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Performance of 10-100GeV gamma ray camera for SUBARU optical-infrared telescope

This study discusses the deployment and performance of a gamma-ray camera at the SUBARU telescope for observing pulsars in the 10-100GeV region. The camera, known as CheSS, is designed for high-altitude observations and simulations at SUBARU. The research includes detector specifications, observational reports, and summaries of the study.

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Performance of 10-100GeV gamma ray camera for SUBARU optical-infrared telescope

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  1. Performance of 10-100GeV gamma raycamera for SUBARU optical-infrared telescope A.Asahara*, K.Komiyama#, G.Kosugi#, H.Kubo*, S.Miyazaki#, M.Moric, M.Nakagiri#, D.Nishida*, R.Ogasawara#, R.Orito*, K.Sakurazawa♭, T.Takata#, T.Tanimori* and T.Usuda# ＊Department of Physics, Kyoto University, Japan ＃Subaru Telescope, National Astronomical Observatory cICRR, University Tokyo ♭Tokyo Institute of Technology AGENDA Introduction Detectors at GeV region High altitude observation “CheSS” gamma ray camera Simulation of SUBARU with CheSS Observation report Summary

  2. 1. Introduction-- Pulsars in 10GeV region -- Target: Crab pulsar/nebula • The standard candle for gamma-ray detectors. • SUBARU has a good location to observe it. • Wide band pulsed emission Pass through near the zenith. Extend above 10GeV ? • Polar cap • Outer gap Cut off very sharply ~20GeV Cut off more slowly ~50GeV Credit: A.K. Harding (NASA/GSFC) Thompson astro-ph/0101039

  3. 2. Detectors in 10GeV region Crab Nebula (unpulsed component) Satellite Ground Conventional Cherenkov detectors • COMPTEL • MeV region Over 300GeV • EGRET • ～10GeV Two new type Cherenkov detectors • STACEE One point at 200GeV • CELESTE One point at 60GeV

  4. 3. High Altitude Observation 10GeV gamma-seed (CORSIKA simulation)

  5. SUBARU optical-infrared telescope FOV: 0.75deg Focal length: 15m Mirror diameter: 8.2m Mirror reflectivity: 91%(380nm) Transmittance of correction lenses: 68%(380nm) PMT array 200mm 0.1deg 0.75deg

  6. CheSS Main mirror Prime Focus Unit SUBARU Prime Focus Unit How to set up PMTs SUBARU telescope

  7. Remote control Fast VME-based Electronics PMT array 200mm 200mm 4.CheSS(Cherenkov light detecting System onSubaru) • 44ch VME-TDC (ΔT =0.75nsec) • Onboard VME-CPU • 3ch VME-ADC • GPS module Acceptable trigger rate ～300Hz (dead time 20%) １ｍ photo-cathode area ～233cm (without light guides) 2 • Weight ~200Kg • Power consumption under 700W

  8. 5. Simulation of SUBARU with CheSS • Night Sky background ~6p.e/trigger • Expected trigger rate:0.89 + 26.7 + 1.5 ~30Hz • Energy threshold (gamma) ~30GeV Jelley(1958) Same as observation data Cut the event when the sum of photons is under 7p.e (Using CORSIKA)

  9. Sensitivity -- on-off chopping only -- Pulsed Un-pulsed

  10. 6. Observation log On-Off chopping observation Milky way Crab 5min OFF 10min OFF 12min OFF Target: Crab pulsar Date: 17, 18, and 19, December 2001 Time: on 12hours, off 12hours Weather: Fine 3 chopping modes: 5min, 10min, and 12min

  11. Timing cut ADC cut Clustering cut Shower (Power law) Shower N.S.B Examples of noise reduction N.S.B 35ns shower N.S.B N.S.B Camera image ADC PMT hit timing (measured by TDC)

  12. Trigger rate Data on 17th Trigger rate of raw data ON: 8 - 30Hz OFF: 6 - 22Hz ON OFF Trigger rate after ADC cut (over 3000channel) 0.7Hz - 1.7Hz (depends on zenith angle)

  13. 7. Summary • Gamma-ray pulsars in 10GeV region: • Two emission models. polar cap or outer gap? • Cherenkov light detecting System on SUBARU: • Compact detector. 1m X 1m cylindrical shape, 200 kg weight. • Energy threshold is about 30GeV (simulation). • Observation of Crab • On 17, 18, and 19, Dec 2001 • Total time; On 12hours and Off 12hours.

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