In this paper we investigate the possibility that there is a first phase of partial ionisation due to X-rays produced by black hole accretion in small-mass galaxies at redshifts 7 < z < 20. This is followed by complete reionisation by stellar sources at z ≃ 7. This scenario is motivated by the large optical depth to Thompson scattering, τe ≃ 0.17 ± 0.04, recently measured by WMAP. But it is als...

We use numerical simulations of a cosmological volume to study the X-ray ionisation and heating of the intergalactic medium by an early population of accreting black holes. By considering theoretical limits on the accretion rate and observational constraints from the X-ray background and faint X-ray source counts, we find that the maximum value of the optical depth to Thompson scattering that c...

In an x-ray preionised XeF(B~X) dischargeexcited laser driven by a magnetic-spiker sustainer circuit with a magnetic pulse compressor the influence of the various parameters on the optical pulse duration was experimentally investigated. Laser pulses at 2= 351 nm with a duration of 212 ns (FWHM) have been achieved in a NF3/Xe/Ne mixture by using very low (0.25 mbar) NF3 partial pressures in a to...

The charge mode is a new mode to excite a discharge XeC1 laser based on the dynamics of a spikersustainer circuit with a magnetic pulse compressor. The breakdown voltage is higher than in any other mode, due to a very fast rise time. The higher breakdown voltage provides a wider discharge and we found that more energy can be deposited before discharge instabilities terminate the optical output....