| Paper |
Title |
Page |
| MOP40 |
A Study Of Coupler-Trapped Modes In X-Band Linacs for the GLC/NLC
|
129 |
| |
- R.M. Jones, V.A. Dolgashev
SLAC/ARDA, Menlo Park, California
- Z. Li
SLAC, Menlo Park, California
- J. Wang
SLAC/ARDB, Menlo Park, California
|
|
| |
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.
|
|
| MOP64 |
Wire Measurement of Impedance of an X-Band Accelerating Structure
|
165 |
| |
- N. Baboi
DESY, Hamburg
- G. Bowden, V.A. Dolgashev, R.M. Jones, J. Lewandowski, S.G. Tantawi, J. Wang
SLAC/ARDA, Menlo Park, California
|
|
| |
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)
|
|
| THP33 |
Progress toward NLC/GLC Prototype Accelerator Structures
|
675 |
| |
- J. Wang, G. Bowden, V.A. Dolgashev, R.M. Jones, J. Lewandowski, C.D. Nantista, S.G. Tantawi
SLAC/ARDA, Menlo Park, California
- C. Adolphsen, D.L. Burke, J.Q. Chan, J. Cornuelle, S. Döbert
SLAC/NLC, Menlo Park, California
- T. Arkan, C. Boffo, H. Carter, N. Khabiboulline
FNAL, Batavia, Illinois
- N. Baboi
DESY, Hamburg
- D. Finley, I. Gonin, S. Mishra, G. Romanov, N. Solyak
Fermilab, Batavia, Illinois
- Y. Higashi, T. Higo, T. Kumi, Y. Morozumi, N. Toge, K. Ueno
KEK, Ibaraki
- Z. Li, R. Miller, C. Pearson, R.D. Ruth, P.B. Wilson, L. Xiao
SLAC, Menlo Park, California
|
|
| |
The accelerator structure groups for NLC (Next Linear Collider) and GLC (Global Linear Colliders) have successfully collaborated on the research and development of a major series of advanced accelerator structures based on room-temperature technology at X-band frequency. The progress in design, simulation, microwave measurement and high gradient tests are summarized in this paper. The recent effort in design and fabrication of the accelerator structure prototype for the main linac is presented in detail including HOM (High Order Mode) suppression and couplers, fundamental mode couplers, optimized accelerator cavities as well as plans for future structures. We emphasize techniques to reduce the field on the surface of the copper structures (in order to achieve high accelerating gradients), limit the dipole wakefields (to relax alignment tolerance and prevent a beam break up instability) and improve shunt impedance (to reduce the RF power required).
|
|
| TUP56 |
Simulation of RF Breakdown Effects on NLC Beam
|
396 |
| |
- V.A. Dolgashev
SLAC/ARDB, Menlo Park, California
- T.O. Raubenheimer
SLAC/NLC, Menlo Park, California
|
|
| |
The linacs of the Next Linear Collider (NLC) will contain several thousand traveling wave X-Band accelerator structures operating at input power of about 60 MW. At this input power prototypes of NLC structures have breakdown rates lower than one breakdown in ten hours. RF breakdowns disrupt flow of energy inside the structure and create arcs with electron and ion currents. Electromagnetic fields of these currents interact with the NLC beam. We simulated deflection of the NLC beam caused by breakdown currents using the particle-in-cell code MAGIC. In this paper we present modeling considerations and simulation results.
|
|
| THP67 |
Traveling Wave and Standing Wave Single Cell High Gradient Tests
|
766 |
| |
- 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
|
|
| |
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.
|
|
| FR202 |
Status of High-Power Tests of Dual Mode SLED-II System for an X-Band Linear Collider
|
852 |
| |
- S.G. Tantawi
SLAC/ARDA, Menlo Park, California
- V.A. Dolgashev, C.D. Nantista
SLAC/ARDB, Menlo Park, California
|
|
| |
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.
|
|
|
Transparencies
|