Design and Operation of a High Power L-Band Multiple Beam Klystron
A 10 MW, 1.3 GHz multiple beam klystron (MBK) has been developed for the DESY X-FEL and International Linear Collider projects. The device uses six electron beams set off-axis on a large bolt circle which interact with a combination of higher-order-mode and conventional klystron cavities to efficiently produce high power RF. Extensive two and three dimensional simulations were used to design the device. Recent test results have validated the basic design concepts and procedure. Ten megawatts of peak and 150 kW of average power have been stably generated with 59% efficiency and 48 dB of gain.
A High Luminosity e+e- Collider to study the Higgs Boson
A strong candidate for the Standard Model Scalar boson, H(126), has been discovered by the Large Hadron Collider (LHC) experiments. In order to study this fundamental particle with unprecedented precision, and to perform precision tests of the closure of the Standard Model, we investigate the possibilities offered by An e+e- storage ring collider. We use a design inspired by the B-factories, taking into account the performance achieved at LEP2, and imposing a synchrotron radiation power limit of 100 MW. At the most relevant centre-of-mass energy of 240 GeV, near-constant luminosities of 10^34 cm^{-2}s^{-1} are possible in up to four collision points for a ring of 27km circumference. The achievable luminosity increases with the bending radius, and for 80km circumference, a luminosity of 5 10^34 cm^{-2}s^{-1} in four collision points appears feasible. Beamstrahlung becomes relevant at these high luminosities, leading to a design requirement of large momentum acceptance both in the accelerating system and in the optics. The larger machine could reach the top quark threshold, would yield luminosities per interaction point of 10^36 cm^{-2}s^{-1} at the Z pole (91 GeV) and 2 10^35 cm^{-2}s^{-1} at the W pair production threshold (80 GeV per beam). The energy spread is reduced in the larger ring with respect to what is was at LEP, giving confidence that beam polarization for energy calibration purposes should be available up to the W pair threshold. The capabilities in term of physics performance are outlined.
The multiple-beam klystron
The multiple-beam klystron (MBK) is a device for extending klystron power generation capability at a given frequency by a factor of ten or more. The MBK utilizes a multiplicity of electron beams in conjunction with multiwavelength waveguide circuits. These circuits are periodically loaded and operate in the\pi/2-mode. The efficiency, bandwidth, gain and stability of the MBK are equal to or better than that of the single-beam prototype klystron. Furthermore, the MBK permits generation of a given power level at an unusually low voltage, thus minimizing insulation, X-radiation, and modulator problems. An MBK utilizing ten external-circuit klystrons has been built for 750-Mc operation to demonstrate the principle of the device. A single main magnetic circuit is used to focus all beams simultaneously. An RF power output ten times that of one klystron was measured, corresponding to an efficiency of 44 per cent. Bandwidth and gain were identical with single-beam prototype operation. Individual beam drop-out tests were made which showed no disruption of operation in case of the failure of one or more beams. Limited tests tend to confirm the conclusion that the harmonic content of an MBK can be lower than that of a single-beam klystron.