Electron beam diagnostics.
Spectroscopic electron beam diagnostic technique, examining negligible effect elevated vibrational temperatures have on measured rotational temperatures of molecular nitrogen
ELECTRON BEAM↗
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DEVELOPMENT OF A QUANTUM ELECTRON BEAM DIAGNOSTIC APPARATUS
Spatial properties of electron beams are the essential parameters needed in particle physics and accelerator research. Beam characterization using optical detection methods through the interaction between photons and electrons such as Compton scattering, or electro-optic sampling of the electric field of electrons have been extensively explored and successfully implemented as non-invasive diagnostics at various accelerator facilities. However, such methods often suffer from inherently low sensitivity. Here we present the study of a new type of electron beam diagnostic device for direct optical imaging of electron beams at various energy levels. The concept is based on the extremely high sensitivity of atoms, prepared in a specific "dark superposition" quantum state, to the external electric or magnetic perturbations induced by the passing charged particle, which allows atoms to change polarization of the probe light or absorb probe light and to fluoresce, enabling direct 3D imaging of the charged particles with high resolution. We report our recent experiment results and the design effort on a compact apparatus intended to be tested with the relativistic electron beams at Jefferson Laboratory.
Zhang, S.↗
Advanced Laser-driven Plasma Accelerator Electron-beam Diagnostics with COTR Techniques
A significant advance in laser-driven plasma accelerator (LPA) electron-beam diagnostics has recently been demonstrated based on coherent optical transition radiation (COTR) imaging. We find COTR signal strengths from a microbunched subset of beam exiting the LPA to be several orders of magnitude higher than that of incoherent optical transition radiation (OTR). The transverse sizes are only a few microns as deduced from the point-spread-function-related lobe structure. In addition, the far-field COTR interferometric images obtained on the same shot provide beam-size limits plus divergence and pointing information at the sub-mrad level when compared to a modified analytical model. The integrated image intensities can be used to estimate the microbunching fraction and relatable to the LPA process. Initial results in a collaborative LPA experiment will be reported for electron beam energies of about 215 MeV. A revised configuration is proposed to record energy and ene rgy spread via COTR on the same shot with the interferometer.
43 PARTICLE ACCELERATORS↗
On Possibilities of Using Edge Radiation for X-ray and Electron Beam Diagnostics at Bending Magnet Beamlines of NSLS-II
Spectral flux density distributions of long-wavelength Edge Radiation, i.e. radiation generated by relativistic electrons at edges of bending magnets in a storage ring are described, both analytically and numerically. Possibilities of using this radiation for the alignment of optical components of bending magnet beamlines at NSLS-II and for non-destructive X-ray and electron beam diagnostics at these beamlines are discussed.
43 PARTICLE ACCELERATORS↗
Electron-Beam Diagnostic Methods for Hypersonic Flow Diagnostics
The purpose of this work was the evaluation of the use of electron-bean fluorescence for flow measurements during hypersonic flight. Both analytical and numerical models were developed in this investigation to evaluate quantitatively flow field imaging concepts based upon the electron beam fluorescence technique for use in flight research and wind tunnel applications. Specific models were developed for: (1) fluorescence excitation/emission for nitrogen, (2) rotational fluorescence spectrum for nitrogen, (3) single and multiple scattering of electrons in a variable density medium, (4) spatial and spectral distribution of fluorescence, (5) measurement of rotational temperature and density, (6) optical filter design for fluorescence imaging, and (7) temperature accuracy and signal acquisition time requirements. Application of these models to a typical hypersonic wind tunnel flow is presented. In particular, the capability of simulating the fluorescence resulting from electron impact ionization in a variable density nitrogen or air flow provides the capability to evaluate the design of imaging instruments for flow field mapping. The result of this analysis is a recommendation that quantitative measurements of hypersonic flow fields using electron-bean fluorescence is a tractable method with electron beam energies of 100 keV. With lower electron energies, electron scattering increases with significant beam divergence which makes quantitative imaging difficult. The potential application of the analytical and numerical models developed in this work is in the design of a flow field imaging instrument for use in hypersonic wind tunnels or onboard a flight research vehicle.
Source record↗
Fiber-Optic Electro-Optic Sensors for Non-Destructive Electron Beam Diagnostics
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Rabiei, Payam [Partow Technologies LLC]↗
A compact, high resolution energy, and emittance diagnostic for electron beams using active plasma lenses
High-resolution (sub-%), single-shot energy distribution, and emittance measurements of GeV-class electron beams generated by laser plasma accelerators (LPAs) have been enabled through the use of an active plasma lens combined with relatively short dipole magnets. This setup, with only 60 cm between the LPA source and the final diagnostic screen, was facilitated through the use of a replenishable ∼20–40 nm thick liquid crystal plasma mirror to separate remnant laser radiation from the electron beam without emittance degradation. As LPAs capable of generating GeV-class electron beams at cm-scale distances become increasingly ubiquitous, there is a need to supplement these compact accelerators with equally compact diagnostics.
Barber, S. K. (ORCID:0000000172518755)↗
Single-shot ionization-based monitor for pulsed electron beams
In this work, we present an experimental demonstration of a single-shot, nondestructive electron beam diagnostic based on the ionization of a low-density pulsed gas jet. In our study, 7 MeV electron bunches from a radio-frequency photoinjector, carrying up to 100 pC of charge, traversed a localized distribution of nitrogen gas (N 2 ). The interaction of the electron bunches with the N 2 gas generated a correlated signature in the ionized particle distribution, which was spatially magnified using a series of electrostatic lenses and recorded with a microchannel-plate detector. Various modalities, including point-to-point imaging and velocity mapping, are investigated. A temporal trace of the detector current enabled the identification of single- and double-ionization events. The characteristics of the ionization distribution, dependence on gas density, total bunch charge, and other parameters, are described. Approaches to scaling to higher electron bunch density and energy are suggested. Additionally, the instrument proves useful for comprehensive studies of the ionization process itself.
47 OTHER INSTRUMENTATION↗
Assessment of errors in analytic modeling of permanent magnet electron spectrometers for laser-plasma accelerators
Here, we assess the error in three treatments of a critical electron beam diagnostic for laser-plasma acceleration (LPA) experiments: a permanent magnet electron spectrometer. Since LPA electron spectrometers are often difficult to calibrate due to the scarcity of well-characterized, tunable electron beam sources in the appropriate energy range and the mechanical complexity of electron spectrometers, the standard of calibration is Hall probe measurements. We first compare the electron spectrometer performance between SIMION calculations and the Hall probe measurements. We find up to a 60% (<8%) error in determining the absolute energy for electrons below (above) 80 MeV when using the SIMION-modeled magnetic field vs the measured magnetic field due to SIMION overpredicting fringe field strength. The difference in spectrometer energy resolution is within ∼10% between the modeled and measured fields. We then assess a simple block model, which is commonly used. We find that the simple block model presented here sufficiently captures the predicted as-built spectrometer performance for any application provided that the user can tolerate uncertainties on absolute energy determination up to 5% and errors on energy resolution up to 1%.
Electromagnetic optics↗
A novel nondestructive diagnostic method for mega-electron-volt ultrafast electron diffraction
Abstract A real-time, nondestructive, Bragg-diffracted electron beam energy, energy-spread and spatial-pointing jitter monitor is experimentally verified by encoding the electron beam energy and spatial-pointing jitter information into the mega-electron-volt ultrafast electron diffraction pattern. The shot-to-shot fluctuation of the diffraction pattern is then decomposed to two basic modes, i.e., the distance between the Bragg peaks as well as its variation (radial mode) and the overall lateral shift of the whole pattern (drift mode). Since these two modes are completely decoupled, the Bragg-diffraction method can simultaneously measure the shot-to-shot energy fluctuation from the radial mode with 2·10 −4 precision and spatial-pointing jitter from the drift mode having wide measurement span covering energy jitter range from 10 −4 to 10 −1 . The key advantage of this method is that it allows us to extract the electron beam energy spread concurrently with the ongoing experiment and enables online optimization of the electron beam especially for future high charge single-shot ultrafast electron diffraction (UED) and ultrafast electron microscopy (UEM) experiments. Furthermore, real-time energy measurement enables the filtering process to remove off-energy shots, improving the resolution of time-resolved UED. As a result, this method can be applied to the entire UED user community, beyond the traditional electron beam diagnostics of accelerators used by accelerator physicists.
43 PARTICLE ACCELERATORS↗
An Electron-Beam Ion-Neutralization Diagnostic for the Scorpius Radiography Accelerator
Electron beam spilling onto the beam pipe can produce positive ions that are accelerated inward into the beam body by its space charge. These ions partially neutralize the space charge, thereby causing the beam to be mismatched to the magnetic fields used for transport. A diagnostic of neutralization effects has been used on present accelerators, and in this note the feasibility of its use on a future accelerator is assessed.
43 PARTICLE ACCELERATORS↗
Attosecond electron bunch measurement with coherent nonlinear Thomson scattering
Not Available
74 ATOMIC AND MOLECULAR PHYSICS↗
The effect of filament peaking on electron beam weld quality
Electron beam welding uses high intensity beams that are generated by an electron emitting cathode under high vacuum conditions. The cathode, typically a ribbon or wire filament of refractory metal, must be heated to sufficiently high temperatures for electron emission to occur and must be carefully controlled to produce the desired beam current while at the same time optimizing filament lifetime. Traditional methods for doing this in commonly used triode gun assemblies consist of first finding the filament knee point in the filament current versus beam current relationship that produces the desired beam current for a given beam voltage. The filament current is then increased by some amount, typically 5–10%, per conventional wisdom to produce a peaked beam. This investigation studies and quantifies the beam and weld quality produced by underkneed and overpeaked filaments using electron beam diagnostics to measure the power density distribution of these beams. Underkneed filaments are shown to have power densities that drop off very quickly below the traditional knee, resulting in poor weld penetration. Kneed filaments do not reach the full beam intensity and also produce shallow welds. Increasing the filament current 10% above the traditional knee was shown to produce a circular Gaussian-like beam with peaked intensity optimized for welding and for filament lifetime. Further increases in the filament current that produce overpeaked beams do not significantly change the beam or weld quality and would only contribute to a reduced filament lifetime.
Electron Beam Welding↗
Applications of “Synchrotron Radiation Workshop” Code
The “Synchrotron Radiation Workshop” (SRW) computer code was started in the group of Insertion Devices of the European Synchrotron Radiation Facility in 1997. The idea behind it was to combine in one software library electrodynamics methods for calculating electric fields (and derived characteristics) of synchrotron radiation (SR) generated by relativistic electrons moving in magnetic fields of nearly arbitrary configuration with wave-optics methods for simulating propagation of radiation through optical elements of beamlines. Further, the use of this general approach was initially driven by applications in electron beam diagnostics using SR. However, with time it started to be used for more complicated beamlines of synchrotron light sources, and the use of the code for these applications continues to increase, with the new light sources offering brighter and more coherent x ray beams for wide ranges of experiments in different areas of science.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Virtual Diagnostic Suite for Electron Beam Prediction and Control at FACET-II
We discuss the implementation of a suite of virtual diagnostics at the FACET-II facility currently under commissioning at SLAC National Accelerator Laboratory. The diagnostics will be used for the prediction of the longitudinal phase space along the linac, spectral reconstruction of the bunch profile, and non-destructive inference of transverse beam quality (emittance) while using edge radiation at the injector dogleg and bunch compressor locations. These measurements will be folded into adaptive feedbacks and Machine Learning (ML)-based reinforcement learning controls to improve the stability and optimize the performance of the machine for different experimental configurations. In this paper we describe each of these diagnostics with expected measurement results that are based on simulation data and discuss progress towards implementation in regular operations.
Emma, Claudio (ORCID:0000000247191831)↗
Transverse uncorrelated emittance diagnostic for magnetized electron beams
Not Available
43 PARTICLE ACCELERATORS↗
Longitudinal bunch profile diagnostic for magnetized electron beams
Not Available
43 PARTICLE ACCELERATORS↗
Impulsive H-alpha diagnostics of electron-beam-heated solar flare model chromospheres
Time-dependent H-alpha profiles were computed for the dynamic model atmospheres of Fisher, Canfield, and McClymont (1985) simulating the effects of an intense impulsively initiated power-law beam of electrons incident on the chromosphere. The temporal response of H-alpha arises from three separate physical mechanisms, whose relative importance varies over the line profile. The fastest variations (typically less than 0.1 s for the explosive heating discussed here) arise from energy imbalance; these are apparent on chromospheric heating and cooling time scales and have their greatest amplitude at line center. Slower variations arise from ionization imbalance and are most apparent in the blue wing. The slowest variations arise from hydrodynamic effects and are related to the formation of a chromospheric condensation; these are most apparent in the red wing. These results provide a basis for the design and analysis of observations of H-alpha, in coordination with hard X-rays or microwaves, to test mechanisms of energy transport in solar flares.
Canfield, Richard C.↗