CHARACTERISTICS OF CONDENSED GAS MODERATORS FOR THE GENERATION OF VERY SLOW POLARIZED MUONS

Motivated by the possibility of using condensed gas moderators to prod uce very slow (epithermal) polarized muons we have studied the moderat or properties of rare gas solids and solid N-2 thin films as a functio n of the growing parameters (deposition temperature and rate, heat tre atment) and of the film thickness. For Ar and Kt moderators the modera tion efficiency is found to depend an the growth temperature and an an nealing effect is observed. The dependence can be interpreted in terms of the changes in granularity and porosity of I-he condensed gas laye rs when the growth parameters are varied. From the thickness dependenc e of the moderation efficiency the escape depth, of the very slow muon s was determined, Its large value;indicates a suppression of electroni c energy loss mechanisms for the epithermal muons. The rime dependent decay properties of the moderators were also investigated and found to depend solely on the rest gas pressure. At a pressure of 10(-10) mbar the moderation efficiency remains stable over a period of days. (C) 1 997 American Institute of Physics.