A large cross-section Mach-Zehnder interferometer is illuminated by a 30-nsec CO(2) laser pulse. The line-integrated density sensitivity is 2 x 10(19) m(-2). Spatial features down to 150 microm can be identified within a usable field of view of 50 mm. An example of a typical interference pattern obtained on a plasma column is shown together with its corresponding Abel deconvoluted density profile.