NEW ASPECTS OF X-RAY LASERS PUMPED BY PHOTOIONIZATION

It is shown that a steady state inversion on hydrogenic states can be obtained if a fully ionized plasma is subjected to the appropriate kind of radiation. Two well defined cases are numerically investigated : 1. narrow band pumping radiation, 2. black body pumping radiation. Special emphasis is given to the question if radiative cooling of the plasma is sufficient to prevent a temperature increase of the electron gas which would destroy the inversion

Generalized Linford formula and its application to Traveling Wave Excitation

The Linford formula for the intensity output from a medium undergoing Amplified Spontaneous Emission (ASE) is generalized to the case when the gain coefficient is position dependent. The most evident application of this theory relates to the frequently encountered situation that the pump intensity and therefore the gain coefficient vary along the line-focus. A second application arises in Traveling Wave Excitation (TWE) ASE lasers if the excitation velocity and the group velocity of the amplified pulse are not the same. Using the new formula an explanation of the early roll-off in the emitted intensity of Transient Collisional Excitation (TCE) x-ray lasers is given and the design of a more effective TWE set-up is put forwar

Photopumping of innershell transitions by relativistic plasmas

A 130 fs 200 mJ titanium saphire laser is used to investigate conditions of generating inversion on an innershell transition in cobalt Using a longitudinal pumping geometry copper K-shell radiation is used to photopump cobalt [MATH]. The amount of photopumping is determined by comparing the generated cobalt radiation with the one of nickel, for which photopumping by copper [MATH] is not possible. Using a specially designed target with a vacuum gap in between the pump and the medium to be pumped we observe a photopumped fraction of over 90 %. The vacuum gap holds back the electrons which generate L-holes and thus destroy the inversion

Generating inversion on a nuclear transition - photopumping of 103Rh

The natural isotope 103Rh has two low-lying levels with energies of 357.4 keV and 295.0 keV, the lifetimes of which are 107 and 9.7 ps, respectively. Thus the lower level has a considerably shorter lifetime than the upper one, a situation favorable for generating population inversion. Nuclear Resonance Fluorescence (NRF) experiments have been performed in which 26 high-lying levels have been identified, from which either the upper or the lower level or both can be populated by radiative decay. An evaluation of the data shows that this "feeding" mechanism indeed resulted in inversion on the 62.4 keV transition

High gain recombination XUV lasers and efficient XUV harmonics from ps laser pulse interactions with solid targets

We present recent developments on high gain recombination XUV lasers and efficient XUV harmonics from solid targets using the CPA Vulcan laser beam at the Rutherford Appleton Laboratory (RAL). Following successful experiments on the hydrogen-like carbon recombination laser at 18.2 nm, high gain operation has also been demonstrated at 11.1 nm in the sodium-like copper recombination XUV laser by irradiating thin fibre targets at intensities of 6x10(15) Wcm(-2) with 2 ps laser pulses. This experiment has shown that 2 ps is the optimum pulse duration to drive the sodium-like copper laser. In addition to the recombination laser experiments, highly efficient harmonics up to 75th order at 14.0 nm have been observed in the interaction of 2 ps laser pulses with solid targets for intensities up to 10(19) Wcm(-2). The conversion efficiency is estimated to be greater than or equal to 10(-6) at 10(19) Wcm(-2) for harmonic orders up to the 68th

Robust, low-bandwidth, multi-vehicle mapping

This paper addresses the problem of decentralised simultaneous localisation and map building for a team of agents where the communication bandwidth is limited. We present an extension to current approaches that enables multiple vehicles to acquire a joint map, but which can cope with communication bandwidth limitations. Nettleton's approach uses a hybrid information filter/Covariance Intersection algorithm on each communication link to manage the inter-vehicle communication and ensure that information vehicles share does not get 'double counted'. The Covariance Intersection algorithm is a highly conservative method for managing double counting and its use can produce highly uncertain maps. We introduce a novel and more efficient tool, called Bounded Covariance Inflation, for managing the double counting (or rumour propagation) problem. We show that the parameters required by the new approach can be determined locally by each vehicle and therefore the decentralised nature of the network is not compromised. We provide experimental results that illustrate the effectiveness of our approach in comparison with the original approach of Nettleton et al. © 2005 IEEE