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Analyzing Neutron Fluence and Beam Interception Factors in EAR-1 Simulations at CERN

This study, presented at the n_TOF Analysis Group Meeting at CERN on April 18, 2012, examines the spatial profile of neutron fluence in EAR-1 simulations. Key concepts include the beam interception factor (BIF), assessing how beam energy and geometry influence the hits on samples of varying radii. The analysis covers different geometries and sample sizes, discussing the impact of sample alignment and gravity. Findings reveal significant variations in the 5 eV-to-thermal ratio, emphasizing the critical nature of sample positioning and alignment in neutron fluence measurements.

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Analyzing Neutron Fluence and Beam Interception Factors in EAR-1 Simulations at CERN

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  1. n_TOF EAR-1 SimulationsSpatial profile & beam interception factor A. Tsinganis (CERN/NTUA), V. Vlachoudis (CERN), C. Guerrero (CERN) and others n_TOF Analysis Group Meeting CERN, April 18, 2012

  2. Geometry EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  3. Spatial profile EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  4. Beam interception factor • How much – and what part – of the beam hits a sample of radius R? • Dependent on energyand geometry • Different samples / geometries studied EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  5. Beam interception factor • BIF calculated for 1, 2 & 3cm diameter samples @184m EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  6. Beam interception factor • Influence of gravity EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  7. Beam interception factor • Normalising at 5eV… • …differences in the shape and the 5eV-to-thermal ratio emerge 1% 2.5% EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  8. Beam interception factor • Beam-line alignment • Tested for 3 cases • Realistic collimation setup • Aligned • “Ideal” alignment <0.5% normalised @5eV 1 % EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  9. Beam interception factor • Sample alignment • x- and y-offsets of 2mm • Changes in the shape and the 5eV-to-thermal ratio! 1.5% 6 % EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  10. Conclusions • The 5eV-to-thermal ratio is sensitive to various parameters • The sample alignment is the most relevant • These uncertainties have been quantified • Normalising at 5 eV, the value at thermal in the worst case can change ~6% • Nevertheless, a +/- 2mm offset of the sample is perhaps too pessimistic • This source of uncertainty should be kept in mind during pertinent data analysis • BIF(E) for specific sample size and position available upon request EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

  11. The end EAR-1 Simulations: neutron fluence n_TOF Analysis Group Meeting – CERN, April 18, 2012 | A.T.

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