Particle accelerators and detectorsEdexcel A-Level Physics: Mind map

Exam questions on Particle accelerators and detectors

1. In a particle accelerator, electrons are produced by a heated metal filament (the cathode) in an evacuated tube. They are then accelerated towards an anode through a p.d. of 2.0 kV. The charge on an electron is 1.60 × 10⁻¹⁹ C.
   Explain why the accelerator tube must be evacuated.2 marks
2. A cyclotron consists of two hollow D-shaped electrodes (dees) in an evacuated chamber, placed in a uniform magnetic field of flux density 1.2 T perpendicular to the plane of the dees. An alternating p.d. is applied between the dees, and protons are injected near the centre. The charge on a proton is 1.60 × 10⁻¹⁹ C and its mass is 1.67 × 10⁻²⁷ kg.
   A proton is moving at 5.0 × 10⁶ m s⁻¹ inside one of the dees. Calculate the radius of its circular path.2 marks
3. A linear accelerator (linac) consists of a line of hollow cylindrical drift tubes in an evacuated chamber, connected alternately to the two terminals of an alternating supply of frequency 25 MHz. A beam of protons travels along the axis of the tubes.
   Explain why the protons travel at constant speed inside each tube, where they are accelerated, and why the polarity of the supply must alternate.3 marks