Ⅲ-4. Radiation Chemistry & Biology

RIKEN Accel. Prog. Rep. 51 (2018)

Current status of development of ion microbeam device
with tapered glass capillary for biological use
T. Ikeda,∗1 M. Hamagaki,∗1 K. Sato,∗1,∗2 K. Hirose,∗1,∗2 M. Miwa,∗1,∗2 H. Sato,∗1 and T. Abe∗1
A microbeam irradiation system based on single tapered glass capillary optics with thin end-window has
been developed at a beam line of the Pelletron tandem accelerator in the Nishina R&D Building. Themicrobeam is extracted through a several-µm diameteroutlet. The previous system (FY2006-2015) was used toinvestigate only the cellular response to ion microbeam
hitting.1–4) The new system will irradiate samples of not
only (1) cells (transparent target), but also (2) the surfaces of small insects (not transparent). The corresponding aims are (1) investigation of the mechanism of repairof DNA by microbeam irradiation to a small area in thenucleus to artiﬁcially induce accumulation of proteinsfor the repairing, and (2) search for a speciﬁc gene that
corresponds to an active organ (horn, wing etc.) to develop its structure or shape. The system will employ H+
ions of up to 3 MeV and He2+ ions of up to 4.5 MeV,
whose ranges after the end-window are approximately
130 µm and 20 µm in water, respectively. For the irradiation of cells, the ion energy is selected such that theion can be stopped inside the nucleus or can penetrate
the cell. For the irradiation of an insect that is alive in
air, the distance from the capillary outlet is several mmfor both H+ and He2+ beams, since air is about 1000
times thinner than water. One can select the ion species
according to their linear energy transfer (LET) of up
to about 80 and 230 keV/µm for H+ and He2+ in thetarget, respectively. This means that single ion hitting
can cause a serious damage in the DNA. This year, thefollowing parts were installed or are in progress:(a) Laser alignment system for capillary axis: a green(wavelength = 532 nm, 1 mW max. for output) laser
source is positioned at the counter part of the capillary
beam line on the analyzing magnet so that the ion beamaxis can be visualized as the laser beam. The laser istransmitted through the capillary optics. The systemallows users to reduce the alignment time from a few
hours to a few minutes. The inset photo in Fig. 1 shows a
diﬀraction ring pattern that is obtained when a capillary
is aligned precisely. The capillary is seen at the bottom
left part as a shining cone by the green laser.
(b) Prototype of vertically bending magnet of MeV ion
beams using neodymium magnets located in the vacuum
chamber: the magnetic ﬁeld in the gap was measured
to be 6.4 kGauss. The gap will be tuned so that theoptimum bending angle of the ion beam will be obtained.
(c) Capillary holder with a remote-control tilt system (Fig. 2): the actuators (SGSP-13ACTR-B0, SIGMAKOKI Co., LTD) for the horizontal and vertical tilting are controlled by Windows Tablet PCs through Eth∗1∗2

RIKEN Nishina Center
Department of Physics, Toho University

Fig. 1. The beam line of the new microbeam system. Thesymbols (a)–(e) are explained in the text. The degree ofvacuum level is kept better than 10−5 Pa.

Fig. 2. Capillary holder with a remote tilt system controlled
through Ethernet. The glass tube will be replaced witha tapered glass capillary optics to produce microbeams.

ernet.
(d) Ion counting system to estimate the dose for theirradiation: PIN photodiode sensor (S3590-09, Hamamatsu) is connected to a charge-sensitive pre-ampliﬁer
whose output signals are processed by NIM modules.
(e) An inverted microscope (IX73, OLYMPUS) anda motorized XY stage system (BIOS-225T-OL, SIGMAKOKI Co., LTD) were purchased. The working distances of the stage are 110 and 75 mm for the X (leftright) and Y directions, respectively, with a position resolution of 0.1 µm.
The next step is the irradiation to biological target for
the aims mentioned in the introduction section.
References
1) Y. Iwai et al., Appl. Phys. Lett. 92, 023509 (2008).
2) M. Kato et al., Appl. Phys. Lett. 100, 193702 (2012).
3) V. Mackel et al., Rev. Sci. Instrum. 85, 014302 (2014).
4) T. Ikeda et al., RIKEN Accel. Prog. Rep. 48, 315 (2015).

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