1. Z. Cao, H.H. He, J.L. Liu, M. Zha Y. Zhang 2011-02-18 The 2 nd workshop of air shower detection at high altitude

2. Motivation Wide Field of View Cherenkov Telescope Data and MC simulations Preliminary result Outlook WFCTA @ YBJ

3. Hybrid measurement a shower Absolute energy scaler 3

4. Wide field of view Cherenkov telescope array Portable design 5m 2 spherical mirror ； Camera: 16x16 PMT array Pixel size: 1 º x 1 o Field of view: 14 º x16º.

5. Running information Running period 1: 09/ 2008 to 08/ 2010 coincident events with ARGO stereo 500,000 + 89 days + 0.5 Hz mono 810,000 + 168 days + 0.7 Hz – Shower geometry from ARGO – Internal air shower events; – Nhit >1000; – Shower core resolution: < 2 m – Angular resolution: <0.3 o 中心区 监护环

6. Lower energy threshold for one telescope to 15 TeV Running days: 51 days; Mono events: 123, 000;

7. distributions of coincident events ARGO Telescope field of view ~40TeV

8. Corsika6735(QGSJET II + GHEISHA 2002d) + telescope response + trigger Primary particle: proton

9. DATA MC DATA MC

10. Very preliminary result

11. UV LED Mirror UV light 375nm PMT camera  Uncertainty: -- HPD: 4.8% -- Probe: 5% => LED : 6.9% => Calibration constant of camera ： 7.0% Uncertainty: about 10 ％. Using a calibrated Hybrid Photon Diode (HPD) to calibrate probe which has two PMTs and has the same electronics with WTCTA. Using the probe to calibrate UV LED

12. CR composition – J.R. Horandel model – P/ He/ CNO/ Mg/ Iron Energy range – 10 TeV – 10 PeV interaction model: – QGSJETII + SIBYLL Detector simulation – G4argo – WFCTA detector simulation

13. High Energy Hadronic model Uncertainty: <2% (7%) except 250 TeV point

16. nhitAcutLight ratio Heavy ratio 3.0-3.2>1.280%0.8% 3.2-3.4>1.470%0.8% 3.4-3.6>2.054%0.2% 3.6-3.8>2.560%0.5% 3.8-4.0>4.060%0.6%  in(54) /  out (76) > 1.2

17. Xmax information

18. WFCTA has successfully run for 2 years. A very preliminary energy spectrum has been measured. Energy resolution is about 20%@60TeV. Calibration resolution is about 10%. In future – Laser  lower the energy resolution – CR composition separation on sensitive parameters. – to reconstruct X max.

20. Purpose: – Convert FADC count to number of photons; – Monitor PMT camera gain every day. Method: End-to-end calibration – LED relative flux on camera: moving the probe (or sub-cluster) position by position through the whole camera. – LED absolute flux – CRTNT Probe is calibrated by HPD in HiRes lab, Utah, USA – UV LED is calibrated using CRTNT Probe CRTNT Probe UV LED Mirror UV LED at 375nm PMT camera

21. On-line computer Inverse- polarity Amplifier Generator UV LED trigger HPD & FA CRTNT Probe UV light 355nm  CRTNT Probe: -- Two PMTs -- Electronics is the same as two Cherenkov telescopes  CRTNT probe is calibrated by a calibrated Hybrid Photo Diode (HPD) in HiRes lab, Utah, USA. From HPD, we know I LED = #photons/mm 2 (4.8%)  CRTNT probe measures the light flux at the same time: C FADC =Q e (λ) *G*A PMT *I LED => (#phtons/mm2 vs. pulse area);

22. CRTNT Probe Monitor Probe gain.vs. dayProbe gain.vs. temperature

23. Calibration result  Resolution: -- HPD: 4.8% -- CRTNT Probe: 5% => I LED : 6.9%

24. Image cleaning Signal to noise ratio>3.5; Arrival time information: all triggered pixel should be within a time window Δt; Rejection isolated pixel.