What is meant by the term beam spill ?

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Discussion Overview

The discussion centers around the term "beam spill" in the context of particle accelerators, exploring its definition, implications, and measurement. Participants examine its relevance in both fixed target and collider modes of operation, as well as its impact on accelerator performance.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that beam spill occurs when accelerated particles hit the walls of the accelerator pipe, which can be detrimental to the accelerator's operation.
  • Others propose that beam spill refers specifically to the time period during which particles are expelled from the accelerator ring into a linear beamline for experiments.
  • There is a mention of beam spill being measured in units of time, with a reference to beam loss rates in the LHC, indicating a relationship between beam spill and particle quantity.
  • A participant cites a definition of beam spill as the removal of a controllable quantity of particle beam current at a controllable rate onto an adjacent target.
  • Another participant references a specific example of beam spill duration from the OPERA experiment, noting it as 10.5 microseconds.

Areas of Agreement / Disagreement

Participants express differing views on the definition and implications of beam spill, with no consensus reached on a singular understanding of the term.

Contextual Notes

There are unresolved aspects regarding the relationship between beam spill and particle loss, as well as the specific conditions under which beam spill is measured or defined.

Doofy
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what is meant by the term "beam spill"?

in the context of a beam of particles from an accelerator?
 
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Some accelerated particles can hit the walls of the pipe (-> beam spill). If too many particles do that, it is bad for the accelerator.
 


mfb said:
Some accelerated particles can hit the walls of the pipe (-> beam spill). If too many particles do that, it is bad for the accelerator.

hmm are you sure? I'm seeing it being quoted in units of time.
 


Consider a synchrotron which is being used in "fixed target" mode, not in "collider" mode. You have a circular accelerating ring that gets the particles up to the desired energy. Extending tangentially from the ring is a linear beamline which then branches off to form various subsidiary beamlines for different experiments.

This setup doesn't produce a continuous beam. You inject (usually) protons at low energy into the ring, the ring accelerates them to the desired energy (which takes a few seconds as the magnetic field ramps up to keep the beam contained in the beampipe), and finally a deflecting magnet turns on and "spllls" the contents of the ring into the linear beamline(s). Then you inject a fresh batch of protons into the ring and the cycle repeats.

IIRC "beam spill" refers to the time period during which the accelerated particles are actually being "spilled" out of the ring.
 


Doofy said:
hmm are you sure? I'm seeing it being quoted in units of time.
As this is proportional to the number of particles, I would expect this unit. Beam loss in the LHC is usually reported like this - a beam lifetime of 100h means ~1% loss per hour.
 
As jtbell says, beam spill is defined as "the removal of a controllable quantity of the particle beam current at a controllable rate onto an adjacent target." See http://www.google.com/patents?id=52xYAAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false for the detailed description of a beam spiller.

the Wikipedia article on the OPERA experiment mentions that the proton beam spill used to generate the neutrinos is 10.5 microseconds.
 

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