The Design of the Orthogonal Box Cavity

The muon collider and/or the neutrino factory require large accelerating electric field gradients immersed in large (3 to 6 T) solenoidal magnetic fields for ionization cooling of muon beams. Our original vacuum breakdown study demonstrated a loss of achievable peak accelerating gradient in solenoidal magnetic fields by a factor 2 or greater. The Muon Collaboration has developed a theory of a method to suppress high electric field breakdown in vacuum cavities needed for a Muon collider or neutrino factory. It has been shown in our studies and by others that high gradient electric field emitted electrons (dark current) are the primary cause of breakdown. A DC magnetic field orthogonal to the RF electric accelerating field prevents dark current high field emitted electrons from traveling across the accelerating gap and then will prevent breakdown. We have decided to test this theory by building a special cavity in the shape of vacuum box. Figure 1 is a simplified view of the cavity design. The design is based on an 805 MHz WR975 waveguide cavity resonating in the TE{sub 101} mode. For the TE{sub 101} mode the resonant frequency f{sub 0} is given by the relationship f{sub 0} = c[(I/a){sup 2} + (m/b){sup 2} + (n/d){sup 2}]{sup 0.5}/2 where a and d are the lengths of the base sides and b is the height of the box in MKS units and c is the velocity of light