Higher harmonics suppression in Fe/Si polarizing neutron monochromators

D. G. Merkel, B. Nagy, Sz Sajti, E. Szilágyi, R. Kovács-Mezei, L. Bottyán

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The reflected neutron beam originating from a crystal monochromator contains higher order wavelength contributions. Multilayer mirror structures with various custom reflectivity curves including monochromatization and/or polarization of the neutron beam constitute a challenge in modern neutron optics. In this work, we present the study of three types of magnetron-sputtered Fe/Si layer structures with the purpose of higher harmonic suppression. First, an approximately sinusoidal profile was achieved directly by carefully controlling the evaporation parameters during sputtering that leads to first-Bragg-peak reflectivity and polarizing efficiency of Rc=82% and P=97%, respectively. Second, a random, quasi-periodic distribution of the layer thicknesses was implemented, in which the layer structure of the structure was derived from a fit to a prescribed simulated spectrum. This solution resulted in Rc=92% and P=88%. Third, a structure of Fe/Si layers with rounded scattering length profile was constructed starting with a step-like profile and applying 350 keV Ne+ irradiation of 0, 0.5, 1.0, 2.7 and 27×1015/cm2 fluence. Disregarding the highest fluence, the increasing fluence improved the monochromatization (decreasing the intensity of higher order reflections from a total of 11.1% to 2.2% and that of the first Bragg peak from 80% to 70%) and increased the polarizing efficiency from P=79% to 91%). In none of the above structures was a contrast matching agent added to the constituents.

Original languageEnglish
Pages (from-to)92-97
Number of pages6
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume704
DOIs
Publication statusPublished - 2013

Fingerprint

Monochromators
monochromators
Neutron beams
Neutrons
monochromatization
retarding
harmonics
neutrons
fluence
neutron beams
profiles
reflectance
Sputtering
Optics
Multilayers
Evaporation
Mirrors
Irradiation
Scattering
Polarization

Keywords

  • Monochromator
  • Multilayer
  • Neutron optics

ASJC Scopus subject areas

  • Instrumentation
  • Nuclear and High Energy Physics

Cite this

Higher harmonics suppression in Fe/Si polarizing neutron monochromators. / Merkel, D. G.; Nagy, B.; Sajti, Sz; Szilágyi, E.; Kovács-Mezei, R.; Bottyán, L.

In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 704, 2013, p. 92-97.

Research output: Contribution to journalArticle

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