DTI - SLAC Portal

Solid State Modulators for X-Band 

Accelerators 

John Kinross-Wright 

Diversified Technologies, Inc. 

Bedford, Massachusetts 

The Power You Need www.divtecs.com

DTI X-Band Experience 

• Developed and built two completely different NLC-class 

modulator systems for DOE 

– Production ready design 

• DTI has built a number of state-of-the-art, large X-band 

transmitters for precision radar systems 

• Some transmitter packages include everything from the wall 

plug to the antenna or linac 

• DTI team is fluent with klystron, TWT, magnetron and 

gyro- devices as well as IOT and tetrodes 

– Recent pulsed transmitter projects from 150 MHz to 94 

GHz 

– Several unique new transmitter systems developed 

yearly 

– Production to suit customer needs 

– Broad technology base to support almost ANY high 

power transmitter requirement 


NLC Dual klystron system 

Nominal Specifications 

500 kV 

500 amps 

3 Microseconds 

120 Hz 

Dual X-band system shown with single 

S-band klystron (5045) installed for 

testing 


Requirements for Short Pulse Klystron Modulators 

• Technical Requirements 

– High Voltage (150 – 500 kV) 

– Medium Current (100 – 400 A per klystron) 

– Fast Risetimes (< 1 us) 

– Short Pulse (1 – 20 us) 

– Flattop / Stability ( < 0.1 / 0.01 %) 

– Repetition rate (1 - 400+ Hz) 

– One or two klystrons 

• Operational Requirements 

– Extreme Reliability 

– Power efficiency 

– Flexibility / Stability 

– Ease of Maintenance 

– Maximize Klystron Life 


Short Pulse Klystron Modulator Architectures 

DTI 500 kV-class modulators include “Hybrid”, 

transformer coupled designs as well as solidstate 

Marx bank systems 

– Hybrid designs take advantage of DTI’s unique 

capability in high voltage solid state switching as 

well as our advanced high voltage power supply 

designs 

– Marx bank systems promise the ultimate 

combination of high efficiency, compact size, and 

pulse fidelity 

“Hybrid” ~ high voltage solid-state hard switch driving a pulse transformer 


DTI Solid-State Modulators Can Meet the Challenges 

• Series of IGBTs (or FETs), configured for high blocking voltage, high conduction 

currents, very low losses, fast switching 

• Can be closed, opened arbitrarily 

• Fast high voltage, high current switch is ideal for short or long pulse systems 

• > 150 kilovolts DC 

• > 10 kA peak 

Power 

Supply 

Fast Opening Switch 

Load 

• < 3 V/kV drop 

• < 1 mA leakage 


Switch Module and Assembly 

• DTI switch built from high 

voltage, high current IGBTs 

• 5 kV, 5 kA pulse (10 kA fault) 

• Series stack has large built in 

redundancy 

• 80 KV switch assembly 

configured as 

transmission line 

• DTI builds various 

switch module types 


Hybrid Modulator - Overview 

Modulator 

I 

5µF 

80kV 

• High voltage modulator switch * 

• Energy storage capacitor 

• Pulse transformer * 

• High voltage power supply * 

• Controls and housekeeping circuitry 

* DTI has unique technologies in these areas which combine effectively 


Hybrid Modulator at SLAC 

• Designed to pulse a pair 

of X-band klystrons 

• Tested at SLAC w/ 5045 

klystron 

• Pulse flat top +/- 0.5%. 

• Rise/fall/flat-top can be 

optimized to meet pulse 

fidelity and efficiency 

requirements 


Arc Protection 

• 420 kV arc of 5045 

klystron protected by 

switch opening in ~ 1 

!sec. 

• (blue) Cathode 

voltage – collapses at 

arc. 

• (red) Cathode current 

– spikes at arc, starts 

to climb. 

• (brown) Primary 

current – switch 

opens at < 4000 A. 


Recent hybrid modulators at DTI 

– S, X, K, Ka band 

• Klystrons and magnetrons 

– 150 nanoseconds – 10 

microseconds 

– PRF to ~ 5 KHz 

– Laboratory use or portable 

– Commercial or mil 

– Air or oil insulated 

– Linacs and radars 

– Excellent pulse fidelity/stability 

and reliability in all cases 


Klystron short pulse transmitter 

Typical Specifications 

Cathode voltage < 500 kilovolts 

Pulse width < 10’s microsec 

Average power < 250 kilowatts 

Rep rate < 500 Hz 

One or two klystrons 


Transmitter Systems Integration 

DTI is prepared to deliver complete 

RF transmitter systems, including 

• Pulsed modulator 

• High voltage power supplies 

• Controls 

• RF 

– High power microwave tube 

– Waveguide 

– Driver 

– Fast protection/LLRF 

• Cooling 

– Manifolds 

– Chiller 


DTI Customer support 

• Installation 

• Training 

• Spares 

• Documentation 

• Follow up support 

• Upgrades 


Marx Bank Solid-State Modulator Systems 

• DTI has designed and built solid-state 

Marx banks for both ILC and NLC projects! 

• DOE SBIR funding 

• Both designs based on a fully modular 

design concept 

• Short pulse (500 kV-microseconds) for X- 

band klystrons 

• Long pulse (150 kV-milliseconds) for L- 

band Multiple beam klystron 


Marx Switch Configuration 

Charging 

(parallel) 

Pulsing 

(series) 

• Charging circuit (left) – 

switches are off, capacitors 

charge quickly through 

common mode chokes. 

• Pulsing Circuit (right) 

Switches are on, high 

voltage (nV 0 ) is pulsed on 

load. Pulse current does not 

flow through chokes. 

• Intermediate gate drive & 

diagnostic power provided 

by additional choke 

windings. 


Compact Marx Modulator (original concept) 

• Spiral assembly lowers 

parasitic capacitance 

• 500 kV, 250 A 

design…“desktop” size 


Short pulse Marx modules assembled into racks 

• 3x3 or 4x4 racks hold prewired 

assemblies 

• one face (below) has daisychain 

choke interconnects and 

fiber optic links 

• other face (right) has daisychain 

pulse interconnects 


Short Pulse Marx – Full Spec Pulse Shows < 200 ns risetime 

• 9-stage short pulse 

modulator test: 12.5 kV 

charge 

• 110 kV into 1125 ", 1.8 

!sec 

• Risetime < 200 ns (10- 

90%) 

• Short pulse Marx in a 

“funding hiatus”, hope to 

complete for DOE if funds 

made available 

• red: current (A) 

• blue: voltage (kV) 


Long Pulse (ILC) Marx System Assembly 

• High voltage systems tested at DTI 

• ~150 KV, 1.5 milliseconds for MBK 

• System drops into 54” x 88” x 54” oil tank 

• Size/volume ~ half of DTI solid-state hard-switched system 

• Expect to complete controls and deliver to DOE 


Summary 

• Solid State Modulators Have Been Proven 

– Over 300 Fielded Systems from DTI Alone 

– Very High Reliability in Operation 

– Demonstrated Extension of Tube Life 

• Numerous systems delivered for High Voltage, 

Short Pulse Applications 

– Linacs 

– Radar 

• Benefits 

– Improved Performance 

– Lower Operating Costs 

• Impact - Lower Life Cycle Costs 


Thanks! 

Work Supported Under DOE Grants 

DE-FG02-03ER83638 

& DE-FG02-05ER84352 

More Information: 

Diversified Technologies, Inc. 

35 Wiggins Ave 

Bedford MA 01730 

781-275-9444 

www.divtecs.com

DTI - SLAC Portal

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