CO2 laser and sigarette smoke question

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    Co2 Laser Smoke
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Discussion Overview

The discussion revolves around the behavior of cigarette smoke in the focus area of a CO2 laser, particularly why the smoke is expelled in the direction of the laser rather than away from it. The context includes both historical anecdotes from a lab environment and speculative scientific reasoning related to laser physics and momentum transfer.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant recalls a lab anecdote where cigarette smoke was introduced into a CO2 laser's focus area, leading to a question about the smoke's behavior.
  • Another participant expresses a desire to see a video of the experiment, noting current restrictions on such practices.
  • A participant reflects on the pride and creativity in their work environment, mentioning the historical significance of their laser development efforts.
  • One hypothesis suggests that the smoke's movement could be due to momentum transfer from photons, referencing a humorous comparison to levitating a squirrel.
  • Another participant proposes that the temperature differences in the cigarette smoke and the reactive forces from burning could explain the observed behavior, questioning why the temperature is higher on the focus side.
  • A later reply discusses the possibility of smoke particles heating up and ionizing, forming a plasma that absorbs laser energy and creates pressure directed towards the laser, suggesting this could explain the smoke's movement.

Areas of Agreement / Disagreement

Participants present multiple competing views and hypotheses regarding the behavior of the smoke, with no consensus reached on the exact mechanisms at play.

Contextual Notes

Some claims rely on assumptions about the behavior of light and matter interactions, and the discussion includes speculative reasoning without definitive conclusions.

Who May Find This Useful

Individuals interested in laser physics, experimental setups involving lasers, or historical accounts of laser technology development may find this discussion relevant.

Minich
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In 1975 I've got the job in lab constructing middle power one mode CO2 lasers for outer space object location (they used C and O isotopes for reducing losses in atmosfere).

The main joke for newbies of our lab's boss (Yuri Vasilievich Pechenin) was to breathe sigarette smoke from mouth into focus area of operating laser (1 to 3 kilowatt output radiation ordinary).

And there was a question:

Why was the smoke rocketed from focus area in opposite direction (from focus to laser)?

I don't remember the reason. Who can help?
 
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Sure would like to see a video of this.

unfortunately in this day and age they will not let us any where near our lasers with a cigerett in hand (or mouth for that matter!)
 
Our boss wanted to show us that we work in proper place. And we worked with greate emotion and proud that we make best in the world lasers those days :)))

And lasers were not scientific installations only, they were produced in series at the plant. They were industrial lasers.

We were fascinated by creative atmosfere.We were aheard of laser groups in USSR, headed by Nobel Prize wiiners Basov and Prochorov (in CO2 line)..

I think video of those days are for restricted access only.
 
Perhaps a hefty transfer of momentum from the photons? According to widely cited academic sources (XKCD) it takes 1.21GW/m^2 to levitate a squirrel of mass 0.7kg. Consider that gas particles have masses lower by several orders of magnitude ;)

Also, it might be a heat/pressure wave. When I place something into the focal point of a reasonably high powered laser it begins to emit white light.
 
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To dst.

I remember it is connected with the temperature of spots on sigarett smoke bit and reactive force due to sigarette bit burning. But why is temperature on focus side higher?

Sigarette bit in laser beam is burning inhomogeneosly and behaves like rocket.

Excuse my poor english. I had never been outside former USSR and had never practice in written english.
 
I'll have a go at this;

If the laser spot hits the smoke particles they will heat up, if sufficient heat is imparted on the particles they will ionize forming a plasma.

This heated vapor at first directs pressure in all directions, however, the plasma absorbs most of the incident light, so the front of heated dusted partciles traveling towards the laser acts as an absorption front fot the laser energy, which in turn exerts pressure towards the laser.

In simple terms, there is an absorbing front created by the smoke plasma which travels towards the laser by the expansion of the heated gas.

Why doesn't it go in all directions? Simply because the point of absorption is getting closer and closer to the laser.

Does this help?