4.1 The design and operation of a self-contained irradiator should ensure that reproducible absorbed doses are obtained when the same irradiation parameters are used. Dosimetry is performed to determine the relationship between the irradiation parameters and the absorbed dose.

4.1.1 For most applications, the absorbed dose is expressed as absorbed dose to water (see ISO/ASTM Practice 51261). For conversion of absorbed dose to water to that to other materials, for example, silicon, see Annex A1 of ISO/ASTM Practice 51261.

4.2 Self-contained dry-storage gamma irradiators contain properly shielded radioactive sources, namely ¹³⁷Cs or ⁶⁰Co, that emit ionizing electromagnetic radiation (gamma radiation). These irradiators have an enclosed, accessible irradiator sample chamber connected with a sample positioning system, for example, irradiator drawer, rotor, or irradiator turntable, as part of the irradiation device.

4.3 Self-contained dry-storage gamma irradiators can be used for many radiation processing applications, including the calibration irradiation of dosimeters; studies of dosimeter influence quantities; radiation effects studies, and irradiation of materials or biological samples for process compatibility studies; batch irradiations of microbiological, botanical, or in-vitro samples; irradiation of small animals; radiation "hardness" testing of electronics components and other materials; and batch radiation processing of containers of samples.

Note 1: Self-contained dry-storage gamma irradiators contain a sealed radiation source, or an array of sealed radiation sources securely held in a dry container constructed of solid materials. The sealed radiation sources are shielded at all times, and human access to the chamber undergoing irradiation is not physically possible due to the irradiator's design configuration (see ANSI/HPS N43.7).

Note 2: For reference-standard dosimetry, the absorbed dose and absorbed-dose rate can be expressed in water or other material which has similar radiation absorption properties to that of the samples or dosimeters being irradiated. In some cases, the reference-standard dosimetry may be performed using ionization chambers, and may be calibrated in terms of exposure (C kg^-1), or absorbed dose to air, water or tissue (Gy). Measurements performed in terms of exposure apply to ionization in air, and care should be taken to apply that measurement to the sample being irradiated.