Help me getting FoFu-1's simulation right.

The Focus Fusion Society › Forums › Lawrenceville Plasma Physics Experiment (LPPX) › Help me getting FoFu-1's simulation right.

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  • November 29, 2010 at 6:32 pm #1027
    MTd2
    Participant

    This is where you can get the simulator:

    http://www.plasmafocus.net/IPFS/modelpackage/UPF.htm

    This is just a excel spreadsheet with a macro. Input the data and press ctrl+a to run it.

    I am not sure about the values of LPPX’s device, but I tried cathode/anode radius of 7-5/3.5-2.5 cms, lenght 20-30cm, voltage of 45KV – 100KV, and pressure always above 10Torr. I always adjust the capacitor so that the total energy is always around 100KJ. I also try to maximize yield by playing with the impedance.

    The problem is, I am never able to simulate more than around 0.2KJ (2×10^10 neutrons) of D-D yield.

    Can you?

    November 30, 2010 at 6:04 am #9138
    Lerner
    Participant

    Try this: 18 nH, 113 microF, length 7cm, anode 2.8 cm, cathode 5 cm, 45 kV, 200 torr

    November 30, 2010 at 11:22 am #9140
    MTd2
    Participant

    I am always getting around 5*10 11 neutrons. It should be 15 times more at least… I changed the remaining parameters, but nothing changed much.

    Attached files

    November 30, 2010 at 3:45 pm #9141
    MTd2
    Participant

    I think something is wrong here. Increasing the pressure means either increasing the temperature and/or the mass of the gas. I think these won’t lead to equivalent situations.

    November 30, 2010 at 4:09 pm #9142
    Lerner
    Participant

    Mine is the older version and it gives 10^3 more neutrons. Be interesting to check with Lee what the difference is in the formuale. But our experimental results are way above what the newer formual predicts.

    November 30, 2010 at 4:18 pm #9143
    MTd2
    Participant

    I sent him an email when I started another thread, two weeks ago. He hasn’t answered yet. Maybe you sending now can be more successful.

    BTW, are you sure the new formulas are wrong ? Testing it with 10-20Torr gave exactly the yields you’ve been getting, that is, around 10^10 neutrons.

    November 30, 2010 at 8:01 pm #9145
    Lerner
    Participant

    Try this: 29 nH, 56 microF, length 14cm, anode 2.8 cm, cathode 5 cm, 27 kV, 10 torr . The old Lee program predicts 4×10^11. We got 1.5×10^11. What does the new program predict?

    November 30, 2010 at 8:03 pm #9146
    MTd2
    Participant

    I am at work now, so I cannot check this right now, but what is the correct length, 7 cm, as in your 1st post or 14cm, as the one above? I will give you an answer within 2 hours, anyway.

    November 30, 2010 at 10:51 pm #9147
    Lerner
    Participant

    right now we are using 14 cm, but later on we willbe using 7 cm. The shots were taken with 14 cm.

    November 30, 2010 at 11:04 pm #9148
    MTd2
    Participant

    About 3,77*10 9 , 30 times less than your result. It didn`t change (well, just 10% more, 4,06*10 9) by modifying the length to 7cm.

    Attached files

    November 30, 2010 at 11:09 pm #9149
    MTd2
    Participant

    BTW, when I used T-D reaction, I got 4.18*10 11, with the data you gave me. It seems that, at least the new version, it give your yields, but with D-T instead of D-D.

    November 30, 2010 at 11:22 pm #9150
    MTd2
    Participant

    Lerner wrote: Try this: 18 nH, 113 microF, length 7cm, anode 2.8 cm, cathode 5 cm, 45 kV, 200 torr

    For Deuterium – Tritium, it gives 1.49 * 10 13

    December 1, 2010 at 1:18 am #9151
    Francisl
    Participant

    I was looking at the Theory of Facility for the spreadsheet. At the risk of looking dumb, I request that someone look at the equations. The second page shows the illustrations upside down. We can work with that. The first equation below the illustrations is fundamental to the rest of the paper. The term (b^2 – a^2) on the left side of the equation is changed to (c^2 – 1)a^2 on the right side of the equation. That doesn’t look right to me. I drew a diagram and substituted numbers in the terms and the results are not the same.

    December 1, 2010 at 2:10 am #9152
    Lerner
    Participant

    Using DT is not relevent. We are not using tritium, and although we produce it, it is in very small amounts. The main point is that Dr. Lee’s model predictions dropped by a factor of 100 between the early and late versions. That does not sound right, and I have contacted him about it. The new version is not at all close to our observations, while the old one is. A decimal point error is possible, and very common.
    As to the equation, there is a lot on the Dr. Lee’s site, so I suggest you post a link to the actual paper and what number equation you are questioning, so we can find it.

    December 1, 2010 at 3:13 am #9156
    Francisl
    Participant

    Francisl wrote: I was looking at the Theory of Facility for the spreadsheet. At the risk of looking dumb, I request that someone look at the equations. The second page shows the illustrations upside down. We can work with that. The first equation below the illustrations is fundamental to the rest of the paper. The term (b^2 – a^2) on the left side of the equation is changed to (c^2 – 1)a^2 on the right side of the equation. That doesn’t look right to me. I drew a diagram and substituted numbers in the terms and the results are not the same.

    The link that I meant to post was Theory of Facility. The first equation is on page two of the paper and is the one I am questioning. It is in the first section under Axial Phase. It is the equation for rate of change of momentum.

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