european physical society 19 th nuclear physics divisional conference new trends in nuclear physics...

European Physical Society19th Nuclear Physics Divisional Conference

New Trends in Nuclear Physics Applications and TechnologyPavia (Italy) September 5-9, 2005

EXPERIMENTAL STUDIES AND SIMULATIONS OF SPALLATION NEUTRON PRODUCTION ON A THICK LEAD TARGET

Mitja Majerle

NPI CAS

Řež, The Czech Republic

19th NPDC, Pavia (Italy), September 5-9, 2005

Introduction

Generally : Experiments with high-energy protons on heavy targets

(~ADS), spallation neutrons, direct beam We measure transmutation possibilities, neutron fields,

we compare data with model simulations

Focus – The PHASOTRON experiment : Protons, neutron field (threshold detectors) Transmutation of Iodine (short-lived isotopes)

... and the simulations What and how we calculate Comparison with the experiment The influence of the setup parts


•Neutrons and protons react with detectors: (n,), (n,2n), (n,xn), (n,), (p,n), (p,), ...

•Yields of produced elements are detectable in -detectors


Proton beam – 660 MeV, 10 min

The integral measured with two foils (Al,Cu) : 1,58·1015, accuracy 6%

Beam displacement (Al, Au, Bi foils): beam was shifted upwards - few mm

Reaction : (p,xn+yp), (p,), ...

Neutron field Al, Au, Bi foils Reactions : (n,xn), (n,), (n,) Spatial and energetic distribution of

spallation neutrons We do not see the whole spectrum !


Experimental results

27Al(n, )24Na

1E-08

1E-07

1E-06

1E-05

0 5 10 15 20 25 30 35 40 45

Distance along the target [cm]

B [

g-1

pro

ton

-1]

196Au(n,x)Au

1E-08

1E-07

1E-06

1E-05

1E-04

0 5 10 15 20 25 30 35 40 45


B [

g-1

pro

ton

-1]

Au-194

Au-196

Au-198

B=Number of produced nuclei in 1 g of material per one incident proton

207Bi(n,xn)Bi

1E-08

1E-07

1E-06

1E-05

0 10 20 30 40 50


B [

g-1

prot

on-1

] Bi-206

Bi-205

Bi-204

Bi-203

Bi-202

Bi-201


How do we get the neutron spectrum from that ?• We cannot ! Experimentaly we can get it with other types of detectors.

Calculated neutron spectrum

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E-7 1E-5 1E-3 1E-1 1E+1 1E+3

Energy [MeV]

Neu

tron

s pe

r in

cide

nt p

roto

n

Spectrum information only for regions

197Au(n,)198Au

197Au(n,2n)196Au

27Al(n,)24Na

• Our results are however important...

... for simulations.


Iodine samples 4 samples: 2×127I, 2×129I 129I - 90% of 129I, 10% of 127I During the experiment

~1/1011 part of the iodine nuclei transmuted

Chart explanation : 130I produced only in 129I Ratios of produced

elements are higher in 127I samples (on graphblue)

120I lower than expected – two isomers produced with almost the same lines, and only one is detected

Stable

=hours,days

=years

=minutes

(n,xn)+

127I and 129I samples at 9th cm

1E+06

1E+07

1E+08

1E+09

1E+10

I-130 I-128 I-126 I-124 I-123 I-121 I-120 I-119 I-118

Isotope

Nu

mb

er o

f p

rod

uce

d n

ucl

ei

i7n3i9n2


Simulations, how/what we calculate

MCNPX code v. 2.4.0 (on Linux, parallel computing)

Input : setup geometry starting conditions

Output 1: neutron distribution

Cross-section libraries (Au, Al - ENDF; Bi - experimental; Iodine - ?)

Output 2: masses of produced

elements or B-values


How do we get the neutron spectrum from that ?• We can convolute the calculated neutron spectrum with the cross-section for a given reaction (SSW+HTAPE3X+convolution).

Calculated neutron spectrum

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E-7 1E-5 1E-3 1E-1 1E+1 1E+3

Energy [MeV]

Neu

tron

s pe

r in

cide

nt p

roto

n

Spectrum information only for regions

197Au(n,)198Au

197Au(n,2n)196Au

27Al(n,)24Na

• Computer can convolute the spectrum with cross-sections and outputs B (F4+FM tally).


Calculations vs. experiment

B-values for Bi and I were not yet calculated (problem: cross-section libs)

27Al(n, )24Na

1E-8

1E-7

1E-6

1E-5

0 5 10 15 20 25 30 35 40 45


B [

g-1 p

roto

n-1]

experimental

simulation

27Al(n, )24Na

0,7

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

0 5 10 15 20 25 30 35 40 45


Ratio

197Au(n,2n)196Au

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

0 5 10 15 20 25 30 35 40 45


Ra

tio

197Au(n,4n)194Au

0,7

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

1,6

0 5 10 15 20 25 30 35 40 45


Ra

tio

Calculated values in comparison with the experiment for 27Al(n,)24Na

Ratios between calculated and

experimental values for 24Na, 196Au, 194Au


Influence of the setup parts

Concrete walls : Neutrons are

moderated and reflected back

197Au(n,)198Au

1E-8

1E-7

1E-6

1E-5

1E-4

0 5 10 15 20 25 30 35 40 45


B [g

-1 p

roto

n-1

]

experimentalno wallsHTAPE3XFM


Influence of other simplifications Extensive calculation tests on PHASOTRON and EPT setup

revealed that : HTAPE3X and F4 methods results do not always agree. Beam profile and displacement influence the neutron field (3 mm ~

5%). Detectors minimally influence the neutron field. Metal holders, tables, ... have minimal influence. ... and more.

The use of parallel processing (PVM) speeds up our calculations significantly.

2000

4000

6000

8000

0

10

20

30

40

50

60

70

80

90

0 2000 4000 6000 8000 10000

Accumulated processor power [MHz]

His

tori

es s

imu

late

d in

1 s

nps=2000k

nps=50k


Conclusion We try to imitate an ADS systems with the setup Experimentally : we get new data about transmutation rates (I,

(n,xn) reactions, others...) – precious in ADS design Calculations : it seems that we measure right things to test the

codes We can describe new, similar systems with the computer with the

accuracy (50%) Plans :

to finish analyzing the experimental data, to improve the accuracy of the calculations, try to recalculate all this with DCM (Dubna Cascade Model) code, probably another experiment on Phasotron, different setups...

Thank you.


Experiment data

Intensive beam (2,6·1013 protons/s) of protons with energy 660 MeV from Phasotron (http://phasotron.jinr.ru)

Date and time: 14th of December 2003 at 16:33 Pb target, without box to moderate fast neutrons The irradiation time : 10 minutes After another 10 minutes start of measurements

of I samples and foils on detectors ORTEC and CANBERRA

european physical society 19 th nuclear physics divisional conference new trends in nuclear physics...

Documents