Symposium on X-Ray Microscopy and Microradiography, Cambridge 



43 



butions. The international aspects were emphasized 

 by virtue of ten countries producing 66 papers and 

 with 125 registered participants, several from count- 

 ries not included in the program list. Almost equal 

 thirds of the program were supplied by Great 

 Britain and the Dnited States, with Sweden the next 

 largest contributor. The full program was completed 

 with no parallel sessions by meeting from 9.00 a.m. 

 to 7.00 p.m. with a few short breaks, and full atten- 

 dance was continued till the end, helped somewhat 

 by inclement Cambridge weather. 



The program was generally divided among the 

 three main methods of x-ray microscopy and started 

 with a broad survey of the whole field by Dr. 

 Cosslett. Cambridge. More detailed survey papers 

 were read by Prof. Kirkpatrick, Stanford, on the 

 grazing incidence mirror reflection x-ray microscope; 

 by Prof. Engstrom, Stockholm, on the contact 

 method of x-ray microscopy, where more normal 

 x-ray tubes are used with fine grained emulsions and 

 the specimen is in contact with the film; and by 

 Dr. Nixon, Cambridge, on the point projection 

 method where a special x-ray tube is used to produce 

 initial x-ray enlargement from a point source of 

 x-rays and the image is recorded on coarse grained 

 film. 



Instrumentation of the three methods was well 

 developed since x-ray microscopy is still in the 

 process of experimentation and research on the 

 methods as well as with the methods. Dr. Fitzgerald, 

 New York, and Mr. Ely, London, described special 

 x-ray tubes for contact microradiography incorporat- 

 ing many desirable features for flexibility and con- 

 structed in their respective laboratories. A new gas 

 discharge x-ray tube for long wavelength contact 

 microradiography was described by Dr. Henke, 

 California, and his method of total reflection of the 

 x-rays inside an ellipsoidal mirror gives high inten- 

 sity x-radiation in the 10-100 A region. Dr. van 

 den Broek, Eindhoven, described the commercially 

 available Philips sealed-ofT x-ray tube for contact 

 microradiography at 1-5 kV with a resolution of 

 0.5 micron and early delivery was promised. 



Projection x-ray microscopes of several kinds 

 were mentioned. Dr. Ong and Dr. Le Poole, Delft, 

 discussed their magnetic lens point source tube for 

 high intensity at 1 // resolution and several micro- 

 graphs using their 2 initial enlargement method 

 (specimen equidistant from x-ray source and him 

 and both distances only a few mm) were shown. 

 Paper, blood cells, spermatozoa and replicas of 

 deep fracture surfaces all gave excellent x-ray micro- 

 graphs. Dr. Cosslett, Dr. Nixon and Mr. Pearson, 

 Cambridge, described the recent changes to the 

 series of point source tubes made there and Dr. 

 Siegel and Dr. Knowlton, Cornell, discussed an 

 ingenious conversion of an RCA EMU-2B electron 

 microscope with a 15-minute change-over either 

 way from electron to x-ray microscopy. This kit is 

 produced by Canalco, 4934 St. Elmo Ave., Bethesda 



14, Md., U.S.A. Mr. Newberry and Mr. Summers 

 presented a paper, in absentia, on the latest version 

 of the General E.lectric Co., U.S.A., electrostatic 

 x-ray microscope and several still photographs of 

 cine x-ray micrographs taken at 5 frames per second 

 were shown. 



Two contributions from Drs. Rovinsky, Zulsau 

 and Avdeyenko, Moscow, were also read from the 

 chair. The first described a pin hole camera x-ray 

 method using a 1 // hole and exposure times of 30 

 minutes. The second method used an etched tungsten 

 needle point, radius 0.1 //, as an anode with a ring 

 cathode. 1 // resolution was shown with exposures 

 as low as 3 minutes. Results from test grids were 

 shown for both methods. 



Low intensity limits the performance of projection 

 x-ray microscopes and Dr. Pattee, Stanford, and 

 Drs. Marton, Schrack and Placious, NBS, Washing- 

 ton, described the use of tungsten point field emit- 

 ters as electron sources of high intensity for x-ray 

 microscopy. The former has measured I //A beam 

 current at 9 kV through an angle of 2 10 - rad 

 from a field emitter and the latter authors have 

 focussed their beam to a 5 /< x-ray source. Both 

 feel confident that field emission will help to improve 

 x-ray microscope resolution in the future. 



Theoretical papers of projection x-ray microscopy 

 were read by Dr. Langner, Diisseldorf, Mr. N. Dy- 

 son, Cambridge, and Dr. Cosslett, Cambridge. The 

 first dealt with the variation of intensity and resolv- 

 ing power and confirmed other experimental results; 

 the second discussed image formation, contrast and 

 angular and spectral distribution of the x-rays emit- 

 ted (both in theory and practice) from a point source 

 tube; the third gave a critique of the 2 enlarge- 

 ment method and discussed umbra and penumbra 

 methods of defining resolution. 



The reflection mirror x-ray microscope was well 

 represented by the Stanford school with other papers 

 from Berlin, Paris and Dartmouth. Dr. Pattee, Stan- 

 ford, described a 4-mirror compound reflection x-ray 

 microscope computed for 500 A resolution, field of 

 20 microns, at 4 A x-ray wavelength. Difficulties of 

 alignment have prevented use of this instrument. 

 Dr. Hink, Berlin, described a special high intensity 

 x-ray tube and 2 mirror system that gave I // resolu- 

 tion in practice with 90 minute exposures. Dr. 

 McGee, Stanford, reported results with an 8 A 

 (AlKa) x-ray wavelength 2 mirror microscope, also 

 using a special aluminium anode x-ray tube. Dr. 

 Montel, Paris, presented a difTerent version of the 

 2 mirror system without astigmatism or anamor- 

 phism, by using the 2 mirrors in the same plane 

 unlike the Stanford method. 



Dr. Baez. Redlands, California, showed results of 

 electronic computing of x-ray paths from mirrors 

 of various surface shapes, and Dr. Rieser, Dart- 

 mouth, discussed the effect of surface finish on 

 reflection of the x-rays. 



Various techniques and methods of contact micro- 



