-volume occupancy

4

NRHRhSNo ripening and high-volume occupancy

5

NRHRhLNo ripening and high-volume occupancy

Additive
None
None

Tetrazolium
compound20 μ mol/Ag mol

Rhodiumcompound2.5 μ mol/Ag mol
Rhodiumcompound
5.0 μ mol/Ag mol

22

Bull. Soc. Photogr. Imag. Japan. Vol. 29 No. 2 (2019)

Table 2 L
 ist of high-energy ion beams used here. Irradiation energy was 350
MeV per nucleon for each ion.
Irradiation
particle
Li

Be
B

C

Electric
charge3

4

5

6

Irradiation energy[MeV/n]
350

350

350

350

Ionization energy loss
[MeV cm2g-1]
22

40

62

90

lithium, beryllium, boron and carbon with energies of 350 MeV per
nucleon. These tests were performed at HIMAC (Heavy Ion Medical Accelerator at Chiba) in National Institute of Radiological Sciences on October 26, 27 and 31 in 2017. The beam characteristics
are summarized in Table 2.
For these tests, we constructed an emulsion chamber block withfive types of emulsion films and a CR-39 plate, which is shown in
Fig. 1. The exposed dimension of the chamber was 50 mm × 50 mm
and its thickness was 85 mm. Four chambers shown in Fig. 1 wereprepared for each ion beam exposure.
The direction and amount of irradiation applied in these tests are
summarized in Table 3. We tilted the chambers toward the z direction of each beam shown in Fig. 1, at 0°, 20° and 40° and toward they direction of each beam at 20°.
3.2 Processings of nuclear emulsion films and CR-39 plates
We developed the nuclear emulsion films12) after the irradiation
experiments. The NRHTz films were blacked out over the entire
surface. The other emulsion films were developed without any errors.
After developing, we scanned the nuclear emulsion films with HTS,
after we swabbed them to remove silver deposits and swelled them.
The swelling processes were carried out to restore the original thickness of nuclear emulsion layer by bathing in 20°C to 30°C water and
30% to 35% glycerin aqueous solution for the adequate duration.
As the films were swelled, black specks appeared in the sensitized

Fig. 1 S chematic structure of the chamber. Numbering of the nuclear emulsion films is summarized in Table 1.

Table 3 B eam direction and total amount of ions. These angles are given indegree unit in both x and y directions shown in Fig. 1
Direction (x degree, y degree)

Amount of irradiation (/25 cm2)(0, 0)

8×104(40, 0)4×104(0, 20) for calibration(20, 0)

4×104

4×104

Fig. 2 ( a) Photograph of a nuclear emulsion film (RM) in the carbon irradiated chamber, (b) Photographs of sets of three pieces with nuclear
emulsion films (RM) irradiated with each ion. The scale of one film is
5 cm × 5 cm.

and middle-volume occupancy emulsion films, as shown in Fig. 2-a.
As one can see in Fig. 2-b, black specks appeared most frequently inthese three pieces of ripening emulsion film (abbreviated as RM)
when exposed to carbon ions. The variations in the frequency of
black specks caused by the four different ions in the same film arestill not understood. The black specks are typically more than
100 μm in diameter. HTS ordinarily recognizes large size black objects as noise2) by applying a low-pass-filtering algorithm. Theselarge black specks were eliminated from the digitized track data, but
fragments of these specks affected the estimation of the ionizationenergy described below.
We chemically etched the exposed CR-39 plates with 1 mm original thickness, in the 30 wt% aqueous sodium hydroxide solution at
a temperature of 80°C for 60 minutes. The etched pit sizes along
both major and minor axes have been measured by using HSP-1000
developed by Kodaira et al13).
3.3 Emulsion Scanning
HTS recognized tracks in the following procedures; ① we binarized the image of each tomograph, ② we searched black pixel
groups in each layer which were connected each other through 16
layers, ③ we considered the chain of black pixel group as a track andestimated three-dimensional information, such as position (x, y, z)
etc., ④ we shifted the coordinate of each group as the line of pixel
group through layers was perpendicular to the film, ⑤ we counted
the number of pixels which were black in the 16 layers at each coordinate position of the pixel, ⑥ we defined the maximum value of
pixel number in the group as PH, ⑦ we obtained the number ofblack pixels at the coordinate position of each pixel within the pixels
whose number was greater than 9 in the 16 layers and summed up
the number in the black group and ⑧ we defined this sum as PHV
value for the track indicated by the black group. After all these pro-

Saya Yamamoto, Shigeki Aoki, Atsushi Iyono, Keita Ozaki, Satoshi Kodaira, Misato Yabu

Fig. 3 C onceptual diagram of the algorithm to obtain PH (pulse height)
and PHV (pulse height volume).

cedures, HTS returns data about three-dimensional positions (x, y,z) at the end of track touching the plastic film base, incident andorientation angles to the emulsion film, pulse height (PH) and PHV.
HTS provides the horizontal coordinates (x, y) with an accuracy of
0.5 μm, the resolution along the optical axis (depth coordinate: z)
became 2.1 μm2). The incident angle can be determined with an accuracy of 2.8 mrad by comparing the track positions on both sides ofthe plastic film base (180 μm). PHV is an indication of the size ofionization energy loss for MIP, gray track, black track and highly
ionized particles. PHV indicates the degree of ionization loss perunit track length, which ranges from 0 to 1024 per emulsion layer. A
schematic view of the HTS process is shown in Fig. 3.

Desensitized nuclear emulsion films for measuring the chemical composition of cosmic-ray nuclei

23

between the irradiation experiments and development. Kuge et al.8)
reported that tetrazolium compound greatly increases the sensitivityof the nuclear emulsion film when it is stored in a vacuum. Fig. 4-a,-b and -c show the PHV distributions of each ion in RM, NRHRhS
and NRHRhL films, where the obtained PHV data are summed
values with both emulsion layers in the three films. In Fig. 4-a, thePHV values for each ion are distributed in the PHV range from 400
to 800. Though the PHV ranges of Li and those of the other higher-charged ions are separated, distributions of PHV for Be, B and C
ions overlap and cannot be separated. So, in case of RM, we cannot
distinguish what kind of ion forms the track. In case of NRHRhS
emulsion films shown in Fig. 4-b, each PHV value for Li to C ionscan be distinguished. The PHV distributions in the most desensitized nuclear emulsion film (NRHRhL) are shown in Fig. 4-c. PHVvalues are smaller than those of RM or NRHRhS and no PHV

4. Results
4.1 Analyses of PHV distribution
We have analyzed the PHV distributions of C, B, Be and Li ionsat the beam energy of 350 MeV per nucleon in RM, NRHRhS,
NRHRhL films except for NRHTz films which were blacked out.
Those NRHTz films were preserved in a vacuum over the fifty hours

Fig. 5 C orrelation of PHV with ionization energy loss. Blue, orange andgray dots represent types of nuclear emulsion films of RM, NRHRhS
and NRHRhL, respectively.

Fig. 4 A nalyzed PHV distribution for each emulsion film and each ion.

24

Bull. Soc. Photogr. Imag. Japan. Vol. 29 No. 2 (2019)

Fig. 6 D ependence of irradiation angle to the average of PHV at NRHRhS
sample. Blue, green, red and yellow dots correspond to carbon, boron,
beryllium and lithium ion beams, respectively.

signal corresponding to Li ions appeared. In this emulsions, Be, B
and C ions were identified in the PHV range of 100 to 700. The
separation ability between ion species is similar to that in the
NRHRhS emulsions.
To compare the peak values of PHV for Li, Be, B and C ions with
their ionization energy losses in the middle-volume occupancy
emulsion film, we calculated these ionization energy losses by using
Bete-Bloch formula14), which are listed in the fourth column of Table 2. In Fig. 5, the peak positions of the PHVs for Li, Be, B and C
ions obtained in Fig. 4 , were plotted as a function of ionization energy losses listed in Table 2.
The relationship between PHV and the incident angle of the ion
beam has been discussed in several papers15). To determine how
PHV depends on the incident angle, we exposed emulsion chambers
at three different alignments to the beam line. The averaged PHV
values in NRHRhS samples for each ion are plotted as a function ofincident angles in Fig. 6. When the front side of the emulsion chamber is perpendicular to the beam line (0°), the PHV values are thesame as those shown in Fig. 4-b. At the incident angle of 20°, thePHV decreased for B, Be and Li ions but not for the C ions. On theother hand, at 40° incident angle, the PHV values for Be, B and C
ion except Li ion increased from those values at 20°.

4.2 
Correlation of PHV and etched pit-size of solid-state
track-detector (CR-39)
We deployed CR-39 solid-state track-detectors downstream ofeach emulsion chamber to calibrate the PHV values via comparison
with the etched pit sizes along the minor axis. This test follows Kuge
et al.'s calibration of comparing the OPERA film produced by Fuji
film PHV and CR-3916). They reported the saturation of PHV.
The distributions of etched pit size along the minor axis for theions hitting perpendicular to the beam line are shown in Fig. 7.
These distributions were also fitted by Gaussian functions aroundtheir peak position. We obtained the averaged etched pit size from
Be, B and C as 1.80±0.18, 2.03±0.16 and 2.37±0.14 μm, respectively.
Li ions do not make any etched-pits and cannot be detected on CR39. The second small peak of etched pit size in the C ions lay around
1.5 μm. This would come from the secondary fragments of C ions.
Finally, we compare the averaged PHV values with the minor axesof etched pit size for Be, B and C ions recorded on NRHRhS in Fig.
8-a and on NRHRhL in Fig. 8-b. The PHVs in both desensitizedemulsion plates correlated to the etched pit sizes very well. NRHRhS
gives slightly better linearity than NRHRhL does.

5. Discussion
To identify the charge of heavy ions, the ionization loss of eachFig. 7 H istogram of etched pit sizes at the minor axis recorded on CR-39
plate by each ion entered perpendicular to the plate. The etched pit
sizes were measured using HSP-1000. Each color (purple, green, blue
and red) of histograms corresponds to the irradiated ions of Li, Be, B
and C, respectively. Gaussian-distribution fitting to each peak is also
shown as colored lines of yellow, blue and red, respectively.

Fig. 8 C orrelation of PHV at (a) NRHRhS and (b) NRHRhL with the etched pit size.

Saya Yamamoto, Shigeki Aoki, Atsushi Iyono, Keita Ozaki, Satoshi Kodaira, Misato Yabu

track in terms of PHV in the desensitized nuclear emulsion films
was used. In case of NRHRhS, the peak values of PHV estimatedfrom the distribution of PHV in Fig. 4 were well expressed as alinear function of the calculated values from Bete-Bloch ionization
formula except for Li ions. In the RM films, PHV values for each
ion were around 600. We cannot distinguish the ions from each other in this case. Therefore, in order to identify the charge of heavy ionswith nuclear emulsion film and HTS system, the PHV values for thedesensitized films are valuable to obtain the effective information.
This mechanism is equivalent to traditional track width measurements made with photo-metrical methods11). Heavy ions typically
produce a lot of knock-on electrons (delta-rays), with energies above
5 keV and the delta-ray range spectrum should be used to determin
the Z2/β2 factors of ionization energy losses, where β is the speedof particle relative to the one of light, c. This is called the delta-ray
count method. Delta-rays with energy less than 5 keV are partiallyeffective in the formation of latent images along the track, which isreferred as effective local ionization. But the delta-rays with energy
from 5 keV to the maximum kinetic energy ∼2me c2 tend to be tied
into knots by scattering and are therefore closely confined to theregion of the trajectory of heavy ions. Therefore, these delta-rays
would be cause PHV increase and finally be saturated in digital image analysis.
Furthermore, the HTS system accumulates binary pixel values intomographic images along the track to determine track likelihoods
and integrates all total pixel numbers above the threshold(PH ≧ 9)
to obtain the PHV of each track. The PHV for Be, B and C was
saturated in the RM films because delta-rays of energy above 5 keVtravel for several micro meter, overlap with each other and normallyspill over the HTS window size (26 μm × 26 μm). On the other
hand, the HTS system focuses on the analysis of single charged particles without higher-energy delta-rays to distinguish electrons, mesons and baryons produced by reactions of elemental particles, because those particles leave latent images via delta-rays of energy lessthan 5 keV. So we actively eliminate delta-rays from heavy ion tracks
in order for HTS to recognize these tracks as being MIP or lower
ionized particles. Therefore, we decided to desensitize nuclear emulsion films.
The desensitization of nuclear emulsion film suppresses the production of delta-rays. Consequently, by using PHV obtained from
HTS, the sensitivities of NRHRhS film was reduced by 37% relative
to the RM film and that of NRHRhL films was reduced by 54%
relative to the NRHRhS film for a Li beam as shown in Fig. 5, when
we regard the PHV value as a sensitivity of films. In this figure, thePHVs and their ionization energy losses are well correlated, for the
NRHRhS film. Thus, we can control the sensitivity of nuclear emulsion films by changing the amount of added Rh. On the other hand,difference of PHV values for each ion in NRHRhL emulsion films
is less enhanced relative to NRHRhS films. Further investigation isrequired to clarify this feature.
Since the peak values of PHV for each ion were well separated in
the NRHRhS emulsion films, we can distinguish each ion clearly. To
apply PHV measurement by desensitized films for cosmic ray experiments, the linearity of PHV and density of rhodium compound

Desensitized nuclear emulsion films for measuring the chemical composition of cosmic-ray nuclei

25

would be preferable, because we have to extrapolate it to heavier
charged particles than the ones used here in heavy ion beam experiments. Unfortunately, we cannot state a functional relationship between nuclear emulsion sensitivity and the total amount of added
rhodium compound. We would need to prepare more samples withdifferent amounts of added rhodium to establish this relationship.
The shadowing effect of overlapped grains also affects the HTS
analysis. We have verified dependence of incident angle to PHV
values for Li, Be, B and C ions. Grain-overlapping effects in PHV
have been observed for B, Be and Li ions at the incident angle of 20°.
At the incident angle of 40°, the PHVs of Be, B and C ions increased
from these values at 20°. In the image analysis, HTS is applied toimage filtering to eliminate noise and to reconstruct off-focus grains.
Further details of HTS image processing can be found in Section
3.5 of the paper by Yoshimoto et al.2) These image analysis processes
are complicated in simulating the observed PHVs. Therefore, wemust analyze the correlation between PHV and incident angles forheavier charged particles.
It is indispensable to combine solid-state detector such as CR-39
and nuclear emulsion films, because previous nuclear emulsion films
with high sensitivity could not distinguish high energy particles
each other. Whereas desensitized films can measure ions of Li, Be, B
and C by adjusting the sensitization level of films properly, and measured results were well-consistent with the ones with CR-39. Therefore, we need not to use the hybrid system of films and CR-39 by theuse of films desensitized properly.

6. Conclusion
To assess the sensitivities of nuclear emulsion films with or without the addition of rhodium compound evaluated by the PHV signals that indicate the ionization energy losses of a heavy ion beam,
we exposed samples of nuclear emulsion films to 350 MeV-per-nucleon heavy ions at the HIMAC facility. We prepared five nuclear
emulsion films with different sensitivity. The sensitivity of NRHRhS
was decreased by 37% relative to that of RM and that of NRHRhL
was decreased 54% relative to that of NRHRhS.
In the RM and NRHRhS films, we successfully obtained PHV
distributions for the Li, Be, B and C beams. On the other hand, Liions left no tracks in the NRHRhL films. In the RM film, we did
not obtain any linear relationship between PHV and ionization energy losses calculated from the Bete-Bloch formula for Li, Be, B, C
beams. In case of the NRHRhS and NRHRhL films, the PHV values are well correlated with the energy losses calculated from theBete-Bloch formula. The incident-angle dependency of PHV was
also examined and complex relationships were found. Finally, we
confirmed the validity of the PHV signal measurement with desensitized NRHRhS and NRHRhL films to detect high-energy particles. We will not need the hybrid system with films and solid-state
track-detectors such as CR-39.
We will be able to use the HTS in the F-lab. of Nagoya University for the exploration of long-duration balloon flights of the
GRAINE experiment to analyze the chemical composition of galactic cosmic-ray nuclei.

26

Bull. Soc. Photogr. Imag. Japan. Vol. 29 No. 2 (2019)

Acknowledgment

This work was supported in part by the joint research program of
the Institute of Materials and Systems for Sustainability, Nagoya
University. We wish to acknowledge valuable discussions and advises regarding the production and scanning of nuclear emulsion films
with the member of GRAINE experiments in the fundamental particle laboratory at Nagoya University. The authors would also like tothank Mr. K. Kuwabara, visiting researcher in the fundamental particle physics laboratory and Designated Prof. K. Ohzeki, Institute ofMaterials and Systems for Sustainability at Nagoya University, forpreparing chemical compounds for desensitizing nuclear emulsion
films used in this work.

References
1)
2)
3)

4)

K. Ozaki, S. Aoki, K. Kamada, T. Kosaka, F. Mizutani, E. Shibayama, S.
Takahashi, Y. Tateishi, S. Tawa, K. Yamada, H. Kawahara, N. Otsuka, H.
Rokujo, J. Instrum., 10, P12018 (2015).
M. Yoshimoto, T. Nakano, R. Komatani, Hiroaki Kawahara., Prog. Theor. Exp. Phys. 2017, 103H01 (2017).
Y. Nakamura, GRAINE collaboration, Balloon Symposium: 2018(sas18-sbs-011), Institute of Space and Astronautical Science, Japan
Aerospace Exploration Agency ( JAXA)(ISAS), Sagamihara, Kanagawa
Japan (November 1-2, 2018)(in Japanese).
R. Acquafredda, T. Adam, N. Agafonova, P. Alvarez Sanchez, M. Ambrosio, A. Anokhina, S. Aoki, A. Ariga, T. Ariga, L. Arrabito, C. Aufranc,
D. Autiero, A. Badertscher, A. Bagulya, E. Baussan, A. Bergnoli, F. Bersani Greggio, A. Bertolin, M. Besnier, D. Biare, D. Bick, S. Blin, K. Borer, J. Boucrot, D. Boutigny, V. Boyarkin, C. Bozza, T. Brugiere, R. Brugnera, G. Brunetti, S. Buontempo, J.E. Campagne, B. Carlus, E. Carrara, A.
Cazes, L. Chaussard, M. Chernyavsky, V. Chiarella, N. Chon-Sen, A.
Chukanov, R. Ciesielski, L. Consiglio, M. Cozzi, G. D'Amato, F. Dal
Corso, N. D'Ambrosio, J. Damet, C. de La Taille, G. De Lellis, Y. Declais, T. Descombes, M. De Serio, F. Di Capua, D. Di Ferdinando, A. Di
Giovanni, N. Di Marco, C. Di Troia, N. Dick, S. Dmitrievski, A.
Dominjon, M. Dracos, D. Duchesneau, B. Dulach, S. Dusini, J. Ebert, I.
Efthymiopoulos, O. Egorov, K. Elsener, R. Enikeev, A. Ereditato, L.S.
Esposito, C. Fanin, J. Favier, G. Felici, T. Ferber, R. Fini, L. Fournier, A.
Franceschi, D. Frekers, T. Fukuda, C. Fukushima, V.I. Galkin, V.A.
Galkin, R. Gallet, S. Gardien, A. Garfagnini, G. Gaudiot, G. Giacomelli, M. Giorgini, C. Girerd, C. Gollnitz, T. Goeltzenlichter, J. Goldberg,
D. Golubkov, Y. Gornushkin, J.N. Grapton, G. Grella, F. Grianti, E.
Gschwendtner, C. Guerin, M. Guler, C. Gustavino, J.L. Guyonnet, C.
Hagner, T. Hamane, T. Hara, M. Hauger, M. Hess, M. Hierholzer, K.
Hoshino, M. Ieva, M. Incurvati, K. Jakovcic, J. Janicsko Csathy, B. Janutta, C. Jollet, F. Juget, M. Kazuyama, S.H. Kim, N. Khovansky, M. Kimura, B. Klicek, J. Knusel, K. Kodama, D. Kolev, M. Komatsu, U. Kose, A.
Krasnoperov, I. Kreslo, Z. Krumstein, V.V. Kutsenov, V.A. Kuznetsov, I.
Laktineh, M. Lavy, C. Lazzaro, T.D. Le, T. Le Flour, J. Lenkeit, J. Lewis,
S. Lieunard, A. Ljubicic, A. Longhin, G. Lutter, A. Malgin, K. Manai, G.
Mandrioli, A. Marotta, J. Marteau, G. Martin-Chassard, V. Matveev, N.
Mauri, M. Meddahi, F. Meisel, A. Meregaglia, A. Meschini, M. Messina, P. Migliozzi, P. Monacelli, I. Monteiro, F. Moreau, K. Morishima, U.
Moser, M.T. Muciaccia, P. Mugnier, N. Naganawa, M. Nakamura, T.
Nakano, T. Napolitano, V. Nikitina, K. Niwa, Y. Nonoyama, A. Nozdrin,
S. Ogawa, A. Olchevski, D. Orlandi, G. Orlova, V. Osedlo, D. Ossetski,
M. Paniccia, A. Paoloni, B.D. Park, I.G. Park, A. Pastore, L. Patrizii, L.

Pellegrino, E. Pennacchio, H. Pessard, V. Pilipenko, C. Pistillo, N.
Polukhina, M. Pozzato, K. Pretzl, P. Publichenko, F. Pupilli, L. Raux, J.P.
Repellin, R. Rescigno, D. Rizhikov, T. Roganova, G. Romano, G. Rosa,
I. Rostovtseva, A. Rubbia, A. Russo, V. Ryasny, O. Ryazhskaya, A. Sadovski, C. Sanelli, O. Sato, Y. Sato, V. Saveliev, G. Sazhina, A. Schembri,
W. Schmidt-Parzefall, H. Schroeder, H.U. Schutz, J. Schuler, L. Scotto
Lavina, J. Serrano, H. Shibuya, S. Simone, M. Sioli, C. Sirignano, G.
Sirri, J.S. Song, M. Spinetti, L. Stanco, N. Starkov, M. Stipcevic, T.
Strauss, P. Strolin, V. Sugonyaev, S. Takahashi, V. Talochkin, M. Tenti, V.
Tereschenko, Francesco Terranova, I. Tezuka, V. Tioukov, P. Tolun, V.
Tsarev, R. Tsenov, S. Tufanli, U. Ugolino, N. Ushida, G. Van Beek, V.
Verguilov, T. Viant, P. Vilain, M. Vladimirov, L. Votano, J.L. Vuilleumier,
T. Walchli, M. Weber, G. Wilquet, B. Wonsak, J. Wurtz, V. Yakushev,
C.S. Yoon, Y. Zaitsev, A. Zghiche, R. Zimmermann, J. Instrum., 4,
P04018 (2009).
5) T. Fukuda, Proceedings of Science, The 3rd KMI International Symposium (012), 294, Nagoya University, Nagoya Japan ( January 5-7, 2017).
6) S. Takahashi, S. Aoki, K. Hamada, T. Hara, T. Inoue, K. Ishiguro, A. Iyono, H. Kawahara, K. Kodama, R. Komatani, M. Komatsu, T. Kosaka,
M. Miyanishi, F. Mizutani, K. Morishima, M. Morishita, N. Naganawa,
M. Nakamura, T. Nakano, A. Nishio, K. Niwa, N. Otsuka, K. Ozaki, H.
Rokujo, O. Sato, E. Shibayama, A. Suzuki, R. Tanaka, Y. Tateishi, S.i
Tawa, M. Yabu, K. Yamada, S. Yamamoto, M. Yoshimoto, Adv. SpaceRes., 62, 2945-2953 (2018).
7) S. Takahashi, S. Aoki, K. Hamada, T. Hara, T. Inoue, K. Ishiguro, A. Iyono, H. Kawahara, K. Kodama, R. Komatani, M. Komatsu, T. Kosaka,
M. Miyanishi, F. Mizutani, K. Morishima, M. Morishita, N. Naganawa,
M. Nakamura, T. Nakano, A. Nishio, K. Niwa, N. Otsuka, K. Ozaki, H.
Rokujo, O. Sato, E. Shibayama, A. Suzuki, R. Tanaka, Y. Tateishi, S.
Tawa, M. Yabu, K. Yamada, S. Yamamoto, M. Yoshimoto, Prog. Theor.
Exp. Phys., 2016, 073F01 (2016).
8) K. Morishima, M. Kuno, A. Nishio, N. Kitagawa, Y. Manabe, M. Moto,
F. Takasaki, H. Fujii, K. Satoh, H. Kodama, K. Hayashi, S. Odaka, S.
Procureur, D. Attié, S. Bouteille, D. Calvet, C. Filosa, P. Magnier, I.
Mandjavidze, M. Riallot, B. Marini, P. Gable, Y. Date, M. Sugiura, Y.
Elshayeb, T. Elnady, M. Ezzy, E. Guerriero, V. Steiger, N. Serikoff, J.
Mouret, B. Charlès, H. Helal, M. Tayoubi, Nature, 552, 386-390, (2017).
9) D. M. Siegel, B. D. Metzger, Phys. Rev. Lett., 119, 231102-1 - 231102-7(2017).
10) K. Kuge, K. Yabe, N. Aoki, A. Hasegawa, N. Mii, T. Habu, J. Soc. Photogr. Sci. Tech. Jpn., 63, 63-67 (2000)(in Japanese).
11) C. F. Powell, P. H. Fowler, D. H. Perkins, “The Study of Elementary
Particles by the Photographic Method", PERGAMON PRESS, 100112 (1959).
12) K. Kuwabara, S. Nishiyama, FUJIFILM Research & Development, 48,
82-86 (2003).
13) N. Yasuda, S. Kodaira, M. Kurano, H. Kawashima, H. Tawara, T. Doke,
K. Ogura, N. Hasebe, J. Phys. Soc. Jpn., 78, 142-145 (2009).
14) W. R. Leo, “Techniques for Nuclear and Particle Physics Experiments",
Second Revised Edition, Springer-Verlag, 24-27 (1994)
15) A. Iyono, S. Aoki, T. Hara, K. Kuretsubo, H. Matsumoto, F. Mizutani, K.
Ozaki, E. Shibayama, A. Suzuki, S. Takahashi, Y. Tateishi, M. Yabu, K.
Yamada, K. Kodama, K. Hamada, H. Kawahara, R. Komatani, M.
Komatsu, M. Miyashita, M. Morishita, K. Morishima, M. Nakamura, N.
Naganawa, T. Nakano, A. Nishio, K. Niwa, N. Otsuka, H. Rokujo, O.
Sato, M. Yoshimoto, S. Yamamoto, Proceedings of Science, 35th International Cosmic Ray Conference (171), 301, 171, Busan Korea ( July
12-20, 2017).
16) K. Kuge, K. Hayashi, Y. Endo, N. Yasuda, C. Fukushima, M. Kimura, H.
Shibuya, A. Hasegawa, H. Kumagai, S. Kodaira, S. Ota, J. Soc. Photogr.
Sci. Tech. Jpn., 72, 209-213 (2009).