The day after Ioffe's invitation, Theremin started at the institute. He worked in diverse fields: applying the Laue effect to the new field of X-ray analysis of crystals; using hypnosis to improve measurement-reading accuracy; working with Ivan Pavlov's laboratory; and using gas-filled lamps as measuring devices. He built a high-frequency oscillator to measure the dielectric constant of gases with high precision; Ioffe then urged him to look for other applications using this method, and shortly made the first motion detector for use as a "radio watchman".