Monte carlo calculations for increasing of very cold neutron flux
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Monte-Carlo calculations for increasing of very cold neutron flux. Shabalin E., Verhoglyadov А. FLNP JINR. Main concept. CN: λ≈ 4÷20Å VCN: λ >20Å. Neutron spectrum. Cold (cryogenic) moderators Low rate of VCN in Maxwellian spectrum Neutron guides and radiation damage

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Monte-Carlo calculations for increasing of very cold neutron flux

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Monte carlo calculations for increasing of very cold neutron flux

Monte-Carlo calculations for increasing of very cold neutron flux

Shabalin E., Verhoglyadov А.

FLNP JINR


Main concept

Main concept

CN: λ≈4÷20Å

VCN: λ>20Å

Neutron spectrum

  • Cold (cryogenic) moderators

  • Low rate of VCN in Maxwellian spectrum

  • Neutron guides and radiation damage

  • Special reflector for increasing of directed neutron flux

  • Irradiation stable material with high reflectivity for CN, VCN

  • Nanodispersed diamond powder (particle size 1÷10nm)

  • Good VCN reflection at low thickness


The conical reflector

The conical reflector

  • Hollow truncated cone

  • Inner walls are covered by a layer of diamond nanopowder

  • Directed neutron flux will be increased

  • Existence of the optimal angle of cone opening

  • In our calculating:

  • Diameter of the source equal to 10cm

  • Neutron wavelength has Maxwellian distribution 1-10nm

  • Nanopowder particles are spheres with known distribution of their diameter 1-10nm

  • Main points:

  • Computation of the gain in the directed flux

  • Estimation of the nanopowder wall thickness

  • Total albedo

  • Differential (angular) albedo


Monte carlo calculations for increasing of very cold neutron flux

VCN coherent elastic scattered by particles as a whole

Differential cross section

  • Coherent elastic scattering on particles as a whole

  • Small angle scattering

  • Capture cross sectionσa=0.01b

  • Inelastic scattering didn’t consider(low temperature)

Calculating of the VCN transport was done by Monte Carlo statistical test


Monte carlo calculations for increasing of very cold neutron flux

The results

Differential albedo (azimuth angle dependence)

Differential albedo (polar angle dependence)

Total albedo depending on

incident polar angle


The results

The results


Conclusion

Conclusion

  • Addition of the conical reflector to the cold moderator raises forward directed VCN flux about twice

  • Walls thickness can be about 0.5cm for high gain factor

  • Maximum gain factor of the flux is obtained at angles of cone opening about 7-15 degrees

  • Optimal angle must depend on distribution of the neutrons flying out from the source

  • Investigation grooved type reflectors

  • with nanodispersed diamond powder

  • layers to reach more gain in VCN

  • production


Monte carlo calculations for increasing of very cold neutron flux

Thank you for attention!


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