HICS: Highly charged ion collisions with surfaces
Abstract The layout of a new instrument designed to study the interaction of highly charged ions with surfaces, which consists of an ion source, a beamline including charge separation and a target chamber, is presented here. By varying the charge state and impact velocity of the projectiles separately, the dissipation of potential and kinetic energy at or below the surface can be studied independently. The target chamber offers the use of tunable metal–insulator–metal devices as detectors for internal electronic excitation, a time-of-flight system to study the impact induced particle emission and the possibility to transfer samples in situ to an ultra high vacuum (UHV) scanning probe microscope. Samples and detectors can be prepared in situ as well. As a first example data on graphene layers on SrTiO3 which have been irradiated with Xe36+ are presented.
Atomic-force-microscopy observations of tracks induced by swift Kr ions in mica.
For the first time, latent tracks induced by swift Kr ions have been directly observed in mica. These tracks are imaged by atomic force microscopy as hollows which are associated with softer areas in the mica surface. The track core is formed by disordered mica. The mean diameter of the observed hollows increases with the electronic stopping power of the ions. The track shape along the ion path is deduced from the analysis of both the number of the tracks per unit area and their diameter distribution. These observations are the first images of nanometric changes of elastic properties
Randi Weingarten, the American Federation of Teachers, and the Challenges of Policy Leadership in a Hostile Environment
Randi Weingarten is the president of the most vocal and influential teachers’ union, the American Federation of Teachers. Since rising through the ranks to AFT president in just two years, Weingarten is now a major, if not the most prominent, nongovernmental player in national education policy. She has earned deep respect from many educational policy actors. Likewise, Weingarten elicits withering criticism from others. This fascinating profile explains why, in such a brief period, she has proved to be a fierce, fearless, and effective leader under extraordinarily difficult circumstances. Her experience offers invaluable lessons applicable for others working in similarly intense policy arenas.