Measuring a Billion Degrees
(0) CommentsHow did LPP measure a billion degrees in their Billion Degree Breakthrough? With no ordinary thermometer.
Measuring the energy of the x-rays is done by seeing how much they were absorbed by copper filters of various thickness - the less they were absorbed, the higher their energy. By measuring the ratios of the signals from detectors with different filters, the energy of the x-rays could be calculated. From the energy of the x-rays, we can calculate the energy of the electrons in the plasmoid.
We found that, indeed the plasma was truly hot and generating typical energies ranging from 80 keV to 210 keV (equivalent to 900 million to 2.4 billion degrees), depending on the filling gas used.
We employed another technique to measure the energy of the ions. We used deuterium gas in some shots, which produces neutrons through fusion reactions. By measuring the spread in energy of the neutrons coming from the plasmoid, we could calculate the energy of the ions that produced the neutrons. These energies ranged from 45 to 210 keV (500 million degrees to 2.4 billion degrees).
Our team was able to measure the confinement time by observing the duration of the x-ray and neutron pulses, which were around 50 billionths of a second.
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