A-2_STATEMENT_OF_WORK.doc

ATTACHMENT A

NIST NCNR LENSES AND PRISMS

STATEMENT OF WORK AND DRAWINGS

I. BACKGROUND

The National Institute of Standards and Technology (NIST), Center for Neutron Research (NCNR) focuses on providing neutron measurement capabilities to the U.S. research community. It is the national center for research using thermal and cold neutrons, offering its instrumentation for use by all qualified applicants. Many of its instruments rely on intense beams of cold neutrons emanating from an advanced liquid hydrogen moderator.

II. OBJECTIVE

The NCNR is currently undertaking a facilities expansion to include a new Very Small Angle Neutron Scattering (VSANS) instrument. The instrument will use refractive lenses and prisms for focusing eighteen separate neutron beams at the detector and correcting for gravity over a long flight path of 45 m. Due to the small negative deviation from unity for the refractive index from neutrons, the lenses and prisms will be stacked into a compound refractive optic as shown schematically in Figure 1 below.

Figure 1

Sketch of compound series of lenses for focusing and compound series of prisms for correcting neutron trajectory for gravity. Sketch shows six separate vertically arranged neutron beams. Application will have stack of 6 vertical x 3 horizontal = 18 beams.

III. REQUIREMENTS

NCNR requires the following items:

· 200 Biconcave Lenses

· 56 Right Angle Prisms

The above items shall be in accordance with the following specifications.

To obtain acceptable neutron transmission, the compound refractive optic must be made from magnesium fluoride single crystals of high purity. The material used to manufacture the required lenses and prisms shall be optical quality single crystal Magnesium Fluoride (MgF2). Crystal orientation can be random, since not birefringence occurs with neutrons. The required items shall have material purity in the following three (3) elements that are highly absorbing of neutrons:

Boron: <1.3ppm (parts per million by weight)

Cadmium: < 4.3 ppm (parts per million by weight)

Gadolinium < 0.3 ppm (parts per million by weight) The lenses shall meet the following specifications:

· The lenses shall be biconcave;

· Surface profile error: ≤ λ at 632 nm wavelength

· Surface Quality: 40-20 (scratch-dig specification)

· Coating: not coated

· Lens diameter: ø = 12.7 mm (+0,-0.1 mm)

· Center thickness: t = 2.0 mm (+/-0.3 mm)

· Radius of Curvature: R1 = R2 = 12.7 mm (+/-0.2 mm) (Note to accept standard curvatures from manufacturer’s tooling, it is acceptable to have 10 mm < RL < 13 mm).

· Clear aperture: 90% of lens diameter.

The prisms shall meet the following specifications:

· The prisms shall be right angle prisms;

· Flatness error: ≤ λ at 632 nm wavelength

· Surface Quality: 40-20 (scratch-dig specification)

· Coating: not coated

· Prism edge length: A = B = 17.8 mm (+0,-0.2 mm)

· Prism transverse length: C = 50 mm (+/-0.3 mm)

· Angle tolerance: +/- 10 arc minutes

· Bevel: 45˚, < 0.4 mm

Provided below are sketches of both the required lenses and prisms for reference.

Figure 2

Drawing of biconcave lens. Note that the radius curvature of lens R1 = R2 = 12.7 mm. (Note to accept standard curvatures from manufacturer’s tooling, it is acceptable to have 10 mm < RL < 13 mm).

Figure 3

Drawing of right angle prism. Note dimension A = B = 17.8 mm is given in specifications.

IV. DELIVERY

FOB Destination delivery terms are required. Delivery shall be completed within three (3) months of an award. The Contractor shall deliver all equipment to NIST, Building 301, Shipping and Receiving, Gaithersburg, MD 20899-1640. The Contractor shall notify the NIST Technical Point of Contact (TPOC) at least one week prior to shipping.

Attachment A – NIST NCNR Lenses and Prisms SOW and Drawings