million electron volts

Two years ago, Safdi and his colleagues put the best upper limit on the mass of the QCD axion at about 16 million electron volts, or about 32 times less than the mass of the electron.

Although that amount of energy is miniscule by everyday standards, the increase occurred as the electrons traveled only three one-hundredths of a millimeter—equivalent to them gaining about 30 million electron volts over the course of a meter.

She estimates that 1,000 stages could fit on a chip a couple of centimeters in length and imbue electrons with a million electron volts’ worth of energy, allowing them to travel at about 94 percent of the speed of light.

Radium emitted alpha particles at a meager 7.6 million electron volts and beta rays—that is, electrons—at only 3 million volts.

Bethe had not been wrong about this obstacle, merely premature; but if the cyclotron were to move beyond 30 million electron volts, the issue had to be faced now.