Particle Accelerators, Detectors and Cross-Sections · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Smashing particles to see the small

Science · Quantum & Modern Physics · ages 20-21
Name ______________________   Date ____________

  1. What path do particles take inside a cyclotron?

    • A widening spiral, kicked twice per lap
    • A straight line with one kick
    • A fixed circle with no kicks

  2. Why study quarks with a giant accelerator rather than a better microscope?

    • Microscopes cannot focus that small
    • Lenses that strong would melt
    • Resolution needs short wavelength, which needs high energy

  3. A track's bend direction in a magnetic field reveals the particle's charge sign.

    Circle one:   True   False

  4. A curved detector track is found. What does its curve reveal?

    • Only the particle's color
    • Momentum from bend size, charge sign from bend direction
    • Only the time of day

  5. An 800 MeV linac has 2000 gaps. Type the average energy gain per gap in MV.

    Answer: ______________

  6. How is a passing particle identified?

    • By its smell in the tunnel
    • By guessing from the beam clock
    • Energy loss, flight time, and Cherenkov light combined

  7. The beam flux doubles with the same target and energy. What happens to the event rate?

    • It stays exactly level
    • Event rate doubles
    • The cross-section doubles

  8. A student says detectors film the collision moment. What is wrong?

    • They record outgoing tracks and quote rates as cross-sections
    • Detectors are always switched off
    • Collisions emit no products at all
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Smashing particles to see the small W1-mt_euJtxtxXyV-s1

  1. A widening spiral, kicked twice per lap · Magnets bend each lap into a wider spiral while gaps kick twice per orbit.
  2. Resolution needs short wavelength, which needs high energy · Only short-wavelength, high-energy probes resolve such fine structure.
  3. True · Opposite charges curve opposite ways in the same field.
  4. Momentum from bend size, charge sign from bend direction · Tighter bends mean lower momentum, and the bend way shows charge sign.
  5. 0.4 · Total MeV divided by gap count: 800 over 2000 is 0.4 MV per gap.
  6. Energy loss, flight time, and Cherenkov light combined · Three independent clues together name the particle.
  7. Event rate doubles · Rate equals flux times targets times cross-section, so it scales with flux.
  8. They record outgoing tracks and quote rates as cross-sections · Detectors count products after the crash and report likelihood as cross-section.
Worksheet · LightMySky