high efficiency x-band klystrons development at cern · 2019. 2. 8. · clic ws, january 2019, cern...
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I. Syratchev, J. CaiCLIC WS, January 2019, CERN
High efficiency X-band klystrons development at CERN
Igor Syratchev and Jinchi Cai, CERN
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
The new klystron bunching technologies have been established and evaluated. The computer code KlyC/2D and special scaling procedures have been developed and implemented. A number of high efficiency klystrons has been designed and few were communicated to industry.
High efficiency klystron development at CERN
S-band/IndustryCPI50 MW
X-Canon6 MW
X-CLIC8 MW
X-CLIC50 MW
L-FCC1.3 MW UHF-LHC
0.4 MW
X-CanonPPM, 50 MW
L-MBK ILC10 MW
L-MBK CLIC20 MW
UHF-LHC0.3 MW
Designed at CERN
Industrial tubes for science
S-Canon6 MW
X-BVERI50 MW
High Efficiency industrial prototypes
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
As of 01.11.2018
6 MW X-band klystron available from industry
Operates at repetition rate of 400 Hz
E37113
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
Objectives of the 6 MW klystron retrofit development at CERN.
Design of the COM klystron with improved (60%+) efficiency, thus increasing the peak power from 6 MW to 8-9 MW without modifications of the modulator and the tube cathode (fixed perveance).
Development of new computer tool (KlyC module) capable of the fast and reliable optimisation of the multi-gap output RF circuit.
Establishment of the complete compute simulation cycle (A-Z) including gun, solenoid and collector using PIC code CST/3D.
Deign of the new RF window (TW in ceramic) with higher RF power capacity than in existing device.
Providing the company with details of design study and fabrication of the prototype.
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
The 8MW X-band klystron design sequence flowchart.
1. KlyC 1D optimisation with artificial single cell output cavity (73%)
2. KlyC 2D with artificial output cavity (67%)
3. KlyC 2D The multi-cell output coupler (60.8%)
Optimal coupler topology choice: 4 cells
4. KlyC 2D full tube optimisation with additional gain cavity (62.8%, Pin=80W)
CST/3D benchmark, 60.5%Excessive E surf. (100 MV/m)
5. Output coupler re-optimisation, E surf. ~70MV/m, 60.8% (CST, 58%)
6. Solenoidal field optimisation to avoid the beam interception: 0.38T (KlyC:60.2%;CST 59.8%)
RF circuit design summary
Pin=800W
7. Solenoid design (CST). Scaled from existing Canon magnet.
8. Collector design. CST TRK. P <150 kW/cm2 in diode mode.
9. CST PIC simulations of the tube + solenoid + collector (59%)
10. Original Canon cathode + bucking coil + solenoid tuning in CST.
11. Technical design of the single feed input/output couplers and RF cavities.
12. Final KlyC 2D optimisation with beam parameters imported from CST gun simulation (59.5%)
13. Full (A-Z) tube simulation in CST (58.1%)
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
12. Final KlyC 2D optimisation with beam parameters imported from CST gun simulation (59.5%)
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
100W 8MW
15
4kV
,90
A
Eff.=58.1%
Bz field imported from solenoid system
Emax=80MV/m
13. Full (A-Z) tube simulation in CST (58.1%)
22 millions mesh cells2 millions particles in simulated volume
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
60MHz at-1dB
KlyC2D
The tube performance summary
KlyC2D
KlyC2D KlyC2D vs. CST 3D
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
E37113 tube window Compact (32 mm long) window with travelling wave in ceramic
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
As of 01.11.2018
50 MW X-band klystrons available from industry
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
Frequency
Peak power
Repetition rate
Pulse width
Power Gain
Efficiency
-3dB bandwidth
Beam voltage
beam current
Focusing
11.424GHz
50.4MW
10Hz
1.5μs
50.9dB
60.4%
36MHz
446kV
187A
Solenoid
The first HE (60%) commercial prototype of the 50 MW COM X-band klystron.BVERI, Beijing, China
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
53 MW X-band klystron design activity at CERN.
Parameter Target value
Frequency, GHz 11.994
Voltage, kV 400
Current, A 190
Perveance, µAV-3/2 0.75
Efficiency, % ~70
Power, MW 53
Surface E field, MV/m ≤ 100
Pulse length, ns 2000
Power gain, dB > 55
Cathode loading, A/cm2 < 5
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
Multi-cell klystron output circuit simulation. New module in KlyC.
1. Introduce cell by cell the geometries of the individual cells into KlyC EM module. Specify their frequencies and loaded Q-factor of the coupler cell. The arbitrary coupler topology (tapered aperture and/or cells length) is supported.
- KlyC will simulate the eigen-fields and eigen-frequencies for each cell.- Calculate the coupling matrix and generate eigen-field and complex eigen-
frequencies of entire geometry.
2. Use the idealized bunched beam (internal KlyC option) as a power source. Specify bunch frequency, length and congregation (normalised amplitude of the intra- bunch velocity spread).3. Optimise the coupler’s individual cells frequencies using KlyC optimiser (and/or manually)
4. ‘Glue’ the bunching circuit and proceed with optimisation of the entire tube.
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
The coupler performance optimised by KlyCCoupler topology: constant aperture/impedance 6 cells structure with ‘long’ last coupler cell.
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
The coupler performance benchmark with CST/3D
In this comparison, the idealized bunches parameters are identical for both codes.
E max ~ 100 MV/m
Bunch length /3, monochromatic bunch
Bunch length /3, bunch congregation 0.25‘cold’ measurements
‘frozen’ beam, congregated bunches
Eff. = 74% at 11.994 GHz
Eff. = 73.% at 11.994 GHz
Bz=0.38T, congregated bunches
No beam interception
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
First design option with 8 cavities circuit optimised in KlyC.
Output circuit zoom in
Output circuit with ideal bunch
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
430 KV, 190A cathode design
A. Krasnykh J. Neilson
CERN-SLAC collaboration on the 50 MW HEX tube
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
The 50 MW HEX klystron progress summary
90 MHz at -1dB
Parameter Target value
KlyC/2D
Frequency, GHz 11.994 11.994
Voltage, kV 400 400
Current, A 190 190
Perveance, µAV-3/2 0.75 0.75
Efficiency, % ~70 70.2
Power, MW 53 53.4
Surface E field, MV/m ≤ 100 <100
Pulse length, ns 2000 2000
Power gain, dB > 55 58.8
Cathode loading, A/cm2 < 5 4.74
The design is not yet finalized. The perveance and/or bunching circuit topology can be modified.
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
The tube design migration to CST/3D.
Coming next
• Coupler post optimisation in CST. The direct interface between KlyC and CST is developed and tested. It allows for the local and fast optimisation in CST using the bunched beam information from KlyC.
• Gun simulation in CST and final tube optimisation in KlyC.• Collector design• Full tube simulation in CST.
The full design shall be completed in three month (by March 2019). Start looking for the partners for the prototype fabrication, anticipating the first
testing at the end of 2020. Optimised design and fabrication of HTSC solenoid (0.38T; 320 K?) for HEX
klystron (end of 2020).
Complimentary studies (CST/3D) of PPM and reversed PM focusing solenoids options for 8MW and 50MW HEX tubes.
I. Syratchev, J. CaiCLIC WS, January 2019, CERN
http://cds.cern.ch/record/2649486/files/
…Converts the klystron design work into a pleasant journey…
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