Demonstration of Plasma Startup by Coaxial Helicity Injection

Raman, R.; Jarboe, T.R.; Nelson, B. A.; Izzo, V.A.; O'Neill, R.G.; Redd, A. J.; Smith, Roger

doi:10.1103/physrevlett.90.075005

Cited by 57 publications

(34 citation statements)

References 9 publications

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“…On HIT-II, a new type of CHI termed "transient CHI" was developed 146,147 where, with the injector flux footprints sufficiently close together, the injector current is rapidly reduced to zero. This causes the oppositely directed field lines in the injector region to reconnect causing closed flux surfaces.…”

mentioning

confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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“…In addition, once the discharge initiated, as a result of the significant external inductance required to operate the power supply the injector current could not be rapidly reduced, as required for transient CHI. Experiments on the HIT-II concept exploration device showed that a capacitor based power supply would be more suitable for transient CHI startup [12]. As a result a suitable power supply was designed to meet the requirements for transient CHI operation in NSTX.…”

Section: Hardware Upgrades That Enabled Implementation Of Transient Cmentioning

confidence: 99%

“…However, for the purpose of initial plasma startup it was found in the HIT-II ST that a new mode of CHI operation in an ST, referred to as transient CHI [12], which involves only axisymmetric magnetic reconnection works very well and produces useful closed flux equilibrium. In transient CHI, the initial poloidal field configuration is chosen such that the plasma carrying the injected current rapidly expands into the chamber.…”

Section: Introductionmentioning

confidence: 99%

Non-inductive solenoid-less plasma current startup in NSTX using transient CHI

et al. 2007

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“…It has allowed HIT-II consistently to produce higher current discharges than was possible by induction alone. It is largely insensitive to field errors and changing wall conditions (11) .…”

Section: Transient Chimentioning

confidence: 99%

“…This mode of CHI operation can be referred to as steady state CHI, during which the CHI injector circuit is continuously driven for some time (t pulse > t L/R ). A very significant development during the past two years has been the demonstration of a new mode of CHI operation, referred to as transient C H I (11) . This mode involves an axisymmetric reconnection and has been highly successful on the HIT-II experiment.…”

Section: Introductionmentioning

confidence: 99%

Solenoid-free Plasma Startup in NSTX using Coaxial Helicity Injection

Raman

Jarboe

Bell

et al. 2005

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The favorable properties of the Spherical Torus (ST) arise from its very small aspect ratio. However, small aspect ratio devices have very restricted space for a substantial central solenoid. Thus methods for initiating the plasma current without relying on induction from a central solenoid are essential for the viability of the ST concept. Coaxial Helicity Injection (CHI) is a promising candidate for solenoid-free plasma startup in a ST. Recent experiments on the HIT-II ST at the University of Washington, have demonstrated the capability of a new method, referred to as transient CHI, to produce a high quality, closed-flux equilibrium that has then been coupled to induction, with a reduced requirement for transformer flux [R. Raman, T.R. Jarboe, B.A. Nelson, et al., Phys. Rev. Lett., 075005-1 (2003)]. An initial test of this method on NSTX has produced about 140 kA of toroidal current. Modifications are now underway to improve capability for transient CHI in NSTX.

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Demonstration of Plasma Startup by Coaxial Helicity Injection

Cited by 57 publications

References 9 publications

Recent progress on spherical torus research

Recent progress on spherical torus research

Non-inductive solenoid-less plasma current startup in NSTX using transient CHI

Solenoid-free Plasma Startup in NSTX using Coaxial Helicity Injection

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