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AND/R Top Level Specifications
April 9, 2002

  1. Guide Cut
    1. a 22 inch gap in the NG-1 guide system will be created by cutting a neutron guide
    2. position - the gap will be centered in the monochromator cavity 4400 mm downstream of the last guide in the penetration casing, measured along NG-1
    3. vacuum continuity will be maintained across the gap

  2. Monochromator
    1. material and form - pyrolytic graphite (P.G.), in a composite array
    2. individual P.G. crystals are 50mm long and 2mm thick. The height will be chosen to take full advantage of the 150 mm guide illumination (i.e. minimizing the gap between fingers)
    3. attachment - crystals mounted on 7-finger focusing device, 3 layers deep, 1/3 degree angle between layers
    4. nominal orientation - (in neutral position) crystal array mounted vertically, in center of guide cut, horizontal and vertical midpoint on NG-1 central axis, array face normal 45o to NG-1 axis (causing an incident neutron to be reflected westward)
    5. focusing - individual horizontal bands in P.G. array rotate about their horizontal axis, focusing reflected neutrons. Focal length range is from + to 500mm. Focal length is controlled by stepper motor.
    6. motion - besides focusing, the monochromator will be mounted on an assembly which can perform the following movements:
      1. rotation
        1. 20 about the horizontal centerline of the array (in the plane of the array)
        2. 360 about the vertical axis of the array
      2. translation - the monochromator array and the rotating devices can be moved horizontally, 60 mm in a direction perpendicular to the incident beam axis (NG-1)

        note: all compound and individual movement shall be limited to movement that will not cause interference between the guides and the monochromator assembly

  3. Local Beam Shutter
    1. composition- to be determined
    2. speed of opening/closure- 15 sec
    3. status indication/control - compliant with "Experimental Shutter Control List of Requirements" (Mark English 4/30/2001)
    4. position - the shutter will be located in the interior of the west wall shield, and will function to close the beam opening through the west wall shield

  4. Shielding
    1. shielding shall consist of specially designed shielding tanks that are assembled in such a fashion that no radiation streaming occurs.
    2. surrounding the monochromator, shielding shall be placed to stop radiation in all directions, except the opening for the reflected beam and the area surrounding the NG-1 neutron guide. The shielding thickness is as follows:
      1. below monochromator - 30 inches (filled base)
      2. above monochromator - 21 inches
      3. along NG-1 upstream - 12 inches
      4. along NG-1 downstream - 16 inches
      5. west of monochromator (towards sample) - 18 inches
      6. east of monochromator - 22 inches
    3. shielding tanks shall be filled with steel shot and paraffin.

  5. Monochromator-to-Sample Beam Conditioning
    1. Neutrons reflected from the monochromator pass through the west shield in an opening 22 inches wide by 10 inches tall. It is centered horizontally and vertically on the guide cut center.
    2. Optical Bench (Lower) - Attached to the outer face of the west wall shield is a horizontal optical bench constructed of aluminum or stainless steel. It contains a grid of tapped holes. The grid has a 2 inch spacing in both directions and the holes are ¼ - 20 UNC tapped through the 1 inch plate. The lower optical bench measures 32 inches x 20.25 inches (long axis perpendicular to the NG-1 guide axis). It is attached to the shield so that the top surface is 12.5 inches below the central beam axis of NG-1.
    3. Optical Bench (Upper) - attached to the inner face of the west wall shield is an optical bench above the beam. It is constructed of aluminum or stainless steel. It measures 11.25 inches in the direction of the reflected beam and is 20.25 inches wide. The hole pattern is the same as on the bottom plate. It is attached to the shield so that the bottom surface is 5.0 inches above the central beam axis of NG-1.
    4. Beam Conditioning - the upper and lower optical benches allow the attachment of the following incident beam conditioning devices:
      1. aperture(s)
      2. spin flippers
      3. polarizer
      4. soller collimator
    5. Adjustments - the beam conditioning devices are mounted such that the following degrees of freedom are available:
      1. aperture(s) -horizontal position (perpendicular to reflected beam axis)
      2. spin flippers - roll, vertical position (coarse adjustment, in initial setup)
      3. polarizer - roll, yaw, horizontal position
      4. soller collimator - roll, yaw, horizontal position

  6. Sample Table
    1. load capacity - the sample table will accommodate a maximum load of 500 daN (1,120 lbf), applied no more than 5 inches from the central vertical axis of the sample table assembly
    2. clearance - the vertical distance from the top of the sample table assembly to the sample center point is 350 mm (13.7 inches), the horizontal distance from the vertical sample table axis to the nearest obstruction or interference is 375 mm (14.75 inches)
    3. motion
      1. rotation - full 360 rotation about the vertical axis (resolution - .0005 ), 20 about either orthogonal, horizontal axis through the nominal sample center point (resolution - .004 )
      2. translation
        1. vertical - none; initial installation will place the horizontal rotation axes at the proper height
        2. horizontal -both sample table and detector arm assembly can translate 63 mm (2.5 inches) in a direction parallel to NG-1 (resolution - 2 x 10-5 inch). In a direction along the incident beam, the entire sample table and detector arm can translate 356 mm (14 inches), varying the monochromator-to-sample-axis distance from 80 inches to 94 inches (resolution - 2 x 10-5 inch).
        3. in addition, a translation stage mounted below the two chi segments allows a relative translation between the common rotation center of the chi segments and the vertical rotation axis of the sample table. The translation range is 125 mm (5 inches) on two perpendicular, horizontal axes (resolution - 5 x 10-4 inches).
    4. sample mounting - various "boosters" or shims will be constructed to mount sample environments such that the sample center is at the proper position.
    5. base position - the base of the sample table and detector arm will be anchored to the guide hall floor. Provisions will be made to allow the repositioning of the base from its original position. The range of allowable repositioning will be 12 inches in any direction from the original position.

  7. Sample-Reflected Beam Conditioning
    1. Optical Rail - mounted between the sample table and detector is a length of Newport X-95 rail. The rail is attached to the detector arm. The rail measures 35 inches in length, starting at a distance of 12.9 inches from the sample table axis. The rail can be slid downstream in the reflected beam direction for longer sample-to-detector distances. The rail can be removed and replaced reproducibly or replaced with other X-95 rails.
    2. Beam Conditioning - using X-95 clamps as bases, the following beam conditioning devices can be mounted in the beam:
      1. aperture(s)
      2. spin flippers
      3. polarizer
      4. soller collimator
    3. Adjustments - the beam conditioning devices are mounted such that the following degrees of freedom are available:
      1. aperture(s) - horizontal position (perpendicular to reflected beam axis)
      2. spin flippers - roll, vertical position (coarse adjustment, in initial setup)
      3. polarizer - roll, yaw, horizontal position
      4. soller collimator - roll, yaw, horizontal position

  8. Detector
    1. shielding - detector shall be housed in a shield (a 16 inch cube). The shield shall have an opening allowing illumination of the active area by sample-reflected neutrons. The shielding shall consist of high-density polyethylene, boroflex™, and cadmium, designed so that the minimum path length (through shielding) from the exterior to the detector is 7.5 inches. A layer of 4mm boroflex and a layer of .020 inch cadmium will line all inside faces of the shield (the innermost layer is cadmium). Cables (HV, LV, and signal) shall be routed through the shielding in such a way as to minimize shielding loss.
    2. mounting - the detector and surrounding shielding shall be mounted on a trolley. The detector shall be mounted in such a fashion that it is electrically isolated from the trolley and the remaining instrument.
    3. travel - the detector trolley shall ride on rails mounted on an arm such that the horizontal center of the active area is at the sample center height (nominally 48 inches above the floor). The detector arm shall rotate about the vertical sample table axis in a range from -120 to +120 as observed in a plan view with a resolution of 5 x 10-4 . The sample-to-detector distance can be set manually in a range from 56 inches to 68 inches.


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