Engineering for pulsed operation

[Tulse]

While I understand how a focus fusion device could produce power in a single shot, I’m not clear how it is to be engineered to do rapid pulsing. The issue I specifically haven’t seen mentioned (although I may have missed it) is how the helium waste will be removed from the reaction chamber after each shot, to avoid poisoning the later shots. As I understand it, the chamber is at near-vacuum, and the intent is to cycle many shots per second — does this mean that the chamber is completely evacuated and refilled after every shot? How is the device to be engineered for continuous pulsed operation?

[Henning]

The helium particles are in fact ejected by the ion beam passing through the coil by the mere fact that they are positively charged and in a big electric/magnetic field. Behind that coil is a chamber which is evacuated. The main chamber contains evaporated decaborane with a pressure of about 10 mbar (7 torr). So the main chamber is always filled with that gas at low pressure compared to our atmosphere. Only a very small portion of the gas is ignited.

The main concern is overheating, which will limit the rate of the pulses, i.e. how fast you can remove waste heat from the anode. Current design proposes a beryllium anode (and also cathode) with helium as coolant, because of the low Z (number of protons in their core). Beryllium and helium are translucent for x-rays.

[Tulse]

I realize the helium ions get ejected through the coil, but the interior of the coil must be open to the main chamber, no? Does the main chamber essentially continually “leak” into the evacuated chamber beyond the coil? And is it simply that the amount of leakage isn’t significant enough to be a problem?

[Henning]

Hmm, I for my part thought the force of the ions passing through the coil would enough to repel any atoms going the other way. If not, add a valve or gate after the coil to minimize leakage.

[Author]

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