Development of high sensitive measuring system of radiation using ESR

x射线照射后，镧系离子掺杂的玻璃石晶体（K_3Na (SO_4) _2）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。在Gd离子或Y离子掺杂的K_3Na (SO_4) _2中，SO_3^-自由基的ESR信号强度非常高。为了研究SO_3^-自由基的产生机理，采用热释光（TL）光谱法测定了主体晶体中Ln离子的存在。Pr、Nd、Gd、Y、Tm离子掺杂的K_3Na (SO_4) _2显示了由三价Ln离子跃迁产生的TL谱。特别是Gd离子或Y离子掺杂的K_3Na (SO_4) _2的TL亮度较强。而稳定三价La离子掺杂的K_3Na (SO_4) _2没有显示出TL谱。掺入Eu离子和Sm离子的K_3Na (SO_4) _2显示出TL谱，分别是由于Eu离子的二价跃迁和Sm离子的二价跃迁。结果表明，在基体中掺入尺寸与Na离子相近的稳定三价Ln离子，可显著促进SO_…More 3^-自由基的生成。我们尝试将Gd离子掺杂的K_3Na (SO_4) _2应用于ESR成像方法，可以同时监测吸收剂量和照射方向。采用zupancic型线圈产生有方向的磁场梯度，用于电磁共振成像。zupancic型线圈的并联导线相互连接，并与电流源连接，形成四个独立的电流回路，以改变磁场方向。采用带100kHz磁场调制器和相敏检测器的x波段ESR谱仪测量ESR谱。四个回路的电流值由四个稳压直流电源控制的12位D/A转换器控制。利用1.05mT mm^<-1>场梯度获得的180个方向（1度步长）投影数据，采用滤波反投影（FBP）方法重建二维图像。结果表明，Gd离子掺杂的K_3Na (SO_4) _2可以作为20 ~ 100Gy范围内的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