neutron production in large pb u assembly irradiated by 0 7 gev protons ond ej svoboda
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Neutron production in large Pb/U assembly irradiated by 0.7 GeV protons Ondřej Svoboda. Work leader: RNDr. Vladimír Wagner CSc. 22.4. 2006 Řež. Introduction. Within my Diploma thesis I worked on one of the experiments from project „Energy plus Transmutation“

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neutron production in large pb u assembly irradiated by 0 7 gev protons ond ej svoboda

Neutron production in large Pb/U assembly irradiated by 0.7 GeV protonsOndřej Svoboda

Work leader: RNDr. Vladimír Wagner CSc.

22.4. 2006 Řež

introduction
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

main goals of the experiment
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

spallation reactions
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

experiment
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

nuclotron accelerator
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

target
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

beam monitors
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

selected isotops in beam monitors
Selected isotops in beam monitors
  • Beam monitors were measured on HPGe detector – 2 types of measurements (short/long)

AER Working Group "f" session - Třešť

beam monitors results
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

detection of rising neutrons
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

evaluation of the foils
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

correction on unstable irradiation
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

slide14

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

slide15

Radial distribution of produced isotopes in Au and Al foils – first gap

AER Working Group "f" session - Třešť

comparison between experimental data and simulations
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

conclusion
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

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