Collimators are fabricated using the above tungsten alloy and 304 stainless steel material as cladding. The tungsten alloy shield for the tungsten directional collimator is designed to provide a 50 degree radiation beam and is encased with stainless steel and totally sealed by argon arc welding.

When an exposure is taken with tungsten directional collimator attached to the exposure head of the guide tube of gamma camera, the radiation beam coming out will have a 50 degree solid angle in the forward direction. The primary radiation beam intensity in all other area except the front side will be reduced to 5% with the collimator.

At a source to film distance (SFD) of 50 cm, the beam will cover an area of a circle with 24 cm radius which is sufficient to cover a film size of 37 cm x 30 cm. Overall size : 44 mm dia x 82 mm long. Weight : 1.15kg.

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Tungsten powders were prepared by Self-propagating High-temperature Synthesis (SHS) method directly from hitherto unreported system: sodium tungstate (Na₂WO₄) and magnesium (Mg). The adiabatic temperatures of self-propagating combustion reactions with different amount of Mg in Na₂WO₄ + Mg system were calculated. The influences of different starting conditions (molar ratios of Mg/Na₂WO₄ and relative densities of samples) on the compositions and microstructure of reaction products were investigated. It shown that, the complete reduction of WO₃ required a 60% excess of magnesium over the stoichiometric molar ratio Mg/Na₂WO₄ of 3. The amount of the impurities is minimal at appropriate relative density. At last, tungsten powders can be obtained after the acid enrichment and distilled water washing.

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The tungsten collimator kit is a main component of medical X-ray detector. This detector system was designed to simultaneously measure the X-Ray tube peak potential (kVp), and to characterize the mammographic X-Ray tube spectrum.

The components of tungsten collimator kit:

Stainless steel collimator housing

1. Tripod and mounting plate
2. Laser pointer
3. Brass Spacer
4. 7 Tungsten (W) Collimator disks:

• 1 mm thick with 25 µm hole
• 1 mm thick with 50 µm hole
• 2 mm thick with 100 µm hole
• 2 mm thick with 200 µm hole
• 2 mm thick with 400 µm hole
• 2 mm thick with 1000 µm hole
• 2 mm thick with 2000 µm hole

All Tungsten disks are made of alloy HD17 (90% W, 6% Ni, 4% Cu). All Tungsten disks and spacers have a diameter of 0.625 inches. This Tungsten (W) Spacer /Collimator is 36 mm thick with a 300 µm hole. It is designed to stop and collimate x-rays greater than 100 keV produced from high energy tubes.
 

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Both radiotherapy and most effective chemotherapeutic agents induce different types of DNA damage. Here we show that tungstate modulates cell response to DNA damaging agents. Cells treated with tungstate were more sensitive to etoposide, phleomycin and ionizing radiation (IR), all of which induce DNA double-strand breaks (DSBs). Tungstate also modulated the activation of the central DSB signalling kinase, ATM, in response to these agents. These effects required the functionality of the Mre11-Nbs1-Rad50 (MRN) complex and were mimicked by the inhibition of PP2A phosphatase. Therefore, tungstate may have adjuvant activity when combined with DNA-damaging agents in the treatment of several malignancies.

 

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Amorphous anodic oxide films on InAlP have been grown at high efficiency in sodium tungstate electrolyte. The films are shown to comprise an outer layer containing indium species, an intermediate layer containing indium and aluminium species and an inner layer containing indium, aluminium and phosphorus species_. The layering correlates with the influence on cation migration rates of the energies of In³⁺–O, Al³⁺–O and P⁵⁺–O bonds, which increase in this order. The film surface becomes increasingly rough with increase of the anodizing voltage as pores develop in the film, which appear to be associated with generation of oxygen gas.

 

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Due to unknown effects of the potential exposure of the terrestrial environment to tungsten substances, a series of toxicity studies of sodium tungstate (Na₂WO₄) was conducted. The effect on earthworm (Eisenia fetida) survival and reproduction was examined using Organisation for Economic Co-operation and Development (OECD) Guideline 222. No effect on either endpoint was seen at the highest concentration tested, resulting in a 56-d no-observed-effect concentration (NOEC) of ≥586 mg tungsten/kg dry soil (nominal concentrations). The effect of sodium tungstate on emergence and growth of plant species was examined according to OECD Guideline 208: oat (Avena sativa), radish (Raphanus sativus), and lettuce (Lactuca sativa). No effects on emergence, shoot height, and dry shoot weight were observed in oats exposed to the highest concentration, resulting in a 21-d NOEC of ≥586 mg tungsten/kg dry soil. The NOECs for radish and lettuce were 65 and 21.7 mg tungsten/kg dry soil (nominal concentrations), respectively. Respective 21-d median effective concentration values (EC50) for radish and lettuce were >586 and 313 mg tungsten/kg dry soil (based on shoot height) (confidence level [CL] -8.5-615); EC25 values were 152 (CL 0-331) and 55 (CL 0-114) mg tungsten/kg dry soil. Results are consistent with the few other tungsten substance terrestrial toxicity studies in the literature.

 

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Fluorescence, excitation, and pulsed fluorescence measurements have been made on a single crystal of CaWO₄ over a wide temperature range. The temperature dependences of the integrated fluorescence intensities and lifetimes were obtained for different excitation wavelengths. A sharp increase in the fluorescence lifetimes is observed below about 75°K and zero‐phonon lines can be observed. These results are used to formulate a model for the tungstate luminescent center based on the ion in a crystal field of S ₄ symmetry. Energy migration and impurity trapping effects are also discussed.

 

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The influence of annealing in different atmospheres on absorption and luminescent properties of high-quality undoped CaWO₄ single crystals is presented. The decreasing of green emission intensity after annealing in oxygen and air have been revealed, while two well-defined maxima near 25,000 and 32,000cm^-1 can be observed in the induced absorption spectra. These maxima are attributed to the interstitial oxygen, possibly in the form of the O⁻-centre. The increase of the blue/green luminescence ratio has been revealed after annealing in nitrogen while the crystal transparency remains unaffected. The possible ways to reduce slow green emission component without changing crystal absorption are shown. Structure of colour centres and the models of revealed processes are discussed.

 

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The geff=30/7 isotropic signal in the EPR of high-spin Fe3+ compounds is discussed for both tetragonal rhombic crystal fields by reference to the resonance in calcium tungstate. The Fe3+/CaWO4 EPR signals are shown to arise from Fe3+ in two slightly different interstitial sites in the crystal; the crystal field in both sites is predominantly rhombic. Highly anisotropic signals arising from transitions within the other two Kramers' doublets were positively identified leading to an unambiguous calculation of the spin Hamiltonian parameters. The results are likely to be of great value in analysing similar Fe3+ spectra in crystals of biological importance.

 

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Tungsten tetrachloride is a black needle-like crystals, orthorhombic structure, at 300-500 ℃will cause disproportionation reaction to generate tungsten hexachloride and tungsten dichloride. Tungsten tetrachloride at 475 ℃ and vacuum can produce by aluminum or white phosphorus restore to tungsten hexachloride. Tungsten tetrachloride producing processes are as follows:
1.In an inert gas oven, mixed 5g tungsten hexachloride and polytetrafluoroethylene，  put them into bottom No.6 from the manifold No.4 as is shown in the picture. Then fusion seal manifold No.4. Cooled No.6 with dry ice, and open the cock which made by polytetrafluoroethylene exhaust from manifold No.2.
2.Using the vacuum distillation method introduced refined dehydration tetrachlorethylene from the outside to bottom No.6 reach 30mL. After recovery at room temperature, vacuum and dipped No.6 into transparent oil bath with a 500W light bulbs, at 150 ℃ for 3 days.
3.After the reaction is cooled and upside downs the device, precipitated by a glass filter from manifold No.3.
4.In the oven which filled with inert gas, cut off the bottom No.6, remove product on the glass filter.

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