TA = 25°C, USB voltage VCC = 4.8V
|VCC||Supply Voltage||4.0||5.0||5.5||V||Comply with USB 2.0|
|ICC||Supply Current||300||500||mA||Comply with USB 2.0, Mode dependent|
|Bias Voltage Source for Sensor Diode|
|VBIAS||Bias Voltage (positive version)||3||200||450||V||Max. limited internally for thin Si sensor|
|VBIAS||Bias Voltage (negative version)||-4||-300||-450||V||With CdTe or CZT sensor|
|ff||Frame-rate||16||fps||with USB 2.0 Host|
|TFREAD||Frame Readout Time1||62||ms|
|fp||Pixel type hit-rate in ToT+ToA mode (pixels per second)||2.35 x 106||pps||with USB 2.0 Host|
The whole detector is exposed to homogenous perpendicular irradiation from X-ray tube operated at 18 kVp with 2 mm Aluminum filter. The measurement type is set to “Pixels” and mode to “ToT+ToA” all other parameters are set to factory defaults (as stored in configuration file delivered with device). The exposure time is set to 0.1 s. The “Clustering” tool of PiXet-Pro is used to analyze measured data. The number of hit pixels per second is drawn as function of X-ray tube current searching for saturation.
TA = 25°C
|σThl@23||Energy resolution of energy discrimination threshold @ 23 keV||0.5||1.1||keV||rms|
|σ Thl@60||Energy resolution of energy discrimination threshold @ 60 keV||0.6||1.5||keV||rms|
|σ ToT@23||Energy resolution in ToT mode (σ @ 23 keV)||0.7||3.0||keV||rms|
|σ ToT@60||Energy resolution in ToT mode (σ @ 60 keV)||1.0||3.6||keV||rms|
|Typical detectable energy range for X-rays||3 – 60||5 – 500||keV||See chart below|
The ionizing radiation particle interacts with the sensor material creating an electric charge. This charge is collected by electric field and brought to pixel preamplifier where it is amplified and shaped forming triangular voltage pulse. The amplitude and duration of this pulse is proportional to energy deposited by particle within the pixel. The situation when the voltage pulse amplitude in particular pixel exceeds preselected threshold value is called “event” or “hit”.
Each pixel contains three digital counters (10, 14 and 4 bits). These counters are used differently according to measurement type and mode. There are four basic values which can be measured and stored in counters of each pixel:
|Number of Events||number of events (hits) in the pixel during exposure time (this mode is suitable mainly for frame type readout)|
|Time-over-Threshold (ToT)||measured as number of periods of 40 MHz clock signal (25 ns step) when amplifier output signal stays over the energy threshold. The ToT can be transformed to energy in keV using per-pixel-calibration function. The coefficients for per-pixel-calibration are unique for each detector pixel and they are stored in configuration file delivered with device. The energy calibration is valid only for given values of other detector parameters as delivered in configuration file (especially threshold)|
number of periods of 40 MHz clock signal (25 ns step) from start of exposure till the event is registered by pixel (i.e. pulse in pixel crosses the threshold). The range is
409.6 µs. Additional 16 bits are added in FPGA in readout electronics so that the total range is 26.8 seconds. The additional bits are usable only if the pixel hit rate is below maximal value (see fp in table of Performance characteristics)
time difference between event detection and next clock signal measured with step of 1.5625 ns. Range is 4 bits. The combination of ToA and FToA gives precise time of event detection in nanoseconds using following formula:
Time [ns] = ToA*25 – FToA*1.5625
ToA and FTOA are combined together by software. If saved then ToA and FToA are stored as separate items
|Frame type measurement||No data is sent out of device during the exposure time. All measured events are accumulated in counters of pixels. Event counter is incremented and ToT is integrated for all events. The measured data is read-out after end of exposure time for all pixels with nonzero content. No measurement can be performed during readout process.|
|Pixel type measurement||Information about all hit pixels is read-out immediately and continuously during exposure time. If hit rate is below maximal value (see fp in table of Performance characteristics) then there is virtually no deadtime.|
Major modes and types of operation (rarely used combinations are shown with gray background):
(reading all pixels after end of exposure)
10 bit + 14 bit
2 output frames per exposure:
1st Events = Number of events in pixel,
2nd iToT = total time over threshold for all events in pixel.
|iToT||14 bit||1 output frame: iToT = total time over threshold for all events in pixel.|
1 output frame: ToA+FToAError!Bookmarknotdefined.= Time of Arrival of first
event in pixel.
(reading only hit pixels continuously during exposure)
|ToT+ToA||10 bit + 18 bit||4 numbers per pixel per event: Position, ToT, ToA and FToA.|
3 numbers per pixel per event: Position, ToA and FToAError!Bookmarknot
|Only ToT||10 bit||2 number per pixel per event: Position and ToT.|
The device is supplied with USB flash disk containing installer of PiXet-Pro software, unique device configuration and calibration file and protocol on quality tests. The communication and powering is provided by USB Micro-B connector and cable.
The device is delivered with protective plastic box covering the sensitive detector part. The protective box is used only for transportation. Protective cover has to be removed before use to avoid sensor damage from overheating. The removing has to be performed with extreme care avoiding any touches to the sensor chip or wire-bonds. Sensor chip is supplied with high voltage up to ±500V. To avoid sparks or unwanted discharge follow EN 61010-1 (chapter 6.7, Insulation requirements. Fig. 4, Tab. 6, Annex C).
USB type Micro-B, Standard USB 2.0 High-Speed.
|Drawing of the device with aluminum baseboard supporting the PCB side:|
|All dimensions are in mm.|
1 During Readout time (or Dead time), no signal is collected from the sensor.
2 ToA and FTOA are combined together by software. If saved then ToA and FToA are stored as separate items.