S. L. Smith

Prospects for a 4th Generation Light Source for the UK

A 4th Generation Light Source (4GLS) forms a major part of the new CASIM (Centre for Accelerator Science, Imaging and Medicine) project that has been proposed to be based at Daresbury Laboratory. Such a light source is envisaged to contain 3 free electron lasers (FELs) that are integrated with a highly optimised low energy synchrotron radiation source. The light source will be optimised to cover the photon energy range of 5 to 100 eV as well as being designed to host a cavity based FEL that would operate in the UV region. A second, linac based, infrared FEL would be placed in the same building thus enabling pump-probe experiments to be carried out with,state, of the art photon flux and brightness. The third FEL would not initially be a user facility but would be a linac based SASE FEL research project with the aim of producing ultra high brightness light in the VUV/SXR region. The primary source of 5 to 100 eV light could either be a storage ring or an energy recovery linac. Both options are presently being studied and a choice will be made by the Autumn of 2001. This paper describes the present concept for the 4GLS project and details the current status of the designs.

Sub‐picosecond X‐rays from CEBAF at Jefferson Lab.

A high brightness sub‐picosecond x‐ray source can be created by installing an undulator at Jefferson Lab’s CEBAF, a nuclear physics electron accelerator. Although the beam current is only 100 microamps, the electron beam has an extremely small emittance and energy spread, with the result that one can produce x‐ray beams tunable over the range 5–30keV with an average brightness quite comparable to beamlines at the Advanced Photon Source (APS) at Argonne National Lab. In addition, with rms bunch lengths measured down to 85 fsecs, peak brightness values are much higher than at the APS. Furthermore, this x‐ray source has similar emittance in both horizontal and vertical directions, (a so‐called round beam) making it of very high potential for many applications. In order to determine if indeed such a source is worth pursuing we present “tuning curve” calculations of peak and average flux and brightness for an undulator on CEBAF. They are compared with similar calculations for a dipole and for undulator‐A at th...

DIAMOND: a UK national light source project

Modifications to the original racetrack lattice concept as used in the feasibility study of the DIAMOND light source project are presented. Double bend achromat structures with both 16 and 20 cells are described, with 4 fold superperiodicity. The production of higher brightness beams through lower emittance is achieved by optics solutions having finite dispersion in the long straights. The implications of insertion device minimum gaps and of the beam energy spread are discussed with reference to the specification of the radiation spectrum required by users.

Recent developments in the DIAMOND storage ring design

The Design Phase of DIAMOND, a 3rd generation light source facility, is currently in progress. Earlier studies of a similar storage ring had found a basic lattice structure with low emittance, good dynamic stability and the flexibility to operate in different modes. The lattice has been further developed to meet the evolving demands of the project, delivering very high brightness radiation over a wide photon energy range. Optimisation of the lattice properties, including those of nonlinear dynamics, is described in detail, together with other general characteristics of the storage ring.

Commissioning of new orbit control and diagnostic facilities on the SRS at Daresbury

New beam diagnostic and steering control facilities on the SRS at Daresbury have recently been installed. Early results from the commissioning of the advanced 16 bit VME based steering control system, tungsten vane photon position monitors and new electron beam pick up processing electronics are presented. A resolution of 1 micron has been achieved on both electron and photon beam monitoring systems. First trails of local vertical automatic position control have taken place. The photon beam has been stabilized to ±5 microns 15 meters from the source over a 24 h period.

PC-based applications programming on the SRS control system

The CERN PC-based ISOLDE control system has been installed at the SRS electron storage ring at Daresbury Laboratory. The use of Windows NT for the control consoles together with PC and VME front-end computers running under several operating systems has resulted in a flexible and reliable system for accelerator control. The implementation and philosophy of control application programs, based around a suite of Microsoft Visual Basic and Excel programs, is described. In particular, the use of Excel to provide adaptable programs online allows rapid generation of new control functions; orbit correction and servoing at the application level are described as examples of this.