"Now, around the beryllium is a cylinder of tungsten-rhenium, which we need for its density. We will purchase twelve kilograms in powder form, which we will sinter into cylindrical segments. You know sintering? That is heating it just hot enough to form. Melting and casting is too difficult, and not necessary for our purposes. Around that goes the explosive-lens assembly. And this is just the primary, Ghosn, not even a quarter of our total energy budget."

"And the precision required.."

"Exactly. Think of this as the world's largest ring or necklace. What we produce must be as finely finished as the most beautiful piece of jewelry you have ever seen - or perhaps a precision optical instrument."

"The tungsten-rhenium?"

"Available from any major electrical concern. It's used in special filaments for vacuum tubes, numerous other applications, and it's far easier to work than pure tungsten."

"Beryllium - oh, yes, it's used in gyroscopes and other instruments thirty kilograms."

"Twenty-five yes, get thirty. You have no idea how lucky we are."

"How so?"

"The Israeli plutonium is gallium-stabilized. Plutonium has four phase-transformations below melting point, and has the curious habit, in certain temperature regimes, of changing its density by a factor of over twenty percent. It is a multi-state metal."

"In other words, a sub-critical mass can -"

"Exactly." Fromm said. "What appears to be a sub-critical mass can under certain circumstances convert itself into criticality. It will not explode, but the gamma-and neutron-flux would be lethal within a radius of oh, anywhere from ten to thirty meters depending on circumstances. That was discovered during the Manhattan Project. They were - no, not lucky. They were brilliant scientists, and as soon as they had a gram or so of plutonium, it was decided to investigate its properties. Had they waited, or simply assumed that they knew more than they did - well "

"I had no idea," Ghosn admitted. Merciful God

"Not everything is in books, my young friend, or should I say, not all the books have all the information. In any case, with the addition of gallium, the plutonium is a stable mass. It is actually quite safe to work, as long as we take the proper precautions."

"So we start by machining out stainless-steel blanks to these specifications, then make our casting-molds - investment casting, of course."

Fromm nodded. "Correct. Very good, mein funge."

"Then when the casting is done, we will machine the bomb material I see. Well, we seem to have good machinists. They'd 'drafted' - that was the term they used - ten men, all Palestinians, from local optical shops, and trained them on the use of the machine tools. The tools were all that Fromm had said they were. Two years earlier, they'd been totally state-of-the-art, identical to the equipment used in the American U-bomb fabrication plant at Oak Ridge, Tennessee. Tolerances were measured by laser interferometry, and the rotating tool heads were computer-controlled in three dimensions through five axes of movement. Instructions were passed to the computers via touch-screens. The design itself had been done on a mini-computer and drawn out on an expensive drafting machine. Ghosn and Fromm brought the machinists in and set them to work on their first task, making the stainless steel blank for the plutonium primary that would ignite the thermo-nuclear fire.