Farnsworth Fusor
ref. 1

Fred's Fusor


Contents of this page


May 19, 2017: counting 45,000 page views from 22,730 individual visitors in a total of 159 countries!


The 31st December 2016 at 24:00 hours we were pleased to finish the year. In our opinion and experience a lousy year loaded with disease, hospital visits, and operations, preventing us from making real progress with the Fusor.
We don't know if this has to do with it: the number 2016 is quite peculiar, because for x = 2016 the equation
(x2 + x3) has the solution 8197604352, a result which contains all numbers from 0 to 9 only once!
We consider the start of a new year as a milestone!

On September 26, 2016 we were pleased to count 30,000 page views from 16, 684 individual visitors from 144 different countries. Whatever the objective was for their visit or by which way they found our website we wish everybody a warm welcome!

On March 10, 2016 this website counted 20,000 page views since its first publishing and on the same day 2,000 visitors from the USA had visited our site. In total that date we had received 6,006 individual visitors from 124 different countries. We still encourage feedback!

On June 30, 2015 this website had its first anniversary with the project still in the collecting and constructing phase. The past year the website received 2942 visitors from 107 different countries, who visited 9848 pages. More disappointing is that the site only had one single feedback reaction, no support whatsoever except one negative support experience.


This website will describe all steps in the construction and operation of a Fusor, a "lone nut" project.

A Fusor is an inertial electrostatic confinement device in which colliding nuclei may fuse. With other words a kind of nuclear fusion reactor. The theory and other details of the Fusor can be found in Wikipedia:
Fusor (ref. 2) and the basic principles of nuclear fusion can also be found in Wikipedia: Nuclear Fusion (ref. 3).

The purpose of this website is to provide information about the construction of a Fusor, operated under medium to high vacuum, and to demonstrate its fusing capabilities by injecting Deuterium and detecting the presence of fast neutrons from the reactions:

Deuterium reacties

Both reactions Ia and Ib occur each for 50% and yield Tritium and Helium-3, releasing a proton of 3.02 MeV and a fast energetic neutron of 2.45 MeV. Tritium formed in reaction Ia will react further with Deuterium present in the reactor by forming Helium-4 conform reaction II and release a high energetic neutron with an energy of 14.1 MeV. A neutron detector is therefore the instrument of choice to be used for demonstrating that fusion occurs. The neutron detector will be placed inside a moderator in order to capture the fast neutrons of 2.45 MeV and higher and slowing them down to thermal neutrons with a kinetic energy of about 0.025 eV, which then fall in the range of detection for the neutron detector.

The conditions required for enabling a fusion of Deuterium (i.e. "the project") will be discussed in detail on separate pages, dealing with rationales for choices made, realisation of equipment, tests, discussions of more theoretical approaches of Fusor physics, etc.

A tremendous help for the newbie in Fusor construction is the Forum in Fusor.net (ref.4). It is a source of information on all details of Fusor construction and help is available for answering questions.

The approach of the project is quite different from the approach that would have been used when a professional scientific research project path would have been followed. In that case the starting point would have been
acquiring the budget, followed by developing a project plan, acquiring equipment and constructing and operating the Fusor according to the (approved) plan. Following this path, it would be quite possible that a budget somewhere between 20 - 80 kEUR would be required for a rather simple project like the one we will describe on this website.

At the start of this project, the final construction is not yet known; the budget departs at zero and a fixed plan is totally absent. The Fusor wil get its final shape during the project, fully depending on own efforts and skills and from the parts that will be obtained, based on a very low budget. Therefore, challenges are constantly present and different solutions and/or techniques will have to be found or followed. Once again, the journey is more important than the arrival.

For the construction of an amateur built Fusor the following main system components will be required:
  • Vacuum systems
  • Reactor with connecting lines
  • High voltage power supply
  • Deuterium gas supply
  • Monitoring and measuring equipment
The layout of the website is quite simple: a page (i.e. a chapter) deals with one single subject only and can be read independently from the other pages. Only a very few pages follow from a previous page, which gives the website a rather flat structure:


The index page gives access to all other pages; the bottom row of pages give access to pages in the same row, to the index page (called "home") and to the feedback page.
Most pages have at the bottom a list of references. Addressing a link from a reference will open a new window in your browser.

A continuous story of progress made in obtaining and constructing of any of the main system components can be found on the following separate pages (press button):

theory reactor vacuum HV deuterium monitors

engineering works Ion Source
control systems

fred credits feedback links


It should be noted that the construction of the fusor as described on this web site is a rather ambitious project that probably will take several years before it can be finished and before fusion of deuterium (hopefuly) can be detected. Please observe the "Last Updated" dates and times at the bottom of the individual pages to see if recent progress is obtained in the continuation of the project.

First publication of the Home Page of this website: Monday June 30, 2014
Last update (one or more pages) of this website: Last Updated on: Thu Jun 8 11:49:15 2017
Last pages updated of this website: Last
Before that
Ion Source Engineering Works

Note: All "Last Updated" times at the bottom of all the pages and in the table above are my local time, i.e. GMT+1.

Purpose of the Website

The purpose of this website is mainly for my own purposes. It acts as a kind of notebook for jotting down my (internet) research and personal thoughts and observations. Therefore it is subjected to irregular changes when new insights have been processed. These changes may be radical and could be opposing previous points of view. It is emphasized here that my knowledge of the subject is at start not particularly well developed though the intention is that constant progress will be gained.
In the past a similar way of working was used though by writing the thoughts and observations in a (paper) notebook. The reason to do this on a website is mainly because I prefer to have access to my 'notebook' on all occasions and at all times. Moreover, a website encourages others to share their opinions and additional information with me. You're welcome!

Call for Support

The realization of the Fusor is a time and efforts consuming, privately funded project.
Factors of influence on the timeline of the project are funding, the ability to construct items, obtaining suitable items and the fact that the Fusor is located in France, whereas we change our residence half-yearly.

The last issue is something that cannot be changed but all the other timeline issues can be accelerated when help is offered:

When you have obsolete equipment (privately owned or surplus from your job) that is suitable for the project, please let me know by using the feedback button. Suitable means in working condition or easily repairable. Of particular interest are vacuum pumps (two stage rotary vane, turbo-molecular), vacuum gauges and controllers, vacuum connectors (KF and conflat: tees, crosses,  valves, flexible tubes, etc.), NIM modules, HV equipment (old röntgen transformator, i.e. X-ray transformator, feedthroughs, cable, etc.). For this type of support a restriction has to be applied:  either the distance to be covered for collecting equipment should be less than 80 kilometers around our residency of that moment, or the shipping costs (paid by me) should be within reasonable limits.

When you have skills and a workshop that can offer (free) services,
please let me know by using the feedback button. Of particular interest are milling and turning of components, gas tight welding of stainless steel components, etc. For this type of support the same distance restriction applies as for the preceding paragraph.

When you would like to contribute to the project with a modest financial contribution, please use the donate button below. Your donation is very welcome!

All donations and equipment or skills offers shall be accounted for on a separate webpage: Credits. When you don't want to be mentioned on the credits page, please let me know by sending feedback.

Thank you!


1) Farnsworth Fusor from U.S. Patent 3.386.883 at

2) Wikipedia: Fusor at http://en.wikipedia.org/wiki/Fusor

3) Wikipedia: Nuclear Fusion at http://en.wikipedia.org/wiki/Nuclear_fusion

4) Fusor Net: http://www.fusor.net

5)  Inventory List of Equipment and Parts:  Inventory


This website, including all its individual pages and including its associated websites, does in no way encourage reproduction, construction and operation of the described apparatus, its connected equipment and its described experiments, tests and operational instructions.

Construction and operation of the described apparatus and its connected equipment involves application of lethal high voltages with the risk of electrocution and high vacuum with the risk of implosion possibly causing serious injury or death.

When in operation the described apparatus may produce neutrons, UV-radiation and X-rays, which may be dangerous to your health.

The author cannot be held responsible for any damage caused by disregarding the terms and warnings of this disclaimer or by making use of any information provided by this website.

This website is subjected to constant alterations as more insight may be gained in the process of  developing the apparatus and its connected equipment as well as concerning the underlaying theoretical knowledge.

The information on this website is in no way considered to be complete, exhaustive or up-to-date.

Last Updated on: Mon May 29 10:08:47 2017

Animated GIF's on this website by: Sevenoaks Art

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All schematics and drawings on this website are made with Dia Diagram Editor, free software running on Windows 8.1, 8, 7, Windows Vista and Windows XP, Linux and Mac OS X. For more information please see: http://dia-installer.de/index.html.en

Website made and maintained on an Apple MacBook Air 13":

Replaced in 2016 by a MacBook Pro Retina 15":

Photos made by the author are made with a Contax 645 and
a Phase One digital back:
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