A5047962973- Particle accelerators and beam dynamics
- Gyrotron and Vacuum Electronics Research
- Particle Accelerators and Free-Electron Lasers
- Microwave Engineering and Waveguides
- Superconducting Materials and Applications
- Advanced X-ray Imaging Techniques
- Pulsed Power Technology Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Laser Design and Applications
- Electromagnetic Compatibility and Measurements
- Photocathodes and Microchannel Plates
- Antenna Design and Analysis
- Photonic and Optical Devices
- Radio Frequency Integrated Circuit Design
- Electrostatic Discharge in Electronics
- Semiconductor materials and devices
- Energy Harvesting in Wireless Networks
- Internet of Things and Social Network Interactions
- GaN-based semiconductor devices and materials
- Terahertz technology and applications
- Radiation Therapy and Dosimetry
- Superconducting and THz Device Technology
- Advanced Radiotherapy Techniques
- Physics of Superconductivity and Magnetism
Linac Coherent Light Source
2007-2025
Menlo School
2007-2025
SLAC National Accelerator Laboratory
2015-2024
Stanford University
2003-2022
UCLA Health
2018
Stanford Synchrotron Radiation Lightsource
2003-2018
Lawrence Livermore National Laboratory
2011
Massachusetts Institute of Technology
2011
High Energy Accelerator Research Organization
2004-2010
University of California, Los Angeles
2010
A design for a compact x-ray light source (CXLS) with flux and brilliance orders of magnitude beyond existing laboratory scale sources is presented. The based on inverse Compton scattering high brightness electron bunch picosecond laser pulse. accelerator novel high-efficiency standing-wave linac rf photoinjector powered by single ultrastable transmitter at X-band frequency. efficiency permits operation repetition rates up to 1 kHz, which further boosted 100 kHz operating trains bunches pC...
We present the experimental results of a systematic study rf breakdown phenomenon in high vacuum accelerator structures. In this study, surface processing, geometry, and materials structures have been varied, one parameter at time. The rate or alternatively, probability breakdown/pulse/meter has recorded for different operating parameters. These statistical data reveal strong dependence on magnetic field, alternatively pulsed heating. This is contrast to classical view electric field...
Cyclic thermal stresses produced by rf pulsed heating can be the limiting factor on attainable reliable gradients for room temperature linear accelerators. This is especially true structures that have complicated features wakefield damping. These limits could pushed higher using special types of copper, copper alloys, or other conducting metals in constructing partial complete accelerator structures. Here we present an experimental study aimed at determining potential these materials...
Vacuum radio-frequency (rf) breakdown is one of the major factors that limit operating accelerating gradients in rf particle accelerators. The occurrence breakdowns was shown to be probabilistic, and can characterized by a rate. Experiments with hard copper cavities showed harder materials reach larger for same We study effect cavity material on short $X$-band standing wave structures. Here we report results from tests structure at cryogenic temperatures. At greater than $150\text{ }\text{...
We are exploring the physics and frequency-scaling of vacuum rf breakdowns at sub-THz frequencies. present experimental results tests performed in metallic mm-wave accelerating structures. These experiments were carried out facility for advanced accelerator (FACET) SLAC National Accelerator Laboratory. The fields excited by FACET ultrarelativistic electron beam. compared performances metal structures made with copper stainless steel. frequency fundamental mode, propagating speed light,...
We report the experimental demonstration of a mm-wave electron accelerating structure powered by high-power rf source. demonstrate reliable coupling an unprecedented power—up to 575 kW into accelerator using quasi-optical setup. This standing wave consists single-cell copper cavity and Gaussian TM01 mode converter. The is 110 GHz, 10-ns long pulses. These pulses are chopped from 3 ms gyrotron oscillator laser-driven silicon switch. show high gradient up 230 MV/m that corresponds peak surface...
Recent studies of the performance radio-frequency (rf) copper cavities operated at cryogenic temperatures have shown a dramatic increase in maximum achievable surface electric field. We propose to exploit this development enable new generation photoinjectors that may attain, through enhancement launch field photocathode, significant five-dimensional electron beam brightness. present detailed dynamics associated with such system, by examining an S-band photoinjector $250\text{ }\text{...
Purpose: To measure radiation dose in a water‐equivalent medium from very high‐energy electron (VHEE) beams and make comparisons to Monte Carlo (MC) simulation results. Methods: Dose polystyrene phantom delivered by an experimental VHEE beam line was measured with Gafchromic films for three 50 MeV two 70 Gaussian of 4.0–6.9 mm FWHM compared corresponding MC‐simulated distributions. MC the calculated EGSnrc/BEAMnrc DOSXYZnrc codes based on setup. Additionally, effect 2% energy measurement...
We present an experimental study of a high gradient metallic accelerating structure at sub-THz frequencies, where we investigated the physics rf breakdowns. Wakefields in were excited by ultrarelativistic electron beam. first quantitative measurements gradients and metal vacuum breakdowns cavities. When beam travels off axis, deflecting field is induced addition to longitudinal field. measured forces observing displacement changes shape bunch. This behavior can be exploited for...
We present a multimode $X$-band rf pulse compression system suitable for TeV-scale electron-positron linear collider such as the Next Linear Collider (NLC). The NLC main linac operating frequency is 11.424 GHz. A single unit required to produce 400 ns pulses with 475 MW of peak power. Each should power approximately 5 m accelerator structures. design consists two 75 klystrons and dual-moded resonant-delay-line that produces flat output pulse. components are all overmoded, most designed...
A prototype 11.994 GHz, traveling-wave accelerating structure for the Compact Linear Collider has been built, using novel technique of assembling from milled halves. The use halves many advantages when compared to a made individual disks. These include potential reduction in cost, because there are fewer parts, as well greater freedom choice joining technology no rf currents across halves' joint. Here we present design and fabrication structure, followed by results high-power test post-test...
Performance of the x-ray free electron laser Linac Coherent Light Source (LCLS) and Facility for Advanced Accelerator Experimental Tests (FACET) is determined by properties their extremely short bunches. Multi-GeV bunches in both LCLS FACET are less than 100 fs long. Optimization beam understanding free-electron operation require diagnostics with time resolution about 10 fs. We designed, built commissioned a set high frequency $X$-band deflectors which can measure longitudinal space charge...
This paper explores the physics of vacuum rf breakdowns in subterahertz high-gradient traveling-wave accelerating structures. We present experimental results tests 200 GHz metallic structures, made copper and copper-silver. These experiments were carried out at Facility for Advanced Accelerator Experimental Tests (FACET) SLAC National Laboratory. The fields excited by FACET ultrarelativistic electron beam. structure is an open geometry, 10 cm long, composed two halves separated a gap....
Terahertz accelerators can achieve potential gradients beyond 200 MV/m. Gyrotrons are the only power sources capable of producing megawatt-level, microsecond-long pulses in this frequency range, yet nanosecond-long required for breakdown-free operation. The authors explore possibility using a single GaAs wafer to enable production pulse widths, with rise and fall times that closely track illuminating laser's length. They demonstrate quantify reflective properties laser-induced...
We present a novel method of reducing the footprint and increasing efficiency modern multi-MW rf pulse compressor. This system utilizes high power polarizer to couple two circular waveguide modes in quadrature single resonant cavity order replicate response traditional configuration using 4-port hybrid. The 11.424 GHz, high-Q, spherical has 5.875 cm radius is fed by circularly polarized signal simultaneously excite degenerate $T{E}_{114}$ modes. overcoupled ${Q}_{0}$...
Recent experience with $X$-band accelerator structure development has shown the rf input coupler to be region most prone breakdown and degradation, effectively limiting operating gradient. A major factor in this appears high magnetic fields at sharp edges of coupling irises. As a first response problem, couplers rounded thickened iris horns have been employed successfully tested power. To further reduce for higher power flow, conceptually new designs developed, which is coupled through broad...
Electron beam interaction with high frequency structures (beyond microwave regime) has a great impact on future energy frontier machines. We report the generation of multimegawatt pulsed rf power at 91 GHz in planar metallic accelerating structure driven by an ultrarelativistic electron bunch train. This slow-wave wakefield device can also be used for gradient acceleration electrons stable phase and amplitude which are controlled manipulation To achieve precise control pulse properties,...
During the past five years, there has been an concerted program at SLAC and KEK to develop accelerator structures that meet high gradient (65 MV/m) performance requirements for Next Linear Collider (NLC) Global (GLC) initiatives. The design resulted is a 60-cm-long, traveling-wave structure with low group velocity 150 degree per cell phase advance. It average iris size produces acceptable short-range wakefield, dipole mode damping detuning adequately suppresses long-range wakefield. More...
An analytical method to estimate the scattering of RF power into multiple modes inside a nonuniform waveguide using perturbation techniques is presented. This quite general, much faster than numerical methods, and may be applied wide variety waveguides. We have used this design analyze three-section mode transformer that converts TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> circular...
We summarize recent progress in a program to develop externally powered dielectric-loaded accelerating (DLA) structures that can sustain high gradients. High-power RF tests of earlier showed strong multipactor loading. In addition, arcing at dielectric joints between the uniform DLA structure and matching sections either end limited achievable gradient. this paper, we study onset structure. also effect thin-film TiN coatings applied by atomic layer deposition reduction inner diameter Test...
In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, power, repetition rate operation, a PBG accelerator structure was designed and tested at $X$ band (11.424 GHz). The consisted single test cell with matching cells before after structure. design followed principles previously established in testing series conventional pillbox structures. an accelerating gradient $65\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ yielding breakdown two...
We have successfully designed, fabricated, installed, and tested a super compact $X$-band SLAC Energy Doubler system at SLAC. It is composed of an elegant 3 dB coupler--mode converter--polarizer coupled to single spherical energy storage cavity with high ${Q}_{0}$ 94000 diameter less than 12 cm. The available rf peak power 50 MW can be compressed average more 200 in order double the kick for electron bunches transverse deflector greatly improve measurement resolution both x-ray free-electron...