  X-ray diffraction experiments show that solid 4He grown in aerogel is highly
polycrystalline, with a hcp crystal structure (as in bulk) and a crystallite
size of approximately 100 nm. In contrast to the expectation that the highly
disordered solid will have a large supersolid fraction, torsional oscillator
measurements show a behavior that is strikingly similar to high purity crystals
grown from the superfluid phase. The low temperature supersolid fraction is
only ~3x10-4 and the onset temperature is ~ 100 mK.

Other Condensed Matter