Ch. 5 The X-Ray Tube

Question 1

what is the rotating anode disc mounted on and why

Answer 1

copper shaft with a molybdenum core, copper for thermal and electric conductive properties, molybdenum for low-thermal conductivity and light weight but strong alloy

Question 2

Heat unit capacity formula

Answer 2

kVp x mA x s x c x # of exposures

Question 3

what is the stator made up and where is it located

Answer 3

electromagnets arranged in pairs around the rotor, located outside the tube enclosure

Question 4

what is the core of the anode disc made of and why

Answer 4

molybdenum for low thermal conductivity and light but strong alloy

Question 5

general purpose tubes are capable of rotating the anode at what speed

Answer 5

3400 rpm

Question 6

angle of target face is <45 degrees

Answer 6

line focus principle

Question 7

what is the correction factor for three-phase, 6 pulse generator

Answer 7

1.35

Question 8

what is tungsten’s melting point

Answer 8

3400c; 6152f

Question 9

what is tungsten’s atomic number

Answer 9

74

Question 10

what is the correction factor for high frequency generators

Answer 10

1.45

Question 11

what is sometimes added to tungsten on the anode target and why

Answer 11

Rhenium to increase thermal capacity and tensile strength

Question 12

what do we call the cloud of electrons in the focusing cup

Answer 12

space charge

Question 13

primary purpose of enclosure of the x-ray tube

Answer 13

maintain vacuum

Question 14

specialty tubes are capable of spinning the anode at what speed

Answer 14

10,000 rpm

Question 15

what is the rotating disc coated with and why

Answer 15

tungsten for its high melting point and thermal conductivity

Question 16

anode disc mounts onto shaft made of what

Answer 16

copper for its thermal and electrical conductive properties
molybdenum core for low thermal conductivity

Question 17

origin of the x-ray beam; area seen from patients perspective

Answer 17

effective focal spot

Question 18

area being bombarded by the filament electrons

Answer 18

actual focal spot

Question 19

what is the single phase generator correction factor

Answer 19

1

Question 20

glass envelopes are usually made from

Answer 20

pyrex glass/borosilicate glass

Question 21

what is the rotor made up of and where is it located

Answer 21

iron core - iron bars embedded in copper shaft surrounded by coils, located in center of stator within enclosure

Question 22

what circuit are the filaments connected to

Answer 22

filament circuit

Question 23

the anode is rotated using what

Answer 23

induction motor

Question 24

where does the voltage come from and go to

Answer 24

autotransformer to the step-up transformer

Question 25

what are filaments made of

Answer 25

tungsten with 1-2% thorium

Question 26

appropriate leakage allowed outside the housing

Answer 26

1mGy/hr at 1 meter

Question 27

filament heats and emits electrons to the point it can’t produce anymore, what do we call this

Answer 27

saturation current

Question 28

what is the correction factor for three-phase, 12 pulse generator

Answer 28

1.41

Question 29

what is the focusing cup made of

Answer 29

nickel

Question 30

what is the rotating anode disc made of and why

Answer 30

molybdenum for low thermal conductivity coated in tungsten for high melting point and thermal conductivity

Question 31

how big is the target window on enclosures usually

Answer 31

5 cm

Question 32

what is the focusing cup connected to

Answer 32

secondary circuit

Question 33

as tubes age, vaporized tungsten from the filament deposits on the inside of the glass envelope known as

Answer 33

sun tanning

Question 34

what is the x-ray tube coated in

Answer 34

di-electric oil

Question 35

why is tungsten used for the filament and why is thorium added

Answer 35

tungsten’s high melting point and it doesn’t vaporize easily, thorium is added to increase thermionic emission and extend filament life

Question 36

what does the stationary anode consist of

Answer 36

tungsten button inside a copper rod

Question 37

what are the target angle’s for general purpose tubes

Answer 37

7-18 degrees, 12 most common

Question 38

systems can record and display many shades of grey in digital technology known as

Answer 38

dynamic range