Due to the relatively small intensity of an ABS the target density of the outcoming jet is limited to 1012 atoms/cm2. To increase the density the atoms are stored in T-shape storage cells that they will leave after ~100 wall collisions or more. Thus, the target density is increased by a factor of 100. But there is a price to be paid: Hydrogen atoms are radicals that react with many different materials and the nuclear polarization is lost.
To investigate the possible processes on the surface of such storage cells a dediated apparatus was built and is now in operation at the IKP-2. Especially the recombiation of the polarized atoms into molecules is of interest, because fully polarized molecules could help to increase the target density due to their lower velocity. More details can be found here (Link: Polarized Molecules).
Actually, CERN is preparing for a polarized storage-cell target in front of the LHCb experiment. Due to technical constraints only a carbon-coated surface would be possible that is under investigations with our apparatus.