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physics

LHeC

LHeC 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 LHeC rather than just read about it. In short: The Large Hadron Electron Collider (LHeC) is a conceptual particle accelerator facility that has been studied for a possible upgrade of the existing Large Hadron Collider storage ring operating at CERN in Geneva, Switzerland. By adding a new electron accelerator adjacent to the existing LHC proton accelerator and storage ring, the LHeC would enable the investigation of electron-proton and electron-ion collisions at…

LHeC — main illustration
LHeC — illustration

Key takeaways

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

Reference excerpt

The Large Hadron Electron Collider (LHeC) is a conceptual particle accelerator facility that has been studied for a possible upgrade of the existing Large Hadron Collider storage ring operating at CERN in Geneva, Switzerland. By adding a new electron accelerator adjacent to the existing LHC proton accelerator and storage ring, the LHeC would enable the investigation of electron-proton and electron-ion collisions at much higher energies and rates than had been possible at the electron-proton collider HERA at DESY in Hamburg, Germany, which terminated its operation in 2007. These capabilities of the LHeC could provide a unique program of particle physics research, studying the substructure of the proton and nuclei, or the physics of the Higgs boson.

Design Concept The baseline design of the LHeC consists in two superconducting linear particle accelerators ("linacs") each about 1 km long, arranged in a racetrack configuration tangential to the LHC. Each linac provides about 10 GeV acceleration, therefore the electrons makes three turns in the racetrack reaching an energy of about 60 GeV before colliding with the 7 TeV protons or 2.7 TeV lead ions. A unique feature of the design is the optimization for a particularly low power consumption, which would be achieved by decelerating the electron beam after the collision and gaining back nearly all its energy into the radio-frequency cavities of the linacs, a principle termed "energy recovery". Currently, preparations of an international collaboration with CERN are ongoing for developing superconducting accelerator cavities, at the appropriate frequency of 802 MHz. In parallel a design study for an energy recovery linac test platform is being pursued at CERN. Related to the proton and heavy-ion physics of the LHC, the physics program and a detector for the LHeC are also under study. For maximum use of the operation time and resources of the LHC complex at CERN it is envisaged that electron-proton and proton-proton data are taken simultaneously. The LHeC electron beam may be combined with a multi-10-TeV proton beam in the far future, which has been under consideration in a worldwide study at CERN since 2013. LHeC would be an electron–ion collider, similar to other systems planned at other particle physics laboratories, although the present design would not include polarized protons.

References "The Large Hadron-Electron Collider at the HL-LHC", 2020 update of the 2012 conceptual design report "Electrons at the LHC: a new beginning", CERN Courier, June 2014 "A Large Hadron Electron Collider at CERN: Report on the Physics and Design Concepts for Machine and Detector", Journal of Physics G: Nuclear and Particle Physics, 2012 "Electrons for the LHC", CERN Courier, April 2012

Illustrations

LHeC: Current default layout of the LHeC recirculating linear electron accelerator complex. Collisions with the proton beam happen at the interaction point (IP).
Current default layout of the LHeC recirculating linear electron accelerator complex. Collisions with the proton beam happen at the interaction point (IP).

Worked examples

Example 1 — a first encounter with LHeC

Start with the simplest possible case. Write down what LHeC 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 LHeC 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 LHeC 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 LHeC

In research
LHeC 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 LHeC 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
LHeC is common in secondary-school and first-year university syllabi. It links to neighbouring topics CERN particle accelerator studies, Particle physics facilities, Proposed particle accelerators, so understanding it makes those chapters shorter.
In everyday life
Look for LHeC 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 LHeC in 20 minutes

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

Frequently asked questions

What is LHeC in simple terms?

The Large Hadron Electron Collider (LHeC) is a conceptual particle accelerator facility that has been studied for a possible upgrade of the existing Large Hadron Collider storage ring operating at CERN in Geneva, Switzerland. By adding a new electron accelerator adjacent to the existing LHC proton…

Why does LHeC 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 LHeC?

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 LHeC.

Tags

  • CERN particle accelerator studies
  • Particle physics facilities
  • Proposed particle accelerators

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