eV neutron WS at ICANS2005 Trial of eV Neutron Diffraction KEK M.Arai & T.Yokoo 1) Diffraction on highly absorbing materials K.Kuwahara, M.Kohgi Tokyo Cosm.U 2) Diffraction on pulsed high magnetic field H.Nojiri, M.Motokawa Tohoku Univ 3) Use of resonance effects (Breit-Wigner) (extracting partial structure factor) Y.Kawakita, S.Takeda Kyushu Univ. 4) Use of energy dependent cross-section (recoil effects, potential energy, energy contrast) T.Yokoo , K.Iwasa KEK 5) Pilot Instrument for epithermal neutrons (EXCED) T.Yokoo KEK Y.Inamura Univ. Tokyo M.Nakamura JAERI
eV neutron WS at ICANS2005 EXCED at KENS (designed for single crystal diffraction) L 1 =6.4m, L 2 =3m Collimation Δθ =0.1° -5° < 2 θ small < 10°, Δ d/d=0.1 37°< 2 θ high < 95°, Δ d/d=0.01 2meV < Ei < 100eV 1.4+1.6m Steel Collimator high angle PSD L 1 =6.4m L 2 =3m small angle PSD (adjustable)
eV neutron WS at ICANS2005 Requirement on the instrument and detector 1) good collimation for epithermal neutron ---> 1.4 +1.6 m long steel ( σ ~11 barns) collimator section 2) high counting rate with good spatial resolution for epithermal neutrons --> 4 layers of 3 He-PSD (10atm, 60cm long, Δ r ~ 4mm, 4000 pixels, 70% at 1eV ) 3) low background --> Vacuum scattering tank with B 4 C layer Disadvantage of EXCED Lorentz factor ~ ( λ /Q) 2 Intensity decreases at small angle scattering for the same Q by using small λ !
eV neutron WS at ICANS2005 Resolution For magnetic scattering most Bragg peak appears at or < Q = 2 π /d ~ 1Å -1 dominant negligible with Ei = 2eV ( λ ~0.2Å) --> 2 θ ~2° (SANS with epithermal neutrons) 2 � d 2 + � � � 2 � � � ( ) = cot � �� � � � � � � d Δ d/d ~ 0.1 is required @ 2 θ ~2° --> Δθ =0.1° (good value for single crystal) Detector segment size is Δ r ~4mm (commercially available, cf. RS- 1/2”-60cm PSD) Hence, L 2 ~ 3m ---> Δθ = Δ r/2L 2 < 0.1°
eV neutron WS at ICANS2005 Detector system (RS 1/2” PSD) Intensity at each layer Four layered 3 He-1D-PSD(10atm) small angle bank detecting efficiency 70% for 1eV spatial resolution 4mm Pixel Segmentation keeps good spatial and time resolution high angle PSD bank
eV neutron WS at ICANS2005 LabView panel Bragg Peak appears at 4layers 4th layer at 1eV 3rd layer 2nd layer TOF 1st layer Angle Angle direct-beam background Slice along
B 4 C slit system eV neutron WS at ICANS2005 Sample gonio (top view) EXCED photoes Cryo-magnet (Oxford 7T) Scattering Tank(from behind)
eV neutron WS at ICANS2005 Diffraction on highly absorbing materials at Epithermal neutron region Cross-section as a function of energy ~@1eV *+,-./01 *+,-./01 2/-341 2/-341 5./661 5./661 7+8-9/0 7+8-9/0 ( !" :;!" 5< ' !" the absorption cross-section =<;!&( -/-3418./6616+8-9/0111?@3.06A 7>;!&! & !" decreases by 4 order of magnitude % !" $ !" # !" *+,-./01 20-+034-51 *+,-./01 20-+034-51 6-1 6-1 74-+8-/.1 74-+8-/.1 9/34-4/01 9/34-4/01 401 401 :;<:7 :;<:7 ! !" $! slowing down region ! ")"""! ")""! ")"! ")! ! !" *+,-./0120-+034-5111=6%,%> #" (Epithermal) B0+.CD111?+EA Neutron Intensity at a pulsed source #! Storage region high intensity " (Maxwellian, Thermal) at the epithermal region( 1Å< λ ) ! !%& #%' $%( )%$ ( (%& 0+,-./01?6@+1A+0B-C111=D>
eV neutron WS at ICANS2005 Example of measurement １） GdB6 understanding magnetic structure Ei=1.3eV 2 θ =2.6° without Quadru-pole interaction (in comparison with CeB6) ２） GdGa2 Magnetic structure and moment rotation to understand the phase diagram
eV neutron WS at ICANS2005 Development on pulsed high field magnets at KENS achieved 32T in 1998 It lasts 100,000 pulses. for Horizontal field for Vertical Field
eV neutron WS at ICANS2005 Capacitor Bank Specification Capacity 1.2mF Voltage(Vc) 10kV Current(I 3 ) 20kA Power 60kJ Time duration 1ms Time repetition 2s 2x2x4m 3 Dimension Time Averaged power 1kW(@1ms x 2s) (6 degree increase for 10litter/min cooling water) Ignitron 30 25 20 DC power B (T) 15 10 5 0 0 0.2 0.4 0.6 0.8 1 Time (msec)
eV neutron WS at ICANS2005 Neutron diffraction with pulsed field Bragg Peak = 2 sin � 1 ,-(./#*3(4#15$" !"#"$#%&4 � d !"#"$#%& L1+L2 2 � >1.5"#($*,("-3 L2 01)2-" 01)2-" L1 >1.5"# >1.5"# L1 6789: ;<= 0 ( � ) '()"*%+*,-(./# ?"@#&%5*0%@&$" Disadvantage Neutron production freq.; 20Hz Pulsed field freq.; 0.5Hz --> 1/40 of normal intensity
eV neutron WS at ICANS2005 CsCuCl3 Spin structure based on Quantum effect (Triangular structure with one-dimensional nature, spin=1/2) Spin structure and Bragg Peak intensity in Mag. Field 1.5 (1/3,1/3,0) Intensity of magnetic peaks Calc (1/3,1/3,0) (1/3,1/3,0.85) Calc(1/3,1/3,0.085) 1 0.5 0 0 5 10 15 20 25 30 Magnetic Field in Tesla
eV neutron WS at ICANS2005 Coverage of pulsed field EXCED Previous experiment Epithermal neutron at 2 θ =2° 10meV neutron at 2 θ =10° magnetic field profile 1ms 1ms Diffraction with epithermal neutron --> effectively broaden pulsed field (diffraction time range is very short) Remark: intensity reduction due to Lorentz factor at small angle
3 2 sigmaT(1) sigmaT(0) H n=0,1,2 5 4 Energy dependent cross-section 1 sum 0 4 3 2 1 0 sigmaT(2) eV neutron WS at ICANS2005 Potential Energy Cross-section with recoiling effect 2 ω o � � � � � t = � � � 0 x + ( n ) ω o � M � 1 � dxx n e � x � � � � � � � 4 E m n ! x � ( n ) n � � m n : E = n � � 0 1 + � � � � M mol [ ] 2 E 1 2 ± E � n � � 0 1 + � ' x ± ( n ) = m 1 2 { } ( ) 1 2 ( ) � � 0 1 + � ' M n=0 � � � � � � � � � t = � � � 0 � 4 mE M � � � 1 � exp � � � � � ( ) � � M � � 0 1 + � ' 2 � � 4 E m � � � � n=1 � � � t = � � � � 0 M [ ] ( ) � exp � x + ( ) � x � + 1 ( ) � exp � x � ( ) � x + + 1 � � � 4 E m E/ ω o
6000 6 1.2 10 4 1 10 8000 TiCrMo 4000 2000 0 4 8 2 10 12 Ti45Cr50Mo5Dx Intensity [a.u.] Q [A -1 ] Sirius (V)D TiCrMo(V)D 4 eV neutron WS at ICANS2005 (Hydrogen storage material) ・ <b>~0 for metal atoms →P eaks from H(D) only ・ Ti 0.45 Cr 0.45 Mo 0.1 D 1.8 (TCMD) ・ Hydrogen extaction Temperature ・ Ti 0.48 Cr 0.32 V 0.2 D 1.8 (TCVD) TCMD ~ 100 ˚C (32meV) TCVD ~ 200 ˚C (41meV) Powder sample (3g) M D
Normalized Intensity 8 10-125seg -1 ] Q [A Bragg peak intensity change with energy NOR_TCMD 10 6 T=24 K 4 2 3.5 2.5 1.5 0.5 16PSDs eV neutron WS at ICANS2005 1) Can it give energy landscape in various crystal directions from various Bragg diffractions ? (energy-surface observation from powder diffraction ?) 2) Gives Caution on powder diffraction analysis. 3) Can apply energy contrast variation ? 4) Importance of angle dispersive diffraction (energy dispersive analysis) ! (importance of continuous angle coverage of powder diffractometer)
2 -2 10 4 10 1 10 0 10 -1 10 10 -3 10 10 10 -1 10 0 10 1 10 2 109Ag elastic & absorption cross section elastic cross section absorption cross section 109Ag Cross Section [barn] Neutron Energy [eV] 3 eV neutron WS at ICANS2005 Breit-Wigner Cross-section (resonance scattering) Resonance Scattering Cross-section 2 � n ( E res � E i ) � s = 1 2 + � o 4( E res � E i ) 2 k Resonance Absorption Cross-section � n � � a = 1 o 2 + � 4( E res � E i ) 2 k o Extraction of partial structure factor 2 S ( Q ) = b A b A S AA ( Q ) + 2 b A b B S AB ( Q ) + b B b B S BB ( Q ) b If A-atom has a resonance scattering, S AA (Q) can be extracted.
5 2 2.5 3 3.5 4 4.5 5 1 3 1.5 4 10 領域A 領域C Intensity Q [A -1 ] 2 1 -1 1 C A B lambda [A] 109Ag Cross Section [barns] absorption cross section elastic cross section 109Ag elastic & absorption cross section (lambda) 0.1 0 4 10 3 10 2 10 1 10 10 eV neutron WS at ICANS2005 Example of Resonance Scattering (AgI)-(Ag 2 S)-(AgPO) 3 (super-ionic conductor) Ag-Ag correlation could be extracted At 2.5A -1 S(Q) of (AgI) x (Ag 2 S) x (AgPO 3 ) 1-2x glass Diffraction pattern observed by high-angle detector bank of SWAN X=0.33 X=0.23 X=0.17 S(Q) X=0.09 X=0.00 0 2 4 6 8 10 12 !"#$%&'( -1 ) Q (A ) !"#$ *+,-./0
eV neutron WS at ICANS2005 Summary 1) Epithermal neutron is usefule for highly absorbing materials 2) Epithermal neutron is very useful for pulsed field experiments. 3) Use Breit-Wigner cross-section to extract partial structure factor. 4) Use energy dependent cross-section to study recoil effects, potential energy landscape and could apply energy contrast
eV neutron WS at ICANS2005
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