John Petillo
YOU?
Author Swipe
View article: Multiphysics modeling of accelerators through code integration
Multiphysics modeling of accelerators through code integration Open
This work aims to improve the ability of particle accelerator researchers to develop high-performance accelerator cavity designs by creating an overall multiphysics framework that integrates and couples existing application codes. This fra…
View article: Editorial—Announcing 2023 TPS Best Paper Award
Editorial—Announcing 2023 TPS Best Paper Award Open
The winner of the 2023 TPS Best Paper Award has been selected (please refer to our TPS home page for details about the award at https://ieee-npss.org/publications/transactions-on-plasma-science/ ). This year is the fifth year that the awar…
View article: Physics-based Model for Nonuniform Thermionic Electron Emission from Polycrystalline Cathodes
Physics-based Model for Nonuniform Thermionic Electron Emission from Polycrystalline Cathodes Open
Experimental observations of thermionic electron emission demonstrate a smooth transition between TL and FSCL regions of the emitted-current-density-versus-temperature (J-T) (Miram) curve and the emitted-current-density-versus-voltage (J-V…
View article: Analysis of Anode Current From a Thermionic Cathode With a 2-D Work Function Distribution
Analysis of Anode Current From a Thermionic Cathode With a 2-D Work Function Distribution Open
A model of a thermionic cathode in a planar diode in which the Poisson and Vlasov equations are solved in 3-D assuming an infinite magnetic field is presented. We explore how 2-D work function variations across the cathode surface may affe…
View article: An extended moments model of quantum efficiency for metals and semiconductors
An extended moments model of quantum efficiency for metals and semiconductors Open
The complexity of photocathode designs and detector materials, and the need to model their performance for short pulse durations, the response to high-frequency photons, the presence of coatings and/or thinness of the absorptive layer, nec…
View article: Analytic model of electron transport through and over non-linear barriers
Analytic model of electron transport through and over non-linear barriers Open
Tunneling barriers are an essential component of electron sources, sensors, detectors, and vacuum nanoelectronics, and a pivotal factor in their performance, but the barriers themselves routinely depart from the analytic models used to mod…
View article: Effect of Nonuniform Emission on Miram Curves
Effect of Nonuniform Emission on Miram Curves Open
Analysis of temperature-limited flow, space-charge-limited flow, and the transition between them using a simple planar diode with a thermionic cathode, in which the cathode surface has spatially nonuniform emission properties, is presented…
View article: Thermal-field and photoemission from meso- and micro-scale features: Effects of screening and roughness on characterization and simulation
Thermal-field and photoemission from meso- and micro-scale features: Effects of screening and roughness on characterization and simulation Open
A methodology of modeling nonplanar surfaces, in which the microscale features of the emission sites can be orders of magnitude smaller than the mesoscale features defining the active emission area, has been developed and applied to both o…
View article: Single Objective Genetic Optimization of an 85% Efficient Klystron
Single Objective Genetic Optimization of an 85% Efficient Klystron Open
Overall efficiency is a critical priority for the next generation of particle accelerators as they push to higher and higher energies. In a large machine, even a small increase in efficiency of any subsystem or component can lead to a sign…
View article: Adjoint Approach to Beam Optics Sensitivity Based on Hamiltonian Particle Dynamics
Adjoint Approach to Beam Optics Sensitivity Based on Hamiltonian Particle Dynamics Open
We develop a sensitivity function for the design of electron optics using an adjoint approach based on a form of reciprocity implicit in Hamilton's equations of motion. The sensitivity function, which is computed with a small number of tim…
View article: Adjoint Approach to Beam Optics Sensitivity Based on Hamiltonian\n Particle Dynamics
Adjoint Approach to Beam Optics Sensitivity Based on Hamiltonian\n Particle Dynamics Open
We develop a sensitivity function for the design of electron optics using an\nadjoint approach based on a form of reciprocity implicit in Hamilton's\nequations of motion. The sensitivity function, which is computed with a small\nnumber of …
View article: Analytical models of transmission probabilities for electron sources
Analytical models of transmission probabilities for electron sources Open
Electron emission from coated surfaces as a result of thermal, field, and photoemission effects is often described theoretically using models dependent on the Kemble approximation for the transmission probability D(k). The validity of the …
View article: A photoemission moments model using density functional and transfer matrix methods applied to coating layers on surfaces: Theory
A photoemission moments model using density functional and transfer matrix methods applied to coating layers on surfaces: Theory Open
Recent experimental measurements of a bulk material covered with a small number of graphene layers reported by Yamaguchi et al. [NPJ 2D Mater. Appl. 1, 12 (2017)] (on bialkali) and Liu et al. [Appl. Phys. Lett. 110, 041607 (2017)] (on copp…
View article: Modeling emission lag after photoexcitation
Modeling emission lag after photoexcitation Open
A theoretical model of delayed emission following photoexcitation from metals and semiconductors is given. Its numerical implementation is designed for beam optics codes used to model photocathodes in rf photoinjectors. The model extends t…
View article: Delayed photo-emission model for beam optics codes
Delayed photo-emission model for beam optics codes Open
Future advanced light sources and x-ray free electron lasers require fast response from the photocathode to enable short electron pulse durations as well as pulse shaping, and so the ability to model delays in emission is needed for beam o…
View article: 2D/3D image charge for modeling field emission
2D/3D image charge for modeling field emission Open
Analytic image charge approximations exist for planar and spherical metal surfaces but approximations for more complex geometries, such as the conical and wirelike structures characteristic of field emitters, are lacking. Such models are t…
View article: Schottky’s conjecture, field emitters, and the point charge model
Schottky’s conjecture, field emitters, and the point charge model Open
A Point Charge Model of conical field emitters, in which the emitter is defined by an equipotential surface of judiciously placed charges over a planar conductor, is used to confirm Schottky’s conjecture that field enhancement factors are …
View article: Discrete space charge affected field emission: Flat and hemisphere emitters
Discrete space charge affected field emission: Flat and hemisphere emitters Open
Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models propose…