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

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

P1 Marx +Toshiba 10 MW MBK Performance Kirk Bertsche

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

RF Pulse Flatness Pulse flat to within 0.5%

Modulator Power Correlations

Modulator Voltage Correlations Toshiba measured a mP of 3.16

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

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

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

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

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

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

SLAC P2 Marx Cell Schematic Time Voltage

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

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

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

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

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

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

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

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

Layout

P2 Being Assembled

P2 Nearly Assembled

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

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.

Thompson Modulator for XFEL

Thompson Modulator

DTI MARX MODULATOR Rosa Ciprian

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

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)

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

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.

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.

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

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 1.542 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”.

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.

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.

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.