Air Cherenkov Telescope Arrays!

Transcription

1 Air Cherenkov Telescope Arrays! " " " " " " " "as SII receivers! Imaging Air Cherenkov Telescope (IACT) arrays are appealing for Intensity Interferometry because of the large number of simultaneous baselines between large light collectors they might offer. I will present the sensitivity possibilities, constraints and limitations associated with the utilization of IACT for Stellar Intensity Interferometry.! Stephan LeBohec, University of Utah! SIIWG Workshop, SLC, Friday January 30 th 2009!

2 1963 J.E. Grindlay, 1975! uses the Narrabri telescopes! to observe Cen A in gamma TeV energies! we could start using! TeV gamma ray telescopes! as Intensity Interferometer receivers!

3 NSII:! Two telescopes! " " "on circular tracks! * No signal delays! * Range of baselines (10m - 200m)!

4 HESS 12m telescope array (Namibia)! VERITAS 12m telescope array (Arizona)!

5 VERITAS as an interferometer!

6 A possible design for CTA! Cherenkov Telescope Array! 4656 baselines! 47 baseline lengths! 600m 2 100m 2 Construction: 2012!

7 CHARA! Imaging the surface of Altair! J.D. Monnier, et al., 2007,! " " "Science, 317, 342.!

8 See Paul Nunez phase and image reconstruction! CTA! SII! imaging! capabilities!

9 SII receiver! convertion! of IACTs! (Interferometric observation! during full moon)! Camera! shutter! integration!

10 Geometrical optics digression! 12m f/1 Davis-Cotton! " " " " "0.05 o PSF = 10mm! 10nm OBW = Collimation to ~5 o! " " "f/1 Collimator ø=10mm/tan(5)=110mm! 5 o collimation! 110mm concentrator! 110mm analyzer! 110mm collimator! From f/1! Davis-Cotton!

11 Parabolic optics preserves timing! Camera!

12 Davis-Cotton optics used for IACT! "in order to minimize PSF degradation toward the edge of the fov! Camera! 12m Davis-Cotton f/1 = 4ns dispersion! " " " " "~100MHz signal bandwidth limitation!

13 Sensitivity?! A=100m 2! α=30%! Δf=100MHz! T=5 hours! S/N=5! For γ 2 =0.5! n ~ 5.5m V Δr=14%! 3.7m V, Δr=3%! This is with just one baseline!!!!

14 With many baselines...! PSF! limitation:! 0.05 o -> 9.6m V! 0.01 o -> 13.0m V!

15 So there is an interesting potential...! " " " "Now what?! Implementing SII with IACT arrays! Two types of considerations! " "1) "SII specific technology! " "2)IACT facility interfacing and adaptation!

16 1) SII specific technology! "* Optics! "* Photo-detectors! " "see David Kieda s presentation! "* Signal transmission! " "see Michael Daniel s presentation! "* Correlation! " "see presentations by! " " "Erez, Dainis, Giampiero, Stephan,! IT SEEMS WE VE GOT EVERY THING ALREADy!

17 2) IACT facility interfacing adaptation! "* Focal plane implementation! " "camera shutter = space and freedom! " " "CTA in need of specifications! " " " "(volume, weight, power, )! "* Parabolic instead of Davis Cotton! "- Not likely to happen (larger f/d & cost)! "- from 100MHz to 1GHz SN x 10 = 1.2m v! "- 1GHz implies 100ps timing!

18 2) IACT facility interfacing adaptation! * Should redundancy be reduced?! "% Analysis (higher order or not)! "% Science (low order imaging or imaging)?! NORTH! SKA! SOUTH!

19 2) IACT facility interfacing adaptation! "* Add a couple of telescopes! " " " " " " "for shorter baselines?! " " "Should they be smaller so as to! " " " " " " "not resolve bright stars?! Aliasing!

20 2) IACT facility interfacing adaptation! "* Real estate issues! " " "- Conduits! " " "- Building (correlator location,! " " " " " " " "control room, )! " " "- Observation programming! " " "- Observing modes! " " " " " "!

21 Conclusions!! "* SII with IACT: real science potential! " " "Bright moon time " " "IACT science output increased! " " "Synergy Optical % High Energy! "* Technology already available! " " "Choices to be made! " " "Several ongoing prototyping! "* CTA is going to happen! " " "Construction starting 2012! " " "Now is the time to get involved!

22 Hardware budget:! " "A shot in the dark:! "Secondary optics= $5,000 x 97! "Photo-detector = $2,000 x 97! "Signal transfer = $1,500 x 97! "Correlators = $200 x 4656! "Computing " = $20,000! "TOTAL =$1,775,700! " " " " "Say $2M!