Laboratory Experiment 1

1
Laboratory Experiment 1

• Vasily Arzhanov

2
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

3
Experimental Setup
d 6 47 cm
d

1. Naming convention
2. Same distances
3. Time scaling

Without Cd With Cd
NoCd08cm100s WithCd08cm50s
NoCd12cm200s WithCd12cm400s
Cd Sphere
4
Detection Technique
97
a
Channel 1
?
Detector
?
PM
Eu
?
a
3
6Li
n
Channel 2
t
Eu
?
Fiss. prod.
5
Multi-Channel Analyser
Counts
Channel n
Channel n-1
Amplitude
0

An-1
A1
An
Amax
Time
6
(No Transcript)
7
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

8
One-Speed Diffusion Theory
S0
r gt 3?s
Distance at which Diffusion theory is valid
Isotropic source of thermal (slow) neutrons
9
Differential Measurement
10
Diffusion Length
Thermal (slow) neutron borne
Thermal neutron absorbed
r
Average over the neutron population
11
Migration Area (Length)
Ordinary measurement
Thermal neutron absorbed
Fast neutron borne
r
Differential measurement
rs
rth
Fast neutron thermalized
12
Orthogonality Property
Fast neutron borne
Thermal neutron absorbed
?
?
?ave 90
?ave 0
Fast neutron thermalized
13
Calculation of Migration
14
Evaluating Integrals
log r2A(r)
Ordinary meas.
15
Relaxation Length
No absorption
r
S0
Absorption
Absorption
Uncollided flux
First collision
16
Summary