A variety of irradiation processes uses low energy electron beam facilities to modify product characteristics. Dosimetry requirements, the number and frequency of measurements, and record keeping requirements will vary depending on the type and end use of the products being processed. Dosimetry is often used in conjunction with physical, chemical, or biological testing of the product, to help verify specific treatment parameters.

Note 1-In many cases dosimetry results can be related to other quantitative product properties; for example, gel fraction, melt flow, modulus, molecular weight distribution, or cure analysis tests.

Radiation processing specifications usually include a minimum or maximum absorbed dose limit, or both. For a given application these limits may be set by government regulation or by limits inherent to the product itself.

Critical process parameters must be controlled to obtain reproducible dose distribution in processed materials. The electron beam energy, beam current, beam width and process line speed (conveying speed) affect absorbed dose.

Before any electron beam facility can be routinely utilized, it must be validated to determine its effectiveness. This involves testing of the process equipment, calibrating the measuring instruments and the dosimetry system, and demonstrating the ability to consistently deliver the required dose within predetermined specifications.

In order for a dosimetry system to be effective in low-energy electron irradiation applications and to measure doses with an acceptable level of uncertainty, it is necessary to calibrate the dosimetry system under irradiation conditions that are consistent with those encountered in routine use. For example, a dosimetry system calibration conducted using penetrating gamma radiation or high energy electrons may result in significantly inaccurate dose measurement when the dosimetry system is used at low energy electron beam facilities. Details of calibration are discussed in Section 5.