Minutes30January2009 < SPL

---+++ DTL structure meeting 30.01.2009

S. Ramberger, R. Wegner, G. <nop>DeMichele, F. Grespan  

*DTL Power Coupler Simulations*
   * Power Coupler 3D simulations with MWS and HFSS.
   * Reduced DTL Volume simulated (7th and 8th cell).
   * Installed WaveGuide geometry (short at Lamda_guide/4 = 31 cm from the Iris centre).
   * Discussion about the method described by Balleyguier in [[http://accelconf.web.cern.ch/accelconf/l98/PAPERS/MO4037.PDF]] , using 2 Eigenmode simulations in order to calculate the Qext.
   * good agreement (< 5%) between the simulation methods:
      * MWS:
         1. "Balleyguier" method
         2. Eigenmode solver for Qext calculation
      * HFSS:
         1. "Balleyguier" method
         2. Driven Modal solver for VSWR calculation
   * Scaling the simulations to the whole DTL volume: simulation with end walls PEC, Tank and Drift-Tubes dissipative; then scaling with the cell number; finally add the end walls to the total dissipated power.
   * Check the possibility to keep the PIMS Coupler Geometry for the DTL tanks: varying 1st the Wguide short length, 2nd the coupler height, 3rd the iris dimensions.

*DTL Circuit Model*
   * the geometrical estimation of the Coupling Capacitance (between Drift-Tubes and Tank) makes sense with the frequency fitting (within a factor 2).
   * the Stem circuit has been included in the model and the theoretical dispersion curve fit the measurements.
   * Post Couplers: simulations show the PC field not to interact with Stems -> maybe the PC circuit can avoid the Stems.
   * results of a circuit without coupling between PCs: dispersion curve fit the 1st and the 2nd frequency, but not the next.
   * look at the fields and currents of the 3D simulation to understand the Coupling between PC (inductance? Mutual inductance? Both?).
   * simulations with different number of PCs per cell, different Drift-Tube length, etc:
      * How does the PC's Dispersion Curve vary?
      * How does the effect of the PC vary on the axis?
      * Is it possible to define a "Number_of_PC/meter" in case of different Drift-Tubes Length?

*DTL RF Power Test*
   * Directivity of the directional coupler is fundamental to know, in order to correctly distinguish P_forward and P_reflected. 

-- Main.FrancescoGrespan - 04 Feb 2009
This topic: SPL > WebHome > Linac4Web > RFStructureMeetings > Minutes30January2009
Topic revision: r1 - 2009-02-05 - SuitbertRamberger