7B.1 Particle Accelerators

Question 1

how do we investigate the internal structure of particles

Answer 1

by colliding them with other fast moving particles, and when they are hit hard enough they will disintegrate and show us there internal structure, as well as when they collide new particles form sometimes they are undiscovered

Question 2

why is it important to collide small particles at very high speeds (high energies)

Answer 2

because at low energies the particles just bounce off each other

Question 3

how can we change the direction of a charged particle while moving in a straight line in an electric field

Answer 3

by applying an eclectic field on it

Question 4

in linear accelerators how can we overcome the fact the there is a maximum limit for P.d applied

Answer 4

they are accelerated at different stages all with maximum P.d applied

Question 5

what is a linear accelerator

Answer 5

it is a machine which accelerates charged particles along a straight line

Question 6

what are the 3 machines that work as particle accelerators

Answer 6

1. linear accelerator
2. the cyclotron
3. synchrotron

Question 7

how do linear accelerators work

Answer 7

the electrons are made from a electrostatic machine, once they are made they are put in the linear accelerator, once they are inside the cylinder they move in a straight line through as the electrode is equally attracting in all directions, the altering voltage supply is made to change the supply as the electron reaches the middle of the tube so now the tube is negative and repeals the electrons to the second tube which is positive attracting it towards it once they reach the middle of the second tube the voltage is changed again and so on and so fourth until it reaches the end of the line where it would most likely hit a target

Question 8

what are the disadvantages of a linear accelerator

Answer 8

1. each tube needs to be successively larger and large to catch up wit the electrons increasing speed as the electron would go through each successive one with higher speed and the time in which the altering P.d is changes is set and cant be changed
2. it is limited by how long you build it
3. it must me a prefect straight line
   4.the whole structure needs to be in vacuum so the particles wont collide with air particles

Question 9

what is one of the claims that Einstein made in his theory of special relativity

Answer 9

nothing can accelerate beyond the speed of light

Question 10

is the claim that Einstein made “nothing can accelerate beyond the speed of light” true and if so how does it effect the particles being accelerated in a linear accelerator

Answer 10

it is true as Bertozzi demonstrated that at very high speeds, particles deviate from the equation 1/2mv^2= qV and never accelerate past the speed of light, he proved that by measuring the actual speeds of electrons accelerated by a van de graaff generator and then he determined their kinetic energy by colliding the with a target and measuring the heat generated , and the results showed that the accelerating P.d became more than the expected kinetic energy, this ended up demonstrating that the kinetic energy or the momentum of an electron increases without a limit but its speed doesn’t. so this can only happen if the mass of a particle seemingly increase with its speed and it becomes significant at the relativistic speeds, as in terms of particles in a linear accelerators they wont accelerate past the speed of light

Question 11

how did the scientist work around the disadvantage of having to build a longer and longer linear accelerators to reach faster speeds

Answer 11

they started to coil the accelerators up in a circle allowing the particles to be repeatedly accelerated in an electric field in a smaller space.

Question 12

why do we use a magnetic field in circular accelerators

Answer 12

because we can use the fact that charged particles moving through a magnetic field will move in a circular path and have a centripetal force acting on it, so we can work out the radius of the circular path and use it to build a circular accelerator with the right dimensions.

Question 13

what is the radius of a circular accelerator

Answer 13

r = mv/Bq (deriving this is found in page 88)

Question 14

the radius of a circular accelerator increase with

Answer 14

speed or square root of kinetic energy at slow speeds, and mass at relivistic speeds (always increases with momentum)

Question 15

what is a cyclotron

Answer 15

a circular machine that accelerates charged particles, usually following a spiral path

Question 16

what is the cyclotron made from

Answer 16

so the cyclotron is made from 2 d shaped electrodes (dees), a north and a south pole and a electric field in the middle of the gap between the dees and a altering voltage

Question 17

how do cyclotrons work

Answer 17

as the cyclotron is turned on the charged particle would be attracted to the oppositely charged Dee but because of the magnetic field acting it will be going in a circular path semi circles (since its acting in right angles to the magnetic field) once it leaves the oppositely charged Dee because of the magnetic field the voltage would flip making Dee 1 same charged and Dee 2 oppositely charged accelerating the charged particle and making the radius of its circular path bigger as it leaves Dee 2 the voltage will be flipped again making it further accelerates towards Dee1, this will continue until the radius of the circular path is big enough and the particle spirals outwards till it goes through the exist hole and hits the target placed in the bombardment chamber

Question 18

why can we use a constant frequency for cyclotron

Answer 18

in a cyclotron the frequency needs to change as soo as the charged particles leaves the Dee, so you’d assume with increasing radius the frequency would need to increase which is not true! that is because of the equation f = Bq/2pim meaning that since the frequency needed is depended of the radius. this means that a constant frequency can be used and a particle would complete each semi-circle through the Dee at the same time, that is until we reach the speed of light and mass starts changing

Question 19

how do we get f Bq/2pim

Answer 19

page 88

Question 20

what is the equation of the cyclotrons frequency when approaching the speed of light

Answer 20

f = Bq/2pim(0) x the square root of 1- v^2/c^2

Question 21

what is a synchrotron

Answer 21

a machine that accelerates charged particles aroud a fixed circular path