Effects of the radial electric field on the confinement of fast ions in ITER

Tani, Keiji*; Honda, Mitsuru; Oikawa, Toshihiro*; Shinohara, Koji; Kusama, Yoshinori; Sugie, Tatsuo

Nuclear Fusion, 55(5), p.053010_1 - 053010_15, 2015/05

AA2014-0355.pdf:2.0MB

https://doi.org/10.1088/0029-5515/55/5/053010

The effects of a radial electric field (EF) on the losses of alpha particles and NBI fast ions in typical ITER operation scenarios for both error fields due to test blanket modules (TBMs) and toroidal field (TF) ripple were evaluated using an iterative method to execute an orbit-following Monte-Carlo code and a one-dimensional transport code. The EF effect on the loss of fast ions strongly depends on the operation scenario as well as on the error field. The electric field is very significant in the loss of fast ions in a 9MA ITER operation scenario with a higher safety factor and in the error field associated with TBMs. The EF effect in the error field of TF-ripple is very small in any operation scenario. The radial electric field changes the toroidal precession of fast ions and consequently alter their condition of resonance with the error field, which may account for the EF effect on the loss of fast ions in ITER with TBMs.

Identification of high energy ions using backscattered particles in laser-driven ion acceleration with cluster-gas targets

Fukuda, Yuji; Sakaki, Hironao; Kanasaki, Masato; Yogo, Akifumi; Jinno, Satoshi; Tampo, Motonobu; Faenov, A. Ya.*; Pikuz, T.; Hayashi, Yukio; Kando, Masaki; et al.

Radiation Measurements, 50, p.92 - 96, 2013/03

https://doi.org/10.1016/j.radmeas.2012.10.010

A new diagnosis method for high energy ions utilizing a single CR-39 detector mounted on plastic plates is demonstrated to identify the presence of the high energy component beyond the CR-39's detection threshold limit. On irradiation with a 25 MeV per nucleon He ion beam from conventional rf-accelerators, a large number of etch pits having elliptical opening shapes are observed on the rear surface. Detailed investigations reveal that these etch pits are created by heavy ions inelastically backscattered from the plastic plates. This ion detection method is applied to laser-driven ion acceleration experiments using cluster-gas targets, and acceleration of ions with energies up to 50 MeV per nucleon are identified.

A Diagnosis of intense ion beam by CR-39 detectors analyzing the back scattered particles

Kanasaki, Masato; Yamauchi, Tomoya*; Fukuda, Yuji; Sakaki, Hironao; Hori, Toshihiko*; Tampo, Motonobu; Kurashima, Satoshi; Kamiya, Tomihiro; Oda, Keiji*; Kondo, Kiminori

AIP Conference Proceedings 1465, p.142 - 147, 2012/07

https://doi.org/10.1063/1.4737553

A new diagnosis method has been developed utilizing back scattered particles for high energy intense ion beams. The CR-39 detector mounted on the uniform back-scatterer was irradiated with He ions with an energy 25 MeV/n, which is never recorded as etchable track in CR-39. We found that it is possible to diagnose the high energy intense ion beams by analyzing the etch pits created on the rear surface of CR-39 that directly contacted on the back-scatterers. It turns out that most of etch pits in the rear surface are made by the backscattered particles through the investigation of the growth pattern of each etch pit with multi-step etching technique. This method allows simple diagnosis of the ion beam profile and the presence of high energy component of ions beyond the detection threshold limit of the CR-39 in mixed radiation fields such as laser-driven ion acceleration experiments.

Application of CR-39 solid state nuclear track detector to ion beam diagnosis

Kanasaki, Masato; Fukuda, Yuji; Sakaki, Hironao; Nishiuchi, Mamiko; Kondo, Kiminori; Kurashima, Satoshi; Kamiya, Tomihiro; Hattori, Atsuto*; Oda, Keiji*; Yamauchi, Tomoya*

Purazuma, Kaku Yugo Gakkai-Shi, 88(5), p.261 - 275, 2012/05

https://cir.nii.ac.jp/crid/1571698602857969152

CR-39 solid state nuclear track detector, which was developed for optical lens, has been applied for various field such as radon surveys, measurement of galactic cosmic ray, cell irradiation experiment and so on. The CR-39 detectors have the great advantages of being insensitive to high energy photons and electrons and capable of detecting only ions in the mixed fields such as laser driven relativistic plasmas. Though there are some analytical methods of CR-39 to diagnose ion beam, unfortunately, only few researchers in the field of plasma know the methods. This article looks at how to use CR-39 detectors and introduce the accomplishment of the joint study JAEA and Kobe Univ. for application of CR-39 detectors to ion beam diagnosis.

Effects of complex symmetry-breakings on alpha particle power loads on first wall structures and equilibrium in ITER

Shinohara, Koji; Kurki-Suonio, T.*; Spong, D. A.*; Asunta, O.*; Tani, Keiji*; Strumberger, E.*; Briguglio, S.*; Koskela, T.*; Vlad, G.*; Gnter, S.*; et al.

Nuclear Fusion, 51(6), p.063028_1 - 063028_12, 2011/06

https://doi.org/10.1088/0029-5515/51/6/063028

Ripple loss of alpha particles in a low-aspect ratio tokamak reactor

Tani, Keiji*; Nishio, Satoshi; Tobita, Kenji; Tsutsui, Hiroaki*; Mimata, Hideyuki*; Iio, Shunji*; Aoki, Takayuki*

Denki Gakkai Rombunshi, A, 129(9), p.569 - 574, 2009/09

https://doi.org/10.1541/ieejfms.129.569

Studies on the loss of fusion produced alpha particles enhanced by toroidal field (TF) ripple in a low-aspect-ratio tokamak reactor (VECTOR) have been made by using an orbit-following Monte-Carlo code. In actual TF coil systems, the ripple loss of alpha particles is strongly reduced as the aspect ratio becomes low (the power loss is proportional to A for A more than 2.5) and the reduction of the number of TF coils results in a large amount of ripple losses even in a low-aspect-ratio tokamak.

Simulation studies on alpha-particle-driven current in tokamak reactors

Tani, Keiji; Azumi, Masafumi*

Nuclear Fusion, 48(8), p.085001_1 - 085001_9, 2008/08

https://doi.org/10.1088/0029-5515/48/8/085001

Simulation studies are made for alpha-driven currents in tokamak reactors by using an orbit-following Monte-Carlo code. The finite banana width of alpha particles causes an asymmetry particle trapping and consequently an alpha current is driven by the imbalance of transit particles. The current driven by alpha transit particles (simply referred to as transit current) is greatly enhanced by a collaborative effect of the finite banana-width trajectories and a non-uniformity of alpha particle source. The pitch-angle scattering is also very important for the transit current. Fusion produced alpha particles can drive substantial current to assist the bulk bootstrap current in steady state tokamak reactors.

Confinement of alpha particles in a low-aspect-ratio tokamak reactor

Tani, Keiji; Tobita, Kenji; Iio, Shunji*; Tsutsui, Hiroaki*; Nishio, Satoshi; Aoki, Takayuki*

Denki Gakkai Rombunshi, A, 125(11), p.938 - 942, 2005/11

https://doi.org/10.1541/ieejfms.125.938

Studies on the loss of fusion produced alpha particles enhanced by toroidal field (TF) ripple in a low-aspect-ratio tokamak reactor (VECTOR) have been made by using an orbit-following Monte-Carlo code. The ripple loss is strongly reduced as the aspect ratio becomes low. Consequently, alpha particles are well confined in VECTOR. Thanks to the good confinement of alphas in a low-aspect-ratio system, the number of TF coils can be reduced to about 6, one half of the original VECTOR, by installing cooling systems near the outer edge of plasma and making allowances for about 30% increase in the bore diameter of TF coils.

On the confinement of alpha particles in a low-aspect-ratio tokamak reactor

Tani, Keiji; Tobita, Kenji; Nishio, Satoshi; Iio, Shunji*; Tsutsui, Hiroaki*; Aoki, Takayuki*

Denki Gakkai Purazuma Kenkyukai Shiryo (PST-03-39), p.13 - 18, 2003/09

Studies were made on ripple losses of fusion produced alpha particles in a tokamak reactor with a non-circular plasma cross-section by using an orbit-following Monte-Carlo code. A preliminary estimation of ripple loss of alpha particles in VECTOR, a compact tokamak type fusion reactor, with a negative magnetic shear was also made

Construction and commissioning of a 215-m-long beamline at SPring-8

Goto, Shunji*; Takeshita, Kunikazu*; Suzuki, Yoshio*; Ohashi, Haruhiko*; Asano, Yoshihiro; Kimura, Hiroaki*; Matsushita, Tomohiro*; Yagi, Naoto*; Isshiki, M.*; Yamazaki, H.*; et al.

Nuclear Instruments and Methods in Physics Research A, 467-468(Part1), p.682 - 685, 2001/07

https://doi.org/10.1016/S0168-9002(01)00445-4

no abstracts in English