The Year Leading to a Supereruption
Fig 4
Comparison of CL images and derived intensity profiles using incident electron beam energies of 15 kV (left panels) and 5 kV (right panels).
(A, C, E, G) Data obtained using 15 kV electron beam. (B, D, F, H) Data obtained using 5 kV electron beam. (A-B) Low-resolution images showing a whole quartz crystal with a distinct bright-CL rim. (C-D) High-resolution images (195 nm per pixel) of the contact between bright rim and duller interior (location within the crystal shown in A-B as white rectangle). (E-H) CL intensity profiles extracted from high-resolution images (locations shown), with best fit error functions displayed as gray curves; the length scale of diffusional relaxation (L) extracted from the fitted curves (assuming an initial step function) are indicated, as well as the derived growth times assuming a temperature of 750°C (following [10]). Estimated errors are less than a factor of 2 (see [28] for details), which, despite relatively large, do not affect any of the interpretations or conclusions. (E-F) Calculations showing profiles resulting in minimum growth times (out of 11 parallel profiles) in each case. (G-H) Calculations showing profiles consisting of median values (out of the same 11 parallel profiles) at each position in each case. Crystal is from fall unit F8 (following the nomenclature of [2]), sample F8-15.