Modeling and Measurement Of Neutronic Properties of New Cryogenic - - PowerPoint PPT Presentation

RC No. 14161 CENTRO ATOMICO BARILOCHE - ARGENTINA

Modeling and Measurement Of Neutronic Properties of New Cryogenic Neutron Moderators

Second Research Coordination Meeting of the Agency’s Coordinated Research Project on “Improved production and utilization of short pulsed, cold neutrons at low-medium energy spallation neutron sources”

Kuala Lumpur, Malaysia 02 – 04 July 2009

Neutron Physics Group Centro Atómico Bariloche Comisión Nacional de Energía Atómica ARGENTINA CENTRO ATOMICO BARILOCHE - ARGENTINA

Chief Scientific Investigator: José Rolando GRANADA Scientific Investigator: Javier Roberto SANTISTEBAN Collaborators: Javier DAWIDOWSKI, Florencia CANTARGI, Aureliano TARTAGLIONE, Sergio PETRIW, Jerónimo BLOSTEIN, Luis CAPARARO

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OUR TASK

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DETAILED WORK PLAN FOR COMING YEAR (05/08-05/09), INCLUDING PROPOSED METHODS OR TECHNIQUES: To complete the validation of the scattering kernels developed in the last year, through comparisons of their predictions with experimental

• data. The hydrogeneous materials involved are: toluene, mesytilene,

and mixtures of the two. MCNP calculations based on the new cross section libraries will be compared with measured spectra from those materials, at a few low temperatures.

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DETAILED WORK PLAN FOR COMING YEAR (05/08-05/09), INCLUDING PROPOSED METHODS OR TECHNIQUES (cont.) During this second year of the project, we will tackle the problem of describing the interaction of slow-neutrons with deuterated molecular solids, typically d-methane and d-mesitylene at vey low temperatures. Those materials are of primary interest as moderators for very- and ultra-cold neutrons, on account of their very small absorption cross sections and the expected shift in the excitation energies due to isotopic effects.

Cross Section Libraries NJOY Nuclear Data Processing System Neutron calculations (with MCNP) Structure and Dynamics of the system

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AROMATIC HYDROCARBONS

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[Nucl. Instr.Meth. B 267, 175 (2009)]

• According to the cooling rate it

can exist in three solid phases

MESITYLENE (C9H12)

• Phase III: cooling down at 2K/min
• Phases I and II: annealing process

is required

• Good radiation resistance

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• Availability of low-frequency rotational

modes related to methyl groups

MESITYLENE

0.00 0.02 0.04 0.06 0.08 5 10 15 20 25 30

E [eV] Z[E] [u.a.] Phase I Phase II Phase III

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Experimental information [Natkaniec et al., Proceedings of ICANS XVI, 2003]

Natkaniec et. al studied a solution of mesitylene and toluene in a fraction 3:2 by volume It solidifies in a glassy structure irrespective of the cooling rate or thermal treatment provides a frequency spectrum with low frequency modes

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0.00 0.02 0.04 0.06 0.08 0.10

Z (E) [u. a.] E [eV ] M esitylene:T oluene (3:2) T oluene (glassy phase)

M esitylene (phase II)

SOLUTION MESITYLENE : TOLUENE 3:2 by volume

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Experimental information [Natkaniec et al., Proceedings of ICANS XVI, 2003]

MEASUREMENTS

(performed at our lab using a pulsed neutron source) CENTRO ATOMICO BARILOCHE - ARGENTINA

0.001 0.01 0.1 1 10 100 300 600 900 1200 1500 Sección eficaz total [barns] E [eV]

(293 ± 2) K (89.45 ± 0.05) K

0.001 0.01 0.1 1 10 100 300 600 900 1200 1500

Sección eficaz total [barns] E [eV] (180.0 ± 0.5) K (120.0 ± 0.5) K (31.6 ± 0.5) K

0.001 0.01 0.1 1 10 100 200 400 600 800

Sección eficaz total [barns] E [eV] (120.0 ± 0.5) K (31.6 ± 0.5) K

0.001 0.01 0.1 1 10 100 300 600 900 1200

Sección eficaz total [barns] E [eV] (120.0 ± 0.5) K (31.6 ± 0.5) K

Mesitylene Mesitylene Toluene M:T 3:2

CROSS SECTION LIBRARIES: GENERATION AND VALIDATION

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[Nucl. Instr.Meth. B 267, 175 (2009)]

TOLUENE

1E-3 0.01 0.1 1 10 100 200 400 600 800 1000

Total Cross Section[barns] E [eV] Experimental NJOY calculation

T= 32 K

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1E-3 0.01 0.1 1 10 400 600 800 1000

Total cross section (barn) E [eV] Experimental NJOY Calculation

MESITYLENE T= 32 K

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1E-3 0.01 0.1 1 10 400 600 800 1000

Total cross section (barn) E [eV] Experimental Calculation

1E-3 0.01 0.1 1 10 400 600 800 1000 1200

Total cross section (barn) E [eV] Experimental Calculation

MIX 3:2 M:T

T= 120 K T= 32 K

0.001 0.01 0.1 1 10

• 7

10

• 6

10

• 5

10

• 4

2 4 6 8 10 2x10

• 5

3x10

• 5

4x10

• 5

5x10

• 5

6x10

• 5

7x10

• 5

8x10

• 5

9x10

• 5

10

• 4

φ (E)/ φo(E)

E [eV]

Methane phase I 22 K Mesitylene phase II 20 K Mix M:T 3:2 20 K Mesitylene phase III 20 K Toluene glassy phase 20 K Benzene phse I 20 K

E [meV]

SPECTRA CALCULATIONS at 20 K

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METHANE (CH4) – Phase II

• Simplest hydrocarbon
• Gas at room temperature
• Two solid crystalline phases
• Best H cold neutron producer
• Low radiation resistance

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Phase II : T < 20.4 K

[Nucl.Instr.Meth. B 266, 164 (2008)]

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The scattering law of a molecular system R lν(t) denotes the position of the atom v within the molecule l , can be written as the sum of inter (l ≠ l´)- and intra (l = l´)- molecular contributions. The intermediate scattering function is

( ) ( ) { } ( ) { } ( ) { } ( ) { }

t i i a a t i i a a t

lv lv l lv lv v v v l lv l l v l lv v v ´ ´ * ´ , ´ ´ ´ ´ ´ * ´ ,

. exp . exp . exp . exp , R Q R Q R Q R Q Q − + − =

∑∑ ∑∑

≠

χ

( ) ( ) { } ( ) { }

∫ ∑∑

∞ ∞ − −

− = t i i a a e dt S

v l lv l l v l lv v v t i ´ ´ ´ , ´ ´ * ´ ,

. exp . exp 2 1 , R Q R Q Q

ω

π ω h

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( )

( )

[ { (

) ( ) }

( )

( )

{

( ) (

) ( ) }[ ( ) ] ]

1 , 1 . 3 , 4 ,

' 2 2 2 2 2 intra

− + + + + + + ≅

Γ Γ Γ Γ

∑

Q S S Q Q

HH H H H i H c HH H i H c CC C c

f S S b b t f b b g f b t χ

( ) [ { (

) ( ) }

( ) {

( ) ( )

( ) } ( ) ( ) ]

ω δ ω ω

γ

h

2

2 2 2 2

4 3 , 4 ,

Q HH H i H c H i H c H

e Qr j T F b b S b b g S

Γ

− Γ Γ Γ Γ

+ + + + ≅ ∑ Q Q

• Convtnal. Incoher. Scatt. function

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1 2 3 4 4 6 8 10 10 20 30 40 50

y x

S(α,β)=(kBT/ħ) S(Q,ω)

α=ħ2Q2/2MkBT ~y β=ħω/kBT ~x

5K CENTRO ATOMICO BARILOCHE - ARGENTINA

1 2 3 4 5 10 20 30

Q (A

• 1)

dσ/dΩ|

int (barn/ster/molec)

10 K 7 K 4 K 2.6 K 1.4 K 0.3 K

The distinct differential cross section of CH4 II at several temperatures

( ) ( )

ω ω σ , Q

H

S k k d Q d d

∫

= Ω

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1 2 3 4 5

• 5

5 10 15 20 25

∆dσ/dΩ|

int (barn/ster/molec)

Q (A

• 1)

dσ/dΩ {T} - dσ/dΩ {10K}

(a) (b) (c) (d) (e)

Differential cross sections at several temperatures relative to that at 10K

a) 0.8K b) 1.4K c) 2.6K d) 7K e) 0.3K

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1E-4 1E-3 0.01 0.1 1 100 200 300 400

Total Cross Section (barn) E (eV)

Elast.self

• Elast. all

Inelast. Total 4K

Calculated components of σT(E) for CH4 II at 4K

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1E-4 1E-3 0.01 200 400 600 800

Total Cross Section (barn) E (eV)

0.3K 10K

Comparison of calculated σT(E) with experimental data of Grieger et al.

J.Chem.Phys.109,3161 (1998)

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0.1 1 10 300 400 500 600

Total Cross Section (barn) T (K)

1.5 meV 0.9 meV 0.1 meV

Temperature dependence of σT at low energies caused by spin correlations

White circles: this work Closed stars.: Grieger exper. Lines: Ozaki calculations

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1E-3 0.01 0.1 1 1E-6 1E-5 1E-4

Neutron Flux (au) E (eV) Meth 22K Meth 4K

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NEUTRON SCATTERING KERNEL FOR SOLID DEUTERIUM [EPL (Europhysics Letters), in press 2009]

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D2 Molecule

Formed by bosons → Symmetric total WF ψ(1,2) ≡ φ(R1, R2) χ(S1 ,S2 ) = ψ(2,1) Si = 1 ⇒ S = S1 + S2 = 0, 1, 2 Ortho states : S = 0, 2 & J = 0, 2, 4,.. Even AM Para states: S = 1 & J = 1, 3, 5,.. Odd AM

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( ) ( ) { } ( ) { } ( ) { } ( ) { }

t i b i b t i i t

v l v l lv lv l l v v l l

• ut

´ ´ ´ ´ * ´ ´ , ´

. exp . exp . . exp . exp , b Q b Q a Q a Q Q − − = ∑

∑

≠

χ

Id (Q,t) u (Q,t) Leaving aside for the moment the consideration of vibrational modes: There is no correlation between atoms belonging to different molecules, and then u(Q) = |Σν <blν exp{iQ.bν (0)}>|2 = 4 (bc )2 j0

2 (Qd/2)

∴ χout (Q,t) = 4 (bc )2 j0

2 (Qd/2) . Id (Q,t)

( ) ( ) { } ( ) { }

t i l JJ l l inner

J J

e J J Q f J A t i i t

) ( ' ' ' '´

'

) ' , ; ( ) ( . . exp . exp ,

ω ω ππ ππ ππ

χ

− −

∑ ∑ ∑

− = a Q a Q Q

Is (Q,t) v (Q,t)

Aee (J) = c { 4 bc

2 + 5/2 bi 2 } Pe (J)

Aoo (J) = (1-c) { 4 bc

2 + bi 2 } Po (J)

Aeo (J) = c 3/2 bi

2 Pe (J)

Aoe (J) = (1-c) 3 bi

2 Po (J)

c: o-D2 concentration fπ=π (Q;J,J’) = (2J+1) Σl even (2l+1) C2 (JlJ’;000) jl

2 (Qd/2)

fπ≠π (Q;J,J’) = (2J+1) Σl odd (2l+1) C2 (JlJ’;000) jl

2 (Qd/2)

∴ χinner (Q,t) = v(Q,t) . Is (Q,t) CENTRO ATOMICO BARILOCHE - ARGENTINA

CENTRO ATOMICO BARILOCHE - ARGENTINA I performed calculations using the NJOY code to evaluate the inelastic contributions to the cross section (with σ = σc + σi )

• The lattice density of states was taken from J.W.Schmidt et al.,

Phys.Rev.B 30, 6308 (1984);

• The rotational motion is computed according to the Young-Koppel

formalism;

• And the vibrational degree of freedom is also accounted for, with

a vibrational energy of 0.371 eV.

Under the hypothesis of polycrystalline solid, the elastic coherent component revealing the crystalline structure (hcp) was calculated with

• ur programme CRIPO.

The elastic incoherent component was taken directly from the NJOY result, renormalized by the factor σi /(σc + σi )

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2 4 6 8 10 0.00 0.05 0.10 0.15 0.20 0.25 0.30

Z(ω)

ω (meV)

Lattice DoS

J.W.Schmidt et al., Phys.Rev.B 30, 6308 (1984)

CENTRO ATOMICO BARILOCHE - ARGENTINA χinel(Q,t) = v(Q,t) . Is (Q,t) . χvib(Q,t) Total Inelast. χel(Q,0) = 4 bc

2 j0 2 (Qr/2) |F(Q)|2 χvib(Q,0) Convent.El.Coh

+ 2 (1+α) bi

2 χvib(Q,0) Total El.Incoh

The actual calculations are performed according to:

(α = ¼ for o-D2, - ½ for p-D2, 0 for n-D2)

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1E-5 1E-4 1E-3 0.01 0.1 1 0.01 0.1 1 10

Inelastic X-Section (b) Energy (eV) 18K 12k 8K 5k

• -D2

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1 2 3 4 5 6 7 8 9 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5

Total X-Section (b) Wavelength (A) 5K 8K 12K 18K

• -D2

PSI exp.

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6.6 6.8 7.0 7.2 7.4 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6

Total X-Section (b) Wavelength (A)

• -D2

PSI exp. 18K 12K 8K

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1E-3 0.01 0.1 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0

X-Section (b) Energy (eV) Seiffert 17K Model nD2 PSI 18K Model oD2

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σabs = 0.000577 λ(Å)

1000 2000 3000 4000 5000 6000 7000 0.01 0.1 1 10

Inelastic X-Sections (b) Wavelength (A)

5K

Pure Para Pure Ortho 0.015 Para (~ 4.2 % UCN losses) ´Real´ Ortho

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0.000 0.002 0.004 0.006 0.008 0.010 0.012 10 20 30 40 50 60 70 σ(E,E´)

E´(eV)

• D5k

pD5k E = 0.00001 eV

0.000 0.002 0.004 0.006 0.008 0.010 0.012 5 10 15 20 25 30

pD5k

• D5k

E´(eV)

σ(E,E´)

E = 0.0001 eV

0.000 0.005 0.010 0.015 5 10 15 20 25 30 35

pD5k

• D5k

E´(eV)

σ(E,E´)

E = 0.001 eV

0.000 0.005 0.010 0.015 50 100 150 200 250 300

pD12k

• D12k

E´(eV)

σ(E,E´) 0.000 0.005 0.010 0.015 20 40 60 80

pD12k

• D12k

E´(eV)

σ(E,E´) 0.000 0.005 0.010 0.015 0.020

20 40 60 80 pD12k

• D12k

E´(eV)

σ(E,E´)

5K 12K

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0.000 0.002 0.004 0.006 0.008 0.010 0.012 10 20 30 40 50 60 70 σ(E,E´)

E´(eV)

• D5k

pD5k E = 0.00001 eV

0.000 0.002 0.004 0.006 0.008 0.010 0.1 1 10 σ(E,E´)

E´(eV)

100% oD5k 98% oD5k E = 0.00001 eV

a b c a: 1 ph + 0 rot (J1→1 ) b: 0 ph + 1 rot (J1→0 ) c: -1 ph + 1 rot (J1→0 ) Upscattering increase due to 2% p-D2 ´contamination´

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• 40
• 30
• 20
• 10

10 20 30 0.0 1.0x10

• 4

2.0x10

• 4

3.0x10

• 4

4.0x10

• 4

β

S(α,β)

α = 1

S(α,β) for solid [98% ortho, 2% para] D2 at 5 K

1E-3 0.01 0.1 1 10 40 60 80 100 120 140

liquid, 290K solid, 32K

Total Cross Section (barn) Energy (eV) d-Mesitylene

Preliminary data for d-Mesi

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CENTRO ATOMICO BARILOCHE - ARGENTINA ►Cross section libraries of hydrogen bound in benzene, toluene, mesitylene and a solution 3:2 by volume of mesitylene/toluene were generated at different temperatures, in particular at 20K.

CONCLUSIONS

►The 3:2 mesitylene-toluene mixture, that forms in a simple and direct manner the appropriate disordered structure, constitutes an excellent cryogenic moderator material, as it is able to produce an intense flux of cold neutrons while presenting high resistance to radiation.

CENTRO ATOMICO BARILOCHE - ARGENTINA ► We developed a new scattering kernel for solid methane in phase II, including the main dynamical features of the system and the effect of spin correlations. ► Good agreement with a quantum mechanical calculation over the limited range where the latter was formulated, and with available experimental information over the complete thermal energy range.

CONCLUSIONS (cont.)

CENTRO ATOMICO BARILOCHE - ARGENTINA ► A new scattering kernel to describe the interaction of slow neutrons with solid Deuterium has been developed. ► Scattering functions and cross sections for both ortho- and para- Deuterium have been evaluated for temperatures ranging from the freezing point (18.7 K) down to 5 K. ► The new model has been compared with the best available experimental data, showing a highly satisfactory agreement.

CONCLUSIONS (cont.)

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1) "Experimental Neutron Data: Sigma(E) of Solid Benzene and Ice in the thermal range".

• L. Torres J.R.Granada and J.J. Blostein.

Nuclear Data Section, IAEA, EXFOR 31588 (2007). 2) “Synthetic Scattering Kernel for solid methane in phase II” J.R. Granada Nucl.Instr.Meth. B 266, 164 (2008). 3) “Neutron experiments with cryogenic methane hydrate and mesitylene moderators”

• K. N¨unighoff, et al.
• Eur. Phys. J. A 38, 115–123 (2008)

4) “Total cross section of solid mesitylene, toluene and a mixture of them at thermal neutron energies” L.A. Rodriguez Palomino, F. Cantargi, J.J. Blostein, J. Dawidowski and J.R. Granada Nuclear Instr.Meth. B 267, 175 (2009).

PUBLICATIONS PRODUCED WITHIN THIS RC

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5) “Neutron Scattering Kernel for solid Deuterium” J.R. Granada Eur.Phys.Lett. (in press, 2009). 6) “A Low-cost Moderator for Bragg Edge Transmission Analysis at Small Pulsed Sources”,

• J. Santisteban, A. Tartaglione, L. Torres, J.R. Granada, J.J. Blostein,

Journal of Physics: Conference Series. ISSN 1742-6588 (submitted) 7) “Stress analysis by Energy Dispersive Neutron Diffraction”

• J. R. Santisteban

in “Neutron and Synchrotron Radiation in Engineering Materials Science”, pp 155- 176,Editado por W. Reimers, A. R. Pyzalla, A. K. Schreyer, H. Clemens Wiley-VCH Verlag GmbH & Co, Weinheim, Germany (2008), ISBN:3-527-31533-0

PUBLICATIONS (cont.)

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8) “Neutron Scattering Kernel for Solid Methane in phase II”, J.R. Granada. International Collaboration on Advanced Neutron Sources, ICANS.XVIII, Dongguan, Guangdong, China (April 2007). 9) “Neutron Cross Section Libraries for Aromatic Systems of Interest as Cold Neutron Moderators”,

• F. Cantargi, J.R. Granada, L.A. Rodríguez Palomino, S. Petriw, M.M. Sbaffoni.

International Collaboration on Advanced Neutron Sources, ICANS.XVIII, Dongguan, Guangdong, China (April 2007). 10)“New Cross Section Libraries for Advanced Cold Neutron Moderators”, J.R. Granada, F. Cantargi, S. Petriw “International Workshop on Research Reactor Utilization: 50 Years of Safe and Sustainable Operation of the IEA-R1 Research Reactor”, Sao Paulo, Brazil (3-6 Dic. 2007).

CONTRIBUTIONS TO CONFERENCES

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11)“Generation of Cold Neutron Cross Sections for Advanced Moderators”, J.R. Granada, F. Cantargi, S. Petriw. International School-Seminar “Pulsed Advanced Neutron Sources - PANS III” Dubna, Russia (28/01-04/02 /2008). 12) “Neutron Cross Section Libraries for Cryogenic Aromatic Moderator Materials” Florencia Cantargi, J. R. Granada and María Mónica Sbaffoni International Conference on the Physics of Reactors, PHYSOR 08, Interlaken, Switzerland (14-19 Sept 2009). 13) “A Low-cost Moderator for Bragg Edge Transmission Analysis at Small Pulsed Sources”,

• J. Santisteban, A. Tartaglione, L. Torres, J.R. Granada, J.J. Blostein,

9th International Cenference on Neutron Scattering, Knoxville, Tennessee, USA 3 - 7 May 2009. 14) “Development of Cold Neutron Scattering Kernels for Advanced Moderators” J.R. Granada International Conference on “Neutron and X-Ray Scattering 2009”, Kuala Lumpur, Malaysia, 29 Jun - 1 July 2009.

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THANK YOU!

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