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in subjects: "Resonators 430303* -- Particle Accelerators-- Experimental Facilities & Equipment"

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Development of 400- to 450-MHz RFQ resonator-cavity mechanical designs

In the development of the radio-frequency quadrupole (RFQ) linac, the resonator cavity's mechanical design may be a challenge similar in magnitude to that of the development of the accelerator structure itself. Experience with the all-copper 425-MHz RFQ proof-of-principle linac has demonstrated that the resonator cavity must be structurally stiff and easily tunable. This experience has led to development of copper-plated steel structures having vanes that may be moved within a cylinder for tuni… more

Date: January 1, 1982

Creator: Hansborough, L.D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Resonators for heavily beam-loaded linacs

Capacitively loaded resonant line section accelerating structures are discussed. Prototype models were measured at low levels, and calculations were made to predict high level operation. High current composite beams of multiple-beamlets as accelerated by a MEQALAC were assumed.

Date: April 28, 1980

Creator: Sanders, R.T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Resonant impedance of bellows above cutoff

The perturbation method of Chatard-Moulin and Papiernik is used to calculate the longitudinal and transverse impedances, Z(..omega..) and Z/sub perpendicular/(..omega..), of a bellows. The bellows shape is defined by its radius a(z) = a (1 + epsilons(z)), where a is the mean radius, epsilon a small parameter, and s(z) describes the convolution of the bellows. A finite wall conductivity is considered and the resonant contribution to the impedance above the cutoff frequency of the unperturbed cha… more

Date: January 1, 1980

Creator: Krinsky, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A three-gap klystron output cavity at X-band

A high-power X-band klystron employing a double-gap output cavity has been operating at SLAC. Multi-gap output circuits have lower surface gradients at the interaction gaps than single-gap ones but are prone to self-oscillate due to negative loading and trapped higher-order modes. In the double-gap circuit design, considerable attention had been directed to deal with these stability problems. The performance of the present tube appears to be limited by gap breakdown and beam interception partic… more

Date: March 1, 1992

Creator: Ko, K.; Lee, T.G.; Tonegawa, S. (Stanford Linear Accelerator Center, Menlo Park, CA (United States)) & Kroll, N. (Stanford Linear Accelerator Center, Menlo Park, CA (United States) California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics)

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Discrete cavity model of a standing-wave free-electron laser

A standing-wave free-electron laser (SWFEL) has been proposed for use in a two-beam accelerator (TBA). Unlike a conventional microwave free-electron laser, the SWFEL has a wiggler that is divided by irises into a series of standing-wave cavities, and the beam is reaccelerated by induction cells between cavities. We introduce a one-dimensional discrete-cavity model of the SWFEL. In contrast to the continuum model that has been extensively used to study the device, the new model takes into accoun… more

Date: August 1, 1991

Creator: Rangarajan, G.; Sessler, A. (Lawrence Berkeley Lab., CA (United States)) & Sharp, W.M. (Lawrence Livermore National Lab., CA (United States))

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Stability of klystron operation as a function of input parameters

Instabilities in the operation of a high-power multicavity klystron have been studied as a function of various input parameters. Among these, the focusing magnetic field, rf input power and tuning of the second harmonic cavity were observed to have a striking effect in deciding the regions of unstable operation. One region of instability could be identified with a value of magnetic field corresponding to cyclotron resonance, at the operating frequency. The magnetic field value in the region of … more

Date: March 1, 1984

Creator: Singh, A.; Konrad, G. T. & Griffin, C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Development program for a 200 kW, CW, 110 GHz gyrotron. Quarterly report No. 1, June-September 1979

The objective of this program is the design and development of a millimeter-wave device to produce 200 kW of continuous-wave power at 110 GHz. The device, which will be a gyrotron oscillator, will be compatible with power delivery to an electron-cyclotron plasma. Smooth control of rf power output over a 17 dB range is required, and the device should be capable of operation into a severe time-varying rf load mismatch. Progress toward this goal is described and specifications of the gyrotron are … more

Date: January 1, 1979

Creator: Arnold, K.W.; Tancredi, J.J.; Caplan, M.; Ha, K.W.; Birnbaum, D.N. & Weiss, W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Modeling of a 1700-MHz cluster cavity of planar triodes

In this paper we present the modeling and design of a 1700-MHz cluster-cavity vacuum tube amplifier. We used a three-dimensional, finite-difference code (MAFIA) to characterize the modes that the resonant structure of the amplifier will support. We describe the characteristics of the tube, including performance predictions. 1 ref., 5 figs., 1 tab.

Date: January 1, 1991

Creator: Rees, D.E. & Friedrichs, C. Jr.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Reduction of the beam breakup mode Q values in the ETA/ATA Accelerating Cells

Earlier Microwave Measurements of the ETA Accelerating Cells has uncovered eleven resonances in the frequency range of 0 > 850 MHz. The Q values of these modes ranged from 14 to 70. A three phase program directed at substantially reducing these Q values is reported. In particular the dampening methods described below resulted in a decrease of Q value from 40 to 5 for the beam breakup mode (TM/sub 110/) with a corresponding reduction for most of the other cavity modes.

Date: May 20, 1980

Creator: Birx, D.L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Photon storage cavities

A general analysis is presented of a photon storage cavity, coupled to free-electron laser (FEL) cavity. It is shown that if the coupling between the FEL cavity and the storage cavity is unidirectional (for example, a ring resonator storage cavity) then storage is possible, but that if the coupling is bi-directional then storage is not possible. Parameters are presented for an infra-red FEL storage cavity giving an order of magnitude increase in the instantaneous photon power within the storage… more

Date: August 1, 1991

Creator: Kim, K. J. & Sessler, A. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Performance of an rf beam monitor on the NBS-Los Alamos racetrack microtron

A prototype rf beam-position, current, and phase monitor has been used on the 100-keV injector beamline of the racetrack microtron (RTM) where performance was measured with the chopped and bunched beam. This monitor works with both a pulsed beam and a cw beam. The pulsed beam consists of beam pulses with a FWHM of 40 ns. The rf beam monitor was tested with beam currents from approx. 50 to 600 ..mu..A. The rf beam monitor will be described and its performance will be reported. 6 refs., 5 figs.

Date: January 1, 1985

Creator: Young, L. M. & Cutler, R. I.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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LAMPF 805-MHz accelerator structure tuning and its relation to fabrication and installation

In the course of construction of the 805-MHz linac, it was necessary to set 10,000 resonant cavities to precise frequencies and to check, and in some cases, to adjust the field distribution along the beam axis of the 104 rf tanks composing the linac. Since this was the first proton linac of the side-coupled type ever built, it was necessary to develop new techniques and instrumentation for structure tuning. An outline of the fabrication and installation process is given, showing how the tuning … more

Date: July 1, 1979

Creator: Swain, G.R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Wakeatron: acceleration of electrons on the wake field of a proton bunch

We explore in this note the idea of accelerating a low intensity electron or positron bunch, travelling through a linear rf structure, following at a short distance an intense proton bunch which leaves behind a wake field. This device acts like a transformer where two beams are involved: one made of protons at high current and low energy, the other made of either electrons or positrons, at low current and high energy. The two beams are coupled electromagnetically to each other by a specially de… more

Date: January 1, 1985

Creator: Ruggiero, Alessandro G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Microwave measurements of the ETA accelerating cavity

Microwave measurements of the ETA accelerating cavities have shown eleven resonances in the frequency range of 0 to 850 MHz. These modes have been identified according to their similarity with the modes of a cylindrical cavity. Measurements of the Q's of the modes yielded values from 14 to 70 and transverse shunt impedances (R/sub perpendicular/Q) of 9 to 12..cap omega... In particular, beam breakup mode (TM/sub 110/) has a Q of 20 to 40 and a transverse impedance of 9..cap omega... A later rep… more

Date: March 12, 1980

Creator: Birx, D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Voltage breakdown testing for the radio-frequency quadrupole accelerator

Designs of radio-frequency quadrupole (RFQ) accelerators with reasonable length require operation with surface fields above the limit imposed by Kilpatrick's Criterion. A cavity was designed using SUPERFISH to test the validity of this Criterion and to determine operating limits for the RFQ. The experimental setup and procedure are described, as are the data and results. A method of calibrating the test is presented.

Date: January 1, 1979

Creator: Williams, S. W.; Rodenz, G. W.; Humphry, F. J. & Potter, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Mechanical design considerations in FMIT RFQ development

The mechanical features of the several rf structures that have been made to test the theory of the radio-frequency quadrupole (RFQ) are briefly described. A 425-MHz structure, designed as a proof-of-principle (POP) test, is described in detail. Methods of coupling rf power into the structure, temperature control, tuning, and mode separation are discussed. The methods and setup of N/C machinery used to generate the critical geometry surrounding the RFQ aperture are detailed fully. Finally, the a… more

Date: January 1, 1979

Creator: Fuller, C. W.; Williams, S. W. & Potter, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-Q ferrite-tuned cavity

Rapid cycling proton synchrotrons, such as the proposed LAMPF II accelerator, require approximately 10 MV per turn rf with 17% tuning range near 50 MHz. The traditional approach to ferrite-tuned cavities uses a ferrite which is longitudinally biased (rf magnetic field parallel to bias field). This method leads to unacceptably high losses in the ferrite. At Los Alamos, we are developing a cavity with transverse bias (rf magnetic field perpendicular to the bias field) that makes use of the tensor… more

Date: January 1, 1983

Creator: Carlini, R. D.; Thiessen, H. A.; Potter, J. M. & Earley, L. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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MEQALAC: a new approach to low beta acceleration

An acceleration system is described which allows one to accelerate high currents of ions at very low velocities. The main principle is to utilize an array of electrostatic quadrupoles in an rf linac drift tube, rather than a single magnetic quadrupole, as is usually the case. Because electrostatic quads can be built with very small apertures, relatively high frequencies can be used. A number of examples are given.

Date: June 1, 1979

Creator: Maschke, A.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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High-beta linac structures

Accelerating structures for high-beta linacs that have been and are in use are reviewed in terms of their performance. Particular emphasis is given to room-temperature structures and the disk-and-washer structure. The disk-and-washer structure has many attractive features that are discussed for pulsed high-gradient linacs, for 100% duty-cycle medium-gradient linacs and for high-current linacs requiring maximal amounts of stored energy in the electric fields available to the beam.

Date: January 1, 1979

Creator: Schriber, S.O.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Discontinuity effects on radial cavity transmission lines

Pulse propagation in radial cavity transmission lines such as those found on a radial line accelerator is considered. Specifically, the effects of discontinuities along the line are examined in detail. It is found that previous analyses of such effects have been incorrect, and here two alternate solution techniques are presented. Depending upon the parameters of such a radial line, the discontinuity effects considered here may or may not be significant; however, if they are significant, it is r… more

Date: April 1, 1979

Creator: Seidel, D.B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Buncher cavity resonant at the first and second harmonic

A buncher is an RF accelerator followed by a drift space. Its purpose is to bunch the dc ion source beam into suitable bunches for acceleration in a linac. The voltage in a simple buncher is a sine wave at the linac frequency. A more elaborate wave form can result in increased capture of ion source beam. The cavities discussed here are resonant at 12.5 and 25 MHz, the first and second harmonic of the Argonne National Laboratory (ANL) low beta linac. They will support a wave form which should gi… more

Date: January 1, 1979

Creator: Foss, M.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Experimental and calculated rf properties of the disk-and-washer structure

A detailed study of the disk-and-washer structure using SUPERFISH has shown that the physical geometry can be optimized to make the structure more efficient than previously reported. The calculated ZT/sup 2/ is equal to that of an equivalent LAMPF cavity (neglecting any losses associated with the side-coupler slots) for ..beta.. = 0.6 and is 30% higher for ..beta.. = 1.0. Several techniques for supporting the washer were studied in addition to the conventional ''L'' supports. Two types of suppo… more

Date: January 1, 1979

Creator: Potter, J. M.; Schriber, S. O. & Humphry, F. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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rf system for the Los Alamos free-electron laser (FEL)

The FEL electron linac consists of three buncher cavities: two accelerator cavities and a deflection cavity, each with its own phase-coherent rf source. All sources will be pulsed for 100 ..mu..s at a 1-pps rate. The phase and amplitude stability requirements are +-1/2/sup 0/, and +-1/2%. There are two subharmonic bunchers, each requiring 5 kW at 108.33 MHz. All remaining cavities operate at 1300 MHz. The fundamental buncher requires 5 kW, whereas each of the accelerating cavities requires at l… more

Date: January 1, 1983

Creator: Friedrichs, C.C.; Tallerico, P.J. & Hoffert, W.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Single-cavity double-frequency buncher

A single-cavity buncher has been developed that resonates at both the fundamental and twice the fundamental frequency to form a more nearly ideal bunching voltage waveform in the gap. The cavity utilizes the TM/sub 020/-like mode as the first harmonic of the fundamental TM/sub 010/-like mode. Field distributions on or near the axis, which are seen by the beam, are essentially identical for the two modes. Many beam bunching applications require two bunchers with the harmonic buncher being physic… more

Date: January 1, 1979

Creator: Schriber, S.O. & Swenson, D.A.

Item Type: Article

Partner: UNT Libraries Government Documents Department