Field mapping of microtron for radio therapy machine

A compact microtron capable of accelerating electrons up to 12 MeV is desired for the radiotherapy machine. Microtron will be operated at magnetic field of 1926 G. The diameter of the largest orbit corresponding to 12 MeV will be 446 mm. The desired uniformity of magnetic field is within 0.2% in a good field region of 480 mm diameter. To investigate the magnetic field uniformity inside microtron precise measurement of the field profile along various diametric axes is carried out with Hall probe. The length of good field region is extended by introducing the shims. Also field perturbations caused by the RF cavity is studied and presented in the paper. (author)