2nd Birthday

29 10 2010

Last week this blog turned two years old.

Happy birthday Prometheus Fusion Perfection!





Fast Neutron Counter

28 10 2010

Dear community,

Please help me evaluate this fast neutron counter:

http://www.drct.com/neutron_detection/Pug-7_Fast_Neutron.htm

Is this appropriate for measuring fast neutrons from deuterium-deuterium fusion?

Accurate neutron counts are crucial for both the research and safety.

This meter comes calibrated and is in my budget (barely).





PERSISTENT SUPERCONDUCTING MAGNET VICTORY!!!

21 10 2010

All photos.

I have put the superconducting magnet into a persistent state!!!!!

Power supplies off, magnet still going!

Details to follow.

UPDATE:

OK. Here it is. The units are in raw volts coming from the magnetometer and the current sensing resistor (0.008 ohms). The red is the current going into the superconducting coil, the white is the magnetic field. You can see that the current drops off, but the magnetic field persists. WIN!!!!

The magnetic field gradually falls off over the course of an hour.

This is the setup:

SC coil in the dewar:

Here is the schematic:

It was all controlled manually by switching the power supplies on and off.





Superconducting Magnet Test 3

21 10 2010

All photos.

I re-spooled the YBCO on it’s original spool. Hoping for a stronger magnet and less liquid nitrogen.

We ran 2A DC through the coil at room temperature and David searched for the strongest point of the field.

Which turned out to be the very center, perhaps amplified by the ferrous steel screw:

In this configuration we are seeing ~140 gauss magnetic field while running 5A DC current through the SC magnet submerged in liquid nitrogen (with no persistent switch short circuit):

Much better!

Next we re-fabricated the persistent switch… this time using a much longer splice, better soldering, and a longer heater directly over the splice:

We also included some heat shrink tubing to insulate the heater:

We will test this again today!





Putting it all Together

20 10 2010

All photos.

I’m tackling the challenging task of mounting the equipment for the Sydney Experiment.





Vacuum Check

20 10 2010

All photos.

Just out of curiosity I wanted to see how deep a vacuum I could reach with just the ion gauge connected to the pump.

I tested the pump’s bake-out heater:

Heater switch.

Heater collar.

I let the pump and heater run all afternoon and I got as low as 25 nano torr:

It was still dropping slowly when I finished.

 

I also played around with the Hornet’s RS485 digital interface and Labview, but didn’t get too far.

 





Prototyping

19 10 2010

Just got this sweet breadboard and jumper set. I really needed this!





Superconducting Magnet Test

18 10 2010

All Photos.

I added another terminal to the superconducting coil.

It looks like this:

I operated the coil in the following configuration. About 12cm of SC cable was above the liquid nitrogen forming a resistor.

Putting 5A through the SC coil produced about 20 Gauss.

When I submerged the warm SC cable in liquid nitrogen (leaving the current source on), the field dropped off by half!

The strength of the magnetic field was sensitive to changes in the amount of YBCO at room temperature.

In summary:

We succeeded in directing the current into the main superconducting coil despite the short circuit. GOOD.

When we “turn off the heater” by dunking the warm SC cable into the liquid nitrogen, we lose much of the current going into the main coil.

Not exactly sure how to interpret the results.

My guesses for what’s needed:
1) Longer span of YBCO in the heater.

2) Insulate the heater.

3) Longer splice, better solder joint.





Muriatic Acid

18 10 2010

Finally scored some muriatic acid in Brooklyn at True Value on 558 Metropolitan Avenue.

 

I’ll be using an 18% solution to clean or “pickle” all the parts going into the vacuum chamber.

 

 





Superconducting Magnet Test

16 10 2010

All photos and videos.

Yesterday I tried the the superconducting magnet‘s persistent switch again.

I failed to make a persistent superconductor, but all the circuits and LabView worked properly. More WIN than FAIL.

 

Superconducting magnet submerged in liquid nitrogen.

 

Conceptually this is the circuit we are testing. The heater functions as a variable resistor. The IGBT functions as the switch. Both are computer controlled.

This is the procedure:

I built a LabView VI to trigger the SC coil a variable number of millisecond after the heater:

We can measure the magnetic field produced with the DC magnetometer:

When I ran the experiment with 5A through the SC coil,  I only saw a tiny magnetic field:

6 Gausse from the SC magnet

Furthermore, use of the heater seemed to make no difference at all.

As a control I ran the magnet in this configuration to see what magnetic field strength we should expect:

The produced a much stronger field:

15 Gauss When connected directly.

So the full current is not going through the main coil, but through the heater. I suspect either the heater resistor is not working (I can hear and see it boil the liquid nitrogen) OR the splice in the coil has more resistance than the coil heater:

The last time I ran this experiment the YBCO corroded from condensation:

This time I ran 2A of current through the coil for several hours to warm and evaporate any moisture.








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