Medical Physics: Linear Accelerators
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Questions and Answers

What component is used to produce microwaves in the RF power generation system?

  • Klystron
  • Diode Gun
  • Pulsed Modulator
  • Magnetron (correct)

Which type of electron gun incorporates a grid?

  • Triode type (correct)
  • Diode type
  • Electron-type
  • Radiation type

What is the purpose of cavities in the accelerating waveguide?

  • To amplify microwaves
  • To store electrical energy
  • To couple and distribute microwave power (correct)
  • To increase electron speed

What pressure level is the accelerating waveguide evacuated to?

<p>10−6 tor (D)</p> Signup and view all the answers

Which of the following is a function of the pulsed modulator in the RF power generation system?

<p>Generating high voltage pulses (A)</p> Signup and view all the answers

How many cavities are suitable for acceleration at any given moment in the travelling wave accelerating structure?

<p>Only one in four (B)</p> Signup and view all the answers

Which type of waveguide is used specifically for RF power transmission?

<p>Radiofrequency power transmission waveguide (D)</p> Signup and view all the answers

What does the triode type electron gun share with the diode type?

<p>The heated filament cathode (B)</p> Signup and view all the answers

Why are waveguides evacuated in linear accelerators?

<p>To allow free propagation of electrons (D)</p> Signup and view all the answers

What is the purpose of the grid in a triode electron gun?

<p>To control electron flow (C)</p> Signup and view all the answers

What is the primary function of the electron gun in a linear accelerator?

<p>To serve as the source of electrons (C)</p> Signup and view all the answers

What distinguishes the triode type electron gun from the diode type?

<p>It includes a grid (D)</p> Signup and view all the answers

Which component in the RF power generation system amplifies microwaves?

<p>Klystron (B)</p> Signup and view all the answers

What is the major purpose of an accelerating waveguide in a linear accelerator?

<p>To accelerate electrons (C)</p> Signup and view all the answers

Which type of waveguide is used for transmitting RF power in a medical linac?

<p>Gas filled waveguide (D)</p> Signup and view all the answers

How does the structure of the accelerating waveguide differ from a uniform waveguide?

<p>It has a series of disks added with circular holes (C)</p> Signup and view all the answers

What is the role of the cavities in the accelerating waveguide?

<p>To couple and distribute microwave power (B)</p> Signup and view all the answers

What is the maximum atmospheric condition of the acceleration waveguide?

<p>Evacuated to about $10^{-6}$ tor (D)</p> Signup and view all the answers

In the travelling wave accelerating structure, how often are cavities suitable for acceleration?

<p>One in four cavities is suitable (C)</p> Signup and view all the answers

What component produces the high voltage pulses required by the RF power source?

<p>Pulsed modulator (A)</p> Signup and view all the answers

Study Notes

LINAC Basics

  • LINACS utilize an electron gun for electron injection, functioning as a basic electrostatic accelerator.
  • Two common electron gun types in medical LINACS: diode type and triode type.
  • Both gun types are equipped with a heated filament cathode and a perforated grounded anode; the triode variant includes an additional grid.

RF Power Generation

  • The radiofrequency (RF) power generation system supplies microwave energy essential for electron acceleration.
  • Key components of the RF power generation system include:
    • RF Power Source:
      • Magnetron: Generates microwaves.
      • Klystron: Amplifies microwave signals.
    • Pulsed Modulator: Delivers high voltage and short duration pulses needed for RF power source and electron gun.

Waveguides

  • Waveguides are either evacuated or gas-filled metallic structures, facilitating microwave transmission, shaped as rectangular or circular cross-sections.
  • Two types utilized in LINACS:
    • RF Power Transmission Waveguides: Usually gas-filled with SF6, directing RF power from the source to the accelerating waveguide.
    • Accelerating Waveguides: Evacuated to approximately 10−6 torr, specifically designed for electron acceleration.

Accelerating Waveguides

  • Accelerating waveguides comprise cylindrical uniform tubes with multiple disks featuring circular holes to create cavities at consistent intervals.
  • The primary functions of these cavities:
    • Distribute and couple microwave power.
    • Establish an electric field pattern essential for optimal electron acceleration.

Traveling Wave Structure

  • Microwaves enter the accelerating structure from the gun side, traveling towards the high-energy end.
  • At any moment, only one in four cavities is active for electron acceleration, optimizing the efficiency of the process.

LINAC Basics

  • LINACS utilize an electron gun for electron injection, functioning as a basic electrostatic accelerator.
  • Two common electron gun types in medical LINACS: diode type and triode type.
  • Both gun types are equipped with a heated filament cathode and a perforated grounded anode; the triode variant includes an additional grid.

RF Power Generation

  • The radiofrequency (RF) power generation system supplies microwave energy essential for electron acceleration.
  • Key components of the RF power generation system include:
    • RF Power Source:
      • Magnetron: Generates microwaves.
      • Klystron: Amplifies microwave signals.
    • Pulsed Modulator: Delivers high voltage and short duration pulses needed for RF power source and electron gun.

Waveguides

  • Waveguides are either evacuated or gas-filled metallic structures, facilitating microwave transmission, shaped as rectangular or circular cross-sections.
  • Two types utilized in LINACS:
    • RF Power Transmission Waveguides: Usually gas-filled with SF6, directing RF power from the source to the accelerating waveguide.
    • Accelerating Waveguides: Evacuated to approximately 10−6 torr, specifically designed for electron acceleration.

Accelerating Waveguides

  • Accelerating waveguides comprise cylindrical uniform tubes with multiple disks featuring circular holes to create cavities at consistent intervals.
  • The primary functions of these cavities:
    • Distribute and couple microwave power.
    • Establish an electric field pattern essential for optimal electron acceleration.

Traveling Wave Structure

  • Microwaves enter the accelerating structure from the gun side, traveling towards the high-energy end.
  • At any moment, only one in four cavities is active for electron acceleration, optimizing the efficiency of the process.

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Description

This quiz covers the fundamentals of linear accelerators, specifically focusing on the electron gun types used in medical linacs. It discusses the differences between diode and triode types and their components like cathodes and anodes. Ideal for students in M.Sc. Medical Physics seeking to understand linac technology.

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