Transcript (n,xn) cross-section measurements

• 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
the (n,xn) threshold reactions
Ondřej Svoboda
Outline
- Motivation for s
measurements
- Requirements
- TSL Uppsala
- Cyclotron Řež
- Conclusion
•
•
•
•
•
Motivation for s measurements
Requirements for s measurements
TSL Uppsala experiment
Experiments on Cyclotron in Řež
Cross-section conclusion
Motivation for s measurement – E+T
- Motivation for s
measurements
• Energy plus
Transmutation
• Yield to
neutron flux
- Requirements
- TSL Uppsala
- Cyclotron Řež
- Conclusion
N yield 
S p  Cabs  Cirr
I   P ( E)  Coi  Carea
treal 1
  tirr
e(t0 )
tlive m foil 1  e( treal ) 1  e( tirr )
Yield to neutron flux problem
- Motivation for s
measurements
• Energy plus
Transmutation
• Yield to
neutron flux
Solving a Fredholm equation we can find Φ(E):
Measured in E+T
N yield 
- Requirements
Ebeam
  ( E ) s ( E ) dE
Ethresh
- TSL Uppsala
Poor knowledge of s
- Cyclotron Řež
We would like to find!
(Up to now only MCNPX simulation)
Cross-section [barn]
3.0
197
2.5
2.0
EXFOR
ENDF
1.5
1.0
0.5
0.0
0
10
We want to measure
2.0
Au(n,2n)196Au
20
30
40
Neutron energy [MeV]
Cross-section [barn]
- Conclusion
197
Au(n,4n)194Au
1.5
EXFOR
ENDF
1.0
0.5
0.0
50
0
10
20
30
40
Neutron energy [MeV]
50
Requirements for s measurements
- Motivation for s
measurements
Requirements for s-measurements by activation method:
- Requirements
- high energy neutron source with good intensity
• Equipment
• Materials
- TSL Uppsala
- Cyclotron Řež
- Conclusion
- (quasi)monoenergetic neutrons with well known spectrum
- pure monoisotopic samples
- good spectroscopic equipment –  and X-rays spectrometers
- knowledge about the corrections on beam fluctuation,
self- absorption, non-point like emitters…
Evaluation process:
Irradiation
HPGe
Spectra evaluation
Corrections
s
NYield
N yield  S  A
Nn  N A
Measured materials
- Motivation for s
measurements
- Requirements
• Equipment
• Materials
- TSL Uppsala
- Cyclotron Řež
iodine
(KIO4)
- Conclusion
Reaction
E thresh
[MeV]
Half-life
197Au
(n,2n) 196Au
8.1
6.183 d
197Au
(n,3n) 195Au
14.8
186.1 d
In Řež also
measured:
197Au
(n,4n) 194Au
23.2
38.02 h
Mg, Ni, Fe, Zn
197Au
(n,5n) 193Au
30.2
17.65 h
197Au
(n,6n) 192Au
38.9
4.94 h
197Au
(n,7n) 191Au
45.7
3.18 h
TSL Uppsala
- Motivation for s
measurements
- Requirements
- TSL Uppsala
• Introduction
• Blue hall
• Experiment
• Measurements
- Cyclotron Řež
- s conclusion
- E+T:1.6 GeV d+
- Simulations &
comparisons
- Data share
- E+T conclusion
- Protons on Li target or spallation source
- Neutrons with energies 11-174 MeV
- Well known beam and neutron spectrum
TSL Uppsala – Blue hall
- Motivation for s
measurements
- Requirements
Experimental setup
in the Blue hall
- TSL Uppsala
• Introduction
• Blue hall
• Experiment
• Measurements
- Cyclotron Řež
- Conclusion
Neutron flux density [1/(cm2.s)]
1E8
108
1E6
106
1E4
104
1E2
102
spallation source at JINR
Neutron spectra
quasi-monoenergetic source at TSL
1E0
0 1E-7
10-7
-5
10
1E-5
-3
10
1E-3
1E-1
10-1
Neutron Energy [MeV]
1
1E+1
10
3
1E+3
10
TSL Uppsala - irradiations
- Motivation for s
measurements
- Requirements
- TSL Uppsala
• Introduction
• Blue hall
• Experiment
• Measurements
- Cyclotron Řež
- Conclusion
- 3 irradiations on the Li target – 25, 50, and 100 MeV p+
Proton beam energy [MeV]
24.68 ± 0.04
49.5 ± 0.2
97.9 ± 0.3
Li-target thickness [mm]
2
4
8.5
Proton beam current [mA]
10
10
5
Average energy of peak neutrons [MeV]
21.8
46.5
94.7
Fraction of neutrons in the peak [%]
50
39
41
Peak neutron flux density [105 cm-2 s-1]
1.3
2.9
4.6
- one irradiation on the ANITA
spallation target – 180 MeV p+
June 2008, supported by
EFNUDAT program
TSL Uppsala – spectroscopic measurements
- Motivation for s
measurements
- 8 hours each irradiation
- Requirements
- one day of spectroscopic measurements after each irradiation
- TSL Uppsala
• Introduction
• Blue hall
• Experiment
• Measurements
Au, Al, Bi, In, Ta, I samples
- Cyclotron Řež
- Conclusion
Present status:
Finished yields evaluation: ratio Řež – Uppsala ~ 1000
Now waiting for the beam data…to be completed soon
Cyclotron Řež
- Motivation for s
measurements
- Protons on Li target
- Requirements
- Neutrons with energies 10-37 MeV
- TSL Uppsala
- Good intensities: 108 n cm-2 s-1
- Cyclotron Řež
• Introduction
• Experiments
• Preliminary
results
Beam-line
Graphite
stopper
- Well equipped spectroscopic
laboratory (NSD-NPI)
Samples
- Conclusion
Li-target
Cyclotron Řež – experiments
- Motivation for s
measurements
- Up to now 2 experiments: 20 and 25 MeV
- Requirements
- Au, Al, Bi, In, Ta, I, Ni, Fe, Mg, Zn
- TSL Uppsala
- next irradiations will hopefully be in near future
- Cyclotron Řež
• Introduction
• Experiments
• Preliminary
results
2E+15
.1015
- Conclusion
20 MeV
25 MeV
30 MeV
35 MeV
40 MeV
n [1/sr MeV C]
1E+15
.1015
.1014
8E+14
.1014
4E+14
0
0E+00
0
10
20
30
Neutron energy [MeV]
40
Cyclotron Řež – experimental results
- TSL Uppsala
- Cyclotron Řež
• Introduction
• Experiments
• Preliminary
results
- Conclusion
194Au
1.25
1
s
EXFOR data
Our value - Řež
0.75
N yield  S  A
Nn  N A
0.5
Number of
neutrons in peak
0.25
0
20
25
30
Energy [MeV]
Tentative data!
Evaluation not yet
ready…
35
40
3.0
Cross-section [barn]
- Requirements
1.5
Cross-section [barn]
- Motivation for s
measurements
2.5
196Au
EXFOR data
Our value - Řež
2.0
1.5
1.0
0.5
0.0
0
10
20
Energy [MeV]
30
40
Conclusion
- Motivation for s
measurements
- Requirements
- TSL Uppsala
- Cyclotron Řež
- Conclusion
– Uppsala and Řež cross-section measurements
covered wide spectrum of energies (20-100 MeV)
– Preliminary results show we are close to known
cross-section values
– Near future – finalize experiment analysis
– next experiments at Řež
– Farther future – next experiments at Uppsala?
– application of the results on the E+T
experiments
– publish the measured cross-sections
with respect to be involved in the
EXFOR library if possible
Thank you for your attention..