Steady state high power test system at 3.7 GHz

Bora, D.; Dani, S.; Gangopadhyay, S.; Jadav, Bhanu Pratap Singh; Jha, M; Kadia, B.R.; Khilar, P.; Kulkarni, Sanjay; Kushwah, M.; Patel, Amit; Parmar, K. G.; Parmar, Pramod R.; Rajnish, Kumar; Raghuraj, S.; Rao, S.L.; Samanta, Kamal K.; Sathyanarayana, K.; Shah, P.; Sharma, P. K.; Srinivas, Y.; Trivedi, Rajesh; Verghese, George C.

doi:10.1016/s0920-3796(01)00277-0

Cited by 5 publications

(2 citation statements)

References 1 publication

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“…It is the key element of all the present devices addressing long pulse issues, as it exhibits the highest current drive efficiency in present devices, and is fundamental for their inductive flux saving needs. In particular, all superconducting tokamaks (EAST [1], HT-7 [2], KSTAR [3], SST1 [4], Tore Supra [5] and TRIAM-1M [6]) have or plan LHCD capability. Since the emergence of the close link between the current profile and the turbulent transport properties, a strong renewed interest was found for LHCD in advanced tokamak (AT) researches.…”

Section: Introductionmentioning

confidence: 99%

A lower hybrid current drive system for ITER

et al. 2009

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Section: Introductionmentioning

confidence: 99%

A lower hybrid current drive system for ITER

et al. 2009

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“…For the 3.7 GHz LHCD system, a WR-284 standard high power test bed [5] powered by a 500 kW Klystron has been made ready for testing of various transmission line components. CW output power as function of high voltage is shown in figure 14.…”

Section: Lhcd Systemmentioning

confidence: 99%

Test results on systems developed for the SST-1 tokamak

Bora¹,

Team²

2003

Nucl. Fusion

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The steady state superconducting tokamak (SST-1) is a large aspect ratio tokamak, configured to run double null diverted plasmas with significant elongation (κ) and triangularity (δ). Superconducting (SC) magnets are deployed for both the toroidal and poloidal field coils in SST-1. A NbTi based cable-in-conduit conductor (CICC) has been fabricated by M/S Hitachi Cables Ltd., Japan under specification and supervision of the Institute for Plasma Research (IPR). The suitability of this CICC for the SST-1 magnets has been validated through test carried out on a model coil wound from this CICC. Toroidal and poloidal SC magnets have been fabricated and factory acceptance tests have been performed. SC magnets require liquid helium (LHe) cooled current leads, electrical isolators at LHe temperature, superconducting bus bars and LHe transfer lines. Full scale prototypes of these have been developed and tested successfully. SC magnets will be cooled to 4.5 K by forced flow of supercritical helium through the CICC. A 1 kW grade liquefier/refrigerator has been installed and is in final stages of commissioning at IPR. SST-1 deploys a fully welded ultra high vacuum vessel, made up of 16 vessel sectors (VSs) having ports and 16 rings with -shaped cross-section. To establish the fabrication methodology for this, a fullscale prototype of the vessel with two VSs and three rings has been fabricated and tested successfully. Based on this the fabrication of the VSs and rings is in final stage of fabrication. Liquid nitrogen cooled radiation shield are deployed between the vacuum vessel and SC magnets as well as SC magnets and cryostat, to minimize the radiation losses at the SC magnets. SST-1 will have three different high power radio frequency systems to additionally heat and non-inductively drive plasma current to sustain the plasma in steady state for a duration of up to 1000 s. Ion cyclotron resonance frequency (ICRF) and electron cyclotron resonance frequency (ECRF) systems will primarily be used for heating the plasma while lower hybrid waves will be used for non inductive lower hybrid current drive (LHCD). A neutral beam injection with peak power of 0.8 MW with variable beam energy in range of 10–80 keV will be used as additional auxiliary heating system. A number of prototypes for various critical components have confirmed the fabrication methodology. The fabrication of most of the subsystems is nearing completion and many components have already been accepted on site. Erection and installation of the base of the mechanical structure has already been initiated in the SST hall. This paper reports on the results of the tests on various prototypes and actual components to be used on SST-1 for various subsystems.

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Characteristics of electron cyclotron resonance plasma formed by lower hybrid current drive grill antenna

et al. 2008

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A 3.7 GHz system, which is meant for LHCD experiments on ADITYA tokamak, is used for producing ECR discharge. The ECR discharge is produced by setting the appropriate resonance magnetic field of 0.13 T, with hydrogen at a fill pressure of about 5 × 10 −5 Torr. The RF power, up to 10 kW (of which ∼50% is reflected back), with a typical pulse length of 50 ms, is injected into the vacuum chamber of the ADITYA tokamak by a LHCD grill antenna and is used for plasma formation. The average coupled RF power density (the RF power/a typical volume of the plasma) is estimated to be ∼5 kW/m 3 . When the ECR appears inside the tokamak chamber for the given pumping frequency (f = 3.7 GHz) a plasma with a density (n e) ∼ 4 × 10 16 m −3 and electron temperature ∼8 eV is produced. The density and temperature during the RF pulse are measured by sets of Langmuir probes, located toroidally, on either side of the antenna. Hα signals are also monitored to detect ionization. An estimate of density and temperature based on simple theoretical calculation agrees well with our experimental measurements. The plasma produced by the above mechanism is further used to characterize the ECR-assisted low voltage Ohmic start-up discharges. During this part of the experiments, Ohmic plasma is formed using capacitor banks. The plasma loop voltage is gradually decreased, till the discharge ceases to form. The same is repeated in the presence of ECR-formed plasma (RF pre-ionization), formed 10 ms prior to the loop voltage. We have observed that (with LHCD-induced) ECR-assisted Ohmic start-up discharges is reliably and repeatedly obtained with reduced loop voltage requirement and breakdown time decreases substantially. The current ramp-up rates also decrease with reduced loop voltage operation. These studies established that ECR plasma formed with LHCD system exhibits similar characteristics as reported earlier by dedicated ECR systems. This experiment also addresses the issue of whether ECR plasma formed with grill antenna exhibits similar behavior as that formed by single waveguide ECR antenna. Our experimental observations suggest that the characteristics of (LHCD system-induced) ECR-assisted Ohmic start-up discharges show similar properties, reported earlier with normal ECR-assisted Ohmic start-up discharges and hence LHCD system may be used as ECR system at reduced toroidal magnetic field for other applications like wall conditioning.

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Steady state high power test system at 3.7 GHz

Cited by 5 publications

References 1 publication

A lower hybrid current drive system for ITER

A lower hybrid current drive system for ITER

Test results on systems developed for the SST-1 tokamak

Characteristics of electron cyclotron resonance plasma formed by lower hybrid current drive grill antenna

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