Fusor Forums

Just wanted to issue a quick report on my 40 degree circumferential ion source running with deuterium and up to 30kV. Data below. 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) Chamber covered with lead shield, B10 tube in HDPE, Left side device is ion source power supply top view of deuterium beams 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. Some issues to resolve and more experiments to come.
Rich G.

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.

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

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.)

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.

Ion source power supply schematic.
Rich G.

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.

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?

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.

Ok; still nice ion source power supply.

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.