Speaker
Description
A pulsed electron lens for space charge compensation is being developed at GSI to increase the achievable beam intensities in the synchrotrons SIS-18 and SIS-100 of the FAIR project where space charge constitutes a major performance constraint during the process of injection of a primary beam into the synchrotron. Studies based on numerical simulations for SIS-100 have shown that a few symmetrically distributed electron lenses could increase the space charge limit by up to 50% while a larger number could potentially raise this to 100% [1]. As a first step, the concept will be investigated in SIS-18 with a single electron lens. To this end, the existing electron cooler will be modified and used as a test-bed. Compensation is foreseen on the bunched beam, following the changing space charge tune shift over the cycle. Consequently, the electron beam current coming out of the gun with a peak current of up to 15 A must be modulated at frequencies ranging from 400 kHz to 1 MHz. The longitudinal magnetic fields for confining the electron beam have to be considerably higher in the case of space charge compensation than in the case of electron cooling. These requirements present challenges for both development of components for the electron lens and modification of the optics of the synchrotron as a whole. One aspect in particular regards modelling of the deflection of the primary beam by the magnetic fields of the toroidal coils of the electron lens over many beam revolution periods. The status of the electron lens project with an emphasis on its relevance to SIS-18 is given.
[1] A. Oeftiger and O. Boine-Frankenheim, "Pulsed Electron Lenses for Space Charge Mitigation", Phys. Rev. Lett., vol. 132, p. 175001, 2024, doi: 10.1103/PhysRevLett.132.175001.