127 research outputs found
Tapering Enhanced Stimulated Superradiant Oscillator
In this paper, we present a new kind of high power and high efficiency
free-electron laser oscillator based on the application of the tapering
enhanced stimulated superradiant amplification (TESSA) scheme. The main
characteristic of the TESSA scheme is a high intensity seed pulse which
provides high gradient beam deceleration and efficient energy extraction. In
the oscillator configuration, the TESSA undulator is driven by a high
repetition rate electron beam and embedded in an optical cavity. A
beam-splitter is used for outcoupling a fraction of the amplified power and
recirculate the remainder as the intense seed for the next electron beam pulse.
The mirrors in the oscillator cavity refocus the seed at the undulator entrance
and monochromatize the radiation. In this paper we discuss the optimization of
the system for a technologically relevant example at 1 m using a 1~MHz
repetition rate electron linac starting with an externally injected igniter
pulse.Comment: 24 pages, 13 figure
Summary Report Topical Group on Application and Industry Community Engagement Frontier Snowmass 2021
HEP community leads and operates cutting-edge experiments for the DOE Office
of Science which have challenging sensing, data processing, and computing
requirements that far surpass typical industrial applications. To make
necessary progress in the energy, material, and fundamental sciences,
development of novel technologies is often required to enable these advanced
detector and accelerator programs. Our capabilities include efficient
co-design, which is a prerequisite to enable the deployment of advanced
techniques in a scientific setting where development spans from rapid
prototyping to robust and reliable production scale. This applies across the
design spectrum from the low level fabrication techniques to the high level
software development. It underpins the requirement for a holistic approach of
innovation that accelerates the cycle of technology development and deployment.
The challenges set by the next generation of experiments requires a
collaborative approach between academia, industry and national labs. Just a
single stakeholder will be unable to deliver the technologies required for the
success of the scientific goals. Tools and techniques developed for High Energy
Physics (HEP) research can accelerate scientific discovery more broadly across
DOE Office of Science and other federal initiatives and also benefit industry
applications
Amp\`ere-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator
Pulsed field emission from cold carbon-nanotube cathodes placed in a
radiofrequency resonant cavity was observed. The cathodes were located on the
backplate of a conventional -cell resonant cavity operating at
1.3-GHz and resulted in the production of bunch train with maximum average
current close to 0.7 Amp\`ere. The measured Fowler-Nordheim characteristic,
transverse emittance, and pulse duration are presented and, when possible,
compared to numerical simulations. The implications of our results to
high-average-current electron sources are briefly discussed.Comment: 5 pages, 6 figures; submitted to Applied Physics Letter
Nanometer Thick Diffused Hafnium and Titanium Oxide Light Sensing Film Structures
We examine 10 nm thick film structures containing either Hf or Ti sandwiched between two respective oxide layers.The layers are deposited onto heated substrates to create a diffusion region.We observe a high degree of light sensitivity of the electric current through the film thickness for one polarity of an applied voltage. For the other polarity, the current is not affected by the light. We explain the observed phenomenology using the single-particle model based on the existence of interface states on the metal-oxide interfaces
Upgrades of beam diagnostics in support of emittance-exchange experiments at the Fermilab A0 photoinjector
The possibility of using electron beam phase space manipulations to support a
free-electron laser accelerator design optimization has motivated our research.
An on-going program demonstrating the exchange of transverse horizontal and
longitudinal emittances at the Fermilab A0 photoinjector has benefited recently
from the upgrade of several of the key diagnostics stations. Accurate
measurements of these properties upstream and downstream of the exchanger
beamline are needed. Improvements in the screen resolution term and reduced
impact of the optical system's depth-of-focus by using YAG:Ce single crystals
normal to the beam direction will be described. The requirement to measure
small energy spreads (<10 keV) in the spectrometer and the exchange process
which resulted in bunch lengths less than 500 fs led to other diagnostics
performance adjustments and upgrades as well. A longitudinal to transverse
exchange example is also reported.Comment: 16 p
Electron beam profile imaging in the presence of coherent optical radiation effects
High-brightness electron beams with low energy spread at existing and future
x-ray free-electron lasers are affected by various collective beam
self-interactions and microbunching instabilities. The corresponding coherent
optical radiation effects, e.g., coherent optical transition radiation, render
electron beam profile imaging impossible and become a serious issue for all
kinds of electron beam diagnostics using imaging screens. Furthermore, coherent
optical radiation effects can also be related to intrinsically ultrashort
electron bunches or the existence of ultrashort spikes inside the electron
bunches. In this paper, we discuss methods to suppress coherent optical
radiation effects both by electron beam profile imaging in dispersive beamlines
and by using scintillation imaging screens in combination with separation
techniques. The suppression of coherent optical emission in dispersive
beamlines is shown by analytical calculations, numerical simulations, and
measurements. Transverse and longitudinal electron beam profile measurements in
the presence of coherent optical radiation effects in non-dispersive beamlines
are demonstrated by applying a temporal separation technique.Comment: 12 pages, 11 figures, submitted to Phys. Rev. ST Accel. Beam
Tunable Electron Multibunch Production in Plasma Wakefield Accelerators
Synchronized, independently tunable and focused J-class laser pulses are
used to release multiple electron populations via photo-ionization inside an
electron-beam driven plasma wave. By varying the laser foci in the laboratory
frame and the position of the underdense photocathodes in the co-moving frame,
the delays between the produced bunches and their energies are adjusted. The
resulting multibunches have ultra-high quality and brightness, allowing for
hitherto impossible bunch configurations such as spatially overlapping bunch
populations with strictly separated energies, which opens up a new regime for
light sources such as free-electron-lasers
DESIGN FOR A FAST, XFEL-QUALITY WIRE SCANNER
Abstract RadiaBeam Technologies has designed and manufactured a new wire scanner for high-speed emittance measurements of XFEL-type beams of energy 139 MeV. Using three 25-micron thick tungsten wires, this wire scanner measures vertical and horizontal beam size as well as transverse spatial correlation in one pass. The intensity of the beam at a wire position is determined from emitted bremsstrahlung photons as measured by a BGO scintillator system. The wires are transported on a two-ended support structure moved by a ball-screw linear stage. The doubleended structure reduces vibrations in the wire holder, and the two-bellows design negates the effects of air pressure on the motion. The expected minimum beam size measurable by this system is on the order of 10 microns with 0.1-micron accuracy. To achieve this, new algorithms are presented that reduce the effect of the non-zero thickness of the wire on the wire scan output. In addition, novel calculations are presented for determining the elliptical geometric parameters (vertical and horizontal beam size and correlation, or alternatively, the axis lengths and rotation) of the beam from the wire scanner measurements
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