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I know in our systems we have problems with out gassing rather than leaking. But 10^-4torr it shouldn’t that bad I assume. We where going down to 10-8 and outgassing even after long bake periods where constantly a problem.

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This is not true. Many of the MRI machines are open loop cooling. That is the He boils off into the atmosphere. This is very common for most scientific MRI machines, even very new ones. You simply can’t use that sort of He tonnage a year without dumping most of it into the atmosphere.

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The moom has helium in the parts per *billion* range.

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Its not surprising since this is what the thing was built for in the first place.

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There is a lot more in that issue that just this paper, solid state LVA, other switch articles etc. looks like some may even be good! I got about 20-30 that i want to scan and i expect at least 5 or so will be detailed reading. Big llink to the above article below. You can’t download without a subscription. Can’t wait for open access everywhere (My institute has a subscription).

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6152158&contentType=Journals+&+Magazines&sortType;=asc_p_Sequence&filter=AND(p_IS_Number:6324463)

[delt0r]

Not quite the reply you want(not from LPP). But having done some HV work previously I can comment on the general issues of arcing. Basically any HV things tend to have some issues because insulating is really harder than it looks. Furthermore insulation degrades over time. Expensive HV cables are not rated for very long. There are a lot of physical process that matter at this level. Not all well understood and most highly stochastic. It only takes one electron to get enough energy to knock off more electrons… and now you have a lot of current and heat where you really don’t want it.

Now add the pulse nature and high currents that a DPF has. This further compound problems quite considerably. The biggest issue i would guess is the high stresses that the magnetic fields would place on everything. This means each pulse there are strong forces trying push everything apart, and no matter how strong everything is, things will flex a little. This can then compromise insulation by cause physical damage or by simply providing somewhere to seed a discharge.

A lot of HV equipment has arcing issues. The trick is to not let it destroy the device.

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If the public believes Hollywood then i don’t think any amount of fliers are going to fix it. To give an idea of how much fuel there is, even in ITER the total amount is about 1 gram, or about 10lt of fuel in a gas state.

Contrary to popular belief there are no neutron bombs. They where proposed but never built. The idea was that the neutrons would be the primary kill mechanism. All bombs so far are optimized for yield, not neutron radiation. Even with the large neutron pulse (and subsequent activation of the surroundings), hydrogen bombs are far less dirty than pure fission weapons of the same yield.

For the Tsar bomb, which in its design configuration was a 50MT bomb. Half of that was from fast neutron induced fission of the 238U tamper/case. This was replaced with lead because of the large amounts of fallout you get with fission. The yield of the tested bomb was 25MT.

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Yes, soda cans, thick ones (5mm IIRC). Its was driven by a rather large pulse generator that produces say a pulse per week IIRC. Basically the liner is imploded with a z-pinch. I want to try imploding a liquid metal liner with a z-pinch. A really think one, ie high aspect ratio where most of the compression is from momentum.

As for the “hard to make work”. See the thread on reliable high current, high voltage switches for 10Hz operation. There are none!

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I can’t see 10s or even 100ns rise times on a 400kV primary transformer. That is their issue. 50Hz transformers at the 250kV range are horrendously expensive. Can see a 400kV high frequency one being much cheaper.

In a LVA design you don’t need to worry about 1 or 2 switches per unit failing if designed right. Also they are solid state, so should have very long life times if rated correctly. Its often better to spend a lot up front to prevent downtime.

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LVA is a LTD. Same thing different name. Matching does not seem hard. They can infact match to more or less all sorts of different loads as well as anything else can. Pulse times from micro seconds to ns are also fairly typical. They however are not that cheap. The ferrite tends to be the bulk of the cost. More so if you go for metglas. However it does offer a way to add smaller current and voltage modules that could use solid state switching to more or less the MA levels and MV levels (add a transmission line transformer for more design flexibility too). For a commercial operation the extra capitol cost could well be justified.

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Rail guns and emag guns for next gen tanks are driving compulsator work. Self excited, something on the order or MA is achievable. Heating is an issue. IEEE is where i have found the literature. Don’t want to sound too harsh, but a patent on inductive energy storage for a arc is ridiculous.

Energy density is not really the problem, but switches are and physically large caps means its hard to keep inductance down without going to a 2 stage design or whatever.

Personally I see a commercial plant going for LVA, since they can be designed to add in both voltage and current.

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You seem to be having a completely different conversation. POS are crap…which is why i keep saying IF you have a opening switch that we currently DON’T have. Of course it can’t work now…THAT is what i said like every time. I also said the current would be a challenge without superconductors.

But a compulsator with some magic solid state switch it would really work without superconductors. With potentially higher energy density than caps. Even higher than fast water caps.

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As i said, magnetic storage could be something to consider *if* you have a fast opening switch with high stand off. Which we *don’t* have. Magnetics can be fast if the opening switch is fast which also implies high voltages.

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Well no i can’t *because* there are no fast opening switches. In small scale well yea, every switch mode power supply uses inductors and the main energy store which makes them far more compact than a transformer/ripple cap combination. But the physics is straight forward and power density is pretty good compared to caps. Current at the MA level is a little more challenging without superconductors. But then MA is not trivial with caps either.

But if you can get a solid state switch with high current and high standoff. There is a strong case to use magnetic storage rather than caps.

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If you could get a fast opening switch with larger than 40kV standoff, we would all be using magnetic energy storage. You don’t even need superconductors. At 1T you can store 400kJ per m^3 which is *easy* (this is without magnetic materials). With materials you get much higher densities. It would be like a switched mode power supply on steroids. You can get high voltages easily and high currents with some effort.

Catch is opening switches like this just don’t exist. If we move to solid state, say diamond or SiC switches that don’t just np junctions (avoids the voltage drop problem), then perhaps something could be developed.

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