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