Stilbene

Stilbene is an organic solid scintillator material used for fast neutron detection.

Characteristics:

  • Direct detection of fast neutrons
    • Stilbene is highly sensitive to fast neutrons, hence they do not need to be moderated to lower energies to be detected
    • Stilbene takes advantage of the low background of fast neutrons for low-noise measurements
    • Detection of unmoderated neutrons preserves information about neutron trajectories and energies

 

  • Excellent discrimination between neutrons and gamma rays
    • Facilitates counting fast neutrons without false positives from gamma rays
    • Permits use of lower energy thresholds than liquid scintillators

 

  • Safe and Easy to Handle and Transport
    • Solid, non-hygroscopic, not flammable, not hazardous
    • Unpackaged stilbene is stable
    • Avoids the transportation, storage, and handling concerns of many liquid organic scintillators

CsI(Na) cutted and polished at home

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.

 

OST 40x40mm NaI(Tl)

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!!!

CsI undoped

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”

Pure CsI crystal

I’ve tested it under UV light to see if it’s fluorescent but… no way! It doesn’t lights up under UV.

CsI under UV light

Anthracene

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.

Crystal with it’s removable cap

 

My crystal is not clear… maybe is damaged?
It’s strong UV fluorescence

 

LYSO crystal scintillators

Hi! Some time ago I’ve bought some 4x4x22mm LYSO Crystals to make a scintillation probe or just to test they.

From the manufacture:

LYSO crystal is an ideal generation scintillator crystal. LYSO (Cerium-doped Lutetium Yttrium Orthosilicate). LYSO crystal has the advantages of high light output and density, quick decay time, excellent energy resolution and low cost. These properties make LYSO an ideal candidate for a range of ray detection applications in nuclear physics and nuclear medicine, which require higher, improved timing resolution and superior energy resolution. “

The seller on ebay is the well know: “The Rad Lab”. For 12$ I’ve received 2 crystals. They are for sure intended to use into a proton emission tomography machine “PET”. More docs from Saint Gobain:

LYSO datasheet  NextGen LYSO

 

The Rad Lab LYSO Crystals

Some more info about this type of crystal:

 

Crystals in their package

I think this crystals are from a PET machine who was scrapped… but hey, they works great! Take a look at how they react when are exposed to some UV light.

LYSO crystals under UV light

This type of scintillator crystal is a bit radioactive because of Lu176 inside it. That’s makes it a nice calibration source for my spectrometer,

I’ve made this gamma ray spectrum of my LYSO crystals. To make it I’ve used PMT R6095 + 30x30mm NaI(Ti) scintillator at 8% FWHM. Peaks of Lu176 at 201.8keV and 306.8keV

LYSO: this is a recording in a XML file of this spectrum. To be used with BecqMoni2011 software.

LYSO gamma ray spectrum

NaI(Tl) Crystal scintillator

This type of scintillator material is the best one that an hobbist could afford. At the moment NaI(Tl) crystals are easy to find on eBay from russian or ukrainian sellers. Take care that NaI(Tl) are highly higroscopic and if they absorb too much water they turn color to yellow than brown and finaly their light output drop to unusable level. As the majority of the scintillation materials, they are used coupled with a photomultiplier tube for Gamma Spectroscopy.

Gamma Spectroscopy probe

Some pics of my gamma-spectrometer crystal + PMT probe.

A 25mm diameter NaI(Tl) crystal mounted on my gamma-spectrometer probe.
NaI(Tl) + PMT inside an alluminium enlosure + Madexp USB PMT adapter measuring a radioactive source
A 10mm NaI(Tl) crystal with it’s alluminium enclosure, packaging and datasheet
NaI(Tl) crystal optical window

BC408 BC412 Plastic scintillators from Bicron

Some weeks ago I’ve bought from an US eBayer some cilindrical shaped plastic scintillators. From wikipedia “A scintillator is a material that exhibits scintillation — the property of luminescence,[1] when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate”. This means that you can make a very  sensible radiation counter using a scintillation material coupled with a PMT to detect his ligh pulses.

Scintillation probe
Gamma Spectroscopy / scintillation probe

One is 1” diameter made of BC408, the other is 1-1/2″ of BC412.

Bc408-412

This type of scintillators are very easy to use and cople to a photomultiplier tube, they just need some silicone coupling gel and a proper light tight enclosure to work. I’ve bought some otical coupling silicone too.

Optical coupling silicone

A simple way to determine that this pieces of plastic will work is to test with some UV light. If they are sensible to radiations they are sensible to UV too.

Some tech info about this type of plastic scintillators.

Datasheet

Here you can download the complete datasheet: sgc-bc400-404-408-412-416-data-sheet