Design of a Converging Elliptic Gun for Elliptic-Beam Klystron Applications

There is a need to develop high-efficiency, high-power klystrons capable of operating at peak power levels on the order of 300 kW to 10 MW for a TeV-class linear collider. At present, conventional circular-beam klystrons are used to drive accelerators for physics research applications. However, they are inefficient for low-voltage operation. Sheet or elliptic beam technology makes it possible to operate high-power devices at low beam voltages and higher efficiency. Sheet or elliptic beam klystrons (SBKs or EBKs) will substantially lower the construction and operating cost of a TeV-class linear collider. In particular, an alternative approach of using a low-voltage 300 kW EBK to drive a single 9-cell rf cavity will eliminate the need for a second tunnel, and a 10 MW EBK will be less expensive and more efficient than a 10 MW multi-beam klystron (MBK). In the development of sheet- or elliptic-beam klystrons, much progess has been made recently. However, one of the remaining challenges is to design a high-brightness, high-power converging elliptic gun. This SBIR project aims to design a converging elliptic gun for elliptic-beam klystron applications, based on techniques recently developed at Beam Power Technology (BPT) for creating uniform density, high brightness elliptic charged-particle beams. The Phase I technical objectives are: (1)Theoretical modeling of converging elliptic guns for elliptic-beam klystrons; (2) Development of a core simulation module for converging elliptic guns; (3) Benchmark of the proposed core simulation module against existing gun designs; and (4) Concept design of a converging elliptic gun for 300 kW and 10 MW L-band klystrons. In Phase II, BPT will develop the detailed gun design, mechanical engineering, fabrication and experimental demonstration of the converging elliptic gun for a 300 kW or 10 MW high-efficiency elliptic-beam klystron. Commercial Applications and Other Benefits: If successful, the proposed design will facilitate the development of high-efficiency, high-power elliptic-beam klystrons. As a more efficient, lower-voltage device, elliptic beam klystrons could replace conventional klystrons in new installations or upgrades for applications across a wide range of power and frequency levels. The market size of klystrons is about $200M/year worldwide. The annual worldwide sales of BPT