Recent studies have shown that fairly weak dilution of the D‐T fuel mixture by the thermal alpha particle population may quench ignition in ITER. The alpha particle exhaust issue is not well understood experimentally, especially in H mode. On DIII‐D, a large set of diagnostics for studying alpha particle thermalization and exhaust are being developed. Helium density profiles in the core plasma are inferred from data obtained by the existing DIII‐D charge‐exchange recombination spectroscopy system which has 32 chords that span the plasma cross section and has been absolutely calibrated so that absolute emission intensities can be inferred from the measured data. Relative chord‐to‐chord intensity calibrations have been made by injecting neutral beams into neutral gas with no magnetic fields. A multifiber system viewing the divertor floor has been absolutely calibrated to measure the hydrogen and helium recycling profile across the divertor floor. Other diagnostics in development include a Penning discharge gauge to measure helium partial pressure under the divertor baffle in DIII‐D. Preliminary measurements from these diagnostics will be presented. This work supported by U.S. Department of Energy (DOE) Contract DE‐AC03‐89ER51114 and by appointment to the DOE Fusion Energy Postdoctoral Research Program administered by Oak Ridge Associated Universities.