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Compact X-band high power load using magnetic stainless steel

Description: We present design and experimental results of a high power X-band load. The load is formed as a disk-loaded waveguide structure using lossy, Type 430 stainless steel. The design parameters have been optimized using the recently developed mode-matching code MLEGO. The load has been designed for compactness while maintaining a band width greater than 300 MHz.
Date: May 1, 1995
Creator: Tantawi, S.G. & Vlieks, A.E.
Partner: UNT Libraries Government Documents Department

IKE: An interactive klystron evaluation program for SLAC linear collider klystron performance

Description: When the new 65 MW klystrons for the SLC were planned, a computer based interlock and data recording system was implemented in the general electronics upgrade. Significant klystron operating parameters are interlocked and displayed in the SLC central control room through the VAX control computer. A program titled ''IKE'' has been written to record klystron operating data each day, store the data in a database, and provide various sorted operating and statistical information to klystron engineers, and maintenance personnel in the form of terminal listings, bar graphs, and special printed reports. This paper gives an overview of the IKE system, describes its use as a klystron maintenance tool, and explains why it is valuable to klystron engineers.
Date: March 1, 1987
Creator: Kleban, S.D.; Koontz, R.F. & Vlieks, A.E.
Partner: UNT Libraries Government Documents Department

Reliability and lifetime predictions of SLC klystrons

Description: The energy upgrade of SLAC, with the first of the new 67 MW SLAC Linear Collider (SLC) klystrons, began over four years ago. Today there are over 200 of these klystrons in operation. As a result, there is a wealth klystron performance and failure information that enables reasonable predictions to be made on life expectancy and reliability. Data from initial tests, follow-up tests and daily operation monitoring on the accelerator is stores for analysis. Presented here are life expectancy predictions with particular emphasis on cathode life. Also, based on this data, we will discuss some of the principal modes of failure. 3 refs., 2 figs.
Date: March 1, 1989
Creator: Allen, M.A.; Callin, R.S.; Fowkes, W.R.; Lee, T.G. & Vlieks, A.E.
Partner: UNT Libraries Government Documents Department

Anomalous electron loading in SLAC 5045 klystron and relativistic klystron input cavities

Description: Recent studies of RF breakup and instability in the SLAC 5045 klystrons have revealed that many production klystrons show loading of the input cavity by low energy electrons even under cold cathode no beam conditions. Sometime after the onset of the RF drive pulse, the input cavity absorbs a portion of the incident RF drive that would otherwise be reflected from the not-beam-loaded cavity. This power absorption is a function of drive level, and of axial magnetic field surrounding the cavity. No power absorption is present when the axial magnetic field is zero. This same phenomenon has been observed in the input cavity of relativistic klystron experiments being conducted as part of the SLAC-LBL-LLNL development program. The phenomenon may be associated with RF breakup and RF instability in SLAC 5045 klystrons, and with unstable pulse shortening in the relativistic klystron experiments. This paper outlines some old and new observations of microwave beam device malfunctions that probably are associated with low energy electron fluxes in the vacuum environments of microwave power devices. 2 refs., 5 figs.
Date: March 1, 1989
Creator: Koontz, R.F.; Fowkes, R.W.; Lavine, T.L.; Miller, R.H. & Vlieks, A.E.
Partner: UNT Libraries Government Documents Department

Recent performance, lifetime, and failure modes of the 5045 klystron population at SLAC

Description: The 65 MW S-Band klystrons (5045) used to power SLC have been in service for over seven years. Currently, 244 of these tubes are in place on the accelerator, operating full power at 120 pulses per second. Enough tubes have now reached end of life, or experienced other failures to allow a good analysis of failure modes, and to project average lifetime for this type of tube. This paper describes the various modes of failure seen in klystrons rammed from SLC service, and provides data on expected lifetime from current production based on accumulated SLC operating experience.
Date: August 1, 1992
Creator: Koontz, R. F.; Lee, T. G.; Pearson, C. & Vlieks, A. E.
Partner: UNT Libraries Government Documents Department

High power rf window and waveguide component development and testing above 100 MW at X-band

Description: SLAC is committed to developing an X-band source capable of producing 100 Megawatt, 1 microsecond pulses to power the next linear collider. The first experience encountered at SLAC in the X-Band Regime above a few Megawatts was in the relativistic klystron program in cooperation with LLNL and LBL. About 280 MW had been transmitted through a variety of waveguide components but at very short pulse widths ({approximately}40 nanseconds) and very low pulse repetition rates. The likelihood of high peak power rf breakdown in most X-band components and especially rf windows increases as the rf pulse length becomes longer. Testing components at peak power levels above that at which they are expected to reliably perform is essential in a development program.
Date: August 1, 1992
Creator: Fowkes, W. R.; Callin, R. S. & Vlieks, A. E.
Partner: UNT Libraries Government Documents Department

Accelerator and rf system development for NLC

Description: 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, prebuncher, preaccelerator, 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.
Date: April 1, 1993
Creator: Vlieks, A. E.; Callin, R. & Deruyter, H.
Partner: UNT Libraries Government Documents Department

Design of a multi-megawatt x-band solid state microwave switch

Description: The authors present design methodology for high power microwave switches. Among all possible applications for such a switch they emphasize the design parameters for application to the pulse compression system associated with the Next Linear Collider (NLC). The switch is based on the excitation of a plasma layer within a silicon wafer by either a laser or an electron beam. They investigate problems associated with high power operation of such a switch. Mainly, they explore solutions to the problems of thermal runaway, avalanche breakdown, photo-emission, and secondary emission. Different design methodologies are presented.
Date: July 1, 1995
Creator: Tantawi, S.G.; Lee, T.G.; Ruth, R.D.; Vlieks, A.E. & Zolotorev, M.
Partner: UNT Libraries Government Documents Department

Performance of the SLAC Linear Collider klystrons

Description: There are now 200 new, high power 5045 klystrons installed on the two-mile Stanford Linear Accelerator. Peak power per klystron averages over 63 MW. Average energy contribution is above 240 MeV per station. Electron beam energy has been measured as high as 53 GeV. Energy instability due to klystron malfunction is less than 0.2%. The installed klystrons have logged over one million operating hours with close to 20,000 klystron hours cumulative operating time between failures. Data are being accumulated on klystron operation and failure modes with failure signatures starting to become apparent. To date, no wholesale failure modes have surfaced that would impair the SLAC Linear Collider (SLC) program.
Date: January 1, 1987
Creator: Allen, M.A.; Fowkes, W.R.; Koontz, R.F.; Schwarz, H.D.; Seeman, J.T. & Vlieks, A.E.
Partner: UNT Libraries Government Documents Department

A semi-automated system for the characterization of NLC accelerating structures

Description: *A system for characterizing the phase shift per cell of a long X-band accelerator structure is described. The fields within the structure are perturbed by a small cylindrical metal bead pulled along the axis. A computer controls the bead position and processes the data from a network analyzer connected to the accelerator section. Measurements made on prototype accelerator sections are described, and they are shown to be in good agreement with theory.
Date: June 1, 1995
Creator: Hanna, S.M.; Bowden, G.B.; Hoag, H.A.; Loewen, R.; Vlieks, A.E. & Wang, J.W.
Partner: UNT Libraries Government Documents Department

Operational experience with SLAC energy upgrade

Description: To produce energies of over 50 GeV for SLC, all klystron stations on the accelerator are being upgraded to produce 250 MeV energy contribution per station. This involves installing new, higher power, longer pulse klystrons, upgrading klystron modulators to provide these higher voltage, longer klystron beam pulses, and a new interlock and protection system. A new VAX based diagnostic system including automated microwave measurements, klystron beam monitors, and modulator performance checks is being implemented. Figure 1 shows a block diagram of the klystron-modulator system. To date, over half of the new klystrons have been installed and tested, the modulator upgrade program has converted 22 sectors (8 stations each) of modulators out of 30, and a four sector sampling of klystrons has been run at full SLC specs, namely 350 kV beam voltage, 3.5 microsecond pulse duration, peak output power in excess of 60 MW, and PRF of 120 pps. This paper discusses the klystron design, modulator design, interlock and diagnostic systems, and the results of the initial operation.
Date: April 1, 1986
Creator: Allen, M.A.; Cassel, R.L.; Dean, N.R.; Konrad, G.T.; Koontz, R.F.; Schwarz, H.D. et al.
Partner: UNT Libraries Government Documents Department

100 MW klystron development at SLAC

Description: A klystron designed to operate at 11.4 GHz and 440 kV is presently 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 microsecond. Many of the conventional tube technologies are being pushed to their limits. High electron beam power densities, rf electric gradients in cavity gaps and stresses on the ceramic rf output windows are among the most severe problems to be dealt with. This paper describes progress in the development of this device including results from single and double gap output cavities and various styles of rf output windows. 6 refs., 3 figs., 1 tab.
Date: May 1, 1991
Creator: Vlieks, A.E.; Callin, R.S.; Caryotakis, G.; Fant, K.S.; Fowkes, W.R.; Lee, T.G. et al.
Partner: UNT Libraries Government Documents Department

Numerical simulation of the SLAC X-100 klystron using RKTW2D

Description: We have performed numerical simulations of the X-100 klystron being developed at Stanford Linear Accelerator Center. The X-100 is being developed as a possible source for the next generation of linear collider, and will be required to produce {approx}100 MW of power for a duration of {approx}800 ns. Our simulations were performed using the simulation programs RKTW1D and RKTW2D, developed at Lawrence Livermore National Laboratory. The codes were used to investigate the operation of the klystron over a wide range of operating conditions. We will present comparisons of the simulation results with experimental results. 3 refs., 5 figs.
Date: May 1, 1991
Creator: Ryne, R.D. (Lawrence Livermore National Lab., CA (USA)) & Vlieks, A.E. (Stanford Linear Accelerator Center, Menlo Park, CA (USA))
Partner: UNT Libraries Government Documents Department

Breakdown phenomena in high power klystrons

Description: In the course of developing new high peak power klystrons at SLAC, high electric fields in several regions of these devices have become an important source of vacuum breakdown phenomena. In addition, a renewed interest in breakdown phenomena for nanosecond pulse, multi-megavolt per centimeter fields has been sparked by recent R and D work in the area of gigawatt RF sources. The most important regions of electrical breakdown are in the output cavity gap area, the RF ceramic windows, and the gun ceramic insulator. The details of the observed breakdown in these regions, experiments performed to understand the phenomena and solutions found to alleviate the problems will be discussed. Recently experiments have been performed on a new prototype R and D klystron. Peak electric fields across the output cavity gaps of this klystron exceed 2 MV/cm. The effect of peak field duration (i.e. pulse width) on the onset of breakdown have been measured. The pulse widths varied from tens of nanoseconds to microseconds. Results from these experiments will be presented. The failure of ceramic RF windows due to multipactor and puncturing was an important problem to overcome in order that our high power klystrons would have a useful life expectancy. Consequently many studies and tests were made to understand and alleviate window breakdown phenomena. Some of the results in this area, especially the effects of surface coatings, window materials and processing techniques and their effects on breakdown will be discussed. Another important source of klystron failure in the recent past at SLAC has been the puncturing of the high voltage ceramic insulator in the gun region. A way of alleviating this problem has been found although the actual cause of the puncturing is not yet clear. The ''practical'' solution to this breakdown process will be described and a possible mechanism ...
Date: March 1, 1988
Creator: Vlieks, A.E.; Allen, M.A.; Callin, R.S.; Fowkes, W.R.; Hoyt, E.W.; Lebacqz, J.V. et al.
Partner: UNT Libraries Government Documents Department

Two-klystron Binary Pulse Compression at SLAC

Description: The Binary Pulse Compression system installed at SLAC was tested using two klystrons, one with 10 MW and the other with 34 MW output. By compressing 560 ns klystron pulses into 70 ns, the measured BPC output was 175 MW, limited by the available power from the two klystrons. This output was used to provide 100-MW input to a 30-cell X-band structure in which a 100-MV/m gradient was obtained. This system, using the higher klystron outputs expected in the future has the potential to deliver the 350 MW needed to obtain 100 MV/m gradients in the 1.8-m NLC prototype structure. This note describes the timing, triggering, and phase coding used in the two-klystron experiment, and the expected and measured net-work response to three- or two-stage modulation.
Date: April 1, 1993
Creator: Farkas, Z. D.; Lavine, T. L.; Menegat, A.; Vlieks, A. E.; Wang, J. W. & Wilson, P. B.
Partner: UNT Libraries Government Documents Department

The Next Linear Collider Test Accelerator's RF Pulse Compression And Transmission

Description: 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* pulse compressor has been developed and successfully tested at high power. The system produced a 200 MW, 250 ns wide pulse with a near-perfect flat-top. In this paper we describe the design and test results of the high power pulse compression system using SLED-II. The NLC rf systems use low loss highly over-moded circular waveguides operating in the TE01 mode. The efficiency of the systems is sensitive to the mode purity of the mode excited inside these guides. We used the so called flower petal mode transducer [2] to excite the TE01 mode. This type of mode transducer is efficient, compact and capable of handling high levels of power. To make more efficient systems, we modified this device by adding several mode selective chokes to act as mode purifiers. To manipulate the rf signals we used these modified mode converters to convert back and forth between over-moded circular waveguides and single-moded WR90 rectangular waveguides. Then, we used the relatively simple rectangular waveguide components to do the actual manipulation of rf signals. For example, two mode transducers and a mitered rectangular waveguide bend comprise a 90 degree bend. Also, a magic tee and four mode transducers would comprise a four-port-hybrid, etc. We will discuss the efficiency of an rf transport system based on the above methodology. We also used this methodology in building the SLEDII pulse compression system. At SLAC we built 4 ...
Date: September 14, 2011
Creator: Tantawi, S.G.; Adelphson, C.; Holmes, S.; Lavine, Theodore L.; Loewen, R.J.; Nantista, C. et al.
Partner: UNT Libraries Government Documents Department

Recent Measurements And Plans for the SLAC Compton X-Ray Source

Description: A compact source of monoenergetic X-rays, generated via Compton backscattering, has been developed in a collaboration between U.C Davis and SLAC. The source consists of a 5.5 cell X-band photoinjector, a 1.05 m long high gradient accelerator structure and an interaction chamber where a high power (TW), short pulse (sub-ps) infrared laser beam is brought into a nearly head-on collision with a high quality focused electron beam. Successful completion of this project will result in the capability of generating a monoenergetic X-ray beam, continuously tunable from 20 - 85 keV. We have completed a series of measurements leading up to the generation of monoenergetic X-rays. Measurements of essential electron beam parameters and the techniques used in establishing electron/photon collisions will be presented. We discuss the design of an improved interaction chamber, future electro-optic experiments using this chamber and plans for expanding the overall program to the generation of Terahertz radiation.
Date: February 14, 2006
Creator: Vlieks, A.E.; Akre, R.; Caryotakis, G.; DeStefano, C.; Frederick, W.J.; Heritage, J.P. et al.
Partner: UNT Libraries Government Documents Department


Description: In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test stand is being developed to investigate accelerator optimization for future upgrades. This test stand will enable work to explore the science and technology paths required to boost the current 10 Hz monoenergetic gamma-ray (MEGa-Ray) technology to an effective repetition rate exceeding 1 kHz, potentially increasing the average gamma-ray brightness by two orders of magnitude. Multiple bunches must be of exceedingly high quality to produce narrow-bandwidth gamma-rays. Modeling efforts will be presented, along with plans for a multi-bunch test stand at LLNL. The test stand will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. The photoinjector will be a high gradient standing wave structure, featuring a dual feed racetrack coupler. The accelerator will increase the electron energy so that the emittance can be measured using quadrupole scanning techniques. Multi-bunch diagnostics will be developed so that the beam quality can be measured and compared with theory. Design will be presented with modeling simulations, and layout plans.
Date: May 12, 2010
Creator: Marsh, R A; Anderson, S G; Barty, C P; Chu, T S; Ebbers, C A; Gibson, D J et al.
Partner: UNT Libraries Government Documents Department

High-gradient studies on 11.4 GHz copper accelerator structures

Description: This paper is a progress report on studies carried out at SLAC to assess the high-gradient behavior of 11.4 GHz copper accelerator structures for future linear colliders. the structures which have been examined in the last year are a 7-cavity standing-wave (SW) section and a 30-cavity traveling-wave (TW)section. Both structures are of the constant-impedance uniform-aperture type with a 2{mu}/3 phase shift per cavity. The results presented here included new information on RF breakdown, field emission, RF processing and dark current. the captured dark current depends on the rise time of the RF pulse.
Date: August 1, 1992
Creator: Wang, J. W.; Curry, R. A.; Deruyter, H.; Hoag, H. A.; Koontz, R. F.; Loew, G. A. et al.
Partner: UNT Libraries Government Documents Department

High gradient electron guns

Description: Experiments have been conducted to determine peak operating gradients attainable in thermionic electron guns. These tests are part of a study of high-current-density, long-life cathodes suitable for use in high power klystrons. We also investigated the use of chromium oxide coating as a means of inhibiting electronic breakdown across the focus electrode anode gap. Field gradients in excess of 280 kV/cm have been achieved for a gun operating at 240 kV with a beam current of 228 A, at pulse widths of the order of 1 {mu}s. 3 refs., 5 figs.
Date: August 1, 1990
Creator: Fant, K.S.; Caryotakis, G.; Koontz, R.F.; Vlieks, A.E. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)) & Miram, G. (Miram (G.), Atherton, CA (USA))
Partner: UNT Libraries Government Documents Department

High-power rf pulse compression with SLED-II at SLAC

Description: Increasing the peak rf power available from X-band microwave tubes by means of rf pulse compression is envisioned as a way of achieving the few-hundred-megawatt power levels needed to drive a next-generation linear collider with 50--100 MW klystrons. SLED-II is a method of pulse compression similar in principal to the SLED method currently in use on the SLC and the LEP injector linac. It utilizes low-los resonant delay lines in place of the storage cavities of the latter. This produces the added benefit of a flat-topped output pulse. At SLAC, we have designed and constructed a prototype SLED-II pulse-compression system which operates in the circular TE{sub 01} mode. It includes a circular-guide 3-dB coupler and other novel components. Low-power and initial high-power tests have been made, yielding a peak power multiplication of 4.8 at an efficiency of 40%. The system will be used in providing power for structure tests in the ASTA (Accelerator Structures Test Area) bunker. An upgraded second prototype will have improved efficiency and will serve as a model for the pulse compression system of the NLCTA (Next Linear Collider Test Accelerator).
Date: April 1, 1993
Creator: Nantista, C.; Kroll, N. M.; Farkas, Z. D.; Lavine, T. L.; Menegat, A.; Ruth, R. D. et al.
Partner: UNT Libraries Government Documents Department

An X-Band Gun Test Area at SLAC

Description: The X-Band Test Area (XTA) is being assembled in the NLCTA tunnel at SLAC to serve as a test facility for new RF guns. The first gun to be tested will be an upgraded version of the 5.6 cell, 200 MV/m peak field X-band gun designed at SLAC in 2003 for the Compton Scattering experiment run in ASTA. This new version includes some features implemented in 2006 on the LCLS gun such as racetrack couplers, increased mode separation and elliptical irises. These upgrades were developed in collaboration with LLNL since the same gun will be used in an injector for a LLNL Gamma-ray Source. Our beamline includes an X-band acceleration section which takes the electron beam up to 100 MeV and an electron beam measurement station. Other X-Band guns such as the UCLA Hybrid gun will be characterized at our facility.
Date: September 7, 2012
Creator: Limborg-Deprey, C.; Adolphsen, C.; Chu, T.S.; Dunning, M.P.; Jobe, R.K.; Jongewaard, E.N. et al.
Partner: UNT Libraries Government Documents Department