MEMORY, CONGRUENCE, AND AVALANCHE EVENTS IN HYSTERETIC CAPILLARY CONDENSATION

We report measurements of the hysteretic capillary condensation of hel ium in the porous material Nuclepore which display a hierarchy of retu rn point memory effects and near congruence of closed internal hystere sis loops. Deviations from predictions based on the Preisach model of independent elementary hysteresis domains, originally developed to und erstand magnetic phenomena, are observed and arc attributed to the app earance of additional domains on draining induced by the internal stru cture of the porous material. Pore intersections result in weak intera ctions among the pores which lead to avalanches.