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: Cross Sections
Date: Jun 13, 11:23 am
Poster: Richard Hull

On Jun 13, 11:23 am, Richard Hull wrote:


I spent some time reading last night and today and it paid off in that I found, in one of my reference books, a nice graph of collisional cross sections for D-D and D-T reactions.

Scott Little, myself and others on this list were wondering about this.

The reference is "Neutron Physics" by Beckurts and Witrz, Springer-Verlag publising, 1964, chapter 2 Neutron Sources, pages 39-41.

Figure 2.5.5.a which shows D-T and D-D curves with respect to energy and collisional cross section, gives the low down for us.

The D-D reaction cross section, at our energy levels of 80KEV, (20kv applied - see earlier posts), is about 10 millibarns (very low). The reaction from here proceeds to increase in cross section, virtually linearly, up to 300KEV (approx 75kv applied) near 50 millibarns. From here it climbs in a slow rolloff to an absolute maximum cross section around 1 mev (250 kv applied) of about 100 millibarns (.1 barn).

The D-T reaction displays a uniform nearly 400X increase over the D-D reaction!!! At our current energy level D-T is looking like 3 barns while our D-D reaction is at .01 barns. In fact the D-T reaction peaks out at only 105KEV and 8 barns!! That would be only 30kv applied to the fusor! Thus, for maxing out a D-T reaction at 105KEV collisional (30KV applied) we are only producing about .0025 times as many neuts with D-D at the same level!! That is 400 times more neuts will be boiling out of a D-T fusor with 30 kv applied than with D-D in the same fusor!

Can you say Tritium?

Mr. Rodgers neighborhood needs tritium!!

I could sure go for a 2.5 magnitude increase in neuts!! Also, once you hit 30kv applied there would be little need to continue much higher. As it stands we would contine to gain neutron numbers all the way up to 250,000 volts on our little D-D fusors and even at that huge voltage be behind the 30kv applied D-T fusor by a factor of 80!

Restated, A D-T fusor runing with 10kv applied (40KEV collisional) would be the equal of a D-D system with 250,000 volts on it!!!

I can say Tritium.

Richard Hull