physics

Particle beam

Particle beam is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Particle beam rather than just read about it. In short: A particle beam is a stream of charged or neutral particles other than photons. In particle accelerators, these particles can move with a velocity close to the speed of light.

Key takeaways

Particle beam belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Particle beam to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Particle beam from memory before moving on to harder problems.

Reference excerpt

A particle beam is a stream of charged or neutral particles other than photons. In particle accelerators, these particles can move with a velocity close to the speed of light. There is a difference between the creation and control of charged particle beams and neutral particle beams, as only the first type can be manipulated to a sufficient extent by devices based on electromagnetism. The manipulation and diagnostics of charged particle beams at high kinetic energies using particle accelerators are main topics of accelerator physics.

Sources Charged particles such as electrons, positrons, and protons may be separated from their common surroundings. This can be accomplished by processes such as thermionic emission or arc discharge. The following devices are commonly used as sources for particle beams:

Ion source Cathode-ray tube, or more specifically in one of its parts called electron gun. This is also part of traditional television and computer screens. Photocathodes may also be built in as a part of an electron gun, using the photoelectric effect to separate particles from their substrate. Neutron beams may be created by energetic proton beams which impact on a target, e.g. of beryllium material. (see article Particle therapy)

Manipulation

Acceleration

Charged beams may be further accelerated by use of high resonant, sometimes also superconducting, microwave cavities. These devices accelerate particles by interaction with an electromagnetic field. Since the wavelength of hollow macroscopic, conducting devices is in the radio frequency (RF) band, the design of such cavities and other RF devices is also a part of accelerator physics. More recently, plasma acceleration has emerged as a possibility to accelerate particles in a plasma medium, using the electromagnetic energy of pulsed high-power laser systems or the kinetic energy of other charged particles. This technique is under active development, but cannot provide reliable beams of sufficient quality at present.

Guidance In all cases, the beam is steered with dipole magnets and focused with quadrupole magnets. With the end goal of reaching the desired position and beam spot size in the experiment.

Applications

High-energy physics

High-energy particle beams are used for particle physics experiments in large facilities; the most common examples being the Large Hadron Collider and the Tevatron.

Synchrotron radiation

Electron beams are employed in synchrotron light sources to produce X-ray radiation with a continuous spectrum over a wide frequency band which is called synchrotron radiation. This X-ray radiation is used at beamlines of the synchrotron light sources for a variety of spectroscopies (XAS, XANES, EXAFS, μ-XRF, μ-XRD) in order to probe and to characterize the structure and the chemical speciation of solids and biological materials.

Particle therapy

Energetic particle beams consisting of protons, neutrons, or positive ions (also called particle microbeams) may also be used for cancer treatment in particle therapy. Linear accelerators use electron beam at near speed of light to treat deep cancers in patients. A tungsten/molybdenum target can be moved into the beam to create x-rays to treat surface cancers.

Astrophysics and space physics Many phenomena in astrophysics are attributed to particle beams of various kinds. Solar Type III radio bursts, the most common impulsive radio signatures from the Sun, are used by scientists as a tool to better understand solar accelerated electron beams. Additionally, particle beams cause instabilities when interacting with plasma, which may lead to conditions causing electrostatic solitary waves.

Military The U.S. Advanced Research Projects Agency started work on particle beam weapons in 1958. The general idea of such weaponry is to hit a target object with a stream of accelerated particles with high kinetic energy, which is then transferred to the atoms, or molecules, of the target. The power needed to project a high-powered beam of this kind surpasses the production capabilities of any standard battlefield powerplant, thus such weapons are not anticipated to be produced in the foreseeable future.

See also Electron beam Ion beam Astrophysical jet Atomic beam Accelerator neutrino

References

Worked examples

Example 1 — a first encounter with Particle beam

Start with the simplest possible case. Write down what Particle beam claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Particle beam before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Particle beam ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Particle beam

In research: Particle beam appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Particle beam in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Particle beam is common in secondary-school and first-year university syllabi. It links to neighbouring topics Accelerator physics, so understanding it makes those chapters shorter.
In everyday life: Look for Particle beam outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Particle beam in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Particle beam means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Particle beam out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Particle beam in simple terms?

A particle beam is a stream of charged or neutral particles other than photons. In particle accelerators, these particles can move with a velocity close to the speed of light.

Why does Particle beam matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Particle beam?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Particle beam.