Periodic permanent magnet development for linear collider X-band klystrons

Abstract

The Stanford Linear Accelerator Center (SLAC) klystron group is currently designing, fabricating and testing 11.424 GHz klystrons with peak output powers from 50 to 75 MW at 1 to 2 µs rf pulsewidths as part of an effort to realize components necessary for the construction of the Next Linear Collider (NLC). In order to eliminate the projected operational-year energy bill for klystron solenoids, Periodic Permanent Magnet (PPM) focusing has been employed on our latest X-band klystron designs. A PPM beam tester has operated at the same repetition rate, voltage and average beam power required for a 75 MW NLC klystron. Prototype 50 and 75 MW PPM klystrons were built and tested during 1996 and 1997 which operate from 50 to 70 MW at efficiencies greater than 55 %. Construction and testing of 75 MW research klystrons will continue while the design and reliability is perfected. This paper will discuss the design of these PPM klystrons and the results of testing to date along with future plans for the development of a low-cost Design for Manufacture (DFM) 75 MW klystron and invitation for industry participation.

Electron beam halo formation in high-power periodic permanent magnet focusing klystron amplifiers

“…4 To summarize the results of this section briefly, we find from self-consistent simulations and detailed phase space analysis that in the absence of RF signal, the equilibrium beam transport in the PPM focusing klystron is robust and no beam loss is expected. These results are in good agreement with the experimental observation [10] of 99.9% beam transmission in the absence of RF signal.…”

“…In this section, we discuss important properties of the equilibrium beam transport, and present results of our analysis and self-consistent simulations of periodically focused intense electron beam equilibria for choices of system parameters corresponding to those used in the SLAC 50 MW, 11.4 GHz PPM focusing klystron experiment [10].…”

“…(4) and (5) We analyze the beam envelope for equilibrium beam transport in the SLAC 50 MW, 11.4 GHz PPM focusing klystron experiment [10]. The system parameters of the experiment are shown in Table 1.…”

“…Detailed simulation results are presented for choices of system parameters corresponding to the 50 MW, 11.4 GHz periodic permanent magnet (PPM) focusing klystron experiment [10] performed at the Stanford Linear Accelerator Center (SLAC). It is found from the self-consistent simulations that sizable halos appear after the beam envelope undergoes several oscillations, and that the residual magnetic field at the cathode plays an important role in delaying the halo formation process.…”

Latest Results in SLAC 75 MW PPM Klystrons

“…The fourth of these 50 MW designs [3], the XL4, has been the rf source of choice for X-band component and accelerator development for the last 7 years. At approximately the same time the XL4 was undergoing testing, the first 50 MW PPM klystron [4] was designed and tested. This first PPM klystron, the 50XP, met and exceeded the target specifications and operated at 50 MW at 2.82 μs for approximately 1000 hours.…”