Laboratory Experiment 1 Vasily Arzhanov

HT2004Lab 12 Safety Distance: keep yourself as far from radiation sources as possible Time: expose yourself to radiation as short time as possible Number: expose to radiation only minimal number of people

HT2004Lab 13 Experimental Setup d d = 6 ÷ 47 cm Cd Sphere Without CdWith Cd NoCd08cm100sWithCd08cm50s NoCd12cm200sWithCd12cm400s 1.Naming convention 2.Same distances 3.Time scaling

HT2004Lab 14 Detection Technique α γ Fiss. prod. γ Channel 1: 97% Channel 2: 3% 6 Li Eu α t PM n γ γ Detector

HT2004Lab 15 Multi-Channel Analyser 0 Amplitude A max … A n-1 A1A1 AnAn Counts Time Channel n-1 Channel n

HT2004Lab 16

HT2004Lab 17 Summary Set/remove the Cd sphere Set a distance Acquire data Save to a file Set channels to sum up counts Scale the counts to the reference time Write down the result

HT2004Lab 18 One-Speed Diffusion Theory S0S0 r > 3λ s Isotropic source of thermal (slow) neutrons Distance at which Diffusion theory is valid

HT2004Lab 19 Differential Measurement

HT2004Lab 110 Diffusion Length r Thermal (slow) neutron borne Thermal neutron absorbed Average over the neutron population

HT2004Lab 111 Migration Area (Length) Fast neutron borne Thermal neutron absorbed Fast neutron thermalized r rsrs r th Differential measurement Ordinary measurement

HT2004Lab 112 θ θ θ ave = 0 θ ave = 90 Fast neutron borne Fast neutron thermalized Thermal neutron absorbed Orthogonality Property

HT2004Lab 113 Calculation of Migration

HT2004Lab 114 log r 2 A(r) Evaluating Integrals Ordinary meas.

HT2004Lab 115 Relaxation Length S0S0 r Uncollided flux First collision Absorption No absorption Absorption

HT2004Lab 116 Summary