The Zero Hour

He had received his Ph.D. in nuclear physics at CalTech and was well versed in the strengths and weaknesses of the microwave sniffer. For instance, they now knew how strong the emissions were-that was on the receiver’s readout-but without opening the door to the basement they could not know how far they were from the bomb. That meant they couldn’t map the microwave field, couldn’t learn how close they could safely get to the bomb before it would detonate.

Was there a dead zone? They couldn’t even tell that. Typically, a microwave sensor employs a Doppler shift, which means that the signal creates a constant pattern of microwave energy. The sensor looks for any change in the reflected pattern of that energy. A change occurs when an object within the sensor’s field moves. If you are standing absolutely still in the field, nothing will happen.

Of course, some motion had to be tolerable: what if the air-conditioning caused a curtain near the bomb to ripple? So the detector calculated the amplitude of change over time. Any change that was strong-or long in duration-would set it off, the exact definition of “strong” or “long” having been preset in the detector.

Also, as Payne knew, you could beat a microwave sensor if you knew how. There were ways. If you approached the sensor very slowly, you might not set it off.

But if you allowed your arms to swing at your sides even slightly, you’d probably get nailed, because your arms would be moving toward and away from the sensor at a greater rate of speed, a greater rate of change, than the rest of your body.

That wasn’t even a possibility now, however. Without seeing the bomb and being able to estimate its distance from where they were standing, they certainly could not risk approaching it.

And here was the bitch of it. How could you kill a bomb when you didn’t even know where it was?

CHAPTER NINETY-FIVE

Within fifteen minutes, the line of evacuees from the Network building dwindled and then stopped. Another announcement was made over the PA system, but ten minutes later no one had emerged.

None of the workers who had filed out of the building bore a remote resemblance to Baumann.

***

Inside the building, Sarah made her way up the stairwell. She had searched the first four floors, but no Baumann. And no Jared.

On the fifth floor, she walked silently down the empty corridor, checking office after office.

***

Dr. Payne made a swift calculation.

They were detecting microwave energy, but did that really mean they couldn’t move? He knew that the range of detection is always greater than the range of function-that is, they could “see” the microwave emitter, but the emitter couldn’t necessarily see them. There’s always a threshold of acceptable leakage, just as a microwave oven might leak microwaves, but people don’t necessarily get cooked standing in front of it.

Payne had examined the fusing system. He knew now how much energy it needed to set off the bomb. The more he repeated his mental calculations, the more sure he was that the amount of microwave energy leaking under the steel door was not enough, if reflected backward, to trigger the detector.

They were safe where they were. They could move.

***

“All right,” Dr. Payne said. “The safe line is on the other side of the door. There’s some stray microwave leakage, but we’re safe as long as we stay on this side. Everyone, back off from the door. You, Grant, and you, O’Hara”-he pointed at the DOE scientist who had lost it-“get out of here. I don’t want to see you again.”

On this side of the door, on this side of the safe line, they could move. The microwave sensor, he now realized, would detect motion on the other side of the door only.

This was good. This gave them considerably more room to maneuver.

This also meant they could remotely “look” at the bomb using a technology that remains to this day highly classified by the U.S. government. They used a device called a neutron backscatter, which emits a stream of neutrons at a very specific energy level. The stream is fired at the target, and then the backscatter measures the rate at which the neutrons come back at it-that is, the extent to which the neutrons are absorbed.

The neutron backscatter has the ability to penetrate metal liners and walls, so the steel door was not an obstacle. Using the same physical principle employed in an HED-a hydrogenous explosives detector-it looks for hydrogen. The neutron backscatter they were using was unusually powerful. Payne flipped the switch, checked the readout.

“Well, there’s explosive material there,” Dr. Payne muttered to Suarez. “A shitload of it, from what I can tell.”

“Now what do we do?” Suarez asked.

Dr. Payne did not reply; the truth was, he had no idea. He was winging it; in times like this you always had to wing it and trust your instincts.

“All right,” he said at last. “I want the generator moved out here.”

“You want to do what?” asked Suarez.

“Like I said,” Dr. Payne said. “The generator.”

“You want to do the EMP? Jesus-”