Gun design criteria for the refurbishment of the first prototype of the EU 170GHz/2MW/CW coaxial cavity gyrotron for ITER

Pagonakis, I.; Hogge, J.‐P.; Goodman, T.; Alberti, S.; Piosczyk, B.; Illy, S.; Rzesnicki, T.; Kern, Stefan; Lievin, C.

doi:10.1109/icimw.2009.5324625

Cited by 10 publications

(5 citation statements)

References 6 publications

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“…As a result the final design is not showing any potential well, in particular at the rear part of the MIG, while the electrons which are emitted by the cathode surface with zero velocity and which could contribute to the generation of the beam halo current are not magnetically trapped [9,10]. However, this might not be correct for secondary electrons emitted from the surface.…”

Section: A Magnetron Injection Gun (Mig)mentioning

confidence: 94%

From Series Production of Gyrotrons for W7-X Toward EU-1 MW Gyrotrons for ITER

Jelonnek

Albajar

Alberti

et al. 2014

IEEE Trans. Plasma Sci.

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Abstract-Europe is devoting significant joint efforts to develop and to manufacture MW-level gyrotrons for electron cyclotron heating and current drive of future plasma experiments. The two most important ones are the stellarator Wendelstein W7-X at Greifswald and the tokamak ITER at Cadarache. While the series production of the 140 GHz, 1 MW, CW gyrotrons for the 10 MW ECRH system of stellarator W7-X is proceeding, the European GYrotron Consortium (EGYC) is presently developing the EU-1 MW, 170 GHz, CW gyrotron for ITER. The initial design had already been initiated in 2007, as a risk mitigation measure during the development of the advanced ITER EU-2 MW coaxial-cavity gyrotron. The target of the ITER EU-1 MW conventional-cavity design is to benefit as much as possible from the experiences made during the development and series production of the W7-X gyrotron and of the experiences gained from the earlier EU-2 MW coaxial-cavity gyrotron design. Hence, the similarity of the construction will be made visible in the present article. During 2012, the scientific design of the ITER EU-1 MW gyrotron components has been finalized. In collaboration with the industrial partner Thales Electron Devices (TED), Vélizy, France, the industrial design of the technological parts of the gyrotron is being completed. A short-pulse prototype is under development to support the design of the CW prototype tube. The technological path towards the EU ITER-1MW gyrotron and the final design will be presented. . Both experiments are relying on electron cyclotron resonance heating (ECRH) as the main heating method for steady state operation, while in addition it is planned for ITER to apply electron cyclotron resonance technique for current drive (ECCD). ECRH & ECCD offer the compatibility to the various physics demands, such as controlled plasma start-up, steady state plasma control, and performance optimization by plasma profile shaping. It offers excellent coupling to the plasma, remote launching and very good localization of the absorbed power. Index Terms-PlasmaThe construction of the stellarator W7-X is almost completed and the device is approaching the commissioning phase [3]. W7-X operation will be supported by a 10 MW continuous wave ECRH system working at 140 GHz in 2 nd harmonic X-or O-mode. To date, the ECRH-system of W7-X is in stand-by with already 5 out of 10 gyrotrons operational. The series production of the W7-X 1 MW, CW gyrotrons [4,5] for the 10 MW ECRH system is proceeding.The European gyrotron development for ITER started with an advanced 170 GHz, 2 MW coaxial-cavity design. RF tests with an industrial CW prototype were done at the European test facility at EPFL-CRPP Lausanne in December 2011 [6]. The prototype did show an excellent voltage stand-off. It was directly possible to excite the nominal operating TE 34,19 -mode. The output RF-beam intensity was in good agreement with the expected one. Without further optimization, the RF output power reached the level of almost 2.1 MW in short-pulse (1 ms) operation with sin...

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Section: A Magnetron Injection Gun (Mig)mentioning

confidence: 94%

From Series Production of Gyrotrons for W7-X Toward EU-1 MW Gyrotrons for ITER

Jelonnek

Albajar

Alberti

et al. 2014

IEEE Trans. Plasma Sci.

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“…The geometry used in this study, represented in Fig. 1, is based on the electron gun geometry used in the first prototype 18 of the 170 GHz 2 MW coaxial gyrotron designed for ITER, see Fig. 2.…”

Section: B Geometry and Numerical Parametersmentioning

confidence: 99%

“…2. This particular Magnetron Injection Gun (MIG) was subject to voltage breakdown and detrimental leakage currents for specific magnetic field configurations, and had to be redesigned to allow nominal operation 18 . The configuration of this study focuses on the corona ring region of the original prototype gun, and uses the same magnetic field used for the prototype gyrotron with 𝐵 ∼ 0.28 T 39 .…”

Section: B Geometry and Numerical Parametersmentioning

confidence: 99%

“…The study of nonneutral plasmas is also relevant to the development of gyrotron electron guns, where secondary electron clouds (i.e. not belonging to the main electron beam) can remain locally trapped, and accumulate in effective potential wells due to the local electric and magnetic field topology 18,19 . The trapped electrons, if released by instabilities or shielding of the wells by space-charge effects, can lead to detrimental and even damaging currents that prevent nominal gyrotron operation.…”

Section: Introductionmentioning

confidence: 99%

“…Such ionisation phenomena, combined with the existence of trapping potential wells, have been linked to the observed detrimental currents in gyrotron guns 19 . To avoid this problem, a design criterion has been defined which imposes the absence of any vacuum potential well in the electron gun by a careful modification of the electrodes shapes 18 . However, this process becomes highly demanding from an engineering point of view, and relaxed design criteria are highly desirable.…”

Section: Introductionmentioning

confidence: 99%

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Self-consistent formation and steady-state characterisation of trapped high energy electron clouds in the presence of a neutral gas background

Bars¹,

Hogge²,

Loizu³

et al. 2022

Preprint

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This study considers the self-consistent formation and dynamics of electron clouds interacting with a background neutral gas through elastic and inelastic (ionisation) collisions in coaxial geometries similar to gyrotron electron guns. These clouds remain axially trapped as the result of crossed magnetic field lines and electric equipotential lines creating potential wells similar to those used in Penning traps. Contrary to standard Penning traps, in this study we consider a strong externally applied radial electric field which is of the same order as that of the space-charge field. In particular, the combination of coaxial geometry, strong radial electric fields and electron collisions with the residual neutral gas (RNG) present in the chamber induce non-negligible radial particle transport and ionisation. In this paper, the dynamics of the cloud density and currents resulting from electron-neutral collisions are studied using a 2D3V particle-in-cell code. Simulation results and parametric scans are hereby presented. Finally, a fluid model is derived to explain and predict the cloud peak density and peak radial current depending on the externally applied electric and magnetic fields, and on the RNG pressure.

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