A design providing achromatic correction to a multipassage magnetic mass sp
ectrometer previously described by the author is presented. The energy spat
ial dispersion caused by repeated passages in the magnetic prism is correct
ed by three supplementary mirrors placed in a reinjection loop. From this s
tudy one can see that we simultaneously eliminate the energy dispersion ter
m C-Delta E/E and the opening angle aberration term C-x2 and we may also el
iminate the coupled aberration term C-x Delta E/E. (C) 1999 Elsevier Scienc
e B.V. All rights reserved.