Helicon plasma sources are known to be efficient generators of high-density plasma for materials processing applications. By using multiple sources, arbitrarily large substrates can in principle be covered uniformly with dense plasma. To test this idea, a seven-tube helicon source was constructed, and the plasma density and uniformity measured. Densities up to 10¹² cm^-3 over a 40 cm diameter area with ±3% uniformity were achieved.