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Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
Development of a Neutron Time-of-Flight Source at the ELBE Accelerator
• ELBE• Neutron source• Collimator• Beam characteristics• Detector development
Institute of Nuclear and Hadron Physicsand Institute of Safety Research,
Forschungszentrum Rossendorf, Dresden
Institute of Nuclear and Particle Physics,Technische Universität Dresden
J. Klug, E. Altstadt, C. Beckert, R. Beyer, H. Freiesleben, V. Galindo,M. Greschner, E. Grosse, A. R. Junghans, D. Légrády, B. Naumann,
K. Noack, R. Schlenk, S. Schneider, K. Seidel, A. Wagner, F.-P. Weiss
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
PhD: 2005, Reactor Institute Delft, Delft University of Technology, The Netherlands
Thesis: The Time Dependent Midway Monte Carlo Method for Borehole Logging Applications
Currently working at: Forschungszentrum Rossendorf,Institute of Safety Research, Dresden, Germany
Current Research Areas:
• Time Dependent Monte Carlo for Reactor Dynamics
• variance reduction optimisation for the collimator of the ELBE nToF setup
• detector simulations for the nTof measurements
Connection to EUROTRANS:
• Future contributor
• ADS simulations
About Me
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
ELBE: Electron Linear accelerator with high Brilliance and low Emittance
The superconducting electron accelerator ELBE
Ee ≤ 40 MeVIe ≤ 1 mAMicropulseduration t = 5 psf = 0.5–1 MHz
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
The liquid-lead radiator
• Electron beam pulse length t = 5 ps
• Small neutron radiator volume - short neutron pulses, well-determined in time by e- beam time structure - minimize scattering in radiator & thermal neutron background
• Large enough for reasonable intensity - optimal volume 1 cm3
- neutron pulse width < 2 ns - En resol E/E < 1 % at 4 m flight path
• Thermal load up to 25 kW liquid Pb radiator
• Water-cooled via InGaSn heat exchanger
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
1,E+00
1,E+01
1,E+02
1,E+03
1,E+04
1,E+05
1,E+06
1,E+07
1,E-05 1,E-04 1,E-03 1,E-02 1,E-01 1,E+00 1,E+01 1,E+02
En / MeV
Flu
x d
ensi
ty /
cm
-2 s
-1
Pb in radiator
Mo in radiatorSteel housingTotal
Neutron fluxes obtained with Ie = 1 mAMCNP simulations
Ee
MeV
From rad.s-1
At det., 4 m
cm-2 s-1
20 7.9·1012 4.6·106
30 1.9·1013 1.0·107
40 2.7·1013 1.5·107
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
Neutron beam profile for different collimatorsMCNP simulations; Ee = 30 MeV, Ie = 1 mA
2.4 m
normal heavy boratedconcrete concrete PE lead
beam
cyl.hole,
Ø 3 cm
conical
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
0 5 10 15 20 25 30 35 40
Radial distance from center / cm
Flu
x d
ensi
ty /
cm
-2 s
-1
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
1,E+01
1,E+02
1,E+03
1,E+04
1,E+05
1,E+06
1,E+07
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600t / ns
Flu
x d
ensi
ty /
cm
-2 s
-1
No filter
5 cm PE + 5 mm Cd
No filter
5 cm PE + 5 mm Cd
Neutron fluxes, pulse overlap without/with filterf = 500 kHz
180 ns, 2.5 MeV &2.18 s, 20 keV
Present pulse / previous, no filter: 5·102
with filter: 1·104
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
Time-of-flight vs. energy
96 % in peak
t = 0.1 nsEn = 1 keV
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
Detector development
BaF2
• l = 19 cm• Ø = 53 mm• : 80 % of 4 sr• slow & fast component pulse shape discr
60Co source • E/E 12 % at 1 MeV• time resol 640 ps
Plastic scintillators
• l = 1 m• Large np scattering cross sec• Good timing resolution detection point from two- sided readout
< 1 MeV: Li-glass
• 6Li(n,t)
Photons
Neutrons
n
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
Detector development
time / ns
coun
ts
• neutron detection efficiencies• share of events with lost timing info due to neutron scattering before detection
25 mm Li-glass 11 mmplastic
threshold5 keV
34 %
15 %
Eff = 1.6 % Eff = 56 %
Simulations:
En = 144 keV:
no conditioncoincidence in PMTsanticoincidence
counts
QDC channel
Plastic scintillator detectors:
single-electron peak observed by coincident readout of PM tubes neutron detection threshold of 5–10 keV
(252Cf source)
Institute for Safety ResearchDávid LégrádyIP-EUROTRANS ITC2
Summary
• New neutron ToF setup – liquid Pb radiator at ELBE
• Compact system – 5 ps e- pulses, 4 m flight path
• E/E < 1 %
• Neutron intensity 1.5·107 cm-2 s-1
• 50 keV < En < 10 MeV
• Assembly in progress
• Test runs of the radiator
• & n detectors ready for calibration
e- n