Radio Science - Exam 3 Review

Question 1

Typical incoming voltage to high voltage circuit

Answer 1

220 V

Question 2

Autotransformer

Answer 2

Makes adjustment to voltage before it’s stepped up

Question 3

Location of Autotransformer

Answer 3

Low-voltage side of High Voltage Circuit for safety

Question 4

Exposure switch/timer

Answer 4

Initiates exposure & terminates it in 1 of 3 ways

Question 5

3 ways exposure switch/timer

Answer 5

1. Manual timer
2. mAs timer
3. Automatic Exposure Control AEC

Question 6

Step-up transformer turns ratio range

Answer 6

500:1 to 1000:1

Question 7

Rectification bridge

Answer 7

-Diode that changes AC to DC
-When electrons approach n side, the electrons are repelled toward bridge
-Positive charge on p side repels its holes toward bridge
-At bridge, current can flow

Question 8

2 components of X-ray tube

Answer 8

Cathode
Anode

Question 9

Cathode

Answer 9

Negative side of X-ray tube
Thermionic emission

Question 10

Anode

Answer 10

Positive side of X-ray tube
X-ray production

Question 11

Rotor switch

Answer 11

Begins anode spin - 3400 rpm
Heats up filament within X-ray tube

Question 12

Thermionic emission

Answer 12

Boiling off electrons from filament due to high amperage & high resistance

Question 13

mA selection

Answer 13

Resistors

Question 14

Step-down transformer

Answer 14

Ratio of 1:44
mA increased by factor of 44, up to 5 amps

Question 15

Half-wave rectified & self-rectified circuits

Answer 15

60 pulses/sec
100% voltage ripple
30% average kVp

Question 16

Single-phase, Full-wave rectified

Answer 16

120 pulses/sec
100% voltage ripple
30% average kVp

Question 17

3-phase, 6-pulse generator

Answer 17

360 pulses/sec
14% voltage ripple
91% average kVp

Question 18

3-phase, 12-pulse generator

Answer 18

720 pulses/sec
4% voltage ripple
97% average kVp

Question 19

High frequency generator

Answer 19

< 500 pulse/sec
<1% voltage ripple
100% average KV = Peak KV
Smooth waveform

Question 20

Cathode contains ___ filaments

Answer 20

2
small = 1 cm
large = 1.5 - 2 cm

Question 21

Filaments are made of ___

Answer 21

Thorium-impregnated tungsten
Z= 90

Question 22

Purpose of thorium

Answer 22

Helps w/ heat tolerance

Question 23

Space charge

Answer 23

Electron cloud forming around filament when rotor button is pushed

Question 24

Focusing cup

Answer 24

Surrounds filaments
Prevents electrons from rushing away from each other
Resulting focal spot in anode is 5% size of filament – 0.5 - 1 mm

Question 25

Rotor

Answer 25

Connects to shaft & spins when influenced by stator (induction)

Question 26

Stator

Question 27

Target

Answer 27

Area of anode disk that's struck by electrons Made of tungsten & Rhenium (Z=75)

Question 28

X-ray tube failure

Answer 28

Arcing

Question 29

Arcing

Answer 29

-Vaporized tungsten coats inside of tube & leads to arcing during exposure -Type of short circuit -Cracks glass -Eliminates vacuum -Burns out filament

Question 30

Protecting X-ray tube

Answer 30

Warm-up procedure Avoid excessive rotoring Heat units Tube rating chart Anode cooling chart

Question 31

Warm-up procedure to prevent ____

Answer 31

thermal shock

Question 32

Heat units

Answer 32

Capacity of anode to withstand heat Heat units = constant x kVp x mA x exposure time Heat units = 1.4 x kVp x mA x time

Question 33

Tube rating chart

Answer 33

Ensure technique will not exceed heat capacity of X-ray tube

Question 34

Electrons can accelerate to speeds of more than ___ the speed of ___ in ___ inch

Answer 34

1/2 speed of light 1 inch

Question 35

Anode interactions

Answer 35

Heat Bremsstrahlung Characteristic

Question 36

Anode interactions - heat

Answer 36

99.5% of interactions at 60 kV 99% of interactions at 100 kV

Question 37

Anode interactions - Bremsstrahlung

Answer 37

Braking radiation due to interactions w/ nucleus Closer an electron passes to nucleus, the more it will be decelerated, more energy is lost in form of X-ray Average kV exiting X-ray tube after filtration is 1/3 the kVp setting Responsible for majority of created X-rays

Question 38

Characteristic X-ray formation

Answer 38

1. Projectile electron from cathode interacts w/ INNER shell electron - electron is ejected 2. Outer shell electron drops down to fill vacancy - energy released in form of X-ray 3. Free electrons outside atom can fill vacancy too 4. Strength of X-ray = difference between 2 binding energies

Question 39

Characteristic Cascade

Answer 39

Inner shell electrons replaced in sequence - multiple X-rays created K replaced by L, L by M, M by N, etc

Question 40

X-ray beam/emission spectrum

Answer 40

Complete graph of all X-rays exiting X-ray tube from combination of Bremsstrahlung & characteristic spectrum

Question 41

Factors affecting X-ray emission spectrum

Answer 41

Target material kVp mAs Added filtration Generator type

Question 42

X-ray emission spectrum - mAs

Answer 42

mAs directly controls number of X-rays exiting X-ray tube Doubling mAs will double number of X-rays created

Question 43

X-ray emission spectrum - Added filtration

Answer 43

Removes weak X-rays Thus, increases average kV Known as Hardening the X-ray beam

Question 44

X-ray emission spectrum - kVp

Answer 44

Increasing kVp will move X-ray emission spectrum to the right due to increased energy of resulting X-ray