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Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Mon Aug 22, 2016 8:15 pm
by Steven Sesselmann
Andrew,
Did I understand this correctly, the cap was initially not brazed to the cooled grid and so became heated from the ion bombardment, so you have now brazed it to the grid so it now stays cool?
Steven
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Mon Aug 22, 2016 9:05 pm
by Andrew Seltzman
That's correct. The previous version had a molybdenum cap for shielding the lip of the ceramic. The cooling lines just stuck through, making electrical contact, but without making good thermal contact. The new version has a brazed stainless cap.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Mon Aug 22, 2016 11:43 pm
by Richard Hull
Thanks for the info. My shell has no ion sources pointing at one another across the sphere. Those beams on delecate parts in the chamber would be a bad thing.
So much for taking the time to critically align stuff during assembly.
Richard Hull
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Tue Aug 23, 2016 3:05 pm
by Andrew Seltzman
The beams seem very well aligned, the fact that they are hitting near the ion injector ports is due to the electrostatic lensing effect from the grid. The grid consists of 3 rings, and while it resembles a spherical source at a distance, nearer to the grid the discrete effects of the grid rings are noticeable. An ion beam fired directly radially inward at +-45 degrees to the midplane of the vacuum vessel will pass through the grid and bend towards the midplane. When exiting the grid it will be at an angle nearer to horizontal and will strike the shell about halfway between the midplane and the opposing injector port.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Sun Feb 26, 2017 2:05 am
by Andrew Seltzman
I've been working on converting my older CAD files on the fusor into autodesk inventor, here's what I have so far
Cross sectional view
Grid Detail
Grid insulator box detail showing cooling lines
Detail of machined macor grid insulator
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Sun Feb 26, 2017 4:34 am
by Richard Hull
Nice CAD work. Very professional. Fabulous images of what the finished product will resemble. Boy, times, they do change.
I took two classes in engineering drafting while in college in the mid-sixties. We joked about the drafting requirements, saying that should we fail as electronics engineers, we could always find work with International Havester designing self-propelled manure spreaders.
I bought the drafting table and a super nice set of drafting instruments and used them into the early 70's for my own work and pleasure. I still pull them out on occasion, but tend to use simple Computer drafting programs for mechanical stuff and schematic programs for electronic circuit printouts. I have never considered CAD, as I can doodle out a 3-D mechanical impression and see issues develop on that front. Without free access to CAM, I always felt CAD, by itself, a bit over blown. CAD-CAM need to be fully wed and implemented together. My thoughts.
As the brain ossifies, I currently only attempt to learn that which is supremely valuable immediately which is free of any cost. As I am retired, the only new stuff I need to know is that which presents itself in the press of advancing my own personal efforts. I don't have to impress any one person or employer any more. I have a lifetime accumulation of hard won knowledge, about 60% of which is useful now only for campfire stories about how it was in the "old days". This sort of specific, focused knowledge and its application, which the young folks here strive for now, will be part of their campfire story collection in later life, as well. There will always and forever be "this new thing" leaving the bulk of your past efforts and hard won experience, a relic on the trash pile of what was once the cat's pajamas.
All that past effort in life, as you advanced, served to put bread on the table, pay for the car, etc. However, just as the bread ultimately ended up in the sewer system as consumed waste product and the car, in the junk yard, having ferried the family around so valiently, so hot, current, specific skill sets in focused endevors will also fade from being of any real value in future.
This is why I can see the sage, yet sad, Yogi Berra quote in my closing salutation as truly humorous on many levels.
Richard Hull
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Mon Feb 27, 2017 1:56 pm
by Andrew Robinson
Glad to see you pushing into some newer CAD software Andrew. Nice attention to detail. I keep trying to reinforce the usefulness and application of CAD here. With your level of past attention to detail, I know I don't need to try to convince you. I know it can be a daunting task to model everything but very rewarding in the end. We're now pushing into the 1000's of hours on our current model. I'd be happy to talk CAD with you. I'm sure we both have some tips and tricks we can share. Keep it up and as always, I continue to look forward to your progress.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Mon Feb 27, 2017 2:24 pm
by Andrew Robinson
Andrew,
You may be particularly interested in the thermal and flow characteristics we're modeling currently off your original design. Note the continuous feature via 3D sketches to enable the flow and thermal simulations of the grid. This was an early (and incomplete) 3D test and unfortunately I'm not at the office currently so I don't have our updated models or data to share at the moment, but like I said, send me a message sometime. We're investigating heavily into this area and building on your previous success. I would love to share data between teams.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Sat Mar 11, 2017 5:29 pm
by Andrew Robinson
Hey Andrew,
I fired off a few emails to you, but I'm not sure if I have the correct email address. I wont post it here in plain text due to crawlers but are you still at the university/using that email address? Looking forward to hearing back from you.
Cheers,
Andrew
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Sun Mar 12, 2017 4:29 pm
by Andrew Seltzman
I'm here(same address), I sent you a response via email.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA
Posted: Tue Mar 28, 2017 8:01 pm
by Andrew Seltzman
The fusor has been tested with the new molecular drag pump and dry diaphragm pump. The MDP was mounted to the high vacuum solenoid valve on the fusor and was running off of it's built in AC power supply, while the diaphragm pump was running off of the fusor's 24Vdc supply. Vacuum performance was generally good. The solenoid valve between the fusor and MDP was opened at ~100s while the fusor was at ~100mTorr, pump down into the high 1e-4 range occurred with generally good performance. Deuterium pressure was held at ~8mtorr and the fusor generated ~2.3E6n/s at 40kV and 17.6mA, also generally about the same as running with the turbo station.
MDP mounted on fusor
Plasma
My last deuterium tank had run out of pressure, having only ~90psi when I got it, it lasted about a year of intermittent use. New deuterium tank has ~1750psi in it and should last a significant time. The tank is now mounted inside the fusor frame(more compact and better protected) and all VCR fittings have been upgraded to copper o-rings rather then the nylon washers I was using for testing.
The fusor's going to be hooked back up to the old turbo station until I can get the new one with the MDP built though.
Re: Mark3 operation and upgrades
Posted: Sun Jul 08, 2018 5:50 pm
by Andrew Seltzman
A recent upgrade to the mark 3 has replaced the 6 way conflat cube with an 8 way kimball physics vacuum hexagon. The hexagon is considerably smaller and more compact, and has 2 more ports then the cube. The hexagon is connected to the core with a brazed ceramic isolator with copper conflat o-rings, which replaced the PEEK plastic isolator with viton o-ring. In addition the hexagon mounts an MKS 901P with integrated display, x-ray shielded 1.33CF viewport, deuterium inlet valve, Pfeiffer EVI 005 vacuum valve, an electron collector probe on a BNC feedthrough, and a germanium viewport for IR measurements. This upgrade replaced 1 plastic insulator, 2x 2.75CF viton o-rings, 1x KF40 Viton o-ring, and 1x KF16 o-ring with all metal parts, is about 4kg lighter then the previous unit, and significantly more compact, which will allow a diaphragm pump / turbo pump system to be integrated into the frame. The MKS 901P is the RS485 version which will allow several vacuum gauges and the turbopump to talk on the same bus.
The Pfeiffer EVI 005 valve was the one tested in this post
viewtopic.php?f=10&t=12155
The deuterium inlet valve was welded with this procedure:
viewtopic.php?f=6&t=12284
CAD designs on the hexagon are attached below
Pictures of the completed hexagon
Comparison to the old vacuum cube:
Vacuum tests of the new system are very encouraging, the lower conductance of the smaller valve is offset by the removal of the viton and plastic; the system now archives considerably better vacuum performance, and will max out the gauge at below 1e-5 torr.
First pump down with bakeout starting at ~700s and pressure rise with valves closed.
In addition a new digital control system is in the process of being designed, which will replace the older analog feedback controllers with an arduino controller and provide a touchscreen display for monitoring and control
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Mon Jul 09, 2018 2:15 pm
by Richard Hull
Fabulous upgrade Andrew!! One of the better systems out there and a fusioneer that has been around a while. Thanks for the upgrade. I am envious of the valved off 1000+ second hold to about 50 microns. I am at 100 microns after about 360 seconds, but I have operated like this for about 9 years now.
Again, nice stuff! ( as an old friend used to comment to me).
Richard Hull
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Mon Sep 03, 2018 5:58 pm
by Andrew Seltzman
Latest upgrade progress:
Diaphragm pump, rough vacuum gauge, and turbo pump to be installed on fusor frame.
CAD design of mounting position:
Vacuum gauges and turbo pump will share an rs485 bus for communication. The USB to RS485 dongle used for turbo pump testing is the following:
https://www.amazon.com/gp/product/B010K ... UTF8&psc=1
Pump actual speed, set speed, and controller current, voltage, and power.
Matlab control program for pfeiffer turbo pump:
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Wed Oct 17, 2018 12:38 am
by Andrew Seltzman
More upgrades for the fusor:
Upgrades for mounting internal vacuum pumps, custom backing and mounting bracket for the TPD011 turbo pump
Front and back of bracket, replaces the NW16 backing connector and provides 4x 10-32 tapped threads on a 1.75"x97mm pattern
Turbo pump and diaphragm backing pump
Mounting plate to hold vacuum pumps
Locations of vacuum pump within fusor frame
Thermal camera mounting system on vacuum hexagon to observe grid temperature
Right angle bending mirror
Optics path
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sat Nov 10, 2018 9:48 pm
by Andrew Seltzman
The new CNC'd mounting plate for the internal vacuum pumps have arrived and the turbo and diaphragm pump are installed within the fusor frame.
Diaphragm pump, turbo pump and MKS-901P gauge for roughing line pressure measurement are mounted on the aluminum plate.
Plate mounts on top of fusor
Vacuum line connects turbo pump to foreline solenoid valve
Pumps powered up and backing vacuum gauge added to the RS485 bus
Since both gauges are now on the RS485 bus, backing vacuum and high vacuum can be measured simultaneously, pump down was measured with the turbo at standby speed, at full speed the pumping rate increases. On standby, ultimate vacuum is below 1e-5 torr.
Testing of the thermal camera was also successful.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sun Nov 11, 2018 6:11 pm
by Richard Hull
Wow! You are already in the show-piece class and I sense a move into museum grade exposition. This is how it is to be done if one is "long-term serious" about making a world class fusor system and sticking with it. Great work Andrew! Turbo standby mode is more than adequate to do fusion........
Richard Hull
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sun Nov 18, 2018 7:34 am
by Dennis P Brown
Very impressive system. When money is no object, one can create a very professional system!
Your thermal camera might need optical filtering to reduce the intensity since that filament will be in the thousand centigrade range. So you should keep that in mind to provide room for any such pre-lens filtering. Also, noise might be an issue from the EMF.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sun Nov 18, 2018 5:27 pm
by Andrew Seltzman
The thermal camera is viewing the grid during operation, my grid is liquid cooled so it will remain at fairly low temperatures as long as there is coolant flow. There is a little EMI noise on the video, though I have not yet cleaned up the wiring and the video is being sent over twisted pair wire.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sat Feb 02, 2019 12:09 am
by Andrew Seltzman
I have recently added an x-ray camera to one of the fusor's viewports to image the locations electrons are striking the shell through bremsstrahlung intensity distributions.
The x-ray sensor is a Hamamatsu S10814 CsI crystal needle array coated on top of a fiber optic plate collimator/shield coupled to a 1700x1200 CCD detector, controlled by a C9266 USB readout box. This is the industrial equivalent of the modern digital dental x-ray sensors. The sensor has 20x20um pixels, 42x30mm size, 20Lp/mm resolution, and probably on the order of 60 LSB/mR sensitivity.
http://dtsheet.com/doc/569698/hamamatsu-c9266-04
https://www.hamamatsu.com/resources/pdf ... d1124e.pdf
The sensor gets mounted on a thorlabs optical assembly holding a 1.5mm molybdenum pinhole looking through a Pyrex glass viewport which has negligible attenuation for the more energetic x-rays.
The first x-ray images from the camera are shown below
Remember that my fusor has magnetic deflector yokes on 4 of the nipples, shown circled in red.
http://www.rtftechnologies.org/physics/ ... shield.htm
These magnetic deflectors were installed to prevent the electron beam emitted through the grid openings from striking and damaging the optical viewport. Instead of striking the viewport, the beam is deflected into the wall of the nipple. In this case, x-rays from electrons hitting both the near and far nipple walls are visible, along with the x-ray attenuation shadow due to the grid insulator and molybdenum field control cap. The far electron beam is striking the top of the nipple.
Rotating the far deflector field 90 degrees moves the electron beam strike point from the top to the side of the nipple
Rotating the far deflector field 180 degrees moves the electron beam strike point from the top to the bottom of the nipple
Removing the far deflector from the nipple causes the electron beam to illuminate an area of the far nipple behind the grid
In this case the grid wires and insulator are more clearly visible
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sat Feb 02, 2019 8:30 am
by Dennis P Brown
Nice apparatus! A side possibility; you can get single crystal silicon wafers super cheap (even select from the company what plane it was cut - 001, 011 etc.). Set it at the correct angle relative to your camera (maybe a micrometer rotation mount) and use it to get specific energies from the electron x-rays. The wafer need not be in the vacuum just line of sight to the x-ray source. Closer, of course, the better.
A side thought: one could "focus' the x-rays by placing the wafer on a circular vacuum ring and apply a moderate vacuum to deform the wafer into a spherical surface. This will weakly focus grazing x-rays off its front surface to "image" the source and provide an energy spectrum.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sat Feb 02, 2019 11:54 am
by Andrew Seltzman
I'm planning to do something similar for energy. I have some CZT detectors which I'll mount on an x-y drive to position over the part of the image that I want to probe the energy at.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sun Feb 03, 2019 12:07 am
by Andrew Seltzman
Some upgrades to the x-ray camera now include:
Diffrent molybdenum pinhole sizes 1.5mm, 1.0mm, 0.5mm to sharpen the image
A 3D printed sensor holder to allow zooming in by varying the distance from the sensor to the pinhole
Picture taken with a 1.5mm pinhole for 30s:
Picture taken with a 1.0mm pinhole for 30s:
Picture taken with a 0.5mm pinhole for 60s:
Picture taken with a 0.5mm pinhole for 60s (brightened):
Reducing the pinhole size noticeably sharpens the image at the expense of intensity.
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sat Jun 03, 2023 8:07 pm
by Andrew Seltzman
New upgrades on the Mark 3:
New more compact cooling system using 3d-printed components and including more compact coolant pressure and flow measurements
New grid assembly with 3d printed insulator box to allow a more compact design:
Re: Mark3 operation 3e-4 torr / quad ion source @ -40kV, 1mA-9mA
Posted: Sat Jun 03, 2023 11:37 pm
by Richard Hull
Very nice work. We all like to catch up on making out material better or better mounted for control purposes.
Richard Hull