ondřej svoboda
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Nuclear Physics Institute, Academy of Sciences of Czech Republic Department of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague. Cross-section Measurements of (n,xn) Threshold Reactions. Ondřej Svoboda. - PowerPoint PPT PresentationTRANSCRIPT
Ondřej Svoboda
• Nuclear Physics Institute, Academy of Sciences of Czech Republic• Department of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague
O. Svoboda, A. Krása, M. Majerle, J. Vrzalová, V. Wagner
EFNUDAT – scientific workshop on Slow and Resonance Neutrons 23 – 25 September 2009 Budapest
Cross-section Measurements of (n,xn) Threshold Reactions
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
• Motivation for measurements
• Requirements for measurements
• TSL Uppsala facility
• Cyclotron in Řež facility
• Evaluation process
• Preliminary results
• Conclusion
Outline- Motivation for measurements
- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results- Conclusion
)()(
)(
111
)(
0
irrreal tirr
t
t
foillive
real
areaP
irrabspyield e
tee
mtt
CCoiEICCS
N
Motivation for measurements – E+T- Motivation for measurements • Energy plus Transmutation • EXFOR- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
EXFOR cross-sections- Motivation for measurements • Energy plus Transmutation • EXFOR- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results- Conclusion
0.01
0.1
1
10
0 50 100 150
Cro
ss-s
ectio
n [b
]
Neutron energy [MeV]
209Bi(n,xn)
(n,6n)204Bi (n,7n)203Bi(n,8n)202Bi (n,9n)201Bi(n,10n)200Bi (n,11n)199Bi(n,12n)198Bi
209Bi(n,xn)
0.0
0.5
1.0
1.5
2.0
0 50 100 150Neutron energy [MeV]
Cro
ss-s
ectio
n [b
]
(n,4n)206Bi(n,5n)205Bi
197Au(n,2n)196Au
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 10 20 30 40 50Neutron energy [MeV]
Cro
ss-s
ectio
n [b
]
EXFORENDF
197Au(n,4n)194Au
0.0
0.5
1.0
1.5
2.0
0 10 20 30 40 50Neutron energy [MeV]
Cro
ss-s
ectio
n [b
]
EXFORENDF
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Requirements for using activation method of measurement:
- high energy neutron source with good intensity
- (quasi)monoenergetic neutrons with well known spectrum
- pure monoisotopic samples
- good spectroscopic equipment: and X-rays detectors
- knowledge about the corrections on beam fluctuation, self-absorption, non-point like emitters…
Requirements for measurements- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results- Conclusion
0 10 20 30 40 50
Arb
itrar
y un
its
Energy [MeV]
neutron spectrum
simulated cross-section
0 10 20 30 40 50Energy [MeV]
neutron spectrumsimulated cross-section
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
TSL Uppsala – site
User-oriented facility…
- Motivation for measurements- Requirements- TSL Uppsala • Site • Blue hall • Irradiations
- Cyclotron Řež- Evaluation- Results- Conclusion
Protons 25 - 180 MeV
Neutron spectra from 7Li(p,n)7Be reaction
well known for proton energies 25,
50, and 97 MeV
1E0
1E2
1E4
1E6
1E8
1E-7 1E-5 1E-3 1E-1 1E+1 1E+3Neutron Energy [MeV]
Neu
tron
flux
den
sity
[1/(c
m2.
s)]
spallation source at JINR
quasi-monoenergetic source at TSL102
104
108
106
0 10-7 10-3 10-5 10-1 101 103
Experimental setup in the Blue hall
Neutron spectra comparison
TSL Uppsala – Blue hall- Motivation for measurements- Requirements- TSL Uppsala • Site • Blue hall • Irradiations
- Cyclotron Řež- Evaluation- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
8 hours irradiation at each energy
June 2008, supported from the EFNUDAT program
Proton beam energy [MeV] 25 50 977Li-target thickness [mm] 2 4 8.5
Proton beam current [A] 5 5 2
Average energy of peak neutrons [MeV] 22 47 94
Fraction of neutrons in the peak [%] 50 39 41
Peak neutron flux density [105 cm-2 s-1] 6 13 14.5
TSL Uppsala - irradiations- Motivation for measurements- Requirements- TSL Uppsala • Site • Blue hall • Irradiations
- Cyclotron Řež- Evaluation- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Cyclotron Řež• Protons 18 – 37 MeV on 7Li target
• Neutron spectra known for 20, 25, 30, and 35 MeV – Y. Uwamino et al., NIM A389 (1997) 463
• High neutron intensities: 108 cm-2 s-1
• Well equipped spectroscopic laboratory (NSD-NPI)
BeamBeam-line-line
Li-targetLi-target
GraphiteGraphite stopper stopper
SamplesSamples
Experiments on 20, 25, 32.5, and 37 MeV p
beams
~ 15 hours of irradiation
- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež • Facility • Diodes
- Evaluation- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Silicon diods for neutrons monitoring• BPW 34F, CMRP and Si-1 silicon diods tested at Řež
• Originally proposed as dosimeters (CERN), but can be also used as high-energy neutron monitors
• Irradiation with fast neutrons causes shift of the current-Voltage curve (measurement at constant current few mA for a period of hundreds of ms)
• Neutron intensity range 2.1012 – 4.1014 cm-2 at BPW 34F, respectively 1.108 – 2.1012 cm-2 at CMRP
- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež • Facility • Diodes
- Evaluation- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Reaction E thresh [MeV] Half-life197Au (n,2n)196Au 8.1 6.183 d197Au (n,3n)195Au 14.8 186.1 d197Au (n,4n)194Au 23.2 38.02 h197Au (n,5n)193Au 30.2 17.65 h197Au (n,6n)192Au 38.9 4.94 h197Au (n,7n)191Au 45.7 3.18 h197Au (n,8n)190Au 54.5 43 min197Au (n,9n)189Au 61.8 29 min
197Au (n,10n)188Au 70.9 9 min
In Řež also measured:
Mg, Ni, Fe, Zn
iodine (KIO4)
Measured materials- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation • Materials • Process • Corrections • Background
- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Irradiation
NYield
HPGe
Evaluation process
Spectra evaluation
Cross-section
Corrections0,94
0,95
0,96
0,97
0,98
0,99
1,00
1,01
0 2 4 6 8 10 12 14 16
Cor
rect
ion
fact
or
[-]
Source - detector distance [cm]
Ep Et
2x2cm emmiter
Production in peak Talys1.0
0
0,1
0,2
0,3
0,4
0,5
0,6
0 20 40 60 80 100Neutron energy [MeV]
Neu
tron
flux
[1/M
eV (p
eak
area
=1)]
24.7 MeV p-beam, 2 mm Li-target
49.5 MeV p-beam, 4 mm Li-target
97.6 MeV p-beam, 8 mm Li-target
- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation • Materials • Process • Corrections • Background
- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Spectroscopic corrections
0.94
0.95
0.96
0.97
0.98
0.99
1.00
1.01
0 2 4 6 8 10 12 14 16
Cor
rect
ion
fact
or [
-]
Source - detector distance [cm]
Ep Et
2x2cm emmiterp t
Real - cascade coincidences
Non-point-like emitters
Self-absorption
0
0.04
0.08
0.12
0.16
0 1000 2000 3000
Efec
tivity
[-]
Energy[keV]
ep na p2 et na p2ep na p3 et na p3p - p2p - p3
t - p2t - p3
Detector efficiency
Beam instability correction……
- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation • Materials • Process • Corrections • Background
- Results- Conclusion
0.5
1
1.5
2
2.5
0 500 1000 1500
Self-a
bsor
ptio
n fa
ctor
[-]
Energy[keV]
Tabular valueUsed gamma-lines
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Production by background neutrons• comparisons between EXFOR and TALYS – mostly good agreement
• We believe the simulated shape is OK, only the absolute value can be shifted
•Following the neutron spectrum knowledge, we calculated ratio between production in neutron peak and total production
• With this ratio we multiplied the yields to subtract background production
197Au(n,2n)196AuEXFOR data
TALYS
- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation • Materials • Process • Corrections • Background
- Results- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Experimental results – Au, Al, TaPreliminary results from Uppsala and Řež- Motivation for
measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results • Au, Al, Ta • Bi
- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
0.0
1.0
2.0
3.0
0 25 50 75 100
Cro
ss-se
ctio
n [b
]
Neutron energy [MeV]
197Au(n,2n)196Au
EXFOROur data from ŘežOur data from Uppsala
0.0
1.0
2.0
3.0
4.0
5.0
0 20 40 60 80 100
Cro
ss-se
ctio
n [b
]
Neutron energy [MeV]
181Ta(n,2n)180Ta
EXFOROur data from ŘežOur data from Uppsala
0.00
0.05
0.10
0.15
0.20
0 25 50 75 100
Cro
ss-se
ctio
n [b
]
Neutron energy [MeV]
27Al(n,a)24Na
EXFOROur data from ŘežOur data from Uppsala
0.00
0.05
0.10
0.15
0.20
0.25
0 25 50 75 100
Cro
ss-se
ctio
n [b
]
Neutron energy [MeV]
EXFOROur data from ŘežOur data from Uppsala
27Al(n,p)27Mg
Experimental results – BiPreliminary results from Uppsala- Motivation for
measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results • Au, Al, Ta • Bi
- Conclusion
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
0.0
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ss-se
ctio
n [b
]
Neutron energy [MeV]
EXFOR
Our data from Uppsala
209Bi(n,8n)202Bi
0.0
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0.2
0.3
0.4
0 50 100 150
Cro
ss-se
ctio
n [b
]
Neutron energy [MeV]
EXFOR
Our data from Uppsala
209Bi(n,7n)203Bi
0.0
0.1
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0.3
0 50 100 150
Cro
ss-se
ctio
n [b
]
Neutron energy [MeV]
EXFOR
Our data from Uppsala
209Bi(n,9n)201Bi
0.00
0.04
0.08
0.12
0 50 100 150
Cro
ss-se
ctio
n [b
]
Netron energy [MeV]
EXFOROur data from Uppsala
209Bi(n,10n)200Bi
Conclusion• Our cross-section measurements cover wide range of neutron energies (17 - 94 MeV)• New cross-sections measured in neutron energy region, where no data available so far (40 - 94 MeV)• Measured even cross-sections of reactions that have not been measured yet at all (e.g. I)• Preliminary results show that we are close to known cross-section values• This method of measurements can be used also for other materials• Plans for future – finalize Řež experiments analysis
– next experiments at Uppsala – uncertainty analysis
– publish final results – complete comparison with TALYS
- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results- Conclusion • Summary and prospects • Thanks
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest
Acknowledgements
Thank you for your attention..
We would like to thank to Dr. Bém and his colleagues for the possibility to joint their irradiations on cyclotron in Řež!
This work was supported from the EFNUDAT and from the grant CTU0808214.
- Motivation for measurements- Requirements- TSL Uppsala- Cyclotron Řež- Evaluation- Results- Conclusion • Summary and prospects • Thanks
EFNUDAT – scientific workshop on Slow and Resonance Neutrons, 23 – 25 September 2009 Budapest