Observations with a crystal

plane sound went away.

We used to get some low flying jets around here too, very loud indeed.

There is a story, possibly apocryphal, about a lady who phoned up the RAF to complain about the noise from the latest flyover.

"I'm sorry madam... were you able to see the type of aircraft?"

"No... but I'd recognise the pilot if I saw him again."

--

John Devereux

On a sunny day (Sun, 23 Oct 2011 11:17:11 -0700 (PDT)) it happened whit3rd wrote in :

Well, for a start I have a 2 x 150 Watt RMS audio system that does not seem to affect acquisition in any way. And how could it? Do you think the PMT will produce extra pulses on vibration? Sure the facts you mention may change gain in a minute way, and that would then happen at the audio frequency, and that would cancel out over more than one of the lowest vibrating periods, and that period (say 20 Hz or 50 ms) would be very short compared to the acquisition times, or even the several seconds acquisition time where the phenomena was observed. You can tap the PMT and it wont make any difference. After all it is just detecting flashes of light. It needs an electron released at the cathode to start with, and that electron does not listen to music, but mostly to EM waves. The only 'external systematic' influence that got me in the beginning was that I wrapped it in dark plastic, and it then showed small pulses for some minutes. I found that was static electrical discharges (sparks) in the plastic as it settled. Bummer, no signal, looked so good :-)

On a sunny day (Sun, 23 Oct 2011 23:05:43 -0700) it happened John Larkin wrote in :

Oh I am sure if you hit a piezo crystal with a modulated neutron beam of enough strength it would react. With enough strength it may even damage the quartz. Nuke it so to speak :-)

On a sunny day (Sun, 23 Oct 2011 19:42:12 +0100) it happened John Devereux wrote in :

plane sound went away.

Yep, that was my first explanation, but no other airplane seems to do that now. That is why I waited a week before even posting this.

On a sunny day (Sun, 23 Oct 2011 21:33:46 +0100) it happened Martin Brown wrote in :

plane sound went away.

Yes, exactly the same here, there is a shooting range for the F16 (and bombing too) at an island near to here. Did not have any problems with my security cameras though, but those have IR filters. F16s used to crash all the time too, last one dropped in the sea nearby, lately they seem to be more reliable. Last one was a pilot error IIRC, did not see the horizon, flying into the sea. What that sort of thing happens it is all helicopter traffic too. IIRC helicopters that used to be at Den Helder are now stationed here too. One came over so low that the roof tiles came lose, just shaken, but not stirred... Somebody hopefully complained....

As to targeting, there is this 'friend enemy detector' system, and some years ago that did not work, and they shot the tower...

They also fly helicopters looking for IR signature from grow lights for marihuana plants. Been over my place several times, used to have a lot of electric power running...

An F16 crashing in your garden is not as interesting as an UFO though, but maybe some parts could be used, I bet they have good stuff.

On a sunny day (Mon, 24 Oct 2011 07:34:28 +1000) it happened David Eather wrote in :

plane sound went away.

But why not on all the other planes?

On a sunny day (Sun, 23 Oct 2011 23:18:33 -0500) it happened Jon Elson wrote in :

Interesting, how about this: In one of the google groups like perhaps it was ttp://tech.groups.yahoo.com/group/GeigerCounterEnthusiasts/ I did read that un the military airplane dump there were many instruments (dials) painted with radium. They even installed radiation screens. The guy could see a big counter tick increase if he drove past it on the highway.

And spacecraft detect particles knocked by solar radiation from the surface of planets from many kilometers upwards to detect the composition of the ground.

Note the type of crystals. I dunno what they will have you believe, but reality is almost better than science fiction. distance.

On a sunny day (Mon, 24 Oct 2011 09:10:11 +0100) it happened John Devereux wrote in :

:-)

plane sound went away.

Yeah, that part makes it a puzzle. Perhaps pilot error leaving a radar on, or on a high powered mode, rather than the normal landing / ILS procedures - but that is just me speculating.

strength

I was thinking about single particle detection. An healthy alpha will make a visible flash of light when it hits a ZnS scintillator, and I suspect that conversion efficiency is low. So there should be enough energy to make a detectable vibration in some piezo material.

How about a tiny chamber filled with a dense gas, like xenon or something? An absorbed alpha will spike the temperature and raise the pressure, maybe enough for a microphone to detect. Or whack an electret mike film directly with alphas.

Lots of fun possibilities. Flexy mirror and laser, maybe, like an AFM tip thing.

John

plane sound went away.

Perhaps he was being actively targeted - what with all his nuclear materials lying about... :)

--

John Devereux

strength

I was thinking about single particle detection. An healthy alpha will make a visible flash of light when it hits a ZnS scintillator, and I suspect that conversion efficiency is low. So there should be enough energy to make a detectable vibration in some piezo material.

How about a tiny chamber filled with a dense gas, like xenon or something? An absorbed alpha will spike the temperature and raise the pressure, maybe enough for a microphone to detect. Or whack an electret mike film directly with alphas.

Lots of fun possibilities. Flexy mirror and laser, maybe, like an AFM tip thing.

John

enough strength

Back around 1988, when I was building magnetic-force AFMs, the group I was in was doing a lot of vaguely similar sorts of things, though mostly with optical detection. The problem is that Avogadro's number is really, really big.

The momentum of an alpha goes like the square root of the energy, and the momentum is what makes things ring. Momentum is always conserved in a collision, so using the identity

KE = p**2/(2M),

an alpha particle hitting a mass-and-spring resonator with mass M in the optimal direction transfers an energy

dE = E_alpha*M_alpha/M.

Thus a 1-ug resonator hit by a 10 MeV alpha particle will start ringing with an energy

(1e7 eV)(1.6e-19 J/eV) (4 AMU)/6.02E23 AMU/g) dE = --------------------------------------------- 1 ug

which is 1.06E-29 J.

The thermal energy in that resonance mode is 1/2 kT, or 2E-21 J at room temperature, so it would take about 500,000 properly-timed alpha impacts to reach a SNR of 0 dB.

Cheers

Phil Hobbs

enough strength

In addition to momentum, the alpha will deposit a slug of heat. A 10 MEV alpha packs around 2 picojoules, enough to make a visible flash of light with an inefficient phosphor, so there are probably many ways to detect that much energy.

John

enough strength

Sure. Photothermal is also inefficient, however, because of the 3D diffusion. At one point there was a company called ThermaWave out your way that measured thermal properties of surfaces with a pulsed laser and some acoustic transducers, and then with optical detection of the surface displacement. It was noninvasive but not very sensitive.

Cheers

Phil Hobbs

Possibility 1 - since radar is a beamed directional signal, the plane in question might just have happened to be "looking" in your direction at just the right time.

Possibility 2 - only certain radar frequencies may result in false-triggering of your test apparatus. This might happen (for example) only when the frequency of the radar happened to match a resonant mode for one particular wire in the test arrangement, or an element in the PMT itself.

Your crystal-and-PMT arrangement may be acting as "a crystal radio set of enormous power" (to quite from "Star Smashers of the Galaxy Rangers"), and you unknowningly had it tuned to the radar frequency being used by that particular jet.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

(dials) painted with radium.

highway. Wow, this must have been a LOOONG time ago! I have some WW-II and Korean war (~1951) aircraft instruments that have phosphorescent dial markings. These are NOT radium, but just a phosphor that lights up in visible when illuminated by UV. They used UV fluorescent lamps to illuminate the instrument panels.

Jon

air-base..

the plane sound went away.

Are you well enough shielded that you can eliminate hard x-rays from a marginal power supply?

?-)

Larkin

:

=A0

s

of enough strength

Hmmph. Set up a "cloud chamber" it is only high school grade physics. Heck, i saw one in 6th grade. Bloody cool at the time, but not all that difficult. Helium bubble chambers are rather more difficult.

?-)