Extraction and focusing of intense ion beams from a magnetically insulated diode

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Section: £äçAeçðëçunclassified

Collective ion acceleration in systems with a virtual cathode

Дубинов¹,

Kornilova²,

Селемир³

2002

Usp. Fiz. Nauk

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“…1 " 3 The reduction of electron loss is accomplished via the self magnetic field in a pinched electron-beam diode, 1 the reflexing of electrons in a reflex triode, 2 and an applied magnetic field in a magnetically insulated (MI) diode. 3 We report the production of a converging proton beam with a MI diode driven by the 10 12 -W Proto I dual-puljse-line generator. 4 A proton beam with peak current of 360 kA at voltages between 0.8 and 1.4 MV has been diagnosed and focused with 25% efficiency onto thin conical targets with nominal lengths and diameters of 1 cm.…”

mentioning

confidence: 99%

Production of 0.5-TW Proton Pulses with a Spherical Focusing, Magnetically Insulated Diode

Johnson¹,

Kuswa²,

Farnsworth³

et al. 1979

Phys. Rev. Lett.

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The production, focusing, and numerical simulation of a 0.5-TW proton beam is reported. This beam is produced with a spherical, magnetically insulated, ion diode fed symmetrically by the dual-pulse-line Proto I generator. The ions are accelerated with electric fields due to a virtual cathode supported by magnetic field surfaces. Approximately 75% of the diode electrical power is delivered to ions and 25% of the ion beam is focused upon thin, 1-cmdiam, 1-cm-long conical targets to produce the first experimental ion-driven implosions.Recent advances have been made in sources of intense pulsed ion beams for magnetic and inertial confinement fusion. 1 " 3 The reduction of electron loss is accomplished via the self magnetic field in a pinched electron-beam diode, 1 the reflexing of electrons in a reflex triode, 2 and an applied magnetic field in a magnetically insulated (MI) diode. 3 We report the production of a converging proton beam with a MI diode driven by the 10 12 -W Proto I dual-puljse-line generator. 4 A proton beam with peak current of 360 kA at voltages between 0.8 and 1.4 MV has been diagnosed and focused with 25% efficiency onto thin conical targets with nominal lengths and diameters of 1 cm.The apparatus is shown in Fig. 1. The applied magnetic field rises in 70 jzsec and is spherically contoured in the diode gap by the 15-cm radius aluminum anode. The anode then is pulsed positive via the center electrode of the disk triplate transmission line of the Proto I generator. A virtual cathode then is produced by electrons which are emitted from the cathode disks and spiral axially along magnetic field lines to establish a uniform equipotential surface near the anode. Anode plasma from a nylon mesh mounted upon the anode (thought to be formed by surface flashover or leakage electrons) is the source of protons or higher-Z ions which are accelerated. Since all magnetic field lines are contained between the anode surface (neglecting a 2-mm magnetic field soak in) and diode center line, the ions are emitted from the anode with zero canonical angular momentum and ideally can be focused to the center line. When drifting through the magnetic field, the ions are space-charge neutralized by electrons emitted from the walls of the drift region.The diode was numerically simulated with a two-dimensional (2D) steady-state, particle-incell code 5 with electron and ion motion treated in self-consistent electric and magnetic fields. The applied and self magnetic fields, which are excluded from the anode but fully penetrate the thin disk cathodes, are computed by solving the one-component vector-potential equation Figure 2 contains a typical instantaneous ion simulationparticle map together with lines of equal intensity I? app assuming cylindrical symmetry for the diode. The assumed diode voltage is 1.2 MV and £ app in the diode gap is 13 kG. Atypical electron trajectory is shown at the position of the virtual cathode near one Z? app field line. Complete spacecharge neutralization was assumed between the disks in this simulat...

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Extraction and focusing of intense ion beams from a magnetically insulated diode

Cited by 68 publications

References 9 publications

Tearing-mode stability properties of a diffuse anisotropic field-reversed ion layer at marginal stability

Tearing-mode stability properties of a diffuse anisotropic field-reversed ion layer at marginal stability

Collective ion acceleration in systems with a virtual cathode

Production of 0.5-TW Proton Pulses with a Spherical Focusing, Magnetically Insulated Diode

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