He3/tritium build up during fusion

[Richard Hull]

How long would you have to run a fusor to reach detectable levels of He3 or Tritium?

Note.... Zero He4 can be made in a fusor. The D2 + D2 = He4 + gamma is a very rare reaction even in nature.

******Detection by RGA *****************

It is a rare RGA that goes to 10e-11 torr without an electron multiplier. Electron multipliers just have to be operated at very low pressures indeed (10e-6 torr or better.

Let us assume one million fusions a second... (Sort of a limit for a simple fusor even at 35kv!).

That means that no more than 500,000 atoms of He3 or of tritium can be made/second. With a stable 1 hour run (unheard of) of a fusor, that would make no more than 1.8X10e9 atoms of each. Remember 1 atmosphere contains roughly 2X10e19 MOLECULES/cc...one torr cc of gas would be, therefore ~10e16 molecules.

Assuming a tiny 2 liter fusor chamber this would mean about 0.9 million atoms of these fusion signature gases/cc of chamber volume or a pressure of 10e-10 torr just detectable with a good RGA but a 100 liter chamber would place the signature below 10e-12 torr. Are my crude, order of magnitude calcs close?

All this assumes a very high rate of one mega fusions/second continuous and uninterupted for one full hour.

Mass 3 should rise. Correct?

****** Detection by Tritium's radiation signature.**********

This has been covered before. Let us assume we have an internal detector capable of detecting any tritium beta particle striking it. 1.8 billion tritium atoms in chamber as above. Half of these will decay in about 11 years. that makes a crude decay rate in the chamber of about 3 counts, chamber wide/second. assuming a detection area of about .1% of the surface area of the chamber, a detection rate of .001 cpm would be optimistic and in the noise. So even after an hour of run time with optimum instrumentation, the radiation signature of tritium would most likely not be detectable.

Comments on any of the above?

Richard Hull

[guest]

It is doubtful to detect any radioemmisions from tritium until it reaches the ppm stage in the whole fusor. If your fusor was of six inch diameter it would take a production in the ten watt to 200 watt range to yield enough to detect. You would have better luck with rga
which is an offshoot of the mass spectrograph it's good for parts per billion... parts per trillion with a helium cooler for a better vacuum. The probability of build up is highly unlikely since these elements burn
more effectively than deuterium.

Larry Leins
Physics Teacher

[Richard Hull]

I knew that the D + T cross section peaked well before 100kev, but the He3 + D section is similar to D + D, I thought.

The 1 part per trillion of T or He3 would never burn on a simple statistical basis, anyhow. They should continue to elevate in level as fusion continues until nearly 3-5% of the total gas volume before joining in the burning on a statistically significant basis. This was also covered in a very old songs list posting.

Richard Hull

[guest]

You are absolutely right about he3 crossection being the same as deuterium. Without rga you would be flying blind on he3 buildup. The 3 to 5 % has yet to verified in experiment. We thought the same thing on yield of thermo nukes ... it was mistaken.

Larry Leins
Physics Teacher