14 Feb 2012



The Versatile Electron Linear Accelerator (VELA) at STFC Daresbury Laboratory




The VELA facility at Daresbury is a purpose-built particle accelerator designed to provide a high-quality electron beam for industrial and academic applications. Following a brief commissioning period in 2013 VELA successfully provided beam to several user groups for a variety of experiments. In 2015 VELA was temporarily shut down as part of the front end installation of the CLARA accelerator, which is located immediately adjacent to VELA in the same accelerator hall.

The shutdown period has been utilised to install a novel 400 Hz photoinjector gun on the VELA line. The dedicated diagnostics suite on the VELA line is well suited to characterise this source and includes a transverse deflecting cavity for longitudinal pulse characterisation. This gun also includes a load lock system which allows changing of the photocathode without breaking machine vacuum. This system will initially be used to characterise a variety of photocathode materials (bulk Cu, thin-film Cu and Mg). The outcome of these measurements together with a well-developed underpinning photocathode R&D programme will inform a new generation of particle accelerators, establishing robust cathodes which will have higher quantum efficiency, better beam emittance and lower dark current.

 VELA and CLARA share the same RF and laser infrastructure for the photoinjector and the beam can be made available from either CLARA line or VELA line. The high energy beam (45 MeV) from CLARA front end will be transported through a dogleg to the existing VELA line which supplies two user areas; BA1 (45 MeV) and BA2 (25 MeV); the VELA beam (5 MeV) can also be delivered to both user areas. Longitudinal pulse compression of the CLARA beam is possible using the CLARA-VELA dogleg and opens new experimental possibilities for user groups in BA1.

ASTeC is a beneficiary of the EU Horizon 2020 ARIES programme which provides access for nonUK academic and industrial researchers to the VELA accelerator complex. For qualifying researchers the ARIES programme covers all facility access costs, plus contributions to experiment interfacing hardware and subsistence costs whilst at the facility. ASTeC has secured an allocation of approximately 40 days of VELA access under the programme, to be delivered by 2021.[2]