Orthogonal acceleration coaxial cylinder time of flight mass analyser

A Time of Flight mass analyser comprising:

• an annular ion guide having a longitudinal axis;
• a first device arranged and adapted to introduce ions into said first annular ion guide, wherein an electric field is applied to the annular ion guide so that said ions form substantially stable circular orbits within said annular ion guide about said longitudinal axis;
• an ion detector disposed within said annular ion guide;
• a second device arranged and adapted to orthogonally accelerate ions in a first axial direction from said substantially stable circular orbits within said annular ion guide such that ions follow substantially spiral paths as they pass through said annular ion guide;
• and
• a third device arranged and adapted to maintain an axial DC potential along at least a portion of said annular ion guide so that said ions are reflected in a second axial direction which is substantially opposed to said first axial direction and so that said ions undergo multiple axial passes through said annular ion guide before being detected by said ion detector.