Neutron sources in a 24-MV medical linear accelerator

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Engineering

Background:

• Understanding neutron sources in medical linear accelerators (LINACs) is crucial for radiation shielding and safety.
• The Clinac 2500 is a medical linear accelerator used in radiation therapy.

Purpose of the Study:

• To measure the cumulative neutron yield during the assembly of a Clinac 2500 prototype.
• To identify and quantify the relative strengths of individual neutron sources within the LINAC's treatment head.

Main Methods:

• Neutron fluence measurements were taken in a concrete cavity during sequential assembly of LINAC subassemblies.
• The method relied on the proportionality between scattered neutron fluence and fast neutron source strength.
• Results were normalized to the neutron output of the guide with bend magnet vacuum chamber.

Main Results:

• The relative neutron source strengths were quantified for various components.
• The primary collimator (2.4) and target (1.9) exhibited the highest relative neutron source strengths.
• Steel filter (0.6), tungsten filter (1.5), and jaw system (0.8 open, 2.0 closed) showed lower to moderate contributions.

Conclusions:

• The study successfully inventoried the relative neutron source strengths of Clinac 2500 components during assembly.
• Measurements align with existing literature estimates for neutron yields from LINAC treatment head components.
• This data is valuable for optimizing radiation shielding and safety protocols in radiation therapy facilities.