A5048796138- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Superconducting Materials and Applications
- Magnetic confinement fusion research
- Muon and positron interactions and applications
- Electromagnetic Compatibility and Measurements
- Nuclear Physics and Applications
- Near-Field Optical Microscopy
- Microwave and Dielectric Measurement Techniques
- Particle Detector Development and Performance
- Plasma Diagnostics and Applications
- Photonic and Optical Devices
- Electromagnetic Simulation and Numerical Methods
- Microwave Engineering and Waveguides
- Space Technology and Applications
- Radio Frequency Integrated Circuit Design
- Integrated Circuits and Semiconductor Failure Analysis
- Particle physics theoretical and experimental studies
- Optical Coatings and Gratings
- Laser-Plasma Interactions and Diagnostics
- Quantum Chromodynamics and Particle Interactions
- Quantum Electrodynamics and Casimir Effect
- Radiation Therapy and Dosimetry
- Underwater Vehicles and Communication Systems
Los Alamos National Laboratory
2013-2024
Los Alamos National Security (United States)
1996-2016
Goethe University Frankfurt
2014
Advanced Energy Systems (United States)
2003
University of Maryland, College Park
1995-2002
University System of Maryland
2002
Supercon (United States)
1994-2002
Superconductor Technologies (United States)
1993-1995
Tianjin Hi-Tech Superconducting Electronic Technology (China)
1993
Institute for High Energy Physics
1991
We have constructed, analytically and numerically, a class of self-consistent six-dimensional (6D) phase space stationary distributions. Stationary distributions allow us to study the halo development mechanism without it being obscured by beam redistribution its effect on formation. The is then mismatched longitudinally and/or transversely, we explore formation longitudinal transverse halos in 3D axisymmetric bunches. find that forms first for comparable mismatches because tune depression...
We have developed high-efficiency normal-conducting rf accelerating structures by combining $H$-mode resonator cavities and a transverse beam focusing permanent-magnet quadrupoles (PMQ), for velocities in the range of few percent speed light. The shunt impedance interdigital (IH-PMQ) is 10--20 times higher than that conventional drift-tube linac, while size 4--5 smaller. Results combined 3D modeling---electromagnetic computations, multiparticle beam-dynamics simulations with high currents,...
A realistic treatment of halo formation must take into account 3D beam bunches and 6D phase space distributions. We recently constructed, analytically numerically, a new class self-consistent stationary distributions, which allowed us to study the development mechanism without being obscured by effect redistribution. In this paper we consider nonstationary distributions how characteristics compare with those obtained using distribution. then discuss redistribution on mechanism. contrast...
An analysis of the stability and halo formation is presented for a breathing axisymmetric beam uniform density [Kapchinsky-Vladimirsky (KV) beam] in focusing channel. Theoretical results are obtained form modes involving nonuniform charge density. In particular, mismatch-tune depression space explored, both analytically by numerical particle-in-cell simulations, to determine limits growth rates most unstable modes. The implications then explored. Halo parameters simulations compared with...
We demonstrate that a small discontinuity (such as an enlargement or hole) on smooth waveguide can result in the appearance of trapped modes localized vicinity discontinuity. The frequencies these lie slightly below cutoff corresponding propagating waveguide. find distribution electromagnetic field and calculate their damping rate due to finite conductivity walls. contribution longitudinal impedance is calculated.
After 30 years of operation, the Cockcroft-Walton based injector at Fermi National Accelerator Laboratory has been replaced by a new beam line including dimpled magnetron 35 keV source in combination with 750 four-rod radio frequency quadrupole (RFQ). The is followed existing drift tube linac. Prior to installation, test was built which included and RFQ number measurement instrumentation. first showed an output energy deviation greater than 2.5%. Other problems also up led investigations...
The Spallation Neutron Source (SNS) linac accelerates 52-mA peak of pulsed H- particles to over 800 MeV. There are three types accelerating structure in which the beam position must be measured: drift-tube-linac (DTL); cavity-coupled-linac (CCL); and superconducting-linac (SCL)[1, 2]. Beam with a 402.5-MHz is injected into 402.5 MHz DTL, followed by 805-MHz CCL SCL structures. monitor pickups all shorted-microstrip type apertures 2.5-cm, 3-cm 7.3-cm-dia. In cases, we down convert signals...
Beam breakup (BBU) in linear induction accelerators (LIAs) used for flash radiography is problematic because the high-frequency beam motion can blur source spot, thereby degrading resolution. Amplification of BBU depends directly on details cell design and suppressed operation by solenoidal magnetic field focusing electron beam. Therefore, much effort has gone into cells new Scorpius LIA. In this article, we use computer simulations to demonstrate that should be no more than present LIAs at...
A general theory of the beam interaction with small discontinuities vacuum chamber an accelerator is developed taking into account reaction radiated waves back on discontinuity. The reactive impedance calculated earlier reproduced as first order and resistive one second a perturbation based this approach. also gives, in easy natural way, analytical results for frequencies coupling impedances trapped modes due to cross section. Formulas two important particular cases---a circular rectangular...
A new current structure for the fast traveling-wave 2.5 MeV beam chopper Spallation Neutron Source (SNS) project has been proposed. It is based on meander-folded straight or notched stripline with separators. Detailed electromagnetic modeling MAFIA used to optimize design and parameters. The time-domain 3D simulations predict rise fall times around 1 ns. meander line a dielectric substrate developed accommodate both mechanical requirements.
Beam energy loss in a cavity can be easily computed for relativistic bunch using time-domain codes like MAFIA or ABCI. However, nonrelativistic beams the problem is more complicated because of difficulties with its numerical formulation time domain. We calculate factors frequency domain as function velocity and compare results case.
The radio-frequency quadrupole (RFQ) accelerator is the best structure immediately after an ion source for accelerating light-ion beams with considerable currents. On other hand, higher-energy part of RFQ known to be not a very efficient accelerator. We consider alternative room-temperature RF structures beam velocities in range few percent speed light - including H-mode cavities and drift-tube linacs compare them respect their efficiency, compactness, ease fabrication, overall cost. Options...
A high-current emittance-compensated RF photoinjector is a key enabling technology for high-power CW FEL. The design presently under way 100-mA, 2.5-cell π-mode, 700-MHz, normal conducting demonstration photoinjector. This will be capable of accelerating 3 nC per bunch with an emittance at the wiggler less than 10 mm-mrad. paper presents results coupling from ridged waveguides to cavity. LEDA and SNS couplers inspired this dog-bone design. Electromagnetic modeling coupler-cavity system has...
It has been demonstrated recently [G. V. Stupakov and S. Kurennoy, Phys. Rev. E 49, 794 (1994)] that a single small discontinuity (such as an enlargement or hole) on smooth waveguide can result in the appearance of trapped electromagnetic modes with frequencies slightly below cutoff frequencies. The present paper studies similar phenomenon for many discontinuities, which is good model vacuum chamber large accelerators. Frequencies their contributions to coupling impedance are calculated....
The beam coupling impedances of small obstacles protruding inside the vacuum chamber an accelerator are calculated at frequencies for which wavelength is large compared to a typical size obstacle. Formulas few important particular cases including both essentially three-dimensional objects like post or mask and axisymmetric irises, presented. These results allow simple practical estimates broadband impedance contributions from such discontinuities.
We present a design of superconducting rf photonic band gap (SRF PBG) accelerator cell with specially shaped rods in order to reduce peak surface magnetic fields and improve the effectiveness PBG structure for suppression higher modes (HOMs). The ability structures suppress long-range wakefields is especially beneficial electron accelerators high power free-electron lasers (FELs), which are designed provide current continuous duty beams. Using prominent beam-breakup phenomena due HOMs will...