Progress of high power 170 GHz gyrotron in JAEA

Self Cite

Abstract. In JAEA, mode conversion by corrugated waveguide system which is ITER relevant TL system was studied. To evaluate the alignment method for TL assembly, the mode content of middle section of TL was measured while assembly of the TL test stand. Then 5% of LP01 mode purity degradation was found in the long straight section though it was just assembly of 2m straight WGs. Indeed, the mode conversion calculation showed that 5% of mode conversion may occur when the straight section causes 1.0 mm of periodic deflection. To minimize the deflection, the alignment method with adjustment of both position and angle of the WG piece utilizing the laser beam reflection was applied for the TL re-assembling. The mode purity in the same section was improved and mode purity degradation was less than 1%. Finally 93% of LP01 mode purity was achieved at the end of long TL. Next the effect of mode purity by high-power long-pulse operation in TL was studied. Since the TL components are heated during the high-power RF operation, the TL causes deformation due to thermal expansion and deformed TL section induces significant mode conversion loss. The 170GHz gyrotron provided high-power (400kW) and long pulse (500sec) into TL and the beam profile at TL end was measured both before and after the long pulse operation. The mode purity at TL end was 91% before the long pulse and it decreased to 84% after the pulse. The temperature distribution and displacement of TL components were also measured. The measured displacement shows that the vertical sections became S-bend structures and mode conversion loss was estimated. The estimated total mode conversion loss in deformed long TL system was 8%. The estimated value showed good agreement with measurement of mode purity.

Section: Jaea Tl Test Standmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A study of mode purity improvement in the ITER relevant transmission line

Oda

Ikeda

Kajiwara

et al. 2015

Self Cite

Section: Introductionmentioning

confidence: 99%

Development of dual frequency gyrotron and high power test of EC components

Oda

Kajiwara

Takahashi

et al. 2012

Abstract. In JAEA, development of high-power long-pulse gyrotrons is underway. The output power of the gyrotron was applied for high-power long-pulse tests of the transmission line (TL) and the equatorial launcher (EL) mock up for ITER. The feature of design in the dual frequency gyrotron is the simultaneously satisfying the matching of both frequencies at a window and the same radiation angle at an internal mode convertor for both frequencies. The dual frequency gyrotron was developed and high power operations at 170 GHz and 137 GHz were carried out. The 170 GHz high power experiment of 40 m length ITER relevant TL was carried out and transmission efficiency and mode purity change caused by long pulse operation were measured. The mock-up model of EL was also tested using 170 GHz gyrotron. The power transmission through the quasi-optical beam line in EL was demonstrated using the full scale mock up model. Furthermore, the high power test results of the transmission components will be summarized.

“…As a RF power source, ITER pre-prototype of 170 GHz, 1 MW continuous-wave gyrotron which is featured to have a triode-type magnetron injection gun (MIG), a cylindrical resonator working at 170 GHz with TE 31,12 mode, a water-cooled diamond window and a depressed collector is loaned from JAEA [1]. The Gaussian beam output from the gyrotron passes through an edge-cooled diamond window and is coupled to an HE11 corrugated waveguide via two phase correcting mirrors in a matching optics unit (MOU).…”

Section: Introductionmentioning

confidence: 99%

“…The electron energy is significantly reduced by the depressed collector configuration. The beam landing area is elongated in the axial direction using sweeping coils with 2 Hz and the shape of the coil current for sweeping is sawtooth-like to avoid a long stay at turning points [1]. Installation and initial commissioning on KSTAR is successfully carried out in collaboration with JAEA and the EC beam power of 0.65 MW at the window has been achieved before the KSTAR 2011 plasma campaign by the gyrotron commissioning.…”

Section: Introductionmentioning

confidence: 99%

Commissioning of 170 GHz, 1 MW EC H&CD in KSTAR

Jeong

Sakamoto

Joung

et al. 2012

Abstract. The newly installed electron cyclotron heating and current drive (EC H&CD) system with a frequency of 170 GHz was successfully commissioned and used for the second-harmonic ECH-assisted startup in 2011 operational campaign of the KSTAR. As a RF power source, ITER pre-prototype of 170 GHz, 1 MW continuous-wave gyrotron, is loaned from the Japan Atomic Energy Agency (JAEA). During the KSTAR 2011 plamma campaign, maxumum pulse length of 10 sec at 0.6 MW EC beam was reliably injected into the plasma and the 170 GHz second harmonic ECH-assisted start-up was successful leading to reduce the flux consumption at toroidal magnetic field of 3 T. As a result, the flux consumption until the plasma current flat-top was reduced from 4.13 Wb for pure Ohmic to 3.62 Wb (12 % reduction) for the perpendicular injection. When the EC beam is launched with toroidal angle of 20 deg in co-CD direction, more reduced magnetic flux consumption was obtained with 3.14 Wb (24 % reduction) compared with pure OH plasmas. In recent, the gyrotron has been successfully commissioned with the output power of 1 MW and the pulse duration of 20 sec in KSTAR. This paper presents successful commissioning of 170 GHz EC H&CD system in KSTAR as well as the heating and startup experimental results.