EPAC 2006 - List of Keywords

A B C D E F G H I K L M O P Q R S T U V W X

radio-frequency

Paper	Title	Other Keywords	Page
MOPLS128	Status of the Fatigue Studies of the CLIC Accelerating Structures	CLIC, laser, CERN, target	858
	S.T. Heikkinen, S.T. Heikkinen HUT, Espoo S. Calatroni, H. Neupert, W. Wuensch CERN, Geneva
	The need for high accelerating gradients for the future Compact Linear Collider imposes considerable constraints on the materials of the accelerating structures. The surfaces exposed to high pulsed RF currents are subjected to cyclic thermal stresses possibly resulting in surface break up by fatigue. Since no fatigue data exists in the literature up to very large numbers of cycles, a comprehensive study has been initiated. Low cycle fatigue data (up to 10⁸ cycles) has been collected by means of a pulsed laser surface heating apparatus. The surface damage has been characterized by SEM observations and roughness measurements. High cycle fatigue data (up to 10¹¹ cycles) at various stress ratios have been collected in high frequency bulk fatigue tests using an ultrasonic apparatus. It is found that the appearance of surface fatigue damage in the laser experiments, and of fatigue cracks in the bulk specimen, happen at similar stress levels for similar numbers of cycles. This allows the two experimental techniques to be connected and to predict the surface damage at a high number of cycles. Up-to-date fatigue data for selected high conductivity, high strength Cu alloys are presented.

TUPLS072	Nonscaling FFAG with Equal Longitudinal and Transverse Reference Momenta	lattice, closed-orbit, acceleration, controls	1663
	S.R. Koscielniak TRIUMF, Vancouver
	An unusual feature of linear-field nonscaling FFAG designs is that the radio-frequency is not necessarily synchronous with the reference orbit and momentum chosen for the lattice design. This arises because optics design prefers the reference geometry to be composed of straight lines and arcs of circles - either at the mean momentum, or at high momentum to centre the orbit in the F element. The asynchronous acceleration proposed for rapid acceleration has strong requirements to set the longitudinal reference at 1/4 and 3/4 of the momentum range to minimize phase slip. The usual particle-tracking programs, such as MAD, though sophisticated in the transverse plane, are far cruder in their longitudinal working and do not allow for a longitudinal reference momentum and RF phase independent of the transverse values. In the context of a thin-element lattice model, we show how to make the transverse reference momentum and optic design coincident with the longitudinal reference by adjusting the ratio of positive and negative bending in the D and F elements, respectively, and retaining a lines and arcs composition for the reference orbit. This prepares the way for MAD tracking.

WEOBPA01	First Results of the CRFQ Proof of Principle	rfq, proton, quadrupole, impedance	1873
	D. Davino Universita' degli Studi del Sannio, Benevento L. Campajola Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli V. Lo Destro, A.G. Ruggiero BNL, Upton, Long Island, New York M.R. Masullo INFN-Napoli, Napoli V.G. Vaccaro Naples University Federico II and INFN, Napoli
	The Circular Radiofrequency Quadrupole is a new concept of a storage and accelerator ring for intense beams of light and heavy ions, protons and electrons. It is basically a Linear Radiofrequency Quadrupole completely bent on a circle. The advantages, which are expected to be the same performance features of a linear RFQ, would be smaller overall dimension with respect to accelerators with comparable beam intensity and emittance. A collaboration between BNL and Italian research institute and universities was set up at the end of 2002 with the aim of the proof of the bending principle. The prototype design is based on a 4-rods scheme and have a linear sector followed by a 45-degree curved sector. The 1mA proton beam, produced by a reconditioned RF source, go through a beam gap diameter of 10mm with circular 10mm diameters rods. Each sector is 700mm long and is placed in a 150mm diameter pipe*. The RF power at 202.56MHz is fed by a CERN "Frank James" 50kW amplifier. In this paper the first power and beam tests of the linear sector are presented. A.G. Ruggiero, C-A/AP/65 note, Brookhaven National Laboratory, October 2001. A.G. Ruggiero et al., Proceedings of the EPAC 2004 conference.*D. Davino et al., Proceedings of the EPAC 2004 conference.
	Transparencies

WEPCH147	Simulations of Electron Effects in Superconducting Cavities with the VORPAL Code	electron, simulation, plasma, laser	2269
	C. Nieter, J.R. Cary, P. Messmer, D.S. Smithe, P. Stoltz Tech-X, Boulder, Colorado G.R. Werner CIPS, Boulder, Colorado
	Modeling the complex boundaries of superconducting radio frequency (SRF) accelerating cavities on a Cartesian grid is a challenge for many Finite Difference Time Domain (FDTD) electromagnetic PIC codes. The simulation of such cavities require conformal (curve fitting) boundaries. Modeling the full cavity including couplers and ports is fundamentally a three dimensional problem requiring capability to run in parallel on large numbers of processors. We have recently added conformal boundaries using the method of Zagorodnov* to the plasma simulation code VORPAL. Using this higher order boundary algorithm and the surface physics package TxPhysics, we have begun studies of self-consistent electron effects in SRF cavities. We have modeled the beam excitation of cavity modes and the effects of electron multipacting. Results from these studies will be presented using the new user friendly visualization tool that now ships with VORPAL. *I. A. Zagorodnov et al. “A uniformly stable conformal FDTD-method in Cartesian grids,” International Journal of Numerical Modeling 16, 127 (2003).

WEPLS122	Multiphase Resonant Power Converter for High Energy Physics Applications	controls, power-supply, feedback, klystron	2658
	M.J. Bland, J. Clare, P. W. Wheeler University of Nottingham, Nottingham
	Accelerators used for experiments in high-energy physics require very high power radio frequency sources to provide the energy needed to accelerate the particles. The RF power needs to be stable and predictable such that any variation in the supplied RF power has a limited and acceptable impact on the accelerated beam quality. This paper considers the design of a "long-pulse" modulator supply rated at 25kV, 10A (250kW peak power, duty ratio 10%, 25kW average power, pulse length ≈ 1 − 2ms). The supply is based on direct modulation of a multi-phase resonant power supply, fed by an active rectifier. The objectives of the development are to produce a compact power supply, with low stored energy and with high power quality at the utility supply. The paper provides a brief overview of the technology, followed by a discussion of the design choices. Initial results from the laboratory prototype will be included.

WEPLS123	Initial Experimental Results of a New Direct Converter for High Energy Physics Applications	controls, power-supply, booster, target	2661
	D. Cook, M. Catucci, J. Clare, P. W. Wheeler University of Nottingham, Nottingham C. Oates Areva T&D, Stafford J.S. Przybyla, R. Richardson e2v Technologies, Essex
	This paper presents practical results for a new type of power supply for high energy physics CW applications. The converter is a direct topology operating with a high frequency (resonant) link. Losses are minimised by switching at zero current. High operating frequency reduces the filter and transformer size. The transformer uses the latest nano-crystalline materials to further reduce losses. Where possible, circuit elements are incorporated into the transformer to reduce the physical size of the converter. Design of this transformer to accommodate the insulation, VA rating and circuit elements is non-trivial. The Radio Frequency power generated is stable and predictable, whilst the reduced energy storage in filter components removes the need for crowbar circuits. Potential benefits of this converter when compared to conventional approaches are discussed. These include reduced energy storage, reduced turn-on time and enhanced energy density when compared with existing topologies. Preliminary practical results are promising and are presented along with simulation results.

THPPA02	High-Gradient Superconducting Radiofrequency Cavities for Particle Acceleration	TESLA, DESY, XFEL, acceleration	2752
	L. Lilje DESY, Hamburg
	The development of radiofrequency superconductivity for particle acceleration has reached a level where many projects consider its use. One of the many attractive features of these accelerating structures is to achieve very high accelerating fields efficiently. The technology has been developped to a stage where accelerating gradients of more than 25 MV/m are being implemented in accelerator modules. In single-cell test resonators even higher gradients were already achieved. To operate cavities at these gradients efficiently their frequency needs to be kept stable to reduce the need for an overhead in radiofrequency power. Introducing active elements like piezoelectric actuators allows to achieve these goals.
	Transparencies

THPCH175	Automatic Resonant Excitation Based System for Lorentz Force Compensation for Flash	controls, resonance, DESY, injection	3206
	P.M. Sekalski, A. Napieralski TUL-DMCS, Lodz S. Simrock DESY, Hamburg
	The cavity is the key element of each linear accelerator used for high-energy physics purpose. The resonant frequency of cavities depends on its shape. Due to the pulse operation, they are deformed by dynamic Lorentz force (LF) caused by accelerating electromechanical field. As a consequence, the cavities are not working on resonance but they are detuned from master oscillator frequency by few hundreds of Hertz depending on accelerating field gradient. The paper presents an automatic control system for LF compensation applied to fast tuning mechanism CTS. The active element is multilayer low-voltage piezoelectric stack (EPCOS). The resonant excitation with adaptive feed forward algorithm is used to drive the actuator. Test performed at FLASH (former name VUV-FEL) on cav5/ACC1 showed that detuning during flat-top period (800us) might remain below 10Hz for accelerating field gradient of 20MV/m.