We are live tweeting a fusion attempt today. Olivia Koski, a science journalist student is here to document.
Summary:
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.
The 80/20 arrived. I completed some necessary upgrades to the fusor. We now have proper support for the glass insulator on the high voltage feedthrough:
Previously the glass tube was just hanging there waiting to be broken off.
Mounted all the peripheral electronics:
These upgrades are all about murphy’s law – getting the equipment secured and off the ground prevents an accidental kick from disconnecting wires.
Added a proper mount for the video camera and geiger counter probe:
There was something so satisfying about this particular upgrade. Here is a wide shot of the fusor:
I’ve got plenty of 80/20 left for improvising rigs in the future.
I’m not certain this is all working correctly, but it seems to add up. One oddity: the voltage drops into the negative; perhaps from disabling the high voltage, I’ll have to confirm that.
This is primarily an end to end test of the data acquisition system.
Building and operating the Fusor is a necessary step towards building the Bussard Reactor. The Bussard Reactor is an outgrowth of the Fusor, and the two devices have much in common.
I’ve been doing trials on the fusor all night. Finally GOT IT. WE HAVE FIRST FUSION. LOOK AT THIS BUBBLE:
I had the Glassman power supply maxed out, and the deuterium pressure at ~9 millitorr. The plasma was borderline unstable due to low pressure. The focus of the plasma was maximal. There was a sharp uptick in activity from the geiger counter. The limiting factor was the grid kept heating up and glowing red. I had to cool it off to repeat each trial.
Now that our Fusor seems to be working, I must operate it from a safe distance. Last night I did the first successful remote run. I connected an iSight to the Fusor mac (G4 running OS X Tiger). Then I used VNC to remote control the Fusor mac from my laptop:
I made headway with the command line program to control the fusor and record data in mysql via ruby. It’s currently setup to record vacuum chamber pressure, voltage and current according to the Glassman, and the effective flow rate of the mass flow controller. Currently I can enter commands to turn the high voltage on/off and set the flowrate of the mass flow controller. Next I want to control the voltage and current on the Glassman.
It takes two D batteries. There is a BNC connector for headphones. I have a BNC connector on order with mcmaster. In the meantime I improvised a connection to some computer speakers to test it out. Seems to be working. It picks up the expected background radiation producing that erie clicking sound. You can definitely hear an uptick in the clicks when I run the Fusor.
I’m working towards producing a comprehensive mapping of this device’s performance envelope using computer control to search the parameter space and record the results.
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.
If you’ve been following me on twitter, you know I received a -30kV / 10mA Glassman a few days ago. Now it’s online and it kicks ass. Current limiting, remote controllable… it’s the second unit from the top:
Here is an air plasma it produced:
With current limiting and good air metering, we can get a stable plasma. I notice you get a sense for the plasma just by _listening_ to the glassman. When the plasma is unstable the glassman softly clicks along with the plasma burst.
