Authors: Alberto Leggieri, Davide Passi, Franco di Paolo, Giuseppe Felici, Alessia Ciccotelli, Silvia De Stefano and Filippo Marangoni
Source: FERMAT, Volume 14, Communications 1, Mar Apr., 2016
Abstract: An investigation on the power energy injection in a resonator by electron stream is reported in this paper, by documenting the power transfer between the electron current to a resonant system. The beam current emitted by an electron linear accelerator (LINAC) has been monitored through a particular radiation detector. This device was developed for the dose measurements of a Medical Linear LINAC where monitoring system are required for the real time control of the dose delivered to the patient [1-4]. The power transfer has been observed employing the relation of interaction of the LINAC beam current with a passive resonant cavity [5] placed at the output interface of the accelerator. The LINAC beam current have a bunched form. The spectral content is a line at the accelerating pulsation ω0=2πf and whole-number harmonics [4]. The beam has been used to induce TM010 mode oscillations in a cylindrical cavity at the frequency f [6]. The current drives the cavity in resonance and the energy exchange is heavily regulated by the transit time factor T [7] and the coupling factor k [8]. A magnetic loop antenna is inserted in the cavity in order to perceive the magnetic flux at the TM010 resonance. A voltage induced on the terminals of the magnetic loop is forwarded to an envelope detector through a coaxial transmission line loaded . The envelope detector shows a matched impedance to the loop-cavity system where a certain amount of power is dissipated. The cavity modeling has been performed on POISSON SUPERFISH and the whole system consisting of the cavity and the magnetic loop has been optimized and finally simulated on HFSS version 15 of ANSYS .
Index Terms: Accelerator instrumentation, electron beams, microwave devices, radiation detectors, resonant cavities.
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ELECTRON BEAM DETECTION BY INDUCED RESONANCE IN CYLINDRICAL CAVITY