Geiger Müller tubes on flights

[Lewis]

Hey.

I was wondering if taking a pancake detector style GM tube with a thin MICA window onto an airplane as hand baggage would distroy it due to the changing air preasure.

Iv heard that the cabin preasure can deivate upto 8000 feet AGL which is the maximum rated altitude for most GM tubes.

Iv certainly seen smaller geiger counters survive just fine on airplanes(example: gamma scout), but i dont wanna pay 150$ for a replacement probe if its any different for larger GM tubes.

Thanks.

[Geoff]

I'm not sure if it would be safe as I've never done it. I've only taken scintillation detectors when travelling. However, living in Alaska required the majority of my mail to come by air and I've had three different thin window GM tubes sent to me without issue. None of them were in pressurized packaging.

[Svilen]

I guess nobody can guarantee it, but you may have good chances not to loose the tube.
I got one Ludlum model 44-9 probe with a LND7311 GMT shiped all the way from USA to Europe in a non airtight container and it survived. But the producer warns in the manual that "The GM tube face can rupture above 8000 feet in altitude", so cases like this should also exist.
I also have one Philips ZP1431 with d~30mm mica window, which flew between eastern and western Europe and also survived, but of course we have to ship at least 10, to different locations and then make a conclusion.

I don't know which detector do you use, but if it is with an external probe, maybe you can get one russian SI-8B tube, which are shown from different users to survive at high altitude and even if not, you loose half the amount of money you mentioned :)

[Lewis]

I guess nobody can guarantee it, but you may have good chances not to loose the tube.
I got one Ludlum model 44-9 probe with a LND7311 GMT shiped all the way from USA to Europe in a non airtight container and it survived. But the producer warns in the manual that "The GM tube face can rupture above 8000 feet in altitude", so cases like this should also exist.
I also have one Philips ZP1431 with d~30mm mica window, which flew between eastern and western Europe and also survived, but of course we have to ship at least 10, to different locations and then make a conclusion.

I don't know which detector do you use, but if it is with an external probe, maybe you can get one russian SI-8B tube, which are shown from different users to survive at high altitude and even if not, you loose half the amount of money you mentioned :)

Thanks for the reply.
Im planning on buying a Radiation Alert Ranger EXP. According to the specs listed on www.geigercounters.com, its using a:

”RAP-RS2 Probe - External Halogen-quenched, uncompensated GM tube with thin mica window, 1.4-2.0 mg/cm2 areal density. Effective diameter of window is 45 mm (1.75 in.)”

So basically, a very common pancake style GM tube for detecting alpha, beta & gamma/xray’s.

[Lewis]

I'm not sure if it would be safe as I've never done it. I've only taken scintillation detectors when travelling. However, living in Alaska required the majority of my mail to come by air and I've had three different thin window GM tubes sent to me without issue. None of them were in pressurized packaging.

Sounds like either the 8000 feet AGL thing is a relatively sand-bagged estemate or modern airplanes maintain they’re cabin preasure relatively well.

[Svilen]

Sounds like either the 8000 feet AGL thing is a relatively sand-bagged estemate or modern airplanes maintain they’re cabin preasure relatively well.

I think these both are true indeed.

[ColoRad-o]

I have taken a data-logging GM counter (a Mazur PRM 9000 with an LND 7317 pancake GM tube) on a flight of a few hundred miles. It operated fine and the radiation rate (as is well known) depends so sensitively on altitude (at least for ordinary flights) that it could be used as a crude altimeter. I found that count rates increased by a factor of 25 between cruising altitude and sea level.

Take a look at https://iopscience.iop.org/article/10.1 ... /4/003/pdf for more.

[Lewis]

I have taken a data-logging GM counter (a Mazur PRM 9000 with an LND 7317 pancake GM tube) on a flight of a few hundred miles. It operated fine and the radiation rate (as is well known) depends so sensitively on altitude (at least for ordinary flights) that it could be used as a crude altimeter. I found that count rates increased by a factor of 25 between cruising altitude and sea level.

Take a look at https://iopscience.iop.org/article/10.1 ... /4/003/pdf for more.

Did the air preasure change during the flight, according to your inbuilt barometric altimiter (inner ear)?

[ColoRad-o]

Re: "ear barometer"--Could I feel a reduction in air pressure in an airplane cabin? Not to any significant extent, if I remember rightly. According to the WHO, "Although aircraft cabins are pressurized, cabin air pressure at cruising altitude is lower than air pressure at sea level. At typical cruising altitudes in the range 11,000–12, 200 m (36,000–40,000 feet), air pressure in the cabin is equivalent to the outside air pressure at 1800–2400 m (6000–8000 feet) above sea level."

I live at 6000 feet, so wouldn't have noticed air pressure differences even at 8000 feet equivalent altitude.

Another point I failed to note before: naturally the pressure inside the GM tube will be LOWER than atmospheric to permit the discharges required. Wikipedia claims it's about 0.1 atmosphere. Thus the roughly 25% reduction in air pressure at cabin pressures, say .76 bars vs. 1 bar at sea level, is small in comparison to the pressure gradient on the mica window of a pancake GM tube. Rooting around on the LND site, I found no mention of maximum operating altitudes.

[iRad]

I have never seen anything on the LND web site or in their specifications or literature describing an altitude or atmospheric pressure limit for the 7311 pancake detector or any other they manufacture. However, in 1987, Ludlum (maker of popular pancake detectors based on the LND 7311 detector) issued a newsletter (NwsLtr-4re.pdf) warning of possible failure of their detectors when being shipped on unpressurized aircraft. They sometime thereafter added to the Model 44-9 User manual the following warning (which continues to this day):

Caution!
The GM tube face can rupture above 8000 feet in
altitude. When transporting this detector by air, use an
airtight container in order to avoid sudden atmospheric
changes resulting in tube failure.

According to George Dowell, Bill Lehnert of LND verified the following:

LND 7311-Routine operation at 5000-6000 feet no problem, i.e. Denver, Los Alamos. Above that they work fine until the reverse bow becomes a problem in the housing. Once the bow has reversed, the tube will continue to work fine. It is not a good idea to cycle between high altitude and low altitude, as eventually the seals will suffer.

I have shipped hundreds of these type detectors with no issue that I have ever been made aware of. However I have heard and read of numerous reports of users experiencing issues or rupture of their pancake detectors operating at high altitude, so I'm sure it is an issue to be aware of. I can verify that even here at sea level (Florida east coast), they can "pop" very easily if mishandled. Actually quite startling the first few times it happens. :)