The longitudinal electric field profile of coherent transition radiation (CTR). which is a radially polarized terahertz (THz) pulse from an electron bunch. was measured using a large-aperture photoconductive antenna (PCA) with a diameter of 8. 8 mm and micro-structured concentric electrodes to detect THz light pulses. https://allfixelectricales.shop/product-category/vacuum-crevice-nozzle/