Focused Practice

I. Answer the following questions:

1. What is magnetron sputtering?

2. What is the essential element of magnetron sputtering?

3. What does the planar magnetron source provide?

4. What does a large negative bias applied to the target accelerate?

5. How are secondary electrons and sputtered atoms emitted?

6. When is the efficiency of the generation of ions improved?

7. Where are large electric fields present in magnetron sputtering?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: Magnetron sputtering.

Unit 5 Grammar: The Passive Voice Word List:

1. strong particle-induced turbulence attenuation	ослабление сильной турбулентности (завихрения), обусловленной (наведенной, вызванной) частицами
2. wake	след (за телом в потоке), вихревая зона
3. eddy	вихревое движение, вихрь
4. particle Reynolds numbers	числа Рейнольдса для частиц
5. dissipating scales	значения рассеивания
6. center-plane	диаметральная плоскость
7. blower	нагнетатель воздуха
8. 10:1 contraction	десятикратное сужение

Particle-Induced Turbulence Attenuation

Experiments show that strong turbulence attenuation occurs with particle Reynolds numbers in the range of 10 to100. This indicates that the particles have long wakes which may have scales comparable to energy containing eddies in the flow. Distortion of eddies by these wakes is in some way responsible for the large reductions in turbulence levels. In a manner not fully understood, these wakes modify the turbulence so that energy is passed more rapidly from the energy containing eddies to the dissipating scales. This mechanism is studied by measuring the spatial structure and the dissipation rate for flows with strong particle-induced turbulence attenuation. In particular, the center-plane region of the fully-developed channel flow is examined. The experiments showed turbulence reductions by as much as a factor of 3 for particle mass loading ratios ranging up to 80 %.

The experiments were conducted in the vertical fully developed channel air-flow. The tunnel consists of an inlet and blower section, a flow conditioning section, a particle-feeding section, a 10:1contraction, a 5.2 m long development section, a test section, and a particle removal system. The particle feeding section provides a uniform and steady flow of particles that accelerate to their terminal velocity in the long development section. The development section also allows the gas flow to reach fully developed conditions. The acrylic test section has a channel half-width of 2 cm and a spanwise width of 46 cm. All experiments were conducted with a mean velocity of 10.5 m/s in the test section. The mean properties of the flow were largely unchanged by the addition of particles while the turbulence was changed substantially.