arXiv subjects

Levi Schachter

Publications and source records attributed to Levi Schachter.

4 recordsLinked to original sources

arXiv2023

Efficiency of gratings for silica fiber-coupled internal Smith-Purcell radiation and Cherenkov diffraction radiation -- a quantitative numerical study

We propose a setup for measuring visible and near-visible internal Smith-Purcell radiation and Cherenkov Diffraction Radiation, based on silica and silicon, and perform quantitative numerical analysis of its radiation efficiency. We calculate the total radiated energy per electron and the spectral distribution of different radiation orders, taking into account material dispersion and absorption. For an optimized silica grating of 200 micrometer length, the total radiated energy reaches 2~eV per electron for 2 MeV electrons. Above the Cherenkov threshold, in most cases the energy of Cherenkov diffraction radiation is several times higher than the energy of internal Smith-Purcell radiation, but for some geometries and frequency ranges first or second order radiation may dominate over Cherenkov radiation (zeroth order). Radiation up to the 4th order is detected in the simulation. The spectrum of Cherenkov radiation is highly resonant, with local minima for frequencies where maxima of the other radiation orders occur. The spectrum of Cherenkov radiation takes a frequency comb-like shape for a uniform layer of Si on SiO2 substrate, due to a Fabry-Perot effect occurring for the evanescent field of the moving electron. The proposed setup could become a prototype of a non-invasive particle beam monitor for both conventional and laser particle accelerators.

physics.optics↗

arXiv2021

Beam-Beam Interaction in a Dielectric Laser Accelerator Electron-Positron Collider

We examine through numerical calculation the collision of counter-propagating trains of optically spaced electron/positron microbunches in a 1 TeV collider scenario for a dielectric laser accelerator (DLA). A time-dependent envelope equation is derived for arbitrary number of bunches in the classical limit, with inclusion of the radiation reaction force (RRF). Example parameters are examined based on a constrained luminosity relation that takes into account the bunch charge for optimal efficiency, material damage limits, and power constraints. We find that for initially identical counter-propagating Gaussian bunch trains the periodic temporal structure leads to a peak in luminosity with number of bunches. For longer bunch trains, the enhancement then decreases inversely with number of bunches. The corresponding fractional energy loss of the beam is found to be of order 1.75\%, which is reduced to 0.35\% when the nonlinear radial dependence of the transverse force is included, with an average beamstrahlung parameter of 0.075, an important result considering that beamstrahlung losses are a critical concern for future TeV colliders.

physics.acc-ph↗

arXiv2020

Frequency-domain calculation of Smith-Purcell radiation for metallic and dielectric gratings

The intensity of Smith-Purcell radiation from metallic and dielectric gratings (silicon, silica) is compared in a frequency-domain simulation. The numerical model is discussed and verified with the Frank-Tamm formula for Cherenkov radiation. For 30 keV electrons, rectangular dielectric gratings are less efficient than their metallic counterpart, by an order of magnitude for silicon, and two orders of magnitude for silica. For all gratings studied, radiation intensity oscillates with grating tooth height due to electromagnetic resonances in the grating. 3D and 2D numerical models are compared.

physics.acc-ph↗

arXiv2006

Studies of Particle Acceleration by an Active Microwave Medium

The PASER is potentially a very attractive method for particle acceleration, in which energy from an active medium is transferred to a charged particle beam. The effect is similar to the action of a maser or laser with the stimulated emission of radiation being produced by the virtual photons in the electromagnetic field of the beam. We have been investigating the possibility of developing a demonstration PASER operating at X-band. The less restrictive beam transport and device dimensional tolerances required for working at X-band rather than optical frequencies as well as the widespread application of X-band hardware in accelerator technology all contribute to the attractiveness of performing a PASER demonstration experiment in this frequency range. Key to this approach is the availability of a new class of active materials that exhibit photoinduced electron spin polarization. We will report on the status of active material development and measurements, numerical simulations, and progress towards a planned microwave PASER acceleration experiment at the Argonne Wakefield Accelerator facility.

physics.acc-ph↗