Many improvements are possible in E864. The DA capacity can easily be increased by a large factor. By increasing the beam rate (not a problem in our proposed location) or target thickness, up to an order of magnitude more events could be recorded without a significant loss of efficiency due to overlapping events.
After gaining experience with the apparatus we could also implement a more sophisticated trigger, allowing the higher interaction rate to be used without actually increasing the number of events recorded.
Both of these two upgrades are relatively easy within the scope of the present design.
A major expansion of the E864 program could be implemented at RHIC using an
internal gas jet target and downstream spectrometer similar to E864 (indeed
many pieces of E864 could be used with minor modification). RHIC
has many advantages: the higher energy at RHIC may be favored over AGS
energies according to recent RQMD calculations [13].
Gas jet operation at RHIC will allow interaction rates up to 
Hz which
would be difficult with an extracted beam. The jet would also be ``thin" so
that seconderies would have negligible rescattering probability. The macro
duty cycle at RHIC is 100%, a very significant advantage relative to the 20%
of AGS fixed target operation. Because the kinematics (Lorentz boost, etc.)
are similar to AGS fixed target operation, the E864 detectors, appropriately
spaced, would remain useful for such an experiment.