An Introduction to Beam Physics

The field of beam physics touches many areas of physics, engineering, and the sciences. In general terms, beams describe ensembles of particles with initial conditions similar enough to be treated together as a group so that the motion is a weakly nonlinear perturbation of a chosen reference particle. Particle beams are used in a variety of areas

COMPACT GANTRY WITH LARGE ENERGY ACCEPTANCE*

Abstract Existing proton beam therapy gantries weight 100+ tons and require large (three stories) heavily shielded rooms to house them. Pioneering work by Trbojevic et al [1] using fixed field alternating gradient (FFAG) gantry concept demonstrated the potential of both reducing the size of the gantry as well as increasing the energy acceptance. In this paper we present a new variation of a compact superconducting FFAG gantry. The gantry consists of three, small aperture, 7-bend achromat sections followed by transverse scanning magnets. The 7-bend achromat contains high field superconducting combined-function bending magnets. This gantry provides a large (+/-20%) energy acceptance for fast depth scanning. We present the analysis of the beam tracking and show that it is possible to scan the ion beam over a large volume of roughly 1 cubic liter, with minimal distortion in the beam shape without changing the fields of the superconducting magnets

Thermal limit to the intrinsic emittance from metal photocathodes

Measurements of the intrinsic emittance and transverse momentum distributions obtained from a metal (antimony thin film) photocathode near and below the photoemission threshold are presented. Measurements show that the intrinsic emittance is limited by the lattice temperature of the cathode as the incident photon energy approaches the photoemission threshold. A theoretical model to calculate the transverse momentum distributions near this photoemission threshold is presented. An excellent match between the experimental measurements and the theoretical calculations is demonstrated. These measurements are relevant to low emittance electron sources for Free Electron Lasers and Ultrafast Electron Diffraction experiments

FIRST EXPERIMENTAL RESULTS FROM DEGAS, THE QUANTUM LIMITED BRIGHTNESS ELECTRON SOURCE

The construction of DEGAS (DEGenerate Advanced Source), a proof of principle for a quantum limited brightness electron source, has been completed at the Lawrence Berkeley National Laboratory. The commissioning and the characterization of this source, designed to generate coherent single electron 'bunches' with brightness approaching the quantum limit at a repetition rate of few MHz, has been started. In this paper the first experimental results are described