Pseudo-Lock-in Light Detection Method for a Sinusoidally-Gain-Modulated Photomultiplier Tube

In order to detect a weak signal varied in an intensive background light, we propose a novel pseudo-lock-in light detection scheme used for a photomultiplier tube (PMT) whose gain is modulated sinusoidally. Let the signal light incident on the PMT be modulated sinusoidally at a frequency f. In this situation, one of the dynode voltages applied for the PMT is deeply biased and a sinusoidal reference signal with a frequency f is superimposed on the bias voltage. Then, we detect a frequency component of 2f at the output of the PMT selectively. To pick up only the 2f component, we connect a digital oscilloscope directly to the output of the PMT. Thereafter the digitized waveform stored on a temporal memory of the digital oscilloscope is fast-Fourier-transformed (FFT). Two numerical values obtained from the resultant amplitude and the phase spectrum at the frequency 2f, respectively, correspond to the intensity and the phase of the modulated signal light incident on the PMT. A fundamental performance test of the proposed scheme was carried out.     

新型位置灵敏光电倍增管的性能测量

位置灵敏型光电倍增管(PS-PMT)代表了基于单个管子的原理开发新概念γ相机的技术进步.最近,日本滨松公司出品了一种新型紧凑型的PSPMT—R7600-C12.根据正电子放射断层成像系统(PET)的应用特点,我们测试了由该PS-PMT组合成的闪烁晶体阵列探测器的空间分辨率、空间线性度、增益均匀性及时间分辨率LSO与该PS-PMT的组合空间分辨率达到1.4mm,而且显示出良好的空间线性、增益均匀性及优异的时间分辨特性.     

一维位置敏感探测器位置准确度和线性度的改进

在常规的条状一维位置敏感探测器（PSD）中,光敏区和位置电阻区是结合在一起的,器件的欧姆接触电极难以做得比较理想,因此器件的位置准确度和线性度也受到了不利的影响。而在梳状一维位置敏感探测器中,光敏区和位置电阻区被分成了梳齿区和梳脊区两部分,并且位置电阻区被设计成很窄的长条,即使掺杂浓度比较高,位置电阻也能做得相当大。这样条状一维位置敏感探测器接触电极上的缺陷就可消除。用两种不同的一维位置敏感探测器所测量的位置特性曲线证实了理论分析的正确性。测量结果还表明,梳状一维位置敏感探测器的位置准确度和线性度比条状一维位置敏感探测器有了显著的提高,梳状一维位置敏感探测器的平均位置误差从条状一维位置敏感探测器的55μm减小到了26μm,梳状一维位置敏感探测器的均方根非线性度从条状一维位置敏感探测器的0．94％减小到了0．09％。     

微悬臂梁探测器的理论模型及优化设计

对基于微悬臂梁的光学和红外探测技术进行了理论分析,并建立了相应的理论模型,在此基础上对该类探测器进行了优化设计,包括：微悬臂梁材料的优化选择、金属镀膜材料及厚度的优化选择以及光辐射吸收层材料的选择。最终给出了一种新型的三层结构微悬臂梁探测器,理论上这种新型结构的探测器比现报道的同类探测器灵敏度高出20多倍,噪声等效功率降低了85％－70％。     

Phase transitions in hadronic systems and thermodynamics of a system with an exponential spectrum

Both nuclear matter and hadronic matter at high excitations can be described by a liquid-vapor phase transition. For the hadronic systems, a system with an exponential mass spectrum (Hagedorn-like or bag-like) leads to a thermodynamics which is identical to that of a two phase coexistence at a fixed temperature.     

Fast Analysis for the Focusing of a Laser Beam with Amplitude Modulation and Phase Fluctuation Through an Aperture Lens

Based on the treatment that a rectangular function can be expanded into an approximate sum of complex Gaussian functions with finite numbers, the analytical expression for the focusing intensity distribution of a laser beam with amplitude modulation (AM) and phase fluctuation (PF) through an aperture lens is derived. The typical numerical examples are given and compared with those obtained from numerically integral calculation. The results show that our method can significantly improve the numerical calculation efficiency.     

Fast Analysis for the Focusing of a Laser Beam with Amplitude Modulation and Phase Fluctuation Through an Aperture Lens

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Phase estimation of phase shifts in two arms for an SU(1,1) interferometer with coherent and squeezed vacuum states

We theoretically study the quantum Fisher information(QFI) of the SU(1,1) interferometer with phase shifts in two arms by coherent ? squeezed vacuum state input, and give the comparison with the result of phase shift only in one arm.Different from the traditional Mach–Zehnder interferometer, the QFI of single-arm case for an SU(1,1) interferometer can be slightly higher or lower than that of two-arm case, which depends on the intensities of the two arms of the interferometer.For coherent ? squeezed vacuum state input with a fixed mean photon number, the optimal sensitivity is achieved with a squeezed vacuum input in one mode and the vacuum input in the other.     

Algebra of Effects in the Formalism of Quantum Mechanics on Phase Space as an M. V. and a Heyting Effect Algebra

We prove that the algebra of effects in the phase space formalism of quantum mechanics forms an M. V. effect algebra and moreover a Heyting effect algebra. It contains no nontrivial projections. We equip this algebra with certain nontrivial projections by passing to the limit of the quantum expectation with respect to any density operator. PACS: Primary 02.10.Gd, 03.65.Bz, Secondary 002.20.Qs This paper was a submission to the Sixth International Quantum Structure Association Conference (QS6), which took place in Vienna, Austria, July 1–7, 2002.     

The Use of a Triple Pass Optical Arrangement for the Determination of Arsenic and Selenium by Atomic Absorption Spectroscopy in an Inert Gas Shielded Nitrous Oxide-Acetylene Flame

The utility of the inert gas shielded nitrous oxide-acetylene flame for the determination of arsenic and selenium by atomic absorption spectrometry has been demonstrated elsewhere¹. The low background absorbance of the fuel-rich, 50 mm path-length flame (ca 4 and 5% at the As 193.7 and Se 196.0 nm lines respectively) permits the attainment of detection limits which are equal to, or somewhat superior to, those obtainable with the air-acetylene flame. The AAS sensitivity (that concentration producing 1% absorption), however, is decreased; this is the result of the shorter path length of this flame compared to that employed for air-acetylene (100 mm) and the lower concentration of analyte produced in the larger volume of gas used to support the flame.