[en] Laser-ion guiding is currently deployed on the Advanced Test Accelerator (ATA). Beam profiles are measured as a function of time by detecting optical emissions from foils inserted into the beam path. The beam size is observed to grow with time into the pulse. Two other experimental measurements support this observation: (1) vacuum expansion of the beam shows a loss of current in the latter part of the pulse; (2) beam transport through a pipe of reduced diameter results in a similar loss of current in the tail. These observations of increasing beam size are contrary to expectations based on increasing focus strength due to beam-induced ionization. Possible explanations will be presented