I love my Radiacode 103. I consider it an essential part of my EDC (even though I don't really consider myself an EDC type of guy). I'm interested in being aware of how much ionizing radiation I'm exposed to on a daily basis.

(Sitting at my desk I'm being hit with 0.04μSv/hr at ~3 clicks/second)

One thing that had confused me are the little alarm symbols that appear on the screen of the device. I constantly had to look them up to remember which symbol means what.

Σ, γ, and S^-1. (You'll find a cheat-sheet at the bottom of this page)

So rather than have to load up the manual in a PDF reader every time I get an alarm, I decided I'd do a little write-up for my first actual blog post on this website.

The Radiacode 103 is a Gamma Particle Scintillation Detector. It uses a Cesium Iodide crystal to detect high energy photons incredibly accurately for such a small, inexpensive (relatively) device.

Remember that Cesium Iodide detectors are susceptible to static discharge.

it won't hurt the device, but it can result in false-positives. Check the alarm history in the app to verify if the alarm is an actual positive or not. If the chart has a single sharp spike, there's a very high chance it's a result of static buildup affecting the crystal.

A Cesium Iodide Crystal during active scintillation, notice the faint blue-white glow: MyName (A1000) on Wikipedia. licensed under creativecommons.org/licenses/by-sa/3.0/

Cesium Iodide is also water soluble, but the crystal is contained in a hermetic metal canister in the device and should maintain a water-tight seal even if the device is accidentally dropped in water. (The radiacode is NOT waterproof and should be treated with the care of any other scientific instrument.)

The radiacode 102, 103, and 110 all use CsI crystals. the 103G uses a GAGG (Gadolinium Aluminum Gallium Garnet) Crystal. It is non-hygroscopic.

Also, your count-rate with the 110 model may be higher than your peers with 102 and 103s, this is only because the crystal is significantly larger and therefore has more surface-area to detect particles.

Another thing to take note of is that Radiacode devices only detect gamma spectrum particles^[1]

That being said, alpha particles, while abundant; are very large, heavy particles. Most run out of energy and dissipate within a foot of air at normal atmospheric pressure.

Count Rate (S^-1)

Count rate is generally used as a radiation "metal-detector" good for finding hotspots while sweeping an area. Higher count-rate? Something gamma-spectrum active is nearby.

Dose and dose rate get a little more into the weeds.

Dose (Σ)

Remember from math class, Sigma means "sum"!

Dose is a long-term measure of previous radiation exposure, commonly measured in μSv/hr^[2]. This is to be used as a "sum" of the radiation the device (and by extension, you) have been exposed to over time. This timeframe can be customized in the radiacode app, under the "Dose" tab. It defaults to one month to the current date.

Dose Rate (γ)

lowercase gamma, A.K.A. the symbol used for gamma radiation!

Dose rate is a measure of "How bad is it right now?" Dose rate comes in handy when you are knowingly in an irradiated area and would like to know how much gamma activity is hitting you currently. If the dose rate alarm is triggered it might be a good idea to move to a different location. It tells you that the immediate dose in the area is high, but it may not be high enough to set off your long-term dose alarm.

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1. Some alpha-emiiting isotopes decay into gamma-emitting daughter isotopes, these daughter isotopes will be detected and can aid in characterizing their alpha-emitting parents. ↩︎

2. μSv/hr (micro sievert per hour) is a biologically adjusted measure of radiation dosage. A μSv is 1/1000^th of a Sievert. A Sievert is described as 0.01 rem. Which is to say 1 μSv is equal to 0.0001 rem (1/10000^th of a rem) ↩︎

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Count Rate Alarms

S^-1_ : Count Rate Alarm 1
S^-1‗ : Count Rate Alarm 2
S^-1≡ : Count Rate Alarm Over Scale

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Dose Alarms

Σ_ : Dose Alarm 1
Σ‗ : Dose Alarm 2
Σ≡ : Dose Alarm Over Scale

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Dose Rate Alarms

γ_ : Dose Rate Alarm 1
γ‗ : Dose Rate Alarm 2
γ≡ : Dose Rate Alarm Over Scale