WDX-PIXE analysis of low energy X-rays using a microbeam

A high-energy resolution PIXE system developed at a heavy ion microbeam line was used to analyze low energy X-rays below 1 keV. The system is equipped with a plane crystal spectrometer with a gas flow position sensitive proportional counter (PSPC), which enables high-energy resolution PIXE analysis using a microbeam. In order to improve the detection efficiency for the low energy X-rays, the X-ray entrance window of the PSPC was replaced with a thin polymer film supported by a metal grid. As the result, the detectable energy range was extended to carbon K X-rays and chemical effect in Fe and Cu L X-rays could be detected. A preliminary result of high-energy resolution PIXE mapping of Cu mesh (#500) showed that it is possible to obtain the Cu L mapping image using a 2 MeV proton microbeam with the size of 20 × 20 μm.     

Measurement of tungsten impurity spectra with a two-crystal X-ray crystal spectrometer on EAST

Spectral measurement of tungsten (W) impurity is essential to study impurity transport. Therefore, an X-ray crystal spectrometer (XCS) on EAST was used to measure the line spectra from highly ionized W ions. On EAST, both poloidal XCS and tangential XCS have been developed to measure the plasma temperature as well as the rotation velocity. Recently, He-like and H-like argon spectra have also been obtained using a two-crystal setup. W lines are identified in this study. Through a careful analysis, the W lines of 3.9336, 3.9321, and 3.664 Å are found to be diffracted by He-like or H-like crystals. The lines are confirmed with the NIST database. We also calculated the ion temperature with Doppler broadening of these lines. The ion temperature from the W lines is entirely consistent with that from Ar line spectra. The measurement of these W line spectra could be used to study W impurity transport in future work.     

A comparison between pixe and rbs thin film thickness measurements in binary targets

A method for measuring the thickness of a light element thin film deposited on a heavy substrate, using particle induced X-ray emission (PIXE) at low energies (below 0.7 MeV) is described. The lines detected are the L X-rays of the substrate. The procedure is explained by means of the aluminum-tungsten system. A comparison with Rutherford backscattering spectrometry (RBS) of protons is made, showing that, in the same incident energy range, the latter gives unreliable results, while PIXE is fairly accurate.     

Energy spectra measurements of X-ray emission from electron interaction in a dense plasma focus device

Electrons generated during a pinch implosion in a hollow anode Mather-like plasma focus device (PF) are considered as a possible X-ray source via the impinging of those particles on medium and high-Z targets. A usual PF device has been slightly modified to optimise the X-ray production and their measurements by means of a suitable and non-invasive spectrometer. This ensemble allows measurements of X-rays generated booth by electrons turning back to the anode and by target collision of the so-called relativistic electron beam. The spectrum of the emitted photons is evaluated by using a differential absorption based technique. The X-ray spectrometer consists of a stack of LiF dosimeters which act both as detectors and filters to give curves of attenuated intensities. Finally, the energy distribution is calculated from such attenuation curves using an iterative procedure based on spectral algebra formalism.     

Observation of the evanescent wave excited by proton beam

An exit angle dependence of the intensity of carbon K line during proton bombardment was measured to observe the evanescent wave. A Soller type spectrometer was used to measure the intensity of X-ray lines. A mirror polished Si (1 1 1) wafer was used as a substrate and carbon was deposited onto this surface. As a result a curious exit angle dependence which is similar to the evanescent wave of X-rays was found . The calculated transmission coefficient of X-ray evanescent wave is compared with measured exit angle dependence of X-ray emission. The experimental and theoretical values are in good agreement. Utilization of this phenomenon permits to enhance the surface sensitivity of the PIXE analysis method.     

Parametric X-rays generated by electrons in multilayer mirrors mounted inside a betatron

The measured characteristics of tunable, quasi-monochromatic X-rays from thin multilayer mirrors used as radiators mounted inside a 35 MeV betatron chamber are presented. Parametric X-ray radiation (PXR) was generated by 15-33 MeV electrons passing through two radiators consisted of a few hundreds of W/B4C bilayers with period of 14.86 and 18 A. Shifts of the PXR spectra were measured as the orientation of the multilayer radiators relative to the incident electron beam was changed. The PXR flux was determined by comparison with the yield of L fluorescence generated by electrons in the W layers of the multilayer.     

Étude comparée de la perfection cristalline de monocristaux de zirconium α par la méthode de berg et par diffractomètre à platine oméga

The perfection of a zirconium crystals obtained from a localized phase transformation method was characterized by two X-rays diffraction techniques. First the Berg method was applied using a classical diffractometer on which a camera was mounted; once the optimal experimental conditions determined, the relationship between the width of the diffracted spot and the misorientation was established for various diffracting planes. After that, another method based on a diffractometer equipped with an omega device had led to the determination of the misorientation from the width of the diffraction peak when the Bragg angle corresponding to a given set of crystallographic planes is modified by a small angular value. Results obtained by these two methods on the same crystals are in good agreement, and different misorientation from 0.01 and 5.3° have been easily measured. The possibility of characterizing with accuracy by these techniques the degree of perfection of α zirconium crystals allows us to study the influence of subboundaries in diffusion processes and/or in oxidation phenomena.     

A new analysis chamber with a rotating target holder for total-sample PIXE analysis of aerosol deposits collected in Berner impactors

We describe an external PIXE analysis chamber provided with means for determining the total amount of aerosol material sampled in Berner impactors. The deposits are concentrated in equally spaced small spots along a circle with a diameter of 50 mm. To pass the whole distribution of material through the probing proton beam, the thin backing film is mounted on a rotatable target holder. Driven by a motor, the holder is rotating at a speed of typically 1/min. Depending on the total duration of the analysis, the sample is rotated 3–10 times through the beam. For high sample throughput the analysis chamber is coupled to a helium-backfilled transfer box in which six holders can be stored, at the same pressure as in the analysis chamber. Loading of the transfer box, with a minimum loss of helium, is accomplished by activating load locks on either side of the box. The first experience gained with aerosol samples as well as with dedicated reference standards is discussed with particular reference to the uniformity of aerosol deposits.     

Beta and X-ray spectrometer for monitoring of beta-radiating nuclides

The design and characteristics of the spectrometer for beta-particles and conversion electrons in the energy range from 15 to 3000 keV and X-ray radiation from 2 to 60 keV are presented. Radiation is detected by a 4.5-mm-thick SiLi detector with a sensitive area of 500 mm/sup 2/. The energy resolution for conversion electrons with the energy of 624 keV is 2.0 keV and, for X-rays with the energy of 5.9 keV, is 280 eV.     

Design of Time-Resolved Shifted Dual Transmission Grating Spectrometer for the X-Ray Spectrum Diagnostics

A new time-resolved shifted dual transmission grating spectrometer(SDTGS) is designed and fabricated in this work. This SDTGS uses a new shifted dual transmission grating(SDTG) as its dispersive component, which has two sub transmission gratings with different line densities, of 2000 lines/mm and 5000 lines/mm. The axes of the two sub transmission gratings in SDTG are horizontally and vertically shifted a certain distance to measure a broad range of 0.1–5 keV time-resolved X-ray spectra. The SDTG has been calibrated with a soft X-ray beam of the synchrotron radiation facility and its diffraction efficiency is also measured. The designed SDTGS can take full use of the space on a record panel and improve the precision for measuring spatial and temporal spectrum simultaneously. It will be a promising application for accurate diagnosis of the soft X-ray spectrum in inertial confinement fusion.     

Radiation Emission Correlated with the Evolution of Current Sheath from a Deuterium Plasma Focus

The time resolved emission of neutrons and X-rays (both soft and hard) is correlated with the current sheath evolution during the radial phase of a 3.2 kJ Mather-type plasma focus device operated in deuterium at an optimised pressure of 4 mbar. A three-frame computer-controlled laser shadowgraphy system was incorporated in the experiment to investigate the time evolution of the radial phase of the plasma focus. The dynamics of the sheath was then correlated with the time resolved X-rays and neutron emission. The time-resolved neuron and hard X-ray emission was detected by a Scintillator-photomultiplier system while the time resolved soft X-rays were detected employing filtered PIN photo diodes. The observations were recorded with a temporal accuracy of a few ns. For the reference, the total neutron yield was also monitored by an Indium Foil activation detector. The correlation with the High Voltage Probe signal of the discharge, together with the X-ray and neutron emission regimes enabled to identify the important periods of the sheath evolution i.e. the radial compression (pre focus), minimum pinch radius (focus) and the post focus phenomena. During the initial stage of the radial phase, velocities of 10–23 cm/μs, while at the later stage of the radial phase (up till the compression), velocities up to 32–42 cm/μs were measured in our experiment. For the discharges with the lower neutron yield (lower than the average value ~1 × 10⁸ n/discharge), the current sheath appears to be disturbed and neutron and hard X-ray signal profiles do not carry much information whereas the soft X-ray emission is significant. For the discharges with high neutron yield (higher than the average value), the current sheath has a smooth structure until the maximum compression occurs. Hard X-ray emission is maximum for the discharges with high neutron yield, especially whenever there is development of m = 0 instability compressing the column to very high densities. The neutron are emitted long after the maximum compression supporting the beam target fusion. For the discharges with High neutron yield, the soft X-ray production is less as compared to the discharges with low neutron yield.     

瞬发γ射线中子活化分析的现状与发展

概述了瞬发γ射线中子活化分析(PGNAA)的现状与发展，重点介绍了PGNAA的基本原理，国际上已建的PGNAA装置概况、PGNAA方法学中的单比较器k0法和高能γ射线的效率刻度技术，以及PGNAA在新材料、环境样品、生物和药物以及矿物中H、B、N、Cl等轻元素分析测定方面的日益发展的应用状况。此外，还介绍了在中国原子能科学研究院重水研究堆上建立的热中子束PGNAA实验装置。     

多束脉冲作用下韧致辐射转换靶照射量模拟

20MeV的强流脉冲电子束经加速聚焦后轰击韧致辐射转换靶,在产生脉冲X光的同时将大量能量沉积在靶内,导致靶材迅速膨胀飞散。在多个束脉冲作用下,后续脉冲由于靶材密度的降低可能无法产生足够的X光照射量。本文采用Monte-Carlo软件MCNP以及流体动力学软件ANSYSAUTODYN对靶材的动力学响应以及各脉冲所能产生的照射量进行了数值模拟,结果表明,在3个间隔500ns的20MeV、2kA、70ns、束斑1.5mm（FWHM）的电子束脉冲作用下,X光照射量无明显降低。     

Chemical effects in the Kβ X-ray emission spectra of sulfur

In this work our previous study about chemical effects in the K spectra of S compounds employing high-resolution X-ray spectroscopy has been extended to the Kβ emission spectra. The measurements were performed with a wavelength dispersive single crystal spectrometer operated in the von Hamos geometry having an energy resolution comparable to the natural linewidth of the measured Kβ X-ray lines. The target fluorescence was produced by irradiating the samples with the bremsstrahlung from an X-ray tube. The energies and widths of the main components in the Kβ emission spectrum are given for different sulfur compounds (sulfide, sulfite, sulfate). The measured energy shifts between the Kβ lines of the compounds and elemental sulfur are presented as a function of the sulfur oxidation state and compared with the results obtained from the former K measurements.     

The Characteristics of an Ultra-High Resolution Ge(Li) Spectrometer for Singles and Coincidence X-Ray and Gamma-Ray Studies

The use of an ultra-high resolution Ge(Li) photon spectrometer in low and high energy X-ray and gamma-ray measurements has been evaluated. Studies were made of the resolution, low energy cutoff, the full energy and K X-ray escape efficiencies, tha effective detector dead layer and the detector linearity. The detector was used simultaneously with a high resolution Si(Li) detector to measure fast coincidences between Ka1 , Ka2 and L X-rays, as well as coincidences between K, L conversion electrons and L X-rays. A detailed discussion is presented of the electronic problems associated with making these kind of measurements. Measurements were also made of X-ray beams produced by clinical X-ray machines at 40, 78 and 220 kV.     

一个PIXE-RBS离子束分析系统的刻度

四川大学原子核科学技术研究所依托2.5 MeV范德格拉夫静电加速器搭建了质子诱发X射线荧光分析(Proton Induced X-ray Emission,PIXE)与卢瑟福背散射分析(Rutherford Backscattering Spectrometry,RBS)相结合的离子束分析系统,描述了该分析系统和刻度过程。通过10个金属单质的PIXE-RBS测量,刻度得到的仪器常数H值是一条随能量变化的曲线,然后采用最小二乘法拟合确定了X射线探测器前的Mylar膜有效厚度、选择性滤膜的有效厚度和中心小孔大小,从而得到H值。为了对刻度H值进行检验,在相同实验条件下测量了标准粘土样品元素成分,测量数据与证书数据符合得较好。刻度结果将用于以后的PIXE-RBS分析。     

Accurate calibration of a Si(Li) detector for PIXE analysis

Two methods for obtaining thin target PIXE K_α calibration factors were compared. The first (relative or experimental) method relied on two different sets of accurate thin film standards, while the second (absolute or theoretical) method involved the use of fundamental physical parameters and an experimental investigation of the Si(Li) detector's detection efficiency. Several critical facets of the calibration procedures are discussed or were carefully investigated. These include the incident beam energy determination, beam current integration, accuracy of thin film standards, solid angle and window thicknesses (Be, Au, Si) of the Si(Li) detector, net K_α peak area determination and tail-to-peak ratio as a function of X-ray energy, fluorescence yields and ionization cross sections. The experimental and theoretical calibration factors finally obtained showed excellent agreement, the average difference being only ～3.5%.     

A New Method for Measurements of the Poloidal Rotation Velocities and Wavelength Calibration of X-ray Imaging Crystal Spectrometer in Magnetic Fusion Devices

A new simple method is presented for the wavelength calibration and measurement of poloidal rotation velocities with X-ray imaging crystal spectrometer(XICS)in magnetic fusion devices.In this method,the toroidal rotation of plasma is applied for high precise alignment and wavelength calibration of the poloidal XICS.The measurement threshold of poloidal rotation velocity can be lowered to 1-3 km/s with this method.     

An intense channeling radiation source

A non-conventional X-ray source which is based on the production of electron channeling radiation in a diamond crystal has been installed at the radiation source ELBE. The brilliant electron beam with an average current of up to 200 μA allows to reach photon rates of quasi-monochromatic channeling radiation between 10¹⁰ s⁻¹ and 10¹¹ s⁻¹ per 10% bandwidth. The photon energy can be tuned by variation of the beam energy. On-line X-ray monitoring was realised at high beam currents using a Compton spectrometer. Monochromisation of channeling radiation and bremsstrahlung background reduction has been investigated applying X-ray diffraction at a highly ordered pyrolytic graphite crystal.     

X-rays generated by relativistic electrons in a waveguide radiator mounted inside a betatron

We have observed X-ray emission from an X-ray waveguide radiator excited by relativistic electrons in the experiments carried out at Tomsk betatron B-35. A stratified radiator of a new type was mounted on a goniometer head inside the betatron toroid. The radiator consisted of the W-C-W layers placed on Si substrate. The photographs of the angular distributions of the radiation generated in the radiator by 20 and 33 MeV electrons showed the waveguide effect of the three-layer structure on X-rays generated in the radiator. The effect appeared in the angular distribution of the radiation as an additional peak attributed to guided X-rays inside a wide cone of usual Bremsstrahlung.