Ursula van Rienen, Universität Rostock, FB Elektrotechnik und Informationstechnik, AG Computational...

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Ursula van Rienen, Universität Rostock, FB Elektrotechnik und Informationstechnik, AG Computational Electrodynamics

Scattering Parameter Calculationfor the 2x7 Superstructure

TESLA Collaboration Meeting

INFN Frascati May 26-28, 2003

Karsten Rothemund, Dirk Hecht, Ulla van Rienen

2x7-Superstructure

7 Cell TESLA Cavity

HOM-Coupler

Input-Coupler

Images: I.Ibendorf

Radius Adapter

2x7-Superstructure

Images: I.Ibendorf

Rotation(couplers)

Shift of reference planes(MAFIA simulation has tubes on both sides)

Radius Adaptor

57 mm39 mm

f = 1.5 – 3.0 GHz:TE11co

TM01co

TE21co

f =1.54106GHz

f =2.01317GHz

f =2.55643GHz

TTF beam pipe superstructure

TE11 (deg.) TM01 TE21 (deg.)

HOM-Input-Coupler

antenna cone shape as in9 cell HOM coupler(no data available in drawing)

Geometry data taken from drawing „Formteil F“ (3 99 9177/D.001),[1]

[1] coutesy DESY

HOM-Coupler (HOM 2 + HOM 3)

HOM 2HOM 3 HOM 1

rotate

shift planes

27.4 mm27.4 mm

7 Cell TESLA Cavity

f=1.5-3.0 GHz

Plot: MWS, simulation: MAFIA, 2D, time domain

|S..|/dB

|S..|/dB |S..|/dB

Analytical Sections

Rotation between HOM-Couplers• Rotate reference frame of dipole and quadrupole modes• length of section is 0

Wave Guide (neg. and pos.)• shift reference plane of cavity• shift HOM 3 to correct position

Subsections

Subsection Port-Modes # of this typeHOM-Input-coupler 5 + 5 + 1+1 1HOM coupler 2 + 3 5 + 5 + 1 2TESLA cavity 5 + 5 2Plane shift cavity 5 + 5 4Shift of HOM 3 5 + 5 2Rotation 5 + 5 4Radius adaptor 5 + 5 2

Total number of subsections: 17Total number of modes = S-matrix dimension: 174(to be computed for each frequency point)

CSC-Computation

Calculation of overall S-matrixopen ports: beam pipe, 3x HOM-, 1x Input-coupler

1500 values computed in 1.5-3 GHz frequency range shown here: 2.46-2.58 GHz (3rd dipole passband)

481 frequency-points + interpolation

S-valuesof 7-cell cavity

|S..|/dB

Results

Coupling between HOM1 and HOM2 to beam pipe modes

downstream beam pipe

upstream beam pipe

|S..|/dB

Results

Coupling between HOM couplers

Coupling between Input-coupler and beam pipe modes

|S..|/dB

Timing S-Parameter

CST-MicrowaveStudioTM (2.4 GHz Pentium 4, 4GB RAM):• HOM-Input-Coupler:

316,160 mesh points (20 lines/lambda),5 beam pipe modes + 2 koaxial modesTotal computation time: 100 h (12 runs)

• HOM-Coupler:178,920 mesh points (20 lines/lambda),5 beampipe modes + 1 koaxial modeTotal computation time: 24 h (11 runs)

MAFIA (SUN Enterprise, 400 MHz, 4GB RAM):• TESLA 7 cell cavity:

2D-geometry (rz)31,158 mesh pointsTotal computation time: 2h + 6.5h + 6.75h

Timing CSC

CSC: platform: Mathematica 4.117 subsections 5 modes in structuredimension of matrix: 174481 frequency points, 2.46 – 2.58 GHz430 s on Pentium 3 (1 GHz, 512 MB RAM)

Summary

• S-parameter of 2x7 TESLA-Superstructure have been calculated (an open structure) with CSC• 5 modes have been considered in the structure• S-parameter of subsections were computed with

• CST-MicrowaveStudioTM (coupler sections, 3D)• MAFIA (TESLA cavity, 2D-rz-geometry)• analytically (shifting planes, rotation)

• some exemplary coupling parameters have been presented• computation times for S-parameters of subsections in order of days• additional computation times whole structure then in the order of minutes• parameter tuning (e.g. rotation angles, distances) possible

Ursula van Rienen, Universität Rostock, FB Elektrotechnik und Informationstechnik, AG Computational...

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