Bunched electrons: How many and how fast?

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Discussion Overview

The discussion revolves around the topic of bunched electrons in particle accelerators, specifically focusing on the number of electrons that can be bunched, their acceleration speeds, and the implications of these factors on particle physics. Participants explore concepts related to charge measurement, relativistic speeds, and energy calculations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Jake inquires about the maximum number of electrons that can be bunched and whether this affects their acceleration levels.
  • Zz mentions a record for charge per bunch at their facility, stating it is 110 nC, and notes that this is considered a large amount for electron accelerators.
  • Jake questions the meaning of "nC" and calculates the number of electrons corresponding to 110 nC, suggesting it to be approximately 7x10^11 electrons based on the charge of an electron.
  • Jake expresses uncertainty about the relationship between MeV and relativistic speeds, asking for clarification on what constitutes "relativistic speed."
  • Zz responds that anything above 1 MeV is considered relativistic and explains that calculations for electron dynamics can assume speeds approaching the speed of light at this energy level.
  • Jake seeks confirmation on whether the energy of the bunched electrons is measured in an energy resolving chamber within a particle accelerator.

Areas of Agreement / Disagreement

Participants do not reach a consensus on several points, including the specifics of how many electrons can be bunched and the implications of relativistic speeds on energy calculations. Multiple viewpoints and questions remain unresolved.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about relativistic effects and the dependence on definitions of charge and energy. The relationship between energy and the number of electrons in a bunch is not fully clarified.

Who May Find This Useful

Individuals interested in particle physics, accelerator technology, and the behavior of electrons in high-energy environments may find this discussion relevant.

jaketodd
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I am wondering how many electrons have been successfully bunched and how fast they have been accelerated to in a particle accelerator. Is there an upper limit on how many electrons can be bunched? Does the possible acceleration level of that bunch depend on the number of electrons in that bunch?

Thanks,

Jake
 
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The facility that I work at holds the "world's record" (meaning, it isn't in the Guinness Books, but we haven't found anyone beating it in the literature) for the largest amount of charge per bunch, which is 110 nC. These were accelerated at 18 MeV, which is low, and which is why we're constructing a new one.

To put this into perspective, for most electron accelerator facilities, 1nC is large. For us, we sneeze and we get 1 nC.

Zz.
 
Thank you. I have a couple questions. What is "nC"? I used Wikipedia and my best guess is Nanocoulomb. So, how many electrons does it take to get 110 nC? From Wikipedia, the charge of an electron is about −1.6x10^−19 C and 1 nC is 1x10^-9 C. Are my calculations correct that about 7x10^11 electrons were used? But MeV is a relativistic speed, right (I can't find an eV to speed converter. Do you know of one? I can't get the energy amplification using Einstein's equations without the speed)? Also, what counts as "relativistic speed" (what's the cutoff range of speeds or speed?)? So, my calculations must be wrong because the 110 nC must have been amplified to that level from a smaller nC due to the relativistic energy amplification. Can you tell me how many electrons are in the bunch at 18 MeV and 110 nC?

Thanks,

Jake
 
Also, is the energy of the bunch as a whole measured when bunched electrons are run through an energy resolving chamber in a particle accelerator?
 
Check out my blog, or the thread "perfect symmetry"
jal
 
ZapperZ?
 
jaketodd said:
Thank you. I have a couple questions. What is "nC"? I used Wikipedia and my best guess is Nanocoulomb. So, how many electrons does it take to get 110 nC? From Wikipedia, the charge of an electron is about −1.6x10^−19 C and 1 nC is 1x10^-9 C. Are my calculations correct that about 7x10^11 electrons were used? But MeV is a relativistic speed, right (I can't find an eV to speed converter. Do you know of one? I can't get the energy amplification using Einstein's equations without the speed)? Also, what counts as "relativistic speed" (what's the cutoff range of speeds or speed?)? So, my calculations must be wrong because the 110 nC must have been amplified to that level from a smaller nC due to the relativistic energy amplification. Can you tell me how many electrons are in the bunch at 18 MeV and 110 nC?

Thanks,

Jake

nC = nanocoulomb. It is the amount of charge. To get the number of electrons, you simply divide this by the charge of an electron.

For an electron, anything above 1 MeV is considered as relativistic. A a general rule of thumb, if the KE is larger than the rest energy, then you should consider it relativistic. At more than 1 MeV, most calculation of electron dynamics can be solved with a good degree of accuracy by assuming that the electron speed is c.

You can't find how many electrons with the energy value. You need the charge value.

Zz.
 
Thanks!
 

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