Activities in the Tower
Construction work continues apace on the ERLP areas in readiness for the arrival of the major accelerator components and cryogenic system. The photograph shows a mix of Daresbury Laboratory staff and contractors who are currently working on shielding, painting, electrical distribution, personnel safety system, heating and mechanical installation. Coordination of the multi-discipline team has been essential to ensure a safe working environment and an efficient programme to meet the demanding project milestones.
Installation
of equipment into the building started with the arrival of the laser from
RAL on February 14th and further installation in the accelerator hall is
scheduled for April, starting with the survey network, which will be essential
to ensure the accurate alignment of the magnets, accelerating modules, vacuum
chambers, diagnostics and optical systems.
All of the major contracts for key components are now placed and an intense
assembly and installation phase, initially in clean rooms located in the
assembly building followed by installation of modules into the ERLP accelerator
hall from June 05 through to February 06.
Custom Laser System Delivered
On February 23rd 2005 , exactly on schedule, a custom laser system, designed
and built by the CLF's Laser R&D Group, was switched on at Daresbury
Laboratory. The beam from the laser will be used to generate short bunches
of electrons for the Energy Recovery Linac Prototype (ERLP) - being constructed
at Daresbury as part of the 4GLS programme.
The photograph shows 4GLS team members (L to R) Graeme Hirst, Marta Divall
and Gary Markey.
The laser produces green light in a train of picosecond long pulses at a rate of 81.25 million per second. This pulse train is then chopped into short bursts. The properties of the laser beam (the energy per pulse, the pulse duration and rate, the shape of the laser spot etc.) need to be widely adjustable, to allow the accelerator scientists to investigate the full range of their machine's capabilities. At the same time the laser must operate stably and reliably for long periods with minimum attention. The overall design has therefore included not just high quality commercial laser components but also tight control of cleanliness, temperature, vibration and electrical noise in the laser's environment.
Gallium Arsenide Photocathode
The
gallium arsenide photocathode which is the darker material on the end of
the stainless steel cylinder the in the photograph, is now at Daresbury ready
to be used as the source of electrons in the ERLP photo-injector. Fay Hannon
and Steve Bennett mounted the wafer under the guidance of the FEL and CEBAF
source groups at Jefferson Lab in December. The cathode and cathode stem
were cleaned with a hydrogen plasma before being inserted into a vacuum tube
for transport to the UK. On a second 
wafer
Fay and Steve practised the activation procedure which is needed for the
cathode to work effectively. Joe Herbert was also at the lab to discuss the
vacuum requirements for the equipment for cathode cleaning and testing at
Daresbury. This has now been designed and ordered.
During the same visit, Gary Markey was instructed in the lengthy and skilled process of polishing cathode components to an ultra-smooth finish to prevent high voltage breakdown in operation. The polishing continued once the components and the mounted cathode wafer safely arrived back in Daresbury.