Development of over-MW gyrotrons for fusion at 14 GHz to sub-THz frequencies

Kariya, T.; Imai, T.; Minami, R.; Sakamoto, K.; Oda, Y.; Ikeda, Ryosuke; Shimozuma, Τ.; Kubo, S.; Idei, H.; Numakura, T.; Tsumura, Kohei; Ebashi, Y.; Okada, Maki; Nakashima, Y.; Yoshimura, Y.; Takahashi, H.; Ito, Satoshi; Hanada, K.; Nagasaki, K.; Ono, M.; Eguchi, Takanori; Mitsunaka, Y.

doi:10.1088/1741-4326/aa6875

Cited by 29 publications

(19 citation statements)

References 17 publications

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“…By decreasing the magnetic field, oscillation of lower frequencies around 240 GHz was demonstrated by scanning the cavity magnetic field. Up to now, 345 kW was obtained at 243.9 GHz (TE28,14) [79].…”

Section: Japanese Developments For Future Demo Gyrotronsmentioning

confidence: 96%

High-power gyrotrons for electron cyclotron heating and current drive

Thumm¹,

Денисов²,

Sakamoto³

et al. 2019

Nucl. Fusion

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127

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In many tokamak and stellarator experiments around the globe that are investigating energy production via controlled thermonuclear fusion, electron cyclotron heating and current drive (ECH&CD) are used for plasma start-up, heating, non-inductive current drive and MHD stability control. ECH will be the first auxiliary heating method used on ITER. Megawatt-class, continuous wave (CW) gyrotrons are employed as high-power millimeter (mm)-wave sources. The present review reports on the worldwide state-of-the-art of high-power gyrotrons. Their successful development during the past years changed ECH from a minor to a major heating method. After a general introduction of the various functions of ECH&CD in fusion physics, especially for ITER, Section 2 will explain the fast-wave gyrotron interaction principle. Section 3 discusses innovations on the components of modern long-pulse fusion gyrotrons (magnetron injection electron gun (MIG), beam tunnel, cavity, quasi-optical output coupler, synthetic diamond output window, single-stage depressed collector) and auxiliary components (superconducting magnets, gyrotron diagnostics, high-power calorimetric dummy loads). Section 4 deals with present megawatt-class gyrotrons for ITER, W7-X, LHD, EAST, KSTAR and JT-60SA, and also includes tubes for moderate pulse length machines as, ASDEX-U, DIII-D, HL-2A, TCV, QUEST and GAMMA-10. In Section 5 the development of future advanced fusion gyrotrons is discussed. These are tubes with higher frequencies for DEMO, multi-frequency (multi-purpose) gyrotrons, stepwise frequency tunable tubes for plasma stabilization, injection-locked and coaxial-cavity multi-megawatt gyrotrons, as well as sub-THz gyrotrons for collective Thomson scattering (CTS). Efficiency enhancement via multi-stage depressed collectors, fast oscillation recovery methods and reliability, availability, maintainability and inspectability (RAMI) will be discussed at the end of this section.

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Section: Japanese Developments For Future Demo Gyrotronsmentioning

confidence: 96%

High-power gyrotrons for electron cyclotron heating and current drive

Thumm¹,

Денисов²,

Sakamoto³

et al. 2019

Nucl. Fusion

Self Cite

127

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“…This result will be important in future gyrotrons with higher operating frequency (such as 154 GHz) and output power, which will require a high beam current. We will continue our attempts to develop gyrotrons that can operate over a wide frequency range (14 -300 GHz) for present and future devices up to Demonstration Power Station (DEMO), the next-generation nuclear fusion power plant [3,13,14].…”

Section: Effect Of the Beam Fluctuation On The Outputmentioning

confidence: 99%

“…For these purposes, the gyrotrons must operate in the quasi-continuous regime at frequencies of 10 -300 GHz and output powers of 1 MW or higher. Recently, many studies [1][2][3] have been devoted to high-power and longpulse gyrotrons, and multi-frequency gyrotrons are required for experimental flexibility and research collaboration efforts.…”

Section: Introductionmentioning

confidence: 99%

Code Development for Calculating Electron Beams in the Cavities of the Future High-Power Gyrotrons

Numakura

Kariya

Minami

et al. 2019

Plasma and Fusion Research

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This study develops a computational code for evaluating the operations of high-power gyrotrons with highcurrent electron beams. The analytical model describes the electromagnetic fields and electrons by the Maxwell equations and cold-fluid equations, respectively. Specifically, it estimates the output power of the gyrotron with electron-beam fluctuations, which occur under high beam currents. The effects of fluctuations of the intense electron flows in nonuniform magnetic fields are studied in a 1 MW gyrotron for electron cyclotron resonance plasma heating and current drive in large devices, such as the tandem mirror plasma device GAMMA10/PDX and the Large Helical Device (LHD). The rate of fluctuation growth of the electron beam and the output power of the high-power gyrotron with a fluctuated beam are calculated. In gyrotrons with a higher operating frequency (e.g., 154 GHz), significant deterioration of the electron beam and gyrotron operation is expected at beam currents exceeding 120 A.

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“…GAMMA 10/PDX project primarily focuses on developing a highpower 28 GHz gyrotron. In the 28 GHz gyrotron project, a power output of over 1.5 MW has been achieved in the short pulse test, which is a new record in this frequency range [2].…”

Section: Introductionmentioning

confidence: 99%

Generation and Measurement of High Intermittent Heat Flux in GAMMA 10/PDX

Minami

Kariya

Imai

et al. 2019

Plasma and Fusion Research

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Electron cyclotron heating (ECH) power modulation experiments have been conducted for GAMMA 10/PDX to generate and control the high heat flux and to develop an edge localized mode (ELM)-like intermittent heat load pattern for divertor simulation studies. Flux and energy spectra of end-loss electrons are measured using a multi-grid energy analyzer (loss electron diagnostics, LED). ECH-induced potential formation at plug regions (P-ECH) produces high-energy electron flows along the magnetic lines of force. The power scaling of electron flux in GAMMA 10/PDX indicates that higher ECH power generates higher electron flux. In this study, a new mirror antenna is developed to generate higher heat flux and concentrate the heating power on the axis. The energy density and heat flux obtained using previous systems are 0.06 MJ/m 2 and 11.4 MW/m 2 , respectively, and those obtained using the new mirror systems are 0.09 MJ/m 2 and 30 MW/m 2 , respectively. These values are still considerably lower than those of ITER ELM (mitigated ELMs in ITER is ∼0.5 MJ/m 2 for t = 0.5 ms).

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Development of over-MW gyrotrons for fusion at 14 GHz to sub-THz frequencies

Cited by 29 publications

References 17 publications

High-power gyrotrons for electron cyclotron heating and current drive

High-power gyrotrons for electron cyclotron heating and current drive

Code Development for Calculating Electron Beams in the Cavities of the Future High-Power Gyrotrons

Generation and Measurement of High Intermittent Heat Flux in GAMMA 10/PDX

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