Laboratory study of kinetic instabilities in a nonequilibrium mirror-confined plasma

Viktorov, M. E.; Mansfeld, D. A.; Golubev, S. V.

doi:10.1209/0295-5075/109/65002

Cited by 23 publications

(27 citation statements)

References 31 publications

(38 reference statements)

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“…Such EED is prone to kinetic electron cyclotron instabilities. 10 Kinetic plasma instabilities driven by the anisotropy of the EED have been detected and studied in ECR-heated mirror plasmas 11,12 and recently in a minimum-B ECRIS. 5,13 Each onset of the instability is associated with strong microwave emission from the plasma followed by a burst of electrons ejected into the loss cone and thus escaping the magnetic trap.…”

Section: Electron Cyclotron Instabilities In Ecr-heated Plasmasmentioning

confidence: 99%

Limitation of the ECRIS performance by kinetic plasma instabilities (invited)

Tarvainen

Kalvas

Koivisto

et al. 2015

Review of Scientific Instruments

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Limitation of the ECRIS performance by kinetic plasma instabilities (invited)Tarvainen, Olli; Kalvas, Taneli; Koivisto, Hannu; Komppula, Jani; Kronholm, Risto; Laulainen, Janne; Izotov, I.; Mansfeld, D.; Skalyga, V.; Toivanen, V.; Machicoane, G.Tarvainen, O., Kalvas, T., Koivisto, H., Komppula, J., Kronholm, R., Laulainen, J., . . . Machicoane, G. (2016 Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropic electron velocity distribution. The instabilities are associated with strong microwave emission and periodic bursts of energetic electrons escaping the magnetic confinement. The instabilities explain the periodic ms-scale oscillation of the extracted beam current observed with several high performance ECRISs and restrict the parameter space available for the optimization of extracted beam currents of highly charged ions. Experiments with the JYFL 14 GHz ECRIS have demonstrated that due to the instabilities the optimum B min -field is less than 0.8B ECR , which is the value suggested by the semiempirical scaling laws guiding the design of ECRISs. C 2015 AIP Publishing LLC. [http://dx

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Section: Electron Cyclotron Instabilities In Ecr-heated Plasmasmentioning

confidence: 99%

Limitation of the ECRIS performance by kinetic plasma instabilities (invited)

Tarvainen

Kalvas

Koivisto

et al. 2015

Review of Scientific Instruments

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“…First experimental data on the high-resolution dynamic spectra of five different types of kinetic instabilities in ECR discharge plasma were recently reported in Ref. 7.…”

Section: Introductionmentioning

confidence: 99%

Cyclotron instability in the afterglow mode of minimum-B ECRIS

Izotov

Kalvas

Koivisto

et al. 2015

Review of Scientific Instruments

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It was shown recently that cyclotron instability in non-equilibrium plasma of a minimum-B electron cyclotron resonance ion source (ECRIS) causes perturbation of the extracted ion current and generation of strong bursts of bremsstrahlung emission, which limit the performance of the ion source. The present work is devoted to the dynamic regimes of plasma instability in ECRIS operated in pulsed mode. Instability develops in decaying plasma shortly after heating microwaves are switched off and manifests itself in the form of powerful pulses of electromagnetic emission associated with precipitation of high energy electrons. Time-resolved measurements of microwave emission bursts are presented. It was found that even in various gases (helium and oxygen were studied) and at different values of magnetic field and heating power, the dynamic spectra demonstrate common features: decreasing frequency within a single burst as well as from one burst to another.

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“…Different stages of pulsed ECR discharge offer the opportunity to simultaneously study wave-particle interactions for essentially different plasma parameters [44]. However, highly transient spectra with many repeated frequency sweeps have been observed only in a decaying plasma (N h N c ) and only with a pronounced delay after the ECR heating switch-off.…”

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Observation of quasi-periodic frequency sweeping in electron cyclotron emission of nonequilibrium mirror-confined plasma

Viktorov¹,

Shalashov²,

Mansfeld³

et al. 2016

EPL

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-Chirping frequency patterns have been observed in the electron cyclotron emission from strongly nonequilibrium plasma confined in a table-top mirror magnetic trap. Such patterns are typical for the formation of nonlinear phase space structures in a proximity of the wave-particle resonances of a kinetically unstable plasma, also known as the "holes and clumps" mechanism. Our data provides the first experimental evidence for acting of this mechanism in the electron cyclotron frequency domain.Introduction. -Resonant interaction of electromagnetic waves and charged particles plays an important role in the dynamics of magnetoactive plasma confined in space and laboratory magnetic traps. One of the most intriguing manifestations of such interaction is emission of broadband radiation with regular variations of dynamical spectra, e.g. quasi-periodic bursts with a frequency sweeping, resulting from the development of kinetic plasma instabilities. Such events are common features of experimental plasmas. Kinetic instabilities are caused by the presence of positive gradients in the velocity distribution of resonant particles, whose formation is universal for both space and laboratory plasma. In space magnetic traps, the sources of free energy are formed due to different acceleration mechanisms of particles, such as betatron acceleration, plasma-wave turbulence and magnetic reconnection. Under laboratory conditions, the energetic particles with an anisotropic velocity distribution can be formed due to the features of plasma heating, when the energy of the external source is embedded in a specific region of the phase space, such as provided by resonant cyclotron heating or neutral beam injection in magnetic fusion experiment. Spatial gradients can also result in instabilities of waves for which the diffusion in real space is coupled to the diffusion in velocity space due to conservation of invariants of particle motion in inhomogeneous systems energy; this type of instability is exploited in the so-called alpha channeling proposals [1,2]. As a rule, plasma confined in laboratory traps consists of at least two components, one

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Laboratory study of kinetic instabilities in a nonequilibrium mirror-confined plasma

Cited by 23 publications

References 31 publications

Limitation of the ECRIS performance by kinetic plasma instabilities (invited)

Limitation of the ECRIS performance by kinetic plasma instabilities (invited)

Cyclotron instability in the afterglow mode of minimum-B ECRIS

Observation of quasi-periodic frequency sweeping in electron cyclotron emission of nonequilibrium mirror-confined plasma

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