June 2020. After some time searching around on the net for a scintillation material that I can shape at home, I’ve found a Dutch guy called Luuk that have some CsI(Na) crystals avaiable for free to make experiments. A couple of emails with him and voilà…. I’ve just received a nice piece of raw CsI(Na) crystal from him (Scionix?). Thank you Luuk!!! Sadly the crystal quickly cracked because, probably, thermal shock during transport. Summer is summer and postal services are not famous for the good handling of the crystals.
I’ve soon realized, carefully looking at the fractures, that I can cut out the intact middle section of it. That part will be “enclosed” with some PTFE white ribbon as reflecting layer and coupled on a fece with a PMT to make spectroscopy tests.
I’ve cutted out the intact part using a small arc saw made for modellism work with very fine teeths. It’s a good idea to handle the crystal with gloves to be sure to not pollute it.
The “rough” grinding of the crystal faces was made with 400 size sandpaper till I’ve get an almost rectangular shaped crystal.
Even with this rought grinding of the crystal faces, it coupled to a FEU85 PMT gives me 8% FWHM. The FEU85 used have 7% PHR at Cs137 peak.
I’ve finally decided to take a spectra of my pitchblende sample to see how does it perform and I’ve got a very nice result. I will try polish it even better and compare the results to see how much the crystal level of polishing affects it’s FWHM.
I’ve finally tested my brand new 40x40mm NaI(Tl) crystal from OST making with it a new probe for my lab. This time I’ve tested epoxy glue for assembly. The dynode voltage divider is home made via a simple toner transfert/etching process.
First thing to do is to glue the crystal inside it’s aluminium housing with some epoxy glue. I’ve simply used a 46mm internal diameter, 50mm lengt aluminium pipe as coupling pipe. It’s external dimensions are 50mm and it will fit the inner diameter of the main probe pipe.
The crystal outer diameter is 45mm, the 1mm total clearance between coupling pipe and the crystal is filled with epoxy by placing the glue around the crystal body and sliding it into position. Next thing is to couple the crystal with the PMT and block in position with some tape.
Now some more epoxy….
And then I’ve slided the assembly inside the body pipe until it will block against the blue tape. As you can see the yellow and blue tape are simple a note of color and the blue one is used as sliding-stop reference mark.
After few minutes the glue will be hard enough to test the assembly. I’ve added a BNC terminated cable soldering the cable into the voltage divider pads, needed 1000V from my USB PMT Adapter and placed a piece of uraninite under it to take a spectra.
A very nice result!!!! Around 8% FWHM but this could be improved because the PMT was exposed to light during assembly and it’s noisy so it will take a day to rest. Today I’ve finally verified it with Cs137
7,8% FWHM but the software is not catching the correct peak position. I can expect a 0,5% FWHM error. This means 7,3% FWHM of the crystal. Not bad, not bad at all!!!
Some months ago I’ve bought a trinitite sand from United Nuclear. They’re website description say:
Early in the morning on July 16th, 1945, the first Atomic Bomb was detonated at the Trinity test site in the New Mexico desert. The nuclear explosion produced a blast equivalent of 18,000 tons of TNT and a ½ mile diameter fireball – with a temperature over 10 million degrees Fahrenheit, far hotter than the surface of the Sun. The intense heat melted the New Mexico desert sand into a light green, glass-like substance which was later named “Trinitite”. The resulting crater lined with Trinitite was buried for security reasons not long after the explosion.
In a couple of weeks I’ve received this vial full of Trinitite grains.
I’ve tested it under UV light but this material not present any fluorescence. The second test is obtain a gamma-ray spectrum from it in order to see if it’s a fake or not. I’ve used my 30×40 NaI(Tl).
The scintillation crytal have a center well made for vials. In this way low energy gamma rays are collected by the crystal at the highest efficency. After several hours of analysis the result spectrum shows clarely Americium and Cesium isotopes made by neutron activation during the bomb explosion. This sand is real nuclear melted sand!!!
The first left peak is Americium and the small peak at 609keV are Bismuth and Cesium isotopes. My crystal have good sensibility but an FWHM of 11% is not enought to extract any fine detail.
UPDATE 10 October 2019
I’ve made this test again with a 63x63mm NaI(Tl) scintillation probe enclosed into a 50kg componible lead shield. The result is amazing!!!
Americium, Europium, Cesium and Potassium isotopes from the neutron activation are quiet recognizable.
My friend Stanislav Prytuliak had made a test of a trinitite sample bought on eBay using the HPGe spectrometer at Karlsrhue university.
The following picture is Copyright by Stanislav Prytuliak (C) 2019 and couldn’t be reproduced. The following picture is published by his permission.
Final conclusion? The trinitite sample is not fake!
I’ve bought this 10x10x30mm CsI undoped crystal scintillator from Moscow. It’s looking great! Let we see what Saint Gobain tells about this type of crystal scintillator material csi-pure-material-data-sheet_69770 :
“Cesium Iodide is a material with high γ-ray stopping power due to its relative high density and atomic number. Undoped CsI, being an intrinsic scintillator, has very different scintillation proper-ties from the more widely used CsI(Tl) or CsI(Na) activated by Tl or Na respectively.Undoped CsI is mainly used in physics experiments because of its combination of fast timing and relatively high density. Its scintillation is heavily quenched at room temperature, and cooling improves the light output.CsI is slightly hygroscopic”
I’ve tested it under UV light to see if it’s fluorescent but… no way! It doesn’t lights up under UV.
I always desired to reproduce some experiments of first pioneers of radioactivity.
Bequerel exposing some photographic plates to the radioactivity of some uranium rocks obtained some foggy image of the radioactive ore. This very simple experiment gived him the “spark” that let him discovery the radioactivity.
How to reproduce it? Simply! I’ve some 4×5″ photographic chassis and some sheet film from Foma czech analog film factory.
The Foma 100ISO film is what I’m using on my large photography analog cameras.
I’ve exposed this film for 24h to the radioactivity of uraninite, autunite and to the alpha rays of an Americium alpha emitter capsule and also added a piece of image intensifying film from an old x-ray casette to a third chassis and I’ve re-done the experiment hoping to see the screen effectiveness in inproving exposure of the sheet film.
Then, I’ve developed and scanned it.
The result confirm at 100% that the radioactivity from autunite and uraninite could expose the sheet film. The image intensify screen confirm it’s efficency too. I must punctualize that I’ve made two errors inserting or extracting sheet film from the chassis because I’ve exposed it to light for about 40% of the surface. Neverthless I’ve obtained nice results. The Americium alpha rays doesn’t reached the sheet film at all, blocked by the 1mm plastic enclosure and the 2mm inner space between chassis “volet” and fim.
For Beta counting and Beta spectroscopy parpuses, Antracene (C14H10) an organic scintillator material is widely used. It’s light output yeld is the highest of the organic scintillator materials family.
I’ve bought a russian crystal that have a removable alluminium cap. Under the cap there is the crystal. It’s front face is alluminized because alluminium act as a screen for Alpha particles. With alluminium cap on it still detects hard Beta’s.
Bundeswehr radiation dosimeter, tactical, set 0065 B
For about 25€ I’ve find this nice militar dosimeter set. It comes from german army and it’s a nice take for the money, the box is made with wood and is methal reinforced. It’s small in size and not too much heavy. It’s looks extremly well made and solid. I’ve bought it on eBay from a military surplus seller; this item is very easy to find searching for “BW Strahlendosimeter, taktisch, Satz 0065 B”
Inside the box there is a yellow plastic charger with a light bulb that is used to read/reset to zero the dosimeter, 6 high rate dosimeters and 6 lower rate dosimeters.
This type of dosimeters are “quartz fiber dosimeter”, here you can find more info Wikipedia
The lower rate dosimeters have the range 0/50 roetgens, the high rate 0/600 roetgens.
Here is what you could see into such dosimeters. The sensibility of such devices is soo low that you hardly will see a move of the line along de scale except when the internal capacitor is discharged by self losses and need to be re-zeroed by the charger.