Transcript 10-RF_Status_Update-Nov-2014x

Status of the MICE RF System
K Ronald, University of Strathclyde
For the MICE RF team
MICE Project Board & RLSR, 24th November 2014
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Content
• Impact of the transition to the ionisation cooling experiment
• Timescales and revised RF apparatus
• Implications for components required
• Projected acceleration performance
• Implications for integrated RF system tests: MPB/RLSR Recommendation
• Status of RF drive system
• Plans & progress for tests of amplifiers
• Plans for delivery, installation of amplifiers
• Status of the LLRF systems
• Development of RF controls
• RF Cavity Test Progress
• Muon-RF phase determination
• Initial tests with real hardware and waveforms
• Procurement of hardware for further tests
• Plans for installation and commissioning of RF modules at RAL
MICE and ISIS synergies: RF subsystems and controls: MPB/RLSR Recommendation
MICE Project Board & RLSR, 24th November 2014
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MICE HPRF systems
• MICE HPRF system requirements have changed
• Fewer cavities, no coupling coil
• Required operational date is Autumn 2017
• Enables demonstration in data campaign from 2017-2018 of ionisation
cooling with energy restoration
• The MICE Demonstration of Ionisation Cooling requires
• Two individual cavities bracketed by two thin LiH absorbers, sandwiching
main absorber
• Cavities themselves are unchanged
• Each cavity is 430mm long with a Q of 44,000 and is resonant at
201.25MHz
• The cavities must still operate in a strong magnetic field environment
• Cavities are estimated (by simulation) to deliver 8MV/m at 1MW
dissipation- shunt impedance 5.9 MW
• Alan has described the cavity test progress
MICE Project Board & RLSR, 24th November 2014
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MICE HPRF systems
• The MICE Demonstration of Ionisation Cooling requires
• Two individual cavities bracketed by two thin LiH absorbers, sandwiching
main absorber
• Cavities themselves are unchanged
• Each cavity is 430mm long with a Q of 44,000 and is resonant at
201.25MHz
• The cavities must still operate in a strong magnetic field environment
• Cavities are estimated (by simulation) to deliver 8MV/m at 1MW
dissipation- shunt impedance 5.9 MW
• Alan has described the cavity test progress
MICE Project Board & RLSR, 24th November 2014
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Expected performance
• 2MW peak output from RF drive amplifiers, also unchanged
• LLRF requires ~10 % overhead to achieve regulation
• Estimated ~10 % loss in transmission line
• Power delivered to each cavity 1.62 MW,
• Anticipated gradient in each cavity 10.2 MV/m
• Slight uplift in gradient from 7.2 MV/m in each ‘STEP V’ cavity
RF system tests
• During summer 2014 an early integrated system test plan was developed
• Based on MPB/RLSR Recommendation
• Eminently feasible, cost and schedule implications fully developed
• Installation next to Daresbury amplifier test stand
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Schedule implications incompatible with new imperative- operation in 2017
New configuration magnetically similar to MTA tests- enhanced derisking
Maximal exploitation of tests at Daresbury and MTA for risk mitigation
Integrated system tests- 2 months available in installation plan
MICE Project Board & RLSR, 24th November 2014
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HPRF System Status
• MICE RF systems demonstrated
• Nominal power levels 2MW, Frequency (201.25MHz) for
1ms @ 1Hz
• First amplifier tested in MICE hall
• Triode amplifier (output stage) remains installed
• Tetrode and all modulator racks shipped to Daresbury
• New higher voltage solid state crowbar tested
• Electrical completion of triode No. 2 will commence
• Triode 2 will be tested using No. 1 tetrode and modulators
• Will use upgraded Triode No.1 modulator
• Each major No. 1 subsystem will be swapped for No. 2
sequentially
• Make fault finding more rapid
• Remote control philosophy being developed
• Will be tested during commissioning of No. 2 system
MICE Project Board & RLSR, 24th November 2014
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PSUs #1 – Progress at Daresbury
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The racks are re-installed at DL and connected to power
The 40 kV modulator is being upgrade with a solid-state crowbar switch.
Testing of the two new 40 kV crowbar switches sucessfull
– Switches integrated with trigger system
– Switches hold off over 40 kV with no false trips
– Run at 42kV for long periods.
– Discharge capability of two switches tested at up to 38 kV with the full 140 uF.
– Thyristors barely get warm.
Switch 1 has had over 120 shots at various voltage/charge levels.
Test apparatus showing crowbar
switch, resistor bank and CT
MICE Project Board & RLSR, 24th November 2014
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Crowbar Tests
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Tests carried out:
– Circuit tests using second switch as a load to trigger the crowbar and measure “arc” energy
Test voltage:
Capacitor:
Dump resistor:
24 kV
140 uF
5 ohms
CH 1 Overcurrent detector (trigger) CH 2 Firing pulse to crowbar
CH 3 Capacitor current (10 dB)
CH 4 Current in Load
Timebase 2.5 us / div
Peak current in crowbar:
Peak current in load:
Estimated energy into load: <10J
4.6 kA
1.2 kA
MICE Project Board & RLSR, 24th November 2014
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LLRF systems
• MICE LLRF: provide 1% amplitude, 0.5o phase regulation
• Will control tuner system
• LLRF system being developed by Daresbury LLRF group
• Using digital LLRF4 boards already procured
• First board operating at 201MHz in tests during August 2014
• Synergy with ISIS requirements for LLRF system
• For new ISIS LINAC amplifier test and commissioning stand
• Similar installation to the MICE amplifier test stand
• System is closely related to the implementation for existing Daresbury accelerators
• 0.1 % amplitude and 0.3o demonstrated in 1.3 GHz accelerating cavities
• Power ramp programming already demonstrated
• Boards will be tested during the amplifier commissioning programme
MICE Project Board & RLSR, 24th November 2014
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Implications for Power Distribution Network
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The change to a two cavity system has some implications for the RF delivery network
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Transmission lines planned to travel under floor level- no requirement to change
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Most components available from stock procured by Mississippi MRI grant
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Fewer hybrid splitters used- one amplifier driving each cavity
• Simpler tuning control and feedback system
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New experiment will demand higher power in 4” lines under floor
• This suggests it may be worth implementing SF6 insulation
MICE Project Board & RLSR, 24th November 2014
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RF Control System
• RF systems will require remote, automated control system
• ‘State Machine’ description being evolved by MICE Team
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‘Operator perceived’ states mapped for Amplifiers
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OFF- Fully hardware inhibited state
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ENABLED
• RF system verified closed: Hardware inhibits cleared
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STANDBY
• Heaters On: Highest state without PPS permit
• Hardware interlocked to coolant, monitoring of heater drive systems
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READY
• HT PSU’s Online, HT Grounds lifted, LLRF Online
• Hardware interlocked to PPS Permit, coolant, enclosure integrity
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ON
• RF system running
• Hardware interlocked to PPS Permit, coolant, enclosure integrity
• Software monitoring of forward and reverse power, coupler signals
MICE Project Board & RLSR, 24th November 2014
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RF Control System
• Detailed logic states within this overall philosophy are being informed by the ISIS
linac control system- excerpt below
4616
4616
4616
4616
4616
Filament + Water
Filament - Water
Grid Water
Screen Water
Anode Water
4616 Filament I/L
4616 Dummy Load Water
Dummy Load I/L
4616 Dummy Load @ Load
Injector Personnel 1
Personnel I/L
Injector Personnel 2
LC1202 Charging Unit Water
20kV Water I/L
20kV Ignitron Water
4616 Filament Regulator I/L
4616 Filament Voltage
4616 Filament Current
4616 Filament ON
Personnel I/L
4616 Filament I/L
20kV Water I/L
4616 Filament ON
Dummy Load I/L
20kV To Dummy Load I/L
20kV I/L
20kV I/L
4616 Grid Bias PSU Status
Earth Sticks Stowed
Cubicle Door Closed
Emergency Stop
Capacitor Cubicle I/L
• Will be built by Daresbury using established standard architecture
• Fast local hardware switches for critical system/safety protection
• PLC’s for more complex, less time critical functions
• Interface to EPICS MICE control system for monitoring
MICE Project Board & RLSR, 24th November 2014
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RF drive systems- plans to complete
• Two RF drive systems are to be delivered to the MICE hall
• Amplifier No. 2 will be progressively commissioned through 2014 into 2015
• Remote control and monitoring systems will be implemented during these
tests
• LLRF system will be tested with the amplifiers
• Delivery and installation of RF system No. 1 can be incremental
• As primary subsystems are replaced by the No. 2 units at Daresbury
• Taking account of STEP IV operations
• Installation resource requirements well understood from TIARA tests
• RF system No. 2 planned to be available for installation in 2016
• Four month commissioning window ending Nov. 2016
• This will be undertaken as an intensive delivery and installation operation
MICE Project Board & RLSR, 24th November 2014
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Timing System Specification
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We wish to know the difference between
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Transit time of any of our muons (in essence through ToF1)
A zero crossing of the RF system in any cavity- choose the first cavity
Use tracker measurement of trajectories to project forward to each cavity in turn
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LLRF phase (0.5o) stability specification is ~3x stricter than the resolution desired for the RF timing
system <20ps or <0.4% of the RF cycle
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In turn specification for RF timing is ~3x stricter than ToF resolution 50ps ~1%
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Should mean the timing accuracy is ~1% of RF cycle, defined by ToFs resolution
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Stability, and/or accurate knowledge, of all parameters in the system will be important
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Long cable runs, with dielectric insulated coaxial lines?
Phase relationship between the cavity fields and the signals on the test ports
Relationship between ToF signals and actual Muon transit
MICE Project Board & RLSR, 24th November 2014
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Overview of Timing Critical Elements
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Digitisers
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Sketch illustrates relationships of key components in the Demonstration experiment
Work in progress: Mathematical tests of digitiser interpolation
• Test sensitivity to vertical resolution, temporal sample rate, noise
Work in progress: Understand cable stability
Work to be undertaken: Test TDC/Discriminators in 201.25 MHz environment
Cavity 1 (RG213)
Cavity 2 (RG213)
Cavity 2
Discriminators (RF)
Discriminators (ToF)
TDC’s (RF)
TDC’s (ToF)
Computers
Cavity 1
Datarecorders
ToF 1
Beamline
ToF Signals RG213
MO Signal (RG213)
HPRF
HPRF
RF Amp 2
RF Amp 1
LLRF Feedback
RF Drive
201.25 MHz LLRF MO
Trigger
RF Drive
RF
LLRF
Clock
MICE Project Board & RLSR, 24th November 2014
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‘Sub’ Nyquist digitisation
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To acquire at Nyquist on 200MHz would demand a sampling rate of ~1-2G.Sa/sec, for 1ms
– Demands ~1 to 2MB per acquired channel, > 7.2GB/hr (assuming an 8 bit digitiser)
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Subsampling
– The Fourier Transform of the undersampled data maps the signal into its ‘unaliased’, relatively low
frequency range
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We may then retransform to the time domain to determine the time evolution of the signal
at some arbitrary point in time
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Must satisfy Nyquist on the linewidth- for our cavity natural linewidth is ~5kHz, effective
linewidth is ~10kHz, so sampling rate ~few hundred k.Sa/sec should be sufficient
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We assume 20M.Sa/sec, with 1ms we now have about 20kB per 8 bit recorded channel, data
rate of ~72MB/hr per channel
MICE Project Board & RLSR, 24th November 2014
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Comparison of rebuilt 20M.Sa/sec subsampled oscilloscope signal with
2G.Sa/sec recording: Agilent DSO-X G2004A
MICE Project Board & RLSR, 24th November 2014
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Timing hardware and Tests
• Use TDC and discriminators used in ToF system
• TDC’s CAEN V1290 25 ps multi-hit
• 25ps bin size maps to 7ps uncertainty (assuming Uniform PDF)
• LeCroy 4415A discriminators
• Needs to be tested in RF environment
• Use of same electronics as ToF mitigates systematic uncertainty & drift
• Both TDC’s and discriminators will travel to Strathclyde tomorrow
• To make efficient integration into DAQ ideally use VME digitisers for the subsample reconstruction
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At present continue to use fast, 8 bit, DSO’s to capture signal
Plan to use CAEN V1761 digitisers
1GHz, 4G.Sa/sec, 10 bit, 2 Channel instrument
Capable of 57.6MS/Ch
• RF cavity tests at MTA have provided real cavity probe signals for analysis
MICE Project Board & RLSR, 24th November 2014
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RF Installation and Commissioning
• RF amplifiers already discussed
• One amplifier previously installed
• Services and support systems well understood
• 1st Amplifier reinstalled- working around STEP IV operations
• 2nd Amplifier- 4 month installation plan- completion projected late 2016
• Pre testing to 1MW possible into hybrid and three 500kW loads
• RF main power lines installed from August ‘16 to February ’17
• Lines from final hybrid measured by VNA
• Matched for electrical length (allowing for hybrid), trimmed with phase
tuners
MICE Project Board & RLSR, 24th November 2014
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RF Installation and Commissioning
• Cavities
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SCTS Cavity tests proceeding very successfully at MTA
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Two cavities and 4 Be windows + spare set will be preselected, electropolished by LBNL
• Based on measurement of resonant frequency
• Four RF couplers will be built to upgraded design
• Delivery to RAL planned for Spring 2016
• Cavity assembly: RF team working with Mechanical assembly team
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Benefits from experience with similar SCTS
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Assembly planned at RAL, can be conducted in separate hall, 6-8 weeks
• Cavity will be installed into the vacuum chamber with Be windows
• Couplers installed and tuned for critical coupling (revised coupler clamp)
• Pick up probe calibration will be adjusted and measured
• Cavity tuning tested and measured, Q, f0 checked
• 2 weeks allowed for RF tuning of cavity
MICE Project Board & RLSR, 24th November 2014
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RF Installation and Commissioning
• Cavity vessels will be integrated with absorber vessels and focus coils
• Moved into beamline and pumped down, estimate 2 weeks effort
• MTA tests indicate X-ray shield requirements to be modest
• Require pressure < 10-7mB inside cavity
• Experience from MTA SCTS informs evacuation process
• Retest RF performance of cavities
• Complex cavity chamber environment limits bake options
• MTA test shows light bake is adequate on EP cavities
• Use hot water in cooling tubes to bake to ~80oC directly
• Estimate 2 weeks to evacuate and 2 weeks for bakeout
• Review RF performance after ultimate vacuum reached
MICE Project Board & RLSR, 24th November 2014
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RF Installation and Commissioning
• HPRF tests can commence once Amplifiers, Cavity and transmission lines installed
• Prerequisites planned to be complete Feb. ‘17
• One month of RF testing planned
• Initially without B-field
• Full tests of LLRF with tuner control
• Magnet commissioning derives from STEP IV plan
• Commence April ‘17 after RF pre-commissioning
• Requires addition of one further focus coil
• All magnets exist and have been tested at currents > requirements
• Once magnets commissioned RF commissioning with B-field
• This will build on tests at MTA
• Essentially repeat of tests without B-field
• Estimated 1 month of tests (May ’17)
MICE Project Board & RLSR, 24th November 2014
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Risk management and Resilience
• Certain risk and procurement items have been eliminated or mitigated
• Distribution network simplified
• 9 cavities available (2 needed)
• All major RF modulator components in hand
• 4 off Thales 116 Triode valves available (2 required)
• 2 spare sets of valve amplifier assemblies readily available
MICE & ISIS RF Subsystem: Synergies and Interaction
• MPB/RLSR Recommendation
• Strong correlations between MICE and ISIS Linac RF systems
• MICE RF Engineer has requested to participate in ISIS Linac commissioning
• ISIS Linac RF amplifier test station similar to MICE amplifier installations
• MICE RF Team working with ISIS Linac RF Team on LLRF systems
• ISIS Linac control philosophy used as model for MICE RF
• MICE RF system safety under MICE-ISIS Safety committee
MICE Project Board & RLSR, 24th November 2014
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Summary
• Progress achieved enhancing the capabilities of the RF amplifier modulators
• In environment where most EE effort focussed on STEP IV
• Plans developed for commissioning two amplifiers chains by 2016
• Progress on LLRF system for 201MHz implementation
• Synergies with ISIS project
• Progress in Muon-RF phase determination
• Sub-sampling and reconstruction shown to work with real 8 bit data
• Includes wideband noise and digitisation artifacts (8 bit vertical
resolution, with timebase jitter)
• Equipment to test TDC based system available now
• Resilient plan in place to bring system together for commissioning tests
• Completion of hardware, Spring 2017
• Coherent experimental plan achievable if operational by Autumn 2017
MICE Project Board & RLSR, 24th November 2014
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Crowbar Switch Design
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Fast crowbar switch needed to protect high
power amplifier tube from potentially
damaging internal arcs. ~ 100kJ in the
capacitor banks.
APP Crowbar Switch
Model S62-2-12
48 kV
Switch characteristics:
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fast turn-on to low impedance state
capability to discharge large amounts of
stored energy.
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Hybrid design combines a small fast switch
in parallel with a slower large area slow
switch
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The resistors R1-R2 ensure that current is
shared between SW1-SW2 initially but
then they also force the current into SW3
as SW3 turns on. C1 and R3 assure AC and
DC voltage sharing between stages.
MICE Project Board & RLSR, 24th November 2014
Conceptual Schematic
C1: Snubber Capacitor
R1-R2: Resistors for Current Sharing
R3: Balancing Resistor
SW1-SW2: Fast Thyristors
SW3: Large Area Thyristor
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Crowbar Tests
• Tests carried out:
– Leakage current measurement on each thyristor in the stack
– Voltage withstand tests up to 42 kV dc for 30 minutes
– Crowbar discharge tests up to 38 kV with 6 uF, 70 uF and 140 uF
capacitance
Crowbar discharge test – 38 kV 140 uF 1 us/div
Ch 1 – trigger signal (TGP 110)
Ch 2 – trigger pulse (APP EB0046)
Ch 3 – current (6dB attenuator) Ch 4 – Switch voltage (x10)
Note rapid turn on of switch; Switch voltage down to 30% (11 Kv) at 1
us after trigger pulse
MICE Project Board & RLSR, 24th November 2014
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Testing of Spectral Domain Remapping
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201.25MHz signals computed (with ramp envelopes) and recorded at both 2G.Sa/sec and
20M.Sa/sec effective digitisation rates
Signals compared after FFT and spectral region remapping, and again after iFFT, to compare
the time domain of source signal
– Good agreement obtained
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Computer used to simulate vertical digitisation error (i.e. 8 bit resolution of digitising typical
oscilloscope)
– Again signals compared and reasonable agreement obtained
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Realistic data obtained by high speed oscilloscope
– Gives realistic vertical (8bit) resolution error and horizontal jitter
– Reconstruction process repeated
MICE Project Board & RLSR, 24th November 2014
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Comparison of synthesised 8-Bit digitised 201.25MHz wave
recorded at 2G.Sa/sec with IFT of padded 20M.Sa/sec data
MICE Project Board & RLSR, 24th November 2014
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Amplitude
Real data taken from Agilent DSO-X G2004A
0.4
0
-0.4
0
1
0.5
MICE Project Board & RLSR, 24th November 2014
Time/ms
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