MAIN DEVELOPMENTS AT IRIS
The LINAC electron beam was optimized by tuning a set of selective electromagnets while monitoring the electron pulse by the signal collected at a Faraday cup. The pulse width is 4 µs. The beam has a conic shaped geometry, resulting from a scattering foil placed in the beam path and a collimation that determines the cone aperture. The beam profile was evaluated on a plane perpendicular to the cone axis by measuring the change in optical absorption of irradiated glass slides. Radiochromic film dosimetry confirmed the beam profile. Absolute measurements show that the electron beam irradiation dose rate can reach 25 kGy/min (10 MeV electrons and pulse frequency of 150 Hz). This value is an average over a 40 mm diameter circle, placed 16 cm after the beam exit. Beam shaping work is ongoing, as well as preparation of the documentation required to license the installation.
Beam profile obtained with irradiated glass slides, disposed along the X and Y axis of a plane perpendicular to the beam axis, placed at a distance of 55 cm from the beam exit. Along the X-axis the beam profile is slightly distorted, and the measured centre of the beam is deviated 5 mm from the intersection of the cone axis with the plane; RIGHT: beam profile obtained with 1 cm2 irradiated FWT-60 radiochromic dosimeters at 60 cm from the beam exit (values are relative absorbed doses).