Performance of the Illinois Superconducting Linac

The first section of the 1.3 GHz superconducting linac, being constructed for the proposed 600 MeV microtron, was installed into the cryostat and operated as an accelerator for the first time. An electron beam of 270 keV, chopped to a select phase spread of 6 degrees, was injected into the 3λ/2 niobium structure and accelerated to 1 MeV with an input of 30 watts of microwave power at 4.2°K. The accelerated beam was 2 mm in diameter 3 meters beyond the accelerating section. The energy spread was less than 1%. The niobium section had not been outgass d at high temperature and had a Q of 1.4 x 108. The energy gain seemed to be limited to about 1 MeV per foot by field emission, as indicated by the rapid rise of the x-ray yield as the microwave power was increased.