Apparatus features a sample tube adapter made of conductive material, having a first part to contain and touch a sample tube having a sample therein, and a second part to provide a thermal path for heat transfer to/from the sample tube and a thermal assembly for performing a sample analysis; and sample support rails to receive the sample tube adapter to provide physical support for the sample tube, orient the sample tube adapter in relation to the thermal assembly so there is contact between the sample tube adapter and the thermal assembly to provide the thermal path for heat transfer to/from the sample tube and the thermal assembly, and align the sample tube adapter in relation to a light source so there is a registration between the sample tube and a light beam provided by the light source, all for performing the sample analysis.