We have investigated solid oxygen as a converter material for the production of ultra-cold neutrons. In a first series of experiments the crystal preparation was examined. An optically semi-transparent solid α-oxygen crystal has been prepared. In a second series of experiments such a crystal prepared indentically as in the first series of experiments has been exposed to the cold neutron flux of the MEPHISTO beam line of the FRM II. Ultra-cold neutrons produced inside the oxygen crystal have been extracted and the count rates have been measured at different converter temperatures. The results of these measurements give a clear signal of the superthermal UCN production mechanism in α-oxygen. The mean free loss length of UCN inside the crystal at a temperature of 5\,K was determined to be in the order of 20cm.
@article{arxiv.1006.2970,
title = {Solid oxygen as converter for the production of ultra-cold neutrons},
author = {A. Frei and F. Böhle and R. Bozhanova and E. Gutsmiedl and T. Huber and J. Klenke and S. Paul and S. Wlokka},
journal= {arXiv preprint arXiv:1006.2970},
year = {2011}
}