No abstract

The application of laser accelerated ion beams in Hadron therapy requires ion beam optics with unique features. It has been shown that due to the spectral and spatial distribution of laser accelerated protons a lens based focusing system has advantages over aperture collimated beam formation. We present a compact ion optical system with therapy applications, based on Gabor space charge lenses for collecting, focusing and energy filtering the laser produced proton beam. For a full therapy solution, a scenario based on three space charge lenses is presented. In this very compact beam line an aperture is foreseen for energy selection.

Aberrations due to solenoid focusing of a multiply charged high-current ion beam Rev.Particle-beam approach to collective instabilities-application to space-charge dominated beams AIP Conf.Space charge lenses provide strong cylinder symmetric focusing for low-energy high-perveance particle beams using a stable space charge cloud. They need drastically reduced magnetic and electrostatic field strength compared with conventional systems and are superior for a degree of lens filling above 17%. They can theoretically provide linear transformation in phase space and reduce beam aberrations and space charge forces. The density distribution of the enclosed space charge is given by the transverse and longitudinal enclosures of the cloud. By the use of self-consistent simulations of the space charge cloud, the focusing properties of space charge lenses in the presented design can be forecasted with sufficient quality. The presented simulations show that the theoretical values can be reached locally. The results of our investigations on the beam transport in a high-current test injector equipped with space charge lenses, including emittance measurements, will be presented and discussed. They show that significant improvements of lens operation have been reached by the reduction of the residual gas pressure and a careful design of the external fields using numerical simulation techniques to calculate the local density distributions. Comparisons of the experimental results with the beam transport simulations show good agreement concerning both focusing strength and linearity of phase space transformation. For the lens design used, the observed degree of lens filling is at least 38% of the theoretical value and more than twice the threshold value.

A noninvasive, compact laserwire system has been developed to measure the transverse emittance of an H − beam and has been demonstrated at the new LINAC4 injector for the LHC at CERN. Light from a low power, pulsed laser source is conveyed via fiber to collide with the H − beam, a fraction of which is neutralized and then intercepted by a downstream diamond detector. Scanning the focused laser across the H − beam and measuring the distribution of the photo-neutralized particles enables the transverse emittance to be reconstructed. The vertical phase-space distribution of a 3 MeV beam during LINAC4 commissioning has been measured by the laserwire and verified with a conventional slit and grid method.