ARGONNE DUAL NEUTRON DIFFRACTOMETERS USING A SINGLE PRIMARY BEAM. Report of Metallurgy Program 4.10.5

Dual neutron diffractometers were designed and built for use at the CP-5 reactor with a number of special features: (1) Two monochromntors are used in an in-line arrangement, as suggested by Levy and Peterson, utilizing the same primary beam with two independent diffractometers, one a horizontal instrument and the other a vertical unit. (2) The two monochromnting crystals may be used in transmission or reflection, and each crystal may be accurntely positioned by external controls. (3) Considerable variations in the wavelength of the primary beam may be made for both diffractometers by changing the take-off angle from the monochromator crystals by means of interchangeable pie-shaped segments. (4) The monochromating crystals are located inside of a relatively small, heavily shielded housing which consists of lead, steel, Boral, and depleted uranium walls which have slotted holes for the exit of two beams, one for the horizontal and the other for the vertical unit. (5) The monochromator housing is surrounded with a large moderating shield which consists of stacked 2-in.thick Masonite die stock forming a 4-ft cube with a minimum thickness of 2 ft from the inner housing. (6) The detector arm on the horizontal diffractometer pivots about the center of the diffractometer table or may also be made to pivot about a point approximately 2 ft from the center of the table. This arrangement permits the use of the horizontal unit as a diffraction instrument aad also as a spectrometer for crystal dynamics studies involving changes of neutron energy. (7) The horizontal table which has optional coupled theta -2 theta motion is constructed so as to support massive accessories, such as cryostat, furnace, and magnet. (8) The vertical unit consists of a Picker diffractometer to which is attached the shielded BF/sub 3/ detector and a counterbalance. Various specimen supports may be attached including a single crystal device which permits 560 deg motion in both chi (X) and phi (O). (9) The movement of the detector arm for both horizontal and vertical instruments may be continuous or incremental by means of the steppm- g device recently described. (10) Provision is made to read visually and to move three angles independently for both horizontal and vertical units by means of this stepping motor. The intensity and angle are recorded by an x-y recorder and in addition, the intensity versus angle is printed automatically with an IBM typewriter. (auth