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Rob. Smith, Steve Bibby-Trevor and Mike Cordwell With The Conditioning Resistor Supplied to JLAB
After considerable assistance by scientists and engineers at The Thomas Jefferson National Accelerator Facility in Virginia USA (JLAB), Engineers at Daresbury have finally had an opportunity to redress the balance… if only in a small way, by building a special high Voltage conditioning resistor for JLAB’s new high voltage surface testing facility. Mike Cordwell, one of Daresbury’s senior mechanical designers has dealt on a daily basis with JLAB over mechanical design issues of critical items for the ERLP. ‘JLAB have been unstinting in their efforts to help us with the ERLP, so we were naturally delighted when we were approached to help them’, he said. Staff at Daresbury responded to a request from JLAB to build a conditioning resistor for their new test facility following a recent visit to DL by JLAB staff. The resistor in question is a copy of the one developed for the ERLP photo-injector to limit current during high Voltage conditioning in the event of an unwanted internal discharge. This is exactly the same function required by JLAB on their test rig, where surfaces and preparation techniques for high Voltage electrodes can be tested. The resistor itself is based on a scheme developed by Rob. Smith. It is constructed on a phenolic paper tube core, using eight parallel chains of ten 155 M Ohm resistors in series. They are connected together via a series of nine corona rings, with each end of the resistor chains secured to highly polished aluminium terminals, the total resistance of the assembly being 200M Ohms. Engineer Steve Bibby-Trevor who assembled the resistor is expert in constructing and handling such specialised components for high Voltage assemblies having previously assembled the ERLP photo-injector. ‘It is important to take great care with components used in high voltage systems. The finish of all assemblies must be of the highest standard. This resistor will be used at DC voltages upto 450 kV. Any scratch or misalignment can cause unwanted discharges which can prolong the conditioning process’, he said. The new resistor has now travelled safely to JLAB and will shortly be installed for use. The experimental results from this test facility will further the development of high voltage equipment and techniques, essential for the next generation of photo-injectors for facilities at JLAB and for 4GLS.
Rob. Smith Oct 2007
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