Space Focus Time of Flight Mass Spectrometer

A mass spectrometer comprising:

• a Time of Flight mass analyser comprising a source region and an ion detector;
• wherein, in use, ions arriving at said ion detector have a spread of ion arrival times ΔT which is related to an initial spread of positions Δx of said ions within said source region by a polynomial expression of the form ΔT=a0+ai(Δx)T′+a2(Δx)2T″+a3(Δx)3T′″+wherein ai(Δx)T′ is a first order spatial focusing term, a2(Δx)2T″ is a second order spatial focusing term, a3(Δx)3T′″ is a third order spatial focusing term and T is the mean time of flight of ions having a certain mass to charge ratio;
• wherein:
• said Time of Flight mass analyser further comprises a fourth order spatial focusing device which is arranged and adapted to introduce a non-zero fourth order spatial focusing term so that the combined effect of said second and fourth order spatial focusing terms is a reduction in the spread of ion arrival times ΔT.

A method of mass spectrometry comprising:

• providing a Time of Flight mass analyser comprising a source region and an ion detector;
• wherein ions arriving at said ion detector have a spread of ion arrival times ΔT which is related to an initial spread of positions Δx of said ions within said source region by a polynomial expression of the form ΔT=a0+a1(Δx)T′+a2(Δx)2T″+a3(Δx)3T′″+ . . .
• wherein a1(Δx)T′ is a first order spatial focusing term, a2(Δx)2T″ is a second order spatial focusing term, a3(Δx)3T′″ is a third order spatial focusing term and T is the mean time of flight of ions having a certain mass to charge ratio;
• wherein:
• said method further comprises introducing a non-zero fifth order spatial focusing term so that the combined effect of said first, third and fifth order spatial focusing terms is a reduction in the spread of ion arrival times ΔT.

A method of mass spectrometry comprising:

• providing a Time of Flight mass analyser comprising a source region and an ion detector;
• wherein ions arriving at said ion detector have a spread of ion arrival times ΔT which is related to an initial spread of positions Δx of said ions within said source region by a polynomial expression of the form ΔT=a0+a1(Δx)T′+a2(Δx)2T″+a3(Δx)3T′″+ . . .
• wherein a1(Δx)T′ is a first order spatial focusing term, a2(Δx)2T″ is a second order spatial focusing term, a3(Δx)3T′″ is a third order spatial focusing term and T is the mean time of flight of ions having a certain mass to charge ratio;
• wherein:
• said method further comprises introducing a non-zero fourth order spatial focusing term so that the combined effect of said second and fourth order spatial focusing terms is a reduction in the spread of ion arrival times ΔT.