IEC Fusion Reactor Mark 3 Construction



Construction in progress. See Fusion Research Progress or main page for updates.


Useful links: Open Source Fusion Research Consortium.



Inertial Electrostatic Confinement (IEC) Fusion is a unique concept developed by Philo T. Farnsworth in the 1960’s. An IEC fusion reactor typically consists of a geodesic inner grid that is held at a negative potential surrounded by a grounded spherical vacuum envelope (outer “grid”). The inner grid emits electrons that are accelerated towards the outer grid by the voltage potential. The emitted electrons ionize deuterium atoms in the sphere by colliding with their electrons which are freed. The ionized deuterium is accelerated towards the center grid by the potential difference.
The central grid is usually fabricated out if several thin interconnected rings; this makes the grid symmetrical yet highly transparent. The accelerated deuterium ions pass through the center grid and collide at the center, often fusing. When the deuterium ions fuse, there are two possible reactions that can occur:

D + D = (50% of the time) 1.01MeV Tritium + 3.02MeV proton
D + D = (50% of the time) 0.82MeV He3 + 2.45 MeV neutron

When a neutron is emitted, it will pass through the reactor walls, where it can be detected, or moderated and used in neutron activation experiments.


IEC Fusion Reactor Mark 3:

The Mark 3 reactor is designed to be highly portable turn key system that can be controlled by Labview over a single USB port.


Core Assembly:

Main components are attached to the reactor core. High voltage feed through connected to accelerating grid, and vacuum hub are attached to axial conflat ports. 8 vacuum ports (4 shown) are attached to the reactor at 45 degree off axis and will be used to accommodate ion injectors and instrumentation.




The reactor core is constructed from two 6" hemispheres joined with 8" conflat flanges. Each hemisphere has 4 ports at 45 degrees for ion injectors and instrumentation as well as one on axis port for vacuum connections (top hemisphere) or grid feedthroughs (bottom hemisphere).


Fluorinert Cooled Ion Focusing Grid:

The implementation of an actively cooled grid system will significantly boost neutron fluxes by removing grid heat due to ion bombardment and allowing higher input power.


Grid Cooling System:

Cools and pumps fluorinert coolant.


Optics system:

Thompson scattering setup to measure plasma density and temperature.


Control System:

Electronic control and computer interface system for the fusor.


Grid Main Power Supply:

X-ray transformer will provide -50kV at 30mA for ion acceleration.


ECRF Ion Injector:

ECRF injector will use the electron cyclotron resonance of electrons within a plasma to sustain ionization.


ECRF Drive System:

RF driver for ECRF injector


Ion Power Supply:

Hitek series 3000 power supply will supply the ion accelerating potential to the ion injectors.


Vacuum Hub:

The vacuum hub connects the reactor core, pressure sensors, and gas handling system evacuation lines to the vacuum system. The vacuum hub contains a servo controlled throttling valve for automatic reactor pressure regulation.


Deuterium Handling:


Deuterium Supply:

Heavy water is electrolyzed to form deuterium and oxygen. The deuterium is then transferred to the reactor. This electrolysis assembly is enclosed in a centrifuge tube that contains the heavy water.


Neutron Detector:

The fusing of deuterium produces fast neutrons with an energy of 2.45 MeV. The detection and quantification of neutron output from an IEC fusor is critical for proving that fusion is occurring. Since neutrons have no charge, they can not be counted by conventional instruments that detect the presence of ionizing particles, such as geiger counters or ionization chambers.

Neutrons must be quantified by their interaction with other nuclei in a detection system. For these interactions to occur, neutrons must be thermalized (slowed down) to the point where they can interact with other nuclei. Neutrons can be thermalized by collisions with protons in a hydrogen rich plastic moderator such as HDPE. As fast neutrons enter the moderator they scatter off the protons, loosing energy in the process. Neutrons passing through the detector tube that are sufficiently slow can be detected and recorded.


Vacuum System:

The reactor system is pumped down with a Sargent Welch 3135 turbo molecular pump backed by a Leybold D2.5E dual stage rotary vain vacuum pump.

The reactor must be operated under high vacuum to obtain the required mean free path, or average distance between collisions, for the deuterium ions being accelerated through the central grid. Operation at lower vacuum levels would cause the deuterium ions to collide with ambient, unionized deuterium in the reactor before they acquired the required energy level for fusion to occur.


Useful links: Open Source Fusion Research Consortium.





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