Decay Kinetics and Bose Condensation in a Gas of Spin-Polarized Triplet Helium

We consider the decay kinetics of a trapped spin-polarized gas of metastable triplet helium ${}_{}{}^4{}_{}{}^{}\mathrm{He}(2\mathrm{}{}_{}{}^3{}_{}{}^{}S$ at ultralow temperatures. The sample lifetime is found to be determined by spin relaxation and Penning ionization, both induced by spin-dipole interaction in pair collisions. The rates of these processes are calculated. The Penning ionization proves to be 5 orders of magnitude slower than in the unpolarized case. The results indicate that spin-polarized triplet helium is a promising candidate for Bose-Einstein condensation.