| Paper |
Title |
Other Keywords |
Page |
| MOP40 |
A Study Of Coupler-Trapped Modes In X-Band Linacs for the GLC/NLC
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simulation, emittance, collider, linac |
129 |
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- R.M. Jones, V.A. Dolgashev
SLAC/ARDA, Menlo Park, California
- Z. Li
SLAC, Menlo Park, California
- J. Wang
SLAC/ARDB, Menlo Park, California
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Each of the X-band accelerating structures for the GLC/NLC consist of 55 cells which accelerate a train of charged particles. The cells are carefully designed to ensure that the transverse wakefield left behind each bunch does not disrupt the trailing bunches. However, unless attention is paid to the design of the fundamental mode coupler, then a dipole mode is trapped in the region of the coupler and cells. This mode can give rise to severe emittance dilution if care is not taken to avoid a region of resonant growth in the emittance. Here, we present results on HFSS simulations, cold test experimental measurements and beam dynamics simulations arising as a consequence of the mode trapped in the coupler. The region in which the trapped mode has little influence on the beam is delineated.
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| MOP64 |
Wire Measurement of Impedance of an X-Band Accelerating Structure
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impedance, dipole, collider, resonance |
165 |
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- N. Baboi
DESY, Hamburg
- G. Bowden, V.A. Dolgashev, R.M. Jones, J. Lewandowski, S.G. Tantawi, J. Wang
SLAC/ARDA, Menlo Park, California
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Several tens of thousands of accelerator structures will be needed for the next generation of linear collders known as the GLC/NLC (Global Linear Collider/Next Linear Collider). To prevent the beam being driven into a disruptive BBU (Beam Break Up) mode or at the very least, the emittance being signifcantly diluted, it is important to damp down the wakefield left by driving bunches to a manageable level. Manufacturing errors and errors in design need to be measurable and compared with predictions. We develop a circuit model of wire-loaded X-band accelerator structures. This enables the wakefield (the inverse transform of the beam impedance) to be readily computed and compared with the wire measurement. We apply this circuit model to the latest series of accelerating for the GLC/NLC. This circuit model is based upon the single-cell model developed in [1] extended here to complete, multi-cell structures.
[1] R.M. Jones et al, 2003, Proc. PAC2003 (also SLAC-PUB 9871)
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| TU201 |
The KEK C-Band RF System for a Linear Collider
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linac, klystron, collider, RF-structure |
256 |
| |
- H. Matsumoto, S. Takeda, S.S. Win, M. Yoshida
KEK, Ibaraki
- H. Baba, T. Shintake
RIKEN Spring-8 Harima, Hyogo
- J-O. Oh
PAL, Pohang
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The C-band (5712 MHz) main linac has been developed just motivated by the urgent and essential physics program at the e+e- linear collider. In total ~8000 accelerating structures and ~4000 klystrons with modulators are needed for 500 GeV C.M. energy. Therefore these units have to meet strict requirements for: high reliability, simplicity, easy operation, reasonable power efficiency and low cost. This list provides a guiding principle and the boundary conditions for our design work. We have already developed the conventional and PPM type 50 MW class C-band klystrons, modulators, and HOM-free accelerator structures. The first high power an rf compressor cavity made of a low thermal expansion material was designed to provide stable operation even with a very high Q of 200 k, it was successfully operated an output rf power of 135 MW at KEK. The C-band linac rf-system will be used for the SASE-FEL project at SPring-8, but it will also serve to verify the design and components, which can eventually be deployed for the main linac rf system in a future linear collider.
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Transparencies
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| TUP50 |
Cumulative Beam Breakup with Time-Dependent Parameters
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focusing, coupling, injection, dipole |
384 |
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- J. R. Delayen
Jefferson Lab, Newport News, Virginia
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A general analytical formalism developed recently for cumulative beam breakup (BBU) in linear accelerators with arbitrary beam current profile and misalignments [1] is extended to include time-dependent parameters such as energy chirp or rf focusing in order to reduce BBU-induced instabilities and emittance growth. Analytical results are presented and applied to practical accelerator configurations.
[1] J. R. Delayen, Phys. Rev. ST Accel. Beams 6, 084402 (2003)
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| TUP54 |
Resistive-Wall Wake Effect in the Beam Delivery System
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single-bunch, focusing, impedance, vacuum |
393 |
| |
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| TUP80 |
A Long-Pulse Modulator for the TESLA Test Facility (TTF)
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klystron, cathode, linac, coupling |
459 |
| |
- W. Kaesler
PPT, Dortmund
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The long-pulse (1.6 ms) klystron modulator for TTF is a hardtube pulser using a Bouncer-circuit for droop compensation. It is built up with new advanced components representing industrial standards. The on-/off switch is a rugged 12 kV IGCT-stack with a fast 4kA turn-off capability. The 100 kJ storage capacitor bank contains only three capacitors with self-healing, segmented PP-foil technology. A new 100 kA solid-state switch based on light triggered thyristors (LTT) replaced the standard ignitrons as crowbar switches. The 300 kW high voltage power supply is based on modern switched mode technology.
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| TUP81 |
Superstrong Adjustable Permanent Magnet for a Linear Collider Final Focus
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permanent-magnet, collider, quadrupole, multipole |
462 |
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| TUP89 |
Static Absolute Force Measurement for Preloaded Piezoelements Used for Active Lorentz Force Detuning System
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resonance, impedance, linac, vacuum |
486 |
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- S. P. Sekalski, A. Napieralski, S. P. Sekalski
TUL, Lodz
- A. Bosotti
INFN/LASA, Segrate (MI)
- M. Fouaidy
IPN, Orsay
- L. Lilje, S. Simrock
DESY, Hamburg
- R. Paparella, P.F. Puricelli
INFN Milano, Milano
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To reach high gradients in pulsed operation of superconducting (SC) cavities an active Lorentz force detuning compensation system is needed. For this system a piezoelement can be used as an actuator (other option is a magnetostrictive device). To guarantee the demanded lifetime of the active element, the proper preload force adjustment is necessary. To determine this parameter an absolute force sensor is needed which will be able to operate at cryogenic temperatures. Currently, there is no calibrated commercial available sensor, which will be able to measure the static force in such an environment. The authors propose to use a discovered phenomenon to estimate the preload force applied to the piezoelement. The principle of the proposed solution based on a shape of impedance curve, which changes with the value of applied force. Especially, the position of resonances are monitored. No need of specialized force sensor and measurement in-situ are additional advantages of proposed method.
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| TUP91 |
Compact Electron-Linac Design Concept for a Gamma Ray Source
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linac, klystron, electron, collider |
492 |
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- K. C. D. Chan, B.E. Carlsten, G. Dale, R. Garnett, C. Kirbie, F.L. Krawczyk, S.J. Russell, T.P. Wangler
LANL, Los Alamos, New Mexico
- E. Wright
CPI, Palo Alto, California
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Gamma-ray sources, particularly sources that are easily transportable, are in high demand for different homeland security applications. We have carried out a review of commercially available electron-linac-based sources, and have investigated alternative compact electron-linac systems that use updated technologies compared with sources that are available commercially. As the results, we propose to develop a new source using an electron linac operating at 17 GHz. It uses a klystron, instead of a magnetron, and a IGBT-switched HV power supply. The source design takes advantages of the advances in X-band linac technology and solid-state HV technology. The higher frequency and upgraded technologies offer smaller size, lighter weight, better efficiency, easier operation, and higher reliability, compared with commercially-available linacs. In this paper, we will describe the source design and our choice of technologies.
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| TUP95 |
Evaluation of Magnetic Field Enhancement Along a Boundary
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dipole, linac, simulation, collider |
501 |
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- Y. Iwashita
Kyoto ICR, Kyoto
- T. Higo
KEK, Ibaraki
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Generally, a cavity has convex corners on its inner surface, where the surface field becomes higher than the average accelerating gradient. This effect has been paid attention not to exceed a criterion only on surfaces that have high electric field gradient. A high magnetic field area, however, sometimes seems harmful on a stable operation too. Such enhancement factors are evaluated in a 2D model to show a feasible crossing angle limit on a convex angle of two surfaces.
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| WE101 |
Gradient Limitations for High-Frequency Accelerators
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collider, plasma, linac, vacuum |
513 |
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- S. Döbert
SLAC, Stanford
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While the physics of gradient limitations in high frequency rf accelerators still lacks a full theoretical understanding, a fairly complete empirical picture has emerged from the experimental work done in the past few years to characterize this phenomenon.Experimental results obtained mostly in the framework of the NLC/GLC project at 11 GHz and from the CLIC study at 30 GHz will be used to illustrate the important trends.The dependence of achievable gradient on pulse length, operating frequency and fabrication materials will be described. Also, the performance results most relevant to linear colliders will be presented in some detail. Specifically, these relate to the requirements that the structures sustain a certain gradient without incurring damaged, and that more importantly, they run reliably at this gradient, with breakdown rates less one in a million pulses. Finally interesting observations concerning the dynamics of breakdowns like spatial and temporal correlations and dark currents will be covered briefly, including the insights they provide into the breakdown mechanism.
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Transparencies
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| TH103 |
Summary of the Argonne Workshop on High Gradient RF
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electron, linac, ion, simulation |
564 |
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- J. Norem
ANL, Argonne, Illinois
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Workshop on High Gradient rf was held at Argonne from October 7 - 9, 2003. This workshop reviewed the problems encountered when a number of accelerator technologies approached the high gradient limits. The aim of the workshop was to involve materials scientists and try to look at trigger mechanisms and surface interactions, in addition to reviewing progress. Talks were presented on superconducting rf, progress with high and low frequency copper cavities, and dielectrics. The focus was on both experimental and theoretical aspects of the problem. The overall picture presented at the workshop will be summarized.
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Transparencies
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| THP34 |
A High-Power Test of an X-Band Molybdenum-Iris Structure
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vacuum, klystron, collider, linac |
678 |
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- W. Wuensch, A. Grudiev, T. Heikkinen, I. Syratchev, T. Taborelli, I. Wilson
CERN, Geneva
- C. Adolphsen
SLAC/NLC, Menlo Park, California
- S. Döbert
SLAC, Stanford
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In order to achieve accelerating gradients above 150 MV/m, alternative materials to copper are being investigated by the CLIC study. The potential of refractory metals has already been demonstrated in tests in which a tungsten-iris and a molybdenum-iris structure reached 150 and 193 MV/m respectively (30 GHz and a pulse length of 15 ns). In order to extend the investigation to the pulse lengths required for a linear collider, a molybdenum-iris structure scaled to X-band was tested at the NLCTA. The structure conditioned to only 65 MV/m (100 ns pulse length) in the available testing time and much more slowly than is typical of a copper structure. However the structure showed no sign of saturation and a microscopic inspection of the rf surfaces corroborated that the structure was still at an early stage of conditioning. The X-band and 30 GHz results are compared and what has been learned about material quality, surface preparation and conditioning strategy is discussed.
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Transparencies
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| THP35 |
Development of a Non-Magnetic Inertial Sensor for Vibration Stabilization in a Linear Collider
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feedback, collider, acceleration, damping |
681 |
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- J. Frisch, A. Chang, V. Decker, L. Hendrickson, T. Markiewicz, R. Partridge, A. Seryi
SLAC, Menlo Park, California
- D. Eric, T. Himel
SLAC/NLC, Menlo Park, California
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One of the options for controlling vibration of the final focus magnets in a linear collider is to use active feedback based on accelerometers. While commercial geophysics sensors have noise performance that substantially exceeds the requirements for a linear collider, they are physically large, and cannot operate in the strong magnetic field of the detector. Conventional nonmagnetic sensors have excessive noise for this application. We report on the development of a non-magnetic inertial sensor, and on a novel commercial sensor both of which have demonstrated the required noise levels for this application.
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Transparencies
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| THP36 |
Vibration Stabilization of a Mechanical Model of a X-Band Linear Collider Final Focus Magnet
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feedback, collider, resonance, site |
684 |
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- 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
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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.
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| THP37 |
Approaches to Beam Stabilization in X-Band Linear Colliders
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feedback, luminosity, linac, ground-motion |
687 |
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- J. Frisch, L. Hendrickson, T. Markiewicz, A. Seryi
SLAC, Menlo Park, California
- P. Burrows, S. Molloy, G. White
Queen Mary University of London, London
- C. Perry
OXFORDphysics, Oxford, Oxon
- T.O. Raubenheimer, T. Thomas
SLAC/NLC, Menlo Park, California
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In order to stabilize the beams at the interaction point, the X-band linear collider proposes to use a combination of techniques: inter-train and intra-train beam-beam feedback, passive vibration isolation, and active vibration stabilization based on either accelerometers or laser interferometers. These systems operate in a technologically redundant fashion: simulations indicate that if one technique proves unusable in the final machine, the others will still support adequate luminosity. Experiments underway for all of these technologies, have already demonstrated adequate performance.
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| THP53 |
Quasi-Optical Components for Future Linear Colliders
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radiation, linac, impedance, alignment |
730 |
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- S. Kuzikov, G. G. Denisov, M. Yu. Shmelyov
IAP, Nizhniy Novgorod
- J.L. Hirshfield
Omega-P, Inc., New Haven, Connecticut
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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.
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| THP59 |
Low Level RF Including a Sophisticated Phase Control System for CTF3
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klystron, linac, collider, beam-loading |
748 |
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- J. Mourier, R. Bossart, J. Nonglaton, I. Syratchev, L. Tanner
CERN, Geneva
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CTF3 (CLIC Test Facility 3), currently under construction at CERN, is a test facility designed to demonstrate the key feasibility issues of the CLIC (Compact LInear Collider) two-beam scheme. When completed, this facility will consist of a 150 MeV linac followed by two rings for bunch-interleaving, and a test stand where 30 GHz power will be generated. In this paper, the work that has been carried out on the linac’s low power RF system is described. This includes, in particular, a sophisticated phase control system for the RF pulse compressor to produce a flat-top rectangular pulse over 1.4 μs.
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| THP60 |
High-Power RF Distribution System for the 8-Pack Project
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collider, diagnostics, vacuum, resonance |
751 |
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- C.D. Nantista
SLAC/ARDB, Menlo Park, California
- D.P. Atkinson
LLNL, Livermore
- J.Q. Chan
SLAC/NLC, Menlo Park, California
- S.Y. Kazakov
KEK, Ibaraki
- D.C. Schultz
SLAC, Menlo Park, California
- S.G. Tantawi
SLAC/ARDA, Menlo Park, California
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The 8-Pack Project at SLAC is a prototype rf system whose goal is to demonstrate the high-power X-band technology developed in the NLC/GLC program. In its first phase, it has reliably produced a 400 ns rf pulse of over 500 MW using a solid-state modulator, four 11.424 GHz klystrons and a dual-moded SLED-II pulse compressor [1]. In Phase 2, the output power of our system has been delivered into the bunker of the NLCTA (Next Linear Collider Test Accelerator) and divided between several accelerating structures, first four and finally eight, for beam acceleration. We describe here the design, cold-test measurements, and processing of this power distribution system. Due to the high power levels and the need for efficiency, overmoded waveguide and components are used. For power transport, the TE 01 mode is used in 7.44 cm and 4.064 cm diameter circular waveguide. Only near the structures is standard WR90 rectangular waveguide employed. Components used to manipulate the rf power include transitional tapers, mode converters, overmoded bends, fractional directional couplers, and hybrids.
[1] S. Tantawi, et al., “Status of High-Power Tests of the Dual-Mode SLED-II System for an X-Band Linear Collider,” FR202, these proceedings.
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| THP67 |
Traveling Wave and Standing Wave Single Cell High Gradient Tests
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vacuum, coupling, simulation, collider |
766 |
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- V.A. Dolgashev
SLAC/ARDB, Menlo Park, California
- Y. Higashi, T. Higo
KEK, Ibaraki
- C.D. Nantista, S.G. Tantawi
SLAC/ARDA, Menlo Park, California
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Accelerating gradient is one of the crucial parameters affecting design, construction and cost of next-generation linear accelerators. Operating accelerating gradient in normal conducting accelerating structures is limited by rf breakdown. In this paper we describe an experimental setup for study of these limits for 11.4 GHz traveling-wave and standing-wave accelerating structures. The setup uses matched mode converters that launch the circular TM01 mode and short test structures. The test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype structures for the Next Linear Collider. Fields elsewhere in the test structures and in the mode converters are significantly lower then in this single cell. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn around time. In this paper we present design considerations and initial experimental data.
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| THP83 |
Measurements of High Order Modes in High Phase Advance Damped Detuned Accelerating Structure for NLC
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dipole, collider, coupling, controls |
791 |
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- N. Khabiboulline, T. Arkan, H. Carter
FNAL, Batavia, Illinois
- G. Linder
University of Illinois at Urbana-Champaign, Urbana, Illinois
- G. Romanov
Fermilab, Batavia, Illinois
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The RF Technology Development group at Fermilab is working together with the NLC and JLC groups at SLAC and KEK on developing technology for room temperature X-band accelerating structures for a future linear collider. We have built several series of structures for high gradient tests. We have also built 150° phase advance per cell, 60 cm long, damped and detuned structures (HDDS or FXC series). Some of these structures will be used for the 8-pack test at SLAC by the end of 2004, as part of the JLC/NLC effort to demonstrate the readiness of room temperature RF technology for a linear collider. HDSS structures are very close to the final design for the linear collider, and it was very interesting to study the properties of high order modes in the structures produced by semi-industrial methods. In this study advanced RF technique and methods developed at Fermilab for structure low power testing and tuning have been used. The results of these measurements are presented in this paper.
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| THP85 |
Test Results of the 3.9 GHz Cavity at Fermilab
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damping, coupling, emittance, collider |
797 |
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| FR101 |
Overview of Linear Collider Test Facilities and Results
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emittance, linac, collider, damping |
827 |
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- H. Hayano
KEK, Ibaraki
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Linear Collider technology will be recommended by the International Technology Recommendation Panel (ITRP) to the International Linear Collider Steering Committee (ILCSC), soon. Towards this recommendation, many efforts of the developments and the output results of each technology have been made to satisfy the requirements of the technical review committee report (TRC). The test facilities of each linear collider design are the place of the key technology demonstration and realization. The overview of the LC test facilities activities and outputs of TTF, NLCTA, ATF/GLCTA and CTF are summarized and reviewed.
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Transparencies
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| FR201 |
Accelerator Control and Global Networks - State of the Art
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controls, feedback, collider, linac |
847 |
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- D.P. Gurd
ORNL, Oak Ridge
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As accelerators increase in size and complexity, demands upon their control systems increase correspondingly. Machine complexity is reflected in complexity of control system hardware and software and careful configuration management is essential. Model-based procedures and fast feedback based upon even faster beam instrumentation are often required. Managing machine protection systems with tens of thousands of inputs is another significant challenge. Increased use of commodity hardware and software introduces new issues of security and control. Large new facilities will increasingly be built by national (e.g. SNS) or international (e.g. a linear collider) collaborations. Building an integrated control system for an accelerator whose development is geographically widespread presents particular problems, not all of them technical. Recent discussions of a “Global Accelerator Network” include the possibility of multiple remote control rooms and no more night shifts. Based upon current experience, observable trends and rampant speculation, this paper looks at the issues and solutions-–-some real, some probable, and some pie-in-the-sky.
*Spallation Neutron Source, ORNL and LANL
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Transparencies
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| FR202 |
Status of High-Power Tests of Dual Mode SLED-II System for an X-Band Linear Collider
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vacuum, collider, linac, coupling |
852 |
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- S.G. Tantawi
SLAC/ARDA, Menlo Park, California
- V.A. Dolgashev, C.D. Nantista
SLAC/ARDB, Menlo Park, California
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We have produced 400 ns rf pulses of greater than 500 MW at 11.424 GHz with an rf system designed to demonstrate technology capable of powering a TeV scale electron-positron linear collider. Power is produced by four 50 MW X-band klystrons run off a common 400 kV solid-state modulator. We present the layout of our system, which includes a dual-moded transmission waveguide system and a dual-moded resonant-line (SLED-II) pulse compression system. Dual-moding of the transmission lines allows power to be directed through a pulse compression path or a bypass path; dual-moding in the pulse compressor allows the delay lines to be about half as long as they otherwise would need to be. We describe the design and performance of various components, including hybrids, directional couplers, power dividers, tapers, mode converters, and loads. These components are mostly overmoded to allow for greater power handling. We also present data on the processing and operation of this system. The power from that system is transported to feed a set accelerator structure. We will present the design and the high power testing data for the overmoded transfer line and the distribution network.
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Transparencies
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