Metallic guides are key elements for modern neutron guide systems. SwissNeutronics developed a super-polishing process to refine the surface of metallic substrates for the coating of neutron supermirrors with large m-values and excellent reflectivities. The properties are:

• super-polishing of aluminum & copper
  roughness ≈1 Å (RMS)

• high reflectivity (like super-polished glass)

• highly reproducible large scale fabrication

• stability against irradiation ↔ no degradation up to
  9×10¹⁹ n/cm²

• mechanical robustness, extended machining options, including welding

• copper substrates for highly efficient shielding.

The following figure shows representative reflectivity profiles of various supermirrors prepared on metallic substrates:

Downloads: Flyer metallic substrates, Flyer supermirror

The FRM-II replaced the beam port SR5 in order to equip it with new neutron optics for the beam extraction to provide neutrons to three instrument in the new guide hall. All new neutron guides in the beam port are made from aluminium substrates for extended lifetime.

• 	Type:	3 beamlines a 3 guide units
  	Path/profile: - SR5a: - SR5b: - SR5m:	straight / elliptic (truly curved) straight / parallel straight / elliptic (polygonal approximated)
  	Cross-sections: - SR5a:     - SR5b:     - SR5m:	□ 32.4 mm -> □ 43.8 mm □ 43.8 mm -> □ 49.3 mm □ 49.3 mm -> □ 50.6 mm 40 mm x 98 mm 47 mm x 97 mm 46 mm x 96 mm 15.2 mm x 50.1 mm -> 28.7 mm x 61.2 mm 28.7 mm x 61.2 mm -> 37.4 mm x 69.5 mm 37.4 mm x 69.5 mm -> 39.7 mm x 71.5 mm
  	Length:	1405 mm / 906 mm / 233 mm
  	Coating:	Ni/Ti, m = 2.55 / 3.75 / 4
  	Substrates:	super-polished aluminium

Within the millennium program the ILL refurbished the neutron guide system H5. For the in-pile section a robust neutron guide was required to withstand the high radiation field and the elevated temperatures. This tasks are achieved by using aluminium substrates. SwissNeutronics has developed a sophisticated process to super-polish the aluminium substrates to become atomically smooth. The process yields a roughness < 1 Å (RMS). These substrates enable excellent reflectivities of the supermirrors. In case of the H5 metallic guide the average reflectivity was Rave = 0.89 @ m =3. The H5 in-pile guide is a multi-channel guide which starts with large common cross-section (170 mm x 120 mm) and branches to three guides over a total length of 2.8 m.

• 	Type:	guide assembly, feds one beam into 3 individual guides
  	Path/profile:	multi-axis, straight
  	Cross-sections:	170 mm x 120 mm -> 60 mm x 120 mm / 67.7 mm x 120 mm / 40 mm x 120 mm (common entrance / individual exits, respectively)
  	Length:	2800 mm
  	Coating:	Ni/Ti, m = 3
  	Substrates:	super-polished aluminium

At NIST all guide systems were equipped with metallic guides at the in-pile section. Both, the CTC and CTE guide systems branch into multiple individual guides. The metallic in-pile guide assemblies are designed for this purpose as guide splitters. Special features for the outer contour were required because of the spatial constraints of the beam port.

• CTE metallic guide
  	Type:	guide assembly, splitter into 3 individual guides
  	Path/profile:	multi-axis, straight
  	Cross-sections:	152 mm x 155 mm -> 50 mm x 120 mm / 60 mm x 150 mm / 50 mm x 120 mm (common entrance / individual exits, respectively
  	Length:	1106 mm
  	Coating:	Ni/Ti, m = 3
  	Substrates:	super-polished aluminium
  CTC metallic guide
  	Type:	guide assembly, feds one beam into 4 individual guides
  	Path/profile:	multi-axis, straight, converging
  	Cross-sections:	245 mm x 220 mm -> 60 mm x 150 mm (4x) (common entrance / individual exits, respectively)
  	Length:	1608 mm
  	Coating:	Ni/Ti, m = 3
  	Substrates:	super-polished aluminium

For the in-pile section of the new neutron guide system at the NCNR at the National Institute for Standards and Technology (NIST) the customer decided using the latest technology for metallic guides uniquely provided by SwissNeutronics. This guide assembly is located at a distance of about 1440 mm from the moderator. Since this region is subject to an increased thermal and radiation load, it was desired to fabricate it from aluminium substrates.
A complex geometry and various m-values from 1.2 to 3.6 were required to match the phase space of the subsequent neutron guides. The fabrication of the guide assembly was performed including the sophisticated super-polishing, supermirror coating with reflectivity measurement of all substrates and highly accurate assembly.

• 	Type:	guide assembly (Common guide in front of the subsequent individual guides)
  	Path/profile:	multi-axis, straight
  	Cross-sections:	151 mm x 157 mm -> 223 mm x 157 mm (common entrance / individual exits, respectivel)
  	Length:	933 mm
  	Coating:	Ni/Ti, m = 1.2 -> 3.6
  	Substrates:	super-polished aluminium