For a heavy ion linac, employing charge strippers is often necessary to improve the performance. The most promising approach, especially for a high-power linac, is to use a liquid metal, thin film as a stripper. Some liquid metals have low vapor pressure and good thermal properties, allowing such a stripper to withstand extreme heat load from ion bombardments. Based on fluid-dynamic, thermal, and nuclear physics considerations, a liquid lithium thin film with the thickness of ~8 μm (0.4 mg/cm 2 ), flowing at >50 m/s may act as the best stripper for a uranium beam at 34+, 12 MeV/u. As the next-stage development, formation of such films is demonstrated at Argonne National Laboratory (ANL). From simple fluid-dynamic considerations, the film thickness and the velocity are estimated to be <～13 ?m and ～58 m/s, respectively. This paper describes how to measure the Li film thickness using low energy electron beams (LEEB). When applied to the Li film, LEEB is absorbed and scattered in the film. Changing the film thickness affects characteristics of the transmitted electrons, from which the film thickness may be back-calculated. Preliminary calculations show that the electron energy of <～30 keV provides the best sensitivity for Li film thicknesses up to 20 μm.
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