ASCE

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The Air Shower Core Experiment

Asce.gif The Sydney Air-Shower Core Experiment (ASCE) was designed to measure the core structure of extensive air-showers (EAS). These cores exhibit a high density flux of the electron/photon and hadron components of the shower and can be used for a better understanding of the particle interactions near the axis that could lead to a better knowledge of the primary composition of the primary particles that initiate the shower.

This experiment was fully operational between 1989 until 1991. Triggered by an array of 8 scintillators, it measured the particle densities of the air-shower cores using an array of Multi-Wire Proportional Chambers (MWPC) of area 4.0 m x 3.4 m working in the proportional mode. The low density of the gas medium in the chambers ensured that the energy threshold for the detection of shower particles was as low as possible and that it had minimal influence in the measurement of the density of shower particles.

About 124,000 showers were recorded by the scintillator array in a period of 523 days and 6210 showers also exhibited a core inside the MWPC array. Most showers exhibited a single core structure but some were observed with multiple-cores. The single core showers were used in a further analysis if their core was well contained inside the MWPC array. A set of 406 showers survived these cuts. The main results found by this experiment are summarised below.

  • It was found that the average age of the showers did not change with size. There had been hints by previous experiments that this might not be the case (E.R. Bagge, M.Samorski, W. Stamm, Proc. 16th Int. Cosmic Ray Conf., Kyoto, 13 (1979) 260; and K. Asakimori et al., Proc. 18th Int. Cosmic Ray Conf., Bangalore, 11 (1983) 189.) but it is believed now that the higher density of their detectors probably affected the local shower densities.
  • The density spectrum of extensive air-showers was measured to have a power law formula with spectral index -2.77 for a particle density of greater than 400 particles per square metre inside an area of 1.3 m x 1.2 m.

Publications:

  • Sun Luorui, M.M. Winn, A Small Cosmic Ray Air Shower Array using Plastic Scintillators and a NIM/CAMAC Recording System, Nucl. Instr. and Meth. 223 (1984), 173.
  • L. Horton, A. Nasri, J. Ulrichs, M.M. Winn, The Sydney Air-Shower Core Detector, Analysis of Subcore Structure, Proceedings of the 21st International Cosmic Ray Conference, Vol. 9, Adelaide, (1990), 54.
  • L. Horton, A. Nasri, J. Ulrichs, M.M. Winn, The Sydney Air-Shower Core Detector, a Preliminary Interpretation of Results, Proceedings of the 21st International Cosmic Ray Conference, Vol. 9, Adelaide, (1990), 55.
  • L. Horton, A. Nasri, J. Ulrichs, M.M. Winn, The Sydney Air-Shower Core Detector, Analysis of Response, Proceedings of the 21st International Cosmic Ray Conference, Vol. 10, Adelaide, (1990), 306.
  • L. Horton, J. Ulrichs, M.M. Winn, B. Yabsley, The Core Structure of Extensive Air Showers as Recorded with an Array of Multi-Wire Proportional Counters (MWPCs), Proceedings of the 22nd International Cosmic Ray Conference, Dublin, 4 (1991), 261.
  • J. Ulrichs, M.M. Winn, B. Yabsley, The Density Spectrum of Extensive Air Showers taken with Multi-Wire Proportional Counters (MWPCs), Proceedings of the 22nd International Cosmic Ray Conference, Dublin, 4 (1991), 265.
  • L. Horton, J. Ulrichs, M.M. Winn, The Response of Multi-Wire Proportional Counters (MWPCs) to Air Shower Particles, Proceedings of the 22nd International Cosmic Ray Conference, Dublin, 4 (1991), 488.
  • L. Horton, J. Ulrichs, M.M. Winn, The Use of Multiwire Proportional Counters in a Cosmic Ray Air Shower Experiment, Nucl. Instr. and Meth. A325 (1993), 326-334.