Circumferential ion source D2 run

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
Post Reply
User avatar
Rich Gorski
Posts: 133
Joined: Mon Aug 01, 2022 4:34 pm
Real name: Rich Gorski
Location: Illinois

Circumferential ion source D2 run

Post by Rich Gorski »

Just wanted to issue a quick report on my 40 degree circumferential ion source running with deuterium and up to 30kV. Data below.
4-19e.jpg
The B10 proportional tube was biased at 742 volts (Joe, Jim, Richard, thanks for your help determining the correct bias voltage) and placed 21cm from the center of the vacuum chamber. I no longer have the B10 tube connected to the Ludlam model 3. My neutron detection system has been upgraded with a NIM Bin consisting of...
1. Stanford Research HV power supply
2. Canberra preamp.
3. Canberra amplifier with adjustable discriminator
4. Canberra counter (2)
5. Rate meter (expected next week)

As the difference between moderated and moderator removed data shows it seems I'm generating a significant number of neutrons. Possibly all the way down to 15kV. Note the two points showing the moderator removed value of 4CPM at 20kV and 5CPM at 30kV. I don't know any other way of explaining this other than the presence of fast neutrons. I've also measured a back ground count of 3CPM with the fusor off, B10 bias =742V and over a 30 minute time period.

This is not the typical fusor. Maybe its better described as a radial ion accelerator. Running at 1mTorr (1 micron) I can for the most part control the ion beam current and thus the current registering on the main negative HV supply by adjusting the ion source discharge current. The plot above represents an ion beam current that I estimate at 2mA from previous ion source characterization work. I also noted that the main HV supply never exceeded 4mA. The D2 gas supply is from an electrolysis set up that can generate about 400ml/hr from D2O. The D2 gas is stored in a 500ml syringe that can be seen in the last photo.

Photos,

The contraption with the top off. Electrodes going from center to edge. Accelerator (-HV), focus (-1kV), suppressor (ground), ion Pole pieces (-1kV), ion anode (ground)
4-19h.jpg
Chamber covered with lead shield, B10 tube in HDPE, Left side device is ion source power supply
4-19a.jpg
top view of deuterium beams
4-19d.jpg
NIM module showing 291 CPM for the 30kV run.
The monitor shows a side view of the beams taken with a 45 degree angled mirror mounted in the vacuum chamber. The white streak going across the mirror is the two ion beams accelerating into the center from the two ion sources mounted on the chamber wall.
4-19-g.jpg
Some issues to resolve and more experiments to come.
Rich G.
JoeBallantyne
Posts: 326
Joined: Tue Jul 20, 2010 4:08 pm
Real name: Joe Ballantyne
Location: Redmond, WA

Re: Circumferential ion source D2 run

Post by JoeBallantyne »

Great work Rich! I think it is pretty clear you are making neutrons. You should expect a certain level of background neutron counts from cosmic rays completely independent of the neutrons generated in the fusor. So 3-5 neutrons per minute with no moderator is actually to be expected.

Joe.
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Circumferential ion source D2 run

Post by Richard Hull »

Great work and well done with the B-10 tube!
This is an excellent overall string of posts and images over time. It is another shining example of how it is supposed to be done here.
Lots of background with missteps, corrections, improvements, upgrades and final report loaded with a proper chart on detection results and tons of photos of the finished system.

Newbies and wannabes take note of how it is supposed to be done.

Rich, I am placing you in the neutron club.

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
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Circumferential ion source D2 run

Post by Dennis P Brown »

Great work and congrats on getting into the neutron club!

I note that you installed bleed resistors on those caps! Good. Next, enclose those caps so they can't be accidentally touched.

I also note your shielding - again, good work. As Richard stated, a good example for newbie's to follow.

I'd really like to get more details on your power supply (or a link to where you posted it.)
User avatar
Rich Gorski
Posts: 133
Joined: Mon Aug 01, 2022 4:34 pm
Real name: Rich Gorski
Location: Illinois

Re: Circumferential ion source D2 run

Post by Rich Gorski »

Dennis,

The supply is a simple 60 Hz, full wave rectifier, DC supply running off a microwave transformer powered by a variac. The output caps are 0.5uF, 10kV. What you see in the photo is actually two separate supplies. One for the discharge current on the ion sources and one to supply the focus potential. The outputs are connected to the ion sources and focus grid through a 5k, 25W current limit resistor. They are pretty hefty with those MOTs and can deliver 100mA at 3.5kV.

I'll post a schematic shortly.

Rich G.
User avatar
Rich Gorski
Posts: 133
Joined: Mon Aug 01, 2022 4:34 pm
Real name: Rich Gorski
Location: Illinois

Re: Circumferential ion source D2 run

Post by Rich Gorski »

Ion source power supply schematic.
Ion HV supply.jpg
Rich G.
User avatar
Rich Gorski
Posts: 133
Joined: Mon Aug 01, 2022 4:34 pm
Real name: Rich Gorski
Location: Illinois

Re: Circumferential ion source D2 run

Post by Rich Gorski »

Richard,

Wow, I’m in the neutron club… that made my day! Time to celebrate. My efforts will continue both in my own fusion related activities and in helping others on this site to achieve their goals. I’m so glad for fusor.net as there’s isn’t anywhere else amateur scientists can go to communicate with others working in this field. Knowing that people are out there that understand and engage gives all of us incentive to continue. This is important. So thanks to you all for keeping this site going. I will continue to post with news of my successes and failures or useful information to share.

As the Jedi master Yoda said “Failure, the greatest teacher it is” How true is that!

Rich G.
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Circumferential ion source D2 run

Post by Dennis P Brown »

You got good fusion with a power supply under 10 kV? So, the voltage was about 3.5 kV? Wow - that is an impressive accomplishment. Wonder if anyone else has achieved detectable fusion in that low range?
User avatar
Rich Gorski
Posts: 133
Joined: Mon Aug 01, 2022 4:34 pm
Real name: Rich Gorski
Location: Illinois

Re: Circumferential ion source D2 run

Post by Rich Gorski »

No, sorry that I confused you. The 3.5kV supply in only to power the ion sources which typically need about 1kV to create the ionization from which ions are extracted. This low energy beam emitted <1keV is then further accelerated by the main negative power supply to fusion energy of at least 15kV. The main power supply is a Spellman DXR3000 and in my neutron data was running from 15kV to 30kV. I'll create a schematic of the entire system and post that. It will clarify things.

Rich G.
User avatar
Dennis P Brown
Posts: 3159
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis Brown

Re: Circumferential ion source D2 run

Post by Dennis P Brown »

Ok; still nice ion source power supply.
User avatar
Rich Gorski
Posts: 133
Joined: Mon Aug 01, 2022 4:34 pm
Real name: Rich Gorski
Location: Illinois

Re: Circumferential ion source D2 run

Post by Rich Gorski »

Hi everyone,

Below is the electrical/mech schematic of the ring ion accelerator. There is no gas input as it runs on the ambient gas in the chamber.
I've also include a computer simulation showing the potential distribution for 30kV operation.

Rich G.
ring assel-sch.jpg
ring-potmap.jpg
Post Reply

Return to “Ion Gun Design and Construction (& FAQs)”