Ballistic heat pulses in spin-polarized atomic hydrogen toT=200mK

We have used a heater and bolometer to create and detect ballistic heat pulses of spin-polarized hydrogen atoms (H↓). Energy can be effectively coupled from helium-covered walls to the H↓ gas without recombination. The energy-loss coefficient of H↓ on ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ has been measured to be 0.2 ± 0.1. This technique can be considered as the generation of very-low-velocity atomic beams of H↓, down to 200 mK.