Scintillation - Science topic

It is not uncommon for certain lab supplies to be in high demand or backordered due to various reasons such as an increase in demand for certain types of research or supply chain disruptions. In such cases, it may be helpful to try reaching out to the manufacturer or distributor directly to see if they can provide any information on when the vials will be back in stock. Additionally, you can try looking for alternative suppliers or checking with local scientific supply companies to see if they have any borosilicate glass vials in stock.

Alternatively, you could consider using other types of containers for storing and drying your tissue samples. For example, you could use pre-combusted aluminum foil packets as you mentioned, or you could try using pre-combusted tin capsules or pre-combusted glass vials. It is important to ensure that the containers you use are properly combusted and clean to avoid contamination of your samples.

It is also worth noting that the type of container you use may depend on the specific requirements of your stable isotope analysis method. It is always a good idea to consult with your laboratory or the manufacturer of the stable isotope analysis equipment to ensure that the container you choose is suitable for your specific application.

Hello Christian,

I never worked with the "new" cocktail indicated by you.

But, If I was which try to undertsand the performance of the new cocktail, I start with some tests in which put in comparison the "old" cocktail with the "new" cocktail.

Use the same ratio sample: cockatil, the same total volume, same vials and same "sample": under these conditions, you could buy ethe cockatails and undertsand if the new cockatail are able to give you the same performance with the old cocktail, and then undertsand if you can perform your experiments with cheapper cost

Mattia

This was all very reassuring to read. Thank you for the responses and the links!

Thank for this interested question

Dear Faqiang Zhang thank you for posting this very interesting technical question on RG. As an inorganic chemist I'm unfortunately not an expert in this field of research. However, I just came across the following instructive lecture which might help you in your analysis:

This presentation of freely available as pdf file. Also please check the following Open Access article:

(please see attached pdf file)

Good luck with your work and please stay safe and healthy!

thank you sir on the article which helps me and gives good information on my quistion

Dear Christoph Vogl ,

please see :

and click Xe therein at the Substances line.

In the XE section there is the paper of R.E. Huffman, Y. Tanaka, J.C. Larrabee listed:

Hello Jacob,

absorption measurements (tauc plot) can give precise informations concerning the band structure of materials. You can vary energy, polarization and k-value of incident radiation.

Luminescence gives integral information. Cathodoluminescence excites electrons in a quasi free state (ionizes the material). The charges then thermalize into band states with different probabilities and recombine as a function of their different lifetimes into the ground state. Photoluminescence is more precise because the start state depends on energy, polarization and selection rules. No "inclined" transitions are possible.The end state after thermalization therefore differ from cathodoluminescence.

With Regard

R. Mitdank

Dear Hesham Yousef

At temperatures below 0 ° and above 60 °C, the light output of the NaI(Tl) scintillator significantly decreases.

The decrease in temperature is accompanied by a deterioration in the intrinsic resolution of NaI(Tl) as a result of the appearance of inhomogeneity of the light output.

To increase the efficiency of NaI(Tl), it is necessary to maintain the optimal temperature of the scintillator. In room conditions, the light output of the NaI(Tl) scintillator is maximum.

Other questions increase the efficiency of the scintillation detector ( NaI(Tl)) they relate to the change in the detector geometry and relate to the detector-photomultiplier system.

Hi Sebastián Alejandro Sarasti,

The most significant difference is the width of the photoelectric peak at 662 keV. This width occurs after gamma-ray energy is transferred to the scintillator crystal. Your simulation probably may not include this part.

The number of scintillation photons generated, when 662 keV is totally absorbed by the NaI:Tl crystal, is statistically distributed. It is also a stochastic process whether each scintillation photon is successfully detected by a photodetector (photomultiplier tube or semiconductor device) or lost.

There are two ways to improve the distribution. One simple way is to assume the energy resolution of the detector (crystal + photodetector) and perform a convolution with your results. You can fine the typical energy resolutions in literature: typically ca. 7% [*].

Another detailed method is to add, if necessary, simulation to track the behavior of the scintillation photons.

The other differences seem to be related to Compton scattering; since the NaI:Tl crystal is sealed in a package, some of the energy may be lost by Compton scattering in the package before it enters the crystal. Then, the gamma-ray energy is not 662 keV but less than 475 keV for the detector. Similarly, Compton scattering from surrounding desks, walls, and other objects may enter the crystal and increase the proportion of that component of the experimental data.

actually is no any problem to replace PMT with something else but you should remember that you need to compensate amplification PMT provide with using an additional amplifier to obtain the same one pulse feedback

أما بالنسبة للنيوترونات السريعة فإنه يفضل الكشف عنها باستخدام البروتونات المرتدة عند تشتت هذه النيوترونات على الهيدروجين . ولهذا الغرض تجهز البلورة في شكل خليط من حبيبات كبريتيد الخارصين ZnS والشمع لاحتوائه على نسبة عالية من الهيدروجين . وتعتبر هذه البلورة من أنسب البلورات للكشف عن النيوترونات السريعة .

Arif Hussain

You can Use 'csvread' command in MATLAB to read the data.

Syntax - Data = csvread('filename.ismr');

Later, you can select any column based on your requirements.

Hope this helps you.

In many media where the main effect of ionizing radiation is ionization, it is known that a small percentage of secondary electrons have enough energy to produce further ionization. They are often called "delta rays". Though not important in number, they can carry a very significant part (several 10%) of the energy lost by the primary particle (e.g. alpha particle) and are responsible for a significant part of the damage to biological tissues.

The situation is basically similar in crystals, where ionization is replaced by e-hole pair excitation. Many secondary electrons receive an energy above the threshold of e-hole production (this threshold is smaller than the ionization threshold), and the transfer of energy to e-hole pairs is often a multistep process. They do not contribue significantly to crystal damages.

Probably simulation codes can describe this in detail, but often the interest is centered on damages to the solids ,for which delta rays are not very interesting, or to the link between the total luminescence to the total energy lost by the primary particle, and this is generally established by an experimental calibration. In the case of ZnS, the intensity of the luminescence is often not analysed, and it is used as a counter of alpha particles, not a spectrometer.

Rem: It is better to use "primary" for the incoming particles, not for the electrons liberated in the medium.

Plastic scintillator response decreases with increasing energy. Plastic scintillator response is Compton, not photoelectric. See

I love the allusion to staring at lion turds and lymphomas! The problem with too much data is that one ends up with constipation if one deals with it in a linear thought structure akin to the gut

I would suggest that the key to processing data is to find a way to recognise the patterns within it. This recognition may start by being more selective about the way that the data is initially collected, but the later filtering process to recognise the patterns is just as important

I am all for the empiricism in its original use of the word " based on, concerned with, or verifiable by observation or experience rather than theory or pure logic " but theory and logic is an integral process that goes hand in hand, and is certainly useful in exploring new ways of thinking.

However all is not lost since to my mind it is the outlying results (the 10% who have absolutely no or absolutely total response) that may indicate new and fruitful areas of research. These responses that do not fit the established pattern allow one to look at things with fresh eyes

Pattern recognition rather than deductive logic is the cornerstone of clinical practice. Perhaps we can integrate more of it into theoretical research models...

Hi Molly, was the problem solved? I am having the same problem with another old scintillation counter (Wallac 1409). Thanks!

Hi! I think that use a scintillator counter would be better. H.

Thank you Manigandan Sekar for the link, but I don't need a buffer for histology experiments. Scintillation fluid this is for experiments with a radioactive label.

The energy of the gamma-quantum needed for Compton scattering is equal to the electron mass, which is approximately 0.5 MeV. The deepest K levels for very heavy atoms like Uranium is of order of 0.1 MeV, for lighter atoms it is smaller. Therefore, while considering the scattering the atomic potential is just a small correction. All electrons may be treated as free.

If there is a small correction, it is for the decrease of the cross section as the discrete electronic structure of the atom imposes only limitations.

below I attach you an explanation about how to measure the efficiency and the Efficiency calibration curve .

Well done, Raed (Baha-Ophthalmology Centre).

Mabrook, habibi.

This is simple calibration. Divide 6 mR/h by cpm. You are calibrated for that radionuclide at that particular geometry.

Hi there,

You are right : as long as the enzyme concentration used in the assay is far less than the substrate concentration, your kinetics are OK for velocity determination. And you can perfectly compare the calculated Km values.

Hi Sandor!

Thank you so much for your reply. Hoping that you are well. As you probably have guessed already the lab I mentioned was your lab that I visited some time ago to learn the GTPgammaS assay :) In my last experiment, morphine produced slightly less stimulation, but in the one before, the Emax values were identical for both drugs. I was surprised because you mentioned morphine being a partial agonist and DAMGO giving much more stimulation than 50%. Another thing is that I also get 10-times lower EC50's than I got in your lab. I know that the EC50 values are not accurate when determined in GTPgammaS assays due to the presence of sodium, but this inconsistency still worries me a bit. I don't remember which membranes I used when I visited your lab, but I think I'll try the brain regions you mentioned and see how it goes. Do you also use spinal cord homogenates? Do you see a clear distinction between the efficacy of DAMGO and morphine? 

All the best,

Anna

read this lecture:

If you see a slow down of the rise-time it is probably to do with two-photon absorption process. The light emitted usually should be proportional with the light you put in in a truly linear case. How do you detect the light coming out? The number of pulses will only have an impact if the separation of pulses is shorter than the decay time of the scintillator, otherwise you only take into account single pulse effect.

I hope this helps.

If there is "a best way" at all. Qunatification with an LSC is certainly superior to quantification with imagers. However, there is a wealth of methodic errors you can make when you use an LSC method as you vaguely describe. The measurement with the imager is more straight forward but also not without problems. As always, much depends on your equipment and experience.

If you put 180,000 cpm into a 1 ml reaction, but then withdrew 0.1 ml for the analysis, the reference for % recovery would be 18,000 cpm.

Your formula for the cholesteryl ester calculation is correct, but only if the recovery of both substrate and product are equal.

The company has given you the the molar concentration of P-33.

Usually they provide information as P-33 in X molar H3PO4. You need the molar concentration of H3PO4. The stable H3PO4 is phosphate concentration you need. When you calculate the uptake it will be the stable phosphate. Typically the supplier describes the product as

Phosphorus-33 Radionuclide, 25mCi (925MBq), Specific Activity: 8500-9120Ci (314-337TBq)/mMole, Orthophosphoric Acid in Water, Concentration:>500mCi/mL

You want the specific activity as X Ci/mMole.

Dr Deka  raised a very good point ,  narrow genetic base of commercial crops in arid regions is perhaps the most pivotal towards lower productivity levels. Unfortunately , expanding aridity coupled  with increasing menace of soil salinity is adding further  fuel to the fire , with the result, challenges to sustain   crop production have multiplied by many dimensions. Abhishek  , you added some very pertinent links , worth reading all of them .

You can use a transient recorder to record and evaluate single pulses, see link. There are cards for PCs, and depending on what exactly you need, these are not very expensive anymore.

Dear Prof. Ghal-Eh,

we can easily get around the range argument by assuming that the electrons or HCPs  are completely stopped in the scintillator. Then let us assume that the incident particles carry identical amounts of energy into the scintillator. Since they are eventually completely stopped they deposit identical amounts of energy into the scintillator. Fluorescence requires that electrons in the scintillating material (in your example PPO) get excited. For each excitation you need at least the excitation energy. On the average there is a certain amount of energy loss of the incident particle necessary to produce an excitation and a resulting photon. If this were all that can happen you just divide the kinetic energy of the incident particle by that average energy loss and you get the average number of photons per incident particle: identical numbers  whether it is an electron or a heavy charged particle.

Now, as I wrote,only a small fraction of the kinetic energy lost by particles in a scintillator is converted to photon production. Most of the energy lost is dissipated without radiation emission. So, electron excitation is not all that can happen. There are also collisions with kinetic energy transfer to atoms/molecules which produces heat.

The dissipation of energy by non-radiative processes  is much more likely for HCP than for electrons. HCP spend most of their energy to heat the material (in your example all three components of the liquid scintillator) and little is left for electronic excitation. Electrons can transfer energy into electronic exciation much more efficiently.

The physical picture behind this is: by the incident particle kinetic energy has to be transferred to a bound electron in the scintillating material to finally produce a photon. An incident electron can ultimately transfer all its energy to another electron in one collision (colliding particles of equal mass in a head-on collision). A heavy particle  can only transfer a fraction of its kinetic energy to an electron just because of kinematic reasons. In a head-on collision of two particles with masses m1 and m2 the (maximum) energy transfer is 4m1 m2 Ekin/ (m1+m2)^2. For incident electrons we have m1=m2=me and the full kinetic energy Ekin can be transferred. If we assume an incident alpha particle the maximum energy that can be transferred to an electron in one collision is approximately Ekin/2000. Hence much of the energy loss of HCP goes into collisions with similarly heavy constituents in the scintillator and these are the atoms that get kinetic energy which means the scintillator is heated. All these arguments are particularly valid at low kinetic energies where nuclear stopping of HCP prevails.

The same arguemnts are basically responsible for the size of atomic excitation cross sections. At kinetic energies of approximately two to  three times the threshold energy electrons have their maximum excitation cross section. At these (low) energies the excitation cross sections  of HCP can almost be negelcted compared to those of the electrons (smaller by many orders of magnitude).

I hope this explanation is sufficient to answer your original question.

Sorry, I just saw the reply. Thank you for the suggestion. It does look like XP 2020. I will try and let you know. Also, the whole PMT and BaF2 seems to be integrated with a polymer like thing. The whole PMT+scintillator is inside a cylinder (probably mu metal) and the gap (between the PMT and the mu metal cylinder) is filled with a polymer. I was wondering if its possible to remove that polymer somehow. The reason is that I want to dissassemble the whole thing and repply the optical glue. Please let me know if you have experience for such taking apart of detectors.

thanks

saurabh

You can use SRIM program. It is very easy to use.

It will depend on the dye concentration. But sorry,  don't know of any measurements either. Have you found an answer? If you are going to do some measurements yourself we might be interested in a collaboration!

I´m not sure with background, because in every background spectrum you see at least some hints to peaks from the natural radiation which can easily been distinguished from noise. And especially the sharp step at the higher end of your curve looks  like a defect.

You have to take a Calibrated radioactive source (you can purchase one) and compare the radioactivity of your Metal ions with that of the radioactive source. This may be done by placing each of the two sources in an identical geometry and compare the intensities of the two resulting spectra using your NaI(Tl) detector. 

If you can specify what metal ions you have in mind, then one can think of the best radioactive source which will yield the best results for your specific problem.

In order to receive suggestions to the problems you are seeing, you should first define the following:

1) region of interest you are using to assess your instrument response

2) volume and reagent of your Am source added to what volume of scintillation cocktail.  E.g., is a portion of your aqueous solution spike insoluble in the cocktail volume and settling to the bottom over time?

3) how far above the instrument background are your samples?

4) by what means are your standards' activities quantified or externally calibrated?

5) what are you seeing on the pulse height spectra?

This information should aide in getting answers to your questions. 

Yes, it is possible to use detectors ranging from 0D point counters to 1D linear position sensitive detectors to the good old photographic film (an extinct species in the XRD lab these days) to modern "Back to the Future" 2D detectors. Depends on how motivated and open minded one is.

No matter what tools you use, in simple English, the basics ("protocol") are still the same.

1. Find the diffractometer axis (z-axis) and make sure it is normal to the diffractometer "equatorial plane". Basic!

2. Make sure the incident beam is parallel (if line source) to the diffractometer axis and the axis bisects the incident beam (hopefully rectangular or near so).

3. Position the sample surface parallel and collinear to the diffractometer axis. Adjust Omega (0 deg.), Phi, Chi/Psi to observe both incident beam and the XRR beam (Two beams! "Split beam"!). 

4. Perform 2Theta-Omega scan while recording the data in 2D.

See images attached. Using a conventional 0D scintillation/point detector for this task is tantamount to "walking in a busy shopping mall with a blindfold and handicapped with only a pinhole to look through". You could do it, slowly & carefully. Others do so even now (for the past century) on a daily basis. However, I suggest using a combo of 0D counter and film (commandeer it from a local "old time" dentist) in order to optimize the sample for the maximum signal to noise ratio. Then take the final quantitative observation with the 0D, that you certainly have, using the smallest of slits possible. Good luck!

A Better, Faster, Smarter, Modern Way! Here's the "lead horse view" using a real time 2D Bragg XRD Microscope attachment (cost effective, state-of-the-art US technology) mounted on a Bruker or Panalytical Diffractometer (or other). It took us about 5 minutes including alignment to acquire 5000+ 800x800 pixels frames. Spatial resolution 29um. Angular (reciprocal space) resolution 0.75 Arcsec. SDD - Sample to detector distance of 145 mm. The 3D data volume nearly 3GB. Using the conventional tools you'll turn into a Rip Van Winkle duplicating these results :-)

(https://www.flickr.com/photos/85210325@N04/11343736043/in/set-72157645018820696) 

I´ll try a quick answer. Radioluminescence is caused by irradiation of certain materials with radioactive particles and photons. This radioluminescence can be prompt, called fluorescence, or delayed, called phosphorescence. Distinctions are the processes in the solid. Primarily no statement to delay.

Scintillation is the prompt emission of "visible" light of irradiated substances, the scintillators. So if you want, scintillations are a subgroup of radioluminescence.

Dear Sir,

At first you may employ a fast scintillator such as LaBr3:Ce (16 ns) with light yield ~ 90 MeV^-1, LuAlO3:Ce (LuAP) (21 ns) & light yield ~ 8000 MeV-1, or, just the well established detector Lu2SiO5:Ce (LSO) or LYSO.

Good semiconductor detectors are CZTs.

I do not know the compatibility issues with your system. However, everything could be put together to work. If the physics remain unaltered.

very thanks.

BaF2 doping Cd very  increased  scintillation light yield after electron radiation.I think in this paper used doping BaF2 not pure...

Thanks Rakesh! I will have a look...

When you buy a radioactive compound usally is very hot and at a very low concentration (something micromolar). Usually you need millimolar concentration of substrate, so you prepare the substrate solution at the  concentration you need then you add some of the radioactive compound (you may calcyulate the amount utilizing the specific radioactivity indicated by the producer). Then you put a know amount of nanomoles of you mixture in the counter and you will obtain the CPM (count per minutes) , if you divide by the number of nanomoles you put in the vial you will obtain specific radioactivity in terms of CPM/ nmol. Now, depending on your protocol you should separate the radioactive product from the radioactive substrates and you need to have the reaction mixture at 0 time and after 5 minutes. The counter will tell you the radioactivity, at the beginning and at the end of the reaction, that was incorporated in our product, if you divide the CPM obtained from the counter by the specific activity calculated as described above, you will obtain the nanomol of your product generated in 5 minutes divide by 5 and multiply by the dilution operated to perform the assay you will obtain the nanomoles formed per minute which are the milliunits per ml in your enzyme preparation.. If you know the amount of protein in the mixture you can also obtain the specific activity. I hope that this will be of some help to you

Dosimetry concerns. Obtain a dose meter and measure the dose rates for the local background, leakage at the surface of the source holder, and for the primary beam.  Compare measured dose rates against limits for public exposure (hint 1 mSv over 365 days) and for radiation workers (hint 20 mSv averaged over 5 working years, each is 50 weeks times 5 days of 8 hours). The primary beam should be directed towards a suitable beam stop.

To check the geometry, consider the single event rate recorded by each detector. Try to increase this by adjusting one geometrical parameter at a time (distance, collimation, x/y allignment etc). A large collimator increases the event rate at  the cost of degraded energy resolution,

Coincidence detection allows the MCA to measure the energy of the recoil electron. The coincidence rate is small fraction of the singles rates, so ensure these are as large as possible. In addition, the experiment requires the delay line NIM module, and this be adjusted so that the pulses reach the MCA at the same time. Remember that a delay of zero, removes the true coincidence events leaving only the randoms. Use a dual channel oscilloscope to monitor both pulses, check their polarity, amplitude and timing characteristics. Be systematic and check each step of the counting chain for both channels.

Read the manual for your MCA to understand how it can be used for gating or coincidence detection.

Lastly, true coincidence detection rates are small, requiring a few minutes or longer to gather enough data to separate the signal from the background noise of random coincidences.

Good luck.

Strange. I think there should be some parameter out of your control. How does it look like with reproducibility of results? Can you obtain the same conditions several times in a row with the same efficiency?

Sorry, I accidentally added another article. Here is article about the nanoscintillator material.

You can see this paper Environ. Sci. Technol. 2011, 45, 3680–3686 which reported the synthesis of Pr3+ activated Y2SiO5. It converts visible light into UVC.