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"They're waiting for you Gordon, in the test chamber."
Black Mesa Scientist[src]

The Anti-Mass Spectrometer is a room-sized piece of equipment located in Sector C's Test Lab C-33/a at the Black Mesa Research Facility used to analyze exotic materials such as Xen crystals. The machine was designed by Dr. Rosenberg.[1]


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Gina Cross seeing Colette Green during the Resonance Cascade under the Anti-Mass Spectrometer Test Lab.

Regular mass spectrometers are used to measure the mass and relative concentration of atoms and molecules, allowing the chemical composition and structure of a substance to be analyzed. This process does not work for exotic matter that has anti-mass (negative mass).

The Anti-Mass Spectrometer works by scanning a sample with oscillating electromagnetic fields and beams of high-energy plasma, agitating the exotic matter of the Xen crystals. This agitation of the Xen crystals results in currents of displacement energy within the crystal, which forms noticeable displacement fields that can be analyzed using advanced sensors developed by the Lambda labs. Xen Crystal samples are brought into the Test Chamber by a lift from the lower levels and held by a cart.

The Black Mesa staff who operate within the spectrometer chamber are jokingly referred to as being "in the barrel." This joke is a reference to the barrel-shaped walls of the chamber and to an old nautical joke.

Despite the high levels of energy used in the experiments (running the spectrometer requires an HEV Suit, and in Half-Life: Blue Shift, the process is shown to place visible strain on the entire facility's power sources), it was a typically safe procedure. The final experiment of the Black Mesa Anti-Mass Spectrometer, combining an unstable sample Xen crystal (GG-3883) and the disabling of certain safety features, caused a Resonance Cascade and the opening event of the Black Mesa incident. The Anti-Mass Spectrometer was heavily damaged during the Resonance Cascade but not destroyed until Black Mesa itself was annihilated by a thermonuclear warhead detonation.

A scaled-down Anti-Mass Spectrometer is seen in Eli Vance's lab, on the chapter Black Mesa East. It is seen analyzing a Xen crystal in what is known as a Rotato.

No detailed descriptions of the Anti-Mass Spectrometer are given in either Half-Life or expansions. Still, it is possible to glean some insights into its operation. It seems that both the spectrometer and the teleportation machines in the Lambda Complex are essentially similar: possessing similar appearances and generating the same unique sound in operation, it appears that the two technologies are related. Based on this similarity, the Lambda complex machine's reliance on a committed nuclear reactor, coupled with the power outages that occur while the experiment takes place (as seen in Half-Life: Blue Shift), suggests that the Anti-Mass Spectrometer requires an immense amount of power to operate.


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