Jamie Holder School of Physics and Astronomy, University of Leeds, U.K

1. Increasing the Collection Area for IACTs at High Energies Jamie Holder School of Physics and Astronomy, University of Leeds, U.K 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=2×105 m2 eff=50%) • >1TeV: 2×10-7 photonsm-2 s-1 ; 1 photon/minute • >10TeV: 6×10-9 photonsm-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. Displacement Wide field-of-view: de la Calle & Biller Light yield Elongation

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

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 Ts) • ’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 = 28m2 • VERITAS (Glass~10 Kg/0.4m2) $1000/0.4m2 • Durham (Al ~6Kg/0.8m2) ?? £150/1.75m2 • 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

10. Large Array: ATA

11. Large Array • 5×5 array ~ $5M Hardware, $7M Total? • 200m spacing • 1km2 physical area • >1.5km2 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: Gamma Ray Astronomical Telescope Imaging System