Novel silicon/aluminum (Si/Al) alloys for use as cold plate materials in cryogenically cooled solid state lasers

The issue of heat transfer in high energy lasers has been a serious problem for years. One valid method of mitigating this problem is the use of low quantum defect solid-state materials operated at cryogenic temperatures1. A significant problem exists due to mismatch of coefficient of thermal expansion (CTE) and repeatedly cycling through a temperature range of ~200 K. Other groups, T.Y. Fan et al at MIT Lincoln Laboratory, have used ingenious crystal holders to overcome this problem. In this paper, we suggest the use of silicon/aluminum (Si/Al) alloys produced by Sandvik Osprey Ltd. that can have their CTE altered easily to match the CTE of whatever crystal material is chosen and still have a thermal transfer coefficient suitable for large heat transfer. We show the results of testing three different Si/Al alloys for CTE and thermal conductivity. We further test the material in a flow boil-off cryogenic cooling system that shows that the CE6 alloy material is capable of heat transfer of 21.5KW/m2K , with cold plate temperatures maintained below 110 K. The CE6 material has a CTE that almost exactly matches YAG from 90--300K.