What is the relationship between HUP and particle accelerators?

[rewebster]

I hope this question relates closely enough:

[Mentor note: Don't be afraid to start a new topic if your question isn't directly related to an existing one. Also, this is really a QM question so I'm moving this to the Quantum Physics forum while I'm at it.]

If the 'controls' of an accelerator sends out impulses to the accelerator sometimes up to a billion times a second, does the process even care where along the path the 'particle' is that is being accelerated (except for re-routing)?

With HUP, speed of the electrical signal involved to each plate/electromagnet, and the speed that the plate must 'charge', the interval between charges, AND knowing the location/'position' of the particle--it seems the process may tend toward a 'gross' process than a 'fine' process.


(PS--I'm not rfwebster)

thank you kind sir(Mentor, whomever you may be), for the:

1) the advice
2) the move
3) the understanding

 

[jtbell]

As far as I know, the design of particle accelerators does not involve QM (including the HUP) at all, that is, it's based on classical electrodynamics applied to beams of charged particles.

On the other hand, the experiments done with those accelerators do usually need to be analyzed using QM (more properly, quantum field theory), of course.

 

[rewebster]

I threw in HUP thinking that if something is moving at .8 or .9, can you know very much else about the particle until it 'does'/(someone measures) something else about it (like even where it is on a five mile course)?

 

[ZapperZ]

Charge particles in a particle accelerators are classical particles. All the software codes that do particle tracking such as PARMELA, etc. treat them as classical particles, and they work pretty well in accelerator design and beam physics.

Zz.

 

[rewebster]

OK--thanks--but, is it 'known' where the particle is at any given moment (except at the point of collision, and maybe at the point of re-direction) in the accelerator?

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http://pbpl.physics.ucla.edu/Computing/Code_Overview/


simplified explanations

 

[ZapperZ]

OK--thanks--but, is it 'known' where the particle is at any given moment (except at the point of collision, and maybe at the point of re-direction) in the accelerator?

The macroscopic position, yes.

We don't deal with position of a single particle in a particle accelerator. We deal with a glob of them. Since they are in bunches (the one I deal with is barely 0.5 cm in length), we know and can track where they are very well, since our LINAC has to be in just the right phase for the electron bunches to enter be accelerated. If we don't get that right, they'll come in at the wrong phase and it won't work.

Besides, as soon as electrons reach MeV energies, they all can be easily estimated to move at c anyway, and that's how many of the particle tracking codes treat them, and treat them successfully that way.

Zz.

 

[rewebster]

Ok--and 'the wrong phase' means..?? spin-position orientation? from the plate/electro-magnetic? not correct for the 'expected outcome' or...?

 

[ZapperZ]

Ok--and 'the wrong phase' means..?? spin-position orientation? from the plate/electro-magnetic? not correct for the 'expected outcome' or...?

Er.. no. In an accelerating structure, an oscillating EM wave is "piped" into the structure, so you have an E-field along the axis that is oscillating. If a charge particle enters the structure at the wrong phase, i.e. the E-field is pointing in the wrong direction, or it is in the right direction but it is decaying, then the particle would not have the right force or the right timing to get accelerated.

So it is the phase of the RF field in the accelerating structure.

Zz.

 

[rewebster]

So, if the accelerator (if I read your answer correctly) is about .5 cm, how many times can it/does it occilate in one 'run'?--and it still gets close to LS?

---In my initial question about if an 'exact' position 'could' be known along the course, I was thinking more of a Fermi accelerator (miles).

 

[ZapperZ]

So, if the accelerator (if I read your answer correctly) is about .5 cm, how many times can it/does it occilate in one 'run'?--and it still gets close to LS?

No, the electron BUNCH length is about 0.5 cm.

Actually, I made a typo, it should be 0.5 millimeter, not centimeter.

Zz.

 

[lightarrow]

So, if the accelerator (if I read your answer correctly) is about .5 cm,

Wow! Nano accelerators! Where can I buy one of them to play with in my freetime?

 

[Anonym]

No, the electron BUNCH length is about 0.5 cm.

Actually, it should be 0.5 millimeter, not centimeter.

Sorry for my ignorance. How BUNCH length is related to the (longitudinal/transversal) coherence length?

The reference on the coherent review of the topic will be highly appreciated.

Regards, Dany.

 

[rewebster]

I'm not an 'accelerated' person, but my guess it has something to do with the '+' and '-' of the wavelength, and the frequency and/or amplitude of the wavelength as the 'bunch' 'rides' the pulse between sin crests either directly or on a harmonic level.---and the 'bunch' fits in between the 'wave crests'. (?)


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surf's up, dude

 

[ZapperZ]

Er.. I don't think it is. There's no "coherence length" in the classical particles within a particle accelerator, at least not in the QM sense. There certainly is no analogue of the coherence length in superconductivity to the particles in an accelerator.

Again, beam physics mainly deal with classical particles. Even the coulombic particle-particle interactions are dealt with classically, rather than what is dealt with in condensed matter.

Zz.

 

[rewebster]

So, in the '50 words or less' category--how's my description?

 

[ZapperZ]

So, in the '50 words or less' category--how's my description?

Your description sucks! :rofl:

Hey, you wanted 50 words or less! :)

If you want MORE than 50 words, here it is:

The bunch length in most particle accelerators that use a photoinjector source depends very much on the pulsed laser duration and the RF phase of the photoinjector. The photocathode sits in a cavity that has an oscillating E-field from the RF source. A pulsed laser hits the cathode. If it hits it at the right phase, then the generated photoelectrons can be accelerated and leave the photoinjector cavity to enter the rest of the accelerator line.

Obviously, there's a range of phase in which the E-field has the right "sign" to do this. However, even if the sign is correct, if the laser hits the photocathodes at different phase within this correct sign, will will change the longitudinal bunch length of the charges that exit the photoinjector. The bunch length is different at 30 degrees when compared to 60 degrees, etc.

So it isn't as simple as the "+" and "-" phase of the RF wave.

Zz.

 

[rewebster]

Thanks--that helps QUITE a bit---



but (in the 50 words or less category) --your MS WORD count is 141----

so, one point subtracted for each 'extra' word (out of a possible 100 points) --you get a score of '9'

 

[Anonym]

Since they are in bunches, we know and can track where they are very well, since our LINAC has to be in just the right phase for the electron bunches to enter be accelerated.

Er.. I don't think it is. There's no "coherence length" in the classical particles within a particle accelerator, at least not in the QM sense…beam physics mainly deal with classical particles.

My question is related to A. Tonomura et al. (1989) set-up which in the source section looks similar. The number you presented is pretty close.

How do you know the difference between the classical electrons bunches and the coherent wave packet? How you define number of the electrons in the bunch?

Regards, Dany.

 

[ZapperZ]

My question is related to A. Tonomura et al. (1989) set-up which in the source section looks similar. The number you presented is pretty close.

Again, I can easily double the bunch length that I'm using by (i) increasing the laser pulse length and (ii) changing the phase that I shoot the laser at with respect to the RF in the photo injector. There's nothing "intrinsic" about this.

How do you know the difference between the classical electrons bunches and the coherent wave packet? How you define number of the electrons in the bunch?

Regards, Dany.

1. The classical particle tracking code works.

2. I measure the charge of the bunch using an ICT (integrated charge transformer), then divide by e. In fact, that is how I determine the quantum efficiency of the photocathode.

Zz.

 

[Anonym]

I measure the charge of the bunch using an ICT (integrated charge transformer), then divide by e. In fact, that is how I determine the quantum efficiency of the photocathode.

What you get usually (average)?

The classical particle tracking code works.

That is always good reason, but perhaps not sufficiently good (depend on your answer to the first question).

Regards, Dany.

 

[ZapperZ]

What you get usually (average)?

Our beamline requires high-charge bunches, so we go from 1 nC to 120 nC. The latter is the world's record for a single bunch in L-band photoinjector. For many facilities, 1 nC is "large". We "sneeze" and we get 1 nC.

That is always good reason, but perhaps not sufficiently good (depend on your answer to the first question).

No, it IS good, because we DESIGN anything we want to build based on those codes. If they don't work, we're screwed and out of several millions of dollars. Most of the beamlines and synchrotron centers have to be designed first, and the beam dynamics have to be simulated so that the correct engineering specifications are built. These simulations predominantly tread the particle dynamics classically.

And we're not the only one either. Look in plasma physics. Most of the treatment there are classical in terms of the evolution and the dynamics of the plasma.

Zz.

 

[Anonym]

I measure the charge of the bunch using an ICT (integrated charge transformer), then divide by e…. Our beamline requires high-charge bunches, so we go from 1 nC to 120 nC. The latter is the world's record for a single bunch in L-band photoinjector. For many facilities, 1 nC is "large". We "sneeze" and we get 1 nC.

You force me to work. You promised the dimensionless number.

No, it IS good, because we DESIGN anything we want to build based on those codes. If they don't work, we're screwed and out of several millions of dollars. Most of the beamlines and synchrotron centers have to be designed first, and the beam dynamics have to be simulated so that the correct engineering specifications are built. These simulations predominantly tread the particle dynamics classically.

No doubt. Russians assert that Vecksler was the first. If so, not correct engineering specifications means bullet. Nevertheless, it is possible that some interesting side effect was overlooked.

Regards, Dany.

 

[ZapperZ]

You force me to work. You promised the dimensionless number.

Where did I actually say that? Besides, what's not dimensionless about it? I have charge in nC, and I divide by "e", which has units of coulombs... <scratching head>

No doubt. Russians assert that Vecksler was the first. If so, not correct engineering specifications means bullet. Nevertheless, it is possible that some interesting side effect was overlooked.

Huh? Why do you even need to make that kind of speculation? What exactly are you trying to prove here?

All you need to do is look at how the field of study handles the beam dynamics. In fact the http://pac07.org/" is going on this very week. You're welcome to look at all the abstract of all the presented work and check for yourself how many of those actually did not use classical dynamics. Don't trust what I just said. Go check yourself before you make that kind of statement. Talk is cheap, but when you have a multi-million dollars worth of system to build, such wishy-washy speculation doesn't cut it.

Zz.

 

[Anonym]

Thank You.

 

[Anonym]

Our beamline requires high-charge bunches, so we go from 1 nC to 120 nC. The latter is the world's record for a single bunch in L-band photoinjector. For many facilities, 1 nC is "large". We "sneeze" and we get 1 nC.

What is the minimum charge of the bunch available?

Regards, Dany.

 

[rewebster]

$1.50--plus delivery charge

 

[Anonym]

$1.50--plus delivery charge

What is the matter with you? I think you ask a good question.

Regards, Dany.

 

[rewebster]

sorry, just 'injecting' some levity---


you have to watch out for those 'delivery charges'

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The whole field of particle accelerators has probably given us more understanding to the 'field' more than anything else in the last 75 years. It is highly enlightening and there's more coming soon.
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"What is the matter with you? I think you ask a good question.

Regards, Dany."

thanks

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I started looking around the 'net' for some answers, and SOME are seemingly very hard to find. Sometimes the answers weren't specific as to what I was looking for mostly. Like: What is the 'percentage' of energy that results (impacts, calculated from observed) from the 'energy' expended (the whole process) to perform an 'average' test?

 

[Anonym]

I started looking around the 'net' for some answers, and SOME are seemingly very hard to find. Sometimes the answers weren't specific as to what I was looking for mostly. Like: What is the 'percentage' of energy that results (impacts, calculated from observed) from the 'energy' expended (the whole process) to perform an 'average' test?

Some answers of Zz are seemingly very hard to comprehend also:

1.For many facilities, 1 nC is "large".
2.We "sneeze" and we get 1 nC.
3.Don't trust what I just said.
4.Why do you even need to make that kind of speculation?

I did not start with my speculations yet.

Regards, Dany.

 

[Anonym]

Talk is cheap, but when you have a multi-million dollars worth of system to build, such wishy-washy speculation doesn't cut it.
Zz.

Provided we are talking about speculations only.

However, what I have in mind may be called the inverse Schrödinger Cat (determination of the boundary between the Classical World and the Quantum World). Obviously we start inside CED (Zz:” The classical particle tracking code works”).

The fermions fit much better than bosons our everyday experience. Zz mentioned "sneeze". Usually it is due to “cold”. I think I will not be terrible wrong if I consider the Zz electron bunches as droplets of the fermions liquid (“snivel”).

Now, what should happen if I will start to reduce the bunch charge each time one order of magnitude? After ten steps I will remain with the single electron which is described by QED. So, somewhere in between the transition from the Fermi liquid to the Fermi gas should occur. Provided that it will be similar to the phase transition one expect that the accelerator software suddenly will stop working properly.

I believe that N. Bohr is right and the electron spin do not exist in the Classical World. If so, at above discussed boundary the very change in the structure of the space-time continuum may be investigated experimentally.

Perhaps, it is worth to spend several dollars to check that.

Regards, Dany.