A search for the Sunyaev-Zel'dovich effect at millimeter wavelengths. [cosmic background photon energy increase due to Compton scattering by high temperature galactic cluster plasma electrons]

We report an initial result in a program to measure the Sunyaev-Zel'dovich effect at frequencies from 3 to 10 cm/sup -1/. The unique spectral characteristics of the effect and the small flux from contaminating astrophysical sources make the millimeter spectral region very attractive for this measurement. We show that the effect of atmospheric fluctuations can be greatly reduced by making multi-freuency measurements. Our measurement of the Zel'dovich effect in Abell 1795 results in a limit on the Comptonization parameter ..delta..y = (-0.4 +- 1.7) x 10/sup -4/ which corresponds to a ..delta..T/sub RJ/ = 0.2 +- 0.9 mK when referred to a change of brightness temperature in the Rayleigh-Jeans limit. These results are not corrected fo the geometrical form factor which depends strongly on models of the cluster plasma.