Absence of a low-temperature anomaly in the Debye-Waller factor of solid {sup 4}He down to 140 mK

The mean-square atomic displacement in hcp-phase solid {sup 4}He has been measured in crystals with a molar volume of 21.3 cm{sup 3}. It is temperature independent from 1 K to 140 mK, with no evidence for an anomaly in the vicinity of the proposed supersolid transition. The mean-square displacement is different for in-plane motions (0.122{+-}0.001 A{sup 2}) and out-of-plane motions (0.150{+-}0.001 A{sup 2})