Laser-controlled adaptive optic for beam quality enhancement in a multipass thin disk amplifier

We devise a laser-controlled adaptive optical element which operates intracavity under high intensity radiation. This element substitutes a conventional mechanically deformable mirror and is free of critical heat-sensitive components and electronics. The deformation mechanism is based on the projection of a CW control laser onto a specially designed mirror. Mounted to a water-cooled heat sink, the mirror can handle laser radiation beyond 3 MW/cm^2. The properties of the adaptive optical element including the maximum correctable wavefront pitch of 800 nm are discussed. The successful implementation in a multipass thin disk amplifier is presented. An improvement of the beam quality by a factor of three is achieved. We identify measures to enhance the performance of the adaptive optic towards efficient operation in a high-power laser system

Metallurgy In Costa-Rica

Anthropolog

Supersymmetric analysis for the Dirac equation with spin-symmetric and pseudo-spin-symmetric interactions

A supersymmetric analysis is presented for the d-dimensional Dirac equation with central potentials under spin-symmetric (S(r) = V(r)) and pseudo-spin-symmetric (S(r) = - V(r)) regimes. We construct the explicit shift operators that are required to factorize the Dirac Hamiltonian with the Kratzer potential. Exact solutions are provided for both the Coulomb and Kratzer potentials.Comment: 12 page

Power-Ups in Digital Games: The Rewarding Effect of Phantom Game Elementson Player Experience

Power-ups are a type of game reward that allow the player tocustomise their experience by altering gameplay for a shortperiod of time. Despite the wide use of power-ups in videogames, little is known about their effect on gaming experiences.To explore this, we conducted an experimental study that compares the experiences of players depending on their exposureto power-ups in a recreational video game. The results show that players who collected power-ups felt significantly more immersed in the game, experienced more autonomy, but didnot feel more competent or challenged than those who played the game without these collectables. Interestingly, a similareffect was observed for those players who picked up ‘placebo ’power-ups, despite the items having no effect on the gameplay. We provide a discussion of these results and their implications both for games user researchers and game designers

National minimum wages improve productivity

Government and firms may not grasp the potential for significant productivity advances, write Richard Croucher, Marian Rizov and Thomas Lang

A journey around my classroom: the psychogeography of learning spaces

During a workshop held at the UAL Learning and Teaching Day we led a session where we used a number of techniques to disrupt the traditional format of a classroom or lecture space. Lectures and classrooms are often associated with static, immovable furniture organised in neat rows, all facing towards a whiteboard or screen, affording specific pedagogies, behaviours, rules and power structures. Our aim in the workshop was to challenge participants’ preconceptions of what might happen in such spaces. Using our observations and reflections on the workshop, this article explores how participants responded to and engaged with the different structures and activities imposed