Summary of contribution to the ICANS-X panel discussion

The author's role on this panel was to represent that group of users who wish to measure S(Q→,ω) at specified, pre-selected values of Q→ and ω. Until now this kind of measurement has always been reasonably easy to do with a triple axis crystal spectrometer (TACS) at a continuous source of neutrons, and rather more difficult to do with a time-of-flight (TOF) machine at a pulsed source. Only those physicists who were extraordinarily hard-working and persistent managed to get any useful specific s(Q,ω) data, using TOF methods. The lazy physicist simply emigrated to a place where triple axis spectrometers were located, or where he could build new ones. It has not so far been feasible to use a conventional TACS at a pulsed neutron source because there is insufficient time-averaged intensity. The pulsed source user is obliged to use TOF methods, so naturally there has been much effort devoted to making it possible to do specific (Q,ω) measurements with a TOF spectrometer. One of the better examples along these lines if right here at Los Alamos-the Constant Q Spectrometer; PRISMA at ISIS is another excellent example. There are, however, significant limitations to the flexibility of these instruments. It seems likely that they will not be capable of supplanting the conventional TACS for a substantial body of fundamental research work