LINAC 2004 - List of Keywords

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

alignment

Paper	Title	Other Keywords	Page
MOP18	Cold-Model Tests and Fabrication Status for J-PARC ACS	coupling, linac, vacuum, simulation	75
	H. Ao, H. Akikawa JAERI/LINAC, Ibaraki-ken K. Hasegawa, A. Ueno JAERI, Ibaraki-ken N. Hayashizaki TIT, Tokyo M. Ikegami, S. Noguchi KEK, Ibaraki V.V. Paramonov RAS/INR, Moscow Y. Yamazaki J-PARC, Ibaraki-ken
	The J-PARC (Japan Proton Accelerator Research Complex) LINAC will be commissioned with energy of 181-MeV using 50 keV ion source, 3 MeV RFQ, 50 MeV DTL and 181 MeV SDTL (Separated DTL) on September 2006. It is planed to be upgraded by using 400 MeV ACS (Annular Coupled Structure), which is a high-beta structure most suitable for the J-PARC, in a few years from the commissioning. The first ACS cavity, which will be used as the first buncher between the SDTL and the ACS, is under fabrication. Detailed design and tuning procedure of ACS cavities has been studied with RF simulation analysis and cold-model measurements. The results of cold-model measurements, fabrication status, and related development items are described in this paper.

MOP36	Preliminary Study on HOM-Based Beam Alignment in the TESLA Test Facility	polarization, dipole, gun, higher-order-mode	117
	N. Baboi, G. Kreps, M. Wendt DESY, Hamburg G. Devanz, R. Paparella CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex O. Napoly CEA/DSM/DAPNIA, Gif-sur-Yvette
	The interaction of the beam with the higher order modes (HOM) in the TESLA cavities has been studied in the past at the TESLA Test Facility (TTF) in order to determine whether the modes with the highest loss factor are sufficiently damped. The same modes can be used actively for beam alignment. At TTF the beam alignment based on the HOM signals is planned to be studied in the first cryo-module, containing 8 accelerating cavities. One of several modes with higher loss factor will be used. Its polarization has to be determined. The options to use single bunches or bunch trains will be analyzed. The results will be discussed in this paper.

MOP42	Linac Alignment and Frequency Tolerances from the Perspective of Contained Emittances for the G/NLC	emittance, simulation, linac, dipole	135
	R.M. Jones SLAC/ARDA, Menlo Park, California
	We maintain the stable progress of a beam consisting of a train of bunched charges, by a careful design of the geometry of the structures [1]. In practice, the next generation of linear colliders will consist of several tens of thousands of X-band accelerating structures and this will entail inevitable errors in the dimensions and alignments of cells -and groups thereof. These errors result in a dilution of the beam emittance and consequently a loss in overall luminosity of the collider. For this reason it is important to understand the alignment tolerances and frequency tolerances that are imposed for a specified emittance budget. Here we specify an emittance dilution of no more than 10% of the initial value and we track the progress of the beam down the linac whilst accelerating structures (and sub-groups thereof) are misaligned in a random manner and at the same time random frequency are incorporated with structures. This results in tolerances in both frequency errors and sets of alignment errors to be imposed on the structures for a specified emittance dilution. [1] R.M. Jones, 1997, SLAC NLC-Note 24.

MOP86	Cold Test Results of the ISAC-II Medium Beta High Gradient Cryomodule	coupling, acceleration, linac, lattice	222
	R.E. Laxdal, Y. Bylinskii, G.S. Clark, K. Fong, A.K. Mitra, R. L. Poirier, B. Rawnsley, T. Ries, I. Sekatchev, G. Stanford, V. Zvyagintsev TRIUMF, Vancouver
	Many proposals (RIA, Eurisol, ISAC-II) are emerging for a new generation of high gradient heavy ion accelerators. The ISAC-II medium beta cryomodule represents the first realized application that encorporates many new techniques to improve the performance over machines presently being used for beam delivery. The machine lattice, compatible with multi-charge acceleration, uses high field (9T) superconducting solenoids with bucking coils for active fringe field compensation. The bulk niobium quarter wave medium beta cavity produces 6 MV/m over an effective length of 18cm with a peak surface field of ~30 MV/m. TRIUMF has developed a mechanical tuner capable of both coarse (kHz) and fine (Hz) frequency adjustments of the cavity. The demonstrated tuner resolution is better than 0.1 μm (0.6 Hz). A new rf coupling loop has been developed that operates at 200 Watts forward power with less than 0.5 Watt of power being added to the helium load. Cold alignment in ISAC-II has been done with rf pick-ups using a stretched wire technique. Finally all cryomodule and testing has been done in a clean environment. The alignment cryogenic, solenoid and rf performance will be presented.
	Transparencies

MOP89	A Wire Position Monitor System for the ISAC-II Cryomodule Components Alignment	linac, vacuum, impedance, acceleration	231
	B. Rawnsley, Y. Bylinskii, G. Dutto, K. Fong, R.E. Laxdal, T. Ries TRIUMF, Vancouver D. Giove INFN/LASA, Segrate (MI)
	TRIUMF is developing ISAC-II, a superconducting (SC) linac. It will comprise 9 cryomodules with a total of 48 niobium cavities and 12 SC solenoids. They must remain aligned at liquid He temperatures: cavities to ±400 μm and solenoids to ±200 μm after a vertical contraction of ~4 mm. A wire position monitor (WPM) system based on a TESLA design has been developed, built, and tested with a prototype cryomodule. The system is based on the measurement of signals induced in pickups by a 215 MHz signal carried by a wire through the WPMs. The wire is stretched between the warm tank walls parallel to the beam axis providing a position reference. The sensors, one per cavity and two per solenoid, are attached to the cold elements to monitor their motion during pre-alignment, pumping and cool down. A WPM consists of four 50 Ω striplines spaced 90° apart. A GaAs multiplexer scans the WPMs and a Bergoz card converts the RF signals to DC X and Y voltages. National Instruments I/O cards read the DC signals. The data acquisition is based on a PC running LabVIEW. System accuracy is ~7 μm. The paper describes system design, WPM calibration and test results.

TUP02	Development of a 352 MHz Cell-Coupled Drift Tube Linac Prototype	coupling, linac, quadrupole, focusing	288
	M. Vretenar, Y. Cuvet, J. Genest, C. Völlinger CERN, Geneva F. Gerigk CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
	At linac energies above 40 MeV, alternative structures to the conventional Drift Tube Linac can be used to increase efficiency and to simplify construction and alignment. In the frame of the R&D activities for the CERN SPL and Linac4, a prototype of Cell-Coupled Drift Tube Linac (CCDTL) at 352 MHz has been designed and built. This particular CCDTL concept is intended to cover the energy range from 40 to 90 MeV and consists of modules of ~5 m length made of 3 or 4-gap DTL tanks linked by coupling cells. The focusing quadrupoles are placed between tanks, and are aligned independently from the RF structure. The CCDTL prototype consists of two half tanks connected by a coupling cell and requires an RF power of 120 kW to achieve the design gradient. RF tests will be made at low and high power, the latter up to a 20% duty cycle. This paper introduces the main features of this CCDTL design, describes the RF and mechanical design of the prototype and presents the first measurement results.

TUP46	A New Control System for the S-DALINAC	electron, target, diagnostics, beam-losses	372
	M. Brunken, W. Ackermann, A. Araz, U. Bonnes, H.-D. Gräf, M. Hertling, A. Karnaukhov, W.F.O. Müller, O. Patalakha, M. Platz, A. Richter, B. Steiner, O. Titze, B. Truckses, T. Weiland TU Darmstadt, Darmstadt
	We will present recent results of the development of a new control system for the superconducting cw electron accelerator S-DALINAC. This system will be based on common industrial standards. Due to the large number of special devices existing to control the beamline, a simple and cheap communication interface is required to replace the current proprietary bus topology. The existing devices will be upgraded by a microcontroller based CAN bus interface as communication path to a control server. The servers themselves may be distributed over the location, giving required applications access to the device parameters through a TCP/IP connection. As application layer protocol for the Client Server communication a special binary protocol and a text protocol based on XML are considered.

TUP69	Precision Alignments of Stripline BPMs with Quadrupole Magnets for TTF2	quadrupole, linac, synchrotron, pick-up	426
	G. Priebe, D. Nölle, M. Wendt, M. Werner DESY, Hamburg
	We report on our alignment setup to calibrate beam position monitors (BPM) with respect to the magnetic axis of the quadrupole magnets used in the warm sections of the TESLA Test Facility (TTF2). The Stripline BPM's are fixed inside the quadrupole magnets. A streched wire measurement was used to calibrate the electrical axis of the BPM wrt. to the magnetic axis of the quadrupole.

TUP77	Status of RF Control System for ISAC II Superconducting Cavities	feedback, controls, linac, resonance	450
	K. Fong, S. Fang, M.P. Laverty TRIUMF, Vancouver
	The rf control system for ISAC II superconducting cavities is a hybrid analogue/digital system using self-excited feedback loop. It has undergone more than a year of testing and improvements have been made to every aspect of the system, including power up sequencing, phase detection, loop regulation, data acquisition as well as communication with EPICS. With a loaded Q of 100,000, amplitude regulation bandwidth of 20 Hz, phase regulation bandwidth of 5 Hz have been achieved.

TUP85	J-PARC Linac Alignment	linac, quadrupole, beam-transport, monitoring	474
	M. Ikegami, C. Kubota, F. Naito, E. Takasaki, H. Tanaka, K. Yoshino KEK, Ibaraki H. Ao, T. Itou JAERI/LINAC, Ibaraki-ken K. Hasegawa, T. Morishita, N. Nakamura, A. Ueno JAERI, Ibaraki-ken
	J-PARC linac consists of a 3 MeV RFQ linac, a 50 MeV DTL (Drift Tube Linac), a 190 MeV SDTL (Separate-type DTL), and a 400 MeV ACS (Annular-Coupled Structure) linac, and its total length is more than 400 m including the beam transport line to the succeeding RCS (Rapid Cycling Synchrotron). In high-current proton accelerators, precise alignment of accelerator components is indispensable to reduce uncontrolled beam loss and beam quality deterioration. In this paper, planned schemes for the linac alignment is presented together with instrumentation for the long-term ground-motion watching.

TH302	End-to-End Beam Simulations for the MSU RIA Driver Linac	linac, emittance, simulation, ion	594
	X. Wu, M. Doleans, D. Gorelov, T.L. Grimm, F. Marti, R.C. York, Q. Zhao NSCL, East Lansing, Michigan
	The Rare Isotope Accelerator (RIA) driver linac proposed by Michigan State University (MSU) will use a 10th sub-harmonic based, superconducting, cw linac to accelerate light and heavy ions to final energies of ≤400 MeV/u with beam powers of 100 to 400 kW. The driver linac uses superconducting quarter-wave, half-wave, and six-cell elliptical cavities with frequencies ranging from 80.5 MHz to 805 MHz for acceleration, and superconducting solenoids and room temperature quadrupoles for transverse focusing. For the heavier ions, two stages of charge-stripping and multiple-charge-state acceleration will be used to meet the beam power requirements and to minimize the requisite accelerating voltage. End-to-end, three-dimensional (3D), beam dynamics simulations from the ECR to the radioactive beam production targets have been performed. These studies include a 3D analysis of multi-charge-state beam acceleration, evaluation of transverse misalignment and rf errors on the machine performance, modeling of the charge-stripping and stripping-chicane performance, and beam switchyard design. The results of these beam dynamics studies will be presented, and further planned beam dynamics studies will be discussed.
	Transparencies

THP16	Engineering and Cryogenic Testing of the ISAC-II Medium Beta Cryomodule	target, vacuum, linac, heavy-ion	630
	G. Stanford, Y. Bylinskii, R.E. Laxdal, B. Rawnsley, T. Ries, I. Sekatchev TRIUMF, Vancouver
	The medium beta section of the ISAC-II Heavy Ion Accelerator consists of five cryomodules each containing four quarter wave bulk niobium resonators and one superconducting solenoid. A prototype cryomodule has been designed and assembled at TRIUMF. The cryomodule vacuum space contains a mu-metal shield, an LN2 cooled, copper, thermal shield, plus the cold mass and support system. This paper will describe the design goals, engineering choices and fabrication and assembly techniques as well as report the results of the initial cold tests. In particular we will summarize the alignment procedure and the results from the wire position monitoring system.

THP38	High Precision Survey and Alignment of Large Linear Accelerators	survey, simulation, target, vacuum	690
	J. Prenting, M. Schlösser DESY, Hamburg J. Green, G. Grzelak, A. Mitra, A. Reichold OXFORDphysics, Oxford, Oxon A. Herty CERN, Geneva
	For the future linear accelerator TESLA the demanded accuracy for the alignment of the components is 0.5 mm horizontal and 0.2 mm vertical, both on each 600 m section. Other accelerators require similar accuracies. These demands can not be fulfilled with open-air geodetic methods, mainly because of refraction. Therefore the RTRS (Rapid Tunnel Reference Surveyor), a measurement train performing overlapping multipoint alignment on a reference network is being developed. Two refraction-free realizations of this concept are being developed at the moment: the first one (GeLiS) measures the horizontal co-ordinates using stretched wires, combined with photogrammetric split-image sensors in a distance measurement configuration. In areas of the tunnel where the accelerator is following the earth curvature GeLiS measures the height using a new hydrostatic leveling system. The second concept (LiCAS) is based on laser straightness monitors (LSM) combined with frequency scanning interferometry (FSI) in an evacuated system. LiCAS measures both co-ordinates with respect to its LSM-beam and is thus suitable for geometrically straight tunnel sections. Both measurement systems will be placed on a train, which could do the reference survey autonomously.

THP41	Development of High RF Power Delivery System for 1300 MHz Superconducting Cavities of Cornell ERL Injector	coupling, insertion, superconductivity, linac	694
	S.A. Belomestnykh, M. Liepe, V. Medjidzade, H. Padamsee, V. Veshcherevich LEPP, Ithaca, New York N.P. Sobenin MEPhI, Moscow
	Development of a 150 kW CW RF power delivery system for 1300 MHz superconducting cavities is under way at Cornell University in collaboration with MEPhI. The system is based on a twin-coupler consisting of two identical coaxial antenna-type couplers derived from the TTF-3 input coupler design. Because the average power is much higher than in the TTF-3 coupler, the required coupling is stronger and we wanted to avoid multipacting phenomena, major changes were made to the prototype design. Presented coupler has completely redesigned cold part and significantly improved cooling of warm bellows. The results of thermal and mechanical stress calculations are reported. The magnitudes and phases of RF fields applied to each side of the twin-coupler must be very close to each other. This imposes very strict requirements upon a power dividing system. These requirements and proposed layout of a system satisfying them are discussed.

THP53	Quasi-Optical Components for Future Linear Colliders	radiation, linac, impedance, linear-collider	730
	S. Kuzikov, G. G. Denisov, M. Yu. Shmelyov IAP, Nizhniy Novgorod J.L. Hirshfield Omega-P, Inc., New Haven, Connecticut
	This paper presents a concept of the quasi-optical RF system for future Ka-band electron-positron linear collider. According to this concept two RF feeding systems are considered: a Delay Line Distribution System (DLDS) and a pulse compressor based on the multi-mirror traveling-wave resonator. The DLDS is based on oversized waveguides. In such waveguides the so-called image multiplication phenomena are used for power launching, extracting, combining, and splitting of waves. Recent low power tests of mode launchers and other DLDS components are discussed. The 34 GHz pulse compressors, based on three and four-mirror resonators, are considered. The tests of the prototypes at a low power level under different modulation methods are discussed. The simulations and tests of mode converters, miter bends, RF loads, and other components, to be necessary for both compression systems, also are resulted.

THP70	Experimental Study of an 805 MHz Cryomodule for the Rare Isotope Accelerator	linac, vacuum, resonance, coupling	773
	T.L. Grimm, S. Bricker, C. Compton, W. Hartung, M. Johnson, F. Marti, J. Popielarski, R.C. York NSCL, East Lansing, Michigan G. Ciovati, P. Kneisel Jefferson Lab, Newport News, Virginia L. Turlington TJNAF, Newport News, Virginia
	The Rare Isotope Accelerator (RIA) driver linac will use superconducting, 805 MHz, 6-cell elliptical cavities with geometric β values of 0.47, 0.61 and 0.81. Each elliptical cavity cryomodule will have four cavities [1]. Room temperature sections between each cryomodule will consist of quadrupole doublets, beam instrumentation, and vacuum systems. Michigan State University (MSU) has designed a compact cryostat that reduces the tunnel cross-section and improves the linac real estate gradient. The cold mass alignment is accomplished with a titanium rail system supported by adjustable nitronic links from the top vacuum plate, and is similar to that used for existing MSU magnet designs. The same concept has also been designed to accommodate the quarter-wave and half-wave resonators with superconducting solenoids used at lower velocity in RIA. Construction of a prototype β=0.47 cryomodule was completed in February 2004 and is presently under test in realistic operating conditions. Experimental results will be presented including: alignment, electromagnetic performance, frequency tuning, cryogenic performance, low-level rf control, and control of microphonics. [1] “Cryomodule Design for the Rare Isotope Accelerator”, T.L. Grimm, M. Johnson and R.C. York, PAC2003, Portland OR (2003)

THP87	Accelerator Structure Bead Pull Measurement at SLAC		803
	J. Lewandowski, G. Bowden, J. Wang SLAC/ARDA, Menlo Park, California R. Miller SLAC, Menlo Park, California
	Microwave measurement and tuning of accelerator structures are important issues for the current and next generation of high energy physics machines. Application of these measurements both before and after high power processing can reveal information about the structure but may be misinterpreted if measurement conditions are not carefully controlled. For this reason extensive studies to characterize the microwave measurements at have been made at SLAC. For the beadpull a reproducible measurement of less than 1 degree of phase accuracy in total phase drift is needed in order to resolve issues such as phase changes due to structure damage during high power testing. Factors contributing to measurement errors include temperature drift, mechanical vibration, and limitations of measurement equipment such as the network analyzer. Results of this continuing effort will be presented.