Neutron Production in Pb/U Assembly Irradiated by 0.7 GeV Protons

1. Neutron production in large Pb/U assembly irradiated by 0.7 GeV protonsOndřej Svoboda Work leader: RNDr. Vladimír Wagner CSc. 22.4. 2006 Řež

2. Introduction • Within my Diploma thesis I worked on one of the experiments from project „Energy plus Transmutation“ • Project „Energy plus Transmutation“ dealth with problematics of neutron sources, that will be sutiable for future ADTT • Until now a lot of experiments within the E+P program: - target material and geometry tests – thick x thin target - charged particle source – different particles, energy, intensity - transmutation abilities – iodine, americium, radium, plutonium samples - large assemblies with natural uranium blanket AER Working Group "f" session - Třešť

3. Main goals of the experiment • Study spallation reactions and the density of the neutron fluxes in large assemblies from U and Pb • Comparison between experimental results and simulations done in MCNPX , deducating results with respect to used models and libraries • Verification of the hi-energy neutron cross-sections libraries • Neutron balance and multiplication factor study AER Working Group "f" session - Třešť

4. Spallation reactions • For most transmutation reactions we need strong neutron fields (~1016 n/cm2) => searching for good source • High energy charged particles produce a lot of neutrons by reactions with heavy elements (spallation reactions) AER Working Group "f" session - Třešť

5. Experiment • Carried out in June, 2004 on Nuclotron in LHE JINR Dubna, Russia • Incident particles: protons of energy 0.7 GeV; total number of protons counted by beam integrator: 5.19*1013 (big uncertainity) • Target: Pb rod surrounded by natural uranium • Irradiation time: 8 hours 51 minutes • Beam inlet and neutron production were measured by the method of neutron activation analysis AER Working Group "f" session - Třešť

6. Nuclotron accelerator • Superconductive accelerator – up to 12,8 GeV for protons, or 6 GeV on nucleon (possibility of acceleration up to U) • Extraction time 10 s • Beam intensity 108 up to 1011 • Superconducting magnets from NbTi alloy – cooled down to 4,5 K • Perimetre 251,5 m, weight of cooled magnets over 80 tons • Still is waiting for reconstruction + booster construction AER Working Group "f" session - Třešť

7. Target • Target – thick Pb rod (lenght 48 cm, diameter 8,4 cm), divided into 4 parts • Activation detectors – placed between the target parts and also before and behind + around the blanket • Target was surrounded by natural uranium blanket, U in form of rods (totaly 206,4 kg) • Whole setup placed in wooden box, walls filled with polyethylen (biological shielding) • On inner walls – Cd plate – shielding against thermal neutrons AER Working Group "f" session - Třešť

8. Beam monitors • In front of the target – two beam monitors => exact measurement of beam intensity, profile and position • Big monitor – total proton fluence • Small monitors – position and profile measurements • Activation materials: Al and Cu foils AER Working Group "f" session - Třešť

9. Selected isotops in beam monitors • Beam monitors were measured on HPGe detector – 2 types of measurements (short/long) AER Working Group "f" session - Třešť

10. Beam monitors - Results • Evaluation of the beam monitors had fundamental importance for whole experiment! • total proton flux through big detector - 1.22(5)x1013 • total proton flux through small detector - 0.90(5)x1013 • beam shift 0.5(1) cm up and 0.1(1) cm left AER Working Group "f" session - Třešť

11. Detection of rising neutrons • Neutrons comming from spallation reactions in target were measured by the method of neutron activation analysis • Used activation materials - Au, Al, Bi, Y, Co foils • Foils properties: squares cca 2x2 cm, weight ~ 1 g, thickness ~ 0,1 mm (according to foil material), totaly some 150 pieces AER Working Group "f" session - Třešť

12. Evaluation of the foils • Foils were measured on HPGe detectors • Evaluation of the measured spectra was done in the Deimos32 program – it fits the gamma-peaks to Gauss curves • Fitted peaks were assigned to the responsive isotopes • Yields of produced isotopes have been computed with respect to all corrections (decay during the irradiation, coincidences, unequable irradiation, square emitors..) AER Working Group "f" session - Třešť

13. Correction on unstable irradiation - Nuclotron as an experimental accelerator of charged particles for a wide range of energies doesn`t work in our case very good AER Working Group "f" session - Třešť

14. Longitudinal distributions of produced isotopes in Au and Al foils 10 cm from the target axis 3 cm from the target axis AER Working Group "f" session - Třešť

15. Radial distribution of produced isotopes in Au and Al foils – first gap AER Working Group "f" session - Třešť

16. Comparison between experimental data and simulations • Simulations done in MCNPX 2.4.0 and 2.5.0 Longitudial direction Radial direction Longitudial distance [cm] Distance from the centre [cm] AER Working Group "f" session - Třešť

17. Conclusion • Main aim of this experiment was a research of the neutron distribution in the setup, simulation of the setup in MCNPX and comparing of obtained results • At present we are finishing with the results interpretation and we are preparing a summary report • Results of the beam determination were used as a base for the report “The beam intensity determination – the Nuclotron experiment June 2004” – send to all E+T collaboration • So far the last E+T experiment ran through in November 2005 – deuterons 1.26 GeV, next experiment is planned to be carried out without the polyethylene shielding – June 2006 Thank you for your attention.. AER Working Group "f" session - Třešť