Detectors that rely on chemical changes- Neutron Detection

Film badge (photographic dosimeter).

Detectors that rely on chemical changes

Film emulsion

contains silver halide crystals (AgBr) — ionizing radiation produces latent image which develops to a darkening on chemicalprocessing.

exposure

Film badge (photographic dosimeter)

Optical density after development is proportional to ____.

energy discrimination, directional information

Film badge (photographic dosimeter)

Filters on the badge yield ____ and ____

Film badge (photographic dosimeter)

Advantages historically: low cost, permanent record (if stored)

Film badge (photographic dosimeter)

Disadvantages: limited dynamic range, energy dependence, fading, processing required, largely replaced by OSL/TLD.

Film badge (photographic dosimeter)

uncharged particles,  ionize matter

Neutrons are ____ → they do not directly___

Neutron Detection

Detection must rely on secondary charged particles produced in nuclear reactions.

Elastic scattering, Neutron capture (absorption), Nuclear reactions

Neutron Detection Main interaction mechanisms:

Neutron capture (absorption)

Neutron Detection

nucleus emits charged particles or γ-rays.

Nuclear reactions

Neutron Detection

producing radioactivity (activation foils)

detector material

target nucleus

secondary charged particles

detector medium

ionization/scintillation; electrical signal

Neutron Detection

Step by step:

Neutron enters the___.

Interacts with ____(e.g., ¹⁰B, ³He, ⁶Li)

Produces ____ (protons, α, electrons).

These charged particles ionize the ___(gas, solid, or liquid).

Resulting____ converted into ____.

Conversion gas detectors, Activation methods

Neutron detection— two main approaches

Conversion gas detectors

Neutron detection— two main approaches

e.g., BF₃ (Boron Trifluoride) or ³He (Helium-3) detectors — neutrons captured by nucleus produce charged particles which ionize gas and are detected.

Activation methods

Neutron detection— two main approaches

irradiate foils — neutron absorption makes nucleus radioactive. (e.g., gold, indium) → induced radioisotopes measured by gamma spectrometry → infer neutron fluence