1. 05/02/031 Next Generation Ground- based  -ray Telescopes Frank Krennrich April, 30 2001

2. 05/02/031 Outline - Scientific objectives - Technique - Design considerations - Solar arrays - Large single imaging telescope - Arrays of imaging telescopes - Summary

3. 05/02/031 Early 1990s 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 [GeV] 10 -2 10 -3 EGRET Whipple Compton, Pair conversion (Satellite) Atmospheric Cherenkov (Ground)

4. 05/02/031 Early 1995 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 [GeV] 10 -2 10 -3 EGRET Whipple, CAT, HEGRA Pair conversion (Satellite) Atmospheric Cherenkov (Ground)

5. 05/02/031 2005 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 [GeV] 10 -2 10 -3 GLAST STACEE, CELESTE MAGIC VERITAS, HESS, CANGAROO III Chandra Integral

6. 05/02/031 Design Goals of New Atmospheric Cherenkov Telescopes - Large effective area ~ 0.1 km 2 (10 5 GLAST) - Low energy threshold ~ 10 GeV – 50 GeV - Better flux sensitivity ~ 5 mCrab (50 hours) - Energy resolution  E/E ~ 10% - 15% - Angular resolution  ~ 0.02 o – 0.1 o - Wide energy range ~ 10 GeV – 100 TeV - Large Field of View ~ 3 o – 10 o (1/80 GLAST)

7. 05/02/031 Scientific Objectives Active Galactic Nuclei Supernova Remnants Infrared Background (Diffuse) Galactic Plane Gamma Ray Bursts Neutralino Annihilation, Primordial Black Holes, Quantum Gravity, … Pulsars   e + + e -

8. 05/02/031 Existing telescopes Whipple * Arizona, USA 10 m 489 250 1984 Crimea Crimea, Ukraine 6 x 2.4 m 6 x 37 1000 1985 SHALON Tien Shen, Russia 4 m 244 1000 1994 CANGAROO Woomera, Aust. 3.8 m 256 500 1994 HEGRA * La Palma, Sp. 5 x 3 m 5 x 271 500 1994 CAT * Pyrenees, Fr. 4 m 600 250 1996 Durham/Mk6 Narrabri/Aust. 3 x 7 m 1 x 109 250 1996 TACTIC Mt. Abu, India 4 x 3.5 m 1 x 225 300 1997 Seven TA Utah, USA 7 x 2 m 2 x 256 500 1998 * Significance (1Crab) > 5  x  t/hours  1/2 Solar-2 Barstow, USA 32x 7m 32 x 1 ?? 2000 GRAAL Almeria, Spain 63 x 7m 4 200 1999 Group/ Location Reflectors Camera Threshold Epoch Instrument Number x Aperture Pixels (GeV) Beginning STACEE Sandia, New Mexico 32(64) x 7m 32(64) x 1 180(50) 1998 CELESTE Pyrenees, Fr. 40 x 7m 40 x 1 50 2000

9. 05/02/031 Future telescopes VERITAS MAGIC STACEE CELESTE CangarooIII HESS GRAAL

10. 05/02/031 Imaging Atmospheric Cherenkov Telescopes Imaging Camera Area ~ 100,000 m 2 (10 5 x GLAST) E ~ 0.2 – 100 TeV  ~ 0.2 o 0.01 – 100 TeV

11. 05/02/031  -ray images: - narrow, short, smooth Hadronic images: - broad, long - local muons, patchy hadron rejection: 99.7% (10 -3 )  -ray proton Cosmic Ray Rejection Technique Crab Nebula 7  in 1hour

12. 05/02/031 Design: Energy Threshold - Night Sky Background : NSB = 2 – 4 x 10 12 photons/sr/m 2 /s  ~ 1.3 photons/m 2 (5ns, 0.5 o aperture) - Signal from  -ray shower: S ~ 0.1 [E /GeV] photons/m 2  ~ 5 photons/m 2 (50 GeV)  Signal/Noise ~ S/NSB 1/2  E ~ A -1/2  mirrorthreshold

13. 05/02/031 Design: Energy Threshold E ~ (NSB  A) 1/2 threshold dark site solid angle  pixel size electronics & optics QE efficiency

14. 05/02/031 General Strategies - increase mirror area: 250 GeV  50 GeV 10m - reduce optical losses:  f/number, light concentrators, mirrors  photodetectors QE (future): 25%  50% … 80% - reduce NSB:  improve telescope resolution  reduce pixel size in IACTs: 0.25 o  0.10 o  fast electronics: 20 ns  5 - 10 ns 50m

15. 05/02/031 General Strategies - increase mirror area: 250 GeV  50 GeV 10m - reduce optical losses:  f/number, light concentrators, mirrors  photodetectors QE (future): 25%  50% … 80% - reduce NSB:  improve telescope resolution  reduce pixel size in IACTs: 0.25 o  0.10 o  fast electronics: 20 ns  5 - 10 ns 50m

16. 05/02/031 Solar Arrays heliostats reflect light onto secondary optics (tower) wavefront sampling (light density profile) rejection of hadrons in trigger mirror area ~ 1200 - 2000 m 2 energy threshold ~ 50 GeV Significance (1Crab) ~ 1.0 – 1.6  x  t/hours  1/2

17. 05/02/031 Solar Arrays Base Ecole Polytechnique MPI, Munich UC, Riverside UCLA Location Pyrenees, Fr. Almeria, Spain Barstow, CA Sandia, NM # of heliostats 40 (54) 63 32 32(48) Mirror area 2160 m 2 2520 m 2 1200 m 2 1200 (1800) m 2 Pixels 40 4 32 32(48) Energy threshold 50 GeV 100 GeV ? 190 GeV (50 GeV) Parameter CELESTE GRAAL Solar-1 STACEE

18. 05/02/031 Single Large Imaging Telescope - parabolic reflector ~ 236 m 2 - focal length ~ 17 m - carbon fiber space frame - diamond-milled aluminum mirrors - swift slew speed 3 o /s - 800 pixels: ~ 0.1 o - fast electronics  5 ns trigger, FADCs - future (high QE detectors 45%) - E ~ 30 GeV MAGIC threshold - First light 2002

19. 05/02/031 Arrays of Imaging Telescopes I - 50 GeV – 50 TeV -  ~ 0.03 o @1TeV ~ 0.09 o @100GeV - Flux sensitivity: 15 mCrab @100GeV 5 mCrab @300GeV 80 m VERITAS

20. 05/02/031 Arrays of Imaging Telescopes I - 50 GeV – 50 TeV -  ~ 0.03 o @1TeV ~ 0.09 o @100GeV - Flux sensitivity: 15 mCrab @100GeV 5 mCrab @300GeV 80 m VERITAS

21. 05/02/031 Arrays of Imaging Telescopes II Stereoscopic detection: - reduction of energy threshold - improved angular resolution  - rejection of local muons  - shower core reconstruction  - analysis of faint images

22. 05/02/031 Arrays of Imaging Telescopes III - Science topics with NGGGRT

23. 05/02/031 HESS - 4 x Davis-Cotton ~ 120 m 2 - focal length ~ 15 m - steel space frame - ground-glas mirrors - 960 pixels: ~ 0.16 o - distance 120 m First light 2002

24. 05/02/031 CANGAROO III - 4 x parabola ~ 80 m 2 - focal length ~ 8 m - composite mirrors - 552 pixels - distance 100 m First light 2004

25. 05/02/031 VERITAS - 7x Davis-Cotton ~ 100 m 2 - focal length ~ 12 m - steel structure - ground-glas mirrors - 499 pixels: ~ 0.15 o - distance 80 m - 300 MHz FADC - Sub-arrays - mirror covers First light 2003/2005?

26. 05/02/031 VERITAS

27. 05/02/031 Overview of Future Telescopes Parameter MAGIC HESS CANGAROO-III VERITAS Base MPI, Munich MPI, Heidelberg Tokyo, Japan SAO, Arizona Location La Palma Namibia Woomera, Australia Arizona # of telescopes 1 4(16) 4 7 Mirror area/tel. 236 m 2 120 m 2 80 m 2 100 m 2 Elevation 2.3 km 1.8 km S.L. 1.3 km Energy threshold 30 GeV 40 GeV 100 GeV 50 GeV # of pixels 800 960 x 4 552 x 4 499 x 7 Sub-arrays First light 2002 2002 2004 2003/2005?

28. 05/02/031 Point Source Sensitivity

29. 05/02/031 Sensitivity of Telescope Arrays

30. 05/02/031 CELESTE: Crab at 50 GeV de Naurois et al., Proceed. of Gamma Ray Astrophysics workshop, in press (Heidelberg)

31. 05/02/031 Sensitivity to flares 5 mCrab (50 h) 20 x Whipple  second time scale for flares  Good match with X-ray satellites hypothetical lightcurve

32. 05/02/031 Status of Projects? Very Energetic Radiation Imaging Telescope Array System (VERITAS) Astronomy & Astrophysics in the New Millenium NRC 10-year Report