Nonneutral Electron Plasma Research Articles

Gabor lens focusing of a proton beam

Gabor or plasma lenses have previously been used to focus intense beams of positive ions at energies from 10 keV to 5 MeV. Such lenses are a possible candidate for matching an intense low-energy proton beam into a radio frequency quadrupole accelerator (RFQ). The conventional solution has been to match an intense beam with two solenoid lenses. This leads to a time-dependent emittance at the RFQ entrance due to neutralization effects. The neutralization time of a space-charge dominated 30–50 mA proton beam in the Gabor lens is <1 μs. A non-neutral electron plasma is contained in the Gabor lens by a 200 G solenoid magnet. The equivalent thin lens focal length of a Gabor lens operated at Fermilab has been determined to be 10 cm. This focusing strength is adequate for matching a proton beam into an RFQ.

Properties of an rf produced magnetically confined nonneutral hot electron plasma

A magnetically confined, nonneutral hot electron plasma is produced by the acceleration and trapping of a low energy (approximately 1 keV) electron beam injected along the axis of an evacuated right circular cylindrical cavity resonator that is excited in the TE111 mode with up to 15 kW of rf power at 0.88 GHz. The cavity axis coincides with that of the static magnetic mirror field (B∼314 G, Rm=1.3:1). The nonneutral (for approximately 10–200 msec) hot electron plasma (We∼100 keV, Ne∼4×1011 electrons, and ne ∼4×109 cm−3) remains trapped for approximately 10 sec. There is a periodic ∇B precessional motion of the trapped electron cloud at a frequency of a few MHz.

Transport of a nonneutral electron plasma due to electron collisions with neutral atoms

Transport of a nonneutral electron plasma across a magnetic field is caused by electron scattering from ambient neutral atoms. A theoretical model of such transport is presented, assuming the plasma is quiescent and the scattering is elastic scattering from infinite mass scattering centers of constant momentum transfer cross section. This model is motivated by recent experiments. A reduced transport equation is obtained by expanding the Boltzmann equation for the electron distribution in inverse powers of the magnetic field. The equation together with Poisson’s equation for the radial electric field, which must exist in a nonneutral column, determine the evolution of the system. When these two equations are properly scaled, they contain only a single parameter: the ratio of initial Debye length to initial column radius. For cases where this parameter is either large or small, analytical solutions, or at least partial solutions, are obtained. For intermediate values of the parameter, numerical solutions are obtained.

Nonneutral electron plasma with a 2.5 MeV mean energy

A pulsed magnetic mirror device is used to produce a nonneutral electron plasma (Ntotal = 8 × 1011) with a mean kinetic energy of 2.5 MeV in a 26 kG field. This represents a substantial increase over previous results.

Properties of Nonneutral Plasma

We describe an apparatus for producing a magnetized column of nonneutral electron plasma which is many Debye lengths in radius. The plasma exhibits the linear and nonlinear electron-wave effects observed in neutralized plasmas.

Variation of the magnetic moment in nonneutral electron plasmas

Exact and approximate expressions are obtained for the magnetic moment of a charged particle, under conditions pertinent to nonneutral electron plasma experiments.