Two accelerator prototype sections from a Therac 25 radiotherapy accelerator. The accelerator was developed at Chalk River and the technology was transferred to the Radiochemical Company for packaging and sales. These protype units were limited in length by the size by the available brazing furnace to less than 40 cm. One segment is a standard accelerating section while the other also has the radiofrequency coupling port and the vacuum pumping port. Later units were made in a longer brazing furnace with the entire accelerating structure (~2 m long) brazed at one time. The 3 GHz, on-axis coupled, accelerator cells are 7.5 cm in diameter and the beam aperture is 1 cm in diameter.
