  We demonstrate sub-Doppler cooling of 40K on the D_1 atomic transition. Using
a gray molasses scheme, we efficiently cool a compressed cloud of 6.5x10^8
atoms from ~ 4\mK to 20uK in 8 ms. After transfer in a quadrupole magnetic
trap, we measure a phase space density of ~10^-5. This technique offers a
promising route for fast evaporation of fermionic 40K.
