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Principles of Radiographic Exposures > X-ray tube components > Flashcards

X-ray tube components Flashcards

1
Q

What is the envelope made of

A

pyrex glass or metal

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2
Q

what is the purpose of the envelope

A

maintain a vacuum between the cathode and anode, protects inner parts

*why vacuum?
-photons and electrons travel w/o interacting w/ air (keeps X-ray precise)

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3
Q

What are the benefits of a metal envelope instead of glass

A

less likely to break
tube is grounded
better conductibility

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4
Q

What is the protective housing made of

A

Lead (on cathode end)
Steel

*why?
-helps reduce heat & leakage radiation

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5
Q

what is the purpose of the protective housing

A

controls leakage radiation
*any radiation coming out of tube somewhere other than the window

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6
Q

what is the maximum limit of leakage radiation

A

100 mR (milliRoentgen) per hour or
1 milligray per hour

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7
Q

What is the high-voltage isolation & tube cooling system made of

A

Dielectric oil
Air fan

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8
Q

what is the purpose of the high-voltage isolation & tube cooling system

A

Reduce heat and shock
helps cool tube

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9
Q

What is the filament made of

A

coil of thoriated tungsten

*why?
-high melting point
-does not vaporize easily

Note: rhenium and molybdenum are also good choices

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10
Q

is the filament on the cathode or anode end of the tube

A

Cathode (-)

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11
Q

what is the purpose of the filament

A

produce negative charge by boiling off electrons
*this is thermionic emission

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12
Q

why does filament size (length/width) matter

A

This is picked via focal spot
-impacts recorded detail

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13
Q

what kind of detail does a longer filament (Large focal Spot) have

A

Less (worse) detail

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14
Q

what kind of detail does a shorter filament (small focal spot) have

A

More (better) detail

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15
Q

what are the dimensions of the filament coil

A

0.1-0.2 mm thick
1-2 mm wide
10-20 mm long

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15
Q

what is the focusing cup made of

A

Nickel
*negative potential applied to narrow (concentrate) cloud of electrons

15
Q

what is the purpose of the focusing cup

A

concentrates electron beam towards focal track of the anode

Also holds filament

15
Q

what is a biased focusing cup

A

has higher negative potential, so cloud of electrons is narrowed even more

16
Q

what is the space charge effect

A

cloud of electrons gets so large; it stops more electrons from being boiled off of filament

17
Q

is the focusing part located within the cathode or anode side of the tube

A

Cathode (-)

18
Q

what is the focal track made of

A

where electrons strike it is made of tungsten-rhenium alloy

*why?
-thermal conductivity
-high melting point
-high atomic #
(more electrons available for more interactions to occur)

19
Q

what is the back/base of the anode made of

A

Molybdenum and/or graphite

*why?
-lighter material allows for easier rotation
-high conductibility
-thermal dissipation

20
Q

What is the purpose of the anode

A

It is the target surface where electrons get projected off X-ray photons are created

Electrical conductor
-taking electron source & heat then putting it back in circuitry

Thermal dissipator
-prevents overheating

21
Q

what is actual focal spot

A

where electrons strike the rotating anode

22
Q

what is effective focal spot

A

where electrons are projected off the anode as X-ray photons

23
Q

what are the dimensions of the rotating anode

A

5-13 cm in diameter with
3600-10000 rpm (rotations per minute)

Anode angles range from 7-17 degrees
(12 most common & required for 14x17 at 40” SID)

24
Q

what are other names for target

A

focal track
focal spot
focal point
focus

25
Q

what is the point source of X-ray photons

A

Anode

26
Q

is the rotating anode a part of the cathode or anode side of the tube

A

Anode (+)

27
Q

what is the line focus principle

A

larger actual focal spot minimizes effective focal spot (allows clearer images)
*controlled by actual focal spot and its angle

28
Q

what is the stator made of

A

bank of electromagnets

29
Q

what is the purpose of the stator

A

induces current/electricity to flow to rotor (Causes rotor to rotate)

30
Q

what is unique about the stator

A

-it is one part of the mutual induction motor

-located outside the envelope

31
Q

Is the stator a part of the cathode or anode side of the tube

A

Anode (+)

32
Q

what is the rotor made of

A

copper cylinder connected to anode disk by Anode (molybdenum) stem

33
Q

what is the purpose of the rotor

A

turns when stator is energized

34
Q

what is unique about the rotor

A

-it is the 2nd part of induction motor

-ball bearings located between shaft & copper cuff

35
Q

is the rotor part of the cathode or anode side of the tube

A

Anode (+)

Principles of Radiographic Exposures (1 decks)

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