Particle Accelerators Electric Magnetic Fields Cf E Higher
- Slides: 15
Particle Accelerators: Electric & Magnetic Fields Cf. E Higher Physics
Particle accelerators • As the name suggests, a particle accelerator moves charged particles from rest to very high velocities. • This is to allow high energy collisions to take place in order to study the fundamental particles that are produced, or to produce high energy X Rays and gamma rays in medical equipment • Particle accelerators either use electric fields or magnetic fields to produce the forces required to accelerate the particles. • Protons (Hadrons) or positive nuclei (large ions) or electrons can be accelerated (Neutrons can’t be used as they are unaffected by electric and magnetic fields)
3 types of particle accelerator: 1. Linear accelerator: This type accelerates particles using electric fields in a straight line towards a target at the end of a long tunnel…. .
2. Cyclotron These use electric fields to accelerate the particles and magnetic fields to steer the particles in a circular path. A medical cyclotron smashes electrons into targets to produce X-Rays and gamma rays for medical purposes.
3. Synchrotron (CERN) A synchrotron can synchronise (sync) multiple beams of particles using electric and magnetic fields. Beams moving in opposite directions can be focused and collide with each other to produce the most fundamental particles in the universe.
What is a field? • In physics a field is a region where a particle experiences a force. • An electric field is a region in which an electric charge experiences a force • A magnetic field is a region in which a moving electric charge experiences a force • (also remember: a gravitational field is a region in which a mass experiences a force) Watch as the electrons in the atoms of the seeds are affected by a large electric field - watch
Electric fields • An electric field is a region in which an electric charge experiences a force Electric fields lines show the direction of the force on a positive charge in the field • A positive charge is accelerated towards the negative terminal • Note: If a charge enters the field at right angles to the field it will experience a force that causes it to move in a projectile path
Work done on a mass in an gravitational field • Similar to a mass moving in a gravitational field: • If a mass (m) is released from a certain height (h) then gravity produces an unbalanced force on the mass (mg) and causes it to accelerate downwards. • Work is done by the field and the gravitational potential energy of the mass is changed into kinetic energy But…. . the force acting on the mass is its weight! F = (mg) The distance it falls is the height (h) (So the Work done = change in potential energy) Gravitational Potential energy Kinetic energy
Work done on a charge in an electric field • When electrons are linearly accelerated in an electric field the energy change is: Electrical energy Kinetic energy W = work done by the field (J) Q = charge in coulombs (C) V = voltage across the field (V) (This is equivalent to the change in the electrical potential energy of the charge!) E = energy gained by the charge (J) m = mass of the charge (kg) v = velocity of the charge(ms-1)
Example: Charge moving in an electric field. An electron is accelerated in an electric field from a cathode to an anode in an electron gun by a potential difference (voltage) of 5000 V. Determine: a) The work done on the electron by the field. (3) b) The kinetic energy of the electron after it passes through the anode. (1) c) The speed of the electron when it exits the anode. (2) Data required: Charge on the electron: q = 1. 6 x 10 -19 C Mass of the electron: m = 9. 11 x 10 -31 kg
Studying fields – The cathode ray tube • We can study fields in the classroom using this apparatus: • Electrons are fired from a negative “cathode” towards a positive “anode” in an “electron gun” • This beam of electrons can then be steered in a circular path with a magnetic field produced using electromagnets.
Magnetic fields • A magnetic field is a region in which a moving charge experiences a force. Since electrons are moving charges they will experience a force when they enter a magnetic field. If a charged particle enters a magnetic field perpendicular to the field, it will experience a force at right angles to its motion and it will be steered into a circular path.
Magnetic field direction? • To represent magnetic fields going into or coming out of the page the following system is used: Magnetic field going into the page: A grid of crosses showing the field region Magnetic field coming out of the page: A grid of dots showing the field region
The right hand rule – (for negative charge) The direction of the magnetic force on a negatively charged particle can be determined if you know the direction of the magnetic field (north to south) and the direction of the motion of a negative charge First finger = magnetic Field se. Cond finger = direction of moving Charge Thumb = direction of the force on the charge
Example: • Use the right hand rule to check which of these 2 diagrams is/are correct Both are correct!!
- The long-term future of particle accelerators
- Electric currents and magnetic fields
- Visualizing magnetic field
- Red fields
- Accelerators computer architecture
- Cosmic super accelerators
- Slidetodoc
- Analytics query accelerators
- Good to great technology accelerators
- Good to great chapter 6
- Scrap heap magnet circuit diagram
- Magnetic field in matter
- Magnetic fields quick
- Learning: module 26: magnetic forces and fields
- Electric fields
- Electric fields quiz