Space Charge Suppression for Uneven Emittances

The intensity of low and intermediate energy accelerators and storage rings is limited by space charge effects. An increase of the space charge tune shift may lead to lifetime degradation and coherent instability. A method to suppress the space charge effect is suggested for a beam with two uneven emittances. It has been shown that for a beam with uneven emittances, use of the circular optics makes the space charge tune shift equal to its planar value in the large-emittance direction. This removes a limit on the smaller emittance from the space charge side. Thus, since flat beams can be extremely bright, they could find their use in various applications: ion-electron colliders, nuclear fusion, medicine, and others. One additional possibility for the use of these beams relates to the fact that in a matched solenoid the CAM-dominated beam is transformed into a parallel beam. This transformation is essential for relativistic electron cooling of antiprotons at Fermilab. The two transverse emittances can be made significantly different either by means of a special injection procedure (painting), or by cooling, or by extraction of the beam from a magnetized gun. In any case, use of the circular optics appears to open a special possibility for extremely bright beams.