SLAC, Menlo Park, California
Static magnetic field undulators are capable of producing quasi-monochromatic synchrotron radiation of very high brightness. However, it is not possible to quickly change the properties such as polarization of the radiation in a static undulator. It is possible to construct an undulator using microwaves instead of static magnets where the electron beam is undulated by both electric and magnetic fields of an rf wave. A major advantage with a microwave undulator is that the radiation properties can be changed very quickly. The biggest challenge in developing a microwave undulator is in keeping the rf losses low. We are designing a microwave undulator with the aim of achieving at least a tenth of the flux obtained by the BL13 static magnetic field Elliptical Polarized Undulator in the SPEAR ring. We have considered circular waveguide modes and hybrid HE11 mode in a corrugated waveguide as possible candidates for the microwave undulator. It is found that a corrugated waveguide has the lowest rf losses with a very desirable field profile. It is also possible to use this device for a linac driven FEL. Our analysis of the corrugated waveguide cavity for the rf undulator will be presented.
CERN, Geneva
KEK, Ibaraki
SLAC, Menlo Park, California
Demonstration of a gradient of 100 MV/m at a breakdown rate of 10-7 is one of the key feasibility issues of the CLIC project. A high power rf test program both at X-band (SLAC and KEK) and 30 GHz (CERN) is under way to develop accelerating structures reaching this performance. The test program includes the comparison of structures with different rf parameters, with/without wakefield damping waveguides, and different fabrication technologies namely quadrant bars and stacked disks. The design and objectives of the various X-band and 30 GHz structures are presented and their fabrication methods and status is reviewed.
SLAC, Menlo Park, California
Funding: Work supported by U.S. Department of Energy, contract DE-AC02-76SF00515 (SLAC)
Design studies on the X-Band transverse rf deflectors operating at HEM11 mode have been made for two different applications. One is for beam measurements of time-sliced emittance and slice energy spread for the upgraded LCLS project, its optimization in rf efficiency and system design are carefully considered. Another is to design an ultra-fast rf kicker in order to pick up single bunches from the bunch-train of the B-factory storage ring. The challenges are to obtain very short structure filling time with high rf group velocity and good rf efficiency with reasonable transverse shunt impedance. Its rf system will be discussed.
CERN, Geneva
SLAC, Menlo Park, California
KEK, Ibaraki
In recent years evidence has been found that the maximum sustainable gradient in an accelerating structure depends on the rf power flow through the structure. The CLIC study group consequently designed a new prototype structure for CLIC with a very low group velocity, input power and average aperture (a/λ = 0.12). The 18 cell structure has a group velocity of 2.4% at the entrance and 1% at the last cell. Several of these structures have been made in collaboration between KEK, SLAC and CERN. A total of five brazed-disk structures and two quadrant structures have been made. The high power results of some of these structures are presented. The first KEK/SLAC built structure reached an unloaded gradient in excess of 100 MV/m at a pulse length of 230 ns with a breakdown rate below 10-6. The high-power testing was done using the NLCTA facility at SLAC.