Andrew Moss Daresbury Laboratory Collaboration Meeting th -16 th February 2013 Coseners House MICE RF HP System rprogress

Contents System Overview –MICE Hall System –Test System at Daresbury Amplifier update and status –Amplifier testing LLRF Layout –Will be presented by Alan Grant Conclusion Andrew Moss

RF system components Andrew Moss 2 MW Amplifier Master Oscillator Controls etc 201 MHz Cavity Module 2 MW Amplifier 201 MHz Cavity Module LBNLCERN 250 kW Amplifier HT Supplies Daresbury DL Test System At present Auxiliary Systems NEW

Amplifier layout Andrew Moss

Test system at Daresbury Andrew Moss

Status of Amplifier s and power supplies Test bay at DL is operational and able to test amplifiers and power supplies as they become available New 250 kW amplifier has been bought, and has been under test at the manufacturers First 250kW amplifier has operated at 100kW with old tube, then 240kW with new tube fitted during 2012 First TH116 high power amplifier has operated at 1MW during 2011 using an old RAL tube – new MICE tube fitted, has operated at 1.2MW for short time Two further 250kW amplifiers are being refurbished now Two 2MW CERN amplifiers circuits refurbished but awaiting assembly and high power test Still need to build 3 more sets of power supplies – including set for TIARA tests in experimental hall September 2013 Andrew Moss

New amplifier in test bay at Photonis USA Andrew Moss

New 250kW amplifier enclosure Andrew Moss New amplifier operating at 240MHz (driver low on gain at 201MHz) Delivered to Mississippi on 8 th June 2012

New tetrode tube in DL test amplifier number 1 Tube needed to be conditioned after spending 3 years on shelf Input matching required careful tuning as new valve presents different RF load eventually this was optimised at around 20dB After 20 hours running, with a lot of adjustments to amplifier and electrical parameters, system is stable and predictable with linear response Still some issues with screen power supply to sort out – loading of screen is moving with beam current and output loading Andrew Moss

250kW amplifiers numbers 2 and 3 One amplifier is now completed and assembled in rack Small number of parts left to source from the manufacturer because they are missing – may need modification to suit much older design of amplifier enclosure final 250kW amplifier will be assembled back into rack in the next few months Andrew Moss

CERN amplifiers Need assembly with the support of CERN Very similar electrical design philosophy for the heater and control functions etc Addition of cathode switch electronics needed and possible small modifications so that they can be operated by the power supplies we already have – will be done as we find issues Already have additional coax sections (for twin output couplers) and second test load Andrew Moss

RF and power supply testing Operation at 1.2MW with good conversion efficiency and gain Overload of power supply resistors during a crowbar caused system stop, replaced with higher power units, testing underway, but now problematic – repeated crowbar events Andrew Moss Forward power into load

Current status HP Tests Testing of the amplifier system continued into late 2012 –However performance above 300kW proved to be very difficult After a period of diagnosis on the power supply and amplifiers it was decided to remove the new tube and revert back to the old used tube to re-establish settings on the amplifier system As the power tube was removed it became clear that sparking had occurred around the valve which clearly indicated the source of the problems we had experienced –This would have triggered the initial crowbar event –Would have inhibited further increases in output power Andrew Moss

116 triode removal Andrew Moss Evidence of arcing on HT connection

HT top box HT top box is where high voltage is applied to the anode Water coolant is supplied to the valve using insulating glass rods On the original LBNL amplifier, coolant passed out of the system as steam CERN HT top box with ability to pass both coolant flow and return pipes, which is why it was used Original LBNL HT top box with small inlet for only one coolant pipe HT box to tube interface is slightly different and is where fault is created LBNL HT top box is being converted to two water pipes and with correct spacing should remove issue that created arcing Andrew Moss

HT Top Box Andrew Moss The seating of the valve in the HT top box has caused the arcing The HT box actually belongs to another amplifier and was swapped in to speed up the commissioning process However there are some dimensional and location differences that obviously have caused the issues that we can see when the tube is removed

HT connection Picture shows the correct spring finger arrangement that is required for the LBNL amplifier Using the CERN top box allowed the valve to be pressed too far down into the socket causing the incorrect alignment All parts are being machined now ready for fitment to the amplifier in the next 5 weeks Amplifier testing will then proceed again with the old Triode tube first to 1MW The Triode tube will then be swapped for the new device and tested to 2MW Andrew Moss

Coax power and Losses Assuming 2MW from the amplifier and 500kW for each cavity coupler Using calculations obtained from MEGA, the peak standoff for 6 inch coax with MICE parameters is 3MW, for 4 inch coax it is 1.4MW With N2 gas at 1.5Bar this rises 3.6MW and 1.68MW respectively Using slow cavity filling technique the reflected power from the cavity can be substantially reduced (P forward + P reflected = P total) we expect P reflected to be less than 20% of P forward = peak standoff will not be exceeded at start of each pulse Calculations of attenuation and hence power loss though coax is 10% per cavity coupler, which will reduce gradient available, overdriving amplifier maybe possible with reduced reliability – still need to test this Andrew Moss

RF to beam synchronisation Cavity phase and amplitude will be stabilised to 0.5 deg and 1% with the ability to run as high a gradient as possible Muon particles will arrive randomly in the cooling channel for acceleration at various phase angles Cavity phase angle will have to be measured for each muon and time stamped for analysis after a period of running Time of flight detectors along the cooling channel will be used to trigger electronics to measure and digitise the state of the cavity phase angle to < 15 pS Groups from Sheffield and Strathclyde University’s in conjunction with DL and LBNL are working on possible solutions for this area of the experiment Andrew Moss

Digital low level RF Control To control and regulate cavity amplitude and phase angle during the RF pulse DL able to build up hardware ~ 3months Systems in use already with EPICS control, feedback, feedforward, resonance control etc Ramped pulse structure to limit reflected power tested on bench with 1.3GHz cavity Andrew Moss Amplifier Mice cavities

RF system monitoring and protection Andrew Moss

Summary Progress on all three 250kW amplifiers including new system in USA Tested first MICE high power tube and system to 1.2MW, some issues to resolve before 2MW –Arc on anode HT plate identified –Probably the cause of the crowbar events –Modification to HT circuit completed, re-assembly completion imminent –Problems with crowbar circuit resolved High power testing to resume at DL as soon as resources allow –2MW peak power objective Tests in MICE hall by September We plan to replicate the power supplies and install and test them at DL – this will allow testing to continue, then move one set of amplifiers and power supplies to the MICE hall for September 2013 Andrew Moss

Extra Slides Andrew Moss

Page 24 Cavity Progress at LBNL/FermiLab 1 st Cavity Electropolished Now at FermiLab 9 Cavities to be polished New Coupler Design Nearing Completion 6 Actuators to be built For the tuning arms FermiLab/MTA have other required components Ready to move to clean room Assembly of 1 st cavity Install into single cavity test chamber Testing initially in fringing field ~1T Cavity section view

Page 25 Revision to RF layout Proposed change to layout Pairing of identical amplifier assemblies Should afford efficiency in running up Two hybrids move to the amplifier side of the shield wall Line lengths re-matched by sections lying along the top of the shield wall No interference with crane service Cavity section view Original Arrangement Revised Arrangement

Page 26 Revision to RF layout Cavity section view Preparation for TIARA & Procurement Plan for installation of STEP IV allows for amplifier installation in 1 st slot To meet TIARA deadline, September 2013 Procurement of co-axial components, new tetrode and amplifier modulator components New Tetrode procured Component list for co-axial and modulator components ready Procurement of components required for TIARA prioritised View over top of shield wall Mounting clamps and hangers for co-axial lines designed

Review of the RF system Review meeting held in December 2011 to assess all aspects of current RF system design and strategy - praise for the design work we had done and the results with the amplifiers The main concern of the review panel was of the RF coax layout, the panel suggested a different layout that would improve access to the amplifiers and simplify the coax runs. This was taken on board and a new layout designed Previously a lot of RF components were placed behind Shield wall TH116 Triode amplifiers 4616 tetrode amplifiers

RF phasing Andrew Moss

Amplifier order changed so that experience of LBNL amplifiers will be consistent

Andrew Moss Coax system distribution

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RF coax parts list Andrew Moss All RF coax parts identified and designed to fit between the amplifiers and the cavities

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RF distribution RF coax distribution system has been finalised in 3D CAD so that line lengths are matched Enough flexibility has been built into the system to take up small random errors Purchasing of components has begun System will be pressurised with 2 Bar of nitrogen to help voltage standoff and use RF pulse shaping to minimise RF reflected power during the cavity filling period – this will increase reliability Andrew Moss