Antonín Krása, Mitja Majerle

for the Energy plus Transmutation Energy plus Transmutation collaboration

Neutron Production in Spallation Neutron Production in Spallation Reactions Reactions

ofof p+Pb, d+Pb at p+Pb, d+Pb at GeV EnergiesGeV Energies(Experiment versus Monte Carlo simula(Experiment versus Monte Carlo simulationtion))

OutlineOutline

• Motivation • Performed experiments• Energy + Transmutation setup• Monte-Carlo simulations• Neutron spectra

• Low-energy region (activation foils)• Intermediate region (activation foils)• High-energy region (SSNTD)

• Sources of differences experiment × simulations

Motivation and Motivation and TTasksasks

• Experimental data for testing the codes for simulation of neutron production and transport in ADT systems

• Measurement of neutron field produced in irradiation of:

• thick target,

• thick target + moderator,

• thick target + fissionable blanket + moderator

with relativistic protons and deuterons

• Comparison: experimental × Monte-Carlo simulations check accuracy of nuclear models and x-section libraries

Experiments onExperiments on thick target (+ thick target (+ moderator)moderator)

.

Beam energy [GeV]

YearIrradiation time [h:m]

Integral beam flux

[1013]Setup Accelerator

1.5 1998 8:35 8.9Pb target

Synchro-phasotron

W target

0.885 1999 2:03 3.46Pb target + moderator

1.3 2000 3:17 2.77

Pb target2.5 2000 2:02 4.07

0.66 2003 0:10 158 Pb target Phasotron

Phasotron setup 660 MeVPhasotron setup 660 MeV

Synchrophasotron setup 885 MeVSynchrophasotron setup 885 MeV

Beam energy [GeV]

Beam particles

YearIrradiation time [h:m]

Integral beam flux

[1013]Set-up Accelerator

0.7

protons

2004 8:51 1.47

Pb-target

+

U-blanket

+

(CH2)n-

moderator

Nuclotron

1.0 2003 6:03 3.26

1.5 2001 12:03 1.14

2.0 2003 7:43 1.25

2.52

deuterons

2005 8:00 0.64

1.6 2006 6:46

ExperimentExperimentss onon Energ Energyy+Transmuta+Transmutation tion setupsetup

ENERGY ENERGY ++ TRANSMUTATION setup TRANSMUTATION setup

• target: Pb (28.66 kg) • blanket: U (206.4 kg)• shielding: Cd + (CH2)n

Measurement of Measurement of activated foilsactivated foils

TypeEnergy resolution (FWHM of 60Co at

1332keV)

Relative efficiency

Amplifier ADC

ORTECcoaxial

GR-1819-7600SL

1.90 keV 28.3 %CANBERRA

2026

ORTEC 919 SPECTRUM

MASTER

• High Purity Germanium -spectrometer

Spatial Spatial distributions of distributions of

yields in yields in Al- and Au-foilsAl- and Au-foils

• Example of yields at 1.5 GeV proton

irradiation of E+T setup

Monte-Carlo simulationsMonte-Carlo simulations

Description of U/Pb assembly in MCNPX

• MCNPX 2.6.C• FLUKA

Produced neutron spectrum

• Spallation produces neutrons with keV-GeV energies

• (n,)-reaction covers neutrons with energies up to MeV

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2 1E+4

Energy [MeV]

Nn

eu

tro

ns [

cm-2

pro

ton

-1] target-blanket

tb+box+Cd

1E-5

1E-3

1E-1

1E+1

1E+3

1E+5

1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2 1E+4

Neutron energy [MeV]

XS

[b

arn

s]

n,gamma

n,xn

n,fission

n,g n,x n n,f

MCNPX simulation of activation reaction MCNPX simulation of activation reaction yieldsyields

Compilation of total neutron yields for Compilation of total neutron yields for p,d+Pbp,d+Pb

1E-5

1E-3

1E-1

1E+1

1E+3

1E+5

1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2 1E+4

Neutron energy [MeV]

XS

[b

arn

s]

n,gamma

n,xn

n,fission

n,g n,x n n,f

Activation detectors

SSNTD

Detectors

• Activation detectors :– 197Au(n,xn)197-x+1Au– Bi, Al, Co, Ta, In– Gamma spectrometry

• Solid State Nuclear Track Detectors :– natPb, natU, 235U + mica foils where fission

fragments leave their tracks– Optical microscopy

Results – Phasotron experiment660 MeV, bare, lead target

0

0.5

1

1.5

2

2.5

3

3.5

4

0 10 20 30 40 50

Distance along the target [cm]

Rat

io e

xp/s

im Au-198Au-196Au-194Na-24

1E-08

1E-07

1E-06

1E-05

1E-04

0 10 20 30 40 50

Distance along the target [cm]

B [g

-1 pr

oton

-1]

Au-198

Au-196

Au-194

Na-24

Experiment Experiment/simulation

Energy Plus Transmutation

• Au detectors– Longitudinal– Radial in the first gap

• SSNTD– Radial in all gaps

Results – EPT, 1 GeV protons

0

1

2

3

4

5

0 5 10 15

Radial distance [cm]

Bex

p/B

sim Au-196

Au-194Au-193Au-192

Results – EPT, 1.5 GeV protons

0

1

2

3

4

5

0 5 10 15

Radial distance [cm]

Bex

p/B

sim

Au-196Au-194Au-193Au-192Au-191

Discrepancies

• Disagreement – 1.5 GeV– 2 GeV bigger– 2.52 GeV deuterons – zero ?!

• Only in radial direction• Only for threshold detectors, SSNTD are ok• Causes :

– Experimental error – Simulations

Experimental error ?

• Systematic uncertainties were studied carefully with sets of MCNPX simulations, they are limited to ca. 30% (foil displacement, beam determination)

• Transport of activated material out of foil is below 5%

• Spectrometry – 5%

• … ?

Simulation errors ?• Spallation :

– INC (E>160 MeV), – pre-equilibrium (160MeV>E>40MeV), – evaporation(40 MeV>E).

• Transport of HE neutrons in uranium blanket• More tests:

– Analysis of Yurevich experiments (angular spallation neutron distribution, Ep>1.5 GeV)

– EPT experiment without blanket at 1.5 GeV or 2 GeV– Repeat 1 experiment (1.5 GeV or 2 GeV)

Results – EPT, 1.5 GeV protonsFLUKA code - preliminary

0

1

2

3

4

5

0 5 10 15

Radial distance [cm]

Bex

p/B

sim

Au-196Au-194Au-193Au-192Au-191

0

1

2

3

4

5

0 5 10 15

Radial distance [cm]

Bex

p/B

sim

Au-196Au-194Au-193Au-192Au-191