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The laser plasma "beat wave" mechanism for the generation of ultrahigh electric fields requires plasmas of several meters length with density uniformity of about 1 percent. Multiphoton ionization of molecular hydrogen gas at a pressure of a few torr provides a scalable mechanism for generating these plasmas using the same laser beams that drive the beat wave. We describe measurements of electron density, temperature, and uniformity of plasmas generated by a frequency doubled Neodymium glass laser, at an irradiance of about 1014 W Â· cm-2. The plasma density corresponds to 100-percent ionization and is measured to be uniform to within the measurement errors over a length of 8 mm.