PROJECTION MICROSCOPY 



7. BoTHE, W., Handb. Phys. XXII, 2, Springer: 



Berlin 2nd Edit. 1932. 



8. Clark, J. C, and Kelly, H. R., Phys. Rev., 



59, 220 (1941). 



9. CoMPTON, A. H., AND Allison, S. K., "X-rays 



in theory and experiment", Van Nostrand, 

 New York, 1935. 



10. Cosslett, V. E., (1959) Unpublished. 



11. Cosslett, V. E., and Dyson, N. A., contribu- 



tion to "X-Ray Microscopy and Microradi- 

 ography" Academic Press, New York, 1957. 



12. DoFFiN, H., and Kuhlenkampff, H., Z. 



Phys.,U8,49Q (1957). 



13. Dolby, R. M., Brit. J. Appl. Phys. (1960). (in 



press). 



14. Dyson, N. k.,Proc. Phys. Soc.,73, 924 (1959a). 



15. Dyson, N. A., Brit. J. App. Phys., 10, 505 



(1959b). 



16. Honerjager, R., Ann. der Phys., 38, 33 



(1940). 



17. Kerscher, R. and Kuhlenkampff. H., Z. 



F/iys., 140, 632 (1955). 



18. KiRKPATRICK, P., AND WiEDMANN, L., PhyS. 



Rev., 67, 321 (1945). 



19. Kramers, H. A., Phil. Mag., 46, 836 (1923). 



20. Kuhlenkampff, H., Ann. Physik, 69, 548 



(1922). 



21. Kuhlenkampff, H., Ann. Physik, 87, 597 



(1928). 



22. Kulenkampff, H., and Schmidt, L., Ann. 



Physik, ^Z, 494 (1943). 



23. Lane, R. O. and Zaffarano, D. J., Phys. 



Rev.,M, 960 (1954). 



24. Lenz, F., Zeit. Naturforsch., 9a, 185 (1954). 



25. Massey, H. S. W., and Burhop, E. H. S., 



"Electronic and Ionic Impact Phenomena" 

 Oxford, 1952. 



26. Nepf, H., Zeit. Phys., 131, 1 (1951). 



27. Nicholas, W. W., Bur. of Stand. J. of Res., 



2, 837 (1929). 



28. Nixon, W. C, Proc. Roy. Sac, A232, 475 



(1955). 



29. Paul, W., and Steinwedel, H., (Article in 



"/3- and 7-ray Spectroscopy", ed. K. Siegbahn, 

 North Holland Publishing Co. Amsterdam), 

 1955. 



30. Sauter, F., Ann. d. Physik., 20, 404 (1934). 



31. ScHEER, M., AND Zeitler, E., Z. Phys., 140, 



642 (1955). 



32. ScHERZER, O., Ann. Physik, 13, 137 (1932). 



33. Smick, a. E., and Kirkpatrick, P., Phys. 



Rev., 60, 162 (1941). 



34. Worthington, C. R., and Tomlin, S. J., 



Proc. Phys. Soc, 69A, 401 (1956). 



N. A. Dyson 



PROJECTION MICROSCOPY (See a/so p. 647) 



The idea of using a small x-ray source for 

 projecting enlarged images was mentioned 

 by Sievert (1) in 1936. In order to limit the 

 efifective emitting area, the use of a pinhole 

 aperture was proposed. This method usually 

 called the camera obscura or pinhole camera, 

 was re-introduced by Avdeyenko, Lutsau 

 and Rovinsky (2) at the Cambridge Sym- 

 posium on x-ray microscopy and micro- 

 analyses. It is equally suitable for both trans- 

 mission and emission microscopy. 



In 1939, von Ardenne (3) proposed use of 

 an electron optical system to make an x-ray 

 source of very small dimension and high 

 specific load. This type of microscope (which 

 was successfully realized by Cosslett and 

 Nixon (4) in 1951) is usually called the pro- 

 jection microscope. 



Since 1951, the problems of obtaining 

 better resolution and more reliable instru- 

 mentation have been studied by Cosslett, 

 Nixon and Pearson (5) (England), Le Poole 

 and Ong (6) (Holland), Newberry and 

 Summers (7) (USA) and Bessen (8) (USA), 

 among others. 



The Projection Microscope 



Principle. The projection microscope is a 

 microfocus x-ray tube, consisting essentially 

 of an electron source, an electron optical 

 system, and a transmission type target 

 (Fig. 1). 



The electrons w^hich have an energy of 

 some 5-15 keV are focused onto a 1-0.1 n 

 spot. In most cases the target acts as a vac- 

 uimi seal, allowing the specimen to remain 

 in air. The electron optical system consists 

 of a very, strong lens, usually called the ob- 

 jective, and a weak one, the condenser. The 

 function of the latter is to regulate the rate 

 of demagnification of the lens system. As 

 the current density of the electron spot 

 largely depends on its size, the use of the 

 condenser is indispensable for optimum 

 working conditions. Due to the short life- 

 time of both target and cathode filament, 



661 



