When the nuclear fuel increases in temperature, the rapid motion of the atoms in the fuel causes an effect known as Doppler broadening.
12.
Either one measures the Doppler broadening of the annihilation radiation ( DBAR ) or the angular correlation of the annihilation radiation ( ACAR ).
13.
So Doppler broadening in the moderator, which affects thermal neutrons, does not work, nor does a negative void coefficient of the moderator.
14.
The thermal energy of the nucleus also has an effect; as temperatures rise, Doppler broadening increases the chance of catching a resonance peak.
15.
An increase in fuel temperature also raises U-238's thermal neutron absorption by Doppler broadening, providing negative feedback to help control the reactor.
16.
Doppler broadening of U-238's neutron absorption resonances, increasing absorption as fuel temperature increases, is also an essential negative feedback mechanism for reactor control.
17.
To overcome the problem of Doppler broadening without cooling down the sample to millikelvin temperatures, a classical, and rather general, scheme in experimental physics is used, a pump-probe scheme.
18.
Changes in reactivity in fuel due to temperature stem from a phenomenon known as doppler broadening, where resonance absorption of fast neutrons in fuel filler material prevents those neutrons from thermalizing ( slowing down ).
19.
Saturated absorption spectroscopy, also known as Doppler-free spectroscopy, can be used to find the true frequency of an atomic transition without cooling a sample down to temperatures at which the Doppler broadening is minimal.
20.
The Doppler broadening of gases in motion allows the determination of properties via the resulting frequency shift . Scanning lidars, such as the conical-scanning NASA HARLIE LIDAR, have been used to measure atmospheric wind velocity.
