  The upper limit on (time reversal symmetry T-violating) permanent hadron
electric dipole moments (EDMs) is the PSI neutron EDM value; $d_n =
(0.0\pm1.1_{\rm stat}\pm0.2_{\rm sys}\times10^{-26})\,e$\,cm. This paper
describes an experiment to be performed at a BNL-proposed CLIP project which is
to be capable of producing intense polarized beams of protons, $p$, helions
(He${}^3$ nuclei), h, and other isotopes.
  The EDM prototype ring PTR (proposed at COSY Lab, Juelich) is expected to
measure individual particle EDMs (for example ${\rm EDM\_p}$ for the proton)
using simultaneous counter-rotating polarized proton beams, with statistical
error $\pm10^{-30}$e.cm after one year running time, four orders of magnitude
less than the PSI neutron EDM upper limit, and with comparable systematic
error.
  A composite particle, the helion faces T-symmetry constraints more
challenging than the proton. Any measurably large value of $$\Delta={\rm
EDM}_h-{\rm EDM}_p,$$ the difference of helion and proton EDMs, would represent
BSM physics.
  The plan is to replicate PTR at BNL. The dominant systematic error would be
canceled two ways, both made possible by phase-locking "doubly-magic" 38.6\,MeV
proton and 39.2\,MeV helion spin tunes. This stabilizes their MDM-induced
in-plane precessions, without affecting their EDM-induced out-of-plane
precessions. The dominant systematic error would therefore cancel in the
meaurement of $\Delta$ in a fixed field configuration.
  Another systematic error cancellation will come from averaging runs for which
both magnetic field and beam circulation directions are reversed. Precise
magnetic field reversal is made possible by the reproducible absolute frequency
phase-locking over long runs to eliminate the need for (impractically precise)
magnetic field measurement. Risk of EDM measurement failure is discussed in a
final appendix.
