In my work with anode layer ion sources that are curved to conform to the inner surface of a cylindrical vacuum chamber I have created a third source design. The long term goal being to create a complete 360 degree sheet ion beam where all ions converge at the center of the chamber and accelerated to fusion velocities. My first design was a 40 degree source which would require 9 such source to complete the 360 degree goal. This was too many to be deal with including the 9 power supplies that would be required. The next attempt was a near 180 degree source where only two sources and PSUs would be required (actually 170 degree. Couldn’t get to 180 due to mechanical construction constraints). This large ion source while it works well creating half circle sheet beams was just too powerful. It was difficult to reduce ion current to within the capabilities of my main negative HV power supply.
So for my latest version I’ve gone to a 90 degree ion source where four would be required for the full 360 degree sheet beam. The photos below show two of the 90 degree sources operating. I think this is a good compromise between complexity and overpowering my main PSU. The 90 degree sources are built onto the wall of a ISO160 nipple six inches long and are operated by two full wave rectified MOT power supplies driven by variacs. Details of my first test is included with the photos.
Rich G.
ABOVE: 90 degree anode layer ion sources running with deuterium and no accerating potential. Triangular shaped ion beams converging at the center of the chamber are easily visible. Note shadows of ceramic insulators. There is no negative accelerating voltage present.
Anode electrode is the wall of the vacuum chamber (ground)
Cathode and magnetic pole pieces are the first electrodes away from the wall. V = -500V
Last electrode closest to center of chamber is the suppressor grid (ground). Suppressor grid shields the ionization region from the high negative accelerating voltage. Too much penetration of the high negative accelerating potential tends to quench the ionization.
Black dot in the center is the stalk of the HV feedthrough and connected to ground. Stalk is pointed at the camera.
Pressure = 4 mTorr D2, Ionization current ~ 20 mA each ion source (ionization current is the current flowing between the anode and the pole pieces. It is not the positive ion beam current).
ABOVE: Ion sources running with -20kV applied to the stalk at the center of the chamber. Black dot is the end of the stalk (not a black hole).
Neutron production was 125CPM, -20kV, 7mA PSU, 4mTorr, B10 counter biased at 743V.
Interesting to note that the power in the ion beams (140 Watts) was enough to melt through the stalk of the HV feedthrough. The front 2 inches of the stalk is visible in the photo on the floor of the chamber. The fact that the ion beam melted the 1/8" diameter, 304 stainless steel stalk implies that the sheet beam was concentrated on a small section of the stalk.
ABOVE: Top view of ion sources removed from the main vacuum chamber. The hole in the center is where the HV feedthrough is mounted.
ABOVE: Front head on view of one 90 degree ion source. The electrode in front is the suppressor grid. The carbon steel pole pieces/cathode are behind the suppressor grid.
ABOVE: Side view of the chamber showing the permanent magnets that couple through the chamber wall to the pole pieces. 6 or 8 magnets are used for each ion source. The B field produced in the 0.125” gap between pole pieces inside the chamber is 0.25 Tesla. Voltage to the pole pieces as well as structural support is provided by the four screws that penetrate the chamber wall and are electrically insulated from the wall by ceramic standoffs. The vacuum seal is accomplished by flat Viton washers under each screw. There are 4 screws for each of the two ion sources and the vacuum seal is good enough to reach into the 10-6 Torr range.
The next step will be to attach circular rings to the HV feed through stalk which will provide the high negative potential and accelerate positive ions to fusion relevant velocity and to and provide focusing for the sheet beam in the vertical plane (perpendicular to the sheet). I'm hoping to detect beam on beam (BOB) fusion events.
New 90 degree circumferential ion source
- Rich Gorski
- Posts: 360
- Joined: Mon Aug 01, 2022 4:34 pm
- Real name: Rich Gorski
- Location: Illinois
- Richard Hull
- Moderator
- Posts: 15459
- Joined: Fri Jun 15, 2001 9:44 am
- Real name: Richard Hull
Re: New 90 degree circumferential ion source
You are doing good work in an effort to improve performance. This is the ideal, of course. Your images and work are recognised and appreciated.
Richard Hull
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
-
- Posts: 813
- Joined: Sun Feb 01, 2004 8:02 pm
- Real name: Andrew Seltzman
- Contact:
Re: New 90 degree circumferential ion source
Super cool work Rich. I've always wanted to see what would happen if this was attempted with a radial ALIS design in a fusor.
John Futter did something similar to put DLC coatings on the inner walls of a pipe:
A novel radial anode layer ion source for inner wall pipe coating and materials modification—Hydrogenated diamond-like carbon coatings from butane gas
https://sci-hub.ru/10.1063/1.4892813
John Futter did something similar to put DLC coatings on the inner walls of a pipe:
A novel radial anode layer ion source for inner wall pipe coating and materials modification—Hydrogenated diamond-like carbon coatings from butane gas
https://sci-hub.ru/10.1063/1.4892813
Andrew Seltzman
www.rtftechnologies.org
www.rtftechnologies.org
- Rich Gorski
- Posts: 360
- Joined: Mon Aug 01, 2022 4:34 pm
- Real name: Rich Gorski
- Location: Illinois
Re: New 90 degree circumferential ion source
Richard & Andrew,
Thanks for the compliments. Actually it was Andrew's work and videos about the ALIS that inspired me to go in a different direction with an ALIS design intended for a fusor. Those videos have been a great source of information for me on the construction of these sources. I wanted to use ion sources to improve fusor performance in two ways. First the ion sources would provide much greater ion current than in the typical gridded fusor and secondly I could incorporate a bit of ion optics to provide focusing action in the perpendicular direction to keep the beam in a sheet form and increase ion density. It all worked out well being able to both accelerate the ions to fusion velocities and provide focusing action.
Yes, I became aware of John Futters work in this area after he responded to my earlier posts. Besides the difference in beam direction, outward in John's design, another difference was the need for a suppressor grid to prevent the high negative accelerating potential from quenching the source ionization. I became aware of that issue early in my designs when trying to apply the negative accelerating potential and seeing that the ionization stopped and started up again when the voltage was removed. Now it became obvious why ion thrusters (hall effect type) needed suppressor grids since they also accelerated ions with high negative voltage. The penetration of high negative potential would impede the spiraling action of electrons in the gap region where the crossed EB fields exist.
My effort these days with the ion sources mainly consists of improving the mechanical design and finding the most practical way to include the electrical feedthroughs needed. One problem I'm encountering is that the sources can easily provide more ion current than my Spellman PSU can deliver. This requires a delicate balance between chamber pressure and cathode potential. Something I working to master.
Rich G.
Thanks for the compliments. Actually it was Andrew's work and videos about the ALIS that inspired me to go in a different direction with an ALIS design intended for a fusor. Those videos have been a great source of information for me on the construction of these sources. I wanted to use ion sources to improve fusor performance in two ways. First the ion sources would provide much greater ion current than in the typical gridded fusor and secondly I could incorporate a bit of ion optics to provide focusing action in the perpendicular direction to keep the beam in a sheet form and increase ion density. It all worked out well being able to both accelerate the ions to fusion velocities and provide focusing action.
Yes, I became aware of John Futters work in this area after he responded to my earlier posts. Besides the difference in beam direction, outward in John's design, another difference was the need for a suppressor grid to prevent the high negative accelerating potential from quenching the source ionization. I became aware of that issue early in my designs when trying to apply the negative accelerating potential and seeing that the ionization stopped and started up again when the voltage was removed. Now it became obvious why ion thrusters (hall effect type) needed suppressor grids since they also accelerated ions with high negative voltage. The penetration of high negative potential would impede the spiraling action of electrons in the gap region where the crossed EB fields exist.
My effort these days with the ion sources mainly consists of improving the mechanical design and finding the most practical way to include the electrical feedthroughs needed. One problem I'm encountering is that the sources can easily provide more ion current than my Spellman PSU can deliver. This requires a delicate balance between chamber pressure and cathode potential. Something I working to master.
Rich G.
- Richard Hull
- Moderator
- Posts: 15459
- Joined: Fri Jun 15, 2001 9:44 am
- Real name: Richard Hull
Re: New 90 degree circumferential ion source
Ah! Another man recognizing the the pure artifice of juggling current voltage and pressure in a novel system design.
All the best in figuring out the new "sweet spot" for fusion in this system.
Richard Hull
All the best in figuring out the new "sweet spot" for fusion in this system.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment