Aboriginal Science Fiction, Issues 57–58 — page 54: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

approach? Only further experi- ments will tell. Z-Machine | In the conventional ITER type , reactor, the bulk of the machine consists of the monstrous magnets and coils that generate the electric and magnetic fields that hold the million-degree plasma in the reac- tor. Is there another way to con- - fine the plasma, a way that does not require tons and tons of hard- ware? Well, it turns out that there is. If you take an ordinary wire, any wire will do, and pass a cur- rent through it, you will generate a magnetic field around that wire. Is there a way to exploit that fact in the quest of a fusion reac- tor? 2 You bet there is. Researchers at Sandia National Laboratory in Albuquerque, New Mexico, are using that simple bit of physics to build what they have called the Z- machine. Imagine if you will a Christmas ornament, a standard glass sphere. Now imagine that you use very thin metal wires and run them from the top of the Christmas ornament to the bot- tom, making sure that the wires hug the Christmas ornament. Then get rid of the Christmas ornament. What you are left with is an array of thin wires — some- thing that looks like the longitude lines on a globe. Well, if you pass a big jolt of current through them very quickly (this is similar in con- cept to the NIF laser, in which huge power levels are reached by compressing the laser pulse to really short periods of time), you can dump a huge amount of power into these wires. In the Z-machine, so much power is dumped that the wires vaporize and turn into a plasma. However, just before they vaporize, the current being sent through them generates a huge magnetic field. Well, all this is happening so fast that the magnetic field is still present when the wires vaporize, and this magnetic field compress- es all the ions that have been gen- erated by the vaporizing wires. This is sort of like lifting yourself up by your own bootstraps. Using this approach, the Z-machine has 54 ____ Aboriginal Science Fiction— Summer 1998 Corlmicloctaktst?coim produced about 20% of the energy, 40% of the power, and 50% of the temperature required for nuclear fusion to produce more energy than it consumes. The Sandia team is now looking for $1 billion or so from the Department of Energy to build a bigger version, the X-1, which just may be able to produce more power than it con- sumes. Colliding Beam Fusion So far, all these approaches, no matter how varied they are, rely on the fusing of deuterium and tri- tium, which produces an alpha particle and neutrons. Part of what makes all these fusion approaches difficult in terms of building the type of machine one would need to install in a power generating plant is that you need to extract the energy out of the neutrons, heating up something like water, and then using the steam to turn a turbine. It’s very difficult to stop an energetic neu- tron. You need steel that is meters thick. Now, if you could come up with a fuel mix that did not generate neutrons, but only charged parti- cles, those which could be cap- tured and manipulated by electric and magnetic fields, then you wouldn’t need all that shielding to stop the neutrons. In addition, if you have a charged particle, by definition you have a source of electrical current. The current running through any power cord is nothing more than moving electrons, where an elec- tron is just a particle that has a negative charge. Any charged par- ticle, whether positively or nega- tively charged, if it is moved, can be viewed as a current. Current is nothing more than moving charge. So, if your fusion reaction generat- ed nothing but charged particles, these could be grabbed by magnet- ic and electric fields, and the ener- gy of those particles would move them along in those fields. Moving charges mean current. This would be a much more direct approach to generating power, cutting out all that extra business of neutron- stopping, shielding, and convert- ing water into steam and using the steam to turn turbines in order to generate electricity. Well, it so happens that if you run a fuel which consists. of pro- tons and boron, they will fuse to produce only alpha particles, which are charged. Using this fuel mixture cuts out all the middle- man steps to energy production, making it a much more efficient approach. But as we all know, there is no such thing as a -free lunch. If you put this fuel in an ITER or NIF-type reactor, for fusion to take place, the tempera- tures must be even higher than those required for a more typical deuterium-tritium reaction. This means you need to put in more power to start the fusion reaction, and as a result, you will need to generate more fusion power before you reach the break-even point. But everything is a trade-off, since the electricity you eventually pro- duce is produced much more effi- ciently. Neutron Generator All the approaches described here, even the muonic-based cold fusion approach, still require that you get the atoms pretty hot in order to make them fuse. Is there some way in which you can elimi- nate all this heating business? There is. All these systems heat in order to get the ions in the plasma moving really fast. There is, however, another way to get ions moving really fast. If you take an ion (a positively charged deuterium ion in this case) and drop it in the vicinity of a metal plate that is held at a neg- ative voltage, the ion will acceler- ate toward the plate. Remember the old adage that opposites attract. Well, the larger the nega- tive voltage, the faster the ion accelerates. Eventually the ion will strike the negatively charged plate, and the game is over. However, imagine that instead of a plate, you have a metal ball, one with a lot of holes punched in it — in fact, a ball which is much more holes than actual ball. If you place the negative charge on it, as the ion is accelerated toward it, in most cases it passes right through the holes and rushes into the cen-