Domen Steve R, Lamperti Paul J
Institute for Basic Standards, National Bureau of Standards, Washington, D.C. 20234.
J Res Natl Bur Stand A Phys Chem. 1974 Sep-Oct;78A(5):595-610. doi: 10.6028/jres.078A.037.
A new type of 3-body calorimeter for measuring absorbed dose produced by ionizing radiation is described in detail. All three bodies rise in temperature during irradiation, and the heat absorbed by the central core is measured by standard means. Only the central core is heated during electrical calibration, but the increased heat losses are compensated by measuring most of the heat lost to the surrounding jacket and automatically adding it to the heat retained by the core. The third body is a massive, thermally-floating shield, whose presence reduces the heat losses during irradiation, with a consequent increase in sensitivity and stability. A mathematical description of the calorimeter behavior is presented, along with a discussion of control and operation technique. In particular, it is shown how this 3-body calorimeter can be calibrated as a 1-body calorimeter, with large heat losses, or as a 2-body calorimeter, in the quasi-adiabatic mode. This calorimeter design decreases the effects of thermal gradients and at the same time provides the means to test for these effects. The results of these tests show that for this particular model, systematic errors caused by thermal gradients, during electrical measurements, are no larger than 0.1 percent. Errors in comparing an electrical run with an irradiation may be somewhat larger because of different temperature gradients within the system. It is also pointed out that the general design of this calorimeter is not restricted to measuring absorbed dose but can be applied to calorimetry in general.
详细描述了一种用于测量电离辐射产生的吸收剂量的新型三体热量计。在辐照期间，所有三个物体的温度都会升高，并且通过标准方法测量中心芯吸收的热量。在电校准期间，仅中心芯被加热，但通过测量散失到周围外套的大部分热量并自动将其添加到芯保留的热量中来补偿增加的热损失。第三个物体是一个巨大的、热浮动屏蔽，其存在减少了辐照期间的热损失，从而提高了灵敏度和稳定性。给出了热量计行为的数学描述，以及对控制和操作技术的讨论。特别展示了这种三体热量计如何可以作为具有大热损失的一体热量计或在准绝热模式下作为二体热量计进行校准。这种热量计设计减少了热梯度的影响，同时提供了测试这些影响的方法。这些测试结果表明，对于这个特定型号，在电测量期间由热梯度引起的系统误差不大于0.1%。由于系统内不同的温度梯度，将电运行与辐照进行比较时的误差可能会稍大一些。还指出，这种热量计的总体设计不限于测量吸收剂量，而是一般可应用于量热法。
