The MERLIN accelerator being commissioned at AWE in a new Technology Development Centre will provide one of the flash radiographic sources at a joint UK/French facility for hydrodynamic testing in support of the two nations' nuclear deterrents. The ten module Induction Voltage Adder (IVA) has been designed to provide a 60 ns long TerraWatt pulse to drive a Self Magnetic Pinch (SMP) electron beam diode at 7.5 MV. The design work for MERLIN was carried out by L3 Pulse Sciences in San Leandro, California and builds on previous IVA experience in the USA. Prototyping of sub-systems was also carried out by L3 to confirm that the performance and reliability requirements for the overall accelerator can be met. However, it is only now that all the components of the accelerator have been brought together and its overall function can be characterised and compared with predictions. Commissioning of the accelerator has involved setting to work the ancillary systems which provide and control oil, deionised water, sulphur hexafluoride gas, vacuum, control and instrumentation, diagnostics and data acquisition. With these operating satisfactorily testing of the pulsed power systems was able to commence. Commissioning of the pulsed power systems started with a run up of the Marx generator into a resistive load to its operating voltage of 2.5 MV, including characterisation of the trigger systems and the diverter switches. These are intended to short the Marx output after it reaches peak voltage, or if a prefire occurs, in order to reduce the risk of electrical breakdowns. The waveforms produced during factory tests in the US were successfully reproduced and the jitter of the trigger systems shown to meet specification. This allowed the commissioning programme to proceed to the active commissioning phase where an X-ray output is generated. Active commissioning is enabled by the Marx generator being connected via an oil insulated transfer line to the Pulse Forming Lines (PFLs). Each module of MERLIN comprises an induction cell driven by one of these PFLs. The upstream section of each PFL receives its 2.5 MV charge from the Marx generator on a microsecond timescale before its pulse forming action is initiated by a laser triggered gas switch. The laser triggering should provide nanosecond order synchronisation, and hence excellent pulse reproducibility, when the pulses are combined in the adder. The 60ns duration 1.1 MV outputs of the PFLs are fed to their corresponding induction cells which act to perform voltage addition along a 28 metre long 80 Ohm MITL. This delivers an 11 MV forward going wave to the e-beam diode. The pulsed radiographic source driven by MERLIN will be a SMP diode developed in an AWE led research programme in collaboration with US National Laboratories. This diode operates at approximately 40 Ohms with the result that retrapping of the MITL sheath current occurs transforming the 11 MV forward wave down to ~ 7.5 MV while increasing the load current to ~ 200 kA. The PFL's configuration tailors the output pulse to compensate for the SMP diode's intra-pulse impedance droop and hence generate a relatively constant voltage during the X-ray flash. Since the SMP diode is a single shot device (due to the energy density incident at the anode/X-ray converter) a Large Area Diode (LAD) of similar impedance is utilised to allow repeated testing of the pulsed power systems. By mid-2017 the testing of the Pulsed Power systems and MITL with the LAD is due to have been completed and the optimisation of the SMP diode should be in progress.

The ten-module Hydrus Induction Voltage Adder, designed by L3 Communications - Pulse Sciences Division for AWE, builds on previous IVA experience in the US. Each of the ten modules comprises a 1.4 MV induction cell driven by a laser triggered gas switched Pulse Forming Line (PFL) in order to provide nanosecond order synchronisation, and hence excellent pulse reproducibility. The PFLs are charged by a single Marx through an oil-insulated transmission line. The outputs of the cells are added along a 22 metre long 80 ohm MITL to deliver an 11 MV forward going wave to the e-beam diode. The accelerator will be used for flash radiography by AWE utilising a Self Magnetic Pinch diode as the radiographic source. This diode operates at approximately 40 Ohms with the result that retrapping of the MITL sheath current occurs, reducing the diode voltage to ~ 7.5 MV, but increasing the load current to 200 kA. The detailed PFL design was previously prototyped and has been chosen to tailor the output pulse to compensate for the SMP diode's intra pulse impedance reduction and hence generate a relatively constant voltage during generation of the X-ray flash. The components of the Hydrus IVA are approaching completion at L3 Pulse Sciences at San Leandro, CA. All parts of the IVA are being procured by L-3 PS and delivered to San Leandro for subassembly. The major IVA subassemblies being fabricated comprise the Marx, oil line, PFL, cell, and stalk. Ancillary systems being fabricated comprise the control software, vacuum, water processing, oil processing, magnetic core reset, gas processing, data acquisition, and power supply. Subassemblies and subsystems are subject to a variety of QA tests which include high voltage testing of the Marx and its trigger, and a first-article PFL driving both a dummy load and a first-article cell. The status of the in-progress fabrication and QA testing for each of the major subsystems is described in this paper. The complete system will not be assembled - nd tested in the US. All components of the IVA are to be delivered as subassemblies to AWE in the UK in mid 2012 for assembly and commissioning.

Summary form only given. The Hydrus project will provide an enhancement of the flash radiographic diagnostics available in the Hydrodynamics Department at AWE as part of new facilities for hydrodynamics research. The X-ray sources for the experiments carried out at AWE are provided by focused electron beam diodes driven by pulsed power accelerators. The most attenuating objects to be radiographed require an X-ray spectrum and dose that can only be provided by pulsed power machines operating at 7 to 14 MV. A design for a 14 MV IVA (induction voltage adder) has been completed by L3 Communications Pulse Sciences for AWE and three such machines are about to be manufactured to provide the main radiographic capability in the new facility. Research currently being conducted by AWE and international collaborators aims to also develop improved electron beam diodes to meet the requirements for higher radiographic resolution being demanded. Other experiments performed at AWE require a softer X-ray spectrum and hence a lower voltage pulsed power driver, two of which will be provided in a second area of the same facility. It has been determined that the optimum radiographic source will have a sub-100 ns pulse , a diameter of 1 mm or less, an X-ray dose of at least 15R at 1 metre and an X-ray spectrum end point energy of 1-1.5 MeV. An electron beam diode that has demonstrated performance o f this order is the plasma filled rod pinch driven by the Gamble II accelerator at NRL. After a concept study and discuss ions with possible vendors it has been decided procure two machines similar in performance to Gamble II. They will feature a Marx generator charging a single water pulse forming line which will in turn drive the diode via a 3 ohm water insulated output line.

Summary form only given. For the next generation radiography machines at AWE it is planned to move to an inductive voltage adder (IVA) design running at 14 MV and over 100 kA. The high impedance diodes proposed to be used on this machine, such as the paraxial diode, need 30-40 kA of current. The excess current is currently shed into the vacuum chamber walls by the field shaper situated directly before the diode region. The greater currents and energy of the new IVA machine means that this shed current produces a significant secondary X-ray source which is costly to shield against. These experiments were aimed at moving this secondary source back from near the X-ray diode to a position where it could be more easily dealt with. The X-ray machine Mogul E was used as it has the longest magnetically insulated transmission line (MITL) of the machines at AWE of 4 m. The vacuum envelope is made of two parts, which allows the use of a second current monitor without the need for reworking of the MITL. A new 4" MITL stalk was constructed to accommodate the additional field shaper half way along to dump the excess current, which has the option of different stalks for the diode feed after the current dump.

The trend in environmental legislation is such that primary engine modifications will not be sufficient to meet all future emissions requirements and exhaust aftertreatment technologies will need to be employed. One potential solution that is well placed to meet those requirements is non-thermal plasma technology. This paper will describe our work with some of our partners in the development of a plasma based diesel particulate filter (DPF) and plasma assisted catalytic reduction (PACR) for NOx removal. This paper describes the development of non-thermal plasma technology for the aftertreatment of particulates from a passenger car engine and NOx from a marine diesel exhaust application.

The paraxial diode is the workhorse x-ray source at AWE for flash radiography of hydrodynamic experiments. It uses a gas filled cone to focus a 30-40kA, 5 to 10MV electron beam onto a tantalum target to produce a source 5-7mm across. Future plans for a new hydrodynamics facility at AWE call for this diode to be fielded at a higher voltage on an Inductive Voltage Adder (IVA) machine. The current machines at AWE are based upon Single Pulse Forming Line (SPFL) technology. To gain some experience with IVA technology and paraxial diodes, a series of shots were fired on RITS-3 at Sandia National Labs.Over 30 shots were fired on RITS-3 to optimise and investigate aspects of paraxial diode operation. The main concern with using RITS-3 was the excess current (similar to110kA) that would be dumped into the vacuum envelope and whether it would effect diode performance. The results that were obtained showed that this was not the case. On RITS-3 a best performance of 57R@ 1 m from a 5.7mm spot was recorded, very similar to performance seen on comparable x-ray machines at AWE.

The Atomic Weapons Establishment at Aldermaston, U.K., has a number of pulsed-power-driven flash X-ray machines for diagnosing the hydrodynamics of explosively-driven high-Z materials. The most powerful of these machines is Mogul-E, which operates at about 10 MV and 30 kA, delivering about 450 R @ 1 m in a 5 mm spot. Longer-term plans envisage the upgrading of existing facilities through the construction of a multi-axis Hydrodynamic Research Facility (HRF). It is proposed that the HRF will be furnished initially with three inductive voltage adder (IVA) machines operating at /spl sim/14 MV, each giving 600 R @ 1 m in a 5 mm spot. It is envisaged that, following further research, the outputs will be increased towards 1000 R, with, it is hoped, a reduction in X-ray spot size. More speculative proposals involve increasing the number of machines from 3 to 5, and/or the splitting of the output end of one or more machines to drive more than one X-ray source per machine. An overview of the research programme necessary to achieve these aims is presented.