1. PAC for Condensed Matter Physics
A proposal for a bent neutron guide at beam line 7A of the modernized fast pulsed reactor IBR-2M for the diffractometers EPSILON-MDS and SKAT
Christian Scheffzük
Frank Laboratory of Neutron Physics Dubna & FU Berlin
PAC for Condensed Matter Physics
Dubna, April 16, 2007
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2. outline scientific subject instrumentation at beamline 7A: EPSILON-MDS
SKAT
neutron guide at present state
new neutron guide:
requirements
simulations
conclusions
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3. mainly investigation of geological samples:
scientific subject
mainly investigation of geological samples:
- better understanding of deformation processes
- strain-stress distributions / redistibutions
- formation of texture as a result of applied stresses
- texture / strain relation
EPSILON-MDS:
- in-situ applied strain
- residual strain distribution
- surface strain
- acoustic emission during
deformation processes
SKAT:
- bulk texture determination
- in-situ texture changes
- deconvolution of
deformation history
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4. beam layout at channel 7A
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5. Experimental hall with neutron diffractometers
EPSILON
SKAT
NSWR
NERA
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6. The EPSILON-MDS strain/stress diffractometer
3He detectors
and preamplifiers
sample
goniometer
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7. SKAT at present
by Ullemeyer, K.
7/23

8. Intended improvement of SKAT
by Ullemeyer, K.
8/23

9. Present state of the neutron guide
construction of the neutron guide in the mid-eighties
the neutron guide is straight
starts at a long distance from the surface of the moderator ( > 6 m distance)
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10. Present state of the neutron guide
construction of the neutron guide in the mid-eighties
the neutron guide is straight
starts at a long distance from the surface of the moderator ( > 6 m distance)
d. the neutrons have to fly a path through between moderator and neutron guide head
e. misfit of the moderator surface size ([HxW]: 270 x 200 mm2) and the cross section of the neutron guide ([HxW]: 170 x 50 mm2)
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11. Moderator size and neutron guide cross section
distance: moderator – neutron guide: 6 m
limitation by:
Liouville-Theorem:
beam cross section x beam divergency = const.
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12. Present state of the neutron guide
construction of the neutron guide in the mid-eighties
the neutron guide is straight
starts at a long distance from the surface of the moderator ( > 6 m distance)
the neutrons have to fly a path through between moderator and neutron guide head
misfit of the moderator surface size ([HxW]: 270 x 200 mm2) and the cross section of the neutron guide ([HxW]: 170 x 50 mm2)
f. at a distance of about 47 m from the moderator is an interrupt (pillar) > gap
g. misfit of beam cross section and sample dimensions
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13. Neutron guide and sample dimensions
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14. Neutron intensity distribution
view to the neutron source
by Churakov, A.V. & Bogdsel, A.A.
14/23

15. Present state of the neutron guide
construction of the neutron guide in the mid-eighties
the neutron guide is straight
starts at a long distance from the surface of the moderator ( > 6 m distance)
the neutrons have to fly a path through between moderator and neutron guide head
misfit of the moderator surface size ([HxW]: 270 x 200 mm2) and the cross section of the neutron guide ([HxW]: 170 x 50 mm2)
at a distance of about 47 m from the moderator is an interrupt (pillar) > gap
low neutron flux
=> the experimental possibilities by improved diffractometers
can not be used to full capacity
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16. Basic requirements for the new neutron guide
improvement of the resolution (low divergency)
b) increasing of the neutron flux at sample position:
i) effective use of the interface moderator – neutron guide head
for intensity gain
ii) adaptation of the neutron guide exit cross section to sample‘s dimensions
=> splitting of the neutron guide into two sub-beams
=> different exit cross sections for
SKAT: 50 x 50 mm2
EPSILON-MDS: [HxB]: 40 x 5 mm2
iii) neutron guide splitter for beams 7A and 7B
c) reduction of the background (removal of the fast neutrons)
=> bent neutron guide
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17. Horizontal cross section of the reactor IBR-2M and the environment
VII
VII
VII
VIII
VIII
VIII 2 4 2 1 1 1 2 2 5 3 3 3
at 5.95 m
at 6.05 m
at m
1 - surface of the orthogonal beam line No. 7
2 - comb-shaped water moderator
3 - pre-moderator
4 - post-moderator
5 - cryogenic mesithylen moderator
by Kulikov, S.A. & Shabalin, E.P.
17/23

18. by Kulikov, S.A. & Shabalin, E.P.
Differential neutron density as function of energy and wavelength: beamline 7, IBR-2M
by Kulikov, S.A. & Shabalin, E.P.
18/23

19. Thermal neutron distribution: beam line 7, IBR-2M
0.957 meV
2.1 meV
23.5 meV
5 meV
modified after Kulikov, S.A. & Shabalin, E.P.
19/23

20. Simulations of neutron distribution: beamline 7, IBR-2M
E < meV
0.957 meV < E < 2.1 meV
(a)
(b)
2.1 meV < E < 5 meV
5 meV < E < 23.5 meV
(c)
(d)
view from the neutron source
by Kulikov, S.A. & Shabalin, E.P.
20/23

21. I. As conclusion: favourite neutron guide
 incident cross section: 50 mm (w) x 125 mm (h)
cold source (mesithylen 20 K)
neutron flux: 2.3 x 1014 n / (cm2 s)
 exit cross section:
- EPSILON-MDS: [HxW]: 40 x 5 mm2
- SKAT: 50 x 50 mm2
 10 m straight neutron guide (m = 1) ([HxW]: 125 x 50 mm2)
 88 m bent neutron guide ([HxW]: 125 x 50 mm2), r = 13,400 m (m=1)
- including 10 m „anti-trumpet“ (focusing element) for vertical
reduction for the SKAT-neutron guide:
condenser: from [HxW]: 125 x 50 mm2 down to 50 x 50 mm2
- at the end: neutron guide segments with lower cross-section for the
EPSILON-neutron guide: [HxW]: 40 x 5 mm2
 neutron flux: 2.6 x 109 n / (cm2 s)
 Divergence: Δα = rad. (0.45°), Δβ = rad. (0.9°)
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22. II. As conclusion: geometry of the favourite neutron guide
distance, mm
horizontal shift : 1.2 m
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23. Acknowledgement - K. Walther (FU Berlin)
A. Frischbutter, F. Schilling (GFZ Potsdam)
V.M. Pusenkov, V.A. Ulyanov (PNPI Gatchina)
A.I. Ioffe (FZ Jülich)
V.V. Zhuravlov, A.V. Churakov, A.A. Bogdsel, S.A. Manoshine, S.A. Kulikov & E.P. Shabalin (JINR Dubna)
the BMBF Germany and the FLNP Dubna for support
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