The resolution and chromatic aberration of a doublet of achromatic quadrupole lenses have been experimentally measured. Each achromatic lens is of length 5.99 cm and comprises an electric quadrupole of bore 1.05 mm and a magnetic quadrupole of bore 3.40 mm. In preliminary tests with 600‐keV protons, a chromatic aberration coefficient of less than 1.2 cm and beam width of 4 μ are measured, compared to 20 cm and 4 μ for the same doublet operated in a solely magnetic mode.
REFERENCES
1.
R. L.
Seliger
, J. W.
Ward
, V.
Wang
, and R. L.
Kubena
, Appl. Phys. Letts.
34
, 310
(1979
).2.
J. Orloff and L. W. Swanson, Proceedings of the 10th Annual Scanning Electron Microscope Symposium, March 1977 (IIT Research Institute, Chicago, 1977), Vol. 1, p. 57.
3.
4.
F. W.
Martin
, Ann. N. Y. Acad. Sci.
306
, 262
(1978
). A very small (0.1 m rad) convergence angle was assumed in the reference.5.
R.
Nobiling
, K.
Traxel
, F.
Bosch
, Y.
Civelekoglu
, B.
Martin
, B.
Povh
, and D.
Schwalm
, Nucl. Instr. Meth.
142
, 49
(1977
).6.
Z. H.
Cho
, M.
Singh
, and A.
Mohabbatizadeh
, IEEE Trans. Nucl. Sci.
NS‐21‐1
, 622
(1974
).7.
8.
F.
Watt
, G. W.
Grime
, G. D.
Blower
, and J.
Takacs
, IEEE Trans. Nucl. Sci.
NS‐28‐2
, 1413
(1981
).9.
10.
P. W. Hawkes, Quadrupoles in Electron Lens Design (Academic, New York, 1970), Eq. (162).
11.
Thanks are due to Carpenter Technology, Inc., Reading, Pennsylvania 19603, for a sample of alloy Hiperco 27 HR.
12.
The facilities of Kovar Engineering Services, Inc., 80 Felton St., Waltham, Mass. 02154, were utilized during fabrication and measurement of the lens structure.
13.
B. L. Doyle, Sandia Laboratories, Albuquerque, N. M. 87115 (private communication);
see also B. L. Doyle, N. D. Wing, and P. S. Peercy, in Microbeam Analysis‐1981, edited by R. H. Geiss (San Francisco, San Francisco, 1981), p. 79.
14.
The lens excitation θ is defined as the spatial frequency of oscillation ω in the converging principal section times the effective lens length The individual lens excitations are experimentally set so that the magnetic force is twice the electric force, in which case and the net excitation is given by For we take ignoring the small difference between and See Ref. 20, Eqs. (11c), (245), and (289).
15.
16.
17.
18.
19.
20.
21.
This content is only available via PDF.
© 1982 American Institute of Physics.
1982
American Institute of Physics
You do not currently have access to this content.
