  In this work we investigate three variants of single amplification-stage
detector elements; they comprise THGEM electrodes closed at their bottom with
metallic or resistive anodes to form WELL-type configurations. We present the
results of a comparative study of the Thick-WELL (THWELL), Resistive-WELL
(RWELL) and Segmented Resistive WELL (SRWELL), focusing on their performance in
terms of spark-quenching capability, gain variation with position and counting
rate, pulse shapes and signal propagation to neighboring readout pads; the
study included both 30x30 and 100x100 mm$^2$ detectors. It was shown that the
WELL structures with resistive anodes offer stable operation even in a highly
ionizing environment, with effective spark quenching, as well as higher gain
than the standard THGEM/induction-gap configuration. Cross talk between
neighboring readout pads was shown to be effectively eliminated in the
segmented detector with a conductive grid underneath the resistive layer. The
latter multiplier should allow for the design of very thin detectors, e.g.
sampling elements in digital hadronic calorimeters planned for experiments in
future linear colliders.
