x-ray tube

Question 1

what are the features of the cathode ?

Answer 1

Filament
Focussing cup
Supporting wires

Question 2

what is the filament made out of ?

Answer 2

Tungsten

Question 3

whys if filament made out of Tungsten (hint- 4 points)

Answer 3

-Good thermionic emitter
-Low vapour pressure
Low evaporation rate
-Highly ductile
Easily made into wire
-Current

Question 4

Alternative methods of producing narrow beam of electrons exist

Answer 4

Changing the focussing cup
Changing the anode angle

Question 5

describe the features of the focusing cup

Answer 5

-negatively charged, this helps helps to accelerate the electrons towards the anode

• it is a shallow depression on the surface of the cathode, concentrates the electron beam towards the focal spot of the anode

Question 6

Larger
negative
potential=

Answer 6

more narrow bean

Question 7

anode angle ?

Answer 7

12 and 17 degrees.

Question 8

state 3 things as anode must be able to do
(hint-contradictions)

Answer 8

• Mange high atomic number for efficient X-ray production but must be light

-High amount of heat generated should be able to conduct this away as little as possible should be conducted along the anode stem towards the bearings and rotor.

-Bearings are in a vacuum and so cannot be lubricated.

Question 9

what type of motor used for anode

Answer 9

Induction motor used

Question 10

what is the anode made out of

Answer 10

tungston

Question 11

the result of decreasing the anode angle

Answer 11

reducing the anode angle, increases the heel thus increasing anode heel effect as there is now less intensity on the anode side

Question 12

do x-rays leave with a hugher intesnity on anode side or cathode side

Answer 12

cathode side due to the beam only travelling a short distance through the anode when it is the the cathode side, this is known as the heel effect

Question 13

explain heel effect

Answer 13

some x-rays once they hit the anode have to go through the anode, some more than others if the beams of e- are closer to the anode side they have to travel a further distance as they are going through more of the heel of the anode. thus x-ray beams on the anode side have a lower intensity.

Question 14

what happens once e- hit the target on the anode ?

Answer 14

-electron passes near the nucleus it is slowed and its path is deflected.
-Energy lost is emitted as a bremsstrahlung X-ray photon

Question 15

describe in detail what leads to the x-ray photon being emitted in terms of the e- and nucleus and magnetic field

Answer 15

The sudden change in motion of the electron, once it gets to close to the nucleus constitutes a violent acceleration, which disturbs the electromagnetic field and a photon of x-radiation is emitted.

Question 16

The principle of conservation of energy states that in producing an x-ray photon the electron has lost some of its kinetic energy and so is travelling more slowly than before the interaction. - is this a consequence or cause of the emission of an x-ray photon?

Answer 16

Consequence

Question 17

bremsstrahlung (braking radiation)

Answer 17

slowing down of the electron after x-ray photon has been releases

Question 18

describe Characteristic radiation

Answer 18

• high energy electron interacts with one of the inner shell electrons.

-energy is transferred to this electron for it to be ejected from the atom ie the atom has been ionised

-outer shell electrons move into the inner shells but to do this they have to release some of their energy as the lower shells represent a lower energy state.

• The energy is released by the emission of a photon of electromagnetic radiation.

Question 19

what does the high voltage between the anode and the cathode cause

Answer 19

Accelerates electrons towards positive anode

Question 20

define volatge

Answer 20

Voltage is maximum kinetic energy of electron