radiation detection with a geiger mueller tube - sensitivity / efficiency

[blackwolfkodi]

Um, one of those disks has gamma decay, why would you touch that? gamma needs at least a foot of lead to stop it...

[sheattri]

I live in So. California near a Nuclear Power Plant that will only sustain a 7.1. I would like to buy one of these but I have no idea which one to buy to know if there is any fallout from Japan or if our power plant blows, when should I take my KIodide. There are so many, CD V700, 715, 717 ??? Some have mueller tubes and some done? What do the dosimeters do? Someone please tell me. Thanks!!!

[bionerd23]

@sheattri

if i'd type that out, i'd have to post approx. 300 comments, so that's useless. goto wikipedia and check for dosimeters and geiger counters and follow the links to more information. differences in CDV are usually ion chambers vs. geiger mueller counters. more info on wikipedia.

for more info on CDV meters, goto:

orau.org/PTP/collection/civild­efense/civildefense.htm

[bionerd23]

@BobbiBeach

very good idea. i'm too far away (germany) to experience any increased radiation levels yet, and i probably never will, but it's a very good idea, e.g. for people in asia and especially the west coast of the USA, too.

[Huffdev]

I have a torbernite sample and it gets about 500,000 CPM is that dangerous i dont know if its calibrated though but thats what im reading

[Obi007007]

GOOD

[eaglevision993]

Der gute alte CDV 700 ;-) - bulletproof gerüstet für den nächsten Atomkrieg hehe.

Aber wenns um Genauigkeit geht vertrau ich eher auf den GammaScout. Auch wenns mit dem CDV 700 aus irgend einem Grund mehr Spass macht.

[sovageek]

Well ok, just that you are sure what exposures you have are within reason and are safe. I have a gamma scout but would love to have one of the cheap russian ticking counters for "everyday carry" and for listening in on local mineral formations in my area. if you know of a reliable retailer of these 'cheap' counters then let me know!

[bionerd23]

@sovageek

sure, there's always some of these around on ebay. :)

[sovageek]

Be careful!!! I love all your vids but watch out your fingers don't turn black from handling those sources. Radiation exposure is cumulative in how it affects living tissues. Use a lead shot 'vest' and tongs to handle the hot stuff. What happened to your Gamma Scout? You usually have it measuring your experiments. Which spider plants survived? I have been offline for a while.

[bionerd23]

@sovageek

that wont happen, i could even tape those three sources to my forehead for a day and nothing would happen, not even a minor redness. :P

my gamma scout has been replaced with a better working one, but i have a pancake probe CD V-700 as well now, as seen in this video. how and why is explained in videos i did about both topics. all spider plants except toilet plant survived.

[cortana2007]

is your pancake geiger tube capable of detecting alfa radiation to?

it would be interesting if you put a inox plate in front of tube. theoreticaly this increase the detection capacity for gama radiation of the tube.

my CDV 700b has a tubular probe with a heavy inox shield. first it is a beta shield but it will emit fast electrons when it is hit by gama rays. these electrons are detected by the geiger tube. (that is was the book said) :)

[bionerd23]

@cortana2007

yes it is, it has a thin mica window. what you say sounds interesting; gamma rays can knock out electrons of a material if the energy of the ray is higher than the binding energy of the electron (that's what happens in the cathode of the geiger mueller tube as well when detecting gammas - it detects those electrons). i've never heard of it working that well with inox, but will look it up and try it! thanks a lot for the tip!

[michalchik]

@bionerd23 Well back when I used to do auto-radiography, radio-immune, radiolablled DNA synth assays, and other techniques, we always had a little badge we wore that helped us keep track of our exposure levels. It was photographic film that would detect penetrating radiation. I think there are digital ones now.

[bionerd23]

@michalchik

they still use those film dosimeters, at least here. :)

it's very accurate and cost-effective, so they stick with it.

if only a short-time exposure of a non-permanent personell is measured (e.g. during one week), pen dosimeters are widely used.

[tesla242]

I will never get tired of saying it, you ROCK! jejeje excellent video!

Again, you target just the point, as you show as in this video, the GM tubes, are good but just if you now almost very well what kind of radiation (types and energies) are you measuring. As an example of this, the 0.9uCi source of Am241 only marks 300cpm on the tipical inox soviet GM tube SBM20, but in the scintillator with a crystal for gammas, get more than 9000cpm (at the 55KeV line)

[tesla242]

(Continues from the last message). On the other hand, for example, a Uranium glaze (like fiestaware), show on the same soviet tube, more than 1200cpm, but in the scintillator I almost get "background levels", mainly because, there is no gamma radiation to detect, and the emission from the glaze is almost beta+alpha.

[bionerd23]

@tesla242

yeah, exactly. =)

you should do a video about this, as you own a glorious scintillation counter, lol! no really, you should!

[tesla242]

@bionerd23 Jejejej I.O.U., I will try to make a video reply to this video this week, comparing reading between the two instruments ;)

[cyberbadger]

How did you come up with the Becquerel to counts/minute estimates? This would be interesting to know? (Seems like reasonable estimates - just was wondering how you came up with them)

[10mintwo]

@cyberbadger  a curie = 3.7e+10 Bq

[bionerd23]

@cyberbadger

counts/second it is, i am converting everything to cps in the video; the CDV shows cpm. ;)

anyway, conversion from uCi to Bq states the total activity of the source. it's a flat source disk, so it basically has two sides, so i take half of the activity, as we're measuring just one side... and then minus something again, as some of the radiation will escape from the sides, too (you can see that in watch?v=I_txeufgt_4 - near the end, i believe).

[DaedricLavaWhiskey]

lool... dare you to eat those radioactive chips

[bionerd23]

@DaedricLavaWhiskey

way too expensive. i could eat a tin of real sturgeon caviar for the price.

[DaedricLavaWhiskey]

@bionerd23 LOL caviars so disgusting id rather eat the expensive chips

[michalchik]

So, do you wear a dosimeter?

[bionerd23]

@michalchik

what do you mean? a pen dosimeter? nope, i dont. not around the house, anyway.

[Parashooters]

So if gamma isn't really detected, would a Geiger counter be able to hypothetically pick up x-rays?

[bionerd23]

@Parashooters

sure, in much the same way it picks up gamma rays. gamma- and x-rays are exactly the same stuff; they just have different names (x-rays are generated in man-made electron tubes, gamma rays come from radioactive decay / excited daughter atoms). (cont)

[bionerd23]

@Parashooters

(part two)

x-rays usually have energies of 40-300 keV; some gamma rays are in this range, too, like from Barium-133, which emits gamma rays @ 130 keV - a typical energy for x-rays (120 kV are widely used to x-ray humans). gamma rays emitted from a Cs-137 source, again, have 660 keV and are thus very far into the "common gamma ray" range.

[Geomanb]

schöner Versuch

[bionerd23]

@thelleht

(part 2 of the reply)

by using a very dense cathode material, the gamma detection rate can be increased; this also goes for using more dense noble gases, where the best bet would be xenon. radon would be even better, but just in theory, as radon is radioactive by itself... if there was a stable isotope of radon, however, that'd be the best gas for detecting gammas / x-rays!

[bionerd23]

@thelleht

yeah, exactly. especially, all of them usually move through the gas without interacting with it, as alpha / beta particles would; most of the detected counts come from electrons that are "knocked out" of the cathode material rather than atoms in the tube gas! this is especially the case with neon-filled tubes, which i guess this one is, too (not 100% sure though, but my gamma scout uses neon).

[PsychoticBovine]

@bionerd23 My cdv 700 (victoreen manufacturer) uses a 6993 geiger tube filled with halogen. Not sure if this is accurate, but found this info on a website: "Instrument accuracy on any of its three ranges is within ± 10% of the true dose rate from Cobalt 60 gamma radiation. "

[PsychoticBovine]

sorry, I spoke too soon. I think the 6993 tube uses neon, with halogen as the quench gas.

[bionerd23]

@PsychoticBovine

i was juuuuust here to reply to your comment that said "I know my cdv-700 with it's normal tube (not a pancake) uses halogen.", but you already said what i wanted to say, so yeah. ;)

anyway, it's always noble gas + halogen, yes.

[PsychoticBovine]

@bionerd23 I do confess I know so very little about such things. When I do comment I do feel kind of foolish with my lack of knowledge. My father said I should have studied physics, but I have a serious weakness for math.

[bionerd23]

@PsychoticBovine

lol, dont worry about it. you live and learn, it's normal. :)

like i once believed uranocircite's beautiful green glow was due to phosphorous in the molecule, while it was in fact the uranyl ion that is responsible for the fluorescence... as long as you're open-minded and always question everything, including yourself, it's not shameful to be "wrong", i think.

were you always weak with math, by the way? or did a horrible teacher just "induce" this, possibly?

[PsychoticBovine]

@bionerd23 Math has always come hard for me, I tend to lean more towards writing, communication, and literature. But nearly everything science-related just fascinates me. Electricity and radioactivity especially.