What is the concept of rf heating in a Paul trap?

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Discussion Overview

The discussion centers around the concept of rf heating in Paul traps, particularly how it relates to the thermal equilibrium of ion clouds with background gas. Participants explore the implications of rf heating, its role in the equilibration process, and the apparent contradictions in the literature regarding cooling efficiency in these systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Kushal questions the relationship between rf heating and thermal equilibrium in Paul traps, expressing confusion over how rf heating can be relevant if the ion cloud reaches equilibrium with the background gas.
  • Thomas suggests that rf heating raises the equilibrium temperature in a manner analogous to how a heater warms a room.
  • Kushal further probes whether the plasma will equilibrate at the background gas temperature and questions the necessity of rf heating in this process.
  • Richard D. Saam explains that different entities absorb RF energy at characteristic frequencies, leading to thermal equilibrium over time, using a microwave oven analogy to illustrate the concept.
  • Kushal cites conflicting statements from the literature regarding the efficiency of cooling in rf traps, highlighting a tension between the effects of collisions with background gas and the heating caused by the rf field.
  • A later participant clarifies that the differing statements about cooling efficiency stem from different criteria for what constitutes "efficient cooling." One refers to the limitations of cooling compared to other methods, while the other discusses the reduction of ion kinetic energy due to buffer gas interactions.

Areas of Agreement / Disagreement

Participants express various viewpoints on the role of rf heating and its relationship to thermal equilibrium, with no consensus reached on the implications of the literature cited by Kushal regarding cooling efficiency.

Contextual Notes

The discussion reveals complexities in understanding the dynamics of rf heating and thermal equilibrium, with references to specific literature that present seemingly contradictory claims about cooling in rf traps. The nuances of these claims and their implications remain unresolved.

kushal
Hello,

I have a question on rf heating in Paul trap.

There are papers which say that in a Paul trap, the ion cloud
eventually comes to a state of thermal equilibrium with the background
gas. And at the same time there is a concept of "rf heating" in these
traps. I am slightly confused about it. If the ion cloud is coming to
an equilibrium, then in what context do we talk of "rf heating"? I
have read some papers on this issue but all seem to be too obscure on
this particular issue.

I would be glad if someone can please reply to this question.

Thanks,
Kushal.
 
Science news on Phys.org
On 24 Sep, 16:22, kushal <atmabo...@gmail.com> wrote:
> Hello,
>
> I have a question on rf heating in Paul trap.
>
> There are papers which say that in a Paul trap, the ion cloud
> eventually comes to a state of thermal equilibrium with the background
> gas. And at the same time there is a concept of "rf heating" in these
> traps. I am slightly confused about it. If the ion cloud is coming to
> an equilibrium, then in what context do we talk of "rf heating"? I
> have read some papers on this issue but all seem to be too obscure on
> this particular issue.
>
> I would be glad if someone can please reply to this question.
>
> Thanks,
> Kushal.[/color]

The rf-heating in a Paul trap would raise the equlibrium temperature
in a similar sense as a heater raises the equilibrium temperature in a
room.

Thomas
 
On Oct 7, 8:14 pm, Thomas Smid <thomas.s...@gmail.com> wrote:
> On 24 Sep, 16:22, kushal <atmabo...@gmail.com> wrote:
>
>
>
> > Hello,[/color]
>
> > I have a question on rf heating in Paul trap.[/color]
>
> > There are papers which say that in a Paul trap, the ion cloud
> > eventually comes to a state of thermal equilibrium with the background
> > gas. And at the same time there is a concept of "rf heating" in these
> > traps. I am slightly confused about it. If the ion cloud is coming to
> > an equilibrium, then in what context do we talk of "rf heating"? I
> > have read some papers on this issue but all seem to be too obscure on
> > this particular issue.[/color]
>
> > I would be glad if someone can please reply to this question.[/color]
>
> > Thanks,
> > Kushal.[/color]
>
> The rf-heating in a Paul trap would raise the equlibrium temperature
> in a similar sense as a heater raises the equilibrium temperature in a
> room.
>
> Thomas[/color]

So, do you mean to say that if the background gas temperature was T,
then after a long time, the plasma will also come to an equilibrium at
temperature T? Will happen even if the background temperature was lower
than the plasma temperature? So, its more like a relaxation process that
takes the plasma to equilibrium and not continuous heating. If that is
the case, then why is it called rf-heating? Even in the absence of the
rf field, the equilibration will, anyways, happen. What is the role of
the rf field in the relaxation process?

Thanks,
Kushal.
 
kushal wrote:
> On Oct 7, 8:14 pm, Thomas Smid <thomas.s...@gmail.com> wrote:
>> On 24 Sep, 16:22, kushal <atmabo...@gmail.com> wrote:
>>
>>
>>
>>> Hello,
>>> I have a question on rf heating in Paul trap.
>>> There are papers which say that in a Paul trap, the ion cloud
>>> eventually comes to a state of thermal equilibrium with the background
>>> gas. And at the same time there is a concept of "rf heating" in these
>>> traps. I am slightly confused about it. If the ion cloud is coming to
>>> an equilibrium, then in what context do we talk of "rf heating"? I
>>> have read some papers on this issue but all seem to be too obscure on
>>> this particular issue.
>>> I would be glad if someone can please reply to this question.
>>> Thanks,
>>> Kushal.[/color]
>> The rf-heating in a Paul trap would raise the equlibrium temperature
>> in a similar sense as a heater raises the equilibrium temperature in a
>> room.
>>
>> Thomas[/color]
>
> So, do you mean to say that if the background gas temperature was T,
> then after a long time, the plasma will also come to an equilibrium at
> temperature T? Will happen even if the background temperature was lower
> than the plasma temperature? So, its more like a relaxation process that
> takes the plasma to equilibrium and not continuous heating. If that is
> the case, then why is it called rf-heating? Even in the absence of the
> rf field, the equilibration will, anyways, happen. What is the role of
> the rf field in the relaxation process?
>
> Thanks,
> Kushal.
>[/color]
Each atomic, molecular, ionic, nonionic entity absorbs RF (or EM in
general) at characteristic frequencies related to its vibrational,
rotational, translational modes. At a particular RF spectrum, one
entity may be 'hotter' than another but with time and constant RF input,
all entities should come to thermal equilibrium.

Consider a frozen dinner in a microwave oven. The meat, vegetables and
dessert each heat a different rates (cover some and not others) such
that after the instructed cook time, all are at a different but
acceptable temperatures.

Now for arguments sake, keep the dinner in the microwave oven for an
extended period of time (hours?) and the whole thing would be at some
type of unpalatable thermal equilibrium.

Richard D. Saam
 
On Oct 9, 9:58 pm, Richard Saam <rds...@att.net> wrote:
> kushal wrote:
> > On Oct 7, 8:14 pm, Thomas Smid <thomas.s...@gmail.com> wrote:
> >> On 24 Sep, 16:22, kushal <atmabo...@gmail.com> wrote:[/color][/color]
>
> Each atomic, molecular, ionic, nonionic entity absorbs RF (or EM in
> general) at characteristic frequencies related to its vibrational,
> rotational, translational modes. At a particular RF spectrum, one
> entity may be 'hotter' than another but with time and constant RF input,
> all entities should come to thermal equilibrium.
>
> Consider a frozen dinner in a microwave oven. The meat, vegetables and
> dessert each heat a different rates (cover some and not others) such
> that after the instructed cook time, all are at a different but
> acceptable temperatures.
>
> Now for arguments sake, keep the dinner in the microwave oven for an
> extended period of time (hours?) and the whole thing would be at some
> type of unpalatable thermal equilibrium.
>
> Richard D. Saam[/color]

Yeah, that makes sense if one accepts that the plasma comes to some
kind of thermal equilibrium.

However, I was going through the literature on rf traps and came
across two statements that seem to say different things:

1) I. Siemers, R. Blatt, Th. Sauter and W. Neuhauser, Phys. Rev. A 38,
5121 (1988)
"On the other hand, in experiments on ion clouds in rf traps,
efficient cooling is impossible, since collisions between the ions and
with the surrounding background gas in the presence of the time-
dependent trap potential leads to heating."

2) F. Vedel, International Journal of Mass Spectroscopy and Ion
Processes 106, 33 (1991)
"Since the earliest experiments with Paul traps, it has been
recognized that collisions with a light buffer gas enhance the
lifetime by reducing ion kinetic energy"

How does one reconcile these two statements?

Thanks,
Kushal.
 
These two statements have different criterion of what is efficient cooling.
In the first case, it means the ions can not be cooled at efficient as MOT trap, which could achieve 10^-12 K on atoms.

In the second case, it means buffer gas reducing ion kinetic energy compared with NO buffer gas.

It's like to say, A human is "bigger" than an ant, but "smaller" than an elephant.


---------------------------Quoted--------------------------------

However, I was going through the literature on rf traps and came
across two statements that seem to say different things:

1) I. Siemers, R. Blatt, Th. Sauter and W. Neuhauser, Phys. Rev. A 38,
5121 (1988)
"On the other hand, in experiments on ion clouds in rf traps,
efficient cooling is impossible, since collisions between the ions and
with the surrounding background gas in the presence of the time-
dependent trap potential leads to heating."

2) F. Vedel, International Journal of Mass Spectroscopy and Ion
Processes 106, 33 (1991)
"Since the earliest experiments with Paul traps, it has been
recognized that collisions with a light buffer gas enhance the
lifetime by reducing ion kinetic energy"

How does one reconcile these two statements?

Thanks,
Kushal.[/QUOTE]
 

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