Justification: We'd like to apply for three days Director’s Discretionary time on WISH to continue the experiment on measures of quantum entanglement in a model 1D magnet. This experiment received the highest rating in the diffraction panel at the FAPs in June (proposal RB1120499 for WISH), and we ran at the end of the October 2011 cycle, getting very exciting results. However, our results are incomplete because of the need to explore the optimal conditions for the experiment, and the relatively slow count-rate. We will be testing the quality of a larger crystal in advance of the experiment. This is a tough experiment but has potentially significant impact because if successful it will as far as we are aware provide the first experimental measurement of an entanglement transition.