微通道板近紫外量子效率测量及成像研究

Measurement of Quantum Yield and Image of Microchannel Plate in Near Ultraviolet Band

提出了一种通过测量微通道板输出电流及增益来计算光电流,从而测量出微通道板量子效率的方法,并用该方法测量了微通道板在近紫外(200~380nm)的量子效率.测量结果表明,微通道板的量子效率很低,并且随波长增加而快速下降,200nm波长处的量子效率为10-4数量级,320nm波长处的量子效率为10-8数量级,大于340nm波长处的量子效率极低且趋近于零.微通道板及荧光屏组成的成像器件可以对酒精灯火焰成像,但图像较稀疏,而传统Cs2Te光电阴极紫外成像器件的图像却较密实,这与微通道板量子效率低,Cs2Te光电阴极量子效率高的情形一致.在该成像器件的前端放置一片350nm波长的高通滤光片后,所成的酒精灯火焰图像消失.对被照射目标成像时,如果照射光源为254nm的汞灯,则可以成像;但如果照射光源为365nm汞灯,则不能成像.说明微通道板的光谱响应主要在350nm波长以下,与其量子效率的测量结果一致.最后测量得到该成像器件的分辨力为32lp/mm,与传统Cs2Te光电阴极紫外成像器件的分辨力相同.微通道板及荧光屏组成的成像器件由于不使用光电阴极,具有价格低、寿命长且可靠性高的优点,因此可在紫外信号较强或成像距离较短的条件下使用.

A method is proposed to calculate the photocurrent by measuring the output current and gain of microchannel plate,so as to measure the quantum yield.The quantum yield is measured in the near ultraviolet(200~380 nm)by the proposed method.The measurement results show that the quantum yield of microchannel plate is very low,and decreases rapidly with the increase of wavelength.The quantum yield of 200 nm wavelength is 10-4 order of magnitude;the quantum yield of 320 nm wavelength is 10-8 order of magnitude,and the quantum yield after 340 nm wavelength is very low and almost zero.The imaging device composed of microchannel plate and fluorescent screen can image the flame of alcohol lighter,but the image is sparse,while the image of traditional Cs2 Te photocathode ultraviolet imaging device is dense,which is consistent with the situation of low quantum yield of microchannel plate and high quantum yield of Cs2 Te photocathode.When a 350 nm high pass filter is placed at the front of the imaging device,the detected flame image of the alcohol lighter disappears.When imaging the illuminated target,it can be imaged if the light source is a 254 nm mercury lamp;but it cannot be imaged,if the light source is a 365 nm mercury lamp.The results show that the spectral response of microchannel plate is mainly below 350 nm wavelength,which is consistent with the measurement results of quantum yield.Finally,the resolution of the imaging device is measured as 32 lp/mm,which is the same as that of the traditional Cs2 Te photocathode ultraviolet imaging device.Because the imaging device composed of microchannel plate and fluorescent screen does not use photocathode,it has the advantages of low price,long life and high reliability,so it can be used under the condition of strong ultraviolet signal or short imaging distance.