Simple DD fusor

For posts specifically relating to fusor design, construction, and operation.
Post Reply
michaell
Posts: 5
Joined: Tue Feb 06, 2018 8:13 am
Real name: Michael Loundry

Simple DD fusor

Post by michaell » Tue Feb 06, 2018 8:42 am

Dear readers,

I am trying to build very simple fusor based on the Neutristor device.
It would be just little bit bigger.

What I am very concerned is Ion Source. I understand its operation, but since there are many ways how to obtain ions, I am not sure what design can be sufficient. I know that ideally there should be electron source which is knocking electrons from deuterium atoms/molecules.

Please see my scheme.

I wonder if this could work.

Operation is very simple:
1. heating resistor will heat Ion Source to a sufficient temperature to free up some deuterium.
2. High voltage power supply will accelerate deuterium (ions) to the Target.
3. DD fusion should occur

My questions are:
A) Can I use heating resistor instead of directly (electrically) heating the Ion Source?
B) What voltage should I apply to the accelerator?
C) What will strip electrons off?

Thanks a lot
Attachments
fusor.png

User avatar
Dennis P Brown
Posts: 1521
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Simple DD fusor

Post by Dennis P Brown » Tue Feb 06, 2018 2:18 pm

Such a simple ion accelerator has been built numerous times by both professionals (as you site) and amateurs but these are no simple projects since they require both high vacuum and a high voltage source. If you had searched the forum you would have see examples that have been built. No one generally wastes their time building a titanium solid source that requires deuterium gas in order to load and create it. Simply ionizing said deuterium gas is far and away easier for such a project - again, numerous examples of ion guns posted in the forum.

You really need to read the various FAQ's on related subjects as well as do even rudimentary searches here on the forum before posting such previously answered questions.

Michael Bretti
Posts: 146
Joined: Tue Aug 01, 2017 4:58 pm
Real name: Michael Bretti

Re: Simple DD fusor

Post by Michael Bretti » Tue Feb 06, 2018 3:06 pm

While I certainly support efforts regarding other low-cost methods of producing fusion neutrons in addition to the fusor, it seems like you still have a lot to consider for your design if it hopes to be successful. As with others I have discussed other neutron producing devices with, you should really do an exhaustive and thorough amount of research on the subject before diving into it, which would save you a tremendous amount of time, money, and frustration in the long run. To address your points:

A.) Regardless of heat source you use, whether direct or indirect, external or internal, the energy must be enough to actually liberate the deuterium from the titanium. In this case, it would occur through desorption, which can be roughly calculated, and should be calculated to determine if it is sufficient enough for your device.

B.) The voltage depends on the requirements for fusion to occur for DD fusion. In a fusor, generally the bare minimum is in the 20-30kV range. However, this is a very different device. If you see my further explanations below, and the reference paper, field gradients used to accelerate the ions in the neutristor are higher than the applied voltage, for the reasons further explained below. This is necessitated due to the incredible difficulty of applying very high voltages, such as 100KV to such a small device which leaves virtually no spacing for arc-over insulation.

C.) Ionization can occur through a variety of means - thermal, electric, or other forms of radiation. However, by definition, ionization occurs when electrons are removed from, in this case, the liberated deuterium gas. If the outer electrons are not removed to begin with, then the deuterium is not ionized. In this case, the high positive voltage would ionize the gas. Note however that in the neutristor, ionization occurs from thermally liberated electrons due to the initiated vacuum-arc breakdown pulse.

Some things not addressed that need to be considered:

1.) Form Factor - How is this actually being put together? It is one thing to show a device with multiple feedthroughs, especially for very high voltages - it is entirely another matter to actually build it. You say the device is only going to be a little larger than the neutristor. How are you going to account for applying such a high voltage of 100KV to a small feedthrough?

2.) Vacuum - What vacuum levels do you plan to operate at? How do you plan on pulling this vacuum? Note that ion based beam on target systems generally require a much higher level of vacuum than the typical fusor, though if the device is small enough then the mean free path at low vacuum would interfere less. Is it a sealed device or continuously pumped?

3.) Ion Optics - This is potentially a very crucial thing to consider, especially for a small device. If you look at papers dealing with the neutristor, you should be aware that even in such a small device, ion focusing optics are still both employed and modeled. The neutristor has a simple lens after the source, but has one nevertheless. Just spraying ions at a target for beam on target systems is a rather inefficient way of utilizing the extracted ion beam. Ideally you want a high beam density on target, which would equate to more neutrons. Another crucial thing in this topic is the modelling of the ion source. Do you plan on modelling the ion source and optics? Again, referring back to the paper on the neutristor, this has been modeled to determine beam profile and other characteristics of the extracted ion beam. This needs to be addressed. You should also note that in the paper, only 15-20Kv is actually applied to the device, not 100Kv. This again goes back to modeling - the source is made in a way so that there should be a very sharp field gradient resulting in high field enhancement effects at the tip, allowing for an electric field strength of 150kV/cm. In addition, the neutristor is also a pulsed device, operating at around a 10uS pulse at high voltage.

4.) Target Loading - How do you plan on loading the titanium targets with deuterium? Do you have a process or method defined that you plan on doing this prior? Have you calculated the amount of deuterium that would be adsorbed into your pre-loaded targets? The neutristor utilizes both deuterium and tritium - the latter will not be available for you to use. Because the original device utilizes tritium, the threshold for fusion is lower, and produces a higher yield than just purely utilizing deuterium. As is, with the neutristor, neutron yields are still very low, so it is safe to assume that using only deuterium would result in lower yields for equivalent input, making detection harder as well.

5.) Ionization - In the original neutristor, liberation and ionization occurs do to a breakdown mechanism built into the device which results in a vacuum arc that heats, releases, and ionizes the deuterium, which is then focused and accelerated by the lens. What heat is required from your setup to sufficiently liberate deuterium if powered by an external heating source? Have you performed desorption calculation to verify if this heat energy is enough to liberate the required deuterium?

If you have not read this paper yet on the neutristor, I would highly recommend it to see what has currently gone into this device to make it work:

Novel Surface-Mounted Neutron Generator.pdf
(718.72 KiB) Downloaded 85 times

Post Reply