Fusion attempt live feed

22 11 2009

We are live tweeting a fusion attempt today. Olivia Koski, a science journalist student is here to document.


2 hours of bakeout prior to metered trial.

Calibration on the bubble detector label: BD-PND, 25 b/mrem(2.3 b/uSv).

Bubble detector is 95mm from the center of the grid.

We got a single bubble during an 8 minute run:

Towards the end of the experiment we noticed a wild outburst of geiger activity while the fusor was _not running_. Not sure what this means. We got it on video:

Using twitter as an experiment log worked very well. It helps capture details you notice along the way with timestamps.

Star Mode

3 11 2009

We got the butterfly value installed and tested out the new grid. Beautiful stable plasmas. Air plasma:


Deuterium plasma in star mode:IMG_4482

No bubbles yet. This video shows the stable air plasma:

Read the rest of this entry »

Second Attempt

25 10 2009

Made a second fusion attempt today with a deuterium plasma. Using the new power supply and the mass flow controller together produced very stable plasmas. I tried a variety of voltages, currents, and pressures but no bubbles.

I have two hypotheses:

a) we are producing fusion, but the detector is not showing it.

b) we are not producing fusion because of grid misalignment.

While double checking the bubble detector, I noticed a relevant detail: the bubble detector must operate within 20˚ C to 40˚C. Today the room temperature was 16˚C. The detector has a built in liquid crystal thermometer. Black means the detector is out of range. To correct this, I put the detector in my pocket for 20 minutes. This warmed the detector to 34˚C :


I want to get a geiger counter as a double check for the bubble detector. The geiger counter would respond to x-rays produced during fusion.

But really I think the problem is that our inner and outer grids are completely misaligned. From what I’ve read grid alignment is necessary for “star mode”. And it seems this is necessary for fusion.

It should be pretty easy to fabricate a new/better pair of grids.

Although we didn’t get fusion today, it was a success in other ways. The system is working smoothly. We have stable plasmas with voltages as high as -17kV. The mass flow controller minimized the deuterium use.

The mass flow controller also lets me adjust the gas flow at a safe distance, which is a welcome upgrade.

Here is a video of the deuterium plasma:

Mass Flow Controller Online

21 10 2009

Big day. Big win. Big upgrade.

Got the mass flow controller online!


Read the rest of this entry »

Deuterium Plasma

13 10 2009

Spent this evening attempting fusion with the Fusor. No bubbles in the detector, but I got these photos of the deuterium plasma:IMG_4278IMG_4277

As you can see it’s a more of a blue color than the air plasma.

The pump is running fantastically… whisper quiet.

I tried for several hours. The main variable is gas flow rate. The more gas, the more current and a brighter plasma.

I may need a higher voltage power supply.

Judging from the reduced PSI of the deuterium bottle, I put a dent in the supply tonight.

All in all it was a good day. Nothing broke. We tool a step forward. I plan to regroup and spend some time working with the air plasma.

Mass Flow Controller

27 09 2009

So I’m making good progress building out the computer control and data acquisition system for the reactor. Currently we have a manually controlled needle valve to regulate flow on the deuterium handling system. I want to replace this with a computer controlled mass flow controller.

A new mass flow controller costs roughly $1,100. There are plenty available on ebay starting from $70.

A mass flow controller must be calibrated for a specific gas. Some can be calibrated on demand with a digital interface, and some are hard wired to work with a specific gas. I’m wondering if we can get away with using a hydrogen calibration for our deuterium system?

The next parameter is flow rate. Here is some background on flow rate nomenclature: flow rate nomenclature. Although mass flow controllers meter based on mass flow rate, they confusingly are rated using volumetric flow rate metrics like SLPM (standard liters per minute), SCCM (standard cubic centimeters per minute) or SCFH (standard cubic feet per hour). Conversion between the two must be done at standard temperature and pressure, and must take into consideration the density of the gas: details.

So before I can spec a mass flow controller I need to calculate our midpoint flow rate needs.

Some facts:

The chamber holds ~6,500 cm^3

The turbo pump removes gas at the following rates:

N2 -> 56 liters/sec

He -> 48  liters/sec

H2 -> 36  liters/sec

So the mass flow controller meters how much fuel is flowing into the chamber. We also want to control how much fuel the vacuum pump is pulling out of the chamber. This requires a gate valve or butterfly valve. Many of them include an integrated bellows connection (which is great), and are pneumatically actuated (not so great).

Adding a gate valve will require us to redesign the welded sled; and I bet it won’t be the last design change. To keep it flexible I’m going to take another page from Andrew and switch to 80/20.

Now my naive attempt to calculate flow rate needs:

Without a gate valve the pumps will remove 2160 l/min. Now the typical mass flow controller seems to max out at 10 SLM (l/min)…. so the pump will remove fuel far faster than the mass flow controller can supply it. And this will waste expensive fuel.

I think these calculation work for pressures in the laminar flow region (> 1e^3 torr). We are working with pressures between the laminar flow domain and the free molecular flow domain – I don’t know how the calculations change at this point.

ps. Wolfram Alpha seems to be useful for density calculations.

Deuterium Handling System

1 09 2009

Got the last bits of plumbing today:


Took about half hour to install:


And with that the first iteration out Fusor is complete. The bubble detectors are purchased and set to ship ASAP. When they arrive we can attempt first fusion. In the meantime I’ll test out the new gas system with air.


Get every new post delivered to your Inbox.

Join 639 other followers

%d bloggers like this: