Crystal monochromator at Diamond Light Source

You can't see what is happening inside the machine but this is on the other side of the wall to the magnets shown on previous posts. The electrons have been pulled round the ring by the magnet but the X-ray beam carries on in a straight line. Scientists usually want to choose a single wavelength but the X-rays will cover a range of wavelengths. So they are shone at parallel crystals. The planes of atoms act like the slits in a diffraction grating so that the spread of the beam depends on the wavelengths present. With visible light diffraction, I have been using n x lambda = d x sin theta. Different wavelengths are found at different angles theta. So you choose your angle to get your wavelength. William Lawrence Bragg did the maths for X-ray diffraction and put a 2 into a version of the equation I have quoted. His dad was born about 2 miles outside Wigton and the two of them shared the Nobel Prize for Physics for work on this topic.