  We present a new preliminary measurement of the b quark fragmentation
function in Z0 decays using a novel kinematic B hadron energy reconstruction
technique. The measurement is performed using 150,000 hadronic Z0 events
recorded in the SLD experiment at SLAC between 1996 and 1997. The small and
stable SLC beam spot and the CCD-based vertex detector are used to reconstruct
topological B-decay vertices with high efficiency and purity, and to provide
precise measurements of the kinematic quantities used in this technique. We
measure the B energy with good efficiency and resolution over the full
kinematic range. We compare the scaled B hadron energy distribution with
several functional forms of the B hadron energy distribution and models of b
quark fragmentation. Several functions including JETSET + Peterson are excluded
by the data. The average scaled energy of the weakly decaying B hadron is
measured to be XB = 0.719 +/- 0.005 (stat) +/- 0.007 (syst) +/- 0.001 (model)
(preliminary).
