2 nd Harmonic cavity meeting March 2 2017 Gennady Romanov On PA test set up one more time 2III2017 Gennady RomanovMechanical 3D model transferred into CST 2 CST tetrode model based on measurements built in PA test set up model ID: 545256
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Slide1
Mechanical 3D model transferred into CST .
2nd Harmonic cavity meetingMarch 2, 2017
Gennady RomanovSlide2
On PA test set up one more time2/III-2017
Gennady Romanov|Mechanical 3D model transferred into CST2CST tetrode model based on measurements built in PA test set up model.Result of CST: f = 70.016 MHz, while the test data is 71.6 MHz All possible incorrectness in the PA model were fixed, the water load added. Result of CST: f = 70.6
MHz.
Anode-grid gap in the tetrode was increased by 0.508 mm (0.02”). Result of simulations: f = 71.648 MHz (≈ 1 MHz rise)
The anode-gap was increased by 0.508 mm in the 2
nd
harmonic cavity model. Results of FD simulations with uniform µ show weak impact of this change:
µ
Old
gapNew gapf high end, MHz1.3834104.05104.11f low end, MHz3.20875.86275.873
Abs electric field distribution in logarithmic scale
PA set up model
2
nd
harmonic cavity model
Frequency of the PA set up is defined mostly by the tetrode itself, because highest electric field is in the anode-grid gap. On the contrary in the 2nd harmonic assembly almost all electric energy is stored in the cavity. Therefore a sensitivity of frequency to the tetrode dimensions is very low (operating mode is assumed)Slide3
Mechanical solid model2/III-2017Gennady Romanov|Mechanical 3D model transferred into CST
3Kevin’s model from February 10, 2017
This position and orientation of the coordinates requires translation and rotation of the imported parts. Any part movement is a numerical operation with finite accuracy. To avoid possible errors during these manipulations, let’s define a common point of coordinate origin. Since this is an accelerator cavity, a natural choice is the accelerating gap.
Sharp edge and gap
Cooling tube goes through RF volume
A very complicated shape. How it is supposed to be built?Slide4
RF 3D model, first shot.2/III-2017
Gennady Romanov|Mechanical 3D model transferred into CST4EM, uniform µ = 1.3834 (corresponds to 575 A coil current), f = 101.4 MHz, ≈ 3 MHz down (from 104.11 MHz) because of this gap
Gap ≈ 0.01”
The parts of this color had to be made from scratch because:
1) Meshing of some CAD parts failed.
2) Meshing of the imported CST part failed either.
Tuning curve after the gap was closed. It is good, slightly reduced.
Surface currents on the gap edge
and on the end plate
Bolts, nuts and non-RF details removedSlide5
More about gaps2/III-2017Gennady Romanov|Mechanical 3D model transferred into CST
5
Surface electric field
outside RF volume
Temporary unrealistic solution
This gap may be closed, if we want a solid flangeSlide6
2/III-2017Gennady Romanov|Mechanical 3D model transferred into CST
6Fields and surface currents on slotsE_surf
General view of
E_surf
, field is
not normalized to V=100 kV
Surface current,
absolute
value
Narrow slots are not a concern. 100%≈130%Slide7
Garnet/ceramic at slots2/III-2017Gennady Romanov|Mechanical 3D model transferred into CST
7
Field enhancement on the wide slot
No noticeable field enhancement on the narrow slotSlide8
2/III-2017Gennady Romanov|Mechanical 3D model transferred into CST8
Garnet-ceramic connectionsAlumina
Garnet
E_surf
Copper
≈130%
Triple point is a singularity, so
the error of simulations may be very big. Therefore we can say for sure that surface field is enhanced there, but we don’t know how much.