Self-powered nano-porous aerogel x-ray sensor employing fast electron current.

Abstract

We developed a new class of aerogel-based thin-film self-powered radiation sensors employing high-energy electron current (HEC) in periodic multilayer (high-Z | polyimide aerogel (PA) | low-Z) electrode microstructures. Low-Z (Al) and high-Z (Ta) electrodes were deposited on 50μm-thick PA films to obtain sensors with Al-PA-Ta-PA-Al structures. Sensors were tested with x rays in the 40-120kVp range and with 2.5MV, 6MV, and 6MV-FFF linac beams (TrueBeam, Varian). Performance of PA-HEC sensors was compared to commercial A12 Farmer ionization chamber as well as to radiation transport simulations using CEPXS/ONEDANT with nanometer-to-micrometer spatial resolution. The computations included periodic and single-element structures N x (Al-PA-Ta-PA-Al) with variable layer thicknesses. Signal from PA-HEC sensors was proportional to the simulated net leakage electron current (averaged over the PA thickness). Experimental response was linear with dose and independent of dose rate. Detector responses to different x-ray sources show higher signals for kVp photon energies, as expected, though a strong signal was obtained for MV energies as well. The signal scaled with total effective area inside the multielemental structures; for example, the yield of a multielement sensor made with 20Ta layers compared to a single-element structure with 1Ta layer of the same total thickness of Ta was 10 times greater for 6MV beam and 23 times greater for 120kVp. Beam attenuation per element in the detector was 0.5%, 1%, 3%, and 46%, respectively for 6MV, 6MV FFF, 2.5MV, and 120kVp. We demonstrated the feasibility of aerogel-based multilayer HEC radiation detector and its application for flux/dose monitoring of kVp and radiotherapy MV beams with small beam attenuation.