The last echoes of the Sphinx

By Julien Geffray
May 21, 2007

Or how, over the past year, the Americans have gone full steam ahead while the French have put on the brakes.

Let’s briefly revisit the past year: in March 2006, a groundbreaking discovery was announced by Sandia Laboratories in the United States: the Z-machine had accidentally generated temperatures of 3.7 billion degrees (see the original press release in English (archive from 17/10/2011)). This was an unprecedentedly high temperature—100 times hotter than the Sun’s core, seven times hotter than the core of a hydrogen bomb, and four times higher than theoretical predictions, with no real explanation. At such temperatures, a new path opened up toward controlled nuclear fusion—not only for hydrogen isotopes as traditionally envisioned in successive tokamak projects like ITER or Megajoule-class lasers, but also for two entirely new nuclear reactions previously deemed impossible: lithium-hydrogen (requiring at least 500 million degrees) and boron-hydrogen (starting at one billion degrees). These two specific nuclear reactions produce virtually no radioactivity—aside from a few minor, negligible side reactions—meaning they could lead to power plants that are both extremely powerful and completely pollution-free, using elements that are abundant and harmless on Earth. In short, this could be the long-awaited energy solution for our planet plagued by rampant pollution.

Throughout 2006, Jean-Pierre Petit described the Z-machine and its potential in layman’s terms:

The existence of a comparable French machine—albeit less powerful—was also highlighted: the ECF at the Gramat Military Experimental Center (CEG), located in the Lot region. ECF stands for “Expérience de Compression de Flux”; in practice, the machine is nicknamed Sphinx.

Numerous attempts were made to get national media to cover this topic and to encourage politicians to take interest, but with little success (an article in the webzine Futura-Sciences (archive from 27/07/2008) and just brief mentions in Science & Vie and Sciences et Avenir). A popular article posted online on the forum Agoravox quickly disappeared. Contacts with politicians were attempted. A top-level scientist in Russia responsible for nuclear fusion issues even agreed to support JPP and a colleague—a former bomb expert—by writing a signed letter to be personally delivered, explaining the importance of this research and even suggesting Franco-Russian cooperation in this field! But who in France could receive such a letter? There’s no scientific official close to policymakers willing or able to listen to such arguments.

Regrettably, these efforts went nowhere for two main reasons:

Research on fusion via “z-pinch” or “magnetic constriction,” as it’s called in French, is viewed—especially regarding budget allocation—as directly competing with the ITER project, a very different approach already underway in France. Moreover, there are too few French experts in magnetic constriction to make their voices heard; disheartened, many have since moved to the U.S. to work on Sandia’s Z-machine.
Such research is “potentially proliferative.” In other words, it could lead to the creation of next-generation nuclear weapons. In such a scenario, the detonation of a hydrogen bomb wouldn’t require a conventional atomic bomb as an initiator—which is hard to produce. Instead, a compact system derived from the Z-machine could be built, much easier for any country to develop and virtually impossible to monitor, since it relies on “mere” high-power electronics. The infamous uranium enrichment step—which causes major geopolitical problems yet allows some control over proliferation—would then become unnecessary.

The obvious goal behind all this activity was to allow civilian researchers access to Sphinx, given that France’s Z-machine is reserved exclusively for military engineers. Currently, its capacity of 2.5 to 5 million amps can’t match the American Z-machine, which delivers 18 million amps. Yet such a device can be upgraded relatively easily. Sandia’s Z-machine was actually dismantled in September 2006 for a renovation that would boost its capabilities by 50%. The ZR program (“Z Refurbished”) is expected to be fully operational by summer 2007, delivering 27 million amps in pulses lasting just 100 nanoseconds. We await the temperatures this will achieve—they should rise further still. As we’ll see later, the Americans won’t stop there: they’ve already set their sights on reaching 60 million amps.

Unofficially, a few months ago French military officials weren’t quite sure what stance to adopt. On one hand, this research seemed highly promising; however, CEG lacked researchers capable of exploring this new field at a fundamental level. On the other hand, the DGA wanted full control over such research, possibly imposing defense secrecy if anything significant emerged. Similar concerns exist regarding Sandia Labs, which are effectively run by the U.S. Defense Department and Army (funding comes from NNSA, the National Nuclear Security Administration). Hence the importance of conducting independent research elsewhere. Dilemma: how to open the Gramat Military Center to civilians?

The answer—disheartening for some, predictable for others—was given by journalist Matthieu Quiret in the May 16, 2007 edition of the economic daily Les Échos, available online at:
http://www.lesechos.fr/info/metiers/4576329.htm

We reproduce the relevant excerpt here (the interesting part is in red):

Les Échos, May 16, 2007

Nuclear Expertise

France’s Z-machine shuns energy applications

A tiny “Sphinx”

Deep in the Quercy region, at the Gramat Research Center (CEG), the DGA has been operating a small French Z-machine (2.5 million amps) nicknamed “Sphinx” for several years now. Like its American counterpart, it’s primarily used to test nuclear warhead durability. Unlike it, though, it won’t see any civilian experiments. Years ago, Gramat researchers tried to persuade their military superiors to diversify their studies, but to no avail. When questioned by Les Échos, the notoriously “reserved” CEG claims it has no energy-related projects at present. This reluctance worries specialists in magnetic constriction. “France’s expertise in high-power electrical engineering is at risk,” warns one of them.

In the UK, a similar machine, Imperial College’s Magpie (1.4 million amps), actively researches magnetic constriction, partly funded by the U.S. Though not powerful enough to meet the Z-machine’s nuclear goals, it helps Americans advance their own research on magnetic constriction. The Russians, too, seem poised to invest in this field.

So now we know exactly what to expect. Despite France’s expertise and Russian assistance, the military has decided: no civilian research on magnetic constriction fusion will occur in France.

Meanwhile, where do the Americans stand—and where are they headed? In the same issue of Les Échos, contrasting sharply with the blockage of French research, controlled hydrogen fusion via the Z-machine is extensively explained in another article titled “Nuclear: America’s Z-machine challenges ITER”, which you can read at:
http://www.lesechos.fr/info/metiers/4576219.htm

We reproduce the illustration from this article below:

Hydrogen fusion in the Z-machine

How America’s Z-machine fuses hydrogen isotopes (deuterium-deuterium reaction producing moderately energetic neutrons at 2.45 MeV)

This is the well-known indirect technique of the “hohlraum” or “X-ray furnace,” which compresses and heats a capsule containing hydrogen isotopes until fusion occurs, using special foam and a tungsten wire cage. The experiment was first successfully conducted on April 7, 2003, on the Z-machine (press release (archive from 04/03/2012)). Direct ultra-high-temperature triggering of clean nuclear reactions (lithium-hydrogen or boron-hydrogen) via recent stainless-steel wire cage technology (3.7 billion degrees end of 2005) hasn’t yet been mentioned. Still, the concept of magnetic constriction fusion is slowly gaining traction in French media.

Until now (1996–2006), Sandia’s Z-machine looked like this:

Z-machine – cross-sectional diagram

Cross-section view of the Z-machine. Note the size of the brown basin and the length of the blue water lines.

Dimensions: 33 meters. When current is switched on, electric arcs spread across the surface of the massive oil-and-water insulated basin:

Z-machine – electric arcs

Short circuits occurring on the Z-machine’s surface between exposed metal parts

“Water lines” help increase power output by compressing the initial electrical impulse (lasting mere microseconds) generated by peripheral Marx generators, so that the final pulse delivered to the wire cage lasts just 100 nanoseconds.

Question: How to boost power output? Several options exist:

One solution came mechanically with ZR in 2007: same method, improved components. For instance, there are still 36 Marx generators, identical to earlier ones, but with capacitors storing twice as much energy. The single 4-joule gas laser trigger shared by all 36 switches is replaced by 36 individual laser triggers. Water-insulated transmission lines are now vertical and triple-plated (previously horizontal double-plated), taking up less space and generating fewer bubbles, etc.

Nothing prevents “stacking all these elements” later on. Doubling the basin height would mechanically yield 54 million amps in a “double ZR” setup.

French specialist Mathias Bavay, who emigrated to Sandia after failing to secure funding in France for Gramat, devised a Z-machine capable of instantly delivering 60 million amps in 100 nanoseconds via a clever self-compressing magnetic flux mechanism using two coaxial liners—no explosives required (for details, see his thesis explained in lay terms).

Jean-Pierre Petit, for his part, suggested replacing the bulky “Marx generators + conductive lines + basin” assembly with an explosive-driven flux compression generator—an ultra-compact device capable of generating 100 million amps, invented by Andrei Sakharov in the 1950s (MK-2 generator) or a more advanced variant (like the faster DEMG disk generator). Russians excel at “high-power pulsed” technologies; see the basics of Russian MHD machines for more info.

The following sketch is purely schematic. It represents a simple “university lab or engineering school” setup aimed at providing a first glimpse into these concepts. Sakharov’s generator, with its solenoid, can produce very high currents, but discharge time is too long. For an ultra-fast explosive-driven generator, look at Russia’s DEMG—incredibly ingenious (see midway down this page).

montage_bis

Schematic setup showing coupling between a Z-machine and a Sakharov generator. Right: Induction MHD generator, a simple solenoid surrounding the target. Bottom: Ultra-fast explosive-driven switch

Yet another promising path toward magnetic constriction fusion within a Z-machine seems to be emerging in the U.S., with Russian backing: the LTD (Linear Transformer Driver) generator, whose rapid progress was proudly announced by Sandia Labs in April 2007. Read about it here:

The Z-machine enhanced by LTD

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