Upcoming seminars: 2017
Friday, 24 March
Professor Jean-Paul Tavernet
LPNHE Paris, Sorbonne- Université Pierre et Marie Curie
The sky through the H.E.S.S. eyes: a ground-based gamma-ray astronomy experimentThe High Energy Stereoscopic System (H.E.S.S.) is an array of five Imaging Atmospheric Cherenkov Telescopes (IACTs) located in the Khomas Highland of Namibia. It is a powerful tool for investigating the non-thermal universe in the 50 GeV - 50 TeV range, the ground-based gamma-ray astronomy domain.
The array initially consisted of four 12 m telescopes, operating since 2004 as a single stereoscopic system. A decade of H.E.S.S. observations gives significant contributions to this exploring field, This includes the H.E.S.S. Galactic Plane Survey, which provided a systematic scan of the Galactic disk with an unprecedented sensibility, spectra and morphologies of Supernova Remnants, observations of fast variability in blazars, constraints on the Extragalactic Background Light, and other important results.
In 2012, a fifth telescope was added at the centre of the original array. This large telescope of 28 meters diameter improves the performance of the array, including a lowering of the energy threshold down to 50 GeV. Such an extension of the instrument's energy range is particularly useful for studies of transient phenomena and variable sources with soft spectra.
The description and the current status of H.E.S.S. experiment will be presented. An overview of some recent results will be discussed such as the H.E.S.S. II observations of the Vela pulsar or the Galactic Plane Survey. The future of the experiment and of the ground-based gamma-ray astronomy with the future Cerenkov Telescope Array observatory will be exposed.
Friday, 31 March
11:00 am – 12:00 pm Rutherford 531, Level 5
Associate Professor G. Mackay Salley, Erskine Visitor from Wofford College, South Carolina. Mackay is visiting with Roger Reeve's laser group from 13 February to 23 June 2017. Mackay is based in Room 614 Ext. 6532.
In this presentation I will share some experiences, successes and struggles, of teaching at a liberal arts college and staying active in a research field. In the second half of the presentation I will present the results of research involving a spectroscopic study of Co:ZnO. ZnO has attracted interest as transparent conducting window for solar energy conversion and doping is a means to extend its useful spectral range. Despite decades of investigation of Co:ZnO by optical spectroscopy and photoconductivity, the precise nature of the 4 A2→4 T1 manifold excitation that gave rise to conductivity was little understood. Variable-temperature photoconductivity measurements reveal a thermally assisted ionization process that enhances the d-d photoconductivity at higher temperatures as well as an additional temperature independent pathway.