Smith, S. L.

Paper	Title	Page
MOPC059	BBU Limitations for ERLs	199
	E. Wooldridge, C. D. Beard, P. A. McIntosh, B. D. Muratori, S. L. Smith STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	The BBU threshold in ERLs is a limitation on the maximum beam current due to the interaction of the electron bunches and the Higher Order Modes (HOMs) contained within the RF cavities. Several factors are involved in determining the threshold current; from the cavity the Q, R/Q and degeneracy of the modes all play an important part. From the beam transport the values of the lattice functions α, β and μ have an effect. We will discuss the limits on these variables to provide a BBU current threshold greater than 100 mA for a multiple cavity machine and what will be required to provide higher currents. Also three different cavity profiles were investigated with the aim of reducing the BBU threshold. The TESLA 9-cell cavity was used as a baseline for comparison against possible 7-cell cavity designs, using the TESLA cell shape for their inner cells. The ends of the 7-cell cavities join to different sized beampipes, with radii of 39 mm and 54 mm, to allow the most of the HOMs to propagate to a broadband HOM absorber. Two different beampipe to cavity to transitions were investigated. The optimised 7-cell cavity will be shown to provide an increase in the BBU threshold.
MOPC062	Results from ALICE (ERLP) DC Photoinjector Gun Commissioning	208
	Y. M. Saveliev, D. J. Holder, B. D. Muratori, S. L. Smith STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	The Energy Recovery Linac Prototype (ERLP) DC photoinjector gun has been commissioned and the beam characteristics measured. The gun has demonstrated the nominal ERLP parameters of 350 keV electron energy, 80pC bunch charge and ~140 ps bunch length (at 10% level). The bunch parameters were measured at different bunch charges from 1 pC up to 80 pC. Special attention was given to measurements of the beam transverse emittance (using a movable slit), correlated and uncorrelated energy spread (using an energy spectrometer) and bunch length (using a transverse RF kicker) at each bunch charge. The effect of the 1.3 GHz RF buncher on the bunch length was also investigated. The experimental results are then compared with ASTRA simulations. Experimental results obtained from the investigation of several other issues including the beam characteristics in the presence of field emission from the cathode and in the presence of strong beam halo are also presented and discussed.
TUOAM02	The Status of the Daresbury Energy Recovery Linac Prototype	1001
	D. J. Holder, P. A. McIntosh, S. L. Smith STFC/DL/ASTeC, Daresbury, Warrington, Cheshire N. Bliss STFC/DL, Daresbury, Warrington, Cheshire A. R. Goulden STFC/DL/SRD, Daresbury, Warrington, Cheshire
	This paper provides an update on the progress with the building and commissioning of the Energy Recovery Linac Prototype (ERLP). The past year has seen a number of notable achievements as well as a number of obstacles to overcome. The detailed results from the gun commissioning work are described elsewhere at this conference. ERLP is a 35 MeV technology demonstrator being built as part of the UK's R&D programme to develop its next-generation light source (NLS). It is based on a combination of a DC photocathode electron gun, a superconducting injector linac and a main linac operating in energy recovery mode. These drive an IR-FEL, an inverse Compton Back-Scattering (CBS) x-ray source and a terahertz beamline. The priorities for ERLP are to gain experience of operating a photoinjector gun and superconducting linacs; to produce and maintain high-brightness electron beams; to achieve energy recovery from an FEL-disrupted beam; the development of an electro-optic longitudinal profile monitor and to study challenging synchronisation issues. ERLP will also act as an injector for what will be the world's first non-scaling, Fixed-Field Alternating Gradient (FFAG) accelerator called EMMA.
	Slides
THPP006	Injection and Extraction for the EMMA NS-FFAG	3386
	B. D. Muratori, S. L. Smith, S. I. Tzenov STFC/DL/ASTeC, Daresbury, Warrington, Cheshire C. Johnstone Fermilab, Batavia, Illinois
	EMMA (Electron Machine with Many Applications) is a prototype non-scaling electron FFAG to be hosted at Daresbury Laboratory. NS-FFAGs related to EMMA have an unprecedented potential for medical accelerators for carbon and proton hadron therapy. It also represents a possible active element for an ADSR (Accelerator Driven Sub-critical Reactor). This paper will summarize the design of the extraction and injection transfer lines of the NS-FFAG. In order to operate EMMA, the Energy Recovery Linac Prototype (ERLP) shall be used as injector and the energy will range from 10 to 20 MeV. Because this would be the first non-scaling FFAG, it is important that as many of the bunch properties are studied as feasible, both at injection and at extraction. To do this, a complex injection line was designed consisting of a dogleg to extract the beam from ERLP, a matching section, a tomography section and some additional dipoles and quadrupoles to transport the beam to the entrance of EMMA. Further, an equivalent tomography module was placed in the extraction line together with several other diagnostic devices including the possibility of using a transverse deflecting cavity.
THPP008	Hamiltonian Approach to the Dynamics of Particles in Non-scaling FFAG Accelerators	3392
	B. D. Muratori, S. L. Smith, S. I. Tzenov STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	Starting from first principle the Hamiltonian formalism for the description of the dynamics of particles in non-scaling FFAG machines has been developed. The stationary reference (closed) orbit has been found within the Hamiltonian framework. The dependence of the path length on the energy deviation has been described in terms of higher order dispersion functions. The latter have been used subsequently to specify the longitudinal part of the Hamiltonian. It has been shown that higher order phase slip coefficients should be taken into account to adequately describe the acceleration in non-scaling FFAG accelerators.
THPP009	Injection and Extraction Orbits and Twiss Parameters for the EMMA Ring	3395
	B. D. Muratori, S. L. Smith, S. I. Tzenov STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
	Using the FFEMMAG code, the injection and extraction orbits for the EMMA ring at a variety of injection and extraction energies together with the Twiss parameters to be used for matching have been calculated. The orbits include two kickers together with a septum at both injection and extraction. The FFEMMAG code has been used in conjunction with several scripts so as to be able to scan the parameter space of the two kicker strengths for a section of the EMMA ring. The results confirm the choice of magnet and vacuum pipe apertures as being adequate to operate EMMA from 10 to 20 MeV.
THPP004	EMMA - the World's First Non-scaling FFAG	3380
	T. R. Edgecock STFC/RAL, Chilton, Didcot, Oxon C. D. Beard, J. A. Clarke, C. Hill, S. P. Jamison, A. Kalinin, K. B. Marinov, N. Marks, P. A. McIntosh, B. D. Muratori, H. L. Owen, Y. M. Saveliev, B. J.A. Shepherd, R. J. Smith, S. L. Smith, S. I. Tzenov, E. Wooldridge STFC/DL/ASTeC, Daresbury, Warrington, Cheshire J. S. Berg, D. Trbojevic BNL, Upton, Long Island, New York N. Bliss, C. J. White STFC/DL, Daresbury, Warrington, Cheshire M. K. Craddock UBC & TRIUMF, Vancouver, British Columbia J. L. Crisp, C. Johnstone Fermilab, Batavia, Illinois Y. Giboudot Brunel University, Middlesex E. Keil CERN, Geneva D. J. Kelliher, S. Machida STFC/RAL/ASTeC, Chilton, Didcot, Oxon S. R. Koscielniak TRIUMF, Vancouver F. Meot CEA, Gif-sur-Yvette T. Yokoi OXFORDphysics, Oxford, Oxon
	EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory in the UK and will be the first non-scaling FFAG ever constructed. EMMA will be used to demonstrate the principle of this type of accelerator and study their features in detail. The design of the machine and its hardware components are now far advanced and construction is due for completion in summer 2009.