SwissNeutronics AG - Bruehlstrasse 28 - CH-5313 Klingnau - Switzerland - phone: +4156 245 02 02 - tech@swissneutronics.ch

metallic guides

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

Ni / Ti & non-depolarising supermirrors on metallic substrates

Reflectivity profiles of Ni/Ti & non-depolarising supermirror coatings for 3 ≤ m ≤ 6 - fit parameters are based on a parametrization on the reflectivity profile using the expression from McStas: R = 0.64, m = 6.16

Supermirror on Cu - a prototype for ESS (2014)

Phil Bentley et al. (affiliated with the European Spallation Source ESS) have demonstrated by means of Monte-Carlo simulations (MCNP5) that Cu reduces the flux of fast neutron emitted from the tungsten target of the ESS much more efficiently than steel. For this approach and to reduce the fast neutron background further, SwissNeutronics has developed a super-polishing process to make Cu suitable as a substrate for supermirror coatings. The reflectivity of supermirror on Cu shows (Figure 2) a similar reflectivity as obtained for typical substrates for neutron guides as borkron glass and aluminium. The new technology enables for robust Cu-guides for the biological shielding without requiring a gap between the neutron reflecting substrates and the surrounding bulk shielding thus eliminating streaming of high energy neutrons. Clearly, ESS and other spallationsources will strongly profit from supermirror coated Cu-guides from SwissNeutronics as the costs for shielding can be significantly reduced.

Reflectivity of supermirror m = 3 on super-polished Copper as manufactured by SwissNeutronics - fit parameters are based on a parametrization of the reflectivity profile using the expression from McStas: R = 0.84, m = 3.1

Metallic in-pile guide - SR5 @ FRM-II (2015)

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

Metallic in-pile guide - H5 separator @ ILL (2013)

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

Metallic in-pile guide - CTE & CTC @ NIST (2011/2013)

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

Metallic in-pile guide - NG-A-D @ NIST (2009)

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

References for metallic guides - complitation of present and past contracts

instrument / laboratorysubstrate materialyear
FRM II - POWTEX in-pileAl2015
FRM II - SR5b in-pileAl2015
FRM II - TOPAS in-pileAl2015
NIST - CANDORAl2015
ESSAl, Cu, steel2014
ILL - H5 in-pileAl2013
NIST - CTC in-pileAl2013
ILL - ultra cold neutronsAl2011
NIST - CTE in-pileAl2011
FRM II - SR4b in-pileAl2010
ILL - test substratesAl, Ni, zircaloy2010
NIST - NG-A to D in-pile (monolith #0)Al2009