Status of the Small-Sized Telescopes of the Cherenkov Telescope Array

Transcription

1 Status of the Small-Sized Telescopes of the Cherenkov Telescope Array Akira OKUMURA for the CTA Consortium (Thanks to the SST teams) Institute for Space-Earth Environmental Research, Nagoya University The extreme Universe viewed in very-high-energy gamma rays 2018 Oct 12, 2018 cherenkov telescope array

2 Small-Sized Telescopes (SSTs) cherenkov telescope array SST-1M SST-2M GCT SST-2M ASTRI 2

3 3 High-energy Frontier by CTA SSTs CTA Consortium arxiv: s -1 ) -2 x Flux Sensitivity (erg cm 2 E LAT Pass 8 (y, (l,b)=(0,0)) LAT Pass 8 (y, (l,b)=(120,45)) Differential flux sensitivity MAGIC 50 h HAWC 1 year HAWC 5 year H.E.S.S. 50 h MST LST SST Core Energy Band TeV VERITAS 50 h CTA North 50 h CTA South 50 h (prod3b-v1) Energy E (TeV) R 2

4 4 Baseline Layout of CTA with 70 SSTs CTA North CTA South LST MST SST 2.5 km Achieves a vast effective area of ~5 km 2 with 70 SSTs Extends the highest-energy frontier to 300 TeV and beyond

5 5 Southern Site Paranal, Chile Very Large Telescope Proposed Site (~2150 m a.s.l) E-ELT Image CNES/Airbus/DigitalGlobe/Google Earth

6 PeVatron: Galactic PeV Cosmic-ray Accelerator 2.6 E 2.6 s -1 E dn/de F(E) (GeV [GeV 1.6 m -2-2 s sr -1-1 sr ] -1 ) Grigorov JACEE MGU Tien-Shan Tibet07 Akeno CASA-MIA HEGRA Fly s Eye Kascade Grande 3 IceTop-73 HiRes 1 HiRes 2 Telescope Array Auger Knee Cosmic rays sr -1 ] s -1 m [GeV F(E) Knee 4 2nd Knee Grigorov JACEE PDG Kascade ~300 TeV gamma Kascade Grande E [ev] E [ev] E IceTop-73 E (ev) Figure 29.9: Expanded view Fi HiRes 1 of Figure 29.8: The all-particle Figure spectrum 29.8: as a The function all-particle of E spectrum as a function of E the cosmic-ray spectrum from da th HiRes 2 (energy-per-nucleus) Where do PeV cosmic from airrays shower Telescope (energy-per-nucleus) come Array measurements from? Do from [90 5]. PeVatrons air shower measurements accelerate and the Auger CRs [90 5]. up Observatory Knee? [5] an 2.6 E TeV in Kascade gammas by SSTs ~3 PeV 2 sr -1 ] s -1 m [GeV F(E) 2.6 E 3 2 Grigorov JACEE MGU Tien-Shan Tibet07 Akeno CASA-MIA HEGRA Fly s Eye 1 Auger MGU Tien-Shan Tibet07 Ankle Akeno Knee CASA-MIA HEGRA Fly s Eye Kascade Kascade Grande IceTop-73 HiRes 1 HiRes 2 Telescope Array Auger 2nd Knee Measurements ~3 PeV cosmic-ray of flux 1 with protons small Measurements air shower ~300 of experiments TeV fluxgamma with in small the rays airthrough shower experiments HiRes data π 0 decays in the [112] is consistent HiRe with knee region differ by as much knee as a region factor differ of two, by as indicative much as of a factor of two, indicative of E [ev] (UHECR) composition getting (UHE ligh systematic uncertainties in interpretation systematic uncertainties of the data. (For in interpretation a review of the data. (For a review and helium above 19 Figure ev, while and 29.9: 6A Knee 17 2nd Knee sr -1 ] s -1 m [GeV F(E) 2.6 Ankle E PeV proton Ankle ISM p/he Telescope Array π 0 Auger sr -1 ] s -1 m [GeV F(E) 2.6 E sr -1 ] s -1 m [GeV F(E) 2.6 E T A

7 7 CTA Key Science Projects for PeVatron Search

8 8 Galactic Center HESS 2016 HESS 11 E 2 flux (TeV cm 2 s 1 ) 12 CTA (Sim) 13 Diffuse emission ( ) Model (best fit): diffuse emission 68% Model: diffuse emission E cut,p = 2.9 PeV 90% Model: diffuse emission E cut,p = 0.6 PeV 95% Model: diffuse emission E cut,p = 0.4 PeV HESS J Energy, E (TeV) Figure 3 VHE -ray spectra of the diffuse emission and HESS Galactic center is the best PeVatron candidate so far (possible CR cutoff energy of a few PeV) Deep survey of ~800 hours is planned (inc. dark matter search)

9 Galactic Plane Survey (GPS) (Data) Galactic Center RX J

10 Galactic Plane Survey HAWC (> (Sim. 20 TeV 1635 Data) hrs) Galactic Center RX J1713 Any other PeVatron candidates by CTA?

11 Young Supernova Remnants (SNRs) See Takeshi s Talk The Astrophysical Journal, 840:74 (14pp), 2017 May HESS ~160 hrs CTA ~50 hrs (sim) HESS Col Acero et al cess image of RX J with overlaid XMM-Newton contours (1 k 50-hrs exposure for RX J and other candidates each after GPS p Ec = 300 TeV. The green contours show (a) XMM-Newton X-ray intensity (e.g., Acero et al. 2009) and (b) total interstel smoothed to match the PSF of CTA. The subtracted image of (b) (a) is also shown in (c). The black contours co (Aharonian et al. 2007a). The unit of color axis is counts pixel 1 for all panels. More photons in > TeV region to study spectral cutoff and hadronic component Higher angular resolution and sensitivity may be able to reveal escaping cosmic rays Differences in the Maximum L 11

12 12 SST Design Proposals SST-2M GCT SST-2M ASTRI SST-1M Need 70 SSTs with less expensive technologies (4-m optics & compact camera) Large FOV (8 ) to detect photons with large core distances SiPM cameras with pixels and compact front-end electronics

13 13 Optical Systems for >8 FOV Schwarzschild Couder (ASTRI and GCT) ASTRI GCT Camera Secondary Davies Cotton (SST-1M) Primary Rodeghiero Credit: SST-1M/CTA

14 SiPM Cameras LST Camera GCT Camera Eff. φ30 mm ~2 m ~40 cm Use of SiPMs enables us to build compact cameras with high pixel density Dedicated compact and modular readout Very NSB tolerant and long SST-only observations (> 5 TeV) are possible 3 or 6 mm 14

15 15 SST-2M GCT (Gamma Cherenkov Telescope) GCT Prototype Paris Observatory 4.0 m CCD Camera 2.0 m (mm) Wide 2D Gaus. Narrow 2D Gaus. White 2017 M1 Star Image m M2 Focal Plane 0.35 m 3.05 m 4.00 m Narrow 3.56 m Wide Built at Meudon site of the Paris Observatory s (very bright sky) 6 segmented aspherical primary mirrors and semi-monolithic secondary Star images by a CCD camera show 6 7 mm PSF size (narrow component) while wide component (scattering by micro roughness) needs to be improved with new Al mirrors 0

16 16 SST-2M GCT Camera First Prototype with Multi-anode PMTs (2015) Second Prototype with SiPMs (2018) Sampling and Tigger ASICs Pre-amps 64-ch MAPMT New ASICs 64-ch SiPM 1 p.e. 2 p.e. Updated the first prototype camera with SiPM arrays Better photon detection efficiency, uniform pixel gain, and better charge resolution New sampling and trigger ASICs for better dynamic range, lower noise, improved trigger efficiency, etc Lab tests and on-telescope observations Charge (arbitrary units)

17 17 GCT First Light CTA s first ever Cherenkov images taken on Nov 26, 2015 CR hadron observations with the first camera and telescope prototype at Paris Observatory The second camera to be tested on the ASTRI telescope prototype in 2018

18 18 mirror replication technology SST-2M ASTRI (Astrofisica con Specchi a Tecnologia replicante Italiana) On-axis Simulation 1.8 m 7 mm (pixel size) 4.3 m CCD Images Credit: CTA/ASTRI Giro Built at INAF-Catania mountain station on Mt. Etna (very active volcano) 18 segmented aspherical primary mirrors + monolithic aspherical secondary ASTRI prototype telescope is the first realization of the Schwarzschild Couder optics with full mirror configuration

19 19 SST-2M ASTRI Camera Image credit: CTA/ASTRI Prototype Camera Camera Lids Front Window 8 8 ch SiPM Backend Electronics Photon Detection Module (SiPM and frontend) 8 8 ch MPPC 37 = 2368 MPPC pixels at the focal plane Dedicated SiPM-readout ASICs (CITIROC) used in front-end electronics Compatible design with SST-2M GCT Pulse height distribution of a single SiPM array

20 20 ASTRI First Light Orion s Belt Image credit: CTA/ASTRI Achieved first light of air-shower images on May 25, 2017 Observed Crab and Mrk 501 but not significant yet Also able to image stars by measuring pixel amplitude variance (proportional to star flux)

21 SST-1M Simulation 0.0 deg Data 4.0 m Pixel size Actis deg Image credit: CTA/SST-1M Conventional Davies Cotton optics with 18 segmented spherical mirrors (less expensive than Schwarzschild Couder) Fully automated system installed at IFJ, Krakow, Poland Optical performance has been verified with star images 21

22 22 SST-1M Camera DigiCam Image credit: CTA/SST-1M Photon Detection Plane Entrance Window Light Concentrators on Hexagonal SiPMs charge resolution Measured Charge Resolution Photon Detection Plane Module 8.9 FOV with 1296-pixel SiPMs and light concentrators Dead-time free fully digital camera (DigiCam) detected light intensity [pe] Not compatible with SST-2Ms but use similar technologies with MST FlashCam -1 no NSB NSB 40 MHz NSB 80 MHz NSB 660 MHz Poisson goal (NSB 125 MHz) requirement (NSB 125 MHz) 2 3

23 23 SST-1M First Light Stacked showers Significance Map Crab 4.2σ (1.2 hrs) Image credit: CTA/SST-1M Achieved first light on Aug 31, 2017 Prototype detected the Crab nebular with 4.2σ excess in test observations New observation campaigns are ongoing in 2018

24 24 SST Harmonization Started Three different approaches are matured and have verified the concept of SSTs But it is time to consolidate the optics and camera designs before SST pre-production phase SST harmonization process started in May 2018 to simplify the southern array with easier maintainability and less construction cost Final SST design proposals to be submitted Oct 2018 Review and evaluation of the final SST design will follow in 2019 Only single acronym, the SST, will be used afterwards :-)

25 25 Timeline We are here! Site hosting agreement for CTA south to be signed Very Large Telescope Proposed Site (~2150 m a.s.l) E-ELT Image CNES/Airbus/DigitalGlobe/Google Earth

26 26 ASTRI Mini Array Image credit: CTA/ASTRI 9 ASTRI telescopes to be built as ASTRI Mini Array in parallel to the SST harmonization Stereo imaging, array trigger, array control etc. will be thoroughly tested ASTRI and GCT cameras can be mounted

27 27 Summary CTA Small-Sized Telescopes will explore the highest-energy gamma-ray frontier from the ground Core energy coverage of TeV 70 telescopes in CTA South Wide-FOV optical system and SiPM camera PeVatrons and cosmic-ray origins Three SST designs; GCT, ASTRI, and SST-1M Verified their functionalities in labs and by first light Harmonization process is ongoing Bigger single SST group will be formed and quickly move toward pre-production and completion