The aim of this proposal is to determine the in-plane and out-of-plane structure of H2 in the two dimensional galleries of stage-I calcium-ammonia-graphite intercalates: this class of materials has excellent potential for hydrogen storage and is also of great fundamental interest for studies of confined hydrogen. Our very recent experiment on D20 at the ILL (7-06-57 ¿ report in preparation) has shown that we can prepare Ca-C-ND3 graphite intercalates with layer spacing 6.65Å. This spacing has been predicted as optimimum for H2 storage, which is also aided by the high-charge divalent cations. We now wish to prepare the 6.65Å material in situ on GEM, remove the ammonia (to create room for H2) and then adsorb H2 into the vacant galleries. Throughout this process we will use time-resolved neutron diffraction to measure the structure of the material,while also measuring H2 uptake by TGA.