x ray tubes

Thermionic emission

Hot metal filament that gives off electrons

Heated by filament current

Space charge

electrons emitted remain near filament when no kV is applied

How are x ray and heat produced

kinetic energy of electrons

How many circuits are in a x ray circuit

2

What is the glass envelope made of

pyrex

What is degassing 

When the tube is baked during manufacture to expel air and gass

What is the glass enveloped emersed in

insulating oil

What does a filament consist of

a high and low voltage wire

How many filaments do x ray tubes usually have

2

Speed of rotating anode

3600 rmp

10,000 rpm for high speed

Angle of anode 

10-17 degrees 

How many focal spots does a anode have

2

What are fractional focus tubes

Tubes designed for magnification radiography with .3mm

Purpose of fractional focus tubes

increase resolution

Anode heel affect

intensity of beam is greater at cathode side

Line focus principle

using an angle on the target will increase effectiveness of the focal spot

Effective focal spot is smaller than the actual focal spot

Function of the stator in a rotating anode 

Spin the rotor

Leaking radiation must not exceed

10 mR/hr at 1 meter

The space charge effect refers to:

difficulty pulling electrons away from the filament at low kvp

Most tube failures occur at the 

filament 

What is the focusing cup made of

nickel

Force with which the electron stream passes from cathode to anode is a result of ____ passing through the x ray tube

Kilovoltage

What is used to determine how fast an x ray tube will dissipate heat after several exposure

Anode cooling curve

What temperature does an x ray tube filament exhibit significant thermionic emission

2500 C

What component of the x ray tube is a graphite disc having a tungsten rhenium track at its periphery

Anode

High frequency power

Has almost no ripple

Mutual induction is used in the operation of what device

Step up transformer

What metal are the filament wires in radiographic tubes made

Tungsten

What is used to focus the electron stream toward the target of the anode

Molybdenum focusing cup

What is a space charge compensator

maintains filament circuit when kV is charging

What does focusing cup do

focus and accelerates electrons to anode

Compensating filter

reduce effect of overexposure

equalized density across image

What does step up transformer do

converts volts to kilovolts