Mass spectrometer

I found this mass spectrometer in a museum in Manchester. It works by turning the atoms in a compound into ions and then bending them with a magnetic field. They all experience the same magnetic field but the heavier elements are not bent as much so they are detected further from the centre of the circle. One clever bit is the use of crossed electric and magnetic fields on the way in which only allow particles of a particular speed to go straight on through a slot. It means that the speed in the main detector is also a control variable. Unfortunately we can't assume that the ions of one element all have the same charge. Some will be +1, some +2 etc. But you can make allowances for that in the analysis. Read the notice in the photograph to see what they are used for.