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Concept idea for a future telescope array observatory

Concept idea for a future telescope array observatory. CTA meeting Berlin May 4-5, 2006 Thomas Schweizer. Goals and constraints. Specification of CTA observatory Energy range 10 GeV to 100 TeV Available budget: 100-150 Mio Euro Sensitivity ~ 5-10 times better than previous instruments

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Concept idea for a future telescope array observatory

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  1. Concept idea for a future telescope arrayobservatory CTA meeting Berlin May 4-5, 2006 Thomas Schweizer May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  2. Goals and constraints • Specification of CTA observatory • Energy range 10 GeV to 100 TeV • Available budget: 100-150 Mio Euro • Sensitivity ~ 5-10 times better than previous instruments • It is impossible to span 7 orders of magnitude (10 GeV - 100 TeV)by one single detector and keep optimal performance (because of limited dynamic range and steep spectra) • One array 10 GeV to 1 TeV (LEA) • low energy threshold, ~10-20 large telescopes • 75 % of budget (North and South) • One array 1 TeV up to 100 TeV (ULTRA II) • very large effective area, ~100-150 small telescopes • 25 % of budget (only South) • E. Lorentz talk May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  3. Two arrays together • Overlap in energy between both arrays for cross-calibration- Simultanous observation with small and large array- Parallel observation of several sources with parts of array- Longterm monitoring of sources with single telescopes Lowest possible energy threshold and highest sensitivity 1-2 km2, large eff. area May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  4. Low energy array (LEA) • What do we want for available budget (~70 Mio Euro) ? • As many telescopes as possible for high sensitivity and parallel observation of sources • As low energy threshold as possible • Possibilities: • 30 m telescopes (710 m2 mirror) with classical PMTs • 23 m telescope (415 m2 mirror) with SiPM light sensors • 23 m telescope • Increase in photon-detection efficiency rather than mirror area high mirror reflectivity (90%), high QE (SiPM, 50%) • Smallertelescopes and lighter telescopes are cheaper, < 120 tons weight, 70 tons possible • Big question: is it possible to build 16-20 telscopesfor 70 Mio Euros ? May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  5. Possible telescope parameters Active mirror control with improved optical quality (PSF) • FOV=5° • F/D = 1.2: • acceptable aberation (5° FOV) D= 23 m diameter parabolc mirror  430 m2 F= 28 m • Protection against • wind lift-up • Lighter & cheaper telescope May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  6. Possible parameters for camera design FOV 5° • D= 2.4 m • A=4.5 m2 • Roundish camera, FOV 5° • Square pixels • Assume QE=50 % flat from 300-600 nm May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  7. Some numbers • Case study: square pixels with 4 SiPM chips à 1 cm x 1 cm • Light concentration 3.25 (with microlensing foil) • Light concentration 5 • Absolute maxim allowed dark rate for SiPM: 20% of NSB  Assume 100-200 kHz/1mm2 for future SiPM May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  8. Data volume generated by telescope system • Assume 2.5 GHz FADC (capacitor array) sampling • Assume 50 samples per pixel à 16 Bits  100 Bytes • Assume trigger rate of 2 kHz (at 10 GeV) • Assume 3000 Pixels • Assume 20 Telescopes • Assume an average of 8h observation time • About 10.5 Petabytes per month !! • Even with modern computers in 10 years this amountwill be a serious problem May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  9. Data reduction • Necessity for online data reduction • Online signal extraction from FADC slices Amplitude, Arrival time, Pulse width of largest pulse3 floats (can be reduced)  12 Bytes • Zero suppression  Low level image cleaningassume reduction factor 20 (maybe more ?) • Reduced data rate: 65 Terrabytes per month (Still a lot ! ) Comment: Data reduction (signal processing) maybe already inside camera May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  10. Readout ideas • All the readout electronics inside the camera reduces the cost of the camera (maximum weight 2 tons) • No heavy cabeling, simplified construction • Data reduction (signal processing) already inside the camera 1 Gbit Ethernet ? Switch Modules of 100 pixels 100 channeldomino sampling Signal processorto extract signalsand data reduction Collect data from all modules & ultrafast data transfer to DAQ May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  11. Cost estimates • The camera housing + mechanics + Cooling and temperaturestabilization + Light concentrators: 400 k€ • Price for 4 SiPM chips (one pixel): ~ 300 € (Hamamatsu) • Price for readout (Cap. array + signal processing) per channel: ~ 300 • Sum price/channel: ~600 € • Sum all pixels (2250): ~1.4 Mio € • Total: 1.8 Mio € • Maxim price for camera + readout: 2 Mio € • Price for telescope frame 2-3 Mio € • Price for one telescope: 4-5 Mio € • 70 Mio €/4-5 Mio €  14-17 telescopes May 4-5, 2006 T.Schweizer, CTA meeting Berlin

  12. Timing • First light within 5-6 years ? • SiPM chips probably available within 2 years • Use standard mechanics/electronics as much as possible • Time plan • Camera development with SiPM: 4 years • Development time for mechanics 2-3 years • Production and installation of 16 telescopes: 2-3 years • All together: 5 years until first telescope installed ? May 4-5, 2006 T.Schweizer, CTA meeting Berlin

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