First ion temperature profiles in the boundary of Alcator C-Mod

The ion temperature is an important parameter in the boundary of magnetic fusion devices, playing a role in the sheath heat flux, total plasma pressure, plasma potential, and sound speed. High spatial resolution measurements of $T_{i}$ and $T_{e}$ profiles are needed to evaluate these quantities and to unfold the rates of cross-field heat transport in each species. To this end, we have developed two specialized scanning probes: an Ion Sensitive Probe (ISP) and a Retarding Field Analyzer (RFA). Alcator C-Mod is a challenging environment for probes, with parallel heat fluxes comparable to that expected in reactors, 100's MW/m$^{2}$, necessitating the use of refractory materials in compact, optimized geometries. The two probes, along with Charge-eXchange Recombination Spectroscopy (CXRS) measurements of B$^{5+}$ ions, allow important cross-checks to be performed. Preliminary results indicate good agreement between the ISP and RFA. Comparison with B$^{5+}$ CXRS is also favorable. In ohmic-heated, sheath-limited plasmas the ratio of $T_{i}$/$T_{e}$ is $\sim $3 (150 and 50 eV) at the seperatrix and increases to $\sim $5 (50 and 10 eV) at the limiter boundary. Experiments with conduction-limited plasma conditions are planned and will be reported. Implications for boundary electron and ion heat transport will also be discussed.