Dear Saha,

the choice for the activity A of your source should be roughly adapted to the dose rate H' you aim at your TLD detector when in operation.

You certainly know that there is the following relation :

H' = A * Gamma/r² with A the activity of your radio-active source (given in units of Bq), r the distance to the source, and Gamma the Gamma dose rate constant of the gamma emitter.

Gamma has the main units [Sv*m²/(h*Bq)]. Numbers of the Gamma constant can be found for example in the following link:

http://nuclearsafety.gc.ca/pubs_catalogue/uploads/Radionuclide-Information-Booklet-2016-eng.pdf

For the case of Cs137 / B we have at page 31):

Gamma Cs137/Ba = 7,789*10-5mSv*m²/(h* MBq)

For conversion of Bq in Ci (as you asked for) you may use: 1Bq=2,7*10-11Ci.

http://www.endmemo.com/sconvert/bqci.php

Fortunately you can balance the activity A against r² in order to find the activity of your source, which can be provided by your local supplier.

Final remark:

Cs 137 mainly emits at about 662keV. However this photon energy is far away from your application (cardiac angiography). So I would recomment other sources such as Am 241 (at about 60keV) or Co 57 at 122/136 keV.;

Am241 is long living (432 a) but unfortunately Co 57 has got a half life time of about 272 d.

thank you dr. Martens for your thorough answer , the X-ray energy mean in cardiac angiography is 80-90 Kev and for cardiac angioplasty is about 150 kev so I think Am has low energy for calibrating TLds that are supposed to detect X rays in ranges mentioned above .

so I guess i have only one option with is Co 57?

Dear Sahar,

I think your numbers given above relate to the tube voltage setting which means that the maximum x-ray photon energies are around 80-90keV and 150keV for the two application cases.

The rough estimate of the mean photon energies Emean is found at about 2/3 of kV numbers. So your mean photon energies are around 60keV (=2/3*(~90)) and around 100keV ( =2/3*150) respectively.

60keV ( i.e. Am241) is a good compromise for both applications.

However even Co57 (~120keV) will do the job and is far better than Cs137 (~660keV).

You will get both types of sources as sealed ones. So the handling is the same for both types.

Thus you should look which of these radioactice sources is easier to acquire.

Good luck.

Yes that’s right

thank you very much 🙏🏻

Additional remark:

Gamma dose constants of Co57 and Am241 can be found at the pages 14 and 34 of the first link presented above.

But please take care that for example for the case of Am241 at the line:

'Gamma ray effective dose rate at 1 m: 4,347E-06 mSv/h per MBq'

you have to interpret the gamma constant as:

GammaAm241= 4,347E-06 mSv*m²/(h *MBq)' for using in

H' = A * GammaAm241 /r²

(the m² was skipped due to the setting of the dose rate at r=1m in the above link)

For the case of Co 57 you have to proceed in a similar way:

'Gamma ray effective dose rate at 1 m: 1,808E-05 mSv/h per MBq'

---> GammaCo57=1,808E-05 mSv*m²/(h *MBq)

Good luck

thank you for your sincier help :)