MICE RF System review Andrew Moss Daresbury Laboratory

MICE RF System review Andrew Moss Daresbury Laboratory Collaboration Meeting 34 15 th 19 th October 2012 RAL

Contents • • • Amplifier update and status Amplifier testing Results of RF review Hall layout LLRF First results from High Pressure Gas Filled RF Cavity Beam Test at the MTA • Progress on Cavities for MICE • Conclusion Andrew Moss

RF system components Master Oscillator Controls etc DL Test System NEW At present Auxiliary Systems HT Supplies 250 k. W Amplifier 2 MW Amplifier 2 MW Amplifier Auxiliary Systems HT Supplies Daresbury LBNL CERN 201 MHz Cavity Module 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 k. W amplifier has been bought, and has been under test at the manufacturers First 250 k. W amplifier has operated at 100 k. W with old tube, then 240 k. W with new tube fitted during 2012 First TH 116 high power amplifier has operated at 1 MW during 2011 using an old RAL tube – new MICE tube fitted, has operated at 1. 2 MW for short time Two further 250 k. W amplifiers are being refurbished now Two refurbished 2 MW CERN amplifiers 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 250 k. W amplifier cavity New amplifier operating at 240 MHz (driver low on gain at 201 MHz) Delivered to Mississippi on 8 th June 2012 Andrew Moss

New tetrode tube in DL test amplifier number 1 • Tube needed to be conditioned after spending 3 years on shelf • Input matching set far to high (S 21 45 d. B), eventually this was optimised at around 20 d. B • 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

250 k. W 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 cavity • final 250 k. W 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. 2 MW with good conversion efficiency and gain • Overload of power supply resistors caused system stop, replaced with higher power units, testing underway, but now problematic – repeated crowbar events • Suspect tube needs to be conditioned, next week? Forward power into load Andrew Moss

Amplifier layout Andrew Moss

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 4616 tetrode amplifiers Previously a lot of RF components were placed behind Shield wall TH 116 Triode amplifiers

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

Coax system distribution Andrew Moss

Andrew Moss

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

Coax power and Losses • Assuming 2 MW from the amplifier and 500 k. W for each cavity coupler • Using calculations obtained from MEGA, the peak standoff for 6 inch coax with MICE parameters is 3 MW, for 4 inch coax it is 1. 4 MW • With N 2 gas at 1. 5 Bar this rises 3. 6 MW and 1. 68 MW 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 phasing 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 moun 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 p. S • 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 ~ 3 months • Systems in use already with EPICS control, feedback, feedforward, resonance control etc • Ramped pulse structure to limit reflected power tested on bench with 1. 3 GHz cavity Mice cavities Amplifier Andrew Moss

RF system monitoring and protection Andrew Moss

Andrew Moss

Ben Freemire Andrew Moss

Andrew Moss

Andrew Moss

Andrew Moss

Summary • Progress on all three 250 k. W amplifiers including new system in USA • Tested first MICE high power tube and system to 1. 2 MW, some issues to resolve before 2 MW • 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 • RF review has prompted a new round of optimisation of coax distribution that looks to make things easier in a number of areas, space around the amplifiers, lower transmission loss, easier to install • Ready to procure coax Andrew Moss

Cavity Progress at LBNL/Fermi. Lab • 1 st Cavity Electropolished • Now at Fermi. Lab • 9 Cavities to be polished • New Coupler Design • Nearing Completion • 6 Actuators to be built • For the tuning arms • Fermi. Lab/MTA have other required components • Ready to move to clean Cavity section view room • Assembly of 1 st cavity • Install into single cavity test chamber • Testing initially in fringing field • ~1 T Page 29

Cavity section view Revision to RF layout Original Arrangement Revised Arrangement • 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 Page 30

Revision to RF layout View over top of shield wall • Mounting clamps and hangers for co-axial lines designed Preparation for TIARA & Procurement • Plan for installation of STEP IV allows for amplifier installation in 1 st Cavity section view 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 Page 31