MASER's

Magnetrons are tuned by the geometry of a vacuum tube's electrodes, and build up oscillations in an electron beam. MASER action occurs in a stimulated emission (from a microwave spectrum line in an atom). So, the only common MASER devices one sees are those Rubidium clocks. MASERs are kept accurate by the characteristics of the identical atoms, not tuned circuits or mechanical structures.

The closest to a hybrid of both, is a storage ring with coherent photon output from a multipole structure of very fine tuned magnets. The electrons have to be relativistic for efficiency, and the resulting LASER/MASER gizmo is called a free electron laser (FEL). Magnetron -> cyclotron -> synchrotron -> FEL are generally titles applied to members of that family.

The MASER was a quantum-mechanical oscillator invented by Charles Townes in 1953. Townes and two others got the Nobel prize.

Masers have been used as oscillators (time standards) and low-noise microwave amplifiers.

The cavity magnetron was invented during WWII.

The maser lead directly to the laser; it's the same basic physics.

A good book:

Nobody believed he could create the Einstein-specified inverted energy population; the thermodynamics looked impossible to the experts, so it almost didn't happen.

Lasers could been built in any good neon sign shop in 1900.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

There are maser-based time standards, but the usual rubidium standard is not a maser. It uses optical-wavelength absorption in a gas, not amplification or oscillation.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

I only have a basic non-physicist's understanding of how a LASER works, but is it correct to say that a LASER and a MASER are fundamentally the same except for wavelength?

And from the above I gather that oscillation in a MASER is electrical rather than electromagnetic.

It's actually quantum-mechanical - molecules or atoms switching between discrete energy states.

You can design a magnetron without reference to the quantised energy levels. Masers and lasers depend on transitions between quantised states.

--
Bill Sloman, Sydney

That should have been:

And from the above I gather that oscillation in a _magnetron_ is electrical rather than electromagnetic.

** This link has good detail of practical RADAR magnetrons.

The devices involve fast electrons in a vacuum, a strong magnetic field and outputting EM waves at high power.

So I reckon "electromagnetic" is the right word.

.... Phil

The electron paths are directed by electric and magnetic fields, and the speed of light is important. So it's electromagnetic. Most everything is electromagnetic.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

The main difference is the limited Q factor of a mechanical enclosure vs the incredibly high Q factor of a stimulated quantum emission.

Rubidium isn't a maser. H-masers are used as local clocks at VLBI observatories because their short term stability is better.

Pretty much Amplified by Stimulated Emission of Radiation. You have to be able to create an inverted population of excited atoms in a metastable state waiting for a photon to trigger them into action.

There is a trick for making X-ray lasers

Masers were relaised in the lab before lasers.

There is something of a patent bun fight over who invented the laser

Early lasers did this with a powerful flashgun and semi silvered mirrors on the ends of a ruby.

Today there are free-electron lasers operating into the X-rays now.

No. It is just electromagnetic radiation and can occur naturally. OH masers are seen in regions of star formation pumped by the UV of bright young newly formed stars acting on the nebula they formed from.

One of the best know is W3(OH).

Regards, Martin Brown

>

To me the major distinction is the laser/ masers use Einsteins's A and B coefficients. Stimulated absorption, spontaneous emission and stimulated emission. (E's genius was to see that stimulated emission had to exist.) So l/maser's need to make (the legendary) population inversion to work. You can get pop. inversion by different means.

George H.

Townes' attempt at the maser was almost de-funded by experts who thought that thermodynamics forbids the population inversion that makes lasing possible. I think that even Einstein discounted maser action.

I just read a good book. "Wrong", that makes the case that most experts are usually wrong.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Speaking of experts being very, very wrong...

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

There are lower-Q laser systems such as free-electron lasers. Those are sor t of intermediate between magnetrons and normal lasers.

And the very narrow line width of lasers isn't primarily due to the gain li ne width--in diode lasers that can be ~1 THz wide--but rather to putting th e gain medium in a big long Fabry-Perot interferometer (the laser cavity) a nd then applying regenerative feedback by pumping well above threshold.

Much the same line-narrowing effect occurs in electronic oscillators.

Cheers

Phil Hobbs

The founding of quantum optics by Hanbury Brown and Twiss almost met the sa me fate, at the hands of a rampaging mob of respectable physicists who had accepted an erroneous argument to the effect that photons from distinct sou rces couldn't interfere. How they explained their kitchen radios, I have no idea.

Optics is just like RF, except with smaller waves and bigger quanta.

You can pump an ammonia maser with nothing more than a magnet.

Cheers

Phil Hobbs

High school kids are building things like lasers and SEMs and high-temp superconductors and NMRs that could have been made in 1930.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

You've been listening to James Arthur again. The article is not about bankers being wrong but rather about them not having the tools they need to influence consumer confidence to the extent that is necessary.

--
Bill Sloman, Sydney

I'm not so sure about that. In about 1970, I was working for a communications accessory company that made CTCSS/PL tone boards for commercial FM radios. The design used a Twin-T filter and oscillator. In order to obtain sufficient frequency stability, it was decided to build the device using a ceramic substrate type hybrid circuit. Among the equipment required was a HeNe laser used to trim the fired resistors to the desired values. The decision was made to build our own which was a close equivalent to having a neon sign shop do the work. The only difference was it was 71 year later.

On the principle of "Learn by Destroying" we successfully reinvented the wheel and recreated all the basic problems inherent in building a

10 watt HeNe (Helium Neon) laser. It could scribe the ceramic substrates, trim resistors, burn holes in things, and produce a thermal shock sufficient to simulate a fragmentation bomb. Details on demand if anyone wants them (and if I can remember them). We also managed to invent some new problems, such as converting the laser cut line into a seismograph simulation as a train passed by a few meters from the building. Without an understanding of physics and mechanics involved, I don't think it could have been possible in 1900 even if the neon sign shop was supplied with plug-n-play components. It's not as easy as it sounds.

HeNe Lasers:

Disclaimer: The laser was not my project. I was only involved when things went awry and required troubleshooting. I don't know (or understand) all the details.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

How ironic! Is the author an expert? Is he wrong?

It's hard to apply this kind of distinction, though, to a free electron laser. It gives off coherent light, by dangling its magnetic fingers in a running stream of charges.