ASTM/ISO 51631-03

4.1 This practice is applicable to the use of a calorimeter for the measurement of absorbed dose in electron beams, the qualification of electron irradiation facilities, periodic checks of operating parameters of electron irradiation facilities, and calibration of other dosimeters in electron beams.

NOTE 1 - For additional information of the use of dosimetry in electron accelerator facilities, see ISO/ASTM Practices 51431 and 51649, and ICRU Reports 34 and 35, and Refs (1-3).4

4.2 The calorimeters described in this practice are not primary-standard dosimeters. They may be used as transferstandard dosimeters or as internal standards at an electron beam irradiation facility, or may be routine dosimeters used for routine dose measurements. The calorimeters are calibrated by comparison with transfer-standard dosimeters.

4.3 The dose measurement is based on the measurement of the temperature rise in an absorber (calorimetric body) irradiated by an electron beam. Different absorbing materials are used, but the response is usually defined in terms of dose to water.

4.4 The absorbed dose in other materials irradiated under equivalent conditions may be calculated. Procedures for making such calculations are given in ASTM Practices E 666 and E 668, ISO/ASTM Guide 51261, and Ref (1).

4.5 The average absorbed dose in the volume of the calorimetric body is measured. Dose gradients may occur in this volume and may have to be considered when estimating dose in other materials.

4.6 The calorimetric bodies of the calorimeters described in this practice are made from low atomic number materials. The electron fluences within these calorimetric bodies will be approximately equal when irradiated with electron beams of 1.5 MeV or higher. Calibration in terms of dose to water is possible for these calorimeters.

4.6.1 Calorimeters for use at industrial electron accelerators have been constructed using graphite, polystyrene or a Petri dish filled with water as the calorimetric body (4-10). The thickness of the calorimetric body shall be less than the range of the electrons for the specified material.

4.6.2 Polymeric materials other than polystyrene may be used for calorimetric measurements. Polystyrene is used because it is known to be resistant to radiation (11) and because no exo- or endothermic reactions take place (12).

1.1 This practice covers the preparation and use of semi-adiabatic calorimeters for measurement of absorbed dose and routine dosimeter calibration when irradiated with electrons for radiation processing applications. The calorimeters are either transported by a conveyor past a scanned electron beam or are stationary in a broadened beam.

1.2 This practice applies to electron beams in the energy range from 1.5 to 12 MeV.

1.3 The absorbed dose range depends on the absorbing material and the irradiation and measurement conditions. Minimum dose is approximately 100 Gy and maximum dose is approximately 50 kGy.

1.4 The averaged absorbed-dose rate range shall generally be greater than 10 Gys¹.

1.5 The temperature range for use of these calorimeters depends on the thermal resistance of the materials, on the calibration range of the temperature sensor, and on the sensitivity of the measurement device.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.