What factors make a fusion reaction difficult to achieve?

What factors make a fusion reaction difficult to achieve? In light of these difficulties, discuss the major problems (scientific, engineering, technical, etc.) associated with the development of a controlled fusion reaction that might become a practical source of energy for the world. (Do not include environmental problems, such as radioactive waste, as part of your answer. Consider only those problems associated with producing a controlled fusion reaction in the first place.)What factors make a fusion reaction difficult to achieve?This is really Physics, not chemistry! However I used to work for the school associated with the JET project that has achieved limited fusion. The physicists there always told me the criteria that made it difficult to achieve were:

1] high enough temperature .. about 10^8 C

2] containing the plasma at that temperature using electromagnetic fields

3] stopping the plasma touching the container and losing it



There are straightforward explanations on the JEt site at http://www.jet.efda.org/ .. just click on the fusion basics section