Oct, l, 1946.e ART P. c. SMITH 2,408,487 ASCERTATNING THE ATOMIC STRUCTURE OF MATERIALS Filed Feb. 29, 1944 „ P0P AMP b Bnvcntor ‘ I MEM” T ! ~ 'Perry l’. Cîîtorneg Patented Oct. 1, 1946 ï 2,408,487 orricla:A f Urufrsov STATES PATENT 2,408,487 ART OF ASCERTAINING THE ATOMIC ` STRUCTURE 0F MATERIALS ' ‘ Perry C. Smith, Moorestown, N. J., assignor to Radio Corporation of America, a corporation _. of _ Delaware Application rFebruary 29, 1944, Serial -No.’524_,42_4 l _ y4 claims. (cl. 25o-49.5) This invention relates to the art of ascertain ing theßatomic -structure of materials> and has special reference to the rprovision of an improved method of and means for producing, recording and interpreting diiîraction patterns. In the usual diffraction apparatus for deter mining the atomic structure, of materials, the electrons or- other rays (e. g., X-I‘ays) which strike, are which emanate from, the specimen are focused upon a photographic plate or film. Prop erly interpreted, the spacingand intensity ofthe rings in the resulting photograpic image or “pat tern” provide .an indication of the atomic struc ture of the specimen and this makes it possible to ascertain changes in the specimen material when the said material is subjected to various treatments and chemical processes. , ~ 2 ` Certainv details of procedure and construction, together withv other objects and' advantages willk be apparent and the invention itself- will be best understood by reference to Atheti-‘ollowing speciñ- l cation and to the accompanying drawing,v wherein: Figure 1>> is a schematic View of an electron __ - dif-~ fraction “camera” embodying the invention andv including certain Vauxiliary translating and re-. cording apparatus, _ _ _ _ _ , ,. .. , Figure 2 is a graph of a diiîraction pattern-pro duced in the “camera” of Fig. 1, and , Y _ Fig. 3 is a schematic view showing the arrange ment of the electrodes of the electron multiplier “pick-up” in the diiïracticn instrument >of Fig. 1.. In Fig. l of the ydrawing there is shown an elec tron dilïraction camera, indicated generally at |-, comprising an >evacuable chamber 3 c_:ontainingga'y vThe examination 3 and interpretation ofsuch photographs requires the use of a precision inf cathode 5, a beam forming anode 1, a specimen strument, such for example as a >microph‘otom 20. holder 9, an .electron lens system_ (exemplified by eter, and can be entrusted only to the most skilled an electro-magnet)- l lV and a pivotedfluorescent technicians..r Further, such work is very tedious and is complicated and limited not only by hu man frailities and mechanical inaccuracies in the screen orv cassette I3„all,arranged in-_spacedarray in the order named along ,theccntralagispfztha chamber 3. The elements thusfar described may measuring instrument, but also by “light scat 25 be of any conventional design (see for example tering” and other undesired phenomena peculiar U. S. Patent No. 2,275,234) and are adapted to to the particular photographic emulsion em-v produce a beam l5 made up of electrons diiiracted ployed. Accordingly. the principal object of the present invention is to obviate the foregoing and other less apparent objections to present day methods of and means for producing, recording and inter _ preting diffraction patterns. from the specimen. As is Well known to those skilled in the art, the invisible rays of which the beam l5 is comprised, are converted into a visible image> of the diffraction ray pattern when the plate I3 is moved into the path of said rays or “beam." In the instant case however, the screen or plate I3 is shown swung upwardly out of the As will hereinafter more fully appear, the ob jects of the present invention are achieved by 35 path of the beam; thus, the only diñraction pat producing a diiïraction ray pattern in space, then tern now present within the Vacuum chamber 3 translating the rays of which the pattern is com exists merely in space. (Such a pattern would prised into an electric current (or voltage) of a be invisible to an observer looking into the cham value proportionate to the intensity of said rays ber through one of the Viewing windows or ports at diil’erent points along a radius of said pattern 40 I1 with which the “camera” is provided.) and then plotting or otherwise recording a graph In carrying the present inventioninto effect, of said current as a function of said radius. The the evacuable chamber 3 is provided with an elec translation or conversion of the rays (of which tronic amplifier device I 9 such for example as the diffraction pattern is comprised) into an elec the electrode assembly of an “electron multiplier” tric current is effected directly or by means of a 45 (say an RCA type 931A), capable of converting -secondarily-emissive electrode assembly and the the rays l5 of which the diffraction pattern 1s plotting and recording of the current may be done comprised into an electric current (or voltage) of either manually, with the aid of a suitable meter, a Value proportionate to the intensity of said or automatically as by means of a facsimile re rays. This electrode assembly I9 is mounted for corder or analogous device. In any event, the 50 movement as on a micrometer screw 2l along a resulting graph or curve contains all of the in radius of the beam and is provided with a mask formation required to be known in the interpre 23 having a slot 23a therein which is arranged tation of a diffraction pattern and may be read in register with the first multiplying stage 4| of by an unskilled observer without the aid of addi the device. The vacuous space about the ampliñer tional equipment. 55 I9 and in the chamber 3 is continuous; hence the 2,408,487 3 rays l5 which pass through the open slot 23a impinge directly upon the electrode 4I and gen erate a secondary-electron current proportionate to the intensity of the rays at the particular point on the radius of the image to which the »said elec trode 4l is presented. As indicated in Fig. 3 the secondary-electrons emitted from the “cathode” 4| are directed by ñxed electrostatic ñelds along fixed paths to the dynode (secondary-emitter) 42. The electrons impinging on this dynode sur; face produce many other electrons;A the number.`Y depending on the energy of the impingingîelec: trons. These secondary electrons are then di rected to the next dynode 53 and‘knock out moref new electrons. This multiplyingprocess is-> re peated in each successive stage (44 to 50 inclu» sive) until those emitted íromth'enlast dynode,_ From the foregoing it is apparent that the pres ent invention provides a simple and reliable method of and means for producing recording and interpreting diffraction patterns. I claim as my invention: l. In combination, means for producing a dif fraction ray pattern ofj'a specimen, in a plane spaced from said specimen, means mounted for movement along a radius of said pattern for con -' verting the diffracted rays which fall along said radius'intofan electromotive force, and means for measuring'l said electromotive force as a function of »said radius. 2i In“combination;V means for producing a dif fraction ray pattern of a specimen in a plane spaced from said specimen, means mounted for moyementalongïaradius of said pattern for con vertingvthe di?fracted rays which fall along said 50, are collected by the anode 5I and constitute radius into an electric current, and means for re the current utilized in the output circuit; The relative position of the amplifier I9 along 20 cording a graph of said current as a function of said'radius. ’ the radius of thediffraction pattern; lâfisfindi 3:. Electron diiîraction apparatusvcomprising anv cated uponk a» scale 25 whichY is `read in> conjunc= evacuable chamberk containing» means for creat@ tion with a pointer ‘21’ on the screw> I9’.-- The out`ing'an electron’beam Aand- for directing said beam» putl of’ the ampliñerl I9" is~ shown connected upon a specimen, an electron lens for; forming 25: through a switch 29î'to a recorder 3l which will the electrons diffracted fromesaidëspecimen into be understood to be driven in eynchronism vwith an electron diffraction vpattermand'for-- projecting the screw 2 I. The recorder 3| thus automatically saidv pattern towarda plane in‘said evacuab'le plots av graph orcurve -showing the current gen chamber, aA secondary-electron emissive ampliñ’er erated bythe ampliñer I9'V as a' function' of the mountedl forl movementN in said' piane4 alongv a radius of the diffraction pattern |5î Alterna 30 radius of said diffraction pattern andiresponsive tively, the output of the translating' device i9 to the impress of‘said'diiîractedïelectrongthereon; may be connected through the switch 29 to a means for moving> saidgampliîñer along< said radius suitableemeter‘33', and 'thel meter‘ readings plotted against thelscal’e 251 In either event'a graphy intensity andfspa'cing ofthe diffractionrings and in said plane, and rnean's'for‘indicatingztliev outr put of said amplifier. 4. The invention asf'set`forth' in claimßl and thus ' contains all’of ‘the informationv necessary to type and is adapted to-,recordthe'outputof said (see Fig; 2) `, is »obtained which shows‘the' relative beknown in the interpretation off av diiîractiorr pattern. The ordinatev of the curve of Fig; 2ïand- wherein said indicating means' isxof- the recording: ampliiier as a function of‘the radius ofV said/elec the-markings of "the sca1e`25 Fig. l, areß’shown 40 tron diffraction pattern.. calibrated in fractions of- an inch; obviously; how-- ever', they may becalibrated in¢Angstrom-units of ‘atomicspacing-g if desired.’ . PERRY." C. , SMITH."