Effects of bunched ion bursts on apparent nonlinear ion acoustic waves
Bunched ion bursts amplitude modulation effects on nonlinear ion acoustic waves in grid plasma system
Ichikawa, Y. H.↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Phase-bunching and other non-linear processes occurring in gyroresonant wave-particle interactions
Consideration of the movement of individual electrons in a magnetized plasma in which a monochromatic wave is propagating in the whistler mode. Simple expressions are derived which give the displacement of the electrons as a function of time, the phase angle that their velocity vector makes with the magnetic component of the wave, their pitch angle, and energy changes. A useful formula is obtained which gives the velocity range over which particles remain trapped inside the wave, as a function of the wave intensity and of the initial phase angle of the particle. It is shown that even strictly resonant particles can escape from the wave when their initial phase angle is very small. From the derived expressions, it is possible to compute the phase-bunching effect which occurs approximately at one trapping wavelength behind the leading edge of the interaction region.
Gendrin, R.↗
SAR imaging of waves in water and ice - Evidence for velocity bunching
Synthetic aperture radar (SAR) images collected over the Arctic marginal ice zone show gravity wave patterns in both the open water and the ice. Diffuse wave patterns are visible in the water at near range (small incidence angles), while most distinct wave patterns are visible in the ice across the entire swath. The wave patterns in the ice appear as bright lines rather than sinusoidal intensity variations. Additionally, the images show a periodic displacement of the ice/water boundary, apparently due to Doppler shift effects associated with the gravity wave orbital motions. These observations are interpreted as evidence for the velocity bunching effect and also illustrate the effects of random scatterer motions in the open water.
Lyzenga, D. R.↗
A component of nongyrotropic (phase-bunched) electrons upstream from the earth's bow shock
The count rates of 1.5- and 6-keV electrons measured on ISEE 1 and ISEE 2 are at times strongly spin modulated despite the fact that the axes of the detectors lie along the spin axis of the spacecraft. Spatial gradients in the guiding center density are ruled out as a cause of the spin modulation. The characteristics of the spin modulation can be explained if the electron velocity distribution is nongyrotropic. The procedure is to show that the direction of the plasma flow velocity during times of spin modulation does not lie along the direction of the local magnetic field when both are projected onto the ecliptic plane. While a gyrotropic distribution will cause spin modulation, the count rate maximum will correspond to the direction of the local magnetic field. Gyrophase-bunched electrons are seen within a few tens of kilometers of the shock and as far upstream as 30,000 km from the shock, suggesting that a wave is associated with their propagation. The magnetosheath electrons in the same energy range are also nongyrotropic at times.
Anderson, K. A.↗
Steps in Solution Growth: Dynamics of Kinks, Bunching and Turbulence
Summary of recent results on fundamental issues in crystal growth from non-stoichiometric solutions, development of steps with low kink density and influence of turbulence on step bunching.
Chernov, A. A.↗
Subpicosecond electron bunch train production using a phase-space exchange technique
Our recent experimental demonstration of a photoinjector electron bunch train with sub-picosecond structures is reported in this paper. The experiment is accomplished by converting an initially horizontal beam intensity modulation into a longitudinal phase space modulation, via a beamline capable of exchanging phase-space coordinates between the horizontal and longitudinal degrees of freedom. The initial transverse modulation is produced by intercepting the beam with a multislit mask prior to the exchange. We also compare our experimental results with numerical simulations.
43 PARTICLE ACCELERATORS↗
INDEPENDENT COMPONENT ANALYSIS (ICA) APPLIED TO LONG BUNCH BEAMS IN THE LOS ALAMOS PROTON STORAGE RING
Independent component analysis (ICA) is a powerful blind source separation (BSS) method. Compared to the typical BSS method, principal component analysis (PCA), which is the BSS foundation of the well known model independent analysis (MIA), ICA is more robust to noise, coupling, and nonlinearity. ICA of turn-by-turn beam position data has been used to measure the transverse betatron phase and amplitude functions, dispersion function, linear coupling, sextupole strength, and nonlinear beam dynamics. We apply ICA in a new way to slices along the bunch and discuss the source signals identified as betatron motion and longitudinal beam structure.
43 PARTICLE ACCELERATORS↗
E-Cloud Effects on Singe-Bunch Dynamics in the Proposed PS2
One of the options considered for future upgrades of the LHC injector complex entails the replacement of the PSwith the PS2, a longer circumference and higher energy synchrotron. Electron cloud effects represent an importantpotential limitation to the achievement of the upgrade goals. We report the results of numerical studies aimingat estimating the e-cloud density thresholds for the occurrence of single bunch instabilities.
43 PARTICLE ACCELERATORS↗
Optimization of Drive-Bunch Current Profile for Enhanced Transformer Ratio in Beam-Driven Acceleration Techniques
In recent years, wakefield acceleration has gained attention due to its high acceleration gradients and cost effectiveness. In beam-driven wakefield acceleration, a critical parameter to optimize is the transformer ratio. It has been shown that current shaping of electron beams allows for enhanced (> 2) transformer ratios. In this paper we present the optimization of the pulse shape of the drive bunch for dielectric-wakefield acceleration.
43 PARTICLE ACCELERATORS↗
Method of controlling coherent synchroton radiation-driven degradation of beam quality during bunch length compression
A method of avoiding CSR induced beam quality defects in free electron laser operation by a) controlling the rate of compression and b) using a novel means of integrating the compression with the remainder of the transport system: both are accomplished by means of dispersion modulation. A large dispersion is created in the penultimate dipole magnet of the compression region leading to rapid compression; this large dispersion is demagnified and dispersion suppression performed in a final small dipole. As a result, the bunch is short for only a small angular extent of the transport, and the resulting CSR excitation is small.
47 OTHER INSTRUMENTATION↗
Magnetic Bunch Compression for a Compact Compton Source
A compact electron accelerator suitable for Compton source applications is in design at the Center for Accelerator Science at Old Dominion University and Jefferson Lab. Here we discuss two options for transverse magnetic bunch compression and final focus, each involving a 4-dipole chicane with M_{56} tunable over a range of 1.5-2.0m with independent tuning of final focus to interaction point $\beta$*=5mm. One design has no net bending, while the other has net bending of 90 degrees and is suitable for compact corner placement.
43 PARTICLE ACCELERATORS↗
Bunch length compression method for free electron lasers to avoid parasitic compressions
A method of bunch length compression method for a free electron laser (FEL) that avoids parasitic compressions by 1) applying acceleration on the falling portion of the RF waveform, 2) compressing using a positive momentum compaction (R.sub.56>0), and 3) compensating for aberration by using nonlinear magnets in the compressor beam line.
42 ENGINEERING↗
Commissioning of the 112 MHz SRF Gun and 500 MHz bunching cavities for the CeC PoP Linac
The Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL includes a short electron linac. During Phase 1, a 112 MHz superconducting RF photo-emission gun and two 500 MHz normal conducting bunching cavities were installed and are under commissioning. The paper describes the Phase1 linac layout and presents commissioning results for the cavities and associated RF, cryogenic and other sub-systems
43 PARTICLE ACCELERATORS↗
R & D on Beam Injection and Bunching Schemes in the Fermilab Booster
Fermilab is committed to upgrade its accelerator complex to support HEP experiments at the intensity frontier. The ongoing Proton Improvement Plan (PIP) enables us to reach 700 kW beam power on the NuMI neutrino targets. By the end of the next decade, the current 400 MeV normal conducting LINAC will be replaced by an 800 MeV superconducting LINAC (PIP-II) with an increased beam power >50% of the PIP design goal. Both in PIP and PIP-II era, the existing Booster is going to play a very significant role, at least for next two decades. In the meanwhile, we have recently developed an innovative beam injection and bunching scheme for the Booster called "early injection scheme" that continues to use the existing 400 MeV LINAC and implemented into operation. This scheme has the potential to increase the Booster beam intensity by >40% from the PIP design goal. Some benefits from the scheme have already been seen. In this paper, I will describe the basic principle of the scheme, results from recent beam experiments, our experience with the new scheme in operation, current status, issues and future plans. This scheme fits well with the current and future intensity upgrade programs at Fermilab.
Bhat, C. M.↗
Theoretical Modeling of Electromagnetic Field from Electron Bunches in Periodic Wire Medium
The interaction of relativistic electrons with periodic conducting structures results in radiation via a number of mechanisms. In case of crystals one obtains parametric X-ray radiation, its frequency is determined by the distance between crystallographic planes and the direction of electron beam. If instead of a crystal one considers a periodic structure of metallic wires with the spacing of the order of mm, it is plausible to expect the emission of radiation of a similar nature (“diffraction response”) at THz frequencies. Additionally, a “long-wave” radiation will occur in this case with wavelengths much larger then structure periods. In this contribution, we present different theoretical approaches for describing the electromagnetic radiation field from prolonged electron bunch propagated in the lattice of metallic wires. The validity of these analytical descriptions is checked by numerical simulations. We discuss the possible applications of aforementioned structure as sources of coherent THz radiation.
43 PARTICLE ACCELERATORS↗
Electron Beam Pattern Rotation as a Method of Tunable Bunch Train Generation
Transversely modulated electron beams can be formed in photo injectors via microlens array (MLA) UV laser shap- ing technique. Microlenses can be arranged in polygonal lattices, with resulting transverse electron beam modula- tion mimicking the lenses pattern. Conventionally, square MLAs are used for UV laser beam shaping, and generated electron beam patterns form square beamlet arrays. The MLA setup can be placed on a rotational mount, thereby rotating electron beam distribution. In combination with transverse-to-longitudinal emittance exchange (EEX) beam line, it allows to vary beamlets horizontal projection and tune electron bunch train. In this paper, we extend the technique to the case of different MLA lattice arrangements and explore the benefits of its rotational symmetries.
43 PARTICLE ACCELERATORS↗
Using Time Evolution of the Bunch Structure to Extract the Muon Momentum Distribution in the Fermilab Muon g-2 Experiment
Beam dynamics plays an important role in achieving the unprecedented precision on measurement of the muon anomalous magnetic moment in the Fermilab Muon g-2 Experiment. It needs to find the muon momentum distribution in the storage ring in order to evaluate the electric field correction to muon anomalous precession frequency. We will show how to use time evolution of the beam bunch structure to extract the muon momentum distribution by applying a fast rotation analysis on the decay electron signals.
43 PARTICLE ACCELERATORS↗
Using Time Evolution of the Bunch Structure to Extract the Muon Momentum Distribution in the Fermilab Muon g-2
Beam dynamics plays an important role in achieving the unprecedented precision on measurement of the muon anomalous magnetic moment in the Fermilab Muon g-2 Experiment. It needs to find the muon momentum distribution in the storage ring in order to evaluate the electric field correction to muon anomalous precession frequency. We will show how to use time evolution of the beam bunch structure to extract the muon momentum distribution by applying a fast rotation analysis on the decay electron signals.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗