The upper, larger disk was epoxied to one of the bowls (after the bowl had been drilled) and the flange on the bottom was custom cut to match the fitting on the pump hose I already had.
Monday, January 25, 2010
Schematic: Custum Vacuum Fitting
The upper, larger disk was epoxied to one of the bowls (after the bowl had been drilled) and the flange on the bottom was custom cut to match the fitting on the pump hose I already had.
Progress Report 1: Vacuum Chamber
The first part of the fusor construction has dealt with creating a vacuum chamber. In order for the fusion reactions to work, a reasonably high vacuum is needed (on the order of 20 to 40 microns). In order to get this vacuum, two things are needed: a good pump (or system of pumps) and a chamber that is vacuum-tight. I managed to scavenge an Alcatel roughing pump, which I will use for the proof-of-concept fusor. For the second iteration, I will incorporate a turbomolecular pump that one of the professors was kind enough to loan me.
As for the chamber, I bought two large, stainless steel mixing bowls with flat flanges to be the main body. The first order of business was making a connector so that the chamber could be attached to the pump. In order to do this, the lab manager and I machined a cylinder of aluminum so that one side could be J-B welded (epoxied) to one of the bowls and the other side would be a connecting flange to the pump hose attachment.
Basic Overview of Fusion
The most common question that I get when I tell people I am trying to build a nuclear reactor is, "Gee isn't that dangerous?!? What if it blows up?" Well, yeah, it is kind of dangerous, but this reactor will never explode, much less produce a mushroom-cloud-worthy blast. It is definitely possible to electrocute oneself, but the "nuclear" part of the reaction is actually pretty safe.
There are many types of nuclear reactions, the most notable being fission and fusion. When people refer to "nuclear energy," they are most likely talking about a fission reactor. In a fission reaction, a nucleus of a heavy element (such as uranium) absorbs a neutron, becomes unstable, and breaks up into two or more smaller elements in addition to shooting off free neutrons. If there is enough of the heavy element in close proximity, the free neutrons from the first reaction will cause more reactions and so on and so forth. If this chain reaction is controlled and moderated, you have the makings of a power plant.
In fusion, the opposite occurs. Instead of a really big element breaking down, two or more small element nuclei combine (i.e. "fuse") into a nucleus of a larger element, also giving off free neutrons in the process. Unlike fission, it is not the free neutrons that sustain the reaction, but the force that is causing the small nuclei to collide and combine.
In a fission reactor, the nuclear reactions are moderated so that the chain reaction cannot spiral out of control. The Chernobyl disaster was an instance where the moderation failed and there was a catastrophic chain reaction. However, in a fusion reactor, this would never happen because an outside force is required to keep the reaction going, and once this outside force was "shut off" the reactions would cease almost instantly.
As far as radiation goes, fusion deals with light elements, such as hydrogen and helium, which in general are not radioactive. Some reactor designs use a radioactive isotope of hydrogen (called tritium) but my reactor will run on a stable hydrogen isotope (called deuterium). The product of the fusion reactions will be a mixture of helium and the aforementioned tritium. The helium is stable, and while tritium is radioactive, it has a very short half-life and low energy decay. Thus, the reactants and products have low, if any, radiation.
While the reactor is running, radiation in the form of fast neutrons will be produced. Although neutron radiation is dangerous, my reactor will not pose a significant nuclear threat anytime soon. First off, I will be lucky to produce enough neutron radiation to notice with measurement devices, let alone be damaging to a person. Secondly, the danger of the radiation drops off exponentially the further away one is from the reactor. In an article by Tom Ligon on the fusor.net website, he says that if one were to stand one meter away from a typical amateur fusion reactor, it would take 12 days of continuous bombardment before the person would even have to start worrying. Finally, as aforementioned, the reactor only produces the fast neutrons while it is on, and because of the finicky nature of the fusion reactions, I will be lucky to be able to contain my reactions for longer than a minute at a time.
To sum it up, as a fusor utilizes fusion instead of fission, my reactor will not be producing radioactive goo or exploding in a giant mushroom cloud anytime soon.
There are many types of nuclear reactions, the most notable being fission and fusion. When people refer to "nuclear energy," they are most likely talking about a fission reactor. In a fission reaction, a nucleus of a heavy element (such as uranium) absorbs a neutron, becomes unstable, and breaks up into two or more smaller elements in addition to shooting off free neutrons. If there is enough of the heavy element in close proximity, the free neutrons from the first reaction will cause more reactions and so on and so forth. If this chain reaction is controlled and moderated, you have the makings of a power plant.
In fusion, the opposite occurs. Instead of a really big element breaking down, two or more small element nuclei combine (i.e. "fuse") into a nucleus of a larger element, also giving off free neutrons in the process. Unlike fission, it is not the free neutrons that sustain the reaction, but the force that is causing the small nuclei to collide and combine.
In a fission reactor, the nuclear reactions are moderated so that the chain reaction cannot spiral out of control. The Chernobyl disaster was an instance where the moderation failed and there was a catastrophic chain reaction. However, in a fusion reactor, this would never happen because an outside force is required to keep the reaction going, and once this outside force was "shut off" the reactions would cease almost instantly.
As far as radiation goes, fusion deals with light elements, such as hydrogen and helium, which in general are not radioactive. Some reactor designs use a radioactive isotope of hydrogen (called tritium) but my reactor will run on a stable hydrogen isotope (called deuterium). The product of the fusion reactions will be a mixture of helium and the aforementioned tritium. The helium is stable, and while tritium is radioactive, it has a very short half-life and low energy decay. Thus, the reactants and products have low, if any, radiation.
While the reactor is running, radiation in the form of fast neutrons will be produced. Although neutron radiation is dangerous, my reactor will not pose a significant nuclear threat anytime soon. First off, I will be lucky to produce enough neutron radiation to notice with measurement devices, let alone be damaging to a person. Secondly, the danger of the radiation drops off exponentially the further away one is from the reactor. In an article by Tom Ligon on the fusor.net website, he says that if one were to stand one meter away from a typical amateur fusion reactor, it would take 12 days of continuous bombardment before the person would even have to start worrying. Finally, as aforementioned, the reactor only produces the fast neutrons while it is on, and because of the finicky nature of the fusion reactions, I will be lucky to be able to contain my reactions for longer than a minute at a time.
To sum it up, as a fusor utilizes fusion instead of fission, my reactor will not be producing radioactive goo or exploding in a giant mushroom cloud anytime soon.
Intro
The purpose of this blog is to document the construction and research on my first Farnsworth-Hirsch fusor. In the coming weeks I will be putting up construction updates, as well as a series of posts on how a fusor works and the basic principles behind it. In my quest to build a fusor, I have been aided by many helpful sites on the internet, and I hope to be able to "give back" with this blog in addition to documenting my progress. Before I start, I would like to thank the folks at fusor.net, Andrew Seltzman of RTFTechnologies, and Raymond Jimenez for their helpful and detailed websites (and e-book!).
I would also like to thank Anatol Hoemke, our lab manager, for all of his help and patience with the construction of the project, Dr. Bulman for helping with the vacuum technology, and Dr. Phillips for loaning me his turbo-pump.
So far, I have been researching the idea of a fusor for about 6 months, and have been accumulating parts. A few weeks ago, I started to construct the fusor in the shop in the physics department at LMU. Right now, I am working on building a vacuum container, a high-voltage power supply, and a feed-through for the IEC grid. Shortly, I hope to have pictures and diagrams up.
**Disclaimer: If you are reading this and decide to build your own fusor, be careful! While this project can be safely constructed and operated, there are several aspects (particularly the high voltage power supply) that can be dangerous and potentially LETHAL in the wrong hands. If you do not have experience working with high voltages, radiation, machine tools, and high-vacuum equipment, find someone who does who can help you. While I encourage potential fusion experimenters to use the information contained in this blog as reference, I take no responsibility or liability for any damage caused by incorrect use of this information. Also, while I will try to be as accurate as possible, especially regarding safety issues, I make no guarantee that the information contained in this blog is completely accurate. Do your homework and check things out yourself. **
I would also like to thank Anatol Hoemke, our lab manager, for all of his help and patience with the construction of the project, Dr. Bulman for helping with the vacuum technology, and Dr. Phillips for loaning me his turbo-pump.
So far, I have been researching the idea of a fusor for about 6 months, and have been accumulating parts. A few weeks ago, I started to construct the fusor in the shop in the physics department at LMU. Right now, I am working on building a vacuum container, a high-voltage power supply, and a feed-through for the IEC grid. Shortly, I hope to have pictures and diagrams up.
**Disclaimer: If you are reading this and decide to build your own fusor, be careful! While this project can be safely constructed and operated, there are several aspects (particularly the high voltage power supply) that can be dangerous and potentially LETHAL in the wrong hands. If you do not have experience working with high voltages, radiation, machine tools, and high-vacuum equipment, find someone who does who can help you. While I encourage potential fusion experimenters to use the information contained in this blog as reference, I take no responsibility or liability for any damage caused by incorrect use of this information. Also, while I will try to be as accurate as possible, especially regarding safety issues, I make no guarantee that the information contained in this blog is completely accurate. Do your homework and check things out yourself. **
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