KWS-3 'VerySANS': Parameters

Neutron Source:
FRMII reactor in Garching bei München

Nominal Reactor Power	20 MW
Moderation	Heavy Water Moderated
Fuel Element	Enriched ²³⁵U (93%)
Max. Undisturbed Thermal Neutron Flux Density	8.0x10¹⁴ cm^-2s^-1

Reactor	Power	Thermal Neutron Flux Density	Cold Neutron Flux Density
FRMII¹⁾	20 MW	8×10¹⁴ cm^-2s^-1	9.1×10¹³
ILL ²⁾	58 MW	15×10¹⁴ cm^-2s^-1	???
HFIR	85 MW	26×10¹⁴ cm^-2s^-1	???

K.Zeitelhack et al.
Nuclear Instruments and Methods in Physics Research Section A:
Accelerators, Spectrometers, Detectors and Associated Equipment, 560(2), p.444 (2006)
DOI:10.1016/j.nima.2005.12.215

Cold Neutron Source:
KWS-3 is fed from SR-1 beam tube

Cold neutron flux density
9.1×10¹³	[cm^-2s^-1]

“… Inside the D₂O-moderator tank a cold neutron source (CNS) is placed in 40 cm distance to the reactor core axis, close to the thermal flux maximum…”

“…The CNS moderator cell is a vessel of 30 cm in diameter and about 30 cm in height. It is designed to contain maximal 15l of liquid deuterium at 25 K temperature and 150 kPa pressure…”

“… Schematic horizontal cross-section of the D₂ cold neutron source CNS mounted in the thermal flux maximum in the D₂O moderator tank. The beam tube SR-1 feeding the neutron guide system closely faces the displacer of the CNS…”

“… Schematical cross-section of the CNS filled with 12.9 l deuterium when the reactor is operated at 220kW . The displacer is still filled with liquid D₂…”

“…Schematic view of the cold neutron guide system installed during the commissioning of FRM-II. Six primary neutron guides (NL1–NL6) extract neutrons from the cold neutron source CNS at beam tube SR-1. The inset shows a rear view of the primary beam shutter subsequent to SR-1. Neutron flux and beam divergence were investigated at the indicated end positions of NL1, NL2b and NL6a…”

K.Zeitelhack et al.
Nuclear Instruments and Methods in Physics Research Section A:
Accelerators, Spectrometers, Detectors and Associated Equipment, 560(2), p.444 (2006)
DOI:10.1016/j.nima.2005.12.215

Neutron Guide System:
Splitting of NL3a guide

“… The KWS3 guide is designed as a horizontal incomplete ‘‘S’’-shaped guide made of two sections, one which is 3.9 m long and shows a curvature radius R=30m and another one only 2.9m long and curved in an opposite direction (R=30m). After this incomplete ‘‘S’’ guide a 1.2m long straight section is installed. The simulations show that optimal beam characteristics are obtained by m=2 supermirrors coating of the ‘‘S’’ guide for the vertical walls and ⁵⁸Ni for the horizontal walls, while the following straight piece is overall coated with ⁵⁸ Ni….”

“…Neutron flux delivered by the KWS3 guide calculated upon the measured intensity at NL1: open circles—at the entrance;

… the monochromatic beam (λ=12.7Å ,Δλ/λ= 20%) is schematically represented by the large triangle….”

KWS-3 Beam Guide: NL3-a-u-S
Shape: horizontally “S”-shaped, 3 parts
m=2 (bent walls), m=1.2 (straight walls)
Part 1.	Radius: 30m, Length: 3.9 m
Part 2.	Radius: -30m, Length: 2.9 m
Part 3.	Radius: ∞m, Length: 2.1 m
Cross-section WxH:		10×56	[mm²]
Cut-off Wavelength		4	[Å]
Spectrum Maximum		7	[Å]

A.Radulescu and A.Ioffe
Nuclear Instruments and Methods in Physics Research Section A:
Accelerators, Spectrometers, Detectors and Associated Equipment, 586 (2008)
DOI:10.1016/j.nima.2007.11.039

Neutron Velocity Selector
Home-Made

Monochromator: MgLi velocity selector
Wavelength Range λ	10.5 .. 30	[Å]
Wavelength Spread Δλ/λ	17..20	[%]
Default Wavelength λ	12.8	[Å]
Default Wavelength Spread Δλ/λ	17	[%]

“ … The cylindrical rotor with a diameter of 21 cm of the basic area. The material consists of an alloy of Mg₆₀Li₄₀. It contains about 10% less Li6 than is contained in natural Li. The length of the rotor is 10 cm. In the middle of the cylinder, a hole is drilled to serve for the pressfit on the axis. On the circumference of the cylinder, 60 grooves of a height of 3 cm and an average width of 0.86 cm with a twisting angle of 28.68 are drilled…”

B.Alefeld, J.Thelen and L.Dohmen
Journal of Neutron Research 13(4) (2005) 275-280
DOI:10.1080/10238160310001617866

Entrance Aperture:
Define resolusion

Entrance Aperture	Flexible size:	0x0 .. 10×10	[mm²]
[defines resolution]	Very High resolution mode:	0.7×0.7	[mm²]
	High resolution mode:	2×2	[mm²]
	High intensity mode:	5×5	[mm²]

Intensity at Sample:
Full Mirror

Intensity at Sample	in high resolution mode: [Q=0.0001..0.003Å^-1 ]	24000	n/s
λ=12.8Å full mirror at SDD=10m	in high intensity mode: [Q=0.00025..0.003Å^-1 ]	120000	n/s
λ=12.8Å full mirror at SDD=10m	in very high resolution mode: [Q=0.000035..0.003Å^-1 ]	3000	n/s

Mirror:
Focusing Element

Mirror	Focal Length	11	[m]
[focusing element]	Toroidal shape
	Length x Width x Height	120x12x8	[cm³]
	Radius (Meridional)	531	[m]
	Radius (Sagittal)	0.224	[m]
	Slop Error (Meridional)	0.84	[″]
	Slop Error (Sagittal)	3.35	[″]
	Surface roughness	1.6-2.0	[Å]
	(Mid-spatial frequency roughness)

KWS-3 "VerySANS": Parameters

Summary of the parameters of the KWS-3 instrument

HRD Detector³⁾	Type: Scintillator, ⁶Li, 1mm
[standard]	Active area	∅9.0	[cm]
	Pixel size	0.34:0.34	[mm²]
	Dead-time	2.9	[μs]
	Matrix Dimension	256×256
VHRD Detector⁴⁾	Type: Scintillator, ⁶Li, 1mm
[optional]	Active area	3.0x3.0	[cm]
	Pixel size	0.12:0.12	[mm²]
	Dead-time	2.7	[μs]
	Matrix Dimension	256×256

¹⁾

K.Zeitelhack et al., Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 560(2), p.444 (2006), DOI:10.1016/j.nima.2005.12.215

²⁾

ILL web-page, https://www.ill.eu/reactor-and-safety/high-flux-reactor/technical-characteristics

³⁾

R.Engels, JCNS/ZEA-2, Forschungszentrum Jülich GmbH; HRD=High Resolution Detector

⁴⁾

R.Engels, JCNS/ZEA-2, Forschungszentrum Jülich GmbH; VHRD=Very High Resolution Detector

KWS-3 'VerySANS'

Sidebar

Reduction Program

SANS@MLZ

Useful Links

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