Look through the texts A-B again and make notes under the following headings. Then use your notes to talk about it

Follow-up Activities

1. The ‘Closed-loop’, the ‘S-gun’ and Planar Magnetrons.

2. Coating Structure and Morphology.

3. The Materials Suitable for Thin Films.

4. Titanium, its Alloys and Properties.

5. Vacuum History in Evolution.

Unit IV. Magnetron: Operation
and Application (part 2)

Before you start: Think it over. Agree-Disagree

“Invention brings invention.” Emerson, Ralf Waldo

Note: Emerson Ralph Waldo, 1803-82, US essayist and poet

“The real history and lore lie in the origins.” Anon

Reading, Vocabulary & Creative Practice

1. Words to be remembered.

available dramatic knock out schematic

apply drift linkage split-anode

cavity expansion microwave oven sustain

collision external quality tool

component frequency drift radar urgent

current glow relax voltage

domestic influence resonant vacuum-tube

drastic klystron result in wavelength

2. Translate the sentences. Pay attention to the words in italics.

1) Sorry, every available computer is now occupied.

2) Apply the paint evenly to both sides of the plate.

3) Cavity is a hole or hollow space in a solid mass.

4) Two people were injured in collision between a bus and a car.

5) The current is strongest in the middle of the river.

6) Domestic electric goods shouldn’t be expensive.

7) The scientist made a dramatic announcement.

8) This medicine is for external use.

9) He is likely to be influenced by his parents.

10) Klystrons are used in radar circuits to amplify microwaves.

11) Microwave ovens are an integral part of the modern kitchen.

12) A schematic shows the main outlines but leaves out many details.

13) He couldn’t sustain his interest to such kind of books.

14) It is not urgent: it can wait till tomorrow.

15) Voltage is electrical force measured in volts.

16) Wavelength is a distance between one wave and another.

3. Read text A carefully paying attention to the words in bold type.

A. Magnetron History (continuation)

There are more than one method of depositing PVD coatings, magnetron sputtering and arc evaporation being among them. But what is magnetron itself? In electronics, it is a two-element vacuum tube in which the flow of electrons is under the influence of an external magnetic field, used to generate extremely short radio waves.

In 1921 Albert Wallace Hull from New York invented the magnetron as a powerful microwave tube. His two-pole magnetron, also known as a split-anode magnetron, had relatively low efficiency. The cavity version proved to be far more useful. There was an urgent need during radar development in World War II for a high-power microwave generator that worked in a shorter wavelength – around 10 cm rather than 150 cm – available from two-based generators of the time. It is known that multi-cavity resonant magnetron was developed in 1935 by Hans Hallmann in Berlin. However, the German military considered its frequency drift to be undesirable, and based their radar systems on the klystron instead. It was for this reason that German night fighter radars were never a match for their British counterparts.

Since then, many millions of cavity magnetrons have been manufactured:

some for radar, but the vast majority for another application far more domestic – the microwave oven. In radars developers have moved to klystron and traveling wave tube systems.

Comprehension Check – 1

4. Decide whether the following statements are true or false according to text A.

1. There is only one method of depositing PVD coatings.

2. Magnetron is a personal name of a scientist.

3. In 1921 Albert Hull invented the magnetron as a powerful microwave tube.

4. Hull’s magnetron is known as a split-anode magnetron.

5. The cavity version of a magnetron proved to be more useful.

6. In World War there was a great need in a high power microwave generator.

7. Multi-cavity magnetron was developed in Berlin.

8. The German military based their radar system on the klystron.

9. There was only one cavity magnetron in the world.

10. Cavity magnetrons are used for radars and domestic purposes.

5. Answer the following questions to text A.

1. How does magnetron used in electronics look like

2. What magnetron did Albert Hull invent?

3. When did Albert Hull invent the split-anode magnetron?

4. What was the disadvantage of Hull’s magnetron?

5. What was an urgent need during radar development in World War II?

6. Who invented multi-cavity resonant magnetron?

7. Did the German military make use of cavity magnetron?

8. What did the German military base their radar systems on?

9. Where are cavity magnetrons used now?

6. Read text B carefully paying attention to the words in bold type.

B. Unbalanced Magnetron. Magnetron Application

An unbalanced magnetron possesses stronger magnets on the outside resulting in the expansion of the plasma away from the surface of the target towards the substrate. In an unbalanced magnetron, the outer North poles are stronger than the inner South poles. Therefore the field lines stretch further into the vacuum chamber. The effect of the unbalanced magnetic field is to trap fast moving secondary electrons that escape from the target surface. These electrons undergo ionizing collisions with neutral gas atoms away from the target surface and produce a greater number of ions and further electrons in the region of the substrate, considerably increasing the substrate ion bombardment. Effectively a secondary plasma is formed in the region of the substrate. When a negative bias is applied to the substrate, ions from this secondary plasma are accelerated to the substrate and bombard it; this ion bombardment is used to control the many properties of the growing film.

With the development of the unbalanced magnetron the substrate ion current that could be achieved and therefore the quality of the coatings increased dramatically. But more was to come with the development of multi-magnetron geometry with magnetic field linkage.

How is a magnetron used to coat tools and components?

While coating tools and components when power is supplied to the magnetron a negative voltage of typically –300V or more is applied to the target. This attracts argon ions to the target surface at speed. When they collide with the surface two important processes take place: Firstly atoms are knocked out of the target surface with mean kinetic energies of 4 to 6 eV – this is sputtering. Secondly, secondary electrons are emitted from the target surface that become trapped by the magnetic fields and undergo further ionizing collisions sustaining the plasma.

Also during the sputtering process a glow is observed. It is caused by excited ions relaxing to a lower energy state and emitting energy in the form of light. Different elements emit the visible light at a different wavelength and therefore a different color will be observed.

A magnetron consists of a plate of the material of which all or part of the coating is to consist with magnets arranged behind it with alternating polarity. See below the basic schematic of a magnetron.

² The basic schematic of a magnetron accompanied by arrows showing target; water cooling; magnets; target backing plate; magnetic field lines; vacuum chamber; N – S; S – N.

7. Decide whether the following statements are true or false according to text B.

1. An unbalanced magnetron possesses stronger magnets on the outside.

2. Unbalanced magnetron improved the quality of coatings.

3. During the sputtering process a thunderstorm is observed.

4. Magnets are necessary in magnetrons.

5. During the sputtering process a nuclear explosion takes place.

6. The nuclear explosion is caused by excited ions.

7. A magnetron consists of various precious stones.

8. A magnetron consists of a plate.

8. Answer the following questions to text B.

1. Does an unbalanced magnetron possess stronger magnets on the outside?

2. What happens when a negative bias is applied to the substrate?

3. How did the quality of coatings change with the unbalanced magnetron?

4. How is magnetron used for coating tools and components?

5. Why is a glow observed during a sputtering process?

6. What does a magnetron consist of?

7. How many important processes do take place when the collision occurs?

8. Is it easy or difficult to describe the basic schematic of a magnetron?

Comprehension Check – 2

9. Fill in the correct prepositions from texts A and B, then choose any of the sentences and develop the idea.

A) 1. There are more than one method __ depositing PVD coatings.

2. Albert Hull invented the magnetron __ a powerful microwave tube.

3. There was an urgent need __ radar development __ World War II.

4. Multi-cavity resonant magnetron was developed __ Hans Hallmann.

B) 1. It attracts argon ions __ the target surface __ speed.

2. When they collide __ the surface two important processes are applied.

3. Secondly, secondary electrons are emitted __ the target surface.

4. The glow is caused __ excited ions.

10. Make sure you know the meanings of these words. Match the words with their definitions.

a) klystron; b) quality; c) radar; d) sustain; e) voltage; f) drastic

1) high standard, goodness or worth; something that is special.

2) the use of radio waves to discover the presence and distance of an object.

3) keep up, maintain.

4) the electrical energy that moves charge around a circuit.

5) a type of valve which amplifies oscillations (колебания) of a high frequency in the microwave range (диапазон).

6) having a strong or violent effect

11. Match the words with the synonyms.

1) manufacture 5) escape a) have e) productivity

2) dramatically 6) supply b) produce f) significantly

3) possess 7) mean c) provide g) disappear

4) efficiency 8) region d) average h) area

12. Match the words with their antonyms.

1) low 5) outside a) positive e) unavailable

2) short 6) outer b) long f) undesirable

3) available 7) negative c) inside g) high

4) desirable 8) fast d) slow h) inner

13. Translate the following sentences into English.

1. С тех пор выпущено немало многорезонаторных магнетронов.

2. С развитием разбалансированного магнетрона качество покрытий значительно возросло.

3. Это притягивает ионы аргона к поверхности мишени с повышенной скоростью.

4. Во время процесса напыления наблюдается свечение.

5. На схеме обозначаются магниты, подложка мишени, силовые линии магнитного поля, водяное охлаждение.

6. Магнетрон (от греч. magnetis – магнит – и … трон) – это также мощный электровакуумный СВЧ прибор.

14. Skim the text “History” below. Use a dictionary. Make an abstract of the following text “History”, using such formulas as:
the text says about, it deals with, it can be divided into some parts, it gives information about, the author comes to the conclusion that, etc.

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