Efficient beam extraction from a synchro-cyclotron at n = 1

With an electrostatic deflector placed at n = 1 (the point of maximum Br), about 50 percent of the internal beam (inside n = 0.2) of the 260 cm synchro-cyclotron could be extracted, and most of the extracted beam was confined within a 2.5 cm diameter area at the tank exit by inserting a magnetic channel acting as a focusing lens. The homogeneity of the magnetic field is essential for this method of beam extraction. The configuration and position of the ion source, and the dee bias voltage were found to affect the transmission of the beam through n = 0.2 to n = 1. Under the optimum conditions, 70 to 80 percent of the beam inside n = 0.2 reached n = 1.