1. Rihua Zeng RF Group, Accelerator Division, ESS ERIC Oct 29, 2015
Energy Efficiency Improvement in LLRF Control for Superconducting Cavities
Rihua Zeng
RF Group, Accelerator Division, ESS ERIC
Oct 29, 2015

2. Outline
Time&Technology is ready to break through the operation limit of power amplifiers
People and not the technologies are the limiting factor
Effort at ESS to break the limit

3. Morten Jensen

4. A Typical RF System Schematic and LLRF Control
Anders J Johansson

6. Time is Ready
Each generation of accelerator has it's own set of needs, and under its own context of social and technology movement The progress and technology in accelerator moves steadily forward, no matter we like it or not, and we use it or not

7. The First Cyclotron (Ernest O. Lawrence&M. Stanley Livingston)

8. The Frist RF accelerator
The need of alternative solution for electrostatic accelerators (400 keV protons)
1920s, maturity of technology for radio broadcasting:
Vaccum tubes (Triodes) available for high power at few MHz
Electornics: oscillating circuits, components.
Break the limits of discharge between electrodes in electrostatic accelerators
RF becomes the center of accelerator
5 MeV achieved in larger cyclotron

9. The next one: First Linear Accelerator
The need of higher RF frequencies, in order to reach higher energies and keep reasonable dimensions
Under the context of rapid development of powerful radar systems in 1940s. Invention of of kystron “cavity resonator”, the mature of RF technology in higher frequency(above GHz )
Break the limits of RF radiation from resonant circuits

10. Alvarez DTL (32MeV, 202.56MHz) in Berkeley

11. 3GHz linac at Stanford

12. RF technologies doesn’t change so much since then, excepting superconducting cavities
Steady progress are made to exploit them on a large scale and specific application area
Then need changes gradually to how to better operate RF&cavity system effectively and efficiently, under the require of high stability, higher reliability and efficiency

13. The need and context in current accelerators
The higher efficiency/higher stability/high reliability we want to go, the more details and deep understanding of system dynamic need to be figured out
The revolution of modern information technology, following the mature of semiconductor technology

14. The technology is ready

15. Technology is ready
Information & computer technology renovation bring adequate and complete information to identify system dynamics in width
High performance hardware bring high resolution and high accurate information to identify system dynamics in depth 
remarkable achievement in accelerator community making working much easier 

16. Break Through the Operation Limitation of Power Amplifiers

17. Perturbations in Reality
Beam Loading
Lorentz force detuning
Microphonics
Thermal effects (Quench…)
Cavity
Synchronous phase
Beam chopping
Pulse beam transient
Charge fluctuations
Non-relativistic beam
Pass band modes
HOMs, wake-field
Modulator drop and ripple
Klystron nonlinearity
Power Supply
Reference thermal drift
Master oscillator phase noise
Phase reference distribution
Crates power supply noise
Cross talk, thermal drift
Clock jitter, nonlinearity
Electronics crates
Further reading: LLRF Experience at TTF and Development for XFEL and ILC, S. Simrock, DESY, ILC WS 2005

18. People and not the technologies are the limiting factor

19. Disconnect between different systems (we are living in different world, LLRF, HPRF, Beam dynamics)
Resources available are not well used (we always ask more, but they are not in use)
Divergent background and interests of in-kind partners at ESS

20. Effort at ESS to break the limit
Take advantage of requirement and interface requirement campaign at ESS
Hardware harmonization
make best of what is available
RF turn on procedures
a platform to connect different systems, and bring together the cavity testing effort of different ESS test stands all over the European
Online cavity model
a methodology to integrate real-time measurement, modeling and data/database, to really identify detailed dynamics

21. Effort at ESS to break the limit
Take advantage of requirement and interface requirement campaign at ESS

22. Hardware Hamonization
A lot of work done by LLRF(Anders Johansson), Beam instrumentation, and ICS to use the same hardware platform
Make the best of what is available

23. RF Turn on Procedure

25. RF Turn on Procedures Create a platform to connect different systems
RF commissioning
Beam commissioning
Cavity commissioning
Bring together the RF/LLRF test effort of different ESS test stands all over the European
Uppsala
France
Spain
Poland
Lund
Create a platform for jointly development, thereby bringing in open innovation

26. Warm Coupler Conditioning Time(Denis Kostin, DESY)
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28. Courtesy of Chiara Marrelli & CERN colleagues

29. Online Cavity Model
A methodology to integrate real-time measurement, modelling and data/database, to really identify detailed dynamics

30. Well-Recorded data in high details
Motor tuner transfer function/DESY
Quench limitation identification/DESY
Klystron input-output characteristics/JPARC
Lorentz force detuning/Fermilab

33. Summary
The time and technology are mature enough to increase energy efficiency
The people and not the technology are the limiting factor
How we can take this opportunity, and make the best of what is available at ESS