Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Hirsch visit - energy conservation
Date: Nov 16, 8:47 pm
Poster: Tom Ligon

On Nov 16, 8:47 pm, Tom Ligon wrote:

>Richard wrote:
>>The particles fall through a potential and acquire energy E and when colliding head on, the net energy is never more than 2E.
>Correct. However, since the relative velocity between the two deuterons is TWICE what it would be if one of them was stationary, the collision dynamics, including probability of nuclear fusion, are the same as a collision between a 4E deuteron and a stationary one. Conservation of energy is not violated because, in the latter case, half of the energy is always "wasted" as translational energy of the two particles AFTER the collision. In other words, the fusor's not getting something for nothing...it's just not wasting half of the particle energy like ordinary accelerators do.
>Since we are using cross-section data obtained by impacting deuterons onto stationary targets, we should therefore continue to use 4E....(I think!)

Since the data for collision crossections are derived from accelerator data with stationary targets, they are valid only if one takes one particle and assumes it stationary. The other particle is therefore at twice the velocity in the case of head-on colliding beams.

It is unfortunate that the original data are expressed in terms of kinetic energy, rather than particle velocity or momentum. This leads to this mis-perception that some violation of conservation of energy is at work. In fact, it is a perfect case of conservation of momentum. It is simply that one must look up or calculate the crossection for 4 x kE to do this frame shift.

At 10 keV you should get about 3 millibarns for head-on collision of two deuteriums.