Lars Groening

Beam envelope calculations in general linear coupled lattices

The envelope equations and Twiss parameters (β and α) provide important bases for uncoupled linear beam dynamics. For sophisticated beam manipulations, however, coupling elements between two transverse planes are intentionally introduced. The recently developed generalized Courant-Snyder theory offers an effective way of describing the linear beam dynamics in such coupled systems with a remarkably similar mathematical structure to the original Courant-Snyder theory. In this work, we present numerical solutions to the symmetrized matrix envelope equation for β which removes the gauge freedom in the matrix envelope equation for w. Furthermore, we construct the transfer and beam matrices in terms of the generalized Twiss parameters, which enables calculation of the beam envelopes in arbitrary linear coupled systems.

Results of the experiments on emittance transfer EMTEX

EMTEX is an experimental setup to proof the principle of transverse emittance partitioning on an ion beam. According to simulations it is possible to transfer emittance by changing only the magnetic field of a solenoid with a charge state changing stripper inside. The change of charge state in the solenoid changes the set of eigenemittances and the skew quadrupoles serve to remove inter-plane correlations. The field strength of the solenoid determines the amount of transfer between the eigenemittances. A detailed description of the concept and the beam line itself is given in [1].

Status of the Compact LEBT Project

To fulfil the intensity requirements for FAIR, a dedicated high current uranium ion source and Low Energy Beam Transport line will be built at the High Current Injector HSI [1]. This new injection line (Compact-LEBT) will be integrated into the existing complex with two branches, designed as a straight injection line without bending magnet (fig. 1). The joint use of the existing matching line (from switching magnet to RFQ) is foreseen.

Upgrade preparation for the 1.4 MeV/u gas stripper system for FAIR

A key projectile for the FAIR facility will be U. In routine operation of the GSI UNILAC, U is generated by a MEVVA ion source that delivers ions with comparably low charge states (4), which are accelerated to 1.4 MeV/u in the high current injector (HSI). The 1.4 MeV/u beam passes a region of high gas density, in which the charge is increased to 28 by stripping of electrons. [1] Generally, higher intensities at charge states, preferably above 28, are desirable. This would allow to operate the accelerator more reliable and efficiently. To optimize the stripping efficiency and potentially increase the achieved ion charge states a program to upgrade the gas stripper has started. The modified stripper setup is depicted in Fig. 1. As a first modification, switching from the continuously fed supersonic N2-jet to a pulsed gas injection, synchronized with the beam timing structure, has been implemented. This allows to increase the gas pressure inside the stripper chamber during a beam pulse, while still reducing the total gas flow. The gas injection was positioned inside a T-fitting, which was installed in the main stripper chamber to match the beamline. In a first test the pressure in the main stripping section as function of the opening time of the valve and the pressure along the beamline adjacent to the gas stripper section were measured.