Michael Read Calabazas Creek Research Presented at CERN Aug 30 2013 mikecalcreekcom PPM Focusing Eliminates large magnet power supplies Reduces operating and capital costs Conventional klystron magnet power supplies can consume more than 4 of average power of klystron ID: 784543
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Slide1
PPM Focusing in Klystrons
Michael Read
Calabazas Creek Research
Presented at CERN Aug 30, 2013
mike@calcreek.com
Slide2PPM Focusing
Eliminates large magnet power supplies
Reduces operating and capital costs
Conventional klystron magnet power supplies can consume more than 4% of average power of klystron
Fields larger than
Brillouin
can be used
CCR designs have RMS fields ~ 1.5 x
Brillouin
Requires careful shaping of field in electron gun
Defocusing near output cavity can be avoided using “quasi-
solenoidal
” magnets
CCR approach with pillbox magnets
Simple access for cavity cooling
Variability in magnet strength is averaged out
Slide3CCR PPM Focused Klystron
Slide4PPM Structure
Variation in field around beam circumference < 0.05%
Slide5Slide6CCR PPM Klystrons
10 kW S-Band (in fabrication)
1 A, 20 kV, 55%, 0.35 µ
pervs
Efficiency limited by beam interception
572 kW, 1.3 G
11A @ 80 kV, 65%, 0.5 micro µ
pervs
75 MW L-Band (in initial design phase)379 A, 440 kV, 48.5%, perv 1.3 µ5 MW S-Band (beginning fabrication) 90.5 A, 127 kV, 48.3%, 2 µpervs
Slide7Design Codes
RF Structure
SuperFish
(LANL code for 2D RF structures)
KLSC (in house klystron code)
TESLA (NRL klystron code)
HFSS (commercial code for 3D elements)
PPM StructurePandira
(2D) (LANL magnetics code)Maxwell 2D/3D (ANSYS magnetics code)Electron gun/beamEGUN, TRAK (commercial 2D beam trajectory codesBOA (CCR 3D trajectory/magnetics/thermal code)TESLA (2D beam in klystron fields)
Slide8EGUN Simulation of PPM Klystron Beam
2D Simulation
Slide9BOA Simulation of PPM Klystron Beam
3
D Simulation
Slide10TESLA Modeling of PPM Klystron
Slide11Off-Axis Focusing
Off axis beam focusing requires only symmetry around beam axis
Initial modeling shows very good symmetry
Slide12Geometry with off axis beams(single period)
Slide13Mag B
On Axis (standard PPM focusing)
Off Axis
Slide14Bz
On Axis
Off Axis
Slide15Bx (Br)
On Axis
Off Axis
Slide16Initial Simulation of Off-Axis Beam
BOA simulation 20 kV, 1 A
Slide17Summary
PPM focusing can be used in high efficiency klystrons
Off axis focusing for multiple beam focusing should be as effective as in single beam devices
Slide18CCR MBK’s
DOE
100 kW X-Band (fabricated)
15 beams
perveance 4.5 micropervs (
17.6
A @
25 kV) 150 kW wide band C-Band (in design)18 beams
Perveance 5.5 micropervs (21.6 A @ 25 kV)
Slide19Mag scale factor 0.7
0.8
0.6