Multi-cell RF deflecting system for formation of hollow high energy heavy ion beam

Terra Watt Accumulator project (ITEP-TWAC) aims for accumulation of an intense ion beam, up to 10¹² ppp and accelerated up to 0.7 GeV/u, in a storage ring for experiments on heavy ion beam-plasma interaction. For advanced experiments on high energy density physics the hollow cylindrical target is needed. A new method for RF rotation of the ion beam is applied for reliable formation of the hollow cylindrical beam. A principle of fast beam rotation by using a system of the multi-cell RF deflectors is considered in this paper. A four-cell H-mode deflecting cavity operating at the frequency of 297 MHz has been developed; similar 1.5 m long cavities being applied for both x- and y- directions. The shape of the deflecting electrodes has been optimized in order to provide the uniform deflection over the whole aperture taking into account both electric and magnetic components of the RF field. A deflecting system and a focusing quadrupole triplet applied to the beam with the energy of 450 MeV/u and normalized transverse emittance of 10^*pi mrad^*mm may form the quasi-hollow configuration with the inner radius up to 1.5 mm and thickness of 1 mm.