Pressure Multiplication Effect in Opposed-Anvil Configurations

Abstract

Pressure distribution at room temperature has been studied in sample cells used in the Bridgman opposed-anvil high pressure apparatus over a range of pressure of 25 to 90 kilobars by observation of discontinuities in electrical resistance at phase transitions in calibrated metals (BiI-II, TlII-III, ``low'' Ba, ``high'' Bi). A ``pressure multiplication effect'' has been found in which the pressure observed in the center of the cell is 2 to 2.5 times the nominal load pressure. This effect is strongly dependent on the diameter-to-thickness ratio of the sample cells and is approximately linear to 90 kilobars.