i. syratchev, clic breakdown workshop, cern, 20 may 2008 power circulation in a clic accelerating...
DESCRIPTION
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008 I. Syratchev, LC99, April 1999 From PETS, A1 Structure Output, A2 Structure Input, A3 To RF Load, A4 Variable polarized power divider basics Circular waveguide with H11 mode beam RF For any azimuthal position, the structure RF input phase remains constant. ! The RF power divider/combiner is a key element of the scheme. It can be build in a different ways (classical planar hybrid for example). However it is very useful to have the design which provide certain tuning capability of the system:TRANSCRIPT
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008
Power Circulation in a CLIC Accelerating
Structure
I. Syratchev
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008
Motivations
The re-cycling of RF power in a Traveling Wave structure can potentially allow for increase of the RF-to-beam efficiency. Compared to the conventional TW, in this regime, there is no power dissipated in RF load during steady state operation.The beam loading compensation comes naturally for this scheme. With application of the tunable element in a feedback loop it is possible to terminate the power delivery into the accelerating structure (alternative to the Petsonov)
PETSLoad
Ohmic Losses
beam
LoadPETS
Ohmic Losses
beam
Traveling wave
Traveling wavewith re-circulation
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008
I. Syratchev, LC99, April 1999
FromPETS, A1
StructureOutput, A2
StructureInput, A3 To RF
Load, A4
Variable polarized power divider basics
Circular waveguidewith H11 mode
beam
RF
For any azimuthal position, the structure RF input phase remains constant.!
The RF power divider/combiner is a key element of the scheme. It can be build in a different ways (classical planar hybrid for example). However it is very useful to have the design which provide certain tuning capability of the system:
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008
from the PETS
from the structureoutput
to the structureinput
to the load
4 –way splitter/combiner
Dual polarization multi-moded bend
Tunable polarizer section
No beam
No beam
Regime #2
Regime #1
Regime #1
Regime #2
In the case of breakdown in a first cell (missing energy 50%)
No beam
T brT br
Re-circulation optimised for the CLIC-G accelerating structure; RF/beam gain in efficiency: 12.1%PETS peak power reduction: 15.8%
Depending on the polarizer azimuthal orientation, the different regimes of operation can be realized: # 0. No recirculation (α=0) # 1. Optimal with recirculation # 2. Off mode (no power delivered to the structure)
Pure TW
Pow
er, n
or.
Pow
er, n
or.
Pow
er, n
or.
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008
Discussion
The first exercise with re-circulation optimised for the present CLIC accelerating structure (CLIC-G) showed quite a potential: the RF-to-beam efficiency can be increased by ~ 12% (from 27.7% to 31 %) The same time, PETS peak power reduction by ~ 16% will also bring a number of advantages.Following certain self-protection mechanism in the structure during RF breakdown, one can expect, that it will be exposed to the less damage. The development of the “simple”, electrically controlled high RF power phase shifter can significantly increase the flexibility and value of the system.
I. Syratchev, CLIC Breakdown Workshop, CERN, 20 May 2008
Modified recycling arm RF design (11.424 GHz)
PETS
Load
4-ports polarized combiner/splitter
Tunable polarizer section
beam
H11 circular waveguide
11 11.2 11.4 11.6 11.860
50
40
30
20
10
0 F0
Horizontalpolarization
Verticalpolarization
Verticalpolarization
Horizontalpolarization
Frequency, GHz
S11,
dB
Horizontal + Verticalpolarizations
Rotating H11