1. C TA An advanced facility for ground-based high-energy gamma ray astronomy

2. Roadmaps European government science funding agencies formal relation not defined! Subdivisions concerned with astroparticles ApPEC Astroparticle Physics European Coordination Steering committee Peer review committee ~ 2000 ApPEC Roadmap ESFRI European large research infrastruct. ESFRI European large research infrastruct. Subcommittee for Astronomy and Astroparticles Subcommittee for Astronomy and Astroparticles ~2004 ESFRI Roadmap

3. C TA An advanced facility for ground-based high-energy gamma ray astronomy Roadmaps ApPEC (Astroparticle Physics European Coordination) Roadmap Draft circulated Three projects proposed for ESFRI roadmap KM3NET neutrino telescope CTA gamma ray telescope Gravitational wave observatory ESFRI (European Large Research Infrastructures) Roadmap Hearings by subcommittees Filtering by ESFRI committee (Funding agencies) First roadmap in fall 2006 Updated in regular intervals Will (very likely) include things such as KM3NET, FAIR, XFEL, …

4. C TA An advanced facility for ground-based high-energy gamma ray astronomy  Exploring the non-thermal universe  the C herenkov T elescope A rray as a facility for gamma ray astronomy in the next decade

5. C TA An advanced facility for ground-based high-energy gamma ray astronomy The Cherenkov Telescope Array facility aims to explore the sky in the 10 GeV to 100 TeV energy range builds on demonstrated technologies combines guaranteed science with significant discovery potential is a cornerstone towards a multi-messenger exploration of the nonthermal universe

6. C TA An advanced facility for ground-based high-energy gamma ray astronomy Unifying European efforts VERITAS MAGIC H.E.S.S. … and maintaining European lead CTA involves scientists from Czech Republic Germany France Italy Ireland UK Poland Spain Switzerland Armenia South Africa Namibia from several communities astronomy & astrophysics particle physics nuclear physics about 250-300 scientists working currently in the field will be directly involved, user community significantly larger

7. C TA An advanced facility for ground-based high-energy gamma ray astronomy CTA as a user facility Significant fraction of open time (~50%) Guaranteed time for CTA consortium (~50%) Probably local staff for basic operation, plus experts when needed Facilities to make data available to outside users Data public after certain time (~1 y) Significant fraction of operating funds / user support / data center support needs to come from external (EC?) sources

8. C TA An advanced facility for ground-based high-energy gamma ray astronomy The Science Case

9. C TA An advanced facility for ground-based high-energy gamma ray astronomy Science topics Dunkle Materie Pulsars and PWN GRBs SNRs AGNs Origin of cosmic rays Cosmology Dark matter Space-time & relativity

10. C TA An advanced facility for ground-based high-energy gamma ray astronomy The Milky Way at very high energies

11. C TA An advanced facility for ground-based high-energy gamma ray astronomy Color scale: TeV gamma rays Black contours: X-rays H.E.S.S. RXJ 1713.7-3946

12. C TA An advanced facility for ground-based high-energy gamma ray astronomy Supernovae & pulsars: Vela region Vela (Rosat) Vela Junior d ≈200 pc age ≈ 700 y

13. C TA An advanced facility for ground-based high-energy gamma ray astronomy Science potential Current instruments have passed the critical sensitivity threshold and reveal a rich panorama, but this is clearly only the tip of the iceberg Broad and diverse program ahead, combining guaranteed astrophysics with significant discovery potential Horan & Weekes 2003 Distance Pulsed emission Microquasars Molecular clouds Clusters of galaxies

14. C TA An advanced facility for ground-based high-energy gamma ray astronomy Science potential

15. C TA An advanced facility for ground-based high-energy gamma ray astronomy Physics working groups Where should we look ? What can we expect to see ? Why should we look i.e. what do we learn from the 100…1000 new sources ? How should the instrument be optimized ?

16. C TA An advanced facility for ground-based high-energy gamma ray astronomy Possible CTA sensitivity Crab 10% Crab 1% Crab GLAST MAGIC H.E.S.S. Current Simulations 20 wide-angle 10 m telescopes de la Calle Perez, Biller, astro-ph 0602284 30 m stereo telescopes Konopelko Astropart.Phys. 24 (2005) 191 E. F(>E) [TeV/cm 2 s] looks a bit optimistic looks a bit optimistic

17. C TA An advanced facility for ground-based high-energy gamma ray astronomy Extending the energy coverage hadron model electron model CTA 10 -13 10 -12 10 -11 10 -10 0,010,1110100 E 2 F(E) Energy [TeV] RXJ 1713-3946 (x 0.1) Vela X MSH 15-52 Cutoff region - crucial to understand acceleration mechanisms Transition region to GLAST Regime of pulsars, AGN,… Sensitive to acceleration mechanism

18. C TA An advanced facility for ground-based high-energy gamma ray astronomy CTA and GLAST EGRET sky GLAST sky Important for schedule: GLAST mission (2007 - 2012+) Provides all-sky monitor Simultaneous spectral coverage from ~2. 10 7 eV to few 10 14 eV

19. C TA An advanced facility for ground-based high-energy gamma ray astronomy Possible CTA sensitivity Crab 10% Crab 1% Crab GLAST MAGIC H.E.S.S. Current Simulations E. F(>E) [TeV/cm 2 s] High energy region will generate important physics but few new sources and few breath-taking discoveries Low energy region expect many new sources new physics regimes (pulsars,…) but still “modest” sensitivity technically challenging, poor angular, energy resolution Medium energy region highest sensitivity predictable performance “bread and butter”

20. C TA An advanced facility for ground-based high-energy gamma ray astronomy Possible CTA sensitivity Crab 10% Crab 1% Crab GLAST MAGIC H.E.S.S. Current Simulations E. F(>E) [TeV/cm 2 s] Performance not perfectly predictable MC should be reliable, if detailed enough; input physics and parameters are well known … Problem in my view (Gamma) signal to (CR) noise is much worse than in TeV range (1:few 10 – 1:few 100 vs 10:1 - 1:10) Not clear if background systematics can be reduced enough – currently stuck at few% level

21. C TA An advanced facility for ground-based high-energy gamma ray astronomy Possible CTA sensitivity Crab 10% Crab 1% Crab GLAST MAGIC H.E.S.S. Current Simulations E. F(>E) [TeV/cm 2 s] Need to achieve factor ~10 gain in sensitivity Aim for full energy range Cover entire energy range within a facility to maximize temporal overlap and minimize systematics Need to achieve factor ~10 gain in sensitivity Aim for full energy range Cover entire energy range within a facility to maximize temporal overlap and minimize systematics

22. C TA An advanced facility for ground-based high-energy gamma ray astronomy Camera field of view A full-sky survey with an instrument like H.E.S.S. is not very interesting H.E.S.S. did not find a single serendipidous source in extragalactic exposures (~35% of total H.E.S.S. time) For the Galaxy, survey mode is most efficient at H.E.S.S. sensitivity and beyond Is a full sky survey interesting @ 20 GeV and few % Crab sensitivity ? Don’t know (guess not) Is a full sky survey interesting @ 1 TeV and milli-Crab sensitivity? Don’t know (guess not) What can one realistically realize? milli-Crab over modest (few degr.) field

23. C TA An advanced facility for ground-based high-energy gamma ray astronomy Camera field of view: (a) Sky coverage 3o3o 5o5o 8o8o Effective field of view for given camera diameter

24. C TA An advanced facility for ground-based high-energy gamma ray astronomy Camera field of view: (a) Sky coverage 14 16 18 20 22 24 24681012 C = 50 C = 25 Cost per (Galactic) Source Diameter [Degr.] C = Dish cost in units of cost of camera per square degree for one-dimensional band of sources

25. C TA An advanced facility for ground-based high-energy gamma ray astronomy Camera field of view: (b) Energy coverage Current instruments: 3 o -5 o fov Larger fov desirable for high energy part of array Image centroids 100 m 2 telescope astro-ph/0602284 Efficiency 10 m 2 telescope J. Phys. G 26 (2000) 183

26. C TA An advanced facility for ground-based high-energy gamma ray astronomy Technology and Maturity

27. C TA An advanced facility for ground-based high-energy gamma ray astronomy few 1000 m High-energy section ~0.05% area coverage E th ~ 1-2 TeV 250 m Medium-energy section ~1% area coverage E th ~ 50-100 GeV 70 m Low-energy section ~10% area coverage E th ~ 10-20 GeV Array layout: 2-3 Zones FoV increasing to 8-10 degr. in outer sections

28. Not to scale ! Option: Mix of telescope types

29. Option: Single dish type Not to scale ! Requires further development of trigger system for central cluster, allowing to combine pixel signals from multiple telescopes Modes of operation Deep wide-band mode: all telescopes track the same source Survey mode: staggered fields of view survey sky Search & monitoring mode: subclusters track different sources Narrow-band mode: halo telescopes accumulate high-energy data, core telescopes hunt pulsars …

30. C TA An advanced facility for ground-based high-energy gamma ray astronomy Telescope structure Proven: H.E.S.S. 12 m dish Proven: MAGIC rapid-slewing 17 m dish Construction started: H.E.S.S. II 28 m dish 010 m20 m30 m Dish size Cost / Dish Area Camera cost dominates Dish cost dominates

31. C TA An advanced facility for ground-based high-energy gamma ray astronomy Telescope costs versus diameter … unless new camera technology is available … gated image intensifiers??

32. C TA An advanced facility for ground-based high-energy gamma ray astronomy Photon detector technology Conventional PMTs with improved cathodes, coatings GaAs photo cathodes Semiconductor single-photon detectors: photon counting with small pixels Improved photon detectors under development allow further improvements in sensitivity and threshold 3 x 3 mm 2 silicon PMT (MPP & MEPhI) 5 x 5 mm 2 silicon PMT (MPP & MEPhI) 2007: Back-illuminated pixel MPI-HLL,  ~ 70%

33. C TA An advanced facility for ground-based high-energy gamma ray astronomy Readout technology Several proven solutions Optimise further, decide on basis of cost, power consumption, performance GHz sampling analog memory ADC Trigger ~ 200 ns memory depth H.E.S.S. SAM ASIC Digital memory GHz FADC Trigger  s … ms memory depth MAGIC FADC/MUX SYSTEM

34. C TA An advanced facility for ground-based high-energy gamma ray astronomy Saclay SAM ASIC 2 GHz sampling freq. 256 memory cells Hi/low gain channel 11.5 bit dynamic range (single channel) Future versions: parallel DACs on-board FPGA on-board trigger comparator

35. C TA An advanced facility for ground-based high-energy gamma ray astronomy Camera field of view: Optics Optics for wide fov very large f/d mechanically non-trivial Dual-mirror optics with (large) secondary cost, alignment, large effective focal length? Frensnel corrector plate in front of camera cost, transmission 1 mrad 0.06 o 2 mrad 0.12 o J. Buckley

36. C TA An advanced facility for ground-based high-energy gamma ray astronomy Low-energy region Dish options 30 m dish with conventional PMTs can be built now; cost? 21 ± 4 m dish with semiconductor PMTs under R&D: when available? cost? 13 ± 3 m dish with FADC and digital intertelescope trigger R&D: trigger non-trivial small 3-5 m dish and digital intertelescope trigger (STAR) I don’t see how this could be cost-effective Other considerations Field of view: “small” (4-5 degr.) Pixel size: “small” (<0.1 degr.) to provide high angular resolution at higher energies

37. C TA An advanced facility for ground-based high-energy gamma ray astronomy Limiting angular resolution with lots of light 1 TeV H.E.S.S. (0.15 degr.)

38. C TA An advanced facility for ground-based high-energy gamma ray astronomy One option (?) High energy ~20 10-12 m dishes with 8-12 degr. fov, spread out 1.5 – 2 M€ each -> 30-40 M€ Medium energy ~15 15-18 m dishes with 7-10 degr. fov, loose cluster ~ 3 - 4 M€ each -> 45-60 M€ Low energy few 25-30 m dishes with 4-6 degr. fov, clustered ~ 10 M€ each -> 40 M€ Well beyond unitarity limit … combine functions ?

39. C TA An advanced facility for ground-based high-energy gamma ray astronomy Design criteria CTA will be a user facility (~50% open time) It will consist of a significant number of telescopes  Cost-effective design but even more important Efficient installation and commissioning High reliability, minimal maintenance Ease of operation and calibration

40. C TA An advanced facility for ground-based high-energy gamma ray astronomy Design criteria Cost seems unrealistic to assume that one will have more than 40-50 M€ for a first stage (before 2015, say) need to find design which optimizes physics output and represents a significant step beyond HESS II / MAGIC II Construction mode very likely, HEP-like model (splitting work over institute shops) is better (=cheaper) than ALMA like models (order system from industry) modest number of different components – sharing of work is nontrivial to organize but see examples: AUGER, LHC Silicon trackers, …

41. C TA An advanced facility for ground-based high-energy gamma ray astronomy Sites

42. C TA An advanced facility for ground-based high-energy gamma ray astronomy Ultimately aim for two sites covering the full sky South: Khomas Highland, Namibia, 23 o S, 1800 m North: Canary Islands, IAC sites 28 o N, 2000+ m Option: South-American High-altitude sites, 3500+ m Multiple sites would be designed, constructed and operated by a single consortium

43. Search Results – Near West Elevation Key >2500m >3000m >3500m >4000m >4500m >5000m Argentina Bolivia Peru Ecuador Colombia Chile Search SRTM preliminary data set for  Contiguous circular region  With radius 720m (9×80m / 1.6km 2 )  At elevation >2500m  Flat to 100m  Ignoring voids in data Search SRTM preliminary data set for  Contiguous circular region  With radius 720m (9×80m / 1.6km 2 )  At elevation >2500m  Flat to 100m  Ignoring voids in data from Stephen Fegan (UCLA)

44. C TA An advanced facility for ground-based high-energy gamma ray astronomy Clear (“photometric”?) nights from satellite survey (Erasmus)

45. C TA An advanced facility for ground-based high-energy gamma ray astronomy Sites - south New site might offer slightly better performance at low energy larger fraction of clear nights easier cooperation with US + Japanese groups, if desired New site might involve longer lead times higher infrastructure costs more difficult access Need to better understand options and balance

46. C TA An advanced facility for ground-based high-energy gamma ray astronomy Schedule

47. C TA An advanced facility for ground-based high-energy gamma ray astronomy (Very optimistic) Schedule 0607080910111213 Site exploration Array design Component prototypes Telescope prototypes Array construction Partial operation Full operation GLAST FP 7 Design Study “Letter of Intent” (100 pages, physics + conceptual design) Technical proposal

48. C TA An advanced facility for ground-based high-energy gamma ray astronomy Next steps Project will receive high priority in upcoming APPEC roadmap Strong support by MPG, CNRS,… Plan to apply for FP7 design study In parallel, continue site exploration simulations & design optimization technical developments tests with existing instruments funding discussion Next goals: conceptual & technical design

49. C TA An advanced facility for ground-based high-energy gamma ray astronomy Organisation Facility with mix (~50/50) of open and guaranteed time Public data (after grace period) Steering committee Scientific and techn. advisory committee Program committee Science tasks Technical tasks Core groups Associated scientists Users Project management General assembly Operation To be defined: organisational form / host organisation