Recent results on electron loading in superconducting cavities are presented and are compared with observations in dc field emission.

... warfare, joint planning, national and international ... of disk-loaded accelerator structure three ... Descriptors : (*PARTICLE ACCELERATORS, CAVITY ...

A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of accelerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole ...

A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second ...

A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second ...

Acceleration of charged particles by the wake fields excited in the elliptical cavity by an intense, short electron bunch is investigated. Two cavities are considered as a wake-field device: disk-loaded and dielectric-loaded. Analytical methods are developed to evaluate the wake ...

... changes, acceleration current and magnetic fields ... facets defined by partially reflective mirrors, supplemented by ... fed back through the mirror into the ...

The PHERMEX accelerator is a standing wave, 50 MHz rf linear accelerator. The rf fields in three cavities are pulsed for a period of 3 ms. The experiments described are directed toward studying injection and trapping of electron rings at modes field stren...

Discussions are given of the general arrangements of the injection system, the principles of the Alvarez structure of the proton accelerator, the ion source, the 500-kev pre-accelerator, beam focusing between the source and the accelerator, the beam buncher, beam steering coils and apertures, the linear ...

We consider an axisymmetric microwave cavity for an accelerator structure whose eigenfrequency for its second lowest TM-like axisymmetric mode is twice that of the lowest such mode, and for which the fields are asymmetric along its axis. In this cavity, the peak amplitude of the rf electric ...

A collaboration between KEK and CEBAF is pursuing the development of a superconducting high gradient accelerating structure for application in future accelerator which optimally requires the high field gradient above 25 MV/m. In the first phase of this collaboration three single cell 1300 MHz niobium cavities have ...

Funnels are a key component of accelerator structures proposed for transmutation technologies. In addition to conventional accelerator elements, specialized rf-cavities are needed for these structures. Simulations were done to obtain their electromagnetic field distribution and to minimize the rf-induced heat ...

The RF control system for a charged-particle accelerator must maintain the correct amplitude and phase of RF field inside the accelerator cavity in the presence of perturbations, noises, and time varying system components. For an accelerator with heavy be...

The proposed superconducting linear accelerator that accelerates muons from 190 MeV to 2.45 GeV will use superconducting solenoids for focusing the muon beam. The accelerator will use superconducting RF cavities. These cavities are very sensitive to stay magnetic field from ...

The method for measuring thresholds and nominal values of RF fields in the linac cavities is proposed. Some peculiarities of measuring these parameters are considered. The threshold values of RF fields in the accelerator initial part (AIP) are measured. b...

This note discusses the effect of SLED cavity temperature changes and resulting cavity detuning on the effective accelerating field delivered by the linac. This effect is of interest because the power dissipated in the SLED cavities depends on the repetition rate at which the linac operates and ...

Limitations on the maximum achievable accelerating gradient of microwave cavities can strongly influence the performance, length, and cost of particle accelerators. Gradient limitations are widely believed to be initiated by electron emission from the cavity surfaces. Here, we show that the deleterious effects of ...

Voltage breakdown is one of the major limiting factors in the design of a high accelerating gradient linear accelerator structure. A multiple-use cavity test system was developed to establish the criteria for voltage breakdown in S-band pulsed electron linear accelerator cavities, in terms of ...

A superconducting third harmonic 3.9 GHz accelerating cavity was proposed to improve the beam quality in the TTF-like photoinjector [1]. Fermilab has developed, built and tested several prototypes, including two copper 9-cell cavities, one niobium 3-cell cavity, and one 9-cell cavity. The ...

CCL cavities are figures of revolution about the beam axis. An automated tuning program sets up the geometry for a symmetric accelerating cavity and runs SUPERFISH repetitively, varying the geometry to tune each cavity to the desired frequency for the electromagnetic fields. SUPERFISH solves ...

High order modes have been successfully damped in the existing NSLS accelerating cavities by the insertion of damping antennae. The location of the antennae was aided by cavity field plots using superfish and their lengths determined experimentally. A description of their construction is presented together with the ...

The progress of the Separated Function RFQ (SFRFQ) accelerator, which can raise the field gradient of acceleration while maintaining the transverse focusing power sufficient for high current beam, is presented. In order to demonstrate the feasibilities of the novel accelerator, a prototype ...

The PHERMEX accelerator is a three-cavity rf linac that operates at 50 MHz. Each cavity has a radius of 2.3 m and a length of 2.6 m. The accelerator produces an electron beam with a peak current of 500 A and energy of 30 MeV. The rf power is supplied by multiple 2.5-MW tetrodes feeding coaxial lines with loops in ...

Two-dimensional simulations of loading effects in a 350 MHz accelerator cavity have been performed. Electron currents of 1-10 kA have been accelerated in 5 MV/m fields. Higher order cavity modes induced by the beam may lead to emittance growth. Operation in an autoaccelerator mode has been ...

Two-dimensional simulations of loading effects in a 350 MHz accelerator cavity have been performed. Electron currents of 1-10 kA have been accelerated in 5 MV/m fields. Higher order cavity modes induced by the beam may lead to emittance growth. Operation ...

Field stability and tuning are critically important for the design of any accelerator. The standing wave structure is under consideration for implementation in the Next Linear Collider. A 15-cavity standing wave accelerator structure was modeled with equivalent circuits in which nearest neighbor coupling was ...

The proposed linear electron-positron collider TESLA is based on 1.3 GHz superconducting niobium cavities for particle acceleration. For a center-of-mass energy of 500 GeV an accelerating field of 23.4 MV/m is required which is reliably achieved with a niobium surface preparation by chemical etching. An upgrade of ...

A periodically Higher Order Mode (HOM) damped RF cavity is a weakly coupled multi-cell RF cavity with HOM couplers periodically mounted between the cells. It was studied as an alternative RF structure between the single cell cavity and superstructure cavity in high beam current application requiring strong damping ...

The superconducting CH structure is a novel multicell cavity for the acceleration of protons and ions in the low and intermediate energy regime. The CH structure is a cross-bar-type cavity; it is the first superconducting low energy multicell cavity operated in an H mode. A superconducting CH-prototype ...

In a wake field accelerator a high current driving bunch injected into a structure or plasma produces intense induced fields, which are in turn used to accelerate a trailing charge or bunch. The basic concepts of wake field acceleration are described. Wake potentials for ...

An electronic oscillator is described for energizing a resonant cavity and to a system for stabilizing the operatin g frequency of the oscillator at the particular frequency necessary to establish a particular preferred field configuration or mode in the cavity, in this instance a linear accelerator. A ...

GN jets produce low density cavities in clusters of galaxies. Stability requires the presence of magnetic fields. We find self-consistent analytical structure of cavities containing large-scale electromagnetic fields and plasma expanding self-similarly. These solutions have no surface currents and, thus, are ...

One of the requirements of the HISTRAP RF accelerating system is that the frequency of the accelerating voltage for the cavity must keep in step with the change in the magnetic field. As the energy of the particle increases, the magnetic field is increase...

We have successfully demonstrated the principles of wake-field acceleration using structures (cavity, dielectric) and plasmas as wake-field devices using the AATF at Argonne National Laboratory. Due to the limited driver electron pulse intensity and relat...

Acceleration effects on resonant frequencies of electromagnetic cavity, using constitutive equations

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the {pi}-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is {beta}{lambda}, where ...

A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where ...

We have manufactured a total of six {beta} = 0.64, 700-MHz 5-cell cavities. The APT (Accelerator Production of Tritium) specification requires Q{sub 0} > 5 x 10{sup 9} at an accelerating field of 5 MV/m. So far, the results of vertical tests have shown maximum accelerating ...

We have manufactured a total of six {beta}=0.64, 700-MHz 5-cell cavities. The APT (Accelerator Production of Tritium) specification requires Q{sub 0} > 5 x 10{sup 9} at an accelerating field of 5 MV/m. So far, the results of vertical tests have shown maximum accelerating ...

Phase and amplitude stabilization of the fields in superconducting cavities in the presence of ponderomotive effects and microphonics was one of the major challenges that had to be surmounted in order to make superconducting rf accelerators practical. Thi...

When designing a radio frequency (RF) accelerating cavity structure various figures of merit are considered before coming to a final cavity design. These figures of merit include specific field and geometry based quantities such as the ratio of the shunt impedance to the quality factor (R/Q) or the normalized peak ...

Broad area rf field emission from superconducting Niobium surfaces was investigated. A specially designed superconducting resonator (reentrant cavity) allows direct measurement of the field emission current. Experiments were performed at four cavity modes between 500 MHz and 3.5 GHz in order to study the frequency ...

Funnels are a key component of accelerators proposed for transmutation technologies. In addition to conventional accelerator elements, specialized rf-cavities are needed in a funnel. Simulations were done to obtain their electromagnetic field distribution and to minimize the rf-induced heat loads. Using these ...

In optical cavity modes the fields in pulsed operation are limited by skin current heating to large values on order of 0.1--1 GV/m. Moreover, efficient transfer of energy from such modes to relativistic particles seems possible. A single cavity electron accelerator based on such modes would show an appreciable ...

A single quantum system, such as the Unruh-DeWitt detector, can be used to determine absolute acceleration by local measurements on a quantum field. To show this, we consider two kinematically indistinguishable scenarios: an inertial observer, Bob, measuring the field of a uniformly accelerated ...

A single-cavity test cryostat is used to conduct pulsed high power RF tests of superconducting 1.3 GHz RF cavities at 2 K. The cavities under test are welded inside individual helium vessels and are outfitted ('dressed') with a fundamental power coupler, higher-order mode couplers, magnetic shielding, a blade tuner, ...

Field emission is one of the key issues in superconducting RF for particle accelerators. When present, it limits operating gradient directly or via induced heat load at 2K. In order to minimize particulate contamination of and thus field emission in the CEBAF SRF cavities during assembly, a cold ceramic RF window ...

An accelerating RF cavity usually requires accessory devices such as a tuner, a coupler, and a damper to perform properly. Since a device is attached to the wall of the cavity to have certain electrical coupling of the cavity field through the opening. RF power dissipation is involved. In a ...

The Spallation Neutron Source (SNS) makes use of superconducting cavities for the acceleration of negative H ions in the main linac. Two types of 6-cell Niobium cavities are used in the superconducting portion of the linac: 33 Beta=0.61 cavities and 48 Beta=0.81 cavities. Each ...

The Spallation Neutron Source (SNS) makes use of superconducting cavities for the acceleration of negative H ions in the main linac. Two types of 6-cell Niobium cavities are used in the superconducting portion of the linac: 33 {beta}=0.61 cavities and 48 {beta}=0.81 cavities. Each ...

The new low level rf system for the light ion acceleration program features direct digital control of a phase continuous rf synthesizer clocked by finite changes in the B field. The system, its operation and testing are described. The system covers the complete rf frequency range and switches over from single cavity ...

At Los Alamos National Laboratory, we are studying higher-order-mode (HOM) suppression schemes for the ferrite-tuned main ring cavity of the Advanced Hadron Facility (AHF). We have built a simplified half-scale model of the cavity which is a /lambda//4 coaxial cavity. The accelerating mode frequency is 107 MHz. ...

Muon cooling requires high-gradient normal conducting cavities operating in multi-Tesla magnetic fields for muon beam focusing in an ionization cooling channel. Recent experience with an 805-MHz pillbox cavity at the Fermilab MuCool Test Area has shown a significant drop in accelerating field ...

I consider two-level detectors, coupled to a quantum scalar field, moving inside cavities. I highlight some pathological resonant effects due to abrupt boundaries, and decide to describe the cavity by switching smoothly the interaction by a time-dependent gatelike function. Considering uniformly accelerated ...

An adaptive feedforward control loop is provided to stabilize accelerator beam loading of the radio frequency field in an accelerator cavity during successive pulses of the beam into the cavity. A digital signal processor enables an adaptive algorithm to generate a feedforward error correcting ...

The field flatness (FF) in a multi-cell superconducting cavity affects not only net accelerating voltage, but also peak surface field [1] and Lorentz detuning coefficient [2]. Our measurements indicate that the tuner's motion changes not only the cavity frequency but also its FF. This ...

An 805 MHz RF pillbox cavity has been designed and constructed to investigate potential muon beam acceleration and cooling techniques. The cavity can operate at vacuum or under pressure to 100 atmospheres, at room temperature or in a liquid nitrogen bath at 77 K. The cavity is designed for easy assembly and ...

Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on th...

Theoretical foundation for a Wakefield Accelerator using rf cavities has been completed. Thus experiments are in the planning to test the numerical and analytical results determined. The computational work and the experiments being planned are discussed in this presentation. (AIP)

The choice of a suitable geometry in designing a radio-frequency cavity for e/sup +/e/sup -/ storage ring allows the reduction of multipacting (MP) discharges. We have studied the behaviour of resonant electron discharges in the RF cavity of the Adone storage ring in Frascati, that shows a broad MP barrier in the 35 to 70 kV range of the ...

A method and apparatus for establishing an ion-stabilized self-focusing relativistic electron beam from a plasma are reported. A plasma is introduced into a specially designed cavity by plasma guns, and a magnetic field satisfying betatron conditions is produced in the cavity by currents flowing in the highly conductive, ...

The Advent of laser-ion-guiding in the Advanced test Accelerator along with the development of accelerator cavities optimized with respect to beam breakup coupling impedence now make it possible to consider a new class of high current, high emergy linear induction accelerators. The control of the beam breakup and ...

The Advent of laser-ion-guiding in the Advanced test Accelerator along with the development of accelerator cavities optimized with respect to beam breakup coupling impedence now make it possible to consider a new class of high current, high emergy linear induction accelerators. The control of the beam breakup and ...

EMMA is an experiment to study beam dynamics in fixed field alternating gradient accelerators (FFAGs). It accelerates the beam in about 10 turns using 1.3 GHz cavities in a mode like that used for muon accelerators. Many applications of FFAGs prefer to have slower ...

Microwave ferrites with dc bias fields perpendicular to the rf fields exhibit magnetic and dielectric quality factors 1 order of magnitude above that of ferrites used in ferrite-tuned synchrotron accelerating cavities built in the past. For the LAMPF II p...

Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nano-smoothness. Electropolishing (EP) is the technique of choice to be developed for high-field superconducting radio frequency (SRF) cavities. Electrochemical impedance spectroscopy (EIS) and related ...

Cooling muon beams in flight requires absorbers to reduce the muon momentum, accelerating fields to replace the lost momentum in the longitudinal direction, and static solenoidal magnetic fields to focus the muon beams. The process is most efficient if both the magnetic fields and accelerating ...

Cooling muon beams in flight requires absorbers to reduce the muon momentum, accelerating fields to replace the lost momentum in the longitudinal direction, and static solenoidal magnetic fields to focus the muon beams. The process is most efficient if both the magnetic fields and accelerating ...

The main goals of the successful research program are to provide theoretical basis to analyze the wake-fields in the elliptically shaped wake-field cavity, and to examine the feasibility of applying the new idea of wake-field acceleration to beams of lasers. The theorectical research is very ...

Two {beta} = 0.175, 350 MHz, 2-gap superconducting (SC) spoke cavities were fabricated in industry under the Advanced Accelerator Applications (AAA) project for the transmutation of nuclear waste. These cavities are promising candidates for the accelerating structures between a RFQ and the elliptical SC ...

A collective field accelerator which operates with a vacuum diode and utilizes a grooved cathode and a dielectric anode that operates with a relativistic electron beam with a .nu./.gamma. of .about. 1, and a plurality of dielectric lenses having an axial magnetic field thereabout to focus the collectively ...

It is shown that for a cylindrical pillbox accelerator cavity operating in a TM[sub 0n0] mode, the use of laminated conductors for the flat walls in conjunction with a multilayered dielectric structure for the round walls can decrease skin-effect losses by an order of magnitude over that of a copper cavity having the same ...

In linear accelerators the maximum achievable beam current is often limited by the Beam Breakup (BBU) instability. This instability arises from the interaction of a transversely displaced beam with the dipole modes of the acceleration cavities. The modes of interest have non-zero transverse magnetic fields at the ...

Superconducting radio frequency (SRF) cavities are a popular choice among researchers designing new accelerators because of the reduced power losses due to surface resistance. However, SRF cavities still have unresolved problems, including the loss of power to stray electrons. Sources of these electrons are field ...

The discussion is confined to high gradient, room-temperature accelerators which have clean well-finished cavity surfaces and good vacuum conditions. Breakdown-initiating mechanisms due to ''cold'' field electron emission occurring at isolated sites on broad-area cavity surfaces, ...

Recent experiments on the breakdown of rf cavities revealed severe surface damage and a reduction of the maximum accelerating gradient after operation in an external magnetic field. This finding implies the possibility of serious problems for cooling lattices wherein rf cavities and external magnetic ...

A coupled cavity accelerator (CCA) accelerates a charged particle beam with rf energy from a rf source. An input accelerating cavity receives the charged particle beam and an output accelerating cavity outputs the charged particle beam at an increased ...

We have measured the effects of high (0 4.5 T) magnetic fields on the operating conditions of 805 MHz accelerating cavities, and discovered that the maximum accelerating gradient drops as a function of the axial magnetic field. While the maximum gradient of any cavity is ...

In 1961 I began doing active research on RF superconducting cavities at the High Energy Physics Laboratory (HEPL) at Stanford University. At that time there were already nascent research programs exploring superconducting cavities at four other laboratories around the world, including the one at the Stanford physics department. However, all attempts to ...

The listed drawings and subsequent referenced drawings therein provide the data and specifications for construction of the phase lock, gap voltage, and frequency control systems used to control the rf accelerating cavity parameters of the Stanford Linear Accelerator Center's PEP storage ring. The phase lock portion is a phase ...

Use of a superconducting traveling wave accelerating (STWA) structure with a small phase advance per cell rather than a standing wave structure may provide a significant increase of the accelerating gradient in the ILC linac. For the same surface electric and magnetic fields the STWA achieves an accelerating ...

A 6-cell 805 MHz superconducting cavity for acceleration in the velocity range of about 0.4 to 0.53 times the speed of light was designed. After single-cell prototyping, three 6-cell niobium cavities were fabricated. In vertical RF tests of the 6-cell cavities, the measured quality factors (Q{sub 0}) were between 7 ...

Three prototype cavities for the side-coupled accelerating structure of Fermilab's Linac Upgrade have been powered. The cavities operate at a nominal maximum surface electric field of 37--42 MV/m and have been run at close to 60 MV/m at 805 MHz. This paper will present the experience accumulated on x-ray ...

1% amplitude and l{degree} phase. The feedback control system requires a phase-stable RF reference subsystem signal to correctly phase each cavity. Also, instead of a single klystron RF source for individual accelerating cavities, multiple klystrons will drive a string of resonantly coupled cavities, based on input ...

A 5-cell, normal-conducting, 1.3 GHz, standing-wave (SW) cavity was built as a prototype capture accelerator for the ILC positron source. Although the ILC uses predominantly superconducting cavities, the capture cavity location in both a high radiation environment and a solenoidal magnetic ...

A mechanism for acceleration of protons is described, in which energy gain occurs near cyclotron resonance as protons drift through a sequence of rotating-mode TE111 cylindrical cavities in a strong nearly uniform axial magnetic field. Cavity resonance frequencies decrease in sequence from one another with a fixed ...

In the baseline Neutrino Factory muon front end, strong, closely spaced solenoid magnets are used to contain the high emittance muon beam. In addition, significant acceleration is required for bunching, phase rotation and cooling, requiring RF cavities operating near to their maximum achievable gradient. There are experimental indications that RF ...

Field emission in an rf cavity in the presence of external magnetic fields is examined. We show that emitted electrons from a sharp protrusion are focused by the magnetic field into small spots at another location in the cavity where they heat its surface. Scaling laws are established for the ...

A double-sided planar mm-wave linear accelerating cavity structure has been studied. The input/output couplers for the accelerating cavity structure have been designed using the Hewlett-Packard High Frequency Structure Simulator (HFSS). The program is a frequency domain finite element 3-D field ...

Optimization of the non-scaling FFAG lattice for the specific application of the muon acceleration with respect to the minimum orbit offsets, minimum path length and smallest circumference is described. The short muon lifetime requires fast acceleration. The acceleration is in this work assumed to be with super-conducting ...

The operation principle of the Astron electron accelerator is an accelerating induction electric field generated by changing the magnetic flux in a ferromagnetic material. The accelerator consists of a number of identical modular units. Each unit is cavity loaded with a ring-shaped ...

A semi-empirical method that allows us to predict intensity of generated field emission in superconducting RF cavities is described. Spatial, angular and energy distributions of the generated radiation are calculated with the FISHPACT code. The Monte Carlo code MARS15 is used for modeling the radiation transport in matter. A comparison with dose rate ...

The shape of TESLA accelerating structure can be improved to decrease maximal surface magnetic field by sacrificing and increasing maximal surface electric field. This sacrifice may be necessary because the magnetic field is a hard limit but electric field emission can be decreased by ...

Superconducting accelerators, such as the International Linear Collider (ILC), rely on very high Q accelerating cavities to achieve high electric fields at low RF power. Such cavities have very narrow resonances: a few kHz with a 1.3GHz resonance frequenc...

of studies on materials and cryogenic test of cavities, that make the group a key component of the ILC of the LHC accelerator (CERN) main dipole and many NbTi and Nb3Sn solenoids for laboratory use. In the last in strong collaboration with industrial partners as ETH and Zanon. The high magnetic field laboratory group

We present a brief overview of the formalism used, and some simulation results for transverse and longitudinal motion of a bunch of particles moving through a cavity (e.g., the Brookhaven National Laboratory high brightness photocathode gun), including effects of the accelerating field, space charge forces (e.g., arising from the ...

... Title : Resonant Frequencies of an Electromagnetic Cavity in an Accelerated System of Reference. Descriptive Note : Journal article,. ...

The use of present Digital Signal Processing (DSP) techniques can drastically reduce the residual rf amplitude and phase error in an accelerating rf cavity. Accelerator beam loading contributes greatly to this residual error, and the low-level rf field control loops cannot completely absorb the fast transient of ...

Reduction of the available accelerating gradient in cavities exposed to external magnetic fields is a longstanding problem which limits the performance of many systems, especially muon accelerators. We propose a novel idea for improving the cavity's gradient by suppressing breakdown events ...

In the last few years superconducting radio-frequency (rf) cavities made of high-purity (residualresistivityratio>200) niobium achieved accelerating gradients close to the theoretical limits. An obstacle towards achieving reproducibly higher fields is represented by �anomalous� losses causing a sharp degradation of the ...

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 ...

We have developed a digital process that emulates an analog oscillator and ultimately a self excited loop (SEL) for field control. The SEL, in its analog form, has been used for many years for accelerating cavity field control. In essence the SEL uses the cavity as a resonant circuit -- much ...

The 476 MHz accelerating cavities currently used at SLAC are those installed on the PEP-II B-Factory collider accelerator. They are designed to operate at a maximum accelerating voltage of 1 MV and are routinely utilized on PEP-II at voltages up to 750 kV. During the summer of 2003, SPEAR3 will undergo a ...

The PHERMEX accelerator is a standing wave, 50 MHz rf linear accelerator. The rf fields in three cavities are pulsed for a period of 3 ms. The experiments described are directed toward studying injection and trapping of electron rings at modes field strengths (approximately 1 T). A single 200 ...

The ionization cooling of muons requires longitudinal acceleration of the muons after scattering in a hydrogen target. In order to maximize the accelerating voltage, we propose using linear accelerating structures with cells bounded by thin beryllium metal foils. This produces an on-axis field equivalent to the ...

X-ray generation by many charged particles experiencing accelerations similar to those in laser wakefield accelerator experiments, including the effects of the interaction of the laser pulse with trapped electrons, as well as betatron oscillations in an electron cavity, is directly evaluated. Semianalytic calculations of high energy ...

A superconducting microwave cavity has been designed to test advanced materials for use in the accelerating structures contained within linear colliders. The electromagnetic design of this cavity produces surface magnetic fields on the sample wafer exceeding the critical limit of Niobium. The ability of this ...

Two niobium resonant cavities for high-brightness ion beam acceleration have been constructed and tested. The first was based on a coaxial quarter-wave geometry and was optimized for phase velocity {beta}{sub o} = 0.15. This cavity, which resonates at 400 MHz in the fundamental mode, operated at an average (wall-to-wall) ...

Two niobium resonant cavities for high-brightness ion beam acceleration have been constructed and tested. The first was based on a coaxial quarter-wave geometry and was optimized for phase velocity {beta}{sub 0} = 0.15. This cavity, which resonates at 400 MHz in the fundamental mode, operated at an average (wall-to-wall) ...

Superconducting radio-frequency (SRF) cavities are a promising technology for future high energy particle accelerators. SRF technology is presently limited by field emission (FE), a quantum mechanical tunneling effect wherein electrons are emitted from a metal surface into vacuum in the presence of a strong electric ...

We have investigated the spontaneous radiative decay of resonant nuclei in a planar x-ray waveguide after excitation by synchrotron radiation pulses. The waveguide acts as a cavity and modifies the mode structure of the electromagnetic field. As a result, the rate of spontaneous emission is enhanced by a factor proportional to the density of photon states ...

An open question in the field of relativistic quantum information is how parties in arbitrary motion may distribute and store quantum entanglement. We propose a scheme for storing quantum information in the field modes of cavities moving in flat space-time and analyze it in a quantum field theoretical framework. In ...

An open question in the field of relativistic quantum information is how parties in arbitrary motion may distribute and store quantum entanglement. We propose a scheme for storing quantum information in the field modes of cavities moving in flat space-time and analyze it in a quantum field theoretical framework. In ...

The building of a muon collider is motivated by the desire to collide point-like particles while reducing the limitations imposed by synchrotron radiation. The many challenges unique to muon accelerators are derived from the short lifetime of the muons. The muons must be produced, then formed into a beam and accelerated to their final energy in less than a ...

The Ground Test Accelerator (GTA) will be a heavily beam-loaded H/sup minus/ linac with tight tolerances on accelerating field parameters. The methods used in modeling the effects of beam loading in this machine are described. The response of the cavity to both beam and radio-frequency (RF) drive stimulus is ...

A deflecting mode in an rf cavity caused by an aperture of the coupling hole from a waveguide is studied. If the coupling hole was a finite size, the rf modes in the cavity can be distorted. We consider the distorted mode as a sum of the accelerating mode, and the deflecting mode. The finite-size coupling hole can be considered as ...

A model has been developed to analyze the static and dynamic behavior of superconducting accelerating cavities operated in self-excited loops in the presence of phase and amplitude feedback, ponderomotive effects, and beam loading. This is an extension of an earlier analysis of the stabilization of superconducting cavities which has ...

A model has been developed to analyze the static and dynamic behavior of superconducting accelerating cavities operated in self-excited loops in the presence of phase and amplitude feedback, ponderomotive effects, and beam loading. This is an extension of an earlier analysis of the stabilization of superconducting cavities which has ...

Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nanosmoothness. Electropolishing is the technique of choice to be developed for high-field superconducting radiofrequency cavities. Electrochemical impedance spectroscopy (EIS) and related techniques point ...

Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of ...

The purpose of this note is to describe the electrical and mechanical properites of particle accelerator rf cavities in a manner which will be useful to physics and engineering graduates entering the accelerator field. The discussion will be limited to proton (or antiproton) synchrotron ...

An L-band (1.3 GHz), normal-conducting, 5-cell, standing-wave cavity that was built as a prototype capture accelerator for the ILC is being high-power processed at SLAC. The goal is to demonstrate stable operation at 15 MV/m with 1 msec, 5 Hz pulses and the cavity immersed in a 0.5 Telsa solenoidal magnetic field. ...

The phenomenon of field emission is very well known: electrons are extracted from within the solid state potential well of a metal and are emitted from the metal's surface under the presence of an accelerating potential. In many accelerators, electromagnetic energy is delivered to charged particles by means of microwave ...

The performances of SRF cavities made of high purity bulk niobium have been improving in the last few years and surface magnetic fields (Bp) close to the thermodynamic critical field of niobium have been achieved in a few cases. The recommendation made in 2004 in favor of SRF as the technology of choice for the International Linear ...

This work is intended to be a study into the application of the finite-difference time-domain, or FD-TD technique, to some of the problems faced by designers of equipment used in modern accelerators. In particular it discusses using the FD-TD algorithm to study the field distribution of a simple two-dimensional cavity in both space and ...

Unwanted field emission is a well known problem for high-gradient accelerating structures as it can cause damage and initiate breakdown. Recent experiments indicated that the deleterious effects of field-emission are greatly enhanced in the presence of external magnetic fields. In the context of designing a muon ...

This report discusses the analysis and design of rf cavities and rf power sources in accelerators. (LSP).

... Title : ACCELERATOR-BUNCHER OF ELECTRONS,. ... CAVITY RESONATORS, KLYSTRONS, ELECTRON BEAMS, OSCILLATION, ELECTRON ...

The Lawrence Livermore Laboratory is currently constructing a new linear induction accelerator with a higher beam current than the Astron accelerator. The new accelerator, called the Experimental Test Accelerator (ETA) will be a 5-MeV, 10-kA accelerator with a pulse width of 50-ns. Like the ...

The design accelerating gradient for Tesla SRF cavities is 25 MV/m. For achieving such high accelerating gradients both the field emission and thermal quench limitations have to be eliminated. Post purification of the niobium sheets, cells or the completed cavities is likely to achieve the ...

Focusing of a low-energy beam of heavy ions in a linear accelerator based on a periodic sequence of independently phased superconducting cavities is considered. The possibility of heavy ion beam focusing by a system of superconducting solenoids is analyzed. The advantages and disadvantages of this focusing technique are considered. It is shown that ...

With the requirement for particle accelerators getting higher and higher in energy and accelerating gradients many phenomena become more and more dominant. One of them is the dark current, resulted from collective movement of electrons which by quantum effects leave cavity walls and cause additional thermal heatup as well as many ...

The choice of superconducting materials for accelerator rf cavities has been determined in the past only in part by basic properties of the superconductors, such as the critical field, and to a larger extent by criteria which include fabrication processes, surface conditions, heat transfer capabilities and so on. For cw operated ...

The SNS linac RF control system (RFCS) is currently in development. A system is being installed in a superconducting test stand at Jefferson Laboratory presently. Two systems will soon be installed at Oak Ridge National Laboratory (ORNL) and more are due to be installed early next year. The RF control system provides field control for the entire SNS linac, including an RFQ and ...

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, ...

A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. ...

Large grain niobium has the potential of simplifying the production sequence and consequently reducing the cost of the superconducting RF cavities for ILC. To investigate the feasibility of fabrication and the possibility to achieve high gradient by large grain cavities, two 1.3 GHz cavities were made of China large grain niobium and a ...

Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic ...

of TESLA accelerating structure can be improved to decrease maximal surface magnetic field by sacrificing. For the TESLA accelerating cavity, as reported in [1], these values are: W 0.2max =accEE , 6.42max =accEH Oe that for the regular TESLA cells [2] 1=e , =h .1 The choice of the TESLA structure for comparison is ...

BS>A device is descrined for producing nuclear fusion reactions by additional acceleration of a hydrogen isotope plasma formed and initially accelerated by a collapsing magnetic field. The plasma is enclosed in a toroidal cavity within a vessel composed of a plurality of insulated coaxial segments. The ...

The various ongoing programs in applied superconductivity supported by BNL are summarized, including the development of high field ac and dc superconducting magnets for accelerators and other applications, of microwave deflecting cavities for high energy ...

In photoinjector electron guns, electrons are emitted from a photocathode by a short laser pulse and then accelerated by intense RF fields in a resonant cavity. Photoinjectors are very versatile tools. Normally we think of them in terms of the production ...

These results use the program ETRANS written by Harvey Lynch. ETRANS steps positrons produced in the target through a series of elements simulating the magnetic and accelerting fields of the flux concentrator, DC solenoids, and accelerating cavities. 13 figures, 1 table.

SLC beams of opposite charge can be transversely deflected in the same direction by RF fields in the accelerating cavities caused by girder tilts, coupler-asymmetries, or manufacturing errors. A symmetric deflection can be corrected by a magic angle bump ...

When an intense electron beam is injected into an evacuated drift cavity placed in a strong longitudinal magnetic field a virtual cathode will form if the beam current exceeds the space charge limiting current. If the drift tube is flared, the virtual cat...

Electropolishing has shown promising results for the treatment of Nb cavities to be used in particle accelerators, particularly in the attainment of high surface electric fields. In support of the CEBAF Upgrade project and as part of a longer-term R and D...

A facility is presently being constructed which can measure transverse and longitudinal wake fields in structures and media. Initial experiments with cavities and plasma are being directed at systems which could be applied to a high energy linear collider...

Use of a superconducting (SC) traveling-wave accelerating (STWA) structure with a small phase advance per cell, rather than a standing-wave structure, may provide a significant increase in the accelerating gradient in the ILC linac [1]. For the same surface electric and magnetic fields, the STWA achieves an ...

Use of a superconducting (SC) traveling-wave accelerating (STWA) structure with a small phase advance per cell, rather than a standing-wave structure, may provide a significant increase in the accelerating gradient in the ILC linac [1]. For the same surface electric and magnetic fields, the STWA achieves an ...

When large transverse and longitudinal emittances are to be transported through a circular machine, extremely rapid acceleration holds the advantage that the beam becomes immune to nonlinear resonances because there is insufficient time for amplitudes to build up. Uncooled muon beams exhibit large emittances and require fast acceleration to avoid decay ...

In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF ...

Radio-frequency (rf) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve rf field values approaching the theoretical limit for niobium is represented by ``anomalous'' losses which degrade the quality ...

Radio-frequency (RF) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve RF field values approaching the theoretical limit for niobium is represented by ''anomalous'' ...

A systematic study is presented of the effects of pulsed high power RF processing (HPP) as a method of reducing field emission (FE) in superconducting radio frequency (SRF) cavities to reach higher accelerating gradients for future particle accelerators. The processing apparatus was built to provide up to 150 kW ...

In order to meet the requirements of high average current accelerators, such as the Superconducting Proton Linac (SPL) at CERN and the electron-ion collider, (MeRHIC) at BNL, a high current 5-cell Nb superconducting cavity, called BNL3 cavity, was optimized and designed. The optimization process aimed at maximizing the R/Q of the ...

Automation of DC photoinjector designs using a genetic algorithm (GA) based optimization is an accepted practice in accelerator physics. Allowing the gun cavity field profile shape to be varied can extend the utility of this optimization methodology to superconducting and normal conducting radio frequency (SRF/RF) gun based injectors. ...

We analyzed and cold tested a 17 GHz 1-1/2-cell RF gun cavity excited through two coupling holes in the broad wall of a rectangular waveguide. An equivalent circuit theory and an advanced field theory were developed to describe the excitation of an 1-1/2-cell RF gun cavity. SUPERFISH was used to calculate the majority of the equivalent ...

This paper describes three stand-alone programs that use the electromagnetic fields generated by the MAFIA 2.04 codes to analyze radio-frequency (RF) cavities. Illustrations are provided that show how these codes are used to do the following: (1) analyze the effect of the coupling slots on the electric and magnetic fields of the linacs ...

The exact solution of the classical nonlinear equation of motion for a relativistic electron in the field of two electromagnetic (EM) waves is obtained. For the particular case of the linearly polarized standing EM wave in the planar optical cavity, the intensity of the nonlinear Compton scattering, the time of flight, and the momentum variation after the ...

The exact solution of the classical nonlinear equation of motion for a relativistic electron in the field of two electromagnetic (EM) waves is obtained. For the particular case of the linearly polarized standing EM wave in the planar optical cavity, the intensity of the nonlinear Compton scattering, the time of flight, and the momentum variation after the ...

During vertical testing of SNS superconducting RF cavities, a lot of electron activity was observed. This could be evidence of in-cell multipacting, cell to cell electron mitigation or near-axis dark current. To study the potential for these electron activities in SRF cavities, a multi-purpose electron tracking code (FishPact) was developed based on the ...

The analog controller for phase and amplitude control of a 402.5 MHz super conducting cavity is described in this paper. The cavity is a single cell with niobium explosively bonded to a copper cavity. It is used as an energy compressor for pions at the Clinton P. Anderson Meson Physics Facility (LAMPF). The controller maintains ...

By using a photocathode instead of a thermionic cathode in a klystron, the possibility exists to make very short low energy spread bunches of high efficiency. However, there is a fundamental limit to the efficiency of a conventional output cavity, such as the one used in the SLAC XK-5 klystron. The fringing electric field in the drift tube acts on the beam ...

Recirculating, energy-recovering linacs can be used as driver accelerators for high power FELs. Instabilities which arise from fluctuations of the cavity fields are investigated. Energy changes can cause beam loss on apertures, or, when coupled to M{sub 56}, phase oscillations. Both effects change the beam induced voltage in the ...

The University of Maryland Dynamical Systems and Accelerator Theory Group carries out research in two broad areas: the computation of charged particle beam transport using Lie algebraic methods and advanced methods for the computation of electromagnetic fields and beam-cavity interactions. Important improvements in the state of the art ...

The University of Maryland Dynamical Systems and Accelerator Theory Group carries out research in two broad areas: the computation of charged particle beam transport using Lie algebraic methods and advanced methods for the computation of electromagnetic fields and beam-cavity interactions. Important improvements in the state of the art ...

The AFEL accelerator has produced beams of greater than 2 x 10(exp 12) A/m(exp 2) at 1 nC (brightness = 2*I/(var epsilon)(exp 2), with I greater than 100 A and (var epsilon) of than 2(pi) mm-mrad normalized ms emittance). The 1300 MHz standing-wave accelerator uses on-axis coupling cells. The electron source is a photoinjector with a CsK2Sb photocathode. ...

The AFEL accelerator has produced beams of 1 nC with peak currents greater than 100 A and a normalized, rms emittance less than 2? mm mrad. The 1300 MHz standing-wave accelerator uses on-axis coupling cells. The electron source is a photoinjector with a CsK2Sb photocathode. The photoinjector is an integral part of a single 11-cell ...

The AFEL accelerator has produced beams of greater than 2 {times} 10{sup 12} A/m{sup 2} at 1 nC (brightness = 2*I/{var_epsilon}{sup 2}, with I greater than 100 A and {var_epsilon} of than 2 {pi} mm-mrad normalized ms emittance). The 1300 MHz standing-wave accelerator uses on-axis coupling cells. The electron source is a photoinjector with a CsK{sub 2}Sb ...

An important linear accelerator requirement, in order to demonstrate narrow energy spectra, is the injection of electron bunches of narrow phase spread and negligible inter-bunch current. This can be achieved by r-f transverse modulation and clipping of the beam by an aperture prior to injection into the accelerator waveguide, i.e., chopper operation. By ...

Recent studies of the scaling laws and economic feasibility of very-high-energy linear accelerators suggest the use of very-short-wavelength accelerating structures. Consideration is being given to the use of electromagnetic driving fields of centimeter, millimeter, and even micron wavelengths. As we scale down to smaller dimensions, ...

Since the last workshop we have tested six b=0.64, 700 MHz, 5-cell elliptical superconducting cavities in collaboration with JLAB in vertical cryostats. All the cavities exceeded the requirements for Accelerator Production of Tritium (APT) (Q0 = 5 x 109 at Eacc = 5 MV/m) with ample margin. The low-field Q0 at 2 K ...

Field strength measurements for the determination of the R/Q of a mm-wave, 50-MeV electron linear accelerator using perturbational techniques are described. The perturbation is achieved using optical fibers coated with a thin metallic film to form a hollow cylinder. The perturbational form factors for such a geometry are approximated using several simple ...

The high levels of peak RF input power required for linear collider TW accelerator structures, and the need to prevent undesirable transverse momentum contributions being imparted to the beam during traversal of the linac coupler cavities, have led to the use of symmetric dual feed cylindrical cavities having diametrically opposed side ...

Superconducting rf cavities are increasingly used in accelerators. Gradient is a parameter of particular importance for the ILC. Much progress in gradient has been made over the past decade, overcoming problems of multipacting, field emission, and breakdown triggered by surface impurities. However, the quenching limit of the surface ...

Superconducting rf cavities are increasingly used in accelerators. Gradient is a parameter of particular importance for the ILC. Much progress in gradient has been made over the past decade, overcoming problems of multipacting, field emission, and breakdown triggered by surface impurities. However, the quenching limit of the surface ...

This paper describes a procedure to set the phase and amplitude of the RF fields in the Spallation Neutron Source (SNS) linac's superconducting cavities. The linac uses superconducting cavities to accelerate the H{sup -} ion beam from the normal conducting linac at 185 MeV to a final energy of {approx}1 ...

As a prior option of the next generation of energy source, the accelerator driven subcritical nuclear power system (ADS) can use efficiently the uranium and thorium resource, transmute the high-level long-lived radioactive wastes and raise nuclear safety. The ADS accelerator should provide the proton beam with tens megawatts. The superconducting linac ...

Understanding the structure of the diffusion region of magnetic reconnection is crucial to pinpoint the mechanism of energy conversion from magnetic field to plasma. Characteristics of a diffusion region with guide field (i.e., component reconnection) may be significantly different from those of a diffusion region without guide field ...

Experimental measurements of magnetic fields generated in the cavity of a self-injecting laser-wakefield accelerator are presented. Faraday rotation is used to determine the existence of multimegagauss fields, constrained to a transverse dimension comparable to the plasma wavelength ??p and several ?p ...

Experimental measurements of magnetic fields generated in the cavity of a self-injecting laser-wakefield accelerator are presented. Faraday rotation is used to determine the existence of multimegagauss fields, constrained to a transverse dimension comparable to the plasma wavelength �?p and several ?p ...

The Recirculating Linear Accelerator (RLA) is returning to operation with a new relativistic electron beam (REB) injector and a modified accelerating cavity. Upon completion of our pulsed-power test program, we will capture the injected beam on an Ion Focussed Regime (IFR) guiding channel in either a spiral or a closed racetrack drift ...

The Recirculating Linear Accelerator (RLA) is returning to operation with a new relativistic electron beam (REB) injector and a modified accelerating cavity. Upon completion of our pulsed-power test program, we will capture the injected beam on an Ion Focussed Regime (IFR) guiding channel in either a spiral or a closed racetrack drift ...

Superconducting radio frequency (SRF) cavities made from deep drawn high-purity niobium have become a popular approach for the design of particle accelerators. A number of current accelerators use this technology and it is a leading candidate for future designs. The development of this technology has required significant advances in ...

Energen, Inc. has designed, built and demonstrated a fine tuning mechanism for superconducting radio frequency (SRF) cavities used in particle accelerators. This tuner is based on giant magnetostrictive materials being developed by Energen, Inc. Magnetostrictors elongate when exposed to a small magnetic field. This extension is ...

A muon cooling channel calls for very high accelerating gradient RF structures to restore the energy lost by muons in the absorbers. The RF structures have to be operated in a strong magnetic field and thus the use of superconducting RF cavities is excluded. To achieve a high shunt impedance while maintaining a large enough aperture to ...

A heavy ion superconducting linac is being installed at ISAC/TRIUMF. A first stage of the ISAC-II upgrade at TRIUMF will see the installation of 20 quarter wave bulk niobium cavities (?0 = 0.057, 0.071). The cavities operate cw at 106 MHz with design peak fields of Ep = 30 MV/m, Bp = 60 mT while delivering an ...

We present recent high power RF test results on an 805 MHz cavity for a muon cooling experiment at Lab G in Fermilab. In order to achieve high accelerating gradient for large transverse emittance muon beams, the cavity design has adopted a pillbox like shape with 16 cm diameter beam iris covered by thin Be windows, which are ...

High brightness sources are the basic ingredients in the new accelerator developments such as Free-Electron Laser experiments. The effects of the interactions between the highly charged particles and the fields in the accelerating structure, e.g. R.F., Space charge and Wake fields can be detrimental to the beam and ...

High brightness sources are the basic ingredients in the new accelerator developments such as Free-Electron Laser experiments. The effects of the interactions between the highly charged particles and the fields in the accelerating structure, e.g. R.F., Space charge and Wake fields can be detrimental to the beam and ...

In previous applications of high-velocity superconducting cavities the accelerated beam currents were sufficiently high that the microphonics-induced frequency excursions were significantly less than the loaded bandwidth, and the power absorbed by the beam dominated the total power requirement. In new applications (CEBAF Upgrade, RIA) the beam currents ...

Four superconducting cavities have been developed at the superconducting RF test facility (STF) at KEK as candidates for the International Linear Collider (ILC) accelerating cavity. These cavities, which are termed TESLA-type STF baseline cavities, are equipped with newly designed ...

The APLE (Average Power Laser Experiment) photoinjector accelerates electrons to 5 MeV with four cavities. A solenoid placed between the first two cavities focuses the low energy (1.2 MeV) electron beam. The beam transport and the beam quality of the inje...

The packaging of microelectromechanical devices is currently one of the most challenging in this emerging field. The available packaging technologies often provide large dimensions and expensive solutions, thereby limiting the market penetration of micro electromechanical devices. A wafer level chip scale package (WLCSP) with an integrated cavity above the ...

It is shown that by incorporating a nonisotropic conductive thin film in a dielectric loaded super-conductive structure, it is possible to design an accelerator cavity wherein the maximum magnetic field at the surface of the superconductive material is below the critical value, although the gradient on axis may exceed 50 MV/m.

variety of possible fields of application. They find use both as bunchers and post accelerators to vary the final energy of the beam. In comparison to other available designs, the advantage of these structures of the beam. Fig. 1: Schematic Drawing of spiral loaded cavity In a cylindrical external tank one or more

and Engineering of Thermal Spray Coating " J.Wiley & sons. [3] M.Fouaidy et al. And reference here cited, " A New the efficiency of cavities stiffening with plasma spraying. Thermal and mechanical properties measured on niobium by a plasma sprayed copper layer. The coating must be efficient for accelerating fields up to 40 MV/m, ...

the oscillations, usually called the bucket. In this note, we shall find the incoherent bucket for single particles within the bunch, and the coherent bucket for rigid oscillations of the bunch centroid. The cavity of synchrotron oscillations is much longer than the cavity filling time. Linear stability analysis 1 shows

Superconducting Radio Frequency (SRF) accelerating structures present a unique design environment for the high-power radio frequency (RF) antennas that deliver power to the cavity to establish the electromagnetic fields and ultimately accelerate beam. These RF couplers need to reliably transmit high power RF with ...

This is a summary of the design procedure for the detuned accelerator structure for SLAC's Next Linear Collider (NLC) program. The 11.424 GHz accelerating mode of each cavity must be synchronous with the beam. The distribution of the disk thicknesses and lowest synchronous dipole mode frequencies of the ...