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NA44 has measured mid-rapidity deuteron spectra from AA collisions atsqrt{s}=18GeV/A at the CERN SPS. Combining these spectra with published proton,antiproton and antideuteron data allows us to calculate, within a coalescenceframework, proton and antiproton source sizes and phase space densities. Theseresults are compared to pion source sizes and densities, pA results and tolower energy (AGS) data. The antiproton source is larger than the proton sourceat sqrt{s}=18GeV/A. The phase space densities of pions and protons are notconstant but grow with system size. Both pi+ and proton radii decrease withtransverse mass and increase with sqrt{s}. Pions and protons do not freeze-outindependently. The nature of their interaction changes as sqrt{s}, and thepion/proton ratio increases.Comment: 4 pages, Latex 2.09, 3 eps figures. Changes for January 2001. The  proton source size is now calculated assuming a more realistic Hulthen,  rather than Gaussian, wavefunction. A new figure shows the effect of this  change which is important for small radii. A second new figure shows the  results of RQMD calculations of the proton source size and phase density.  Because of correlations between position and momentum coalesence does not  show the full proton source size. The paper has been streamlined and  readability improve

(Anti)proton and pion source sizes and phase space densities in heavy ion collisions