Molybdenum Target Research Articles

Metals and metal oxides particles produced by pulsed laser ablation under high vacuum

A pulsed KrF Excimer laser (248 nm, 15 mJ) was utilized to synthesize different particles on (111) Si substrate under vacuum \sim 10^{-6} torr using Aluminum (Al), Platinum (Pt), Tungsten (W), Molybdenum (Mo), Cadmium Oxide (CdO), and Yttrium Oxide (Y_2O_3) targets. Scanning electron microscope (SEM) was used to study particle size distribution on silicon substrate. The size of individual metal particles was found to be ranging from 71 nm to 2 \mu m whereas metal oxides particles were found in the range of 71 nm to 1.1 \mu m. The particles below 100 nm are formed by gas phase condensation of ions, atoms and molecules whereas particles greater than 100 nm size results either from the ejection of liquid droplets from the melt surface or stresses induced by laser on target surface. The advantage of particle formation due to laser ablation in high vacuum is pure particles production.

モリブデンターゲットＸ線管から放射されるＸ線スペクトルの推定計算式

A presumption calculating formula of the X-ray spectrum generated from a molybdenum target X-ray tube is presented. The calculation procedure is to add an amount of characteristic X-ray photons that corresponds to the ratio of characteristic photons and bremsstrahlung photons to the bremsstrahlung spectrum obtained using semiempirical calculation. The bremsstrahlung spectrum was calculated by using a corrected Tucker's formula. The corrected content was a formula for calculating the self-absorption length in the target that originated in the difference of the incident angle to the target of the electron and the mass stopping power data. The measured spectrum was separated into the bremsstrahlung component and the characteristic photon component, and the ratio of the characteristic photons and bremsstrahlung photons was obtained. The regression was derived from the function of the tube voltage. Based on this calculation procedure, computer software was constructed that can calculate an X-ray spectrum in arbitrary exposure conditions. The X-ray spectrum obtained from this presumption calculating formula and the measured X-ray spectrum corresponded well. This formula is very useful for analyzing various problems related to mammography by means of Monte Carlo simulations.

Establishment of the mammographic radiation qualities in industrial equipment: spectra determination

Abstract In this work, a Si(Li) detector was used to analyze mammographic X-ray spectra produced by an industrial equipment with Molybdenum (Mo) target, operating at constant tube potentials between 20 and 35 kV. Filters of Mo and Al of suitable thickness were added to the tube exit, in order to reproduce the radiation qualities of an X-ray mammographic equipment, as recommended by the International Electrotechnical Commission (IEC 61267) and the Physikalisch-Technischen Bundesanstalt (PTB). A detailed evaluation of the detector response functions was made using Monte Carlo simulations. The validity of this method was tested through comparisons with the experimental spectra of radioactive sources. The results showed that the Si(Li) detector exhibits good response function in low energy (between 5 and 20 keV). The measured X-ray spectra for a Mo filtration (0.03 mm thickness), corrected using the response functions, show a good agreement with the reference clinical spectra. The results of this work also show that both the radiation qualities implemented and the spectra shape are consistent with that obtained for mammographic X-ray beams, and they can be applied to calibration of the mammography measurements instruments (e.g. ionization chambers and dosimeters).

ED-XRF spectrometric analysis of comparative elemental composition of in vivo and in vitro roots of Andrographis paniculata (Burm.f.) Wall. ex Nees—a multi-medicinal herb

The multi-elemental composition of in vitro--proliferated root tissues of Andrographis paniculata (Burm.f.) Wall. ex Nees was compared with that of the naturally grown in vivo plants. Trace elements namely Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Rb, Sr and Pb in addition to two macro-elements K and Ca were identified and quantified in root tissues of both sources using the energy dispersive X-ray fluorescence (ED-XRF) technique. ED-XRF analysis was performed using Mo K X-rays generated from a secondary molybdenum target. The elemental content of in vitro roots was found to be at par with that of naturally grown plants of the same species. This opens up a possibility of exploiting in vitro root cultures as a viable, alternative and renewable source of phytochemicals of relevance, besides providing a means for conservation of the valuable natural resources.

The options for the future production of the medical isotope 99Mo

There is a shortage of medical isotopes in the world today. Two of the most important isotope producing reactors, the National Research Universal (NRU) reactor in Canada and the High Flux Reactor (HFR) in the Netherlands, are currently under repair. The main consequence is that the supply of 99Mo, the workhorse isotope of nuclear medicine, is far below the medical demand. This demand comes from >30 million patients worldwide that are diagnosed each year using 99mTc, the daughter isotope of 99Mo. Supply shortages will remain the case until these two reactors are returned to service. However, both these reactors are close to 50 years old, as are the three other main isotope producing reactors (BR2, Belgium, OSIRIS, France and SAFARI, South Africa, Fig. 1). Since it is expected that the clinical demand for 99mTc will remain strong for decades to come [1, 2], the remaining life time of these reactors is too short. The future of a significant part of nuclear medicine is therefore dependent on new reactors being built, or on new technologies being developed. Fig. 1 The contribution of the five most important reactors to world 99Mo production In several countries, the present shortage has given rise to studies on possible ways to resolve the problem. In Canada, it was originally planned to replace the NRU by two so-called MAPLE reactors, but that project was discontinued for technical reasons [3]. Subsequently, at the initiative of the Canadian Government, an independent expert panel reviewed a large number of different proposals for 99Mo production, in order to advise on the way forward [4]. In the USA a committee investigated options to move away from the current use of highly enriched uranium (HEU) as target material for 99Mo production [5]. In the Netherlands, a new multipurpose reactor Pallas [6] has been proposed. This prompted the Dutch government to commission an independent review of all possibilities to produce 99Mo in the future [7]. Such an important issue as the production of 99Mo has political, economic and scientific aspects. In this editorial we focus on a scientific comparison of all the options, using the results of the independent committees as a basis. First we discuss the current technology of irradiating HEU plates in reactors. Then we describe the possible alternatives for 99Mo production in four broad categories: molybdenum targets in reactors, target plates in accelerators, 99Mo extraction from liquid reactors and the replacement of the HEU targets by low enriched uranium (LEU). Finally we present conclusions, which are supported by the independent reviews mentioned above.

Backward transition radiation in EUV-region as a possible tool for beam diagnostics

In this paper we discuss the possibility of proof-of-principle experiment to observe backward transition radiation in EUV region as a first step for beam diagnostics. We have carried out simulations of backward transition radiation angular distributions in the EUV region for molybdenum target for different geometries. The simulation results are promising for beam diagnostics purposes.

Hydrogenic retention of high-Z refractory metals exposed to ITER divertor-relevant plasma conditions

Tungsten (W) and molybdenum (Mo) targets are exposed to the plasma conditions expected at the strike point of a detached ITER divertor (ne ∼ 1020 m−3, Te ∼ 2 eV) in the linear plasma device Pilot-PSI. The peak surface temperatures of the targets are ∼1600 K for W and ∼1100 K for Mo. The surface temperatures and plasma flux densities decrease radially towards the edges of the target due to the Gaussian distribution of electron density (ne) and temperature (Te) in the plasma column. A 2D spatial scan of the W and Mo targets using nuclear reaction analysis (NRA) shows D retention is strongly influenced by surface temperature in the range 800–1600 K and this dependence dominates over any plasma flux dependence. NRA and thermal desorption spectroscopy (TDS) show no clear dependence of retention on incident plasma fluence for the W targets with retained fractions ranging from 10−8–10−5 Dretained/Dincident. NRA and TDS for the Mo targets show retention rates a factor of 4–5 higher than the W targets and this is likely due to the lower surface temperatures for the Mo plasma exposures. NRA also reveals a thin boron layer on the Mo targets but the presence of boron does not correspond to a significant increase in D retention. Overall hydrogenic retention in W and Mo is shown to be low (Dretained = 1019–1020 D m−2) despite exposure to high plasma flux densities (∼1024 D m−2 s−1). This is likely due to the elevated surface temperature due to plasma thermal loading during exposure.

Molybdenum Target in the digital enviromnent, to study the image characteristics of early breast cancer

Objective To improve the pairs of molybdenum and rhodium target X ray of early breast cancer diagnostic accuracy. Methods 41 cases confirmed by surgery and pathology of early breast cancer X ray findings were analyzed retrospectively. Results signs of early breast cancer: 23 cases of nodular masses;calcification in 17 cases, X ray no clear lumps or nodules and calcification of the only 2 cases of malignant signs; non-symmetry of high density 12; limitations associated with skin thickening nipple retraction in 2 cases.Conclusion ①mass is an important basis for the diagnosis of early breast cancer;②micro-calcification is still an important basis for the diagnosis of early breast cancer, even more than the direct signs of (mass) more specific; ③non-symmetry of the limitations of dense breast structure of local distortions disorders, inflammation and surgical history of the exclusion, it should be possible to consider breast cancer ;④In addition to malignant calcification, the more than two kinds of indirect signs of co-exist, we should attach great importance to be further examination or short-term review. Key words: Early breast cancer; Rh-Mo double-target Photography Diagnosis

Threshold Voltage Tunability of p-Channel Metal Oxide Semiconductor Field-Effect Transistor with Ternary HfxMoyNz Metal Gate and Gd2O3 High-k Gate Dielectric

p-channel metal oxide semiconductor field-effect transistor (pMOSFET) devices with a ternary HfxMoyNz metal gate and a Gd2O3 high-k gate dielectric have been demonstrated for the first time. The nitrogen-concentration-control method is a simple and cost-effective technique for metal work-function modulation. HfxMoyNz thin films were cosputtered from pure hafnium (Hf) and molybdenum (Mo) targets in nitrogen (N2) and argon (Ar) mixtures. The HfxMoyNz thin films have low resistivity and high thermal stability up to 950 °C. The threshold voltage (Vth) of the HfxMoyNz/Gd2O3 pMOSFET can be tuned from -0.6 to -0.08 V by controlling the nitrogen flow ratio. Moreover, there is little negative bias temperature instability (NBTI) degradation of the HfxMoyNz/Gd2O3 pMOSFET device. Compared with the HfxMoyNz/SiO2 pMOSFET, the HfxMoyNz/Gd2O3 pMOSFET has a small threshold voltage modulation owing to the extrinsic Fermi level effect at the HfxMoyNz and Gd2O3 interface. A physical model has been proposed to explain the extrinsic Fermi level pinning effect of the HfxMoyNz/Gd2O3 pMOSFET device.

Backward transition radiation in EUV-region as a possible tool for beam diagnostics

In this paper we propose to use backward transition radiation in EUV region for micron and submicron beam diagnostics. We have carried out simulations of backward transition radiation characteristics in the EUV region for molybdenum target using two approaches. The simulation results show a good agreement for both approaches and are very promising for beam diagnostics purposes.

Note: Studies on target placement in TE111 cylindrical cavity of electron cyclotron resonance x-ray source for the enhancement of x-ray dose

X-ray source based on electron cyclotron resonance principle has been constructed using TE(111) cylindrical cavity. At present the device is used to provide low energy x-ray field for thermoluminescent dosimeter badge calibration. Theoretical and experimental studies on the effect of target placement inside the TE(111) cylindrical cavity for enhancing the x-ray output are carried out and the results are presented in this note. Optimum target location is identified by theoretical analysis on the electric field distribution inside the cavity using MICROWAVE STUDIO program. By modifying the magnetic field configuration, the resonance region is shifted to the optimum target location. The microwave transmission line is upgraded with a three stub tuner which improves the microwave coupling from the source to the target loaded cavity. Molybdenum target is located at a radial distance of 2.5 cm from the cavity center and the x-ray dose rate is measured at 20 cm from the exit port for different microwave power. With the introduction of the target, the x-ray output has improved nearly from 70% to 160% in the microwave power of 150-500 W.

Structural and electrical characterization of magnetron sputtered MoO3 thin films

Thin films of molybdenum oxide were deposited on glass and crystalline silicon substrates using dc magnetron sputtering method by sputtering of molybdenum target in the presence of oxygen and argon gas mixture under various oxygen partial pressures in the range 8×10-5 – 8×10-4 mbar. The glow discharge characteristics of the molybdenum cathode under various oxygen partial pressures were studied. The effect of oxygen partial pressure on the core level binding energy, structure, mechanical and electrical properties of the films was systematically studied. The films formed at oxygen partial pressures < 2×10-4 mbar contained the MoO3 and MoO3-x phases. The films deposited at oxygen partial pressures of 2×10-4 mbar were stoichiometric with single phase orthorhombic α- MoO3. The electrical conductivity of films decreased from 4×10-5 to 1.6×10-6 Ω-1cm-1 with increase of oxygen partial pressure from 8×10-5 to 8×10-4 mbar.

Monochromatic X-ray Imaging System Using a W/C Multilayer Mirror

The possibility of monochromatic X-ray imaging using a conventional X-ray tube and a tungstencarbon (W/C) multilayer mirror was examined. The W/C multilayer mirror was designed to choose the characteristic X-ray (17.5 keV) generated from an X-ray tube with a molybdenum target and was fabricated by using an ion-beam sputtering deposition system. The X-ray reflectivity and the monochromaticity of the W/C multilayer mirror combined with the X-ray tube were 0.62 and 0.26 keV, respectively. Monochromatic X-ray slit images for a test sample were obtained from the monochromatic X-ray imaging system with a scanning stage. The slit images were combined together, and a full sample image was obtained. The monochromatic X-ray imaging system showed a spatial resolution of 26 lp/mm at 10% MTF, a better contrast, and a better signal-to-noise ratio compared with polychromatic X-ray imaging.

Substrate temperature influenced structural, electrical and optical properties of dc magnetron sputtered MoO 3 films

Molybdenum oxide (MoO 3) films were deposited on glass and (1 1 1) silicon substrates by sputtering of metallic molybdenum target in an oxygen partial pressure of 2 × 10 −4 mbar and different substrate temperatures in the range 303–623 K using dc magnetron sputtering technique. X-ray photoelectron spectrum of the films formed at 303 K showed asymmetric Mo 3d 5/2 and Mo 3d 3/2 peaks due to the presence of mixed oxidation states of Mo 5+ and Mo 6+ while those deposited at substrate temperatures ≥473 K were in Mo 6+ oxidation state of MoO 3. The films formed at substrate temperatures ≥473 K were polycrystalline in nature with orthorhombic α-phase MoO 3. Fourier transform infrared spectra of the films showed an absorption band at 1000 cm −1 correspond to the stretching vibration of Mo O, the characteristic of the α-MoO 3 phase. The electrical resistivity increased from 3.3 × 10 3 to 8.3 × 10 4 Ω cm with the increase of substrate temperature from 303 to 473 K respectively due to improvement in the crystallinity of the films. Optical band gap of the films increased from 3.03 to 3.22 eV with the increase of substrate temperature from 303 to 523 K.

Value of ultrasound in diagnosing ductal carcinoma in situ

Objective To evaluate the value of ultrasound in diagnosing ductal carcinoma in situ (DCIS). Methods The sonographic characteristics of 12 DCIS which were confirmed by pathology were analyzed retrospectively. Results The ultrasound image of DCIS could be divided into four types;the solid mass nodule, mammary dysplasia, mix mass nodule, the dilated duct type. Micro calcification had high incidence rate. Ultrasonic diagnosis accordance rate was 50.0 %. On molybdenum target mammograms, the tumor appeared as a cluster of calcified spots in 8 cases, and the accuracy rate of diagnosis of was 66.7 %.Conclusion There are no typical characters of DCIS in ultrasound image. However, some characteristics are suggestive and can help to differentiate them from the benign tumors, such as small nodule, irregular shape,obscure boundary, and microcalcification. When sonography combine with molybdenum target mammography,the accuracy rate of diagnosis will be improved. Key words: Breast neoplasms; Ultrasound; Ductal carcinoma in situ; Intraductal carcinoma

A clinic value of ultrasonic diagnosis in breast carcinoma

Objective To probe into a meaning of ultrasonic diagnosis for galactophore cancer and a character of cancer ultrasonic image.Methods To analyze retrospectively 263 ultrasonic images with galactophore cancer,and to contrast with X molybdenum target photograph,and MRI.Results The discovering rate of ultrasonic for galactophore cacer was 87.45%(230/263).The ultrasonic images were numerous low echo of singleness focus,they were 96.58%(254/263),the edge of tumours were abnormity,the contours were fainmoss,they were like burr or crab legs(86.69%)(228/263);the edges were in order,the contours were in clarity but no envelopes 13.31%(35/263);the tumors in length and breadth＞1 were 90.49%(238/263);strong echo flecks in the tumors were 90.87%(239/263);the lymph node of armpit in 77.56%(204/263)patients were intumesce.The detection rate of galactophore cancer in X molybdenum target photograph was 96.74%(208/215),and MRI was 97.92%(47/48),they were all higher B ultrasonic(P＜0.01 or＜0.05).Conclusion The detection rate of galactophore cancer in ultrasonic is not as good as X molybdenum target photograph and MRI,but the ultrasonic is no-hurt,no-radioactivity and charge low so that it is a first way of galactophore cancer examination. Key words: Ultrasonic diagnosis; Breast cancer

Manufacturing of calcium, lithium and molybdenum targets for use in nuclear physics experiments

This paper describes methods used in the manufacturing of chemically reactive targets such as calcium ( natCa), lithium-6 ( 6Li) and molybdenum–97 ( 97Mo) for nuclear physics experiments at the iThemba LABS cyclotron facility (Faure, South Africa). Due to the chemical properties of these materials a suitable and controlled environment was established in order to minimize oxygen contamination of targets. Calcium was prepared by means of vacuum evaporation while lithium was cold rolled to a desired thickness. In the case of molybdenum, the metallic powder was melted under vacuum using an e-gun followed by cold rolling of the metal bead to a desired thickness. In addition, latest developments toward the establishment of a dedicated nuclear physics target laboratory are discussed.

Optimization of radiography applications using x‐ray beams emitted by compact accelerators. Part I. Monte Carlo study of the hard x‐ray spectrum

A 3-year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory-sized commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x rays emitted from thin targets, irradiated by electron beams circulating in the storage ring, is of primary interest for the design and the characterization of a beamline. This article, Part I, aims at optimizing some of the parameters which are critical for the design of medical applications based on the above compact light source. The goal was to evaluate the dependence of photon fluence and beam monochromaticity on electron-beam energy, target material, and thickness. The transport of 6 and 20 MeV electrons in a thin molybdenum, rhodium, and tungsten target is studied by means of Monte Carlo simulations using MCNPX. Configurations of the x-ray output port, different from the default forward-directed emission of the beam, are also investigated. A comparison with reference spectra for general diagnostic radiology and mammography is carried out. It is shown that the emitted x-ray beams can be far more intense than those generated by conventional x-ray tubes for radiography applications. The profiles of the calculated polychromatic spectra resemble those generated by conventional x-ray tubes, with x-ray energies up to the energy of the incident-electron beam. An appreciable improvement in the monochromaticity of the beams can be obtained by viewing the x-ray emission from an output port antiparallel to the direction of the incident-electron beam. The optimum target thickness for tungsten target spectra is practically constrained by a trade-off between bremsstrahlung efficiency and focal-spot size requirements. A larger margin for optimization of target thickness is probably available for mammographic spectra. The constraint of a backward-directed (or, to a lesser extent, orthogonal) output port is to be considered mandatory for minimizing the high-energy tail of the spectral distribution and keeping the radiation dose to a reasonable level. It is also fundamental to evaluate the impact of the high-energy tail of the emitted spectra in x-ray imaging applications, since the energy range involved is significantly beyond the diagnostic range. This topic will be dealt with in Part II of the article.

Bremsstrahlung spectra produced by kilovolt electron impact on thick targets

Measurements of bremsstrahlung spectra generated by 5–25 keV electron impact on thick targets of aluminium, titanium, zirconium, molybdenum and tungsten are reported. The experimental data are compared with the simulation results of X-ray spectra obtained from the general-purpose Monte Carlo code PENELOPE, which implements accurate cross-sections for ordinary bremsstrahlung emission but disregards polarization bremsstrahlung. The agreement between the experimental and simulation results is satisfactory. This is in contrast with a recent study in which large discrepancies were observed between experimental and Monte Carlo simulation results. Our results provide evidence for the reliability of the combined choices of the interaction cross-sections and of the simulation algorithms implemented in PENELOPE for bremsstrahlung emission.

Observation on Therapeutic Effects of Sanjiexiaopi Decoction Treating Hyperplasia of Mammary Gland during Premenstrual Phase

Objective To observe the therapeutic effect of periodical treatment of Sanjiexiaopi decoction on hyperplasia of mammary gland during premenstrual phase. Methods 110 cases were randomly recruited into a treatment group and a control group with 55 case in each group. The treatment group was given Sanjiexiaopi decoction 7 days before menstruation, and the control group was given Rupixiao tablet. Both groups received no treatment during menstruation and were treated for three months. Patients in both groups underwent molybdenum target X-ray photographs and infrascan before and after the treatment. Therapeutic effects of the two groups.were compared. Results The total effective rate was 96.4% and 81.8% in the treatment group and the control group respectively. The patients in treatment group showed obvious improvent than the control group in terms of X-ray photographs and infrascan, having statistical significance (P<0.05) . Conclusion Sanjiexiaopi decoction has obvious effects on hyperplasia of mammary gland during premenstrual phase. Key words: Hyperplasia of mamrnary gland; Premenstrual phase; Periodicity; Sanjiexiaopi decoction