Time of flight mass analyser with spatial focussing

A Time of Flight mass analyser comprising:

• at least one ion mirror for reflecting ions;
• an ion detector arranged for detecting the reflected ions;
• a first pulsed ion accelerator for accelerating an ion packet in a first dimension (Y-dimension) towards the ion detector so that the ion packet spatially converges in the first dimension as it travels to the detector;
• and
• a pulsed orthogonal accelerator for orthogonally accelerating the ion packet in a second, orthogonal dimension (X-dimension) into one of said at least one ion mirrors;
• wherein the first ion accelerator is configured to pulse the ion packet out having a first length in the first dimension (Y-dimension), wherein the orthogonal accelerator is configured to pulse the ion packet out having a second length in the first dimension (Y-dimension), and wherein the detector is arranged such that the ion packet has a third length in the first dimension (Y-dimension) when it impacts the detector, wherein the third length is shorter than the first length and the second length.