Abstract
Neutron diffraction patterns for six samples of polycrystalline solid helium have been measured over the angular range 5° to 62° using A neutrons. Four of these specimens were held at °K and 66 atmospheres while the other two were maintained at °K and at 66 and 69 atmospheres, respectively. The diffuse scattering was small at low angles and increased with increasing angle up to 45° beyond which the intensity decreased in much the same way as observed in the scattering patterns from liquid helium. Six lines were observed in the patterns recorded at °K and 66 atmospheres. The positions of the lines are fitted by a hexagonal close-packed structure in which A and A. Within experimenal error no difference is observed between the patterns at °K and °K. The calculated density of solid helium at °K and 66 atmospheres is 0.214±0.006 gram/cc. The mean isothermal compressibility of the solid at °K between the solidus and 66 atmospheres is (3.1±0.8)× .
- Received 26 September 1957
DOI:https://doi.org/10.1103/PhysRev.109.328
©1958 American Physical Society