165-GHz Coaxial Cavity Gyrotron

Piosczyk, B.; Dammertz, G.; Dumbrājs, O.; Kartikeyan, M. V.; Thumm, M.; Yang, Xiaoxia

doi:10.1109/tps.2004.827593

Cited by 61 publications

(25 citation statements)

References 11 publications

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“…They do not influence results and can not be the reasons for the discrepancy between the theoretical predictions and the experimental measurements of the ohmic losses in the inner conductor revealed in [16] for the T E 31,17 coaxial gyrotron cavity.…”

Section: Resultsmentioning

confidence: 82%

“…The radius of the corrugated inner conductor should be chosen very carefully in order to keep the ohmic losses below a certain upper limit on one hand, and to suppress possible mode competition on the other. A comparison between the theoretical calculations and experimental results for the T E 31,17 coaxial gyrotron cavity [16] showed that the experimentally measured losses almost twice exceeded the theoretical predictions that were based on the SIM. So, compared to the rigorous full wave calculations, the measured losses are three to four times larger.…”

Section: Introductionmentioning

confidence: 81%

“…The reasons for such a discrepancy are still unclear. However, it should be pointed that experiments [16] suffered from uncertainties caused by the short pulse lengths, the limited accuracy of the calorimetric measurements, and the influence of other heat sources, in particular, the dissipation of the captured stray radiation at the insert. Nevertheless, one of the possible reasons can be associated with the idealizations of the corrugation geometry that were assumed in the rigorous full wave approaches [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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Electromagnetic Analysis of Coaxial Gyrotron Cavity With the Inner Conductor Having Corrugations of an Arbitrary Shape

Zaginaylov¹,

Mitina²

2011

PIER B

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Abstract-The mathematical approach for the calculation of the membrane functions of a coaxial gyrotron cavity with an arbitrary corrugated inner rod is proposed. It is utilized mainly for two aims. First, it is shown that for typical parameters of the coaxial gyrotron cavity with the corrugated inner conductor the shape of corrugations only slightly influences the eigenvalues of competing eigen-modes. However, it can significantly influence the density of ohmic losses in the inner conductor. In particular, it is shown that the density of ohmic losses can be reduced almost twice by the proper choice of the corrugation shape. Second, it is shown that the usual idealizations of the corrugated surface of the inner conductor (the surface with rectangular grooves, having rounded edges, is approximated by a surface with wedged groves that have sharp edges) are correct. The physical interpretation of the obtained results and their practical meaning are discussed.

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Section: Resultsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Electromagnetic Analysis of Coaxial Gyrotron Cavity With the Inner Conductor Having Corrugations of an Arbitrary Shape

Zaginaylov¹,

Mitina²

2011

PIER B

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“…The coaxial-cavity gyrotron is a promising technology for future multi-MW fusion gyrotrons [2]. In [3] a world record RF output power of 2.2 MW at short pulses (ms-range) was demonstrated.…”

Section: Verification Of the Coaxial-cavity Technologymentioning

confidence: 99%

European research activities towards a future DEMO gyrotron

et al. 2017

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Coordinated by the EUROfusion Consortium, several European research institutes are working on fusion technologies towards options for a European DEMOnstration Fusion Power Plant (FPP), as a single step between ITER and a commercial FPP, to deliver net electricity by mid of this century. One of the focus areas is the research on a proper Electron Cyclotron Resonance Heating (ECRH) and Current Drive (ECCD) system for which the fusion gyrotron is one of its major key components [1].A future FPP will probably require an ECCD operating frequency ranging from 170 GHz up to 240 GHz depending on the DEMO baseline. An RF output power of significantly higher than 1 MW (target: 2 MW) and a total gyrotron efficiency better than 60% are required. Multi-purpose operation at multiples of the λ/2-resonance frequency of the vacuum window of the gyrotron, hence in leaps of about 30 GHz (e. g. 170 / 204 / 238 GHz) needs to be considered for plasma start-up, heating and current drive. Optionally for possible steering of the absorption layer the gyrotron shall allow a fast frequency tuning in steps of around 2-3 GHz. The R&D work within the EUROfusion work package "WP HCD EC Gyrotron R&D and Advanced Developments (AD)" is focusing on all of the named targets. Verification of the coaxial-cavity technologyThe coaxial-cavity gyrotron is a promising technology for future multi-MW fusion gyrotrons [2]. In [3] a world record RF output power of 2.2 MW at short pulses (ms-range) was demonstrated. Nevertheless, the 2 MW coaxial-cavity technology, already considered for the first installation in ITER earlier [4], is still lacking its proofof-concept regarding long-pulse operation. Major concerns are the proper alignment and thermal loading of the cavity wall and its inner conductor as well as the thermal loading of the collector. Its feasibility shall be finally demonstrated by upgrading the existing KIT 2 MW 170 GHz short-pulse pre-prototype to pulse lengths up to 1 s [5]. In parallel, work is ongoing in the field of advanced cooling concepts [6,7]. Additionally, two new coaxial-cavity Magnetron Injection Guns (MIGs) are under manufacturing. The first is employing an advanced emitter technology whose major element is a new nonemissive coating. That will significantly reduce the velocity spread of the electrons at the emitter [8]. Secondly, a newly designed Inverse Magnetron Injection Gun (IMIG) will allow for a significant larger emitter radius and therefore increased output power at operating frequencies significantly above 200 GHz by keeping the same or even smaller size of the bore hole of the gyrotron SC magnet [9]. Studies towards a 240 GHz gyrotronA frequency up to 240 GHz was selected for the theoretical research work towards a future FPP, considering the requirements for "multi-purpose" and "fast frequency step-tunable" operation at high-field tokamaks and for a wide range of RF beam steering. The coaxialcavity gyrotron technology, and, as a possible fallback solution, the conventional hollow-cavity gyrotron are under investigation. ...

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“…The gyrotron, which based on the electron cyclotron maser instability [1,2] possesses the capability of generating unprecedented power levels (for instance, some can produce megawatt-level millimeter-wave radiation in both long pulse and continuous-wave regimes [3,4]) in the millimeter, sub-millimeter wave and even THz regimes [5] with a myriad of novel applications. The microwave energy is extracted from rotational or transverse energy of a helical electron beam (HEB).…”

Section: Introductionmentioning

confidence: 99%

Analysis of Low Frequency Oscillations in Magnetron Injection Guns

Luo

Yan

et al. 2011

J Infrared Milli Terahz Waves

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In our gyro-TWT experiments, low-frequency oscillations (LFOs) had been observed. LFOs is a physical phenomenon usually caused by the electrons trapped between the magnetron injection guns (MIGs) and the interaction region. In this paper, the formation procedure and physical mechanism of LFOs are reported. Available methods including optimizing the magnetic field distribution in the beam compression region and loading bevel cuts on the second anode are involved to capture the trapped electrons, suppress the LFOs and improve the helical electron beam quality. Simulations and experimental results are in good agreement with each other and also reveal the reasonableness of this means. Finally, the influence of current capture ratio on LFOs and the beam quality are studied. With the current capture ratio increasing, the amplitude of LFOs decreases, the pitch factor maintains a constant about 1.2 and we also demonstrate a low transverse velocity spread about 3%.

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165-GHz Coaxial Cavity Gyrotron

Cited by 61 publications

References 11 publications

Electromagnetic Analysis of Coaxial Gyrotron Cavity With the Inner Conductor Having Corrugations of an Arbitrary Shape

Electromagnetic Analysis of Coaxial Gyrotron Cavity With the Inner Conductor Having Corrugations of an Arbitrary Shape

European research activities towards a future DEMO gyrotron

Analysis of Low Frequency Oscillations in Magnetron Injection Guns

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