Drive Beam Generation For CLIC Based On 200 MHz SC Structures

The present note describes an RF power generation scheme for multibunch operation at 1 TeV CM and luminosity 10^34 cm^-2s^-1. - The scheme is upgraded to use acceleration with 200 MHz SC cavities (instead of 352 or 250 MHz ones, but still with 6MV/m) in order to reduce the active SC linac length, for the required stored electromagnetic energy (180 KJ/linac), and hence also reduce the capital cost of drive beam generation. Further value (7.8 10^9), due to the lowered frequency, increases the overall efficiency

Push-pull Linac pairs to generate two drive beams for CLIC multibunch operation

This note describes an RF power generation scheme for multibunch operation at 1 TeV CM and luminosity of 1034 cm2 s1. The scheme is upgraded to use acceleration with 250 MHz SC cavities (instead of 352 MHz ones) in order to have available the increased stored RF energy necessary to accelerate to 3 GeV the newly required charge of 30 µC/drive beam

Loss factor Dependence on Group Velocity in Disk-Loaded Travelling-Wave Structures

The loss factor, a quantity linked to the energy lost by a point-like charge when traversing an accelerating (or decelerating) structure, can be computed using programs which solve Maxwell's equations in time domain and provide the correct result within the limitations inherent to the numerical simulation process. An alternative method, commonly used, consists in the derivation of the loss factor from the parameter R/Q, which is computed using codes operating in frequency-domain. Recent calculations of the loss factors for disk-loaded structures performed with the two methods have produced diverging results. The discrepancy of the results is a function of the group velocity and can be eliminated by introducing a correction term in the formula linking the loss factor to the R/Q obtained from frequency-domain calculations

PETS Output Power and Drive Beam Deceleration for Finite Q-Values and Tune Errors

PETS performance degradations caused by finite Q-values and small tune errors are estimated. A simple explanation of the recently discovered group velocity enhancement of the loss factor is given

The 30 GHz transfer structure for the CLIC study

In the so-called "Two-Beam Acceleration Scheme" the energy of a drive beam is converted to rf power by means of a "Transfer Structure", which plays the role of power source. In the Transfer Structure the bunched drive beam is decelerated by the electromagnetic field which it induces and builds up by the coherent interaction of successive bunches with the chosen longitudinal mode. The CLIC Transfer Structure is original in that it operates at 30 GHz and uses teeth-like corrugations to slow down the hybrid TM mode to make it synchronous with the drive beam. The beam energy is transformed into rf power, which travels along the structure and is collected by the output couplers. The 30 GHz rf power is then transported by means of two waveguides to two main linac disk-loaded accelerating structures. This report describes the CLIC Transfer Structure design, 3-D computer simulations, model construction and measure-ments as well as the prototype construction and testing with the low energy beam in the CLIC Test Facility. The result of this development is a compact, fully passive, relatively simple and low cost device, which offers a readily scalable solution to the problem of rf power extraction from high frequency bunched beams

Design of a 3 GHz Accelerator Structure for the CLIC Test Facility (CTF 3) Drive Beam

For the CLIC two-beam scheme, a high-current, long-pulse drive beam is required for RF power generation. Taking advantage of the 3 GHz klystrons available at the LEP injector once LEP stops, a 180 MeV electron accelerator is being constructed for a nominal beam current of 3.5 A and 1.5 microsecond pulse length. The high current requires highly effective suppression of dipolar wakes. Two concepts are investigated for the accelerating structure design: the "Tapered Damped Structure" developed for the CLIC main beam, and the "Slotted Iris - Constant Aperture" structure. Both use 4 SiC loads per cell for effective higher-order mode damping. A full-size prototype of the TDS structure has been built and tested successfully at full power. A first prototype of the SICA structure is being built.Comment: Contribution to Linac 2000 Conference, TUA16 (Poster