Minutes of the CLIC Meeting - 9 May 2003

1. To find out how to choose the klystron parameters to get the highest possible efficiency under ideal conditions, a 6-disc model spreadsheet was developed using MathCAD, which is very quickly to optimise the parameters in the output cavity and get the results in several seconds. The results between MAFIA and 6-disc model are compared and the efficiency errors are with 0.5dB using the same calculation conditions. The effects of perveance, gap voltage, initial bunch length, velocity distribution within bunch on efficiency are investigated using the 6-disc mode.

2. To prove that the coaxial cavity is possible with reasonable efficiency using coaxial output structure, a preliminary design has been obtained from the coaxial cavity design Spreadsheet, and the output cavity simulation in 6-disc model shows an efficiency of 66%. MAFIA simulation shows an efficiency of 58% in both methods of gamma calculation and area-integral of Poynting vector; MAFIA simulation results shows losing beams will not affect the uniformity of the electric field along the ridge, just weaken the field and make the efficiency go down.

3. To find out the beam bunching dynamics, a spreadsheet for the investigation of beaming bunching in klystron has been developed using Mathcad. The results of gap voltage and gap phase of a klystron from 2D ring model have been put into the spreadsheet for investigation. Applegate diagram from the ring model and the Spreadsheet look similar, the efficiencies agree well in low input power and low focusing field. Using the spreadsheet, a new bunching method is put forward and modelled, which is to injected a harmonic frequency or together with fundamental frequency into the input cavity.

copy of his transparencies (pdf format)