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PIN Diode Radiation Detector

ThereminoGeiger

A PIN diode (p-type, intrinsic, n-type diode) is a diode with a wide region of intrinsic semiconductor material (undoped) contained between a p-type semiconductor and an n-type semiconductor.
The advantage of a PIN diode is that the depletion region exists almost completely within the intrinsic region, which has a constant width (or almost constant) regardless of disturbances applied to the diode. The Intrinsically region can be made large as desired, by increasing the area in which the pairs of gaps can be generated.
The generation of charge carriers within the intrinsic region may be due to the radiation incident lumionsa, For these reasons, many photosensors include at least one PIN diode, such as PIN photodiodes or phototransistors. In addition to the light radiation, the charge carriers can also be generated by gamma radiation or X radiation: for this reason, a PIN diode can also be used as a solid state radiation detector.

PIN Diode Detector

Pin-Photodiode
PIN diode basic scheme

We choose to utilize a radiation detector that contains a PIN diode array plus a circuitry which amplifies the signal and generates a TTL output.

pinDiode
Detector scheme

Detector type : RD2014
Detector Sensitivity : 1 CPS/mR/h (or 5.8 CPM/μSv/h)
Radiations : Beta+Gamma
Supply voltage range : VCC 3.0 V to 5.0 V
Supply current : 400 μA TYP, 450 μA MAX
Output pulse level Equal to supply voltage (positive going)
Output pulse width 40 μsec to 150 μsec

Theremino Geiger

Based on a simple and reliable hardware, this tool has a sophisticated software (open source) that turns it into a professional equipment, similar to a “Rate-Meter”, with characteristics unattainable from the “usual” Geiger counters. The possibility of making averages over long times allows to perform accurate measurements with the most various sensors. This tool is great in education and experimenting and it gives schools and technical institutes the opportunity to carry out professional analysis, such as the determination of the natural radioactivity of ceramics and building materials.

Connection with PC

The PC has to be connected, through USB cable, to a “Master” module that can be purchased on site thereminostore.com or built “do-it-yourself” following the instructions on the site www.theremino.com.

master
Theremino Master

RD2014 Sensor Connection

connection

In the scheme and picture shown above you can see the connection of the sensor RD2014. The power supply line of +5V comes from the connector present on the Master (see the picture below) and must be filtered with an RC filter. The TTL signal that comes from the sensor has to be connected to an input of the Theremino Master through a 33k resistor in order to limit the current, this is because the input “high level” voltage has a value of 3.3V instead of 5V.

tevisoMaster
Detector + Theremino Master

Measurement Software

The measurement software is Theremino Geiger, below there are some example pictures :

chart1

chart2

In the above images you can see, in the first screenshot, the measure of the background radiation level, and in the second one the radiation level of the low-sodium salt, which contains potassium with the radio-isotope 40K. This is a “difficult” analysis that needs long time to be performed. The measure stabilizes and trust lines converge towards the value of 100 nS/h which is the normal background radiation level present in the laboratory and towards the value of 400 nS/h when the potassium salt is put near the detector.

Software Features

  • Integration time adjustable from 1 to 9999 seconds (almost three hours)
  • Integration of type “finite response” based on FIFO followed by a moving average
  • Readout of radiation level in micro-Sievert and milli-Roentgen
  • Continuous updating of the measurement accuracy based on the amount of events
  • Continuous updating of counts per second, per minute, and the total elapsed time
  • Scale in uS/h with candle-sticks of Min-Max (trust lines)
  • Analog display calibrated in uS/h, mR/h, CPS and CPM, useful for fast” analysis
  • Chart with speed control
  • Chart with memory with “zoom”
  • Calibration of “sensitivity”, “background” e “dead time” for each sensor
  • Modularity and full integration with the Theremino system through SLOT
  • Ability to transmit data via SLOT, IP, local network and the Internet
  • Adjustable sounds in order to realistically reproduces the “click” of Geiger
  • Typical sounds for alarm and event reporting
  • Detailed LOG
  • Availability of different languages

Configuration Parameters for Teviso RD2014

Sensitivity : 1 CPS/mR/h
Background : 0 CPS
Dead time : 0 us

Americium Cap (241Am)

americio

Caesium Spark Gap (137Ce)

cesio

Autunite (uranyl phosphate)

autunite

Uraninite (or Pitchblende)

uraninite

“Fiestaware” Uranium Glaze

fiestaware

Thorium Gas Mantle (232Th)

thorium

Radium Watch Hands

radium

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