Engineering Papers⌕ Search

Engineering topics

Hirshfield, J L

Publications and source records attributed to Hirshfield, J L.

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Multi-harmonic RF test stand for RF breakdown studies

A multi-harmonic RF test stand is under construction at Yale Beam Physics Laboratory. It includes a frequency multiplier which can generate high power harmonics efficiently that are phase locked to the fundamental drive frequency. In a bi-modal asymmetric cavity powered by this RF source, the cavity may experience reduced exposure time to peak fields and sweeping of peak fields across their surfaces, and strong asymmetry between surfaces that may experience cathode-and anode-like fields; these phenomena are to be assessed for their influence on RF breakdown probabilities.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

RF undulator for compact X-ray SASE source of variable wavelength

A room-temperature RF undulator, fed by Ka-band radiation and intended to produce {approx}1 nm wavelength radiation using moderate energy electrons, is considered. The necessary electron bunches with energy 0.2-1 GeV could be produced by petawatt laser pulses injected into plasma bubbles.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Two-beam detuned-cavity electron accelerator structure

Progress has been made in the theory, development, cavity design and optimization, beam dynamics study, beam transport design, and hardware construction for studies of a detuned two-beam electron accelerator structure.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

X-Band Active-Passive Rf Pulse Compressor with Plasma Switches

As proposed by SLAC, the efficiency of a pulse compressor of the SLED-II type could be increased by changing both the phase of the microwave source and the coupling coefficient of the delay line. In the existing SLED-II system at frequency 11.4 GHz, the resonant delay line is coupled with the source via an iris with a constant reflection coefficient. Replacement of the iris with an active component makes it possible to create an active SLED-II system. In this paper, the use of plasma switches as the active elements is discussed. Plasma switches have been developed and tested at a high-power level for production of flattop compressed pulses. Active switching of SLED-II has demonstrated a marked increase in efficiency (by 20%) and power gain (by 37%) as compared with passive switching. The active compressor has produced 173 ns rf flattop output pulses with a power of about 112 MW.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Advanced High Gradient RF Structure Development

Multi-mode accelerating structures aimed at increasing accelerating gradient are described. Such structures operating in several resonant, equidistantly-spaced, axisymmetric, TM-like eigenmodes allow reduction of exposure time to surface fields, reduction of high-field areas and reduction of those fields which are responsible for electron emission. These effects are planned for use in studying the physics of RF breakdown phenomenon with the goal of designing new high-gradient accelerating structures.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

High Gradient Two-Beam Electron Accelerator

A high-gradient two-beam electron accelerator structure using detuned cavities is described. A self-consistent theory based on a circuit model is presented to calculate idealized acceleration gradient, transformer ratio, and efficiency for energy transfer from the drive beam to the accelerated beam. Experimental efforts are being carried out to demonstrate this acceleration concept.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Multi-Harmonic Cavities for Increasing RF Breakdown Threshold

A multi-harmonic asymmetric cavity is predicted to sustain higher acceleration gradients than a conventional pillbox cavity, 55% higher in one example, when driven by external RF harmonic sources. Simulations of multi-harmonic excitation in such a cavity are described, either by a charged drive beam or by external RF sources. An accelerator structure based on multi-harmonic cavity is proposed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

A THz Coaxial Two-Channel Dielectric Wakefield Structure for High Gradient Acceleration

A coaxial two-channel dielectric wakefield structure is examined for use as a high gradient accelerator. A THz design, having radius {approx}1 mm, is shown to provide GeV/m--level acceleration gradient, high transformer ratio, and stable accelerated bunch motion when excited by a stable-moving 5-GeV 6-nC annular drive bunch.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Two Channel Dielectric-Lined Rectangular High Transformer Ratio Accelerator Structure Experiment

Current status of a two-channel cm-scale rectangular dielectric lined wakefield accelerator structure is described. This structure is installed at the Argonne Wakefield Accelerator facility (AWA), and is presently being evaluated. The device has a transformer ratio of {approx}12.5:1. When driven by a {approx}50 nC single drive bunch it is expected to obtain {approx}6 MV/m acceleration gradient. Related issues are discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

High Power Microwave Switch Employing Electron Beam Triggering

A new type of switch for modulation of the Q-factor of a multi-mode storage resonator in a high-power active microwave pulse compressor is described. The operating principle of the switch is based on a sharp increase in the TE{sub 02{yields}}TE{sub 01} coupling coefficient, when an electron beam is injected into the switch cavity. The switch was tested at low power level in a compressor operated at X-band. A power gain of 19-20 in the compressed pulse with pulse duration of 40-50 ns was achieved. The proposed switch shows good prospects for use in high-power active pulse compressors.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Weakly Interacting Sub-eV Particle Searches

We make use of the generation-regeneration or 'light shining through a wall' technique in searches for optical-wavelength photons mixing with hypothetical hidden-sector paraphotons in the mass range between 10{sup -5} and 10{sup -2} electron volts for a mixing parameter greater than 10{sup -7} and in sensitive searches for scalar and pseudoscalar coupling of photons to light neutral bosons in the mass range of approximately 1.0 milli-electron volts and coupling strength greater than 10{sup -6} GeV{sup -1}. Additionally, there is an effort underway to use photons in the microwave region using this same technique to make a more sensitive measurement in the mass range of approximately 0.1 milli-electron volts. The equipment in the latter effort will be used to search for galactic halo axions in this same mass range.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗