Making a Geiger-MÃ¼ller Counter / Electromagnetic Radiation / Forums

Forums

4hv.org :: Forums :: Electromagnetic Radiation

« Previous topic | Next topic »

Making a Geiger-MÃ¼ller Counter

first previous 4 5 6 7 next

Move Thread

LAN_403

Proud Mary

Thu Feb 14 2008, 10:26PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

plazmatron wrote ...

Wow! that site is looking more and more delicious! Thanks Harry!
I`m thinking of taking a wee field trip!
According to auto route, I can make it there in about 3 hours, so If I set off early enough it can be a day out!

There looks to be a golf course immediately behind the cliff, Leslie, perhaps right on top of the original Location 3 trench. As a fallback, you might think about getting a tide-table for the Solway Firth, and seeing how far you can get towards Needle's Eye from Sandyhills Bay at low tide. The Solway Firth is generally <5m so I'd guess you might get all the way to the foot of the cliff - immediately below the vein - at low tide, and come back with rich pickings, provided you bear in mind the great rapidity with which the tide comes in in such shallow seas, and keep a scrupulous eye on the clock when you are there!

plazmatron

Fri Feb 15 2008, 12:32AM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

Funny you should mention that! I was just checking tides, and trying to pinpoint the exact location today.
The pair of veins are on the Southwick coastal reserve, near the Needles eye rock formation so it should be easy to spot!
The tide is fully out around 16:30 on Monday (the day I plan to go) , so I will spend the morning surveying the trench If I can find it (shouldnt be too difficult I`m cheating and using GPS!)

Thanks for the heads up on that one!

plazmatron

Tue Feb 19 2008, 08:26PM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

Well I had a good run to the cliffs at Solway Firth on Monday, and after 5 hours or so, found some classic examples of Pitchblende!
Some are extraordinarily active, even more so than my entire radium watch hands collection!
Thanks again for the tip Harry!

Proud Mary

Tue Feb 19 2008, 09:39PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I'm really pleased for you, Leslie! I can well remember when I found some really active pieces of pitchblende at St Austell, and I could hardly believe how energetic they were.

Now you're in position to try some gamma radiography and all manner of interesting experiments. Whoo-hooo!

plazmatron

Thu Feb 21 2008, 07:59PM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

Absolutely!
I have extracted a small quantity (2g) of fairly pure Uraninite from a soil sample, and sintered it into a small hard pellet to give autoradiography a try. The pellet measures just over 12,000 CPM (combined beta/gamma), so it should give fair results in a comparatively short space of time.

Leslie

Proud Mary

Thu Feb 21 2008, 10:15PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Leslie, here's the website of a very inventive chap whose work I think you'll like if you don't already know of it:

plazmatron

Tue Feb 26 2008, 01:53AM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

Yes I`ve seen his page before. He has done some incredible work. Which reminds me, I must get a decent vacuum setup, I just have to try and build a x-ray tube!

Seoul_lasers

Thu Aug 21 2008, 05:10AM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

c4r0 wrote ...

My counters based on SBM-20 g-m tube easily detects x-rays generated by x-ray tube powered from 50kV. I'm sure that measurement is much lower than it should be, however it detects this radiation. SBM-20 is designed for measuring radiation >100keV.

Medical x-ray machines usually uses 1-2mm Alluminium for filtering, but it's not so necessary until you're not going to x-ray yourself :)

Umm, they usually use lead lining around the tube for filtering. Beryllium is also sometimes used as well as it has a high atomic number. You can seriouly burn yourself with homemade X-rays. ( just like a very bad sunburn) I'd advise you BE CAREFUL.
50Kv-60Kv is more often the range for a dental x-ray machine.
To really see if you have X-rays use a ZnS (Ag) screen below the tube. it will glow green then the power has been turned on.
I have seen small radiotube X-ray machines make some impressive X-ray pictures.

c4r0

Thu Aug 21 2008, 09:51AM

Registered Member #151 Joined: Sun Feb 12 2006, 02:53PM
Location: Poland
Posts: 153

Seoul_lasers wrote ...

I know that there is that lead filter, and i always unwind it off the g-m tube. By the way it's not lead actually becouse i've checked if its good for x-ray tube shielding and its not, about 0.5mm of this metal attenuates just like 2mm of Al.

You wrote that I should use an intensifying screen for detection. Well, in my case the screen glows only in the main x-ray beam so you would say that its ok and safe? My geiger counters are going mad even 5 meters behind the tube (not in front) becouse of scattered radiation and imperfect tube shielding (it can't be perfect). Also while turning anode voltage up the g-m counters laying 1m from the tube starts to tick at significantly lower voltage than the screen placed 5cm from the tube starts to glow visibly. So in my opinion geiger counter is much better for safety radiation detection. Ofcourse it's sensitivity should be checked first.

Proud Mary

Thu Aug 21 2008, 01:48PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

c4r0 wrote ...

I know that there is that lead filter, and i always unwind it off the g-m tube. By the way it's not lead actually becouse i've checked if its good for x-ray tube shielding and its not, about 0.5mm of this metal attenuates just like 2mm of Al.

This is probably a Tin (Sn) or tin alloy filter to smooth out the tube's very uneven energy response curve, though Cadmium (Cd) foil is sometimes wrapped around military G-M tubes to improve neutron counting efficiency.

first previous 4 5 6 7 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob