Splitterra

Splitterra, a shirt-sleeved accelerator builder, holds a burst of orange fire between his hands.

The Physics

In April 1932 at the Cavendish Laboratory, John Cockcroft and Ernest Walton fired protons from a high-voltage accelerator at lithium. Scintillation screens flashed with pairs of alpha particles flying apart (Proc. R. Soc. A 137, 229, 1932). It was the first nucleus split by artificially accelerated particles, and the energy released matched E = mc².

p + ⁷Li → 2α + 17.3 MeV

• p: proton
• ⁷Li: lithium-7 nucleus
• α: alpha particle, a helium-4 nucleus

Their voltage multiplier needed only a few hundred kilovolts, because quantum tunnelling lets protons through the Coulomb barrier. They shared the 1951 Nobel Prize.

Honest caveat: The 17.3 MeV is shared between the two alphas; the line on the sticker omits it.

On the sticker

Splitterra holds a bright orange burst of energy between his hands. Printed text: SPLITTERRA with the line p + Li → 2α. Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.