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Hernan Quevedo

Publications and source records attributed to Hernan Quevedo.

2 recordsLinked to original sources
arXiv2022

A Scintillator Attenuation Spectrometer For Intense Gamma-Rays

A new type of compact high resolution high sensitivity gamma ray spectrometer for short pulse intense 250 keV to 50 MeV gamma rays has been developed by combining the principles of scintillators and attenuation spectrometers. The first prototype of this scintillator attenuation spectrometer or SAS was tested successfully in Trident laser experiments at LANL. Later versions have been used extensively in the Texas Petawatt laser experiments in Austin TX, and more recently in OMEGAEP laser experiments at LLE, Rochester, NY. The SAS is particularly useful for high repetition rate laser applications. Here we give a concise description of the design principles, capabilities and sample preliminary results of the SAS.

physics.ins-det↗
arXiv2021

Emission of electromagnetic waves as a stopping mechanism for nonlinear collisionless ionization waves in a high-$β$ regime

A high energy density plasma embedded in a neutral gas is able to launch an outward-propagating nonlinear electrostatic ionization wave that traps energetic electrons. The trapping maintains a strong sheath electric field, enabling rapid and long-lasting wave propagation aided by field ionization. Using 1D3V kinetic simulations, we examine the propagation of the ionization wave in the presence of a transverse MG-level magnetic field with the objective to identify qualitative changes in a regime where the initial thermal pressure of the plasma exceeds the pressure of the magnetic field ($β>1$). Our key finding is that the magnetic field stops the propagation by causing the energetic electrons sustaining the wave to lose their energy by emitting an electromagnetic wave. The emission is accompanied by the magnetic field expulsion from the plasma and an increased electron loss from the trapping wave structure. The described effect provides a mechanism mitigating rapid plasma expansion for those applications that involve an embedded plasma, such as high-flux neutron production from laser-irradiated deuterium gas jets.

physics.plasm-ph↗