CENTRO ATOMICO BARILOCHE - ARGENTINA. MODELING AND MEASUREMENTS OF NEUTRONIC PROPERTIES OF NEW...

CENTRO ATOMICO BARILOCHE - ARGENTINA

MODELING AND MEASUREMENTS OF

NEUTRONIC PROPERTIES OF NEW CRYOGENIC

NEUTRON MODERATORS


J.R. Granada, F. Cantargi, S. Petriw, J. DawidowskiCentro Atómico Bariloche

Comisión Nacional de Energía Atómica & CONICET

ARGENTINA


NyR - SOME RESEARCH ACTIVITIES

Total Cross Section Measurement and Calculation (subthermal to epithermal range) [+T]

Neutron Diffraction [+T]

Deep Inelastic Neutron Scattering [+T]

Non Destructive Hydrogen Content Determination

Scattering Kernels for Hydrogeneous Materials


Scattering Kernels for Hydrogeneous Materials

Previous Related Experience:

THE SYNTHETIC SCATTERING FUNCTION

[J.R. Granada, Phys.Rev. B 31, 4167 (1985)]

0 20 40 60 80 100 120 1400

2

4

6

8

10

12

14

16

Multiple

Single

H2O

Cro

ss S

ectio

n (b

arn/

ster

ad)

Angle (degrees)

ANGULAR DISTRIBUTIONSExperiment performed at the Orphee reactor (λ=0.7045 Ả)

TOTAL CROSS SECTIONSLight water and plexiglass

at room temperature

1E-3 0.01 0.1 1 10

20

30

40

50

60708090

100

200

300

(%10)

PMMA

H2O

Tot

al C

ross

Sec

tion

(bar

n)

Energy (eV)

0.00 0.02 0.04 0.06 0.08 0.100.0

5.0x103

1.0x104

1.5x104

2.0x104

D2O

SSF M.G. Silk J.W. Daughtry H.J. Jones F.R. Westfall N.G. Sjöstrand

Dec

ay C

onst

ant (

s-1)

Buckling (cm-2)

DIFFUSION PARAMETERSPulse decay time for a

traditional “Hokkaido configuration”

DIFFUSION PARAMETERSDecay constant of heavy water

at room temperature

0 2 4 6 8 100

50

100

150

200

250

300

TD = 124.8 s

Kiyanagi et al., NIM A312, 561 (1992)

(12x12x5)

H2 Decoupled

CH4 Decoupled

H2 Coupled

Dec

ay T

ime

(se

c)

Wavelength (Å)

J.Nucl.Mat. 139, 158 (1986)

Multiple scattering corrections to the observed spectra

(MARI experiment)

Phys.Rev. B 58, 706 (1998)


1E-3 0.01 0.1 120

40

60

80

100

120

140160180200

CH4

GRANADA - CAB Nov. '94

Melkonian (293K) Rogalska (105K) SM (105K) NJOY (100k) SM (293K)

Cro

ss S

ect

ion

(b

arn

)

Energy (eV)

1020

3040

1020

3040

50

1

10

100

1020

3040

1020

3040

50

1

10

100

NJOY/ENDF/B-VI.2NJOY/Synthetic Model

Inci

dent

Inci

dent

Final

Solid Methane - 20K

Final

SYNTHETIC SCATTERING KERNELSPhys.Rev. B 31, 4167 (1985)


1E-4 1E-3 0.01 0.1 1

100

150

200

250

300

350

(*) Grieger et al., J.Chem.Phys. 109,3161 (1998)

SOLID METHANE(ca 20K)

Exper.(*) NJOY NyR

4H-C

ross

Sec

tion

(b)

Energy (eV)


Cross sections calculated through ‘synthetic model’ compared with exp. data at different temperatures

Cryogenic Moderators

10-5 10-4 10-3 10-2 10-1 1000.1

1

10

100

p-H2

n-H2

SSF ENDF/B-VI Expt.

Tot

al C

ross

Sec

tion

(bar

n)

Energy (eV)


Development of New Cold Neutron Moderators

(Main objective of the ACoM collaboration)

SCATTERING KERNELS FOR ADVANCEDMODERATOR MATERIALS


NJOY Calculations

Synthetic Frequency Spectrum

Combination of experimental and synthetic contributions

Continuous part associated to traslational and rotational motions of the molecular system

Vibrational modes (discretes)

NJOY

•(library ENDF)• scattering•mass•Scattering proc• SFS

Gaussian approx.

100 phonons

S(Q)[SFS]

LEAPR

S(Q)[SFS]

(E)kernels[SFS]

integrals libraryACE[SFS]

THERMR ACER

Solid Methane: applications of the SFS concept

0.0001 0.001 0.01 0.1 1

100

1000

10000

100000

Espectro de neutrones(MCNP)Metano Sólido a 22K

[E

]

E [eV]

HB SFS (biblio MCNP)

Solid Methane: using SFS

Neutron spectra at different temps calculated with MCNP Neutron spectra at different temps calculated with MCNP using SFS´based libraries.using SFS´based libraries.

0.001 0.01 0.1 1

100

1000

10000

100000

Espectro de neutrones (MCNP)Metano sólidoBibliotecas a partir del SFS

[E

]

E [eV]

22K 30K 50K 77K

Light Water Ice

Cross Sections obtained from SFS

1x10-4 1x10-3 1x10-2 1x10-1 1x100

0.1

1

10

Inelástica

Hielo

Se

cció

n E

fica

z [b

arn

s]

E [eV]

115K 77K 50K 30K 20K

10-2 10-1 100

20

30

40

50

60

70

80

90

100

Hielo

Se

cció

n E

fica

z [b

arn

s]

E [eV]

Experimental 115K Total SFS 115K

Clathrate

Neutron X-sections and spectra calculated with the use of a Synth. Frequency Spectrum

1x10-4 1x10-3 1x10-2 1x10-1 1x100

2.5

25

Clatrato (SFS)

Se

cció

n E

fica

z [b

arn

s]

E [eV]

Inelástica 20K Inelástica 30K Inelástica 50K Inelástica 77K

10-3 10-2 10-1

100

1000

10000

Espectro de neutrones (MCNP)Clatrato (SFS)

[E

]

E [eV]

20K 30K 50K 77K

Clathrate

10-3 10-2 10-1 100

1000

10000

100000

Espectro de neutrones (MCNP)20K

[E

]

E [eV]

Clatrato Hielo Metano

Clathrate, Methane and Ice at 20K

Cross sections calculated through ‘synthetic model’ compared with exp. data at different temperatures


Neutron spectra from moderator substances at different temperatures (calculated)


10-4 10-3 10-2 10-1 100 101

Neu

tron

flu

x [a

.u.]

E [eV]

Methane 22K Para-hydrogen 20 K Mesitylene 20 K

Calculated spectra of typical cryogenic moderators for the “Hokkaido Configuration”


SCATTERING KERNELS FOR ADVANCEDMODERATOR MATERIALS

Latest Development of New Cold Neutron Moderators


Neutron Scattering Kernel for Solid Methane in phase II

Rolando Granada

Centro Atomico Bariloche

ARGENTINA


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 (also referred to as the outer and inner terms, respectively).

The intermediate scattering function is

tiiaa

tiiaat

lvlvl

lvlvvv

vllvll

vllvvv

´´*

´,

´´´

´´*

´,

.exp0.exp

.exp0.exp,

RQRQ

RQRQQ

tiiaaedtS vllvll

vllvvv

ti´´

´,´´

*

´,

.exp0.exp2

1, RQRQQ


'

22

222intra

1

.3

,

HHHHH

iHc

HHHi

HcCC

Cc

fSS

bb

fbbgfbt

SS

Q

Carbon self Hydrogen self

Interference caused by Proton spin correlations

gГ = 1 for disordered molecules

= 3 for ordered molecules


1E-4 1E-3 0.01 0.1 1

100

200

300

400

To

tal C

ros

s S

ec

tio

n (

ba

rn)

E (eV)

Elast.self Elast. all Inelast. Total

4K

Calculated components of σT(E) for CH4 II at 4KCH4 II


1E-4 1E-3 0.01

200

400

600

800

To

tal C

ros

s S

ec

tio

n (

ba

rn)

E (eV)

0.3K

10K

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

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

CH4 II


0.1 1 10

300

400

500

600

To

tal C

ros

s S

ec

tio

n (

ba

rn)

T (K)

1.5 meV

0.9 meV 0.1 meV

Temperature dependence of σT at low energies caused by spin correlations

Open circles: this workClosed circl.: Grieger exper.Lines: Ozaki calculations

CH4 II


1E-3 0.01 0.1 1

1E-6

1E-5

1E-4

Ne

utr

on

Flu

x (

au

)

E (eV)

Meth 22K Meth 4K


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

Centro Atomico Bariloche

ARGENTINA


• Good moderator for a cold neutron source good resistance to radiation (S.Kulikov, E. Shabalin, V. Melikhov, E. Kulagin, Proceedings of the ICANS-XVI Meeting, Neuss, Germany, 2003)

high protonic density low-energy excitations (I. Natkaniec, Proceedings of the ACoM6 Meeting, ESS-FZ Julich, 2002)

easy handling

MESITYLENE


0.00 0.02 0.04 0.06 0.08 0.100

2

4

6

8

10

12

Z(E

) (a

u))

E (eV)

Phase I Phase II Phase III

MESITYLENE

Low energy part of ouradopted SFS


1E-3 0.01 0.1 1200

400

600

800

1000

1200

To

tal

Cro

ss

Se

cti

on

(b

arn

s)

E (eV)

Experim. Calcul.

MESITYLENE32K

(Phase III)

Experiments using the Bariloche LINAC


1E-3 0.01 0.1 1200

400

600

800

1000

To

tal

Cro

ss

Se

cti

on

(b

arn

s)

E (eV)

Experim. Calcul.

MESI (3:2) TOL32 K

Experiments using the Bariloche LINAC


1E-3 0.01 0.11E-6

1E-5

Ne

utr

on

Flu

x

E (eV)

Benzene Toluene Mesityl ph II Mesityl ph III Mesi (3:2) Tol

20 K

Calculated Spectra for the Methyl derivatives of Benzene


1E-3 0.01 0.1 11E-7

1E-6

1E-5

1E-4

Neu

tro

n F

lux

E (eV)

Methane ph I Clathrate Mesitylene ph II Mesi (3:2) Tol Para hydrogen

20 K

Comparison of Mesitylene and Mixture with standard moderators


Thank you!

25 MeV e-LINAC

LINAC

Bunker Experimental room

Scattering Experiments

Detector bank

Sample changer

P b n

n

e-

WATER

25 MeV e-LINAC

73 cm total height; 50 cm diameter; 38 cm moderator height. Stainless steel. Zircaloy-4 windows


Cryo-Moderator contained in succession of zircalloy-4 containers


19,6cm20,2cm

5 cm

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