Low sodium salt(K40) Geiger Counter/Spectrometry

Characteristics of low sodium salt, Yasashio

"Yasashio" is dietary salt with reduced sodium.
Dietary salt normally consists of Sodium Chloride (NaCl), but Low sodium salts, such as Yasashio, have less sodium and more potassium(Kalium/K) instead.
As potassium (Kalium/K) naturally contains 0.0117% of radioactive K40, and while potassium is commonly contained in various foods, low sodium salt has more potassium than others, long measurement (2 hours for sample picture) of 1kg low sodium salt closely attached to iMetry shows K40 peak spectrum.

K40 has its spectrum peak at 1460keV.
Yasashio (approx. 1kg) K40 spectrum
Idaho National Laboratory
yasashio.JPG K40_spectrum.png

Low sodium salt (Yasashio) spectrum with iMetry

Linear Logarithmic
K40_liner.PNG K40_log.PNG

Amount of K40 contained in Yasashio is so tiny, that spectrum peak is hardly recognizable in linear scale. In this case, you have to check with logarithmic scale.
iMetry's basic spectrometry feature has lower resolution compared to professional equipments, so spectrum peak (1460keV in K40) appears duller and wider, still characteristic peak can be observed on the right side of the graph. You may see difference compared with Cs137 or Ba133 spectra.
In addition, iMetry shows peak at 1600keV while literature based K40 peak spectrum is 1460keV. Being a basic spectrometer, iMetry tries linear interpolation of detected energy amount and keV for rough indication, gap between 1460keV and 1600keV may come from individual characteristic of the scintillator, used in iMetry's radiation detector.
So when reviewing obtained spectrum, use iMetry's keV values only as rough indicator, try catching overall characteristic of the spectrum.

Adding a new energy calibration point with K40

iMetry is already calibrated with Cs137 and Ba133 before shipping, but let's add a 1460keV energy calibration point with widely available low sodium salt and its K40 spectrum peak.
When calibration point is added, K40 spectrum peak comes around 1460keV, as shown below.

  • 最終更新:2013-06-14 12:52:20