1. Business Case Review (Gateway 1)

Extensive 4GLS documentation was presented for Gateway 1 review in October/November 2002. The review was undertaken by an independent OGC team, chaired by A Quigley (consultant to OGC). The review spanned 4 days, during which 19 representatives of the key stakeholders were interviewed.

The overall project was awarded green status. The conclusions of the report, in their entirety, are as follows:

“The 4GLS provides an opportunity for the UK to take a world lead at the forefront of the science and application of accelerators. Notwithstanding the origins of the project, it was very clear that the thrust of the project is firmly about providing an excellent world class facility.
The Business Case and other material presented are comprehensive and cover (with very few exceptions) what is expected at GR1.

Exemplars of good practice are:

• Excellent consultation with prospective users to improve the proposed project to one generating intense excitement
• Use of an independent risk adviser
• Thoroughly documented case covering science, risk, options and a variety of technical papers
• Status of Project
  Green – the project is on target to succeed but may benefit from the uptake of the recommendations”

Of the recommendations none is classed as critical before proceeding and all are readily implemented.

2. Approval of CSR 2002 spend by RCUK

Following the very supportive Gateway 1 review, RCUK was asked at its meeting in March 2003 to approve the funds required for 4GLS during the CSR2002 period (April 2003 – March 2006). This resulted in the DTI announcement on 2nd April 2003 of £11.5M funding for this period, £3.5M from CLRC and £8M from DTI (via OST).

This will allow the research and development work necessary to produce a design study report for the facility. The R&D work will be based around an ERL prototype, which will allow ultrashort pulses of electrons to be generated, then accelerated in a short section of superconducting linac, before being compressed prior to being passed through a FEL. The electrons would then be returned to the linac for energy recovery before finally being dumped. Concomitant with the accelerator-based activities, technical issues associated with experimental utilisaiton of FELs will be addressed. These include multiple source synchronisation, advanced beamline design, experimental system design, photon beam diagnostics and detectors.

The 4GLS ERL prototype will enable:

• experimental verification of predictions from the computer based electron beam dynamics studies
• work to proceed on photoinjectors, superconducting linac control, electron beam diagnostics and control
• trials on bunch compression/expansion
• work on coherent synchrotron radiation emission
• work on short electron bunch/photon pulse interactions
• trials on energy recovery

In addition to the hands-on experience to be harvested from studies of the individual components, such a facility offers the opportunity of gaining experience in operating and managing these components when interacting as a complex coupled system. Such systems management will be crucial to the successful operation of 4GLS, which will require individual components to be synchronised at femtosecond timescales.

The Gateway 3 decision point for 4GLS is currently at the end of 2005, providing a convenient point to assess the design study phase.