Neutron Scattering

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get as heat, the rest is transported as released radiation to the target vicinity like moderators, reflector and shielding or is converted into nuclear binding energy . Secondly, all materials bit by protons (and fast neutrons) will suffer from radiation damage. Finally, the extremely short proton pulses generate shock-like pressure waves in target and structural materials, which may substantially reduce the target seivice life. In order to both keep average target temperaturcs low and reduce specific radiation damage and loads due to dynamic effects from shock waves, a solid rotating target is conceivable and bas been proposed for the ESS . As any solid target has to be cooled, it will inevitably be "diluted" by the coolant, whereby the primary source's luminosity will be diminished . One should therefore operate the target in its liquid state avoiding an additional cooling medium. Radiation damage would be no longer a problem wich the target, but of course with its container . Obviously, the refractoiy metals are excluded due to their high melting points. So we are left with elements like lead, bismuth, the Pb-Bi eutectic or - of course - mercury . In tact, mercury has been chosen for the ESS, because it was also shown to exhibit favorable neutron yield conditions as presented in Figure 1 .4 . Fig. 1 .4 Calculated axial leakage distributions offast neutronsfrom a lead-nefected mercury target compared to waten cooled tantalum and tungsten targets, respectively . The dimensions of a target along the beam path will reasonably be chosen according to the range of the protons of given kinetic energy . For mercury and the ESS energy of 1 .33 GeV this is about 70 cm . Lateral target dimensions are optimized so that the moderators are not too far from the proton beam axis (solid angle!) . A typical target-moderator-reflector configuration is depicted schematically in Figure 1 .5 .
neutron beann channels Fi 1 .5 Schematic vertical and horizontal cuts through the innerpart ofthe target block. 1 .5.2.3 The moderators We will now turn to the "heart" ofthe facility, the moderators, which were just shown in the last figure above in their relative positions next to the target . As the upper and lower faces of the target are equivalent for symmetry reasons with respect to the emission of fast neutrons, it is obvious to exploit both sides with moderators . The question now is, whether we shall use D 20 as the slowing down medium like in all modern medium and high flux reactors or possibly H2O? As we have discussed in section 1 .4, not the highest possible average neutron flux is the only reasonable demand, but rather the highest possible peak flux for a given (or requested) average flux . In that respect, H2O is the preferred material due to its bigger slowing 1-10
Page 1 and 2: Forschungszentrum Jülich in der He
Page 4 and 5: Forschungszentrum Jülich GmbH Inst
Page 6: Contents . . 1 Neutron Sources H .
Page 10 and 11: 1 . Neutron Sources Harald Conrad 1
Page 12 and 13: d) f, = v a, , q - ti = P a, - 0 .3
Page 14 and 15: Period Example Flux (D [1013 1950-6
Page 16 and 17: In stage 1 the primary proton knock
Page 20 and 21: down power and stronger absorption
Page 22 and 23: Appendix Neutron Sources - an overv
Page 24: led remotely. It is rauch more conv
Page 28 and 29: 2 . Properties of the neutron, elem
Page 30 and 31: In the 60's the ferst high flux rea
Page 32 and 33: Hot neutrons in reactors are obtain
Page 34 and 35: elated values for the FRJ-2 reactor
Page 36 and 37: 2 .5 Scattering amplitude and cross
Page 38 and 39: (A+k2 ) yr = u(Z:) yr V( u~r)= z "
Page 40 and 41: _du _ mn \2 A2-~2z r2~ I(k' IVI k)I
Page 42 and 43: E ô ô x z w 0 z _w U N Figure 2 .
Page 44 and 45: scattering is observed with the ave
Page 46 and 47: For a spherical electron distributi
Page 48: A more thorough introduction to neu
Page 52 and 53: 3 . Elastie Seattering from Many-Bo
Page 54 and 55: Q = Q = k2 + k2 - 2kk' cos2B (3 .3)
Page 56 and 57: 3 .2 Fundamental Scattering Theory
Page 58 and 59: The meaning of (3 .l4) is immediate
Page 60 and 61: 1 . e. in the second approximation,
Page 62 and 63: The saure problem will bc dealt wit
Page 64 and 65: ALQ) = Y-bfe'Q'-rB(r-(n .a+m .b+p»
Page 66 and 67: du LQ) = ALQJ2 = e'Q .A' . * -i e-
Page 68 and 69:
Tab . 3.1 : The scattering lengths
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We note immediately that we should
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These magnetic structures can be un
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M1LQ)=Q-MQ)xQ M(Q)= IM (r)e i Q " d
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Orbital magnetic spin angular ,,- m
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aQ . r 3 àQ . N . QR . aQ .t k _ML
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Schweika Analysis Polarization W .
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ducing a complex component and were
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ir v s ftft 3956 2 s 2 0.81[X] 80 c
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Some polarizers using Bragg reflect
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Different to the coherent nuclear s
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where QBG denotes the background .
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4 .4 Applications We now consider e
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Fig. 4 .3 .4 probably represents th
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. occur only in the non-spin flip c
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The results for the magnetization d
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a large solid angle with polarizers
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scattering to spin-flip scattering
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An experimental verification of thi
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Correlation Functions Measured by S
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In real liquids however usually an
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The term in big parentheses of equa
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4 0 -5 0 5 10 15 20 ho) [meV] Figur
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Figure 5 .5 : The pair correlation
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Figure 5 .6 : Partial differential
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Then equation (5 .21) can be conver
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The route from expression (5 .27) t
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In addition it is often useful to d
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2 . The pair correlation function h
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G(r, t) G(r, t) i(Q, t) r Q i(Q, t)
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Insertion of this result into (5 .6
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With this example we can also demon
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6. Continuum description : Grazing
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Starting point is the exact atomic
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For specular reflectivity measureme
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v v z l 2r V(z) = 2 -2erfC~ with er
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F{dV(z)/dz ) to calculate the refle
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Equation (6 .13) also shows that th
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ut is completely reflected . The cr
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0.4° . The full dynamical theory c
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1) If no magnetic induction B (whic
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Diffractometer Gernot Heger
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select a special wavelengths band (
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" The direction of the reciprocal l
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Bragg-intensities of single crystal
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monochromator, on the mosaic spread
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complex sample environments, such a
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the diffraction plane) two further
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Small-angle Scattering and Reflecto
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L= (1) ( k ) a e -(k/k T ) 2 Ak (8
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possible neutron wave lengths betwe
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figure and with neutrons of about 1
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1 .0 Danvinkurve 0 .8 0 .6 0 .4 0 .
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tails. This reflection curve leads
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For the Nickel film one gets a thic
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I The rotor of a velocity selector
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multiplier are arranged in a quadra
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9 . Crystal spectrometer : triple-a
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machine which will be followed by a
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10 .3 Beaur shaping Due to the fact
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G.k=zGz . (11) This case is fulfill
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tribution of bisecting planes (ntos
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directions which is exploited for t
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Fig . 14) Dispersion surfaces for B
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whereby E and v,, denote energy and
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[1] B . N. Brockhouse, in Inelastic
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10 . Time-of-flight spectrometers M
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Tnloderator /K V7 2/m/s A/nm Aiw/eV
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10.2 .1 Interpretation of spectra A
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----~ Probe ' (Chopper 2) Zeit I Ch
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the similar intensity distribution
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is performed without Jacobian due t
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10.2 .6 Crystal monochromators The
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larger energy transfers . However i
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10.3 Inverted TOF-spectrometer In t
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constant offset to the TOF . To be
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sample size of cm and a detection p
Page 232:
Contents 10 .1 Introduction . . . .
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11 . Neutron spin-echo spectrometer
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2 0 L Tr -0 L 2 ArDet Figure 11 .1
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initial velocity-reassemble at the
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distribution (current sheets) that
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esults, where il is an irrelevant c
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10000 - 8000 - co 6000 - C ô 4000-
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e0 oX n .5 1 .0 1 .5 so 0 .0 0 .0 1
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nel" coils) the required homogeneit
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Figure 11 .9 : S(Q, t)IS(Q) of a 2
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Contents 11 .1 Introduction . . . .
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12 . Structure determination G . He
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Important: Thc measured Bragg inten
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determination of accurate atomic pa
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The knowledge of the overall occupa
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(even anharmonic) effects. This com
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Fig . 4 . Coordination ofthe D20 mo
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fenoelectric phase of orthorhombic
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(c) and (d) calculated densities at
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13 Inelastic Neutron Scattering Pho
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Figurel Schematical drawing of a ge
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equilibrium position the atom is in
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s - ' f N .mwn .I )oo K L .~um..un
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esults from the quantum mechanics o
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y absorption . 13 .1 .3 Magnetic in
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Figure 7 The plane in reciprocal sp
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5 100s1 [OSl ] IOSSI [SSS y i 4 0 r
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dynamics of ionic compounds with th
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16 14 12 F.. . 10 ô 8 q 6 cr 4 G.
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21 [ooç 1 " - 19 18 17 16 "" 298 K
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n = v - cap[i(pga . - wt)] (13 .22)
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Y c 3 c Cc E Figure 16 Magnon dispe
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. . 2 H . Bilz and W . Kress, Phono
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14 . Soft Matter : Structure Dietma
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length density of a sample against
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2 P(Q) = 1 ~exp(-Ii - j'6 Q2 ) (14
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fraction. In the region of large Q
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with the partial structure factor S
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and which lead to the scattering cr
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For the intramolecular and intermol
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500 450 -400 U 0 ;, 350 42, 300 s~.
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scaling behavior of the susceptibil
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15 Polymer Dynamics Dieter Richter
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constraints due to the mutual inter
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(15 .3) T ß ( E)=T ô exp E k,T -
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This incoherent approximation does
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10 an 0 2 0 Figure 15.4 : Relaxatio
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In order to test Eq .[15 .9] the re
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Arrhenius temperature dependence wi
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1 3kBT ~ z 2 72 2 p2 a = f2 N2 P =W
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S (Q,t) = 12 fdu exp ~ -u_ (S2Rt) v
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We now use these data, in order to
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c 0 .8 0 .6 00 .055 x 0 .1 110 .14
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small but systematic deviations fro
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S(Q,t) is predicted . Such a platea
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only one single parameter, the tube
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confinement of the relaxation of la
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16 Magnetism Thomas Brückel
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the ground state of metallic magnet
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c~ ~ o 0 `,~i) g',, b o 0 Q! b o 0
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only "sec" this component and not t
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200 ¬ 400 500 600 700 E 3 QI J (h0
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Fie. 16.4: Scattering geometry for
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0 .8 ' D3 ° Stassis 3d spin - - 3d
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Here, J;j denotes the exchange cons
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Fig. 16.8 : Contour plot of the mag
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0.0001 0.001 0 .01 0.1 2 Fig. 16 .1
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17 Translation and Rotation M . Pra
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17.1 Introduction Atomic and molecu
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17 .2.2 Diffusion, microscopic appr
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0.6 H20 2 x2tÄ z ) Figure 17 .2 :
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The scattering function of a polycr
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e (2) 1 (j 1, 0 > - 0,1 >), respect
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leads to the eigenvalue problem ~q
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allow a good determination of the E
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m Eu W Figure 17 .7 : Eigenenergies
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-so o so Energy transfer (NeV) Ener
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Bibliography [1] T. Springer, Quasi
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18 . Texture in Materials and Earth
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Further important structure related
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The axes of the cartesian Kp coordi
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4.0 Experimental Texture Analysis T
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Fig. 18.14: Variation of reflection
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measurements can be performed in tr
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Apart from the global description o
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In the following, two experimental
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The neutron diffraction pole figure
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dependent pole densities, and (4) g
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Schriften des Forschungszentrums J
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Forschungszentrum Jülich in der He
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Neutron Scattering

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