Development of the RFD linac structure

The new RF-focused drift-tube (RFD) linac structure resembles a drift tube linac (DTL) structure with RF quadrupole (RFQ) focusing incorporated into each “drift tube”. As in the conventional DTL structure, these drift tubes are supported on single stems along the axis of a cylindrical cavity excited in the TM₀₁₀ RF cavity mode. Four electrodes of each drift tube couple energy from the primary cavity mode to produce RF quadrupole focusing fields along the axis of the drift tube. The RF properties of this three-dimensional structure are being studied with the aid of HFSS (3D-RF code), CHARGE-3D (3D-electrostatic code), and SUPERFISH (2D-RF code). The beam dynamics of this structure is being analyzed with the aid of a new PARMILA-like beam dynamics code, PARMIR, and TRACE-3D. The results of these studies and descriptions of our target applications are presented