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Paper	Title	Other Keywords	Page
MO102	Accelerator Layout of the XFEL	linac, electron, photon, undulator	2
	R. Brinkmann DESY, Hamburg
	The X-ray Free Electron Laser XFEL is a 4th generation synchrotron radiation facility based on the SASE FEL concept and the superconducting TESLA technology for the linear accelerator. In February 2003 the German government decided that the XFEL should be realized as a European project and located at DESY/Hamburg. The Ministry for Research and Eduation also announced that Germany is prepared to cover half of the investment and personnel costs of the project. This paper gives an overview of the overall layout and parameters of the facility, with emphasis on the accelerator design, technology and physics.
	Transparencies
MOP72	RF Breakdown in Accelerator Structures: From Plasma Spots to Surface Melting	plasma, electron, simulation, radio-frequency	189
	P.B. Wilson SLAC, Menlo Park, California
	Plasma spots are known to form at field emission sites in regions of high dc or rf electric field. Several mechanisms for the formation of plasma spots in an rf field have been proposed, and one such mechanism which fits experimental data is presented in this paper. However, a plasma spot by itself does not produce breakdown. A single plasma spot, with a lifetime on the order of 30 ns, extracts only a negligible amount of energy from the rf field. The evidence for its existence is a small crater, on the order of 10 microns in diameter, left behind on the surface. In this paper we present a model in which plasma spots act as a trigger to produce surface melting on a macroscopic scale (~0.1 mm2). Once surface melting occurs, a plasma that is capable of emitting several kiloamperes of electrons can form over the molten region. A key observation that must be explained by any theory of breakdown is that the probability of breakdown is independent of time within the rf pulse–breakdown is just as likely to occur at the beginning of the pulse as toward the end. In the model presented here, the conditions for breakdown develop over many pulses until a critical threshold for breakdown is reached.
	Transparencies
TUP87	Technologies of The Peripheral Equipments of The J-PARC DTL1 for the Beam Test	power-supply, linac, proton, quadrupole	480
	K. Yoshino, Y. Fukui, E. Kadokura, T. Kato, C. Kubota, F. Naito, E. Takasaki, H. Tanaka KEK, Ibaraki T. Itou JAERI/LINAC, Ibaraki-ken
	First beam test of the DTL1 was performed in November of 2003 at KEK site. A 30 mA H- beam was successfully accelerated from 3 to 19.7 MeV. In order to prepare the beam test, various peripheral equipments were developed: the electrode plates for connecting the hollow-conductor coil and the power cable were developed since quadrupole electromagnets are built in all DTs (77 sets) of the DTL1, the water-cooled multiconductor copper tube (Control Copper Tube) were used as the power cable from the electrode plate to power supply, and the interlock system assembled by PLCs (Programmable Logic Controller) was also prepared for the surveillance of many cooling channel.
TUP88	CLIC Magnet Stabilization Studies	quadrupole, linac, luminosity, collider	483
	S. Redaelli, R.W. Assmann, W. Coosemans, G. Guignard, D. Schulte, I. Wilson, F. Zimmermann CERN, Geneva
	One of the main challenges for future linear colliders is producing and colliding high energy e+e- beams with transverse spot sizes at the collision point in the nanometre range. Preserving small emittances along several kilometres of linac requires the lattice quadrupoles to be stable to the nanometre level. Even tighter requirements are imposed on the stability of the final focus quadrupoles, which have to be stable to a fraction of the colliding beam size to reliably steer the opposing beams in collision. The Compact LInear Collider (CLIC), presently under investigation at CERN, aims at colliding e+e- beams with a vertical spot size of 0.7 nm, at a centre-of-mass energy of 3 TeV. This requires a vertical stability to the 1.3 nm level for the 2600 linac quadrupoles and to the 0.2 nm level for the two final focus quadrupoles. The CLIC Stability Study has demonstrated for the first time that CLIC prototype quadrupoles can be stabilized to the 0.5 nm level in a normal working area on the CERN site. Detailed tracking simulations show that with this level of stability, approximately 70% of the CLIC design luminosity would be achieved. This paper summarizes the work and the achievements of the CLIC Stability Study.
	Transparencies
TH104	Industrial RF Linac Experiences and Laboratory Interactions	linac, vacuum, proton, electron	569
	M. Peiniger ACCEL, Bergisch Gladbach
	Since more than two decades ACCEL Instruments GmbH at Bergisch Gladbach (formerly Siemens/Interatom) is supplying the worldwide accelerator labs with key components like rf cavities and power couplers, s.c. magnets, insertion devices, vacuum chambers and x-ray beamline equipment. Starting with the design and production of turn key SRF accelerating modules in the late 80th, meanwhile ACCEL is engineering, manufacturing, on site commissioning and servicing complete accelerators with guaranteed beam performance. Today, with a staff of more than 100 physicists and engineers and about the same number of manufacturing specialists in our dedicated production facilities, ACCEL's know how and sales volume in this field has accumulated to more than 2000 man years and several hundred Mio €, respectively. Basis of our steady development is a cooperative partnership with the world leading research labs in the respective fields. As an example, for the supply of a turn key 100 MeV injector linac for the Swiss Light Source, and meanwhile also for the Diamond Light Source as well as for the Australian Synchrotron Project, we established a very fruitful partnership with DESY.
	Transparencies
THP36	Vibration Stabilization of a Mechanical Model of a X-Band Linear Collider Final Focus Magnet	feedback, collider, resonance, linear-collider	684
	J. Frisch, A. Chang, V. Decker, L. Hendrickson, T. Markiewicz, R. Partridge, A. Seryi SLAC, Menlo Park, California E. Eric, L. Eriksson, T. Himel SLAC/NLC, Menlo Park, California
	The small beam sizes at the interaction point of a X-band linear collider require mechanical stabilization of the final focus magnets at the nanometer level. While passive systems provide adequate performance at many potential sites, active mechanical stabilization is useful if the natural or cultural ground vibration is higher than expected. A mechanical model of a room temperature linear collider final focus magnet has been constructed and actively stabilized with an accelerometer based system.
THP71	First Experience with Dry-Ice Cleaning on SRF Cavities	superconductivity, extraction, acceleration	776
	D. Reschke, A. Brinkmann DESY, Hamburg G. Müller BUW, Wuppertal D. Werner IPA, Stuttgart
	The surface of superconducting (s.c.) accelerator cavities must be cleaned from any kind of contaminations, like particles or chemical residues. Contaminations might act as centers for field emission, thus limiting the maximum gradient. Today's final cleaning is based on high pressure rinsing with ultra pure water. Application of dry-ice cleaning might result in additional cleaning potential. Dry-ice cleaning using the sublimation-impulse method removes particulate and film contaminations without residues. As a first qualifying step intentionally contaminated niobium samples were treated by dry ice cleaning. It resulted in a drastic reduction of DC field emission up to fields of 100 MV/m as well as in the reduction of particle numbers. The dry ice jet caused no observable surface damage. First cleaning tests on single-cell cavities showed Q-values at low fields up to 4x1010 at 1.8 K. Gradients up to 32 MV/m were achieved, but field emission still is the limiting effect. Further tests are planned to optimize the dry-ice cleaning technique.