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We present a multimode $X$-band rf pulse compression system suitable for a TeV-scale electron-positron linear collider such as the Next Linear Collider (NLC). The NLC main linac operating frequency is 11.424 GHz. A single NLC rf unit is required to produce 400 ns pulses with 475 MW of peak power. Each rf unit should power approximately 5 m of accelerator structures. The rf unit design consists of two 75 MW klystrons and a dual-moded resonant-delay-line pulse compression system that produces a flat output pulse. The pulse compression system components are all overmoded, and most components are designed to operate with two modes. This approach allows high-power-handling capability while maintaining a compact, inexpensive system. We detail the design of this system and present experimental cold test results. We describe the design and performance of various components. The high-power testing of the system is verified using four 50 MW solenoid-focused klystrons run off a common 400 kV solid-state modulator. The system has produced 400 ns rf pulses of greater than 500 MW. 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. We also present data on the processing and operation of this system, which has set high-power records in coherent and phase controlled pulsed rf.

A number of experimental klystrons have been constructed and evaluated at SLAC, KEK and INP, aiming toward output power objectives of 100 and 120 MW at 11.4 GHz (SLAC and KEK respectively) or 150 MW at 14 GHz (INP), with pulse lengths of the order of 1 /spl mu/s. Since RF breakdown is considered to be the principal mechanism limiting power for such tubes, most of the effort has been concentrated on the design of output circuits that reduce RF gradients by distributing fields over a longer region of interaction. Another klystron component receiving emphasis has been the output window, where the approach for future tubes may be to use a circular TEO1-mode, half-wave window. Best results to date in this continuing international effort are: 50 MW with 1 /spl mu/s pulses, using a traveling-wave output circuit (SLAC and INP), and 85 MW with 200 ns. Pulses (SLAC), using two conventional reentrant, but uncoupled, output cavities. At KEK a klystron with a single, but not reentrant, cavity has produced 80 MW in 50 ns pulses. Finally, Haimson has demonstrated 100 MW at 50 ns with a traveling-wave output. This paper addresses primarily the work performed at SLAC during the last two years. >

During the past several years, there has been tremendous progress on the development of the RF system and accelerating structures for a Next Linear Collider (NLC). Developments include high-power klystrons, RF pulse compression systems and damped/detuned accelerator structures to reduce wakefields. In order to integrate these separate development efforts into an actual X-band accelerator capable of accelerating the electron beams necessary for an NLC, we are building an NLC Test Accelerator (NLCTA). The goal of the NLCTA is to bring together all elements of the entire accelerating system by constructing and reliably operating an engineered model of a high-gradient linac suitable for the NLC. The NLCTA will serve as a testbed as the design of the NLC evolves. In addition to testing the RF acceleration system, the NLCTA is designed to address many questions related to the dynamics of the beam during acceleration. In this paper, we will report on the status of the design, component development, and construction of the NLC Test Accelerator. >

An experimental station for an X-band Next Linear Collider has been constructed at SLAC. This station consists of a klystron and modulator, a low-loss waveguide system for RF power distribution, a SLED II pulse-compression and peak-power multiplication system, acceleration sections and beam-line components (gun, pre-buncher, pre-accelerator, focussing elements and spectrometer). An extensive program of experiments to evaluate the performance of all components is underway. The station is described in detail in this paper, and results to date are presented. >

A klystron designed to operate at 11.4 GHz and 440 kV is presently Stanford Linear Accelerator Center's (SLAC's) strongest RF power source candidate for the Next Linear Collider. It is expected to provide 100 MW of RF power with a pulse width of 1 mu s. The authors describe progress in the development of this device including results from single- and double-gap output cavities and various styles of RF output windows. The design parameters for this klystron are shown. Three X-band klystrons have been designed to test various alternatives to RF windows, output cavities, and beam optics. At this time 72-MW RF power has been generated with a pulse width of 100 ns and 35 MW has been generated at 800 ns. >

We describe the fabrication and testing of the RF windows designed to transmit power to the PEP-II 476 MHz cavities. Design choices to maximize the reliability of the window are discussed. Fabrication technologies for the window are described and finite-element analysis of the assembly process is presented. Conditioning and high-power testing of the window are discussed. Design of the coupler assembly including the integration of the window and other components is reported.

Summary form only given. Selecting a mutual fund is a challenging process. Correctly deciding upon the right funds to invest in, or the right companies to invest with, determines how closely one can achieve their financial goals. Since mutual funds, and the companies that manage them, are constantly changing, a tool is needed to help guide the novice through the maze of decisions. This paper presents a model to assist in such critical decisions. It shows how one can base their decisions on a combination of the market trends, the management firm's strengths and weaknesses, and the investor's own personal goals. It then steps through how to evaluate how each of these plays a role in determining which fund, or set of funds, is appropriate for investment. The process presented is intended as a "tool" or "framework" by individuals with diverse goals who are looking for short term, long term, large, or even small investments.

Summary form only given. This paper presents the University Class Scheduling Model specifically designed for the Computer Science department at Portland State University (USA). The approach taken with this paper uses genetic algorithms employing Ward System's GeneHunter with Excel for the PC as the target platform. Excel was selected so that non-programmers could easily modify and expand the model as the needs of the curriculum changes. The paper introduces the genetic model developed to automate this process. Once the theory behind the model's framework is presented, the paper then steps through each of the inputs, results, and constraints required to develop recommended and feasible schedules. This includes constraints for matching faculty to courses, for selecting the day and time a course is offered, for blocking faculty availability so they will not be assigned more than once for a given day and time, and for offering sections specifically in the evening. Each constraint is described in terms of its functionality and is also formulated mathematically. A total of over 600 hours of test suites were executed and evaluated to determine the model's viability.

The use of TE12 in circular waveguide with smooth walls was suggested for low-loss transport of rf signals in multimoded systems [S. G. Tantawi et al., in Advanced Accelerator Concepts: Eighth Workshop, edited by Wes Lawson, AIP Conf. Proc. No. 472 (AIP, New York, 1999), pp. 967–974]. Such systems use the same waveguide to transport different signals over different modes. In this report we detail a series of experiments designed to measure the characteristics of this mode. We also describe the different techniques used to generate it and receive it. The experiments were done at X band around a frequency of 11.424 GHz, the frequency of choice for future linear colliders at X band [The NLC Design Group, Report No. LBNL-PUB-5424, SLAC Report No. 474, Report No. UCRL-ID 124161, 1996; The JLC Design Group, KEK-REPORT-97-1, 1997]. The transportation medium is 55 m of highly overmoded circular waveguide. The design of the joining flanges is also presented.

We present the design and analysis for a set of smooth transitions from rectangular to circular waveguide that preserves their common reflection symmetries. The S-matrix of the transition connects modes of the same symmetry class, and for a sufficiently adiabatic transition preserves their TE (or TM) character. It is then also non-reflecting and, in the absence of degeneracy, its modal connections are one to one and order preserving. This property enables us to carry out all of the RF manipulations in the more easily handled over-moded rectangular waveguide.

The overmoded rf transmission and pulsed power compression system for SLAC’s Next Linear Collider (NLC) program requires a high degree of transmission efficiency and mode purity to be economically feasible. To this end, a number of new, high power components and systems have been developed at X-band, which transmit rf power in the low loss, circular TE01 mode with negligible mode conversion. In addition, a highly efficient SLED-II [1] pulse compressor has been developed and successfully tested at high power at two accelerator test facilities at SLAC. The systems produced a 200 MW pulse with a near-perfect flat-top with pulse widths ranging from 150–245 ns. In this paper we describe the design and test results of a rectangular-to-circular mode converter and the components/transmission systems based on them, as well as the design and measurements of the high power pulse compression systems using SLED-II. We will also describe how these components are being used to efficiently provide high power rf in the NL...

A 10 cm diameter by 5 cm travel plunger tuner was developed for the PEP-II RF copper cavity system. The single cell cavity including the tuner is designed to operate up to 150 kW of dissipated RF power. Spring finger contacts to protect the bellows from RF power are specially placed 8.5 cm away from the inside wall of the cavity to avoid fundamental and higher order mode resonances. The spring fingers are made of dispersion-strengthened copper to accommodate relatively high heating. The design, alignment, testing and performance of the tuner is described.

This paper describes the design and performance of the XL-1 klystron; a 50 MW klystron operating at a frequency of 11.424 GHz for use on the SLAC Next Linear Collider Test Accelerator (NLCTA). Problems associated with the development of high-power rf sources for NLC, and the solutions implemented on XL-1 are discussed.

We have used relativistic klystron technology to extract 290 MW of peak power at 11.4 GHz from an induction linac beam, and to power a short 11.4-GHz high-gradient accelerator. We have measured rf phase stability, field emission, and the momentum spectrum of an accelerated electron beam. An average accelerating gradient of 84 MV/m has been achieved with 80 MW of relativistic klystron power.