13.3 Artificial transmutation and particle accelerators

Artificial transmutation and particle accelerators are game-changers in nuclear physics. They let us turn elements into others, make new ones, and study the building blocks of matter. It's like alchemy, but with science!

These tools help us fight cancer, make clean energy, and unlock the secrets of the universe. From medical imaging to creating superheavy elements, they're pushing the boundaries of what we can do with atoms.

Artificial Transmutation

Process and Historical Context

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• Artificial transmutation changes one element into another through nuclear reactions induced by particle bombardment
• Ernest Rutherford achieved the first artificial transmutation in 1919
  • Transformed nitrogen into oxygen by bombarding nitrogen atoms with alpha particles
• Process overcomes the Coulomb barrier between nuclei to initiate nuclear reactions
• Requires high-energy particles to overcome electrostatic repulsion between positively charged nuclei

Applications in Nuclear Physics and Medicine

• Produces radioisotopes for medical diagnostics and treatments
  • Technetium-99m used for medical imaging (bone scans, cardiac stress tests)
  • Iodine-131 utilized in thyroid cancer treatment
• Creates new elements, particularly superheavy elements not found in nature
  • Expands understanding of nuclear physics and the periodic table
  • Examples include nihonium (element 113) and oganesson (element 118)
• Plays crucial role in nuclear energy production
  • Creates fissile materials (plutonium-239 from uranium-238)
  • Manages nuclear waste through transmutation of long-lived radioactive isotopes
• Essential for studying nuclear structure and fundamental particle interactions
  • Provides insights into decay processes (alpha decay, beta decay)
  • Contributes to understanding of universe's composition (nucleosynthesis in stars)

Particle Accelerators in Transmutation

Fundamental Principles

• Use electromagnetic fields to propel charged particles to high speeds and energies
• Acceleration based on Lorentz force
  • Describes force experienced by charged particles in electromagnetic fields
  • $\mathbf{F} = q(\mathbf{E} + \mathbf{v} \times \mathbf{B})$
    • F = force, q = charge, E = electric field, v = velocity, B = magnetic field
• Utilize electric fields to increase particle energy
• Employ magnetic fields to control beam direction and focus

Key Components and Techniques

• Radio-frequency (RF) cavities synchronize accelerating electric fields with particle motion
  • Enables continuous acceleration of particles
• Vacuum systems minimize particle collisions with air molecules
  • Increases mean free path of accelerated particles
• Beam focusing elements (quadrupole magnets) maintain narrow particle beam
• Cooling systems manage heat generated by acceleration process
  • Examples include liquid helium for superconducting magnets

Role in Artificial Transmutation

• Provide high-energy particles necessary to initiate nuclear reactions
• Allow transformation of target nuclei into different elements or isotopes
• Energy and type of accelerated particles determine transmutation reactions
  • Influences products and efficiency of the process
• Enable precise control over particle energy and beam intensity
  • Allows systematic studies of nuclear reactions across wide range of elements

Types of Particle Accelerators

Linear and Circular Accelerators

• Linear accelerators (linacs) use straight-line arrangement of accelerating structures
  • Suitable for applications requiring pulsed beams or initial acceleration stages
  • Examples include SLAC at Stanford University, LINAC4 at CERN
• Cyclotrons utilize spiral path and constant magnetic field
  • Commonly used for producing medical isotopes and in radiation therapy
  • Examples include cyclotrons at TRIUMF in Canada, PSI in Switzerland
• Synchrotrons employ circular ring with varying magnetic fields
  • Maintain constant orbit radius as particles accelerate
  • Ideal for high-energy physics experiments and advanced light sources
  • Examples include Large Hadron Collider at CERN, Advanced Photon Source at Argonne National Laboratory

Specialized Accelerators

• Tandem Van de Graaff accelerators use electrostatic fields to accelerate particles twice
  • Particularly useful for accelerating heavy ions in nuclear physics research
  • Examples include ATLAS at Argonne National Laboratory
• Fixed-field alternating gradient (FFAG) accelerators combine features of cyclotrons and synchrotrons
  • Offer rapid acceleration cycles for applications like proton therapy
  • Examples include EMMA at Daresbury Laboratory, UK
• Storage rings maintain high-energy particle beams for extended periods
  • Crucial for collider experiments in particle physics
  • Examples include Tevatron at Fermilab (decommissioned), RHIC at Brookhaven National Laboratory
• Spallation neutron sources use high-energy proton accelerators to produce neutrons
  • Essential for materials science and neutron scattering experiments
  • Examples include SNS at Oak Ridge National Laboratory, ISIS at Rutherford Appleton Laboratory

Products of Artificial Transmutation

Types of Transmutation Products

• Wide range of isotopes produced
  • Stable isotopes (carbon-13, oxygen-18)
  • Short-lived radioisotopes (fluorine-18, half-life ~110 minutes)
  • Long-lived radioactive species (plutonium-239, half-life ~24,100 years)
• Yield and purity depend on various factors
  • Target material composition
  • Projectile type and energy
  • Reaction cross-sections
• Neutron-induced transmutations often produce heavier isotopes
  • Example: neutron capture by uranium-238 to form plutonium-239
• Charged particle-induced reactions can form proton-rich isotopes
  • Example: production of fluorine-18 from oxygen-18 via proton bombardment

Applications and Implications

• Creation of superheavy elements through fusion reactions
  • Provides insights into nuclear stability at limits of periodic table
  • Tests theoretical models of nuclear structure
  • Example: synthesis of element 117 (tennessine) from calcium-48 and berkelium-249
• Transmutation of long-lived nuclear waste
  • Potential solution for nuclear waste management
  • Faces significant technical challenges for practical implementation
  • Example: conversion of long-lived actinides to shorter-lived fission products
• Production of specific radioisotopes enables advances in nuclear medicine
  • Targeted radiotherapies (lutetium-177 for neuroendocrine tumors)
  • High-resolution imaging techniques (gallium-68 for PET scans)
• Analysis of transmutation products provides valuable nuclear data
  • Insights into nuclear binding energies
  • Information on decay modes and nuclear structure
  • Contributes to refinements in nuclear models and theories
  • Example: study of superheavy element decay chains to understand nuclear shell structure