TraDeRa aims at monitoring the X-Ray beam upstream to the patient during treatment delivery. TraDeRa is an air vented transmission detector with a patented electrodes design. It will provide a full monitoring of the beam properties (shape and intensity), with measurements in real time, up to the linacpulse scale. Each and every part of the active surface is instrumented : it has no dead zone for a comprehensive monitoring of the beam, up to 40×40 cm² at the isocenter.