1. Institute of Radiation Physics Dr. Evert Birgersson www.fzd.de Member of the Leibniz Association The nELBE neutron source Dr. Evert Birgersson, Institute of Radiation Physics, FWKK

2. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Overview Introduction nELBE – neutron facility at ELBE Total cross section measurements Inelastic scattering cross section measurements Summary

3. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro nELBE – neutron facility at ELBE (Electron Linear accelerator with high Brilliance and low Emittance)

4. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Liquid lead loop Collimator Ø = 2 cm Ø = 3 cm electrons Lead flow Small liquid lead volume (1 cm 3 ) and short electron pulse (10 ps) gives a neutron energy resolution of  E/E  1 % when ToF is used to determine neutron energies Stable operation for more than 800 hours The ELBE electron beam hits liquid lead and creates neutrons from the bremsstrahlung by ( ,n) reactions Ee- = 30 - 40 MeV, Bunch charge 77 pC, repetition rate 100 or 200 kHz

5. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Absorbers or transmission targets Absorption is higher for gammas than neutrons

6. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro PTB ionization chamber Parallel plate ionisation chamber well-characterized U layers 201.6 mg 235 U 10 layers Diameter 7.2 cm

7. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Neutron energy spectra The ToF spectrum in the Fission chamber is converted to energy and by using the 235 U fission cross section and target material the flux is determined, 3.810 4 n/cm 2 s at 19  A at 5.55 m from the lead radiator. A factor of two neutron yield is still missing, compared to MCNP simulations and cathode current measurement –was 60 in August 2008 –Was 6 in December 2008 Improved beam tuning, alignment of beam line

8. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Beam profile scan Vertical scan Main neutron and gamma beam well described Experiment show more neutrons and gammas in the halo Scans can be performed vertically and horizontally with a movable plastic scintillator

9. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro 11 22 n 11 22 Shutter open Shutter closed Gammas through the door n Concrete wall Lead

10. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Less radiation adjacent room The extra shielding is necessary 11 22 No extra wall With extra wall

11. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Transmission measurement ch->ToF->E n Only one event per accelerator bunch can be used due to after pulsing in the photomultiplier, large gamma flash reduces the efficiency T live_daq is the time the data acquisition is ready f acc is the accelerator repetition rate Every Channel has its own live time

12. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro

15. nELBE – inelastic scattering detector Setup 4 plastic scintillators for neutron detection (1 m, 11 x 43 mm 2 ) Beyer et al., NIMA 575 (2007) 449 neutron beam BaF 2 array for gamma detection (42 crystalls, 29 cm, Ø 5.3 cm sample: nat Fe (99.8%)  91.754% 56 Fe mass: 19.82 g  18.15 g 56 Fe flight paths: source – sample: 600 cm sample – BaF2: 30 cm sample – Plastics: 100 cm 235 U fission chamber for neutron flux determination VME-based electronics setup All detectors have time resolutions of about 600 ps

16. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Experimental method Integral at target: 2x10 4 n/s/cm 2 E n,out = E n,in - E x

17. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Tof and energy from 2 MeV neutrons 2 MeV mono energetic neutrons were simulated to understand additional background. Flux determined 1m from the side of the beam. Gamma-neutron coincidence not possible in MCNP Elastic scattering in the collimator Elastic scattering on Fe Inelastic scattering on Fe

18. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Preliminary Result, neutron Inelastic scattering on iron

19. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Conclusions The nELBE neutron ToF facility has been operational since November 2007 Background conditions are continously improving Operation of the liquid lead loop is extremely stable Transmutation relevant cross section are measured From 2010: Superconducting RF-injector (bunch charge 2nC (77pC) 1mA at 500 kHz, which is the design criterion for the lead loop New larger measurement room planed in conection to the extention ELBE Outlook

20. Institute of Radiation Physics Dr Evert Birgersson www.fzd.de Svenskt Kärnfysikmöte XXIX, 17-18 november 2009, Örebro universitet, Örebro Thanks to all Collaborators FZD, Institute of Radiation Physics: A.R. Junghans, D. Bemmerer, R. Beyer, The ELBE Crew, M. Erhard, E. Grosse, R. Hannaske, A. Hartmann, K. Heidel, M. Kempe, K. Kossev, U. Lehnert, M. Marta, R. Massarczyk, A. Matic, P. Michel, C. Nair, K.-D. Schilling, R. Schurig, R. Schwengner, M. Sobiella, A. Wagner FZD, Institute of Safety Research: E. Altstadt, C. Beckert, V. Galindo, K. Noack, F.-P. Weiss FZD, Department Radiation Protection and Safety: B. Naumann FZD, Department Research Technology: R. Schlenk, S. Schneider TU Dresden: H. Freiesleben, M. Greschner, A. Klix, K. Seidel Physikalisch Technische Bundesanstalt Braunschweig: M. Mosconi, R. Nolte, S. Röttger Others: J. Klug, C. Rouki, G. Rusev