Pradhan A S, Bakshi A K
Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai, India.
Radiat Prot Dosimetry. 2002;98(3):283-90. doi: 10.1093/oxfordjournals.rpd.a006720.
CaSO4:Dy and LiF TLDs do not exhibit photon energy dependence beyond +/-55% for photons in the energy range from 1 MeV to about 7 MeV. However, when sandwiched between metal filters or used in TLD badge holders having metal filters, the response changes for irradiation from high energy photons as compared to that from 60Co gamma rays (generally used for reference calibrations). This effect is about the same for both the lower atomic number TLD (LiF) and higher atomic number TLD (CaSO4:Dy). For TLDs held on the surface of the phantom and irradiated in collimated photon beams, the response of TLDs without any filter or those under the open window of the TLD badge is considerably reduced due to insufficient build-up to high energy photons, whereas for uncollimated radiation fields from power reactors, an over-response is observed. It is observed that the use of inappropriate encapsulation of dosemeters would cause a significant error not only in the estimation of doses due to penetrating radiations but also in the estimation of beta doses in the mixed fields of beta radiation, high energy gamma rays and high energy electrons often encountered in the fields of pressurised heavy water reactors.
对于能量范围从1兆电子伏特到约7兆电子伏特的光子，硫酸钙:镝（CaSO4:Dy）和氟化锂（LiF）热释光剂量计（TLDs）的响应在±55%范围之外不呈现光子能量依赖性。然而，当夹在金属滤片之间或用于带有金属滤片的TLD徽章夹中时，与60钴伽马射线（通常用于参考校准）相比，高能光子照射下的响应会发生变化。对于原子序数较低的TLD（LiF）和原子序数较高的TLD（CaSO4:Dy），这种效应大致相同。对于置于模体表面并在准直光子束中照射的TLDs，由于对高能光子的积累不足，没有任何滤片的TLDs或TLD徽章开窗下的TLDs的响应会显著降低，而对于动力反应堆的非准直辐射场，则会观察到过响应。据观察，剂量计使用不当封装不仅会在穿透辐射剂量估算中导致重大误差，而且在加压重水反应堆领域经常遇到的β辐射、高能伽马射线和高能电子混合场中的β剂量估算中也会导致重大误差。
