Cyclotron and Linac

• For very high energy electrons, successive drift tubes have the same length, Why?

  • Electrons approach the speed of light there is no appreciable increase in speed
  • velocity is constant and electrons spend same time in drift tubes so S=vt must be constant
• Main equations for Cyclotron and Linacs

  F = Bqv

  F = mv^2/r

  V = 2πr/T
• Explain the use of electric fields in a Linac

  • Particles are accelerated by electric field in gaps
  • Frequency is constant so time spent in each drift tube is constant
  • This is from the increasing length of the tube
  • The polarity changes it is always accelerating particles
• Explain why a magnetic field is applied at right angles to the dees in cyclotron

  • Particles experience a force at right angles to their velocity
  • This causes centripetal force
• Explain how a cyclotron produces the high energy proton beam. (6)

  • There is an alternating p.d / E field
  • E field accelerates electron through the gap
  • Magnetic field is perpendicular to dees
  • So proton path is curved by magnetic field
  • As velocity increases radius of path in dees increase as well
  • time spent by proton in dees is constant
• Explain why distances between drift tubes increase in first section of linac but are almost equally spaced in the last section of linac? (6)

  • Electrons accelerate in the gaps
  • Frequency of a.c supply is constant
  • Time taken for an electron between tubes is constant
  • Electrosn travel further in a fixed time with a higher speed s = vt
  • In the last section of linac, the electron approaches the speed of light
  • Speed nearly becomes constant so distance travelled nearly becomes constant
• Which type of collision is more likely to produce new particles with largest mass

  Fixed target - momentum of two beams is zero before collision

  Colliding beams - there will be more kinetic energy available

  • All of the kinetic energy of the two beams available can be converted to mass so colliding beams is more likely to produce a particle with larger mass