Torsional oscillator and synchrotron x-ray experiments on solid helium in aerogel

A number of Torsional Oscillator experiments have shown that the Non Classical Rotational Inertia fraction in solid $^{4}$He is strongly dependent on sample preparation. Samples presumed to be the most pristine show the smallest fraction, rapidly quenched samples a much larger one. On the assumption that samples grown in a strongly disordered environment would similarly show a large NCRIf, we have made T.O. measurements on solid samples grown in 95{\%} porous silica aerogel. Contrary to expectation, these samples show a behavior that is very similar to high purity samples grown from the superfluid phase. Subsequent x-ray diffraction experiments show that the solid grown in aerogel is highly polycrystalline, with a hcp crystal structure (as in bulk) and a crystallite size of approximately 100 nm. X-ray diffraction experiments were performed at the Advanced Photon Source, Argonne national laboratory. This work was supported through NSF DMR-0706339 (MHWC) and DE-FG01-05ER05-02 (CAB).