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1 year ago in Particle Physics , Physics By Jayalakshmi

Is beam spreading in relativistic particle beams diffusion or diffraction?

We're optimizing beamlines for a collider experiment. At non-relativistic energies, scattering dominates. However, at our ultra-relativistic energies, the de Broglie wavelength is significant. This makes us wonder if quantum wave effects become non-negligible in the beam's ensemble behavior, or if classical stochastic processes still govern the macroscopic spreading we observe.

 

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By Mukesh Answered 4 months ago

Having designed beamlines for synchrotrons, I would recommend this rule of thumb: for most practical purposes with real beams containing many particles, the spreading is dominated by diffusion-like processes, primarily multiple Coulomb scattering in residual gas or intra-beam scattering. While the single-particle wavefunction diffracts, the collective emittance growth we measure is a statistical, stochastic effect. I have seen diffraction become a limiting factor only in exceptionally cold, dilute beams where the coherence length becomes significant, which is a rare experimental regime.

 

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