Studies of neutron cross-sections by activation method in Nuclear Physics Institute Řež and in The Svedberg Laboratory Uppsala and experimental determination

Studies of neutron cross-sections by activation method in Nuclear Physics Institute Řež and in The

Svedberg Laboratory Uppsala and experimental determination of neutron production in spallation

reactions

Nuclear Physics Institute, Academy of Sciences of the Czech RepublicDzelepov Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, RussiaDepartment of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague

Varna, BulgariaVarna, Bulgaria 16.-22.9.201316.-22.9.2013

J. Vrzalová, O. Svoboda, A. Kugler, M. Suchopár, V. Wagner

collaboration Energy and Transmutation of Radioactive Waste

[email protected]

2

Introduction The collaboration Energy and Transmutation of

Radioactive Waste use different setups consisting of lead, natural uranium and graphite irradiated by relativistic protons and deuterons to study transmutation of radioactive materials by produced neutrons.

Activation samples are used to determine production of neutron flux in different places of experimental set-ups.

Unfortunately, the cross-sections of many reactions important for our activation detectors are missing.

To improve situation, we studied the neutron cross-sections using different quasi-monoenergetic neutron sources based on proton reaction on 7Li target in NPI Řež and in The Svedberg Laboratory Uppsala.

- Motivation

- Cross - section measurements

- Neutron sources

- Background subtraction

- NPI Řež

- TSL Uppsala

- Comparison NPI, TSL

- Conclusion

3

Outline- Motivation


- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Motivation Cross-section measurements Neutron sources in NPI and TSL Background subtraction Experiments on cyclotron in Řež TSL Uppsala experiments Comparison Conclusion

4

Motivation- Motivation• Evaluation• Corrections


- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

dEEENbeam

thresh

E

E

yield )()(

we measured threshold reactions on Au, Al, Bi, In, Ta, Ti, Y commonly used for such purposes and we also studied other materials: Cu, Fe, I, Mg, Ni, Zn.

evaluated from the experimentevaluated from the experiment

we would like to findwe would like to find!!

poor poor knowledgeknowledge, , we want to we want to measuremeasure

Solving a Fredholm equation we can find Φ(E):

the spatial distribution of neutron field inside ADS-setup can be determined with the help of Fredholm equation

due to poor knowledge for us imported neutron cross-section we carried out series of experiments devoted to their determination

5

Evaluation process-Motivation• Evaluation• Corrections


- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

BACKGROUNDBACKGROUND

SUBTRACTIONSUBTRACTION

209Bi(n,4n)206Bi

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

24 29 34 39 44 49 54 59 64 69 74 79 84 89 94

Neutron energy [MeV]

Cro

ss s

ect

ion

[ba

rn]

EXFOR TALYS 1.4. NPI Řež TSL Uppsala

6

Spectroscopic corrections

- Motivation• Evaluation• Corrections


- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Self-absorption

Detector efficiency

Correction for real coincidences

Square-emitter corection

Dead time correction

Decay during cooling

Decay during irradiation

Unstable irradiation 0,88

0,90

0,92

0,94

0,96

0,98

1,00

0 5 10 15 20

Distance from sample to detector [cm]

Squ

are-

emitt

er c

orre

ctio

n [-

]

1.25x1.25 cm

2x2 cm2.5x2.5 cm

3x3 cmiodine 3cm round

Uncertainty caused by the corrections was estimated to be less than 1% in total, except the uncertainty from efficiency calibration of the detector, which is below 3 %.

7

Evaluation - total yield- Motivation• Evaluation• Corrections


- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

)()(

)(

11

1

)(

)( 0

irrreal tirr

t

t

foillive

real

areaP

aabspyield e

t

e

e

mt

t

CCoiEI

BECSN

Peak area Self-absorption correction

Beam correction

Dead time correction

Decay during cooling and measurement

γ line intensity

Detector efficiency

Correction for coincidences

Square-emitter correction

Weight

normalization

Decay during

irradiation

8

Cross-section measurements



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Requirements for -measurements by activation method:

high energy neutron source with good intensity

monoenergetic (quasi-monoenergetic) neutrons or well known spectrum

pure monoisotopic samples

good spectroscopic equipment – and X-rays detectors

Then we can calculate Nyield and finally :An

yield

NN

ASN

Number of neutrons

in peak

foil size relative mass

Avogadro´s

number

9



- Neutron sources


- NPI Řež

- TSL Uppsala

- Comparison NPI, Uppsala

- Conclusion

Neutron sources NPI ASCR Řež: Energy range 14 – 37 MeV, neutron intensity ~ 108 n.cm-2.s-1

TSL Uppsala: Energy range 20 – 180 MeV, neutron intensity ~ 105 n.cm-2. s-1

0.0E+00

2.0E+14

4.0E+14

6.0E+14

8.0E+14

1.0E+15

1.2E+15

4 9 14 19 24 29 34 39


Num

ber

of n

eutr

ons

(1/s

r M

eV C

)

E=25 MeV

E=20 MeV

E=32.5 MeV

E=37 MeV

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 10 20 30 40 50 60 70 80 90 100


Neu

tron

flux

[1/M

eV (p

eak

area

= 1

)]

E = 50 MeV p-beam

E = 62 MeV p-beam

E = 70 MeV p-beam

E = 80 MeV p-beam

E = 92 MeV p-beam

E = 97 MeV p-beam

1E0

1E2

1E4

1E6

1E8

1E-7 1E-5 1E-3 1E-1 1E+1 1E+3Neutron Energy [MeV]

Neu

tro

n f

lux

den

sity

[1/

(cm

2.s)

]

spallation source at JINR

quasi-monoenergetic source at TSL102

104

108

106

0 10-7 10-3 10-5

10-1 101 103

Neutron spectra comparison

10



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Background subtraction

background contribution was determined by folding of the neutron source spectrum and calculated cross-sections (TALYS 1.4)

we calculated ratio between production in neutron peak and total production and with this ratio we multiplied the yields to subtract background production

0

1

15 35 55 75 95Energy [MeV]

Cro

ss-s

ectio

n v

ers

us n

eu

tro

n s

pe

ctr

um

[-]

Bi-204

beam 50 MeV(0.99)beam 62 MeV(0.87)beam 70 MeV(0.57)beam 80 MeV(0.40)beam 92 MeV(0.29)beam 97 MeV(0.28)

11



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Uncertainty analysis HPGe detector calibration uncertainty: less than 3%

Gauss-fit of the gamma peaks: > 1% (usually less than 10%)

spectroscopic corrections uncertainty: less than 1%

neutron spectra determination: 10%

neutron beam intensity determination: 10%

uncertainty of background subtraction: 10% in the worst case (big background, big model influence)

12



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Experiments in NPI four measurements

proton beam energies 20, 25, 32.5 and 37 MeV

irradiation time about 20 h.,irradiated foils: Ni, Zn, Bi, Cu, In, Al, Au, Ta, Fe and I

the sample distances from the lithium target – from 11 cm to 16 cm

13



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Experiments in TSL proton beam energies 50, 62, 70, 80, and 92 and 97 MeV

irradiation time about 8 h

14



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

NPI and TSL resultsComparison of cross-sections (n,xn) reactions on natural indium with TALYS

15



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Comparison of cross-sections (n,xn) reactions on iodine and tantalum with EXFOR, TALYS and libraries of evaluated data

16



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Comparison of cross-sections (n,x) reactions on aluminium and yttrium with TALYS, EXFOR and libraries of evaluated data

17



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Also with the help of our measured cross-section we can analyze neutron flux in different places of experimental set-ups consisting of lead, natural uranium and graphite irradiated by relativistic protons and deuterons (for example QUINTA – more about this setup in the talk of Mr. Furman or Mr. Wagner).

- neutron flux determined with the help of method “effective cross-sections” (experiment at phasotron in JINR Dubna – 660MeV protons, massive lead target, threshold detectors were situated on the target surface).

18



- Neutron sources


- NPI Řež

- TSL Uppsala


- Conclusion

Conclusion ten cross-section measurements were carried out in NPI Řež and in

TSL Uppsala

energy region from 17 MeV to 94 MeV was covered

we studied various materials in the form of thin foils and observed good

agreement with the data in EXFOR database and also with the cross-

sections calculated in deterministic code TALYS.

with the help of neutron cross-section we can analyze

neutron flux in different places of experimental set-ups

all our observed reactions you can find in journal: Nuclear Instruments

and Methods in Physics Research - Vol.726, (2013) 84-90

some of our results are already included in EFXOR

19

Thank you!supervisor in NPI Řež: RNDr. Vladimír Wagner, CSc.

supervisor in JINR Dubna: prom. fyz. Jindřich Adam, CSc.

[email protected]

[email protected]

Documents

Studies of neutron cross-sections by activation method in Nuclear Physics Institute Řež and in The Svedberg Laboratory Uppsala and experimental determination