7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Calibration of a Heavy Ion Beam Probe on the PLATO tokamak.

T. Suetsugu1, T. Ido1,2, A. Fujisawa1,2, T. Nishizawa1,2, D. Kobayashi1, D. Nishimura1, C. Moon1,2,
Y. Nagashima1,2, N. Kasuya1,2, Y. Kosuga1,2, T. Yamada3
1

Interdisciplinary Graduate School of Engineering Sciences, 2 Research Institute for Applied
Mechanics, 3 Faculty of Arts and Science, Kyushu University
e-mail (speaker): t.suetsugu@triam.ksyuhsu-u.ac.jp

A Heavy Ion Beam Probe (HIBP) is a powerful plasma
diagnostic instrument in transport research because it canmeasure the electric potential, its fluctuation, and density
fluctuation, simultaneously[1]. The PLATO tokamak[2],which aims to elucidate plasma turbulence transportphenomena, is equipped with a HIBP as one of main
diagnostic tools[3]. Currently, the installation of the HIBP
has been completed. Calibration experiments are in
progress to evaluate the installation accuracy of theinjection and detection beamlines.
The accuracy of the injection beamline installation isevaluated by detecting the injected beam by a detector
installed at the bottom of the detection port. The injectedbeam trajectory is determined by the ion species, toroidal
magnetic field, beam energy, and injection angle. Theinjection angle is determined by the voltage applied in theelectrostatic deflector (PS1 in Fig. 1). Since the injectedbeam is a singly charged positive ion, it is bent by thetoroidal magnetic field. The PS1 voltage required to bedetected by the injected beam detector was determined by
the beam trajectory calculation as shown in Fig. 2. ThisPS1 voltage is compared with the PS1 voltage at which
the injected beam can be detected by the injected beam
detector in the calibration experiment. The installation
accuracy of the injection beamline can be estimated by thedifferences in the PS1 voltages between the trajectory
calculation and the experiment.

The installation accuracy of the detection beamline
can be estimated by utilizing the fact that the energy
analyzer with parallel electrodes has a quadratic
convergence characteristic with respect to the incident
angle of the detected beam to the energy analyzer when
the incident angle is near 30°[4]. In the calibration
experiment using the detected beam, the detected beam isgenerated by collisional ionization with neutral gas so thatno electric potential distribution is generated in thevacuum vessel. The installation accuracy of the detection
beam line is evaluated by checking whether the detectedbeam enters the energy analyzer at the angle predicted by
the trajectory calculation. In addition, it is also important
to demonstrate that two energy analyzers work
simultaneously. The results of these ongoing calibration
experiments will be reported.
This work was supported by Grant-in-Aid for
Promoted Research 17H06089 and LHD Project Joint
Research NIFS21KOCH004.
References[1] T. P. Crowley, IEE Transactions on Plasma Science(Volume: 22, Issue: 4, August 1994) pp 291-309[2] A. Fujisawa, AIP Conf. Proc. 1993, 02001(2018)[3] T. Ido et al., Rev Sci. Instrum. 92, 053553(2021)[4] T.S. Green et al., Rev. Sci. Instrum. 41. 1409(1970)

Figure 2. Beam arrival position on the surface of the injectedbeam detector and dR’ is distance between the arrival positionand center of the detector. The ion specie is Cs, the toroidal
Figure 1. Poloidal cross section of a HIBP on the PLATO

magnetic field strength is 0.3T, and the beam energy is 20keV.

tokamak. The red line is an injected beam. The blue lines are

The Vps1 is voltage in the PS1.

detection beams.