Spectrometer lens for particle beam apparatus

A spectrometer-lens for particle beam apparatus, comprising:

• a magnetic lens means for focusing a primary particle beam onto a specimen to generate secondary particles;
• a spectrometer including
• a first electrode means for accelerating the secondary particles, and
• a second electrode means for decelerating the secondary particles, said second electrode means including two electrodes lying at different potentials said two electrodes being shaped to form surface portions of concentric spheres of different radii, centers of said concentric spheres of said two electrodes lying on a focus of the secondary particles;
• and
• a single stage deflection unit within said lens means having
• at least one electrical deflection means generating a nearly uniform electrical deflection field, and
• at least one magnetic deflection means generating a nearly uniform magnetic deflection field, said electrical and magnetic deflection fields being oriented relative to one another so that field vectors of said fields are at least nearly mutually perpendicular and at least nearly perpendicular to a velocity vector of the accelerated secondary particles, said electrical and magnetic deflection means generating field strengths matched to one another so that a quotient of the electrical field strength amplitude and the magnetic field strength amplitude is approximately constant and is equal to the amplitude of the velocity of the secondary particles after transversing said first electrode means.