1. Carlos A. Martins ESS – Accelerator Division - RF Electrical Power Systems www.europeanspallationsource.se November 5 th, 2014 Klystron modulators for ESS Strategies and challenges

2. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 2` 1)- Sophisticated power electronic systems Introduction - Modulators and challenges 3)- Can disturb the electrical grid significantly (power quality) 4)- Very few specialized companies exist worldwide (most SMB’s) with limited engineering capabilities 6)- Impacts highly on the Linac availability (MTBF, MTTR) -MTBF (1 modulator) = ~ 50’000 to 70’000 hrs; -MTBF (1 klystron) = ~ 50’000 hrs; SS Long pulse (ms) modulator companies Long list (have designed & built 1 prototype) Short list (have successfully designed & built several units used in accelerators) Europe41 USA11 modulator 2)- Large footprints & Heavy equipment 1m Vertical klystron XFEL (DESY) Modulator 6.5m 2m 5)- Considerably costly -Standard low/medium voltage power supply: < 1€ / W -Klystron modulators: 2 to 3€ / W av Custom built; Mix of several disciplines in one system: -Electrical Engineering; -Power electronics; -Controls and programming; -Mechanical and thermal engineering;

3. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 3 Typical requirements & parameters from different accelerators (SS Long Pulsed klystron modulators) SNSISISXFELESSHP-SPL CLIC Pulse width (50% amplitude):1.6ms2ms1.7ms3.5ms~2.5ms 140µs Flat-top duration1.5ms2ms1.5ms3.31ms~2.2ms 135µs Precision/droop at flat-top (low freq,< 1kHz): <1%<5%<1% HF ripple at flat-top (> 1 kHz):0.1% 0.4%<0.1% <0.01% Pulse repetition rate60Hz50Hz10Hz14Hz50Hz Nominal pulse voltage140kV110kV130kV115kV 150kV Nominal pulse current70A45A150A100A50A? 160A Nominal pulse power9.8MW5MW19.5MW11.5MW5.7MW? 24MW Nominal apparent power1000kVA490kVA365kVA660kVA790kVA 190kVA Rise/fall times (99% / 1%)100µs10µs~100µs~250µs 5µs Max. energy in case of arc< 10 to 20J Max. reverse cathode voltage~10% Pulse width Rise timeFall time time Flat-top V

4. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 4 Long pulse modulator cost model and cost optimization 120 cavities (1cav./klyst.) 1 klys/ mod 2 klys/ mod 3 klys/ mod 4 Klys/ mod # klystrons120 # modulators120604030 Average power per modulator 165kVA330kVA495kVA660 kVA Cost / modulator 0.47pu0.75pu1pu (*) 1.26pu (*) Total cost of modulators 56.4pu45pu40pu37.8pu Relative cost savings (wrt 1 klys/mod) 0%20%29%33% (*) - extrapolation ESS baseline Relative cost (p.u.) Example #5 ESS modulator 330kVA

5. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 5 Introduction Klystron / IOT modulator strategy ESS experience with klystron modulators  One 180kVA modulator procured and tested with success for the CERN RF Test Stand -Contract signed: Dec. 2011; -Delivered: May 2014;  One 330kVA modulator under procurement for ESS RF Test Stand in Uppsala -Contract signed:June 2014; -Delivery expected: Dec 2015; Modulators procured or under procurement by ESS till Oct. 2014 CERN RF Test Stand ESS RF Test Stand Pulse width (50% amplitude):2.8ms3.5ms Flat-top duration2.5ms3.1ms Precision/droop at flat-top<1% HF ripple at flat-top<0.1% Pulse repetition rate20Hz14Hz Nominal pulse voltage115kV Nominal pulse current25A50A Nominal pulse power2.87MW5.75MW Nominal apparent power180kVA330kVA Rise/fall times (99% / 1%)~250µs~150µs Max. energy in case of arc<10J Max. reverse cathode voltage~10%

6. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 6 Introduction Klystron / IOT modulator strategy Is there any existing modulator suitable for ESS ? 1) – CERN RF Test Stand modulator ? One section of the RF Gallery (8x 704 MHz RF sources) -No space available for klystrons, RF distribution; -Prohibitive flicker level on the AC grid; -Flat-top droop: ~3%; -Efficiency: ~88%; -Large capacitor bank : high level of stored energy; -High cost (=0.5 p.u. x 120 = 60 p.u.); Purple: AC line current Green: Capacitor bank voltage

7. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 7 Introduction Klystron / IOT modulator strategy Is there any existing modulator suitable for ESS ? 2) – XFEL modulator ? -Do not fit in the RF Gallery; -High components count; -Large Pulse Transformer in oil tank; -Considerably costly (= 0.75 p.u. x 60 = 45 p.u.); One section of the RF Gallery (8x 704 MHz RF sources)

8. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 8 Development and procurement strategies by different labs Strategy I - in house development; - call for tender for series production on “build-to-print” basis Strategy II - call for tender for qualification of prototypes (ex: 3 units from 3 manufacturers); - call for tender for series production (ex: best 2 out of the 3 pre-qualified) Strategy III - single call for tender for the whole quantity, without defining the topology CERN – Linac4 (17 modulators / ~500 kVA) X CERN – SPL RF test stand (1 modulator / 180 kVA) X DESY – XFEL (~25 modulators / ~7.5 MVA) X RAL – ISIS (1 modulator/ ~400 kVA) X ONRL – SNS (~16 modulators/ ~16 MVA) X KEK – JPARC X

9. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 9 Development and procurement strategy for ESS modulators 1) – Strategy A (baseline)  ESS internal development of a new topology (SML – Stacked Multi-Level);  Construction and validation of a Reduced Scale prototype rated for 120 kVA (115kV / 20A, 3.5ms / 14Hz) in collaboration with Lund University (LTH). Can power one 704MHz 1.2MWpk klystron;  Project has started in June 2013. Completion and demonstration of technology are foreseen for summer 2015;  Upgrade to the full scale system 660kVA (115kV / 100A, 3.5ms / 14Hz) is a matter of thermal re-design and selection of higher current components. The full scale modulator is able to power 4x 704MHz 1.2MWpk klystrons in parallel. Straightforward approach with low risks;

10. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 10 Development and procurement strategy for ESS modulators 2) – Strategy B  ESS has launched an Invitation To Tender for the design and construction of one 330kVA modulator : -Contract awarded to Ampegon on June 2014; -Technical Design Report under review; -Delivery foreseen for Jan 2016; -Soak testing in Uppsala RF test stand, from January to April(?) 2016;  CEA / Saclay has launched an Invitation To Tender for the design and construction of another 330kVA modulator for their RFQ test stand: -Contract awarded to DTI on Oct 2014; -Delivery foreseen for Jan 2016; -Soak testing at CEA/Saclay RFQ test stand from January to April(?) 2016;

11. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 11 The Stacked Multi-Level (SML) modulator- Topology

12. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 12 The Stacked Multi-Level (SML) modulator - Keypoints  Modular concept, allowing the increase of rated power by adapting the number of modules, keeping their size and weight under control. Facilitates maintenance;  Up to 660 kVA average power possible, allowing the supply of 4 x 1.2MW klystrons / IOT’s in parallel;  Compatible both with PULSED and CW operations and with different types of RF amplifiers (Klystrons, IOT’s, tetrodes, etc.);  Lower cost due to usage of standard LV components into a great extent (about 45% price reduction with respect to other topologies);  No active power electronic devices inside oil tanks (facilitates maintenance);  Reduced footprint/volume due to minimal sub-systems count;  Improved efficiency (~94%), due to minimal number of conversion stages;  Good AC grid power quality (constant power absorption = flicker-free operation, sinusoidal current absorption, unitary power factor);

13. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group  Engineering design complete;  Specification and procurement of subsystems: -Power Electronic stacks (SEMIKRON): complete (received and integrated); -LV electrical cabinet assembly (AQ Elautomatik): complete (received in Sept. 2014); -HV oil tank assembly (Ampegon-PPT): undergoing (delivered Jan 2015 ?);  Procurement of control hardware (CompactRIO, NI): complete and received;  Design and production of PCB’s (GDE Electronics): complete (received and integrated);  Development of control software (LTH): complete at ~40%;  LV electrical cabinets integration: complete last week;  Testing to be done… 13 Jun ’13 From a conceptual design to reality… Sept ’13 – May ’14 Apr ’14 Aug ’14 The Stacked Multi-Level (SML) modulator – Development roadmap May ’14

14. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 14 High Voltage Pulse Generation – Simulation results with ideal models 0.5ms 20kV Zoom @ rise time Rise time (0..99%)= 60µs 5µs 100V Zoom @ flat-top Flat-top ripple (pk-pk)= 0.1% @ 180kHz

15. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group High Voltage Pulse Generation – Simulation results with more precise models Rise time (0..99%)= 100µs Flat-top ripple (pk-pk)= 0.13% @ 90kHz 200V

16. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 16 1.Grid power quality (IEC 61000-x-x) (dictated by the capacitor charger)  EMC (conducted noise, immunity & susceptibility)  Current harmonic distortion (depends on the capacitor charger topology)  Flicker (depends on the capacitor charger topology & on the charging control scheme)  Flicker standard IEC 61000-3-2 and IEC 61000-3-11 (low voltage public grids) 14 Hz (  V/V) max =0.3% Possible Capacitor Charger: Active Front End + DC/DC converter with constant power regulation AC grid power quality – an All In One approach Active Front End

17. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 17 AC grid power quality – an All In One approach Simulation results (1 module: AC grid AFE + DC/DC charger) Compliance with IEC 61000-3-2, class C limit as per IEC 61000-3-2 Harmonic spectrum of AC line current AC line current AC grid active power AC grid reactive power Load pulse power Capacitor bank voltage Capacitor bank voltage (zoom) AC line voltage (zoom) - Flicker Compliance with IEC 61000-3-3 (ΔV/V = 0.06% wrt 0.3%@14Hz) AC grid power quality, including Flicker (THD = 2.3% wrt 13%@class C)

18. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 18 Cryo compressors Beam Instrumentation Neutron Instruments Modulators 400V 140 kV 20 kV 600V Cryo compressors Beam Instrumentation Neutron Instruments Modulators 20 kV 400V 600V 400V SVC - SVC footprint (outdoors): 2 x (10m x 15m) = 300 m 2 - SVC estimated cost : 2 x ~6 M€ = ~12 M€ AC grid power quality – A classical approach with external grid compensators

19. From a conceptual design to reality… The Stacked Multi-Level (SML) topology - Scaling up to full power Reduced scale prototype (120 kVA – 1x 704 MHz klystron) Full scale system (660 kVA – 4x 704 MHz klystrons)

20. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 20 330 kVA modulator – Development #1 Electrolythic capacitors (x108) H-bridge inverters (x36) based on MOSFET’s (x720) HVHF transformers (x36 units) AMPEGON AG

21. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 21 330 kVA modulator – Development #2 Diversified Technologies Incorporated, DTI Pulse Transformer (7.4tons; 1’850 liters of oil) Primary pulse generator (weigth = 5 tons)

22. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 22 Modulators for ESS Linac up-to Medium Beta decision chart SML reduced scale prototype is expected to be validated by summer 2015  If SML prototype is successful (Strategy A) -Extrapolation to the 660kVA modulator design is considered straightforward. It has been recognized (by ESS and manufacturers) that the SML topology is the one able to be scalable up-to 660kVA; Note: only the current (and the power) will be increased by a factor of 5; same circuit, same controls, same EMC mitigation, components will be scaled up, new thermal design (water cooling, heat exchangers, etc.); -ESS would launch an Invitation To Tender (ITT) for the construction and production of the 660kVA units (pre-series and series) for the Medium Beta; -ESS-Bilbao (IKC partner) would launch a similar ITT for the construction and production of similar 660kVA units for the RFQ and DTL (same topology, maybe different manufacturer ?);

23. Klystron Modulators for ESSCarlos A. Martins – ESS AB, Accelerator Division, RF Group 23 Modulators for ESS Linac up-to Medium Beta decision chart  If SML prototype not successful (Strategy B) -By April 2016 the two 330kVA modulators will(?) be validated following 4 months of soak testing in RF Test Stands; -ESS would launch an ITT for the development/series production of 17x 330kVA modulators (Medium Beta); -ESS Bilbao (IKC partner) launches another ITT for the development/series production of 6x 330kVA modulators ; Important remarks:  Strategy B will add an extra cost of about 15 MEURO to the baseline budget (based on strategy A);  Strategy B does not seem easier to implement within the current time schedule;  Strategy B could lead to two completely different modulator types.