A level Physics · Edexcel 9PH0 · Topic 8B
Particle accelerators and detectors
Key points
- A linear accelerator (linac) uses alternating p.d.s across a series of drift tubes of increasing length, so charged particles gain energy at each gap.
- A cyclotron uses a perpendicular magnetic field to bend particles into a spiral and an alternating p.d. across the gap between two "dees". The radius grows as the particle speeds up: .
- The cyclotron frequency does not depend on speed (at non-relativistic speeds), so a fixed-frequency supply keeps in step.
- Detectors record tracks of charged particles in a magnetic field: the direction of curvature shows the sign of charge, and the radius gives the momentum.
- Neutral particles leave no tracks; their presence is inferred from conservation of momentum and from the tracks of their decay products.
- In collisions, kinetic energy can create new particles: . Head-on collisions make more energy available.
- Convert energies with 1 MeV = J.
Topic notesPremium
To study particles smaller than a nucleus, physicists give charged particles huge energies and collide them. Accelerators use electric fields to add energy and magnetic fields to steer, and detectors use magnetic fields to turn invisible…
Unlock the full notes with Premium
Premium includes full topic notes, the paper generator, self-quizzes and progress tracking.
Practise this topicPremium
Premium members can generate an exam-style paper with a mark scheme, or take a quick quiz, on Particle accelerators and detectors.