Status of the MICE RF System K Ronald, University of Strathclyde For the MICE RF team 1MICE Project Board, 17th April 2015

Content 2 Redesigned distribution network Change from STEP V design Used under-floor delivery The demonstration experiment has simpler distribution requirements Now makes sense to use ‘over air gap’ network Status of RF drive system Plans for test, delivery and installation of amplifiers Development of LLRF controls Status of the LLRF resources Muon-RF phase determination Initial tests with waveforms from MTA tests Hardware now at Strathclyde for RF tests MICE Project Board, 17th April 2015

MICE HPRF systems 3 MICE HPRF system requirements have changed Fewer cavities, no coupling coil Required operational date is Autumn 2017 Enables demonstration in data campaign from 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 MHz 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 M  Alan has reported on the ongoing tests at FNAL MICE Project Board, 17th April 2015

MICE HPRF systems 4 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 MHz 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 M  Alan has reported on the ongoing tests at FNAL 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 10.3 MV/m Slight uplift in gradient from 7.2 MV/m in each ‘STEP V’ cavity MICE Project Board, 17th April 2015

RF network: STEP V/VI 5MICE Project Board, 17th April 2015 Amplifiers installed behind shield wall Triodes on main floor, Tetrodes on Mezzanine Impact of B-fields negated by yoke Line installation planed before yoke support risers High power dynamic phase shifters removed 4 off 6 inch coax lines over wall Pressurised to increase power handling Line lengths matched using 3D CAD Manually adjustable line trimmers installed at cavity to take up assembly errors in coax length Flexible coax final feeds Allows for small misalignments 10 hybrid splitters Split power for the opposed couplers of each cavity Lines will be pressurised with 2Bar Nitrogen Amplifiers behind Shield Wall Distribution Network to MICE

RF network: Demonstration experiment 6MICE Project Board, 17th April 2015 Flexible coax Line Trimmers Hybrid Splitter Directional Coupler in each line 4616 Pre Amplifier TH116 Amplifier 500kW Load Directional Coupler 6 inch

RF network: Demonstration experiment 7MICE Project Board, 17th April 2015 Propose to have 1 load on the hybrid splitter to each RF cavity absorbs unbalanced reflections Crane hook height fully retracted does not clash with the coax over the wall. Support for network will be from present ‘shield wall’ and from yoke supports

RF network: Demonstration experiment 8MICE Project Board, 17th April nd TH116 amplifier moved to 3 rd position behind wall to use the space and ease installation in congested area With only 2 RF amplifiers now relatively straightforward to place auxiliary systems (cooling) Water cooling for load will need to route over the air gap on the transmission lines

RF network: Demonstration experiment 9MICE Project Board, 17th April 2015 Offcentre mounting of hybrid allows neat take up of 90 degree phase Orientation of load arbitrary- plan to align with the 6” distribution line and share mountings Minimised length of 4” line- minimises breakdown and losses

RF network: Demonstration experiment 10MICE Project Board, 17th April 2015 Offcentre mounting of hybrid allows neat take up of 90 degree phase Orientation of load arbitrary- plan to align with the 6” distribution line and share mountings Minimised length of 4” line- minimises breakdown and losses

RF network: Demonstration experiment 11MICE Project Board, 17th April 2015 With slightly higher mounting of the RF network, work platform can be accommodated above channel Such a platform can be useful for RF and other work RF assemblies from hybrids to flexible lines can be prebuilt and craned in as components Rapid assembly and servicing/access

Implications for Power Distribution Network 12 The change to a two cavity system has some implications for the RF line loading New experiment will demand higher power (1MW peak, 1kW average) in 4” lines under floor Plan to implement SF 6 insulation 4” lines and components rated to 1.12MW peak in air at 1 bar (data from manufacturer/supplier) Likely during full reflect during cavity fill we will have up to double the voltage on the line (eq. to 4MW) This will be mitigated by slow fill Also mitigate with insulating gas MICE Project Board, 17th April 2015

HPRF System Status 13 MICE RF systems demonstrated Nominal power levels 2MW, Frequency (201.25MHz) for 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 Dependent on electrical engineering resource availability MICE Project Board, 17th April 2015

HPRF System Controls 14 Principle activity has been definition of the remote control and monitoring requirements INSERT HERE one-two slides on controls and monitoring: Key parameters and interlocks- the following two slides are presently placeholders MICE Project Board, 17th April 2015

PLACEHOLDER RF Control System RF systems will require remote, automated control system ‘State Machine’ description being evolved by MICE Team ‘Operator perceived’ states mapped for Amplifiers OFF- Fully hardware inhibited state ENABLED RF system verified closed: Hardware inhibits cleared STANDBY Heaters On: Highest state without PPS permit Hardware interlocked to coolant, monitoring of heater drive systems READY HT PSU’s Online, HT Grounds lifted, LLRF Online Hardware interlocked to PPS Permit, coolant, enclosure integrity ON RF system running Hardware interlocked to PPS Permit, coolant, enclosure integrity Software monitoring of forward and reverse power, coupler signals 15MICE Project Board, 17th April 2015

PLACEHOLDER RF Control System Detailed logic states within this overall philosophy are being informed by the ISIS linac control system- excerpt below 16MICE Project Board, 17th April 2015 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

LLRF systems MICE LLRF: provide 1% amplitude, 0.5 o 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 0.3 o demonstrated in 1.3 GHz accelerating cavities Power ramp programming already demonstrated Boards will be tested during the amplifier commissioning programme 17MICE Project Board, 17th April 2015

Timing System, Desired Specification We wish to know the difference between 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 LLRF phase (0.5 o ) stability specification is ~3x stricter than the resolution desired for the RF timing system <20ps or <0.4% of the RF cycle In turn specification for RF timing is ~3x stricter than ToF resolution 50ps ~1% Should mean the timing accuracy is ~1% of RF cycle, defined by ToFs resolution Stability, and/or accurate knowledge, of all parameters in the system will be important 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, 17th April

Overview of Timing Critical Elements 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 MHz environment ToF 1 Cavity 1 RF Amp 1 LLRF Beamline HPRF RF Drive LLRF Feedback TDC’s (ToF) TDC’s (RF) Digitisers Datarecorders RF Clock Trigger Discriminators (RF) Discriminators (ToF) ToF Signals RG MHz LLRF MO MO Signal (RG213) Computers RF Amp 2 HPRF Cavity 2 RF Drive Cavity 2 (RG213) Cavity 1 (RG213) MICE Project Board, 17th April

‘Sub’ Nyquist digitisation 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) – 400  s window presently being acquired at MTA- requires minutes of time to record traces Fourier domain signal reconstruction – The Fourier transform of the undersampled data maps the signal into its ‘unaliased’, relatively low frequency range We may then retransform to the time domain to determine the time evolution of the signal at some arbitrary point in time 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 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, 17th April

Comparison of rebuilt 20M.Sa/sec subsampled oscilloscope signal with 5G.Sa/sec recording: LeCroy (INSERT MODEL NO) MICE Project Board, 17th April T Stanley returned from FNAL with many GB of data – Alex Dick at Strathclyde has been processing these real traces using subsample Fourier domain reconstruction

Timing hardware and Tests Use TDC and discriminators used in ToF system TDC’s CAEN V 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 PLACEHOLDER INCLUDE INFO ABOUT HARDWARE NOW AT STRATHCLYDE To make efficient integration into DAQ ideally use VME digitisers for the sub- sample reconstruction 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 22MICE Project Board, 17th April 2015

Summary 23MICE Project Board, 17th April 2015