Nevada

109

Atomic Testing Museum, Las Vegas, NV

36° 6′ 50.98″ N, 115° 8′ 54.96″ W

History of the Nevada Test Site

From 1951 to 1992, the U.S. (with a little help from the UK) exploded 1,021 nuclear bombs above and below ground outside Las Vegas, Nevada (see Chapter 110). Many of the tests were announced in advance, and the above-ground explosions were visible from Las Vegas, where they became a tourist attraction. Today, the history of the most prolific test site in the U.S. is documented at the Atomic Testing Museum.

Since this is Las Vegas, there’s a multimedia event to compete with the rest of the city’s attractions—the Ground Zero Theater. The visitor is seated inside a mock concrete bunker seven miles from a nuclear explosion. The countdown begins, and the bomb explodes. A blast of air rushes into the bunker and the entire theater shakes.

However, the museum is neither a glorification of nuclear bombs, nor a glitzy tourist attraction. Instead, it’s an informative and intelligent explanation of the Cold War and the chronology of nuclear testing. In addition to many photographs and films of nuclear explosions, the museum has exhibits of equipment recovered from the Nevada Test Site.

There’s a very interesting exhibit concerning photography and filming of nuclear explosions, with dramatic pictures of the first microseconds of nuclear blasts. There’s also a calutron: a device used for separating uranium isotopes by splitting a beam of isotopes by deflecting them using an electromagnet. Different isotopes follow different curving paths based on their weights and can then be collected.

A section on underground testing explains the technology used to bury nuclear bombs, and the after-effects of underground explosions. During the 1950s the explosions were part of popular culture, and there’s a display of period pop-culture items including a book of Atomic Cocktails.

Peaceful uses of atomic energy are also on display, including an atomic rocket engine.

The only part of the museum that’s truly a tourist trap is the shop, which sells everything from finger puppets of Curie, Einstein, Newton, and Darwin to a Miss Atomic Bomb shot glass.

Outside the museum is a weather station that confirms that Las Vegas is hot and dry, but also gives the current background radiation reading in microrems per hour.

Practical Information

The museum’s details are at http://www.atomictestingmuseum.org/. See also Chapter 110 for information on visiting the Nevada Test Site.

Geiger Counters

The Atomic Testing Museum has a large display of radiation-detecting equipment, including Geiger counters. A Geiger counter detects radiation indirectly by detecting ionization of a gas caused by radiation. The same technique was used by Pierre and Marie Curie in their original measurements of the strength of various radioactive sources (see Chapter 15). Visitors can use a Geiger counter to detect the amount of radioactivity from a number of common materials and objects.

A Geiger counter consists of a hollow, gas-filled glass cylinder, called a Geiger-Müller tube, that performs the detection. Inside the tube is an inert gas (such as argon). The interior of the tube is coated with a conducting material, and in the middle there’s a metal needle-like electrode (see Figure 109-1).

Figure 109-1. A Geiger counter

A large voltage (hundreds of volts) is applied between the needle electrode (which becomes positively charged) and the tube interior (which becomes negatively charged). No current flows.

At the end of the tube is a window, typically made of mica. The very thin mica window prevents light (to which the tube would be sensitive) from entering the tube, but lets alpha particles (helium nuclei), beta particles (high-energy electrons), and gamma radiation in.

When radiation enters the tube, it ionizes the gas, resulting in positively charged argon ions and electrons. The large voltage between the electrodes causes the ions and electrons to move rapidly toward the electrodes (the electrons to the anode and the ions to the cathode). As they move, they have enough energy from the electric field to ionize more of the gas. This avalanche of ions and electrons creates a current between the cathode and the anode.

The current is detected by the Geiger counter, which typically emits a clicking sound and counts the number of times ionization has occurred.