Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Fusion Reactors
Name: N/A
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: N/A


Question:
I have been reading about nuclear fusion, and tokamak reactors, and I have a question: how do they achieve the high temperatures of several hundred million degrees? I know that in a hydrogen bomb, which uses fusion,. the use atomic bombs to generate the temperatures to initiate the fusion process. But I do not think that they use atomic bomb blasts in a controlled reactor. So by what means do they use to achieve these spectacular temperatures? to start the fusion reaction?



Replies:
In tokomak's, heating up to a million degrees or more is usually accomplished by resistance (ohmic) heating, just as a wire is heated by passing current through it. In this case the current is generated by coils which induce a current in the plasma. This type of heating is sometimes referred to as I^2 R heating from the formula P=I^2 R. This says that the heating is proportional to the square of the induced current and directly proportional to the resistance. One problem with this method of heating is that the resistance of the plasma can become too small as the plasma temperature increases to allow sufficient heating. Thus supplemental heating is sometimes required. Supplemental heat can be provided by techniques such as: magnetic compression, neutral beam injection, magnetic pumping, laser beam heating, electron beam heating, ion beam heating, or microwave (or radio frequency) radiation. Primarily, though, ohmic heating is the answer to your question.



Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory