Future Imaging Atmospheric Cherenkov Telescopes:

1. Future Imaging Atmospheric Cherenkov Telescopes: Performance of Possible Array Configurations for g-photons in the GeV-TeV Range S. Sajjad, A. Falvard and G. Vasileiadis LPTA, Université Montpellier 2, CNRS/IN2P3, Montpellier, France ICRC’07- Merida

2. Choices and assumptions • Focus on gamma shower simulation and reconstruction: Source, shower core, energy and effective area • gamma-hadron identification issues have not been touched • Parabolic mirrors • In order to focus on the issues concerning the showers themselves, we have ignored: • geomagnetic field • night sky background • image cleaning

3. The Tools: • Package developed for • Simulating the response of IACT arrays to atmospheric showers • Reconstructing the various shower parameters  will be made public

4. The Tools: Simulation Shower simulation done through CORSIKA (version 6.020 currently used - will be updated)

5. The Tools: Simulation Shower simulation done through CORSIKA (version 6.020 currently used will be updated) • Telescope simulation • Uses CORSIKA output

6. The Tools: Simulation Shower simulation done through CORSIKA (version 6.020 currently used will be updated) • Telescope simulation • Uses CORSIKA output • Reflection of Cherenkov photon by a parabolic mirror onto camera plane

7. The Tools: Simulation Shower simulation done through CORSIKA (version 6.020 currently used will be updated) • Telescope simulation • Uses CORSIKA output • Reflection of Cherenkov photon by a mirror onto camera plane • Variable diametre, focal length, camera size, pixel size, camera position

8. The Tools: Simulation Shower simulation done through CORSIKA (version 6.020 currently used will be updated) • Telescope simulation • Uses CORSIKA output • Reflection of Cherenkov photon by a mirror onto camera plane • Variable diametre, focal length, camera size, pixel size, camera position • Position and orientation of individual telescopes

9. The Tools: Simulation Shower simulation done through CORSIKA (version 6.020 currently used will be updated) • Telescope simulation • Uses CORSIKA output • Reflection of Cherenkov photon by a mirror onto camera plane • Variable diametre, focal length, camera size, pixel size, camera position • Position and orientation of individual telescopes • Array simulation (simulate up to 100 telescopes)

10. The Tools: Shower reconstruction source position • Source reconstruction Superposed images from all tels in the camera frame of ref.: • The axes from all images should meet at one point: the source • Each axis should pass from the centroid of corresponding image • The distance of the pixels from the corresponding axis should be minimum • The transverse profile of images is considered to be Gaussian

11. The Tools: Shower reconstruction source position • Source reconstruction Superposed images from all tels in the camera frame of ref.: • The axes from all images should meet at one point: the source • Each axis should pass from the centroid of corresponding image • The distance of the pixels from the corresponding axis should be minimum • The transverse profile of images is considered to be Gaussian Likelihood function

12. The Tools: Shower reconstruction -ln(Lall) map source position • Source reconstruction Superposed images from all tels in the camera frame of ref.: • The axes from all images should meet at one point: the source • Each axis should pass from the centroid of corresponding image • The distance of the pixels from the corresponding axis should be minimum • The transverse profile of images is considered to be Gaussian Likelihood function

13. The Tools: Shower reconstruction -ln(Lall) map source position • Source reconstruction Superposed images from all tels in the camera frame of ref.: • The axes from all images should meet at one point: the source • Each axis should pass from the centroid of corresponding image • The distance of the pixels from the corresponding axis should be minimum • The transverse profile of images is considered to be Gaussian Likelihood function

14. -ln(Lall) map N2 d2 d3 N1 d1 core position d4 N3 The Tools: Shower reconstruction • Shower core reconstruction • Same principle as for source reconstruction • Calculations in the ground frame of reference

15. -ln(Lall) map N2 d2 d3 N1 d1 core position d4 N3 The Tools: Shower reconstruction • Shower core reconstruction • Same principle as for source reconstruction • Calculations in the ground frame of reference N4 • Energy reconstruction • Uses the linear relationship between shower energy and the average number of photo-electrons in the image

16. Energy domains and choices for telescopes • The observational issues and physics goals depend on the energy domain • Different parts of the arrays could be optimised for observations in different energy domains

17. Energy domains and choices for telescopes • The observational issues and physics goals depend on the energy domain • Different parts of the arrays could be optimised for observations in different energy domains • ~300 GeV to a few tens of TeV • Domain where IACT show best performance • Good reconstruction and gamma-hadron discrimination with10-15m diam. telescopes • Need to improve sensitivity • Large number of medium sized tels over a large surface  12.5 m telescopes

18. Energy domains and choices for telescopes • The observational issues and physics goals depend on the energy domain • Different parts of the arrays could be optimised for observations in different energy domains • ~Below 300 GeV • Showers are smaller, more fluctuations, poorer reconstruction and gamma-hadron separation • Fluxes from sources tend to be higher • Need to collect more Cherenkov light from showers • A few telescopes with large diam. telescopes  30 m telescopes

19. Selection of array parameters Optimum telescope separation studied in terms of shower reconstruction Square unit of 4 telescopes preliminary Trigger: at least two telescopes with 50 p. e.

20. Selection of array parameters 400 m 1200 m Optimum telescope separation studied in terms of shower reconstruction preliminary Trigger: at least two telescopes with 50 p. e.

21. Selection of array parameters 400 m 1200 m Optimum telescope separation studied in terms of shower reconstruction preliminary Trigger: at least two telescopes with 50 p. e.

22. 30 m diam. 4 tels 200 m For 1800 m a. s. l. Optimum for 50 GeV(tel. diam. 30m) ~200m

23. 420 m 140 m 100 m 30 m diam. 4 tels 400 m 12.5 m diam. 33 tels For 1800 m a. s. l. Optimum for 300 GeV(tel. diam. 12.5m) ~140m Optimum for 50 GeV(tel. diam. 30m) ~200m

24. 420 m 140 m 100 m 30 m diam. 30 m diam. 5 tels 4 tels 400 m 12.5 m diam. 12.5 m diam. 49 tels 33 tels Two telescope configurations

25. 360 m 120 m 30 m diam. 30 m diam. 5 tels 4 tels 87 m 350 m 12.5 m diam. 12.5 m diam. 49 tels 33 tels At 3600 m  System rescaled Two telescope configurations

26. X103 Results Effective area 1800 m Typical effective areas of 4 tel systems: 0.4-0.5 X106 m2

27. Results Four telescope array (FTA) diam=12.5m Source reconstruction precision Large arrays (LA) Reconstruction done for cores within an 800X800 m2 region (after trigger)

28. Core reconstruction precision Results Typical precision on shower core for 1 TeV for a 4 tel array Reconstruction done for cores within an 800X800 m2 region (after trigger)

29. Results Energy resolution Typical precision on shower core for 1 TeV for a 4 tel array

30. Summary • A public package capable of simulating IACT system response to atmospheric showers and reconstructing gamma-ray parameters has been realised. • It was used to study the effect of telescope separation on various reconstruction parameters. • Two arrays with 37 and 54 telescopes have been studied at 1800 m and 3600 m for gamma parameter reconstruction and show considerable improvement with respect to the current generation.