Pulsed Electron Lenses for Space Charge Mitigation

To produce ultimate high-brightness hadron beams, synchrotrons need to overcome a most prominent intensity limitation, i.e., space charge. This Letter characterizes the potential of pulsed electron lenses in detailed 3D tracking simulations, key to which is a realistic machine and space charge model. The space charge limit, imparted by betatron resonances, is shown to be increased by up to 50% using a low symmetric number of electron lenses in application to the Facility for Antiproton and Ion Research SIS100 synchrotron. Conceptually, a 100% increase is demonstrated with a larger number of electron lenses, which is found to rapidly saturate near the theoretical 2D limit.

Figure 1

Layout of the GSI SIS18 pulsed electron lens (image from Ref. [27]). The ion beam traverses the electron lens insertion from the left to the right in the straight beam pipe. The electron beam is generated in the cathode on the top left, and a modulation grid shapes the electron pulse, which then follows the white arrow: A toroid (violet) guides into the $L=3.36$-m-long interaction region with focusing solenoid fields before a second toroid directs the electron beam away from the circulating ion bunch onto the collector on the top right.

Figure 2

Top: incoherent space charge tune footprints against electron lens strength. Bottom: corresponding vertical extent of footprint (black solid line, only space charge; gray dashed line, including chromaticity).

Figure 3

Beam loss in transverse tune space for SIS100 with sixfold superperiodicity and three electron lenses, the plotted tune diagrams show four different linear compensation degrees $\alpha$ at FAIR design bunch intensity $N=N_0$.

Figure 4

Low-loss tune area contours at various intensities for six electron lenses ($\alpha =0.5$).

Figure 5

SIS100 space charge limit. Low-loss tune area against intensity for various electron lens configurations.