Studies of a magnetically focused electrostatic mirror. I. Experimental test of the first order properties

When a uniform magnetic field is superimposed on a uniform electrostatic fi eld, the combination can act as a magnetically focused mirror. This mirror is predicted to have aberrations of opposite sign to those of a magnetic le ns and may therefore be useful as a corrector. We have built all electron o ptical system to test these ideas. The results are presented in two papers, This first paper describes the general design and the results of the measu rements of the first order properties, The second paper (Tsai, F., J. Micro sc. 197 (2000) 118-135) will describe the measurements of the aberration pr operties.