Trinitite with Graded Shield
Posted: 23 Sep 2019, 02:46
Hello there,
This weekend I tested my third Trinitite sample and it was also an opportunity to test version 1 of my shield.
The graded shield is made of an cylinder of plastic inside a cylinder of copper with lead sheets wrapped around it. The lead is Radmax sheets from United Nuclear. The sheets are 15 cm wide and 3.60 meters long (divided in four sheets) for an equivalent thickness of lead between 1.2 cm and 1.5 cm. A single sheet of lead is placed in front of the shield, creating a sort of room for the sample. This needs to be improved as well.
This is not the final version, so I won’t report about it in the shielding section yet.
Anyway, the goal is to have something that can be easily assembled, disassembled, with the chance to add or take away parts of it independently from the rest. In one word: flexibility.
The shield needs to be improved, I need more lead and also (thanks to Steven tip) also some pewter to attenuate fluorescence from lead.
Anyway, version 1 of the shield still worked not too bad. CPS from the background decreased from 256 to 64, that’s 75% less. In terms of energy the decrease was 55%, which is an indication the shield is more effective in blocking low energy rather than high energy gammas. That’s no surprise of course.
The fluorescence from the shield is clearly visible in the background spectrum.
There’s nothing new to say about Trinitite and about the expected peaks. This sample was made of three pieces, two medium sized ones and a small one.
The three of them together gave me 2100 CPS on my Geiger counter. As usual never judge a sample by its size, the most active one was by far the little one, 1200 CPS versus less than 500 each from the bigger ones.
After recording a 12 hours background I went for a 24 hours measurement of the samples.
This time I had roughly 9 CPS from the sample versus 64 CPS from the background therefore, once the background was removed, the noise is clearly reduced compared to my pervious attempts and the spectrum looks better. Here they are both in counts per bin and energy per bin.
Cs137 and Am241 are always “easy” to spot, the challenge is “catching” Eu152. The 121 keV peak is more visible (there’s a clear Gaussian correlation right there, see image below), but there’s also another peak around 100 keV which I cannot identify.
Another clear correlation emerged at 344 keV (again Europium), while the peak between 400 and 500 keV is probably Cs137 compton edge. There’s an Eu152 peak in that region, but it has ten times less probability than the one at 344 keV, so probably it’s not the main thing we see there.
There’s nothing “north” of Cs137. The absence of Eu152 peak at 1408 keV was surprising to me.
Quantitative analysis shows what’s been said above.
In the end it was a good first test for version 1 of the shield. The noise is much less than before which is good.
Anyway, I am not entirely satisfied with the sample so, be prepared, there will be a fourth attempt with another one.
Today I also recorded another spectrum with the hottest sample I had the chance to test so far…more on this in the coming days.
Massimo
This weekend I tested my third Trinitite sample and it was also an opportunity to test version 1 of my shield.
The graded shield is made of an cylinder of plastic inside a cylinder of copper with lead sheets wrapped around it. The lead is Radmax sheets from United Nuclear. The sheets are 15 cm wide and 3.60 meters long (divided in four sheets) for an equivalent thickness of lead between 1.2 cm and 1.5 cm. A single sheet of lead is placed in front of the shield, creating a sort of room for the sample. This needs to be improved as well.
This is not the final version, so I won’t report about it in the shielding section yet.
Anyway, the goal is to have something that can be easily assembled, disassembled, with the chance to add or take away parts of it independently from the rest. In one word: flexibility.
Anyway, version 1 of the shield still worked not too bad. CPS from the background decreased from 256 to 64, that’s 75% less. In terms of energy the decrease was 55%, which is an indication the shield is more effective in blocking low energy rather than high energy gammas. That’s no surprise of course.
The fluorescence from the shield is clearly visible in the background spectrum.
- Background - CPS - 12 Hours - Counts x Bin - Shield V1 - 0.045 Gauss - 21-09-19.png (7.99 KiB) Viewed 10165 times
This time I had roughly 9 CPS from the sample versus 64 CPS from the background therefore, once the background was removed, the noise is clearly reduced compared to my pervious attempts and the spectrum looks better. Here they are both in counts per bin and energy per bin.
Another clear correlation emerged at 344 keV (again Europium), while the peak between 400 and 500 keV is probably Cs137 compton edge. There’s an Eu152 peak in that region, but it has ten times less probability than the one at 344 keV, so probably it’s not the main thing we see there.
There’s nothing “north” of Cs137. The absence of Eu152 peak at 1408 keV was surprising to me.
- Trinitite @Contact - 24 Hours - BG Subtraction - Counts x Bin - Shield V1 - 0.035 Gauss - 21-22 - 09-19.png (50.52 KiB) Viewed 10165 times
Anyway, I am not entirely satisfied with the sample so, be prepared, there will be a fourth attempt with another one.
Today I also recorded another spectrum with the hottest sample I had the chance to test so far…more on this in the coming days.
Massimo
