1. Jamie Holder School of Physics and Astronomy, University of Leeds, U.K Increasing the Collection Area for IACTs at High Energies Future of Gamma Ray Astronomy Workshop, Mays Landing, October 2005

2. Introduction Power of Cherenkov technique is in large collection area Crab Flux (assuming A=2×10 5 m 2  eff =50%) – >1TeV: 2×10 -7 photons m -2 s -1 ; 1 photon/minute – >10TeV: 6×10 -9 photons m -2 s -1 ; 1.5 photons/hour – New galactic sources are ~few % Crab 3 methods to increase collection area – Large Zenith Angle observations Increases light pool size by viewing distant showers – Wide field-of-view Exploits bright tail of light pool at high energies – Large Arrays Collection area defined by array size, not light pool.

3. Wide field-of-view: de la Calle & Biller Light yield Displacement Elongation

4. Wide field-of-view: de la Calle & Biller Displacement 400m = 4° 10TeV at 400m = 1TeV at 100m Light yield Elongation Displacement

5. Wide field-of-view: de la Calle & Biller 10° Field-of-view Davies-Cotton F/1.0 10m Diameter 2300m a.s.l. 935 PMTs 0.3° spacing

6. Wide field-of-view: de la Calle & Biller Background rate~3KHz Cut efficiency (including T s ) ’s 75% CRs 99.8% Energy Resolution ~25%

7. Large Array Collection area defined by number and spacing of telescopes Brute force, Expensive option? but consider what you DON’T need above ~500GeV – R&D – Challenging Mechanics – High Altitude – Many, High QE pixels – Super-fast signal paths (fibre optics / camera-based electronics) – Topological trigger – Array trigger – FADCs – High speed/throughput DACQ – New analysis techniques

8. Large Array: Telescope Cost 127 PMT camera (0.25° spacing, FoV 3.25°) – DACQ=1 Linux PC ~$1000-$2000 – 127 ADC channels ?? $5000 ?? – 127 discriminator channels ?? $3000 ?? – HV supply, cables, ?? $10000 ?? – 127 1” PMTs + bases @$300-$500 each – Sub-Total = $57,000 – $83,500 6m diameter reflector = 28m 2 – VERITAS (Glass~10 Kg/0.4m 2 ) $1000/0.4m 2 – Durham (Al ~6Kg/0.8m 2 ) ?? £150/1.75m 2 – Sub-total = $10,000 - $70,000 Mount – Allen Telescope Array = 350, 6m diameter radio telescopes for SETI – Currently 30 installed, completion in 2006 – Sub-total = $30,000 Total: $150,000 – $250,000 not impossible

9. Large Array: ATA

11. Large Array 5×5 array ~ $5M Hardware, $7M Total? 200m spacing 1km 2 physical area >1.5km 2 effective collection area Valid for ALL energies>500GeV Complementary to a low energy array Predictable performance Guaranteed Discrimination Flexible (12 stereo pairs) Extendable

12. High Energy: Justification Only worthwhile if there are many extended sources with hard spectra…

13. High Energy: Hard spectra 17 Galactic sources – Hard spectra, no cut- off – Explore hadronic emission region 3 New AGN at z>0.15 Explore high energy, short timescale emission – AGN, X-ray Binaries, GRBs?

14. High Energy: Angular resolution

15. Large Array: Future Work Simulations (spacing, camera size) Serious Cost Estimate Acronym: G amma R ay A stronomical T elescope I maging S ystem