MiniPIX TPX3

Minipix

Advacam’s MiniPIX TPX3 camera is miniaturized and low power radiation camera version of Timepix3 with particle tracking and imaging detector. The camera module contains CERN’s latest Timepix3 detector, which is position, energy and time sensitive. The camera digitally registers each ionizing particle for its position, energy, time of arrival and track shape. The other properties can be often measured from the track shape of the particle.

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Description

Advacam’s MiniPIX TPX3 camera can be used in a variety of applications, such as X-ray radiography in low flux), spectral X-ray imaging (X-ray fluorescence imaging; energy dispersive XRD, WAXS or SAXS without monochromatic X-ray source; radiation monitoring (particle type sorting, spectroscopy, directional sensitivity, etc); spectral gamma ray imaging (scintigraphy or SPECT, radiography with isotopes); gamma camera with available special shielded box and collimators; and compton camera with available special software module for image reconstruction.

The Timepix3 detector has quick sparse data readout where each detected particle or photon is either accumulated in pair of images (frame mode) and read-out later at maximal speed of 16 frames per second or read-out immediately (pixel mode) at maximal rate of 2.35 million hit pixels per second. The device is controlled via USB 2.0 interface with standard µUSB connector.

All major operating systems are supported (MS Windows, Mac OS and LINUX). The PIXET PRO software used for detector operation is provided for free. Extra software modules are available for special functions (e.g. coded aperture image reconstruction, Compton camera image and spectrum reconstruction, radiation field decomposition, networking of many devices, etc).

Sensor Material: Si or CdTe
Sensor Thickness: 100 μm, 300 μm and 500 μm for Si; 1 mm CdTe
Sensitive Area: 14 mm x 14 mm
Time Resolution: 1.6 ns
Readout Speed: 2.35 Million hits/s
Frame rate: 16 fps
Number of Pixels: 256 x 256
Pixel Pitch: 55 μm
Energy Resolution: 0.5-1 keV (Si) and 1.1-3.6 (CdTe)
Min Detectable Energy: 3 keV (Si) and 5 keV (CdTe)
Readout Chip: Timepix3
Pixel Mode of Operation: Time-over-Threshold, Time-of -Arrival
Connectivity: µUSB 2.0
Weight: 30 g
Dimensions: 80 mm x 21 mm x 14 mm
Software: Pixet Pro

Typical Applications:

Spectral X-ray imaging: X-ray fluorescence imaging, X-ray radiography (low flux)
Energy dispersive XRD, SAXS or WAXS: The monochromatic X-ray source is NOT needed! Even high energy for thick samples is possible (e.g. 100 keV)
Spectral gamma ray imaging: Scintigraphy or SPECT, radiography with isotopes
Radiation monitor: Particle type sorting, spectroscopy, directional sensitivity
Gamma camera: Special shielded box and collimators
Compton camera: Special software module available for image reconstruction

Documents

Device parameters

Operating conditions

Symbol	Parameter	Min	Typ	Max	Units	Comment
T_A	Temperature Range	0	50	70	°C
Φ	Humidity	0	55	60	%	Not condensing

Electrical Specification

T_A = 25°C, USB voltage V_CC = 4.8V

Symbol	Parameter	Min	Typ.	Max	Units	Comment
V_CC	Supply Voltage	4.0	5.0	5.5	V	Comply with USB 2.0
I_CC	Supply Current		300	500	mA	Comply with USB 2.0, Mode dependent
P1	Power Dissipation			2.5	W
Bias Voltage Source for Sensor Diode
V_BIAS	Bias Voltage (positive version)	3		450	V	Max. limited internally according to sensor type
V_BIAS	Bias Voltage (negative version)	-4		-450	V	With CdTe or CZT sensor

Performance characteristics

Symbol	Parameter	Min	Typ.	Max	Units	Comment
f_f	Frame-rate			16	fps	with USB 2.0 Host
T_FREAD	Frame Readout Time³	62			ms
f_p	Pixel type hit-rate in ToT+ToA mode (pixels per second)			2.35 x 10⁶	pps	with USB 2.0 Host

Pixel mode hit-rate measurement

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.

Sensor parameters

T_A = 25°C

Symbol	Parameter	Si				CdTe		Units	Comment
	Thickness	100	300	500	1000	1000	2000	µm
	Minimum energy threshold	2.0 – 2.7	2.0 – 2.7	2.0 – 3.0	2.0 – 3.0	2.5 – 4.5	3.0 – 5.0	keV
σ _Thl@60	Energy resolution in ToT mode (σ @ 60 keV)	1.2 – 2.6	1.3 – 2.7	1.4 – 3.5	1.7 – 3.6	2.8 – 5.4	2.9 – 8.3	keV
σ_Thl@122	Energy resolution in ToT mode (σ @ 122 keV)					3.4 – 6.0	4.5 – 9.9	keV
	Typical detectable energy range for X-rays	2.0 – 60				2.5 – 500		keV	See chart below
	Pixel size	55						µm

Basic principles, measurement types and modes

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:

Measurement modes:

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)
Time-of-Arrival (ToA)	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)
Fast-Time-of-Arrival (FToA)	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] = ToA25 – FToA1.5625 ToA and FTOA are combined together by software. If saved then ToA and FToA are stored as separate items

Measurement types:

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):

Type	Mode	Range	Description
Frame (reading all pixels after end of exposure)	Event+iToT	10 bit + 14 bit	2 output frames per exposure: 1^st Events = Number of events in pixel, 2^nd 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.
	ToA	18 bit	1 output frame: ToA+FToA¹= Time of Arrival of first event in pixel.
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.
	ToA	18 bit	3 numbers per pixel per event: Position, ToA and FToA¹defined..
	Only ToT	10 bit	2 number per pixel per event: Position and ToT.

Device description

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 device casing is made of aluminum with sliding cover made of stainless steel protecting sensor window. The communication and powering is provided by USB Micro-B connector and cable.

USB connector

USB type Micro-B, Standard USB 2.0 High-Speed.

Mechanical dimensions

All dimensions are in mm.

* Sensitive surface distance from top of the box is for 300 µm sensor thickness.

¹ ToA and FToA are combined together by software automatically. If saved, ToA and FToA are stored as separate items (for Pixel type measurement).