Copper coil reactor imposible?

[eros]

I make some calculations and hope that I did some mistake. Maybe people can recheck results? I am not sure if that is already talked, not read all talks yet..

We know that WB6 have 15cm dia, 0.1T and produce 10^9 neutrons, D-D neutrons indicate 1.15mW fusion power.

It is well known also that copper have resistivity 0.017ohm /mm²

Also we got magnet field B=4pii * 10^-7 * NI / L

If make coils that occupy 10% of diameter. (I assume there need to be enough free space, coils can't be 100% or block alfas)

Coils resistivy depends how much copper are used, exact ampere and volts depends how much N. But it seems that power to drive mangnets are konstant at konstant size and accupy area. (if put less N then less ohms but higher I = konstant power)

scaling law B^4 * r^3

I made simple oocalc spredsheet based known WB6 powerlevel and copper resistivy. (there seems no posibility include files in BB?)

I got very disapointing results:
-- 1m machine, coil 10cm (square)
0.1T
needed coil energy 2.71MW
fusion power 0.34W
..
1T
coil energy 778MW
fusion power 3.4kW
..
10T
coil energy 24.8GW
fusion power 34.2MW
..
100T
coil energy ~2500GW
fusion power ~342GW
..
further imposible because some values wrap over..

10m machine, 1m thick coil
0.1T
coil energy 21.6MW
fusion power 0.34kw
..
1T
coil energy 2.5GW
fusion power 3.42MW
..
30T
coil energy ~2100GW
fusion power 2770GW
..

2500m machine 250m thick square coil
0.1T
needed coil energy 5.24GW
fusion power 5.34GW

calc have some insulation and water cool things too included. It is only for magnets energy loss, nothing else.
It seems that copper magnets are imposible to get breakeven.
So carage projects are quite imposible because breakeven needs strong superconducting magnets, very difficult at hobby amateurs. (vacuum is not real broblem, pumps are easy to find used)
But say 2m 5T superconduct reactor may produce 17MW at known WB6 power level. 10m 5T machine go 2GW range..
Current MgB2 superconductors in 5T can conduct 1000A/mm², but machine come expensive because coils use lot of superconducting material. It seems in 10m machine that 5T coils can reduce 0.4m thick at 1000A/mm² level (+hydrogen cyrocenics)
0.2²*pii * 10m * pii * 6pcs = 23.7m³, bulk MgB2 price is level 20000$/m³
conductors maybe 100X more expensive..?

But if people can refine these calculations and recheck results. Biggest unsure is in WB6 power level and is it 100% scalable at scaling rules.
I like to publish that spreadsheet at GPL. Maybe somebody can do javascript conversions and put it web.

[drmike]

I don't quite see how you computed the coil power. I would think the coil power scales linearly with radius where the power generated scales as r^3.

Check out the papers here: http://www.askmar.com/Fusion.html I'm sure it is covered there somewhere.

[eros]

I don't quite see how you computed the coil power. I would think the coil power scales linearly with radius where the power generated scales as r^3.

Check out the papers here:

I used B=4pii * 10^-7 * NI / L that gives needed "ampere turns"
then calculate coil crossection area, divide at N -> got one turn area, calculate wire lengt, use copper resistivity to get wire resistivity, use RI²=P and multiply at six coil.

Fusion power at same B and r as coil, using WB6 0.1T and 15cm konstant, scaling law B^4 * r^3 --> (B/0.1)^4 * (r/0.15)^3 = times WB6 power

So copper coil power scales linear at r if use 10% (or anything else) occupy rule. If keep constant coil cross section diameter power seems to grow at rule r^3.
If grow coil crossection r_x power seems to drop at r_x^-2.
Big coil occupy area close quite fast reactor. I don't know yet how thick coil can be without disturbing too much.

But anyway if calculations are correct it show quite clear that copper coils reactor grow imposible big, atleast that 10% occupy rule.
Even 10m machine at 5T and 5m thick coil are breakeven at 2GW power level..

Research level steady state machine if 30% occupy is posible, 1m machine 30cm thick coil, 0.13T give ~1W fusion power and consume "only" ~400kw coil energy. (only 60L/min boiling hot water etc..)
That is carage or student project posibility level, but breakeven needs superconductors. El bil grow quite fast too..
1m machine and 5T superconductors can give ~2MW fusion power. Huge diffrence..
10T and 1m machine give 34MW.

I'll try read papers soon