[andrewmdodson]

XRAM pulse generators…?

[andrewmdodson]

I was thinking about the capabilities of the electron beam forming system deployed at NASA via wire feed and electron beam melting (EB) and then in some commercial systems such as the arcam.com powder feed EBM.

A structure of multiple metals might be created. The thermal conductivity and softness of the BeCu alloy is attractive. It has been used to coat titanium valves, so perhaps a composite structure composed of a titanium skeleton with BeCu filled around it can be laid down via an EBM method. Thermal simulations could determine proper geometries needed…

Thoughts?

EDIT:

at the bottom of this page it is mentioned that EBM can be used to melt CuW onto a copper carrier (in our case BeCu). A tri-layer cathode, titanium skeleton, BeCu mass, and CuW surface layer… http://www.modison.com/copper_tungsten.html

How much heat must be conducted out of a reactor cathode (or anode) per shot?

[andrewmdodson]

heck, The actual PDF I wanted to post is over 5 MB… forum limitations!!

[andrewmdodson]

Could someone please send me some test dimensions of a rogowski coil? I would like to run a simulation.

[andrewmdodson]

If you could configure a gas discharge switch to turn off precisely, interrupt the current in many large inductors. Force them into a parallel configuration and obtain very high currents and multiples of your charging current. The series inductors can charge up a large current with a fairly low voltage over a few seconds. This is known as the XRAM current multiplier (the inductive inverse of the MARX voltage multiplier)

A big advantage is inductive energy storage is 10x denser, meaning a much lower cost and smaller total size. I have a gut feeling that the inductive coil might very advantageous to the beam extraction concept. A current choke averages out the energy pulses of the collection coil and the firing system. I cannot say conclusively if this will give a faster current rise time than a capacitive discharge.

Development of a combined opening switch for the project of generator on inductive storages
Abstract

[em]The article proposes a fundamentally new approach to the problem of breaking high currents of 100kA or more. The vacuum discharger and the vacuum interrupter differ significantly in the rate of electric strength recovery, size of electrode erosion and etc. This is due to the difference in the type of the discharge. In the report considered we suggested that to align these values the current I should be closed through the spark gap prior to moving the electrodes of the vacuum interrupter; at this its value is above the initial by ΔI (ΔI-current, ΔI/I0 ~5÷10·10-2). The excess ΔI-current flows through the vacuum interrupter, but in the reverse direction. In the course of moving the electrodes apart, the ΔI-current falls to zero with a time constant t=L/R, where L and R are the inductance of the contour (vacuum interrupter- spark gap) and resistance of the discharge of the discharge gap, respectively. This makes it possible to quickly recover the electric strength of the gap between the contacts, substantially reduce the electrode erosion and significantly decrease the breaking voltage of the ΔI-current. At the final stage the discharge of the countercurrent battery recovers the vacuum strength of the discharge gap. Such method of current breaking allows for the effective interruption of direct currents of high power. The method was developed in terms of the combination current breaker (vacuum interrupter and plasma opening switch). Spark gap is replaced to mobile plasma gap in design of combination opening switch. The article considers -construction of switch; -described of action steps; -energy characteristics of circuit, in the context to progress of conception pulsed generators based on inductive storage.[/em]

[andrewmdodson]

I see a lot of science getting tossed around, cool :]

If someone could draw up a diagram of a geometry I can throw it in CAD real quick and run a finite element simulation to determine flashover. I can try with a few of the different materials proposed as a basis for model properties…

[andrewmdodson]

zapkitty wrote:
Now, will more research be needed on the subject in
the future? Certainly. Operational FF units will need to
bring the cost of reliable, high-repetition switches
down quite a bit… would such a longer-term
undertaking be more in line with what you feel you can
do?

I have to do something for a PhD. I am working on a thorium reactor paper as well. I would think it could be feasible to contribute in a small way if there is some engineering to do. I can perhaps do a simulation of the power electronics drive that would run off a pulsed power source such as this at a 1-200 Hz rate and deliver energy to the local grid… eh? Im not sure now, I just knew there was an issue with the switches recently. Would love to learn what your solution is.

What about the bigger picture in the electronics drives aspect? What will the interfaces look like for the photoelectric onion shell device or the beam transformer? Anything?

[andrewmdodson]

zapkitty wrote: … and wouldn’t the new switches, from Raytheon I believe, be tested by using them in LPPX-1?

Does it make sense to think of testing switching devices seperate from the reactor proper? I would hope it feasible to say we can fabricate a small vaccuum chamber with electrodes as a dummy load?

[andrewmdodson]

Warwick wrote: This may be an ignorant question, Andrew, but which of the 5 headings are you intending that this should relate to?

I believe the 4th item, non-inductive current drive would be the most appropriate in terms of what the electrical engineering department would contribute.

What are the current needs of the LPPx? What parts of the puzzle are as of yet still completely theoretical? Where does an engineer fit in with all these physics geniuses? :p

[andrewmdodson]

I would be interested in doing a study of the properties of gas discharge switches operating in parallel. I do not know the details of the Raytheon devices. Can someone please get me up to speed on this?

I am an electrical engineer and I know that pulsed fusion needs pulsed power switches. How would you recommend I best contribute? My professor is willing to help me with the writing of a grant and the university already has the required credentials to sign up for this program.

As per the attached paper, a laser triggered Surface-Discharge switch seems most appropriate for this application. What would an appropriate research into the operating characteristic of these devices need to investigate?

I could imagine using a hot cathode to provide an electron beam that is swept from the anode to the cathode of the discharge switch instead of a laser to induce a conductive channel.

Honestly I am just a systems engineer but I am very motivated about the focus fusion and want to contribute. Please help me make your dream my dream. I am wide open to suggestions.

Attached files

GasDischargeJitter.pdf (214 B) 

[andrewmdodson]

https://focusfusion.org/index.php/forums/viewthread/1212/

please reference my post here. I would like to help with a specific grant application.

[andrewmdodson]

details attached.

I am thinking we could fund the testing of a set of the new switches. I do converter design and have looked at some pulse shaping circuits and other methods of generating high power electricity.

Can someone help me out with an idea, some documentation, help budget it out, and agree to visit the lab? Are there concepts/drawings available of parts you would like manufactured and tested?

Attached files

DE-FOA-0000879.pdf (249 B) 

[andrewmdodson]

A spallation source uses protons to knock neutrons out of heavy metal atoms. Liquid mercury is used as it doesnt suffer damage to a solid structure, although I am curious as to what the mercury is gradually converted into.

Consider that the DPF produces alpha particles of a high energy… Does the concept of alpha particle spallation make sense? I know we use charged particles because we can guide them (as opposed to the willy nilly go everywhere neutral neutrons) into a spallation target, resulting in neutrons traveling in roughly the same direction.

[andrewmdodson]

http://www.evincetechnology.com/tech_overview.html

possibility of diamond switches evolving soon into something useful for the focus fusion project?

[andrewmdodson]

My understanding is that the switch only has to close extremely rapidly… the capacitor bank discharges completely into the reactor, expending functionally all the current and then the system resets for the next pulse…

Why does there need to be reverse conducting? Are you using the same electrical pathway to recharge the cap bank?! I thought that no power had yet been extracted from the DPF?

I see what you mean about pulsed power technology not being far along enough… However, considering that SiC is giving rise times 2-3 orders of magnitude over Si, I think that you might actually be somewhat near your goal in about 5 years if you could apply that principle linearly to this pulse thyristor http://www.dynexsemi.com/assets/Pulsed_Power_Thyristors/Datasheets/DNX_PT85QWx45.pdf

But fusion will not wait for a bunch of slacker semiconductor physicists to catch up!! ONWARD!

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