Van der Wiel, M.J.

Paper	Title	Page
MOPLT075	Ideal Waterbag Electron Bunches from an RF Photogun	725
	O.J. Luiten, M.J. Van der Wiel, S.B. van der Geer TUE, Eindhoven F. Kiewiet FOM Rijnhuizen, Nieuwegein M.J. de Loos PP, Soest
	With the implementation of fs mode-locked Ti:Sapphire lasers in high-gradient RF photoguns, a new charged particle acceleration regime has emerged, the so-called pancake regime. Pancake bunches have by definition a restframe length which is much smaller than the bunch radius. This geometry allows a relatively simple, but effective analytical description of the space-charge dominated, critical initial part of the acceleration trajectory. In high-gradient RF photoguns the pancake regime can be relevant up to several MeV. The general opinion is that extremely short bunches should be avoided during the initial stages of the acceleration process, because high space charge densities are always detrimental to the final beam quality. We show that this is not necessarily true: shorter bunches may even lead to better beams.
MOPLT099	NSC KIPT Accelerator on Nuclear and high Energy Physics	761
	I.S. Guk, A. Dovbnya, S.G. Kononenko, A.S. Tarasenko NSC/KIPT, Kharkov J.I.M. Botman, M.J. Van der Wiel TUE, Eindhoven
	One of the main reasons for the outflow of experts in nuclear physics and adjacent areas of science from Ukraine is the absence of modern accelerating facilities, for conducting research in the present fields of interest worldwide in this area of knowledge. A qualitatively new level of research can be achieved by the construction of a new generation accelerator applying the latest developments in the field of electron beam acceleration, in particular on the basis of superconducting accelerating structures of the TESLA type. Such structures may be used for continuous, polarized electron beams, which is crucial e.g. for thin(?) experiments checking modern theoretical models of interactions of nuclear substance, and for beams with high current and extremely short pulses for research in free electron laser and neutron physics. Such a facility will create an opportunity for carrying out research representing the interest of scientists from other countries, which will promote the integration of Ukrainian science into European and worldwide research.
MOPLT100	Magnetic Structure of the NSC KIPT Nuclear-and-high-energy-physics Electron Accelerator	764
	I.S. Guk, A. Dovbnya, S.G. Kononenko, F.A. Peev, A.S. Tarasenko NSC/KIPT, Kharkov J.I.M. Botman, M.J. Van der Wiel TUE, Eindhoven
	Design options of the magnetic structure of a new proposed accelerator facility at NSC KIPT with a continuous-wave electron beam are described. The accelerator represents a recirculator, based on standard TESLA superconducting accelerating sections in one or two straight sections with a length of 5 or 19 meters. The magnetic system is designed on the basis of the magnetic elements of storage ring EUTERPE, transferred by Eindhoven University to NSC KIPT. The focusing and dispersion functions for several design choices of the magnetic structure are reported. Modeling of the beam movement in the accelerator has been carried out; the beam parameters during acceleration and on accelerator output have been calculated.
TUZACH02	Ultra-high Gradient Compact Accelerator Developments	74
	G.J.H. Brussaard, M.J. Van der Wiel TUE, Eindhoven
	Continued development of relatively compact, although not quite 'table-top', lasers with peak powers in the range up to 100 TW has enabled laser-plasma-based acceleration experiments with amazing gradients of up to 1 TV/m. In order to usefully apply such gradients to 'controlled' acceleration, various hurdles need to be overcome. The main one is that of well-synchronized injection into a sub-mm to micron wavelength plasma wave. The talk will describe the various physics regimes of laser wakefield acceleration, and the two classes of experiments being pursued. One is that of atmospheric-density plasmas, non-linear wakefields with extreme gradients (hundreds of GV/m)and 'internal injection' of few-femtosecond electron bunches. A second class involves modest-density plasmas,wakefields of order 1 GV/m and external injection of (sub)-ps bunches. The state-of-the-art of these experiments will be covered, including the progress on plasma waveguiding of TW pulses over many diffraction lengths. The talk will also provide an outlook for the coming few years. This part includes proposed schemes for improvements in the area of injection, such as 'all-optical' injection and injection based on GV/m 'pulsed-DC' photoguns.
	Video of talk
	Transparencies
WEPLT118	Performance of the TU/e 2.6 Cell Rf-photogun in the 'Pancake' Regime	2125
	S.B. van der Geer, G.J.H. Brussaard, O.J. Luiten, M.J. Van der Wiel TUE, Eindhoven G. Pöplau Rostock University, Faculty of Engineering, Rostock M.J. de Loos PP, Soest
	The 2.6 cell rf-photogun currently in operation at Eindhoven University of Technology has been designed as a booster for a 2 MeV semi-DC accelerator with a field of 1 GV/m. In this paper we present GPT simulation results of the TU/e gun, operated without its pre-accelerator, in the low-charge short-pulse regime. The main part of the paper describes detailed calculations of bunch lengthening due to path-length differences and space-charge effects, making use of high-precision field-maps and the newly developed 3D mesh-based space-charge model of GPT. It is shown that with the present set-up bunches can be produced that are well suited for injection into a planned experiment for controlled acceleration in a plasma-wakefield accelerator.