1. The experiment on JINR Dubna Nuclotron
Filip Křížek, ÚJF AV ČR

2. The experiment on JINR Dubna accelerator Nuclotron
The experiment was carried out in December 2001.
A thick lead target and an uranium rod blanket
were irradiated with 1.5 GeV proton beam.
The weight of uranium blanket was about 200 kg.
The set-up was irradiated approximately 12 hours.
Total proton flux during the period of irradiation was
Electrical current approximately 40 pA.
The aims of the experiment were:
- the study of neutron field in the set-up,
- transmutation of radioactive samples,
- heat production in the set-up.

3. Lead target with the natural uranium rod blanket

4. View on the experimental set-up

5. The Activation Detector Method
Reactions induced on activation detector (n,g), (n,2n), (n,3n), ...
Fredholm equation:
209Bi(n,5n)205Bi

6. Positions of activation
detectors in the set-up
Sandwiches contained
Al, Au, Co and Bi foils.
Foils had square shape
2 cm × 2 cm.

7. Activation reactions

8. Processing of gamma spectra with programme DEIMOS
HPGe spectrometer Ortec
The graphical environment
of programme DEIMOS

9. The determination of the yield
The yield (Nyield) is the number of produced nuclei of certain isotope
in activation detector during the whole period of irradiation
divided by mass of the activation detector and total proton flux.
Ndet(E) - area of transition peak with energy E given by DEIMOS
Ig(E) - transition absolute intensity
ep(E) - peak efficiency of the detector
COI - correction on the cascade coincident effects
treal / tlive - correction on the detector dead time
m I(p+) - product of foil mass and total proton flux
l - decay constant
t0 - interval from the end of irradiation until the begin of measurement
tirr - irradiation time

12. Ratios of the yields from the front and from the back of the target

13. Comparison of experimental data with simulation made by the MCNPX code

14. Simulation of the neutron field at different places in the target

15. Comparison of experimental data with simulation made by the MCNPX code

16. Conclusion
The neutron production was measured in the set-up which
consisted of a thick lead target and an uranium rod blanket.
The Activation Detector Method was used to determine the shape
of neutron energetic distribution in different places of set-up.
The comparison was made between the simulations calculated by
the MCNPX code and experimental data. Simulations are in good
qualitative agreement with our measurement. They underestimate
production of isotopes in the blanket and at the end of the target.
In 2003 was carried out another experiment on the same set-up.
Energy of the proton beam was 1 GeV. Next experiment will be in
the JINR Dubna in summer (2.5 GeV proton beam).