Extension of Operational Regimes with ICRF Heating on GAMMA 10/PDX

Ikezoe, Ryuya; Ichimura, M.; Hirata, M.; Yokoyama, T.; Iwamoto, Yosuke; Okada, T.; Sumida, S.; Takeyama, K.; Jang, S.; Oi, Timchenko; Ichimura, Kazuya; Nakashima, Y.

doi:10.13182/fst14-853

Cited by 10 publications

(12 citation statements)

References 16 publications

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“…Double arc type (DAT) antennas for ICRF are installed in both east and west anchor regions and used to heat the plasma in anchor cells. In a series of GAMMA 10/PDX experiments, it was found that adding a plasma heating wave by DAT antenna into an anchor region shows the remarkable effect of increasing the end-loss ion flux [2][3][4]. Then, in this series, simultaneous heating by both east and west anchor DAT antennas has been performed.…”

Section: Methodsmentioning

confidence: 99%

“…In previous research, the energy distribution and the current density of the end- loss ion were measured by the end-loss ion energy analyzer (ELIEA) and the particle flux estimated from measured ion current density is 5 × 10 22 particles/m 2 sec. In order to increase the amount of particle flux to the value expected in ITER or other fusion device; 10 23 ∼10 24 particles/m 2 sec, new antennas of ICRF have been installed and in recent experiments, large increase of plasma density and end-loss particle flux due to the new ICRF heating method were observed [4]. In this article, results of the high-density experiments with new ICRF antenna configurations are reported and discussions on the characteristics of mirror confinement in the newly achieved high-density operations of the tandem mirror are made.…”

Section: Introductionmentioning

confidence: 99%

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Study of the Axial Ion Confinement Time for High Particle Flux Operations of GAMMA 10/PDX

Ichimura

Nakashima

Islam

et al. 2016

Plasma and Fusion Research

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Characteristics of axial plasma confinement in recent high-density mode of GAMMA 10/PDX tandem mirror is reported in this paper. The parameter of the end-loss ion flux is an important issue in the divertor simulation studies in GAMMA 10/PDX. With an ICRF heating in the anchor-cells of the machine, large increase in the electron line-density in the central-cell (NLCC) and the end-loss particle flux were observed. The behavior of the electron line density, plasma temperature and the amount of end-loss ion flux during the experiments suggested that the mechanism of the axial ion loss was changed due to the increase of ion collision frequency. In contrast with the standard operations of GAMMA 10/PDX, plasma parameters in recent high-density operations stays in the range of high collision frequency. In such collisional plasma, the end-loss ion particle flux show linear dependence on the plasma density instead of the parabolic dependence expected in plasmas of low collisionfrequency. In the high collision frequency plasma, it is notable that plasma potential φ largely changes the dependence of the particle flux on the plasma density.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Study of the Axial Ion Confinement Time for High Particle Flux Operations of GAMMA 10/PDX

Ichimura

Nakashima

Islam

et al. 2016

Plasma and Fusion Research

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“…This study has been carried out in GAMMA 10/PDX [1][2][3], which is a minimum-B anchored tandem mirror with outboard axisymmetric plug/barrier cells. The central cell has a length of 5.6 m and the magnetic field intensity at the midplane is 0.4 T with a mirror ratio of 5.…”

Section: Gamma 10/pdx and Icrf Heating Systemsmentioning

confidence: 99%

“…High particle and heat fluxes in the end region along the magnetic field line are required. To control the end loss ions, the ion-cyclotron range of frequency (ICRF) antennas in the central cell, the anchor cells, and the west plug/barrier cells have been used in several combinations [2].…”

Section: Introductionmentioning

confidence: 99%

Investigation of ICRF Heating Effect in Anchor Region on GAMMA 10/PDX

Hirata

Itagaki

Ikezoe

et al. 2019

Plasma and Fusion Research

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To investigate end-loss plasma control, several heating operations were carried out using ion-cyclotron range of frequency (ICRF) heating systems in GAMMA 10/PDX. In anchor region, one of the important heating positions to control the end loss particle and heat fluxes, excited ICRF waves are measured as the density fluctuations using an upgraded reflectometer system and the detailed radial profiles are observed. The efficiency of anchor heating was changed using the phase control between two antennas installed in the anchor and/or the central region. The interference of two waves during a phase-control ICRF heating has been directly measured inside the plasma. In addition, several phase dependencies were observed using absorption methods with photodiode in anchor region.

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“…Representative examples of these waves include the ion-cyclotron range of frequencies (ICRF) waves that are used for plasma production and ion heating in the GAMMA 10 tandem mirror device, 1,2 and also the Alfvén-ion-cyclotron (AIC) waves [3][4][5][6] that are spontaneously excited by strong anisotropy in the ion temperature. AIC waves have several discrete peaks in the unstable frequency range that occur just below the ion cyclotron frequency near the midplane of the GAMMA 10 central cell.…”

Section: Introductionmentioning

confidence: 99%

Multi-point measurement using two-channel reflectometer with antenna switching for study of high-frequency fluctuations in GAMMA 10

Ikezoe

Ichimura

Okada

et al. 2017

Review of Scientific Instruments

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A two-channel microwave reflectometer system with fast microwave antenna switching capability was developed and applied to the GAMMA 10 tandem mirror device to study high-frequency small-amplitude fluctuations in a hot mirror plasma. The fast switching of the antennas is controlled using PIN diode switches, which offers the significant advantage of reducing the number of high-cost microwave components and digitizers with high bandwidths and large memory that are required to measure the spatiotemporal behavior of the high-frequency fluctuations. The use of two channels rather than one adds the important function of a simultaneous two-point measurement in either the radial direction or the direction of the antenna array to measure the phase profile of the fluctuations along with the normal amplitude profile. The density fluctuations measured using this system clearly showed the high-frequency coherent fluctuations that are associated with Alfvén-ion-cyclotron (AIC) waves in GAMMA 10. A correlation analysis applied to simultaneously measured density fluctuations showed that the phase component that was included in a reflected microwave provided both high coherence and a clear phase difference for the AIC waves, while the amplitude component showed neither significant coherence nor clear phase difference. The axial phase differences of the AIC waves measured inside the hot plasma confirmed the formation of a standing wave structure. The axial variation of the radial profiles was evaluated and a clear difference was found among the AIC waves for the first time, which would be a key to clarify the unknown boundary conditions of the AIC waves.

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Extension of Operational Regimes with ICRF Heating on GAMMA 10/PDX

Cited by 10 publications

References 16 publications

Study of the Axial Ion Confinement Time for High Particle Flux Operations of GAMMA 10/PDX

Study of the Axial Ion Confinement Time for High Particle Flux Operations of GAMMA 10/PDX

Investigation of ICRF Heating Effect in Anchor Region on GAMMA 10/PDX

Multi-point measurement using two-channel reflectometer with antenna switching for study of high-frequency fluctuations in GAMMA 10

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