Fault-recovery procedures and associated R&D Frédéric Bouly (IPNO/CNRS) - Isaías Martín (ADEX) MYRRHA accelerator 1 st International Design review WP3 - Task 3.2 WP1 - Task 1.2 Bruxelles, Belgium Tuesday, 13 th November 2012

Accuracy requirements 2 INTRODUCTION Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles13 th November 2012 Requirement on Energy accuracy : 600 MeV ± 1 MeV at the linac ouput. Control systems to ensure stability of the accelerating field and the synchronous phase Superconducting cavities gets a Q 0 (10 10 at 2K) with a 10 6 < Q L < Hz High sensitivity to mechanical perturbations ( Lorentz force, microphonics ) Accuracy requirements

Complete board with analogue mezzanine Objectives 3 INTRODUCTION Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles LLRF Digital system for the control of E acc & ϕ s Signal processing : In phase / Out of phase (I/Q) formalism Cavity frequency tuned to maintain RF power margins (CW) Fast cold tuning system + controller & feedback loop PXI V2 board: 5 ADC (14 80 MHz ), 3 DAC ( MHz ) FPGA handles: IQ demodulation, FIR and PID filtering, online monitoring via SDRAM, embedded NIOS II softcore processor for slow control operations ( collaboration LPNE/IPNO – IN2P3/CNRS Labs) Down converter system (19rack) Study the feasibility of retuning procedures (< 3 sec.) for the individually controlled cavities with a limited margin of CW RF power. Worked based on the β 0.47 linac section Model : cavity + tuning system + feedback/control loops Use of Matlab Simulink TM for time simulation Define the best control strategy for the tuning system - R&D on an adaptive & predictive controller (ADEX). 13 th November 2012

4 Introduction Cavity model & global control strategy - Dynamic study of a fast fault-recovery procedure - Tuning system controller R&D - Conclusion & Prospects Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles13 th November 2012

5 Introduction Cavity model & global control strategy - Dynamic study of a fast fault-recovery procedure - Tuning system controller R&D - Conclusion & Prospects Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles13 th November 2012

RF cavity model 6 Band pass resonator RLC parallel circuit. RF amplifier & beam seen as current generator for the cavity. One can link the cavity parameters ((r/Q), Q 0,Q L ) to R L (or R), L et C. Cavity model & global control strategy Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles StationaryTransient 13 th November 2012

7 Cavity model & global control strategy Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Control strategy (1/3) Complex plane representation : Cavity not frequency tuned Re Im IbIb O VbVb ψ ψ IgIg VgVg VbVb ϕsϕs V g (at ω 0 = ω) V inc V ref φgφg V cav Accelerating Field :V acc = V cav cos( ϕ s ) = V cI ψ depends on the cavity frequency tuning : V b (at ω 0 = ω) φgφg 13 th November 2012

8 Cavity model & global control strategy Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Control strategy (2/3) Optimal tuning is achieved to minimise the reflected power at the cavity input. Re Im IbIb O IgIg ϕsϕs V inc V ref V cav V b (at ω 0 = ω) IgIg V inc V ref Optimal frequency (de)tuning : We want to reach the optimal cavity frequency 13 th November 2012

9 Cavity model & global control strategy Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Control strategy (3/3) Re Im IbIb O ϕsϕs V cav V b (at ω 0 = ω) IgIg V g (at ω 0 = ω) φgφg VgVg VbVb VbVb ψ ψ φgφg V inc V ref Optimal frequency detuning : When the optimal detuning is achieved : φ g = ϕ s 13 th November 2012

10 Cavity model & global control strategy Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Control scheme for superconducting Cavity Amp. CAVITY Cold Tuning System Amp. Perturbations : Lorentz detuning Microphonics He bath pressure … V cI set-p, V cQ set-p V cI V cQ _ Δf SAF Δf L, Δf mic LLRF Loop CTS Loop Beam Low Level RF Controller Δf He ϕ S set-p φgφg φgφg =0 13 th November 2012

11 Introduction Cavity model & global control strategy - Dynamic study of a fast fault-recovery procedure - Tuning system controller R&D - Conclusion & Prospects Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles13 th November 2012

12 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Fault tolerance for the MYRRHA linac Fault tolerant : less than 10 unintended beam trips longer than 3 seconds - per 3 mounts operation cycle. Main beam trips origins in a linac : Injectors (source, RFQ, re-buncher) 2 injection lines for MYRRHA (1 spare line) RF amplifier Main problem for the individually controlled cavities Local compensation with limited RF CW power: Cavities are independantly powered 1 failed cavity (or 1 Cryomodule) is compensated by 2 cavities (or 2 Cryomodules) placed upstream & 2 cavities (or 2 Cryomodules) placed downstream. One has to be able to detect the failed element and to retune the cavities in less than 3 seconds. 13 th November 2012

13 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles LLRF feedback loop model Modelled in I/Q formalism - Transfer function in Laplace domain: Maximum RF power available 30 kW. Numerical system effects : Delay + ZOH + modulator. PI correctors adjusted to minimise beam loading effect. 13 th November 2012

14 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles CTS control loop Transfer function of the cold tuning system modelled from measurements 13 th November 2012

15 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Choice for the CTS controller Different option for the Tuning system controller have been studied : A PI corrector - An adaptive and predictive system (from ADEX) Example: Simple frequency controlExample: strong microphonics perturbations The Control is lost with PI controller 13 th November 2012

16 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles A fault-recovery scenario Recovery from the failure of a β 0.47 cryomodule Cavity n°76 One of the compensation cavities Cavity n°77 One cavity of the failed module 13 th November 2012

17 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Scenario description compensation cavity Cavity n°76 Failed cavity Cavity n°77 13 th November 2012

18 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Compensation cavity (n°76) 13 th November

19 Study of a fault-recovery procedure Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles Failed cavity (n°77) Motor detuning action at 1 kHz/sec Beam deceleration 150 keV >> keV (higher than acceptable limit from the 0.5 % error tolerance) Motor must detune the cavity at a speed higher than 5 kHz/sec. 13 th November 2012

20 Introduction Cavity model & global control strategy - Dynamic study of a fast fault-recovery procedure - Tuning system controller R&D - Conclusion & Prospects Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles13 th November 2012

21 Tuning system controller R&D Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles The ADEX system The ADEX system use an adaptive and predictive control methodology Predictive : instead of reacting to the error already produced, like PIDs, it predicts the process variable's evolution and thus anticipating to the predicted drifts from their set points. Adaptive : it learns in real time from the changing process dynamics in order to have a permanent precise prediction. The adaptive mechanism informs the driver block about the current process status and of the process output deviation from the desired trajectory. 13 th November 2012

22 Tuning system controller R&D Hardware definition In view of carry out real scale fault-recovery experiment a control prototype board is developed. It may support the execution of both conventional PID and ADEX control Board development collaboration ADEX (A. Nevado) & IPNO (N. Gandolfo). The control period of the ADEX algorithm is 2 milliseconds. PROCESS B3 Delfino Board B2 FPGA Board Cyclone III Main MCU Board dsPIC33F MAIN BUS MAIN BUS ADEXs objective: Executing the controller in less than 2 ms DAC ADC PIEZO Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles13 th November 2012

23 Tuning system controller R&D Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, Bruxelles ADEX controllers execution & communication C bit 28x Delfino Floating-point Series. ADEX controllers algorithm executed in μs. Communication trials have been performed with two Delfinos facing each other. The times spent for reading, writing and handling the necessary data are the following: Reading: μs Writing: μs Handling: μs Overall: μs. 13 th November 2012

24 Introduction Cavity model & global control strategy - Dynamic study of a fault-recovery procedure - Tuning system controller R&D - Conclusion & Prospects Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, BruxellesNovember 13 th 2012

25 Bouly F. & Martín I. MYRRHA accelerator 1st International Design review, BruxellesNovember 13 th 2012 Conclusion Based on existing systems a model of the cavity and its feedback loops have been developed : cavity + cold tuning systems + LLRF system + tuning system control loop. Results from simulations showed that it is possible to retune the cavities in less than 3 seconds. Still, procedure feasibility depends on the failure detection speed : here 30 ms are assumed. It is therefore highly recommended to dispose of a fast tuning system (response time : ~ 1 ms) : Otherwise, in certain cases, the spare RF power margin may not be sufficient The unused cavity can disturb the beam-conditions to fulfil : Beam deceleration must be lower than 0,5% Δw nominal ( ~ 20 keV ) In worst case, the minimum required detuning Δf 12 kHz (> 140 * bandpass) has to be achieved in less than 3 seconds. So we need a tuning system which : Acts on a broad frequency band a minimum of 20/30 kHz around f 0, is quite fast to detune the failed cavity V mini 5 kHz/sec, is very fast and precise for Lorentz detuning and microphionics compensation. On this basis a modular electronic board (prototype) is developed to implement an adaptive & predictive controller of the CTS. To be tested with experimental 700 MHz cryomodule.

26 THANK YOU ! Frédéric Bouly MAX 3rd General meeting, Madrid13 th November 2012