An insulator from the voltage doubler stack of the Philips Million-Volt Accelerator, installed at the Cavendish Laboratory, Cambridge, in 1937. Each insulator contains a capacitor that acts as a store of electrical discharge. The fins round the outside increase the surface distance between the ends of the unit to prevent sparks jumping from one end to the other. The stack generates the electric field used to accelerate particles such as protons and electrons during experiments using the accelerator.
© Science Museum / Science & Society Picture Library