Mass spectrometers comprising accelerator devices

A time of flight mass spectrometer comprising:

• an acceleration electrode;
• a detector;
• a flight region for ions to travel through between the acceleration electrode and the detector;
• and
• control means arranged and adapted to:
• accelerate ions into the flight region by applying a voltage pulse to the acceleration electrode;
• maintain a potential profile along the flight region such that, in use, ions travel towards the detector, wherein ions having a range of different mass to charge ratios are passed into the flight region and separate spatially according to mass to charge ratio as the ions travel towards the detector;
• and
• change the potential at which a first length of the flight region is maintained from a first potential to a second potential whilst at least some ions are travelling within said first length of the flight region, the changed potential providing a first potential difference at an exit of said length of the flight region, whereby said at least some ions are accelerated through the potential difference as the ions leave said length of the flight region so as to arrive at the detector with increased kinetic energy so as to increase an ion detection efficiency of these ions.