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A proposed electron–positron linear collider using normal-conducting RF structures powered through a separate drive-beam deceleration system. The 2012 conceptual design studied multi-TeV operation and lower-energy stages; its $3$ TeV design used approximately $100$ MV/m main-linac gradients. Historical design targets should be distinguished from later staging revisions and from operating measurements. ^[ref]

A proposed electron–positron linear collider based on superconducting RF acceleration. The 2007 reference design relevant to an exam-era comparison targeted $500$ GeV centre-of-mass energy and peak collider luminosity $2\times 10^{34}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$, with approximately $31$ km total footprint. These are historical design parameters, not achieved machine performance. ^[ref]

Both machines are proposed electron–positron linear colliders, using sources, damping rings, bunch compressors, two opposing main linacs, and final-focus and beam-delivery sections that bring very small bunches to an interaction point. The spent beams go to extraction lines and beam dumps rather than making repeated collision turns.

In the exam-era International Linear Collider reference design, polarized electrons and an undulator-based positron source feed damping rings and two superconducting main linacs; the full $500$ GeV centre-of-mass facility is about $31$ km long. The Compact Linear Collider adds high-current drive-beam generation and deceleration lines parallel to its main linacs; its $3$ TeV concept is roughly $48$ km long. The linear layout avoids the repeated synchrotron-radiation losses that would be severe for multi-hundred-GeV electrons in a storage ring. ^{[ref] [ref]}