The Hottest Spot on Campus

In support of an experiment designed to measure the strength of radiation scattered from low-density free electrons in an intense laser focus, we model a variety of physical parameters that impact the rate of scattered photons. We employ a classical model to characterize duration of electron exposure to high-intensity laser light in a situation where the electrons are driven by strong ponderomotive gradients. Free electrons are modeled as being donated by low-density helium, which undergoes strong-field ionization early in the pulse or during a prepulse. When exposed to relativistic intensities, free electrons experience a Lorentz drift that causes redshifting of the scattered 800 nm light. This redshift can be used as a signature to discern light scattered from the more intense regions of the focus. We characterize the focal volume of initial positions leading to significant redshifting, given a peak intensity of 2 × 10¹⁸ W∕cm2. Under this scenario, the beam waist needs to be larger than several wavelengths for a pulse duration of 35 fs. We compute the rate of redshifted scattered photons from an ensemble of electrons distributed throughout the focus and relate the result to the scattered-photon rate of a single electron. We also estimate to what extent the ionization process may produce unwanted light in the redshifted spectral region.

Pulse reshaping effects that give rise to fast and slow light phenomena are inextricably linked to the dynamics of energy exchange between the pulse and the propagation medium. Energy that is dissipated from the pulse can no longer participate in this exchange process, but previous methods of calculating real-time dissipation are not valid for extended propagation media. We present a method for calculating real-time dissipation that is valid for electromagnetic pulse propagation in extended media. This method allows one to divide the energy stored in an extended medium into the portion that can be later transmitted out of the medium, and that portion which must be lost to either dissipation or reflection.

The idea of a book being a collection of pages is so ingrained that modern electronic book readers often try to faithfully reproduce this feature--up to elaborate simulations of page turns. However, traditional pages are not necessary and often inconvenient in electronic books. It is often easier to scroll the text than to turn the pages, and text reflowing makes the use of folios a rather strange way to refer to the position inside a text. We argue that it is more natural to paginate electronic books according to their logical structure, when a \page" corresponds to a sectional unit of the book. This leads to rather long pages, with the height of the page depending on the length of the corresponding unit. We discuss how to implement these pages in TEX and provide a basic introduction to output routines in TEX for a beginning TEXnician. We also provide exercises for a slightly more advanced reader.