<title>X-band klystron development at the Stanford Linear Accelerator Center</title>

Abstract

X-band klystrons capable of 75 MW and utilizing either solenoidal or Periodic Permanent Magnet (PPM) focusing are undergoing design, fabrication and testing at the Stanford Linear Accelerator Center (SLAC). The klystron development is part of an effort to realize components necessary for the construction of the Next Linear Collider (NLC). SLAC has completed a solenoidal-focused X-band klystron development effort to study the design and operation of tubes with beam microperveances of 1 .2. As of early 2000, nine 1.2 .tK klystrons have been tested to 50 MW at 1.5 j.ts. The first 50 MW PPM klystron, constructed in 1996, was designed with a 0.6 p.K beam at 465 kV and uses a 5-cell traveling-wave output structure. Recent testing of this tube at wider pulsewidths has reached 50 MW at 55 % efficiency, 2.4 ts and 60 Hz. A 75 MW PPM klystron prototype was constructed in 1998 and has reached the NLC design target of 75 MW at 1 .5 ps. A new 75 MW PPM klystron design, which is aimed at reducing the cost and increasing the reliability of multi-megawatt PPM klystrons, is under investigation. The tube is scheduled for testing during early 2001.

Equilibrium and confinement of bunched annular beams

“…In the previous expression, p ω is the effective plasma frequency and c ω is the electron cyclotron frequency. This parameter limit agreed well with the self-field parameters of three periodic permanent magnet (PPM) klystron experiments, i.e., 50 MW-XL PPM [6,7], 75 MW-XP [6,7] and the Klystrino [8], which are all at the Stanford Linear Accelerator Center.…”

Beam confinement in periodic permanent magnet focusing klystrons

“…The 75-MW XP is operating outside of the confinement limit. This suggests that the 75 MW klystron has greater beam loss than its 50 MW counterpart, which is consistent with more pronounced X-ray emissions measured at the output section of the device [15]. The Klystrino design parameters fall just inside of the theoretical limit, suggesting a marginally stable beam-wall interaction.…”

“…MW XP klystrons [7,15] and the W-band Klystrino [16]. The parameters for all three klystrons are listed in Table 1, and their operating points are marked with letter a, b and c in Fig.…”

Confinement of high-intensity bunched beams in high-power periodic permanent magnet focusing klystrons

“…The 75-MW XP is operating outside of the confinement limit. This suggests that the 75 MW klystron has greater beam loss than its 50 MW counterpart, which is consistent with more pronounced Xray emissions measured at the output section of the device [9]. The Klystrino design parameters fall just inside of the theoretical limit, suggesting a marginally stable beamwall interaction.…”

“…(6) to three recent PPM focusing klystron experiments at SLAC, namely, the X-band 50 MW XL-PPM and 75 MW XP klystrons [4,9] and the W-band Klystrino [10]. The parameters for all three klystrons are listed in Table 1, and their operating points are marked with letter a, b and c in Fig.…”