1. Status of the H.E.S.S. Experiment and First Results Paula Chadwick University of Durham, U.K. for the H.E.S.S. Collaboration

2. Ground-based  -ray Telescopes Detect gamma rays via the Cherenkov light produced by secondary showers – most usually in the atmosphere. Imaging atmospheric Cherenkov telescopes have: Large effective area Excellent background rejection Good source location

3. The H.E.S.S. Collaboration MPIK, Heidelberg Humboldt Universität, Berlin Ruhr- Universität, Bochum Universität Hamburg Landessternwarte Heidelberg Universität Kiel Ecole Polytechnique, Palaiseau LPHNE, Universités Paris VI-VII PCC Collège de France, Paris Université de Grenoble CERS Toulouse CEA Saclay Observatoire de Paris-Meudon University of Durham Dublin Institute for Advanced Studies Charles University, Prague Yerevan Physics Institute University of Namibia University of Potchefstroom

4. H.E.S.S. Location H.E.S.S

5. Vital Statistics 4 telescopes in Phase 1 Arranged on a square of side 120m Diameter 12m, area 108 m 2 382 mirrors Focal length 15m 960-pixel camera Total telescope weight around 60 tonnes

6. Measured spot width 0.02º for angles between 0 and 45º. Mirrors Quartz-coated aluminized glass, reflectivity > 80%

7. The Cameras 960 photon detector elements, each subtending 0.16 o angle, using 29 mm, Photonis 8-stage PMTs with borosilicate windows, equipped with Winston cones to improve light collection.

8. The final result weighs about 800 kg, is 1.6 m in diameter and 1.5 m in length. Close to 5kW of heat is dissipated by 80 computer- controlled fans.

9. Telescope monitoring Telescope pointing is monitored by CCDs LEDs in the camera lid simulate events A laser/LED system flat- fields the camera

10. Information from the CCD cameras allows the pointing to be corrected to give a resolution of 2.5 arcsec. Calculations courtesy of Stefan Gillessen

11. Atmospheric Monitoring Comprehensive monitoring with IR detectors on each telescope, scanning IR detector, LIDAR and of course a weather station on site.

12. The ROTSE 3C First light June 18 2003. Designed for GRB location; some time available to H.E.S.S.

13. Telescope no. 3 has all mirrors installed and aligned

14. The 1 st 2 telescopes are fully operational

16. First Results: The Crab Nebula 4.65 hours of on-source observations, z.a. range 45-50º, one telescope only. 20.1σ, 3.6 gammas/min See Masterson’s paper at the ICRC

17. First Results: PKS2155-304 July 2002: 2.2 hours, 9.9σ, 3.1 gammas/min Oct 2002: 4.7 hours, 6.6σ, 1.2 gammas/min See Djannati-Ataï’s paper at the ICRC.

18. To Conclude…. The first two H.E.S.S. telescopes are fully operational The third telescope has mirrors fitted and aligned Phase 1 completion early 2004 The Crab Nebula and PKS2155-304 have been detected with the 1 st telescope alone Routine observations are under way