A Kossel microdiffraction camera has been adapted to the National Bureau of Standards electron probe microanalyzer. Design criteria for a Kossel camera are discussed and evaluated. The details of their adaption to the National Bureau of Standards Kossel microdiffraction camera are given. The major features adopted were (1) transmission camera, (2) inclusion of microgoniometric capabilities, (3) film cassette in air rather than vacuum, and (4) source to film distance adjustable between 5 and 11 cm. Transmission pseudo-Kossel patterns of an aluminum crystal obtained with Cu radiation are presented to illustrate the capabilities of the camera.
A loading device used primarily in conjunction with Kossel (divergent beam) x-ray diffraction is described. The device is compatible with any standard upright metallograph as well. It is 10.1 cm in diameter and accommodates specimens 2.5 cm in reduced section by 6 mm wide. The device utilizes small load cells having ranges of 0 to 44.5 N and 0 to 445 N respectively. Load cell error is ±0.5% of the full load capacity. Load changes of 0.2% of load capacity can be observed. The load device is mechanically and electrically stable. Loads are read on a standard commercial universal indicator.
.A Kossel patte~n ge nerator, designed and built at th e National Bureau of Standards , is desc ribed In detaIl. Th e Unit IS modular a nd co nsis ts of an electron beam column, vac uum system, light mi c ro· sso pe, film cas selle, an d Kossel ca mera. The ca mera compone nt includes mic rogoniometric capa· blhtles . The Kossel x-ray techniqu e e nables th e investi gator to obtain lattice spacing data precise to two or three parts p er million , and orientation of c rystals to 0.1 0 of arc. The Kossel pallern ge n· e rator de scnbed permIts d ata for such de terminations to be obtained quickly and precisely.Key Word s : Dive rgent x-ray beam , in s trum e nt design, Kosse l camera, Kossel method, x·ray instrum e ntati on.
"The exposure t!me for a Kossel photograph may var y fro m n few seconds t o a few hours. Iher?f.orc, It IS des lI'a ble to be a ble to estimate the expos ure t im e for vari ous experim enta l cond ItIOns . lIence, seml empll"l Cal r elatIOns for the expos ure t im e of a K o sel mi cr od iffraction ~attern have bee n d eveloped. ,Equat ions a re presented for bot h t ra nsmiss ion a nd back l efi ec tlOn I{o sel photographs. rhc e equations ar e testcd for validity u ing t,vo different co mmmc ia lly a va da ble x-ray fi lm s . . It I~ s hown t hat t he agreeme nt of act ual expos ure t imes WIth predIc ted expos ure t im es IS vali d WI t hin 10 to 15 perce nt. )It h as long been known that the exposure time of a Kossel photograph has a well-defined optimum [1].1 However, useful analytical expressions enablino-one to calculate the exposure time have not been b presented. Therefore, the purpose of this paper is to propose expressions fol' the exposure time in both the transmission and the b ack reflection Kossel reo"ions.In the transmission mode, the Kossel gonics usually appear light on a darker background and the contrast is, at best, not good [2,3]. In the b ack reflection region, the conics appear darker than the background, and the contras t may be somewhat better than in transmission [2]. The only practical source for Kossel patterns is a finely focused electron beam whic~ i.s allowed to .stl:ike either the sample or a source fOlI m close proxumty to the sample. The latter case wi~l be disc~ssed as it is the more general and more useful. It WIll be assumed that the film is in a vacuu~ and that once the x rays leave the sampl~, h~vl?g u~dergone the usual exponential reductIOn m mtenslty, t hey travel unimpeded to the film . If an x-ray window and airpath intervene the reduction in intensity of the x rays emero·ent from the sample can also be accounted for by b the usual expone.nt~al retardation law which simply appear s as a multIplIer. ~ Using .a focused bea~ of electrons, one may vary the speClmen current, I.e., the number of electrons fl~wing to ground per unit time from specimen or foil, and the accelerating potential of the electron.s. A knowledge of the number of photon.s p er electron which strik. e .the film and of the film area is necessary. Some prOVISIOn for the fact that the exposure is not constant over the expanse of a flat film is also necess ary . Bearing each of these requirements III mind, we may write for the e>.rposure:I Figures in brackets indicate the literature references at the end of this paper.
Most modern instrumental methods of analysis depend on the use of known standards of composition for calibration. Newer analytical techniques, such as the solids mass spectrometer, laser probe and, especially, the electron-probe microanalyzer have reduced the amount of a sample which can be analyzed quantitatively to a range of about 0.1 to as small as 0.00005 μg. As a corollary to these microanalytical advances, homogeneity requirements have become severe to meet analytical standards. This paper describes a continuation of the National Bureau of Standards' effort to characterize more fully existing standards as to suitability for the new microanalytical techniques. An NBS cartridge brass sample in both the wrought (NBS-1102) and chill cast forms (NBS-C1102), as well as a low-alloy steel sample (NBS-463), have been investigated by means of electron-probe micreanalysis and optical metallography. Some 17 elements are contained in the brass, while 25 elements are found in the steel. Results for 10 elements in the steel and 6 elements in the brass are presented. In the steel, iron, nickel, copper, and silicon ate essentially distributed homogeneously at micron levels, while manganese, tantalum, niobium, zirconium, sulfur, and chromium are not. In the brass, copper and zinc are distributed homogeneously at micron levels while lead, sulfur, aluminum, and silicon are not. Electron-probe micreanalyzer results indicate that both NBS-1102 and NBS-C1102 brass are suitable for use as a calibration standard for electronprobe microanalysis as well as other microsnalyticat techniques, such as the solids mass spectrometer. The results for brass have been corroborated by a number of laboratories using the electron-probe analyzer.
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