High Speed in XRay Diffraction Work by Use of Polaroid FilmH. K. Herglotz Citation: Review of Scientific Instruments 34, 708 (1963); doi: 10.1063/1.1718556 View online: http://dx.doi.org/10.1063/1.1718556 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/34/6?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Fluorescent Screens for Monochromatic XRay Diffraction Patterns on Polaroid Film Rev. Sci. Instrum. 39, 1658 (1968); 10.1063/1.1683197 XRay Diffraction Camera Using Polaroid Film Rev. Sci. Instrum. 35, 957 (1964); 10.1063/1.1718959 Modified Polaroid Film Holder for XRay and Neutron Diffraction Rev. Sci. Instrum. 34, 1441 (1963); 10.1063/1.1718268 Use of Polaroid Film in XRay Diffraction Rev. Sci. Instrum. 34, 930 (1963); 10.1063/1.1718628 Use of Polaroid Film in Neutron and XRay Diffraction Rev. Sci. Instrum. 33, 128 (1962); 10.1063/1.1717643

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708 NOTES

TABLE 1. Partial pressure HCI (XlO-<J Torr).

Before After bake bake 100°C 200°C 300°C

Sample (AgCl) ~7 ~1 ~1 4.9 44

LiF window 140- S1 45

-After 24 h of pumping a second window dropped from 1 XIO-' to 1 X 10-' Torr of He!.

was loosely wrapped around the glass tube to further re­duce stray light from the mass spectrometer filament. The sample was baked along with the entire system overnight (mass spectrometer not operating), and then heated separ­ately with the mass spectrometer envelope to 300°C (mass spectrometer operating). (See Fig. 1.) The rest of the vacuum system remained at room temperature. The sample underwent three 12-h system bakes before electrical difficulties with the mass spectrometer were overcome, and data on the baked sample could be taken.

Before this sample was baked, the presence of oil de­composition products prevented the detection of less than 7X 10-9 Torr of HCl. The AgCI was then heat cycled up to 300°C and held there for periods varying from 1 to 24 h six times. The 36 and 38 mass peaks were identified as HCl30 and HCP, since their ratio is that predicted by the isotopic abundance of Cpo and Cl37. The sensitivity of the mass spectrometer for HCI was taken as that given by F. W. Lampe, J. L. Franklin, and F. H. Field. 6 After the first preparatory bake cycle, the 20-cm2 AgCl sample was heated to 300°C and the total pressure was made up in approximately the following manner:

80% CO, 10% H 20, 9% HCI, and 1% CO2•

The empty system produced CO, H 20, and CO2 in amounts sufficient to account for that observed in the presence of the AgCl sample, but no HCl.

A 2-in.-diam LiF window sealed with AgCI was also tested in a similar vacuum test setup. However, in this case, a mercury diffusion pump was used and the copper trap was replaced by two liquid nitrogen traps in series. Here, the surface area of the AgCI exposed to vacuum was down by a factor of at least twenty, compared to the pre­vious sample. No interference due to oil decomposition products occurred, since a mercury diffusion pump was used.

Table I compares the mass spectrometer results for the AgCI sealed LiF window to the bulk sample of AgCl.

The amount of HCI observed is not in proportion to the surface area of the sample.

The high production rate of HCl for the LiF window before baking is not understood, and no correlation be­tween the partial pressure of water and the production rate of HCl was found using the somewhat limited H 20

data available. No AgCI or Cb were detected at any time. Assuming that their sensitivity is the same as that of HCI, their partial pressures would appear to have been less than 1 X 10-9 Torr.

* This work was supported under contract with the U. S. Atomic Energy Commission.

1 W. Espe, Werksto.ffkunde der Hochvakuumtechnik (Veb Deutscher Verlag der Wissenschaften, Berlin, 1961), Vol. III, pp. 335-338.

2 Handbook of Chemistry and Physics (1952-1953), 34th Ed., p. 2002.

3 W. H. Kohl, Material and Technique for Electron Tubes (Reinhold Publishing Corporation, New York, 1960), pp. 459-461.

4 M. H. Greenblatt, Rev. Sci. Instr. 29, 738 (1958). • A. H. Sommer, Rev. Sci. Instr. 32,356 (1961). 6 F. W. Lampe, J. L. Franklin, and F. H. Field, J. Am. Chern. Soc.

79, 6129 (1957).

High Speed in X-Ray Diffraction Work by Use of Polaroid Film.

H. K. HERGLOTZ

Engineering Research Laboratory, Engineering Department, E. I. du Pont de Nemours & Company,

Wilmington, Delaware

(Received 18 February 1963; and in final form, 6 March 1963)

T HE successful introduction of a Polaroid film­neutron sensitive phosphor combination to permit

more rapid photography in neutron diffraction work has been reported by H. G. Smith.! Mention is also made briefly of a similar technique in x-ray diffraction. A short­ening of exposure time to 5 min is reported.

A setup of similar type has been in use in our laboratory for some time and has proved itself in several applications. Figure 1 describes the arrangement, consisting of a Du Pont type D (blue fluorescence) miniature radiographic screen in close contact with the Polaroid film. Black cellophane on top of the fluorescent screen base shields it from daylight.

The photographs in Fig. 2, (a) and (b), exemplify the results. A bundle of six aluminum wires, each of the

Film

Phosphor layer

FIG. 1. Apparatus used in high-speed diffraction work.

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NOTES 709

(oo2)Ka

FIG. 2. Example of results of high-speed diffraction work. Photo­graphs obtained by apparatus of Fig. 1 from a bundle of 6 aluminum wires of O.OOs-in. diameter each, conditions-50 k Vp, 8 rnA, 3 sec, ASA 3000 Polaroid film. (a) Original sample; (b) deformed by flexing and twisting.

thickness of 0.005 in., was exposed before and after de­formation. The exposure time (unfiltered radiation from a Cu target, 50 k V, 8 mA, with ASA 3000 speed Polaroid film) was 3 sec. The exposure can be reduced to 1 sec at some sacrifice in photographic quality by using 10 000 speed film.

Figure 2(a), in spite of the short exposure and process­ing time, shows clearly the 111 and 002 reflections from both the copper Ka and K{3 radiation. Thus, the usual wire texture of aluminum, with a [l11J direction in the wire axis, is revealed. The diffraction of the continuous radiation manifests itself in the central star.

The deformation due to twisting of the wire bundle introduces randomness so that Fig. 2 (b) shows a pre­ferred orientation to a far lesser degree.

Low-absorption materials, such as organic compounds, allow for far shorter exposures. Thus, observation of transient phenomena in the crystal structure is made possible. Since only lO-sec processing time is required to obtain the photograph, the method suggests itself for many applications where the result of the x-ray diffraction has some immediate use, e.g., deciding on further treatment of the sample.

1 H. G. Smith, Rev. Sci. Instr. 33, 128 (1962).

Scintillation of Liquid Argon Produced by 10-50 MeV Protons

R. A. GILES AND E. J. BURGE

The Wheatstone Laboratory, King's College, Strand, London, England

(Received 10 January 1963; and in final form, 15 February 1963)

T HE scintillation properties of the noble gases have been reported in the last few years for the gaseous,

liquid, and solid phases. Using low energy protons, deu­terons, and gamma rays, several workers have studied and

utilized the gases; reference to the early work may be found in the paper by Sayres and Wu.1 The gases were found to scintillate well with an emission mainly in the uv, and a number of different schemes have been adopted to match the emission to the response of the detecting photomultiplier. Work by Northrop and Nobles2 sug­gested that argon, krypton, and xenon all gave a greater light output in the liquid phase and had shorter decay times. Scintillations from solidified gases have been re­ported by Northrop and Nobles,2 and by Kruse and and Schardt3 and more recently by Takemota, Hasegawa, and Homma.4 Problems were met due to the imperfect coupling between the scintillator and the detecting sys­tem and crazing on a substrate. Only thin layers gave satisfactory results.

The present work was aimed at extending the applica­tion of the method for measuring the total proton reaction cross section proposed for carbon in plastic scintillator.5,6 For this experiment pulse-height spectra are required at a number of different energies and the most useful ma­terial is a pure nuclear species with relatively few (easily excited) low lying inelastic levels and a good scintillation response. Argon would appear to be a suitable choice with levels at 1.48 and 2,22 MeV,7

The incident particle must be stopped in the scintillator at energies up to 50 MeV, The choice lay between solid and liquid targets and the problems associated with the former led to the design of a liquid target cell. This re­quires a low temperature system to produce the liquid argon (mp-189.2°C; bp-185.6°C) and must be de­signed so that the light from the scintillator reaches the detector in the most efficient way. The previous work indicates that a wavelength shifter would probably be essential, although a quartz system would be valuable for a wavelength shifter not 100% efficient. A target cell was built 1 in. deep and 2 in. in diameter. To allow the incident beam to enter with minimum energy degradation and consequently a minimum of reaction products, a thin

FIG. 1. Sketch of quartz window Invar cell,

P QUATER PHENYL

MELlNEX"""""--

INVAR BODY

QUARTZ WINDOW

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