1. Performance of 10-100GeV gamma ray camera for SUBARU optical-infrared telescope A.Asahara*, K.Komiyama#, G.Kosugi#, H.Kubo*, S.Miyazaki#, M.Mori , 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  ICRR, University Tokyo ♭ Tokyo Institute of Technology 1.Introduction 2.Detectors at GeV region 3.High altitude observation 4.“ CheSS ” gamma ray camera 5.Simulation of SUBARU with CheSS 6.Observation report 7.Summary AGENDA

2. 1. Introduction -- Pulsars in 10GeV region -- Polar cap Outer gap Cut off very sharply ~20GeV Cut off more slowly ~50GeV Thompson astro-ph/0101039 Credit: A.K. Harding (NASA/GSFC) Target: Crab pulsar/nebula 1.The standard candle for gamma-ray detectors. 2.SUBARU has a good location to observe it. 3.Wide band pulsed emission Pass through near the zenith. Extend above 10GeV ?

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

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) 0.75deg PMT array 0.1deg 200mm

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

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

8. 5. Simulation of SUBARU with CheSS 1.Night Sky background ~6p.e/trigger 2.Expected trigger rate:0.89 + 26.7 + 1.5 ~30Hz 3.Energy threshold (gamma)~30GeV Jelley(1958) Same as observation data (Using CORSIKA) Cut the event when the sum of photons is under 7p.e

9. Sensitivity -- on-off chopping only -- PulsedUn-pulsed

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

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

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

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.