SARAD Thoron-Scout User manual

SARAD GmbH Thoron-Scout
Manual_ThoronScout_EN_02-07-15.doc
1
User Manual
Thoron-Scout
Version 06/2015
SARAD GmbH Tel.: ++49 (0)351 / 6580712
Wiesbadener Straße 10 FAX: ++49 (0)351 / 6580718
D-01159 Dresden e-mail: [e-mail]
GERMANY Internet: www.sarad.de

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CONTENT
IMPORTANT HINT 3
THEORY OF OPERATION 3
OPERATING THE INSTRUMENT 4
G ENERAL 4
F RONT PANEL ELEMENTS 4
P OWER SUPPLY 5
C ARRYING OUT A MEASUREMENT 6
Adjustment of the sampling interval 7
O PERATION M ODES 7
Pump 8
Alarm 8
Fast/Slow Mode 8
Sniffing 8
D ATA H ANDLING 8
Data Storage 8
Data transfer (RS232 and USB interface) 8
STATISTICAL ERROR (FOR NON-MATHEMATICIANS) 9
E RROR P REDICTION 9
I S AN OBSERVED CONCENTRATION CHANGE STATISTICAL SIGNIFICANT OR NOT ? 10
D ETECTION L IMIT 10
TECHNICAL DATA 12
CAUTION 12

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Important Hint
The determination of the activity concentration of Radon and Thoron is always a radiometric
measurement, meaning a counting experiment. This causes a number of specific
circumstances which have to be taken in consideration by the one who is carrying out this
task. Only the knowledge of those particularities allows the correct set-up of a test and
avoids misinterpretations of the achieved results.
Please read carefully the next chapters “Theory of Operation” and “Statistical Error” to
become familiar with this kind of radiometric measurements.
Theory of Operation
The Radon (Rn-222) gas concentration will be measured by the short living daughter
products, generated by the Radon decay inside a measurement chamber. Directly after the
decay, the remaining Po-218 nuclei becomes charged positively for a short period, because
some shell electrons are scattered away by the emitted alpha particle. Those ions are
collected by the electrical field forces on the surface of a semiconductor detector. The
number of collected Po-218 ions is proportional to the Radon gas concentration inside the
chamber.
Po-218 itself decays with a half life time of only 3.05 Minutes and about 50% (particles
emitted towards the detector surface) of all decays will be registered by the detector.
The equilibrium between the Radon decay rate and Po-218 detector activity is given after
about 5 half life times, say 15 Minutes. This time span defines the minimum achievable
response time to a Radon concentration step.
Now, the decay chain is continued by the both beta emitters Pb-214 and Bi-214 followed by
another alpha emitter, the Po-214. That means, each Po-218 decay causes one more
detectable decay by the Po-214 which is delayed about 3 hours because of the superposed
half life times of those nuclides. The emission energies of Po-218 and Po-214 are different
and therefore it is possible to separate both nuclides from each other by alpha spectroscopy.
The Thoron-Scout offers two calculation modes for the Radon concentration, one (Slow)
includes both, Po-218 and Po-214 decays and the other one includes Po-218 only (Fast).
The advantage of the “Fast” mode is the quick response to concentration changes while the
“Slow” mode gives sensitivity twice as high compared with the fast mode. The higher
sensitivity reduces the statistical error of a measurement which depends on the number of
counted decay events only. The user should select the calculation mode carefully with
respect to the application specific requirements (see next chapter).
In case of Thoron (Rn-220), the direct daughter product Po-216 (which also underlies the
ionisation process) is used to calculate the Thoron activity concentration. The half life of Po-
216 is less than 1s and therefore the equilibrium state between gas concentration and
collected activity on the detector is present immediately.
The half life of the Po-216 decay products Pb-212 (beta) and Pb-212/Bi-212 (alpha) are too
long to use them for Thoron measurement. The single nuclides of the Thoron decay chain
will be also separated by alpha spectroscopy.

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Operating the Instrument
General
The new Thoron-Scout is a versatile, easy to use and state-of-the-art instrument focussed on
the detection of Thoron (Rn-220) and Radon (Rn-222) in the ambient air. The required fast
exchange rate of sampled air is realized by a highly permeable chamber placed outside the
instruments enclosure. The relative Thoron sensitivity is comparable with the one of pump
based instruments.
Beside the activity concentration of Thoron and Radon, air temperature, relative humidity and
barometric pressure will be determined and saved to a non-volatile circular memory (first in –
first out). Up to 2000 chronological data sets will be available for data transfer to PC including
alpha spectrums. An internal real time clock ensures a correct time regime, a tamper lock
indicates dislocation during the measurement. A display with backlight informs about the
actual readings.
Neither mechanical parts like membrane pumps nor an external power supply are required.
Therefore, use and exposition at home or at workplace is possible without any disturbance. A
total duration of measurement of up to four weeks with continuous data recording is possible.
Due to its small dimensions and little weight, the Thoron-Scout can be shipped by mail to the
place of interest/measurement without any additional man-power required for installation or
start-up of an analysis – even untrained staff is able to start a measurement.
Entire part of delivery will be comfortable software for data read out and graph presentation,
dose assessment and easy data backup.
•Read out of measurement data and adjustment of device parameter
•Interactive graphic display with zoom and pan
•Automatic backup of measurement data
•Selective export and conversion of customised time periods to text files for additional
tasks (like import to EXCEL)
Front panel elements

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Power supply
Power supply of Thoron-Scout is realised by two D size (Mono) batteries (also rechargeable).
To open the battery slot, screw out the cover anticlockwise using a screw driver or a coin.
Please pay special attention to the correct polarity of the batteries when inserted. The
positive pole needs to be contacted to the front panel.
Change both batteries at the same time as differing charging levels may lead to failures. Use
always batteries of the same type.
Close the battery slot by screwing clockwise for 45°. Ensure a tight sealing of the cover.
The Thoron-Scout offers an external DC input to supply the instrument by an AC/DC mains
power adapter.
ATTENTION: Connect the AC/DC adapter only if batteries had been inserted before.
Never use the instrument without batteries even if it is supplied by an external voltage,
otherwise malfunction cannot be excluded.
If the AC/DC adapter is connected, the batteries will not be discharged. They will work as a
buffer in case of mains power interruption. If rechargeable batteries are inserted, the
batteries have to be recharged from time to time because of the self discharge process
dependent on the used chemistry. They will NOT charged by the connected AC/DC adapter!
Using Alkaline batteries in combination with the external DC, the instrument can be operated
over several years.
The connector for the AC/DC adapter (4.5V/500mA) is placed at the rear panel of the
Thoron-Scout.
Changing the batteries will force you to adjust the re-set internal real-time clock. A
concerning message appears on the display of the Thoron-Scout. Stored data remain in the
memory and can be read out after changing of discharged batteries.
The selection of the right battery depends on the purpose and total duration of the
measurement. For principals, NiCd- and NiMH-accumulators with a cell voltage of 1.2 V as
well as alkaline-manganese or zinc-carbon batteries with 1.5 V can be used.
Important hint: Never use Lithium batteries - those cells provide a cell voltage of 3.0V or
3.6 V.
For long term measurements or frequent measurements with small periods of usage, the use
of alkaline-manganese cells is recommended as those batteries provide a high energy
density (up to 17000mAh) and a low self-discharging.
Time-to-time measurements for short term are best supplied by rechargeable batteries, as
they may be charged prior to usage. NiMH cells provide an energy density of up to 8000mAh
compared to NiCd-cells with a maximum of 5000mAh. In addition, maintenance to avoid
memory effects is not required for NiMH type but self-discharging is higher.
Because the capacity of any cell type is dependent on temperature, storage condition and
age (especially rechargeable batteries), the following data is only an approximation:
Alkaline-manganese 17000mAh: up to 4 weeks
NiMH 8000mAh: up to 2 weeks
NiCd 5000mAh: up to 1 week
If the battery cell voltage drops below 1.1 Volts, a warning “LOW BATTERY!!” appears in the
display each minute. Nevertheless the measurement can last for many more hours.
LOW BATTERY!!

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The remaining capacity is 15 ... 25% depending on the chemistry of the used cells. After
pressing the Toggle button display presents measurement results as usually. If longer
measurements are planned, the batteries should be replaced before to avoid unexpected
measurement break. If the cell voltage drops further, below 0.9 Volts, the running sample is
stopped automatically and the device enters the stand-by mode with “CHANGE BATTERIES”
indication.
CHANGE BATTERIES
Thoron-Scout
SN:00256
CHANGE BATTERIES
After plugging the power supply and waiting one minute the measurement can be started
anew.
The uptake of power during stand-by is about 15 – 20 % of a measurement. Anyway: In case
of storage of the instrument without usage, batteries should be removed.
Carrying out a measurement
Press short the Toggle button to start a new measurement series. The display will show the
remaining time to complete the first integration interval.
Thoron-Scout
SN:00256
Wait 120 Minutes
for first data !
The actual status and set-up information (see below) may be displayed by pressing the
button again.
If the first interval has been completed, five different display pages are available. The several
pages can be toggled by repeated pressing of the Toggle button. Depending on the selected
system of units, the concentration values are given either in ‘Bq/m³’ or ‘pCi/L’ (mbar/inHg,
°C/°F)
The first page shows the actual Radon concentration (calculated for the last sampling
interval) with the statistical error for a 1 Sigma confidence interval. If the “Fast” mode was
selected, a starlet is appended to the word “Radon” in the first row. Right beside, the time
stamp is given when the integration interval of the calculated concentration was finished
The third row contains at the left hand side the total number of integration intervals since the
last start of a measurement series. At the right hand side the pre-set integration interval and
the remaining time period of the actual sample is displayed.
Radon* 12:20
85Bq/m³±10%
#34 117/120Min
TSC-00256
Page two gives the same information for Thoron (Rn-220)
Thoron 12:20
124Bq/m³±16%
#34 117/120Min
TSC-00256

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The readings of the additional sensors are shown at the third page. Those values represent
the average derived from all “one minute shots” of the whole integration interval.
Ambient 12:20
21.5°C 987mbar
46%rH 12.3V
TSC-00256
The next page shows the average values of the Radon and Thoron concentration from the
very begin of the actual measurement series. The total sampling time is given in the first row.
Average 68.0Hrs
Rn: 314Bq/m³
Tn: 141Bq/m³
TSC-00256
The last page contains the status information, beginning with the date and time of the start of
the measurement series followed by the actual alert settings in the second line. The lower
line shows the mode for the acoustic signal (buzzer).
>>15/06/19 12:34
ALM: 10000Bq/m³
INTVL. BUZZ.OFF
TSC-00256
To finish a measurement series keep the Toggle button down and wait for at least four beeps
from the buzzer. If the button is released, the sample will be stopped, and the device will be
brought into the stand-by mode.
Thoron-Scout
SN:00256
If the button has been locked by software, the button has to be unlocked before.
Adjustment of the sampling interval
The adjustment can be carried out as long the sampling is stopped. The Toggle button must
be hold down for at least 6 seconds (beeper). On the display appears:
INTERVAL: 1min
Now, the interval can be toggled by the button between 1, 5, 10, 15, 30, 60 and 120 minutes.
To accept the new setting, the button must be pressed again for at least 6 seconds.
Operation Modes
All the settings for the operation mode of the device can be performed with usage of the
software application delivered with the unit. Please refer to the software manual for further
instructions.

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Pump
There is no pump in the Thoron-Scout. The air exchange depends on diffusion process only.
Alarm
If the measured Thoron or Radon concentration exceeds the programmable alarm limit, the
buzzer will sound shortly each second. The alert has to be acknowledged by pressing the
push button. The alert check is performed after completion of each integration interval. If the
alert is enabled, “ALARM ON” will appear in the lower line of the status page.
Fast/Slow Mode
“Fast” and “Slow” mode will determine the kind of calculation of the Radon concentration.
Please refer to the chapters “Theory of Operation” and “Statistical Error”.
Sniffing
The sniffing function allows to indicate Radon by an audible signal. That means that each
decay of the daughter products (either Po-216 only or Po-216 and Po-218, dependent on the
user settings) will cause a short beep. Especially the Po-216 (if present) with its short half life
will give a rapid information about local concentration changes.
Data Handling
Data Storage
All data are stored in a non volatile memory using so called ring-buffer architecture. That
means, the last 2047 data records (data of last 2047 integration intervals) remains in the
memory. Older data will be overwritten if the memory exceeds the limit. Because the
complete measurement data are transferred during download to the PC, the memory should
be cleared after successful data transmission and storage on hard disk. This will save time
during the next transmission and avoids redundant data storage.
Each data record is stored after completion of the integration interval and contains the full
information of this single integration interval:
•time stamp
•integration time
•alpha spectrum
•readings of additional sensors
All sequential records with a time distance to the last record equal to the integration interval
are interpreted later as one measurement series. The measurement may be interrupted as
often as desired to finish the old and start a new measurement series. There is no limit for
the number of series. Single point measurements are also possible.
Data transfer (RS232 and USB interface)
The serial interface according RS232 standard is required to read out measurement data and
to adjust the measurement parameter of the Thoron-Scout. Please note that the power
consumption of the instrument is about five times higher if connected to the PC by the data
transfer cable. In case that the device is permanently connected to a PC, the battery life-time
is reduced due to that. The RS232 port is also used for connecting a modem or ZigBee
wireless adapter.
Alternatively, the USB port can be used for communication. In that case, a software driver
(available on SARAD website) must be loaded and installed before. The communication path
appears as an additional COM port in RadonVision.
Both interfaces cannot be used simultaneously because the RS232 port will be disconnected
automatically after plugging the USB cable into the port.

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Statistical Error (for non-mathematicians)
The radioactive decay is a statistical process. That means, even if the Radon concentration
is constant over the time, the number of decays N counted within several intervals of the
same period will be different. N will vary around the mean value of all considered intervals.
Considering an infinite number of intervals would lead to an average which one indicates the
“true” result of N. For a single interval, the value of N will be either below or above the “true”
value. This observed deviation is covered by the term “Statistical Error”.
Therefore, each serious measurement contains beside the calculated Radon value the error
band for a stated confidence interval. The commonly used confidence intervals are 1, 2 or 3
Sigma (σ) which refer to a likelihood of 68.3%, 95.45% and 99.73%.
For example, the correct interpretation of a measured Radon concentration of 780 Bq/m³ with
a statistical 1σerror of ±15% is:
The real “true” Radon concentration lies with a likelihood of 68.3% within the range from 663
Bq/m³ (780 Bq/m³ - 15%) to 897 Bq/m³ (780 Bq/m³ + 15%).
Error Prediction
The relative statistical error E for a chosen confidence interval of k-Sigma can be predicted
from the number of detected counts N by the equation:
E[%] = 100% * k * √(N) / N
The simple consequence is: The higher the number of counts the higher is the accuracy of
the measurement. From the opposite point of view one could ask: How many counts I have
to detect to achieve a predefined uncertainty?
Two items will affect the number of counted decays: The sensitivity of the instrument at the
one hand side and the time period used for counting process (integration interval) on the
other hand.
While the sensitivity is an instrument specific constant, the integration interval may be
expanded to the maximum acceptable value for the desired time resolution of a
measurement series.
The relationship between the measured Radon concentration C
Rn
and the number of counts
N within an integration interval T is:
C
Rn
= N / (T * S)
whereby S represents the Sensitivity of the instrument, given in the unit [cts/(min*kBq/m³)].
The sensitivity using the slow mode is double as high as in the fast mode (see chapter
“Theory of Operation”) and whenever the required response time is more than 2 hours the
slow mode should be selected.
For the following examples a fast mode sensitivity of 4 cts/(min*kBq/m³) shall assumed while
the slow mode sensitivity shall be 8 cts/(min*kBq/m³).
The first question could be: What an integration interval T have to set to get a statistical
uncertainty less than 10% at a confidence level of 1σif the expected Radon concentration is
200 Bq/m³?
A 1σerror of 10% rquires 100 counts (100%* 1 * √(100) / 100 = 10%). Using the fast mode,
the integration interval can calculated by
T(fast) = N / (C
Rn
* S) = 100 cts / (0.2 kBq/m³ * 4 cts/(min*kBq/m³) = 125 min.
Because the required interval is longer than 2 hours, the slow mode is the better choice,
leading to the following result:

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T(slow) = N / (C
Rn
* S) = 100 cts / (0.2 kBq/m³ * 8 cts/(min*kBq/m³) = 62.5 min.
That looks pretty but makes no sense because of the longer response time. So we will set
the interval to 120 Minutes and ask for the statistical error in this case:
N(slow) = C
Rn
* T * S = 0.2 kBq/m³ * 120 min * 8 cts/(min*Bq/m³) = 192 cts
E(1σ) = 100 % * 1 * √(N) / N = 100 % * 1 * √(192) / 192 = 7.22 %
Now one could say 68.3% is not sure enough, I want to choose 2σconfidence interval to get
a more trustable result:
E(2σ) = 100 % * 2 * √(N) / N = 100 % * 2 * √(192) / 192 = 14.44 %
For interpretation look at the begin of this chapter.
Is an observed concentration change statistical significant or not?
If you have a look at the acquired time distribution you will see variations of the concentration
from point to point. The question is now: Is it a real change in the Radon concentration or
only a statistical fluctuation?
The test is very simple: Define a confidence level with respect to your needs and look at the
statistical error bands of the two points of interest. If the error bands do not overlap each
other, the change in the Radon concentration is significant otherwise it “can be or not can
be”.
Example 1:
Reading 1: 1500 Bq/m³ ±10% error band [1350 ... 1650 Bq/m³]
Reading 2: 1300 Bq/m³ ±13% error band [1131 ... 1469 Bq/m³]
The upper limit of the error band of the reading 2 is higher than the lower limit of the error
band of reading 1. Because the “true” value could be placed within 1350 Bq/m³ and 1469
Bq/m³, the variation of both readings is not statistical significant.
Example 2:
Reading 1: 1500 Bq/m³ ±10% error band [1350 ... 1650 Bq/m³]
Reading 2: 1000 Bq/m³ ±15% error band [850 ... 1150 Bq/m³]
The error bands of the readings do not overlap each other. Therefore, a statistical significant
concentration change is given.
Two arbitrary points of a measurement series may be considered using this test. It is not
necessary that the points are direct neighbours.
Detection Limit
The term Detection Limit defines the smallest value of the Radon concentration which
delivers a non-zero reading of the instrument within a given integration interval (at least 1
decay per interval). Because of the statistical behaviour a related confidence interval has to
be stated.
Why is it necessary to know the Detection Limit? If the set integration interval is short and the
Radon concentration low, the expected “true” value of the number of detected decays may
be around or less than 1. Because of the statistical variations, intervals without any detected
decay will appear frequently. The most extreme situation would be a measurement series
with a lot of “zero” intervals and only one interval with one detected decay (because a decay
cannot be split).
When calculating the Radon concentration by the given formula, the concentration value for
the interval with the one count is much to high while all other values show zero. Then, all

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intervals have to be averaged to get a usable result. This procedure is nothing else than to
create an integration interval long enough to meet the Detection limit for the applied Radon
concentration. To avoid zero readings, set the integration interval with respect to the lowest
expected concentration level during measurement.
The mean („true“) value of the number of decays during an integration interval in case of a
Radon concentration in the surrounding of the detection limit is less than 16 and therefore
the statistical fluctuations have to be derived by the Poisson distribution. The stated
confidence interval gives the probability that the detected number of decays within the
interval is not zero.
Confidence Interval Required Mean Value for
N at the Detection Limit
63,2 % 1
95 % 3
99.75 % 6
Example:
Determination of the detection limit of the Monitor using the „Fast-Mode“ and an integration
interval of 60 Minutes. The confidence interval shall be 95% (that means in about 95 from
100 intervals a no zero reading should appear):
Required mean value (number of counts from the table): N = 3.
Calculating the detection limit by the formula:
C = N / (T * S) = 3 cts / (60 min * 8 cts/(min*kBq/m³)) = 0.00625 kBq/m³ = 6.25 Bq/m³
The detection limit in this case is 6.25 Bq/m³.

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Technical Data
Measurement Ranges
Radon, Thoron 1 Bq/m³ … 10 MBq/m³
Temperature -20 °C … 40 °C
Humidity 0 … 100 %
Bar. Pressure 800 mbar … 1200 mbar
Response time (95%) Radon (fast/slow) 12 / 120 Minutes
Sensitivity Thoron 0,42 cts/(min*kBq/m³)
Sensitivity Radon (fast/slow) 0,85 / 1,5 cts/(min*kBq/m³)
Sample Interval 1 … 255 Minutes (adjustable)
Memory 2047 data records
Internal volume (chamber) approx. 60 ml
Power supply
Battery operation > 30 days
AC/DC adapter 4,5V/0,5A
PC -Interface (Serial) USB or RS232, 9600 Baud, 8N1
Dimensions 175 mm x 135 mm x 90 mm
Weight 1,1 kg (with Batteries)
Tamper detection if instrument is moved > 8 Seconds
User interface Display 4 x 20, 2 push buttons, buzzer
Caution
Please, do not carry the Thoron-Scout by holding the black cover!
Please do not carry out the measurements when Thoron-Scout is exposed to strong, direct
light source.