Laser Fusion Fuel Ion Temperature Diagnostics

The fusion fuel ion temperature is a very important implosion dynamics parameter in initial confinement fusion (ICF) research. It is often determined by the neutron time of flight (TOF) technique,1 , 2 which utilizes the neutron Doppler broadening due to the center-of-mass motion of the reacting ions in the fusion fuel. However, the relative yield method has an advantage when the neutron yield is low. On this condition the detector must be placed at a closer distance from the fuel-filled implosion capsule for enough statistical counts, which will cause a narrower neutron TOF width and thus a greater error as the detection system has a certain response time. But it is possible to employ a suitable fuel mixture in which different reactions occur simultaneously although the implosion neutron yield is sensitive not only to the ion temperature alone. Supposing that the final density ratio of the different fusion fuel components in the compressed microballoon core remains constant as compared with the initial one, the relative yield depends only on the ratio of averaged for the different reactions, where σ and v denote the reaction cross section and the relative velocity, respectively. Since the dependence of on temperature is different for different reactions, the relative yield ratio can reflect the ion temperature.3, 4