Development of high sensitive measuring system of radiation using ESR

镧系离子掺杂钾芒硝晶体（K_3Na（SO_4）_2）经X射线辐照后产生顺磁自由基（SO_3、SO_4）。SO_3^-自由基具有各向同性和热稳定性。Gd离子或Y离子掺杂的K_3Na（SO_4）_2中SO_3 ~-自由基的ESR信号强度明显增强。为了研究SO_3 ~-自由基的产生机理，采用热释光（TL）光谱法测量了基质晶体中Ln离子的存在情况。K_3Na（SO_4）_2掺杂Pr、Nd、Gd、Y或Tm离子后，其热释光光谱均为三价Ln离子的跃迁。特别是Gd离子和Y离子掺杂的K_3Na（SO_4）_2的热释光更强。而K_3Na（SO_4）_2掺杂稳定的三价La离子后，没有出现热释光光谱。Eu离子或Sm离子掺杂的K_3Na（SO_4）_2分别显示出由二价Eu离子或二价和三价Sm离子跃迁引起的TL光谱。结果表明，SO_2的产生是由于 ...更多信息 在K_3Na（SO_4）_2晶体中掺入与Na离子大小相近的稳定的三价Ln离子，可显著促进3^-自由基的生成，并尝试将Gd离子掺杂的K_3Na（SO_4）_2晶体应用于ESR成像方法中，实现对吸收剂量和辐照方向的同时监测。Zupancic型线圈用于产生具有ESR成像方向的磁场梯度。Zupancic型线圈的平行导线彼此连接并连接到电流源，形成四个独立的电流回路以改变磁场的方向。用X波段ESR谱仪测量了样品的ESR谱，该谱仪配有100 kHz的磁场调制器和相敏检波器。四个回路的电流值通过使用四个调节直流电源控制的12位D/A转换器来控制。使用滤波反投影（FBP）方法从通过使用1.05mT mm 2的场梯度获得的180个方向（1度步长）的投影数据重建二维图像<-1>。实验结果表明，Gd离子掺杂的K_3Na（SO_4）_2在20 μ戈伊~ 100戈伊范围内可用作ESR CT图像和ESR剂量计。少

The paramagnetic radicals (SO_3, SO_4) are produced in lanthanide (Ln) ion-doped glaserite crystal (K_3Na (SO_4) _2) after X-ray irradiation. The SO_3^- radical was isotropic and thermally stable. The ESR signal intensity of SO_3^- radical was remarkably high in Gd ion-or Y ion-doped K_3Na (SO_4) _2. In order to investigate production mechanism of SO_3^- radical, the existence of Ln ion in host crystal was measured by means of thermoluminescence (TL) spectroscopy. K_3Na (SO_4) _2 doped with Pr, Nd, Gd, Y,or Tm ion revealed the TL spectrum derived from the transition of trivalent Ln ion. Especially, TL of K_3Na (SO_4) _2 doped with Gd ion or Y ion was strongly bright. However, K_3Na (SO_4) _2 doped with stable trivalent La ion did not reveal the TL spectrum. K_3Na (SO_4) _2 doped with Eu ion or Sm ion revealed the TL spectrum due to the transition of divalent Eu ion or the transitions of divalent and trivalent Sm ion, respectively. The results obtained suggest that the production of SO_ … More 3^- radical was remarkably promoted by doping stable trivalent Ln ion of which size is similar to one of Na ion in host crystal.We attempted the application of the Gd ion-doped K_3Na (SO_4) _2 to the ESR imaging method which can monitor both absorbed dose and irradiation direction. Zupancic-typed coils were used to produce the magnetic field gradient with a direction for ESR imaging. The parallel wires of Zupancic-typed coils were connected to each other and to the current sources, forming four independent current loops to change the direction of magnetic field. The ESR spectrum were measured using an X-band ESR spectrometer with a 100kHz magnetic field modulator and a phase-sensitive detector. The current values of the four loops were controlled by using four regulated DC power supplies controlled 12 bit D/A converters. A two-dimensional image was reconstructed using a filtered back projection (FBP) method from the projection data of 180 directions (1-degree steps), which were obtained by using a field gradient of 1.05mT mm^<-1>. The obtained results suggested that the Gd ion-doped K_3Na (SO_4) _2 can be utilized as the ESR-CT image and the ESR dosimeter in the range from 20 mu Gy to 100Gy. Less