Figure 3. Comparison of muographic measurement results.

The plots compare the muon flux measured in different time periods: 14–16 June (red dots) and 17–19 June (blue dots) for different elevation angles (297±16.5 mrad (a) and 264±16.5 mrad (b)). Theoretical flux calculated for various given densities (1.0 and 2.0 g cm⁻³) is also shown for reference. The shaded area indicates 1σ (68% CL) zone. Error bars represent 1 s.d. of statistical uncertainty (1 s.e.). The s.e. was calculated for muon counts in each bin. 2D presentations of the 1σ (68% CL) upper limit of the average density along the muon paths (c and d) are compared between the observation period of 14–16 June (c) and 17–19 June (d). The blue bold dashed line indicates the outline of the cone along the A–B line in Fig. 1b. The conduit diameter determined at an elevation angle of 264±16.5 mrad was extrapolated to an elevation angle of 0 mrad (white broken line). The elevation and horizontal distances at the centre of the cone are also shown in (c) and (d) along with the elevation and azimuth angles.