Thickness, L, and rms thickness variation, σ_L, for various detectors, as follows: filled circles–prototype detectors made from SOI wafers for PSP EPI-Hiby the LBNL-Caltech collaboration; unfilled circles–detectors made from SOI wafers for PSP EPI-Hiby Micron Semiconductor; crosses–detectors made from conventional wafers for STEREO LET (Mewaldt et al. 2008) by Micron Semiconductor. The light, dotted lines indicate curves of constant σ_L ∕L with values (top to bottom) of 5, 2, 1, 0.5, 0.2, 0.1, and 0.05%.