一种新的微波热疗机输出功率定标方法

目的:针对目前微波热疗机所采用的功率定标方法中没有考虑辐射器的损耗的问题,设计一套测量微波热疗机实际输出功率的装置,提出一种新的对微波热疗机实际输出功率进行定标的方法.方法:利用控制系统控制磁控管阳极电流维持在某一预设值,利用小功率计测量由微波源产生的,经过同轴电缆的微波功率P_(同轴电缆).然后将辐射器接上同轴电缆,使辐射器辐射的微波被实验装置中的水完全吸收.通过测量水的温度变化计算出水吸收的微波能量.利用冷却速率计算实验装置散失的能量,最后由两者能量之和与时间的比例得出辐射器输出的功率P_(辐射器).与此同时,可由P_(同轴电缆)与P_(辐射器)的比值得出辐射器的效率η_(辐射器).结果:微波热疗机通过辐射器输出的实际微波功率与磁控管阳极电流的关系为:P_(辐射器)=2η_(辐射器)1,在不同阳极电流下,得出辐射器的效率为:η_(辐射器)=(34±1)%.结论:从实验结果得知,现行微波热疗机的功率定标方法是有缺陷的,它没有考虑辐射器的转换效率,因此它测量的不是微波热疗机输出的实际微波功率.而采用本文介绍的定标方法可以准确获得微波热疗机的实际输出功率.

New Method for Calibration the Output Power of Microwave Hyperthermia Apparatus

Objective: Nowadays, the power calibration methods of the microwave hyperthermia apparatus doesn't take the power loss of the radiator into account Aiming at this problem, the authors designed an equipment of measuring the actual output power of the microwave hyperthermia apparatus. A new method is proposed for calibration the output microwave power of microwave hyperthermia apparatus. Methods: The magnetron anode current was maintained at a default value by a control system. The microwave power generated by microwave source is coupled firstly to a low-power meter by the coaxial cable to measuring the power going through coaxial cable (P_(coaxial cable)). Then the microwave radiator is connected to the coaxial cable to make the microwave radiated by radiator. The radiator is assembled in the experimental device for the microwave completely absorbed by the water. The absorbed microwave energy of the water is calculated by measuring the water temperature change. The energy loss of the experimental device is calculated using the cooling rate. The output power of the radiator is equal to the ratio of the sum of the two aforementioned energy and the time. And the efficiency of the radiator η_(radiator), is equal to P_(radiator)/P_(coaxial cable) Results: The relationship between the actual output power of the microwave hyperthermia apparatus and the mag- netron anode current is P_(radiator) = 2η_(radiator) I. The efficiency of the radiator is η_(radiator)= (34±1)%. Conclusion: From the experimental results, the current method for calibration output power of microwave hyperthermia apparatus is defective, it dose not consider the conversion efficiency of radiator. Using the calibration method introduced in this paper, wecan accurately deter- mine the actual output power of microwave hyperthermia Apparatus.