Intense Relativistic Beam Research Articles

Envelope analysis of intense relativistic quasilaminar beams in rf photoinjectors:mA theory of emittance compensation

In this paper we provide an analytical description for the transverse dynamics of relativistic, space-chargedominated beams undergoing strong acceleration, such as those typically produced by rf photoinjectors. These beams are chiefly characterized by a fast transition, due to strong acceleration, from the nonrelativistic to the relativistic regime in which the initially strong collective plasma effects are greatly diminished. However, plasma oscillations in the transverse plane are still effective in significantly perturbing the evolution of the transverse phase space distribution, introducing distortions and longitudinal-transverse correlations that cause an increase in the rms transverse emittance of the beam as a whole. The beam envelope evolution is dominated by such effects and not by the thermal emittance, and so the beam flow can be considered quasilaminar. The model adopted is based on the rms envelope equation, for which we find an exact particular analytical solution taking into account the effects of linear space-charge forces, external focusing due to applied as well as ponderomotive RF forces, acceleration, and adiabatic damping, in the limit that the weak nonlaminarity due to the thermal emittance may be neglected. This solution represents a special mode for beam propagation that assures a secularly diminishing normalized rms emittance and it represents the fundamental operating condition of a space-charge-compensated RF photoinjector. The conditions for obtaining emittance compensation in a long, integrated photoinjector, in which the gun and linac sections are joined, as well as in the case of a short gun followed by a drift and a booster linac, are examined. @S1063-651X~97!10706-1#

Electron beam propagation in the ion-focused regime

In this paper the features of propagation of intense relativistic beams are discussed in the environment of low-density (≲1 Torr), partially ionized gas. Beam phenomena in this ion-focused regime (IFR) are found to be analogous to those at much higher density. Several instabilities and dissipative mechanisms have been identified and are compared to their high-density counterparts. Scaling laws are derived for quantitative estimation of these effects. In general, it is found that long propagation distances are possible in the laboratory suggesting that this regime may be useful for controlled beam transport and conditioning.

Linear and nonlinear theory of Cherenkov maser operation in the intense relativistic beam regime.

The linear dispersion relation for axisymmetric TM modes in a cylindrical waveguide lined with a dielectric material and enclosing a thin annular electron beam is derived and solved. Approximate analytic solutions are obtained for both weak and moderate beam regimes. A model of nonlinear saturation is developed. This model, combined with the linear theory in the moderate beam regime, defines the most efficient and compact Cherenkov maser.

Electron Beam Bunch Profile Determination through Cerenkov Radiation

The spatial charge distribution of an electron pulse, along with the beam interaction length, determines the Cerenkov radiation distribution as a function of frequency. An angular distribution of the Cerenkov radiation can, in principle, measure its spatial charge distribution. At a measurement angle of 900 with respect to the beam direction, the form factor is unity which allows a measurement of the total charge contained in the pulse. At other angles, Fourier transforms of the charge distribution may be measured. Possible application to intense relativistic beams in air is discussed.

Adiabatic equations of state for intense relativistic particle beams

Adiabatic equations of state for scalar pressure and anisotropic diagonal pressure have been obtained for intense, relativistic, unneutralized electron beams. These adiabatic equations of state complete the set of fluid equations needed to study beam dynamics and interactions from the fluid point of view. In particular, they facilitate the inclusion of thermal effects of momentum spread effects in stability analyses.

Nanosecond megajoule accelerator for beam induced thermonuclear microexplosions

A novel concept for an intense relativistic beam accelerator is proposed which can deliver megajoule energies on the time-scale of one nanosecond with a total beam power of ∼10 15 W thereby reaching conditions as they are required for the ignition of thermonuclear microexplosions.

Strong interaction of relativistic electron beams with gas and plasma

Abstract The problems of excitation of a new strong turbulent plasma state by intense relativistic beams are discussed. The role of self-accelerating solitons, cavitons and spikons is considered. Modulational instability of relativistic electron beams is shown to differ essentially from known modulational instability. The acceleration of ions and plasma heating by beam-plasma interaction and return current are analyzed.

Numerical simulation of the dynamics of an intense relativistic beam of charged particles

A method for the numerical simulation of stochastic processes in intense relativistic beams of particles moving in electric and magnetic fields is described. A two-dimensional approximation using “coarse particles” is considered. The action functions are first tabulated with respect to three variables. The method combines high speed and good accuracy. The results of a simulation are presented.

1540. A time resolved spectrometer for high intensity relativistic electron beams: J V Walker and J StevensRev Scient Instrum, 45 (2), 1974, 163–170

1540. A time resolved spectrometer for high intensity relativistic electron beams: J V Walker and J StevensRev Scient Instrum, 45 (2), 1974, 163–170

Coaxial Marx Generator for Producing Intense Relativistic Electron Beams

A 600 kV Marx generator installed in a completely coaxial form is developed. The structure reduces the internal inductance down to about 80 nH and hence makes it possible to produce high intensity relativistic electron beams of several kA when applied to a field emission type electron gun. The system is remarkably compact in size having the full length of 1400 mm and the diameter of 250 mm. The rise time of the output voltage pulse is less than 8 nsec.

A time resolved spectrometer for high intensity relativistic electron beams

A spectrometer system designed to measure the time-dependent kinetic energy of electrons from high current pulsed relativistic beam accelerators is described. The spectrometer, consisting of a three-element vacuum Compton diode, is simple, rugged, and self-driving. Calibration data are presented covering the energy range of 150 keV to 16 MeV. Applications and limitations of the spectrometer are discussed.

Coherent Effect in the Preferential Acceleration of Relativistic Solar Heavy Cosmic Ray Nuclei

(Solar Phys.). The observed enrichment of heavy nuclei in the composition of relativistic cosmic rays including solar, may be explained on the basis of a coherent accelerating mechanism. This mechanism requires the existence of high intensity relativistic electron beams or preferably blobs (with number density ≥1011 electrons cm−3) in the accelerating solar regions. The radius of each blob should be less than its plasma wavelength, i.e. of the order of cm.

Concentration and Guidance of Intense Relativistic Electron Beams

None of the field-emitting cathodes using sharp points or edges presently being used in producing pulsed intense relativistic beams has any particular advantage over a smooth well-rounded form having the same over-all dimensions when the interelectrode distance is small enough for the current to be space-charge limited. A new method is reported herein for increasing the current substantially and concentrating the increased current into a beam with a diameter less than 2 mm. A small-diameter dielectric rod or tubing inserted into the cathode and extending towards the anode forms a pinched discharge in a thin layer near the dielectric surface concentrating the current with the pinch and guiding the beam in any desired direction.