was far greater than the value of the resulting electricity. Mechanism of action The energy needed to overcome the Coulomb barrier corresponds to the energy of the average particle in a gas heated to 100 million K. The specific heat of hydrogen is about 14 Joule per gram-K, so considering a 1 milligram fuel pellet, the energy needed to raise the mass as a whole to this temperature is 1.4 megajoules (mJ). In the more widely developed magnetic fusion energy (MFE) approach, confinement times are on the order of one second. However, plasmas can be sustained for minutes. In this case the confinement time represents the amount of time it takes for the energy from the reaction to be lost to the environment - through a variety of mechanisms. For a one second confinement, the density needed to meet the Lawson criterion is about 1014 particles per cubic centimetre (cc). For comparison, air at sea level has about 2.7 x 1019 particles/cc, so the MFE approach has been described as "a good vacuum". Considering a 1 milligram drop of D-T fuel in liquid form, the size is about 1 mm and the density is about 4 x 1020/cc. Nothing holds the fuel together. Heat created by fusion events causes it to expand at the speed of sound, which leads to a confinement time around 2 x 10−10 seconds. At liquid density the required confinement time is about 2 x 10−7s. In this case only about 0.1 percent of the fuel fuses before the drop blows apart. The rate of fusion reactions is a function of density, and density can be improved through compression. If the drop is compressed from 1 mm to 0.1 mm in diameter, the confinement time drops by the same factor of 10, because the particles have less distance to travel before they escape. However, the density, which is the cube of the dimensions, increases by 1,000 times. This means the overall rate of fusion increases 1,000 times while the confinement drops by 10 times, a 100-fold improvement. In this case 10% of the fuel undergoes fusion; 10% of 1 mg of fuel produces about 30 mJ of energy, 30 times the amount needed to compress it to that density. The other key concept in ICF is that the entire fuel mass does not have to be raised to 100 million K. In a fusion bomb the