Sound amplification by stimulated emission of radiation implies that lasers should be as feasible with sound as they are with light. In the 21st century, it is easy to produce low frequency sound in the range that humans can hear (~20 kHz), in either a random or orderly form. However, at the terahertz frequencies in the regime of phonon laser applications, more difficulties arise. The problem stems from the fact that sound travels much slower than light. This means that the wavelength of sound is much shorter than light at a given frequency. Instead of resulting in orderly, coherent phonon laser structures that can produce terahertz sound,
Neutron stimulated emission computed tomography sample with neutrons, the measured number of emitted gamma rays of energy characteristic to the nucleus of interest is directly proportional to the number of such nuclei along the incident neutron beam trajectory. After repeating the measurement for neutron beam incidence at positions around the sample, an image of the distribution of the nuclei in the sample can be reconstructed as done in tomography. Neutron stimulated emission computed tomography Neutron stimulated emission computed tomography (NSECT) uses induced gamma emission through neutron inelastic scattering to generate images of the spatial distribution of elements in a sample. NSECT has been shown to