Narrow Results

In this paper, a two-detector measuring system in in-air PIXE system composed of two Si(Li) detectors has been developed for simultaneous measurement of low- and high-Z elements. In order to improve detection sensitivity of the detector for low energy region, a new device which is attached at the tip of the detector has been designed. It is made of acryl and has a thin end on which a 1.5 μm-thick Mylar film is stuck. As a result, it exhibited a miraculous effect in improving detection sensitivity at low energies and it became possible to detect K X-rays of aluminium. In order to perform quantitative analysis in in-air system, we have measured detection efficiencies for the two Si(Li) detectors including the effect of X-ray absorption in air on the basis of the method that we developed. Concerning the beam energy at the target and corresponding X-ray production cross-sections, the same values as were reported in the previous paper were applicable since conditions of irradiating system were unchanged. It was confirmed that the new method allows us to quantitatively analyze all the elements heavier than aluminum and to obtain mostly the same results as those by in-vacuum PIXE for various kinds of samples. Accuracy of analysis was also confirmed by using a standard material.

To obtain certain information such as metabolic concentrations in neural or muscular tissues and other applications, it is necessary to design nuclear magnetic resonance (NMR) transmitters/receivers capable of operating at multiple frequencies, while maintaining a good performance at each frequencies. We have proposed a new NMR receiver front-end for simultaneous detection of proton and carbon nucleus. The system consists of two reception coils for carbon and hydrogen analysis, a multiband low-noise amplifier (LNA) for increasing the voltage level and a network for passive amplification, noise figure minimization and decreasing mutuality effect between two coils. The proposed coil set was designed, simulated and analyzed and also the signal to noise ratio (SNR) with quality factor have been calculated for it by simulation. The LNA has been designed in a 0.18$\mu$m CMOS technology and its gains for carbon and proton NMR signals are 45 and 48dB, respectively. The input referred noise for both signals is lower than 0.4nV/sqrt(Hz) and the power consumption is 4 mA from a single 1.8V supply.

Neutron detection using gadolinium (Gd) and its prompt gamma-rays is vital because of the high cross-section of Gd on thermal neutrons, thereby leading to significant interest in neutron detection with Gd-converted or Gd-loaded detector. However, simultaneous detection of neutron and gamma-rays with a Gd-loaded scintillator has been given less attention. In this study, we explored the feasibility of the GdI₃:Ce detector for simultaneous detection with Monte Carlo N-Particle transport extended simulation. Furthermore, we examined the physical properties of Gd for application in the radiation field mixed with neutron and gamma-rays. Similarly, we simulated the geometry of the GdI₃:Ce scintillator and its spectra obtained under various conditions. The results showed that GdI₃:Ce with a thickness of 1cm is enough to absorb 90$\%$ of photons with energy under 81keV. A shorter source-to-detector distance and larger detector size were superior to detecting prompt gamma-rays emitted from neutron capture, not only the gamma-rays from isomeric transition (named as general gamma-ray in this paper). Ultimately, spectra taken with the Gd₃:Ce scintillator under the radiation field mixed with neutrons and gamma-ray showed gamma-ray peaks from both radio-isotopes and Gd$(n\gamma )$Gd reaction, indicating the feasibility of the application of simultaneous detection.

A simple pyrolysis, activation and hydrothermal method was utilized to synthesize composite materials (Fe₃O₄/SFP) of ferroferric oxide and nitrogen self-doped sunflower plate-derived carbon for the simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The Fe₃O₄/SFP had synergistic catalytic effect on target molecules, and the oxidation peak potential of AA, DA and UA was well distinguished in the differential pulse voltammetry determination. Under the optimal conditions, the linear response ranges of AA, DA and UA are 3–150$\mu$M, 5–450$\mu$M and 15–1200$\mu$M, respectively. The detection limits of AA, DA and UA ($S$/$N=3$) are 1.0$\mu$M, 0.4$\mu$M and 1.48$\mu$M, respectively, and the sensitivity is 1.87$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (3–20$\mu$M) and 0.64$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (20–150$\mu$M) for AA, 3.90$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (5–20$\mu$M) and 1.21$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (20–450$\mu$M) for DA and 1.12$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (15–100$\mu$M) and 0.31$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (100–1200$\mu$M) for UA. In addition, satisfactory results have been obtained for the determination of AA, DA and UA in normal human serum, which provides a new research direction for the construction of electrochemical sensors in the future.