J.A. Clarke

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.

European project to develop a UV/VUV free-electron laser facility on the ELETTRA storage ring☆

Abstract The main features and novel technical aspects of a new European project to integrate a free-electron laser on an existing “third generation” synchrotron radiation user facility are described, including the design of the optical cavity and undulator, the electron beam characteristics and a first assessment of the predicted laser performance.

Operation and performance of a free electron laser oscillator down to 190 nm

We present recent results obtained by the European Free Electron Laser (FEL) project at the ELETTRA storage ring. Coherent and tunable light was produced in the ultraviolet down to below 190 nm, the shortest lasing wavelength obtained so far with a FEL oscillator. The performance of the FEL is described, together with a series of technical solutions that have been adopted on it. These solutions increase its validity as a source for applications, and demonstrate the potential of FEL oscillators to become sources with features in the vacuum ultraviolet.

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.

An ultrashort pulse ultra-violet radiation undulator source driven by a laser plasma wakefield accelerator

Narrow band undulator radiation tuneable over the wavelength range of 150–260 nm has been produced by short electron bunches from a 2 mm long laser plasma wakefield accelerator based on a 20 TW femtosecond laser system. The number of photons measured is up to 9 × 106 per shot for a 100 period undulator, with a mean peak brilliance of 1 × 1018 photons/s/mrad2/mm2/0.1% bandwidth. Simulations estimate that the driving electron bunch r.m.s. duration is as short as 3 fs when the electron beam has energy of 120–130 MeV with the radiation pulse duration in the range of 50–100 fs.

4GLS: a new type of fourth generation light source facility

Consideration is now being given in the UK to the provision of an advanced facility at lower energy to complement the DIAMOND x-ray light source. The proposed solution, 4GLS, is a superconducting energy recovery linac (ERL) with an output energy around 600 MeV, delivering both CW beam currents up to 100 mA and alternatively high charge bunches for FEL applications. Production and manipulation of short electron bunches (fs) is a vital part of the source specification. In addition to beam lines from undulator sources in the ERL recovery path there will be three FELs: two will be oscillator types in the infrared and VUV respectively, and the third will be a high gain system for XUV output. The project is outlined, together with its status and the R&D challenges posed. A funded prototype based on a 50 MeV ERL is also described.

Beamline 14: a new multipole wiggler beamline for protein crystallography on the SRS.

A new multipole wiggler device has been designed for the 2.0 GeV Synchrotron Radiation Source at Daresbury Laboratory in the UK. The nine-pole 2.0 T device will provide radiation for two beamlines dedicated to protein crystallography, one of which will be of high intensity. This article provides details of the design of the two stations and outlines methods being developed to combine dealing with the high heat load from the radiation while allowing both stations to be built as close to the centre of the fan as possible.

COLDDIAG: A Cold Vacuum Chamber for Diagnostics

One of the still open issues for the development of superconducting insertion devices is the understanding of the heat load induced by the beam passage. With the aim of measuring the beam heat load to a cold bore and in order to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. We plan to have access with the same set-up to a number of different diagnostics, so we are implementing: i) retarding field analysers to measure the electron flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. COLDDIAG is built to fit in a short straight section at ANKA, but we are proposing its installation in different synchrotron light sources with different energies and beam characteristics. A first installation in DIAMOND is planned in June 2011. Here we describe the technical design report of this device and the planned measurements with beam.

Completion of the first phase of development of the European UV/VUV free-electron laser at Elettra

Free-electron lasers (FELs) are sources of tuneable, coherent radiation with the potential for producing high peak and average power. Of the various types of FEL, those based on storage rings [ I ] have a combination of characteristics that make them attractive sources for a range of experiments in the UVNUV continuous MHz repetition frequency; synchronization with synchrotron radiation (SR) from the storage ring on a 1: 1 pulse basis; relatively high average power (in the few hundred mW range at present); easily tuneable in wavelength: spatially and longitudinally c o h e r h . A storage ring FEL is also a relatively inexpensive addition to a low-to-medium-energy SR facility, using equipment that for the most part can also be utilized for a conventional SR beamline. The first phase of development of a FEL operating in the UVNUV spectral range on the ELETTRA storage ring has recently been completed. The project [2] received partial funding from the European Community in the framework of a three-year RTD (Research and Technological Development) contract (May 1998 April 2001) involvingsix European laboratories: Sincrotrone Trieste, CEALURE, CLRC-Daresbury Laboratory, the University of Dortmund , ENEAFrascati and MAX-lab. The goals of the project were oriented towards future use of the FEL as a source for experimental activity. The aims were therefore to demonstrate: lasing over a broad spectral range from 350 nm to below 200 nm; extending operation below 200 nm was considered to be of major importance in order to extend the range of scientific possibilities for the utilization of the radiation and to be competitive with respect to conventional laser sources. operation of the laser while continuing to provide synchrotron radiation beams for other users; even though the operational energy and current are lower than that in routine operation (1 GeV rather than 2-2.4 GeV), the FEL mode is still of potential interest for a significant number of beamlines that do

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.