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://www.ealisboa.com/best-flash-Nightstick-TWM-850XL-Tactical-Weapon-Mounted-Light-limited-super/