NIF Tour

• Yes, this is embarrassingly overblown, but it gives you a pretty good overview of what NIF looks like and does.
• NIF can deliver 2 MJ of UV light (351 nm wavelength) to a 1 mm spot in 3 ns.
• NIF is more precise than any other high power laser. Imagine if the SLS rocket were also the nimblest stunt plane.

• Again overblown, but NIF shots really are exciting.
• The laser cost about \$4 billion, and about \$350 million per year to operate.
• NIF shot rate now about 400 per year, so a little less than \$1 million per shot.
• About 400 PhD scientists and engineers work at NIF, plus another 500 technicians. (Wild guess, may be somewhat high.)

• Above: standing atop one of 48 main amplifier bundles.
• Right: target chamber composite with several floors removed so you can see more of it than in real life.

SLS engines ~100 GW at launch

NIF ignition shot ~500 TW

• Total world electricity use 3 TW (US 500 GW)
• NIF target $6\!\times\!10^7$ K (SLS exhaust $6\!\times\!10^3$ K)
• "Stars" in background are neutrons hitting camera!

Ignition target before its cryogenic shroud closes. It takes a day or two to grow the solid hydrogen fuel layer inside the capsule before it can be shot.

A bare cryogenic hohlraum target. The silicon arms conduct heat away so the capsule inside can be cooled below 20 K to freeze a layer of DT fuel inside the capsule.

HDC (aka diamond) ignition capsule. The barely visible hair at the top is the hollow glass tube used to fill the capsule with deuterium-tritium fusion fuel.

Cryogenic hohlraum. Wires are for temperature sensors and the heater coils (black bands above and below center) needed to grow a spherical hydrogen ice layer inside the capsule.

Target before a shot with shroud slightly open. Note copper tube and block holding slicon arms.

After a shot with shroud fully retracted. The copper tube split open and folded back around the base of the target positioner. Note the wires dangling from the block that held the silicon arms.

Using simulations to compare two different hohlraum designs.

The "hohlraum" is the hollow gold case containing the capsule - in simple terms it is a 1 cm tall oven. The laser beams enter the top and bottom of the hohlraum through laser entrance holes (LEH), heating the interior to $3\times 10^6$ K in under 10 ns. This causes the outer layers of the capsule to explode, imploding the fuel inside it.

Higher resolution simulations of the capsule only guide interpretations of what instruments record during an actual experiment. There are too many unknowns for these models to actually describe a real implosion, but without them we would have no idea what we were looking at.

X-ray framing cameras make movies of NIF implosions - like the core of an imploded ignition capsule near "bang time" (BT) below.

Dozens of diagnostic instruments measure light, X-rays, neutrons, and other products from each target shot.