1. Toshiba 10 MW Multi-Beam Klystron (MBK)
Marx Modulators
RF Controls
P1 Marx
10 MW Klystron
P1 Marx: has operated over 5 khr although at half pulse length this year due to capacitor lifetime problem
P2 Marx: has lower voltage cells with individual droop control – nearly assembled
In FY12, no funding for new development, but
P1 and P2 will be long-term tested
A SBIR funded DTI Marx will be delivered to SLAC
A new 10 MW MBK has been purchased
Toshiba 10 MW Multi-Beam Klystron (MBK)
Chris Adolphsen

2. ILC Klystron Modulator
Performance requirements
120 kV peak voltage
140 A peak current
1.6 ms pulse width
5 Hz pulse repetition frequency
+/- 0.5% flat top
134 kW average power
< 20 J deposited into klystron from gun arc

3. P1 Marx +Toshiba 10 MW MBK Performance
Kirk Bertsche

4. Operation History 750 ms Pulse Length 10 Months: Nov 2010 thru Aug 2011

5. RF Pulse Flatness
Pulse flat to within 0.5%

6. Modulator Power Correlations

7. Modulator Voltage Correlations
Toshiba measured a mP of 3.16

8. Marx P1 System Faults 31 Total Faults Nov 2010 thru Aug 2011
Majority of faults due to facilities interlocks (e.g. waveguide pressure, cooling water flow)
One modulator problem, June 2011
Arc on backplane, induced by corona
Corona prevention measures taken on new backplane
No recurrence of problem

9. Problems Encountered
Shorter capacitor lifetime than advertized – related to the discharge level – plan to replace Al coated polyethylene caps with Zinc coated ones next month
Backplane arcs and corona – fixed by using nylon screws and removing air gaps
Reduction of MBK gain after power outage – second or third cavity may have been detuned – investigation underway

10. P2 Marx Design Considerations
Compatibility with two-tunnel design
High availability
Low-cost
Ease of maintenance
Portability of design to future applications

11. Modulator Topology High Availability Low Cost Portability of Design
Each cell provides a regulated output
Modulator has N+2 redundancy
Low Cost
Marx is inherently modular. Large quantities allow for an economy of scale
Portability of Design
PEBB approach to allow cells (building blocks) to be arranged differently for different output requirements

12. RF System Overview DC 4.2kV DC DC DC Marx Modulator 3phase 480V pulsed
out
1.2kV DC
DC Power Supply Rack
Klystron
32 Cells

13. Marx Basics Classic description: +Vin Marx “cell” Charge in Charge out
SLAC P2 Marx Solid
State Implementation:
Cell in
Cell out

14. SLAC P2 Marx Cell Schematic
Time
Voltage

15. Correction Scheme Cell Output Current Cell Output Voltage
Main IGBT Vce
PWM Inductor Current

16. Ripple Cancelation 2 cells switching 2 cells switching in phase
180o out of phase
2 cells switching in phase

17. Switching
High availability -> To simplify control, improve protection, and enhance diagnostic access, the Marx cells do not contain arrays of switches
No need to push the device state-of-the-art with this application. Operation is “within the datasheet”
6.5kV IGBT
half-bridge
1.7kV IGBT half-bridge
6.5kV dual diode module
Common
heat sink

18. Switching
Switch (and cell) first level protection is accomplished at the gate drive level
Over voltage, over current, over di/dt
At left, load arc is triggered at (a). Current rises through IGBT.
After fault is detected, gate drive initiates turn-off.
Active voltage clamping is achieved by partially turning device back on, (b).
(a)
(b)
IGBT Ic
IGBT Vce
IGBT Vge
140 A
4 kV

19. Controls High Availability Portability of design
System has abundant real-time diagnostic access
Prognostics built into software
Auto-reconfiguration possible
Portability of design
Controls hardware used on several projects
High-level applications have potential use in several areas

20. Modulator Control System
Application
Manager
Cell 1 Hardware
GD1
GD2
GD3
GD4
Cell 2 Hardware
Cell 32 Hardware
Gigabit Ethernet + fiber optic trigger

21. Control System Twelve 12-bit, 1 MS/s ADCs per cell
4 voltage monitors, 1-2 LEMs, 2 shunts, 3 temperature monitors, 1 spare
Potential future addition of four 8-bit, 10 MS/s ADCs per gate drive
Vge, Vce, Ic, Vce,sat
System-level monitoring
Includes output voltage, current, system temperatures

22. Packaging Ease of maintenance Portability of design Oil-free design!
Easy to get in and get out (low MTTR)
Cells less than 50 lbs
All cell parts easy to access
Maintenance is at the shop, not at the modulator
Portability of design
Cells designed to be easily scalable

23. Layout

24. P2 Being Assembled

25. P2 Nearly Assembled

26. Shown are initial results with 17 cells at 3kV each
Shown are initial results with 17 cells at 3kV each. Full voltage anticipated by January 20.
+/- 0.2% bands
Eventually, flat top anticipated to be <0.1%
ADC resolution is ~100V

27. Parameters Parameter Value Note AC to DC bus efficiency ~85%
Commercial power supply
DC bus to pulse output efficiency
>95%
Calculated
Modulator flattop
+/-0.2%
Achieved, 17/32 cells
+/-0.1%
Anticipated
Voltage output repeatability
<+/-0.1%
For AC to DC conversion, a COTS supply was used. Increased development on this component may raise the efficiency.
DC to pulse efficiency has been measured at the cell level, but an accurate measurement requires the whole system.
Voltage repeatability will be controlled by closed-loop feedback on the output voltage divider of the Marx.
Many lower limits will likely depend upon pulse to pulse repeatability of the klystron perveance.

28. Thompson Modulator for XFEL

29. Thompson Modulator

30. DTI MARX MODULATOR
Rosa Ciprian

31. ARCHITECTURE High energy Recharge via switch Dual cell approach:
core = 6.5kV
corrector = 900V
Minimize overall size and possibly $ by using electrolytic capacitors
Pulse shaping via feedback D1 D2
Recharge
Pulse

32. CORE MODULES 6.5 kV cell 8.2 kJ electrolytic capacitors
4 switches for pulsing and 4 for recharging
All 20 modules fired simultaneously, (D1 is not needed)

33. CORRECTOR MODULES 900 V cell 340 J caps
MOSFETs for pulsing and recharging
Modules fire for droop remediation (feedback)

34. ASSEMBLY Modulator tank footprint ~1.5m x 2.5m
Height ~ 2 m including controls (doghouse)
Local controls in front panel and remote in the rear panel.

35. Full Voltage/Current/PW Spec
120kV
Current:
130A
Pulse width:
1.5ms
Ch4: Command
Ch1: Pulse current 40A/V
Ch2: Voltage 15kV/V
Ch3: Feedback integrated control
Modulator has demonstrated full spec single pulsing into a resistive load.
Due to source and load limitations, full spec pulsing has been demonstrated at 5Hz with a double full PW pulse, three 1ms pulses and ten 150 us pulses.

36. VOLTAGE REGULATION
User controls voltage regulation set point with front panel controls.
User needs to adjust core and corrector voltages (buck regulators) to the pulse requirement.
Scope shot shows ability to control the regulation point (blue cursor).
Green trace indicates sequencing of pulse correction

37. CONTROLS AND FAULTS
Controls provide protection from over-current, tank over-heating, control power problems and invalid command requests.
A main interlock controls chopper power supplies, HV dump relays and is in series with an external user interlock.
Max rep rate: the limit is set at 5.1 Hz, after that limit it starts skipping pulses.
Max pulse width: at ms, if commanded a wider pulse, the pulse gets cut to the limit.
Both these faults do not produce a hard fault, and pulsing continues by skipping pulses to adjust to max rep rate or cutting the pulse width. The error will show up just as a flashing light in the front panel “pulse error”.

38. REMOTE CONTROLS
Support of complete remote controls suitable for a PLC interface
Uses TTL level signals as well as analog signals
Signals available for monitoring output parameters, run status, and faults available in the rear panel.

39. QUALIFICATION Performed by SLAC @ DTI Aug 22-26.
With and without correction at 120kV, 136A, 1.54mS. Experiments were performed with just 15 correctors.
The load DTI had was about 910Ω which ask for more current than the original requirement of 120kV/120A.
Output cable length: The output cable was about 20ft, emulating a longer cable required installation of a 700pf 150kV capacitor, that was added to the resistive load. No significant change at the output.
Regulation: The regulation feedback seems to be appropriate.
Calibration of the correctors was performed.
Because of the source and load limitations full rep rate cannot be tested at DTI.
Two pulses regulated at 120kV/130A, 1.5mS/5Hz, where the supply is still recharging the caps, we could see a small degradation on the second pulse due to lack of supply power. Also three pulses at 120kV/130V 1mS 5Hz and10 pulses 120kV/130A 150uS 5Hz.
Arc testing: Using a spark gap at 120kV/130A with regulation. After arc we validated that all modules were firing as required, and the modulator was firing full specs pulses.

40. DELIVERY AND INSTALLATION
The modulator will be shipped dry. It will be delivered with a 10m output cable DS2077 (un-terminated at klystron end) and a 10m input cable RG8 (un-terminated at the supply end).
One assembled core and one corrector together with available spare parts will be part of the delivery. DTI is working on the inventory of spares.
INSTALLATION REQUIREMENTS
10GPM cooling water, manifolds and water interlocks.
208VAC 3phase (30A breaker) for controls.
7-10kV rectified unregulated supply for main power.
Oil: ~734 gallons Diala or mineral oil.
Analysis of seismic compliance.
Secondary oil containment.