After an upgrade of the TPX3CAM housing the detector was continued with new product names. The optical Timepix3 detector line has been split into two clearly named products: Chronos (the optical detector) and Phoebe (the intensified, single-photon version). Literature referring to an intensified TPX3CAM corresponds to Phoebe; a non-intensified optical TPX3CAM corresponds to Chronos.
Timepix4 is the successor to Timepix3, introducing finer timing resolution, a larger active area, and improved scalability. It has 512 x 448 pixels at 55 µm pitch (a single Timepix4 provides nearly the area of a full quad Timepix3 assembly), about 195 ps Time of Arrival binning, and a four-side buttable architecture that enables large, gap-free detector arrays. It supports both event-driven and frame-based acquisition modes (8-bit or 16-bit counters) and higher maximum throughput, with 130 million hits/s in today's standard configuration and high-rate variants extending toward 1200 million hits/s. Timepix4 powers LynX T4, the Timepix4-based Hyperion, and FeliS T4.
Medipix3 is a frame-based photon-counting chip, also from CERN. Instead of time-stamping individual hits, each pixel counts photons above one or more energy thresholds during an exposure and reads out complete frames. It supports charge-summing mode (to recover charge shared between neighbouring pixels and sharpen the energy response) and continuous read-write for near-zero dead time between frames. Medipix3 is used where steady, high-flux photon counting with energy thresholding matters, such as LynX M3.
Timepix3 is an event-driven hybrid pixel read-out chip developed at CERN, and the workhorse behind most of the ASI range. It has 256 x 256 pixels at 55 µm pixel pitch (about 14.1 x 14.1 mm active area per chip), measures Time of Arrival and Time over Threshold simultaneously per pixel, and provides 1.56 ns Time of Arrival resolution (down to 260 ps with the on-board Time-to-Digital converters, and about 3 ps with the PicoTDC option). Its event-driven read-out has roughly 475 ns per-pixel dead time and reaches up to 80 million hits/s on a single chip and up to 320 million hits/s on a 2x2 (quad) assembly. Timepix3 powers CheeTah, FeliS, Hyperion, Phoebe, Chronos, Telesto, and LynX T3.
The sensor is matched to the energy range of your experiment. Silicon (Si), 300 or 500 µm, is best for lower X-ray energies (roughly 5 to 15 keV) and for electrons. Gallium arsenide (GaAs:Cr), 500 µm, gives higher efficiency above about 15 keV, with fast charge transport and low timing jitter. Cadmium telluride (CdTe), 1 or 2 mm, provides maximum stopping power for hard X-rays. Sensor availability depends on the specific product.
A hit is a single activated pixel. A single particle or photon usually spreads its charge across several neighbouring pixels, producing a cluster of hits. Once that cluster is grouped back together it becomes one event, that is one detected particle or photon. Clustering hits into events also allows the impact position to be refined to sub-pixel precision.
Every Timepix 3 and 4 pixel measures two things per hit at the same time. Time of Arrival (ToA) is when the hit crossed threshold, that is its timestamp. Time over Threshold (ToT) is how long the signal stayed above threshold, which is related to the deposited energy. Together they provide position, precise timing, and an energy proxy from a single measurement.
No. A gated ICCD opens a fixed time window and integrates everything inside it. An event-driven detector needs no external gate: every hit is individually time-stamped as it arrives, so timing is captured continuously without defining a window in advance.
Frame-based detection (for example Medipix3) counts events during an exposure and then reads out a complete image, which suits high-flux, steady-state imaging. Event-driven detection, also called data-driven (for example Timepix3 and Timepix4), reports individual hits the moment they cross threshold, each with its own timestamp. There are no frames; the data stream contains only real events, which suits sparse, time-resolved, or asynchronous signals.
A conventional camera integrates signal over a fixed exposure (a frame) and reads out every pixel whether or not anything arrived, accumulating read noise and dark current. ASI event-driven detectors instead record only real hits, each tagged with its position, arrival time, and an energy-related measurement. There is no frame, no read-noise floor, and data is produced only when something is actually detected.
A hybrid pixel detector is built from two layers bonded together: a sensor (the top layer that absorbs the incoming particles or photons, made of silicon, GaAs:Cr, or CdTe) and a read out chip underneath, where every pixel has its own independent electronics. Each pixel counts and characterizes what hits it directly. This gives noise-free, single-particle-sensitive detection. The two bonded layers together are called the chip-sensor assembly.
ASI designs and builds hybrid pixel detector systems based on the Timepix and Medipix chip families, developed in collaboration with CERN. From its base at Science Park in Amsterdam, ASI turns these chips into complete detection systems for electron microscopy, X-ray science, neutron science, quantum optics, and mass spectrometry.
TPX3CAM was the general name for ASI's optical Timepix3 camera. Today that optical Timepix3 line is the Chronos family, offered as application-specific products that share the same core: Phoebe for single-photon imaging and quantum science, Telesto for neutron imaging and scattering, and Hyperion for velocity map imaging, mass spectrometry, and ion or electron imaging. A TPX3CAM referenced in the literature corresponds to whichever of these matches the application.
Phoebe is an intensified, single-photon-sensitive imaging detector for quantum optics and time-resolved photon science. A Timepix3 read-out is coupled to an optical intensifier, so each pixel time-stamps individual photons with nanosecond precision and very high signal-to-noise, without long exposures or gating. It is Timepix3-based, single- or quad-chip, sensitive across roughly 200 to 920 nm, with quantum efficiency set primarily by the intensifier photocathode, up to 320 Mhits/s, 260 ps time-stamping (about 3 ps with the PicoTDC option), and pairs with Luna for data processing. Applications include single-photon imaging and correlation, spontaneous parametric down-conversion (SPDC), Hong-Ou-Mandel and g²(0) measurements, entangled-photon and quantum key distribution experiments, trapped-ion and cold-atom state detection, and fluorescence lifetime imaging (FLIM). Single-photon sensitivity requires the external optical intensifier.
Hyperion (previously TPX3CAM) is an event-driven ion/electron imaging detector for velocity map imaging (VMI), mass spectrometry, and Time of Flight experiments. It captures each light flash' position, arrival time, and intensity at once, with multi-hit capability and no dead time between hits. Configurations are Quad-Pico (Timepix3, 512 x 512, 320 Mhits/s, 1.56 ns bins, with integrated 3 ps PicoTDC time-stamping) and TPX4 (Timepix4, 512 x 448, about 120 Mhits/s, about 195 ps bins). Applications include velocity map imaging, mass spectrometry, Time of Flight, 3D ion imaging, Coulomb explosion, photoelectron imaging, and high mass-to-charge detection.
FeliS turns a scanning electron microscope (SEM) into a high-speed, event-based platform for 4D-STEM in SEM, EBSD, and time-resolved experiments, with flexible mechanical integration that adapts to most chambers. It is Timepix3-based and used in transmission mode (below the sample, for 4D-STEM and TKD) or reflection mode (backscattered electrons for EBSD, sensitive down to about 3.5 keV), with Standard (512 x 512, 120 Mhits/s) or Turbo (512 x 512, 320 Mhits/s) bandwidth and a silicon thin-entrance-window sensor for 3.5 to 30 keV electrons. An optional motorised protective lid allows work in FIB/SEM chambers without venting. Applications include 4D-STEM in SEM, EBSD and orientation mapping, nano-beam diffraction, low-dose imaging and diffraction, and in-situ and time-resolved SEM. Note: if your application requires higher dynamic range, throughput or finer timing resolution, ask us about FeliS Medipix3 & Timepix4.
CheeTah is an event-driven direct electron detector for transmission electron microscopy (TEM). By recording only real electron events, it enables far faster acquisition with much smaller data volumes, and its single-electron sensitivity makes it well suited to low-dose work on beam-sensitive materials. It is Timepix3-based, in Single (256 x 256, 80 Mhits/s), Quad (512 x 512, 320 Mhits/s), Linea (256 x 1024, 320 Mhits/s), and Ultra (512 x 1024, up to 640 Mhits/s) configurations, with Si (300/500 µm), GaAs (500 µm), or CdTe (1/2 mm) sensors, up to 40 Gbit/s streaming, and about 1.56 ns timing. The same configurable sensor layout is available with Medipix3 technology. (GaAs/CdTe available upon special request). Applications include 3D electron diffraction (MicroED), 4D-STEM, ptychography, EELS, low-dose imaging, and in-situ and ultrafast TEM (UTEM).
Choose Timepix3 for time-resolved, single-particle, event-driven work at nanosecond timing. Its mature ecosystem also offers a wide range of detector configurations and mounting options. Choose Medipix3 for high-flux, frame-based photon counting with energy thresholding. Choose Timepix4 when you need the finest timing (below 200 ps), the largest gap-free area, or the highest hit rates. If you are unsure, tell us about your experiment and we will recommend the best fit.
MTF describes how well a detector preserves spatial contrast, that is sharpness, as a function of spatial frequency. The small 55 µm pixels and direct detection give ASI detectors a sharp response; the exact MTF depends on sensor material and thickness, and figures are available on request.
Every sensor has a safe operating limit. For optical systems the intensifier and sensor must not be over-illuminated, and for particle or X-ray detectors extreme flux should be avoided. If you work near high intensities, share your parameters and we will confirm safe operating conditions and any attenuation needed.
Yes. Detectors accept external trigger and Time-to-Digital converter signals for synchronisation with lasers, pulsed sources, or other instruments, and multiple detectors can run in a leader/follower chain through Serval.
Because read-out is event-driven, data volume scales with the number of real hits rather than with a fixed frame rate: sparse scenes produce little data, and there is no empty-pixel overhead. High-rate experiments can stream at up to 40 Gbit/s. Data is written as raw event files (.tpx3 and .tpx4) and/or processed images (TIFF, PNG) to disk, or streamed over TCP or HTTP, and then processed with Luna into HDF5.
In event-driven read-out the dead time is per pixel, about 475 ns on Timepix3 and about 400 ns on Timepix4, so the rest of the array keeps detecting while one pixel recovers. In frame-based (Medipix3) continuous read-write mode, successive frames can be acquired with near-zero dead time between them.
1.56 ns is the Time of Arrival bin size, the timestamp granularity, not a minimum pulse length. Individual hits are still detected even when the underlying signal is shorter; the arrival time is simply reported to the nearest 1.56 ns bin (finer with the Time-to-Digital converters or the PicoTDC option). Timepix4 brings this bin down to about 195 ps.
The Timepix3 quad is a 2x2 array of four Timepix3 chips forming a 512 x 512 pixel active area of about 28 x 28 mm. The chips are butted together with no physical gap. At each boundary between the quadrants, two pixels are not bump-bonded to the read-out, so a strip about 110 µm wide (two pixels at the 55 µm pitch) does not send data, while the rest of the array stays fully active. If your work needs a single fully continuous area, the Timepix4 is four-side buttable and tiles into larger seamless formats. Tell us about your setup and we will recommend the best configuration.
Each pixel has an individually adjustable threshold, set above the electronic noise so that only real signals are recorded. The lowest usable threshold depends on the chip, sensor, and calibration; FeliS, for example, detects electrons down to about 3.5 keV.
It depends on the sensor and on the energy or wavelength. For X-rays and electrons, thicker and higher-Z sensors (GaAs:Cr, CdTe) absorb more at high energies, while silicon is optimal at lower energies. For Phoebe's optical range, detection efficiency is set primarily by the intensifier photocathode across roughly 200 to 920 nm.
Requirements vary by system. ASI detectors run from a standard mains supply through the read-out electronics, which generate the low-voltage supplies and the sensor bias. Exact figures are given in each product's documentation.
Each Timepix3 chip has a 256 x 256 pixel active area of about 14.1 x 14.1 mm; a quad is roughly 28 x 28 mm. Overall dimensions and mounting depend on the product and configuration and on whether the detector runs in air, in vacuum, or inside a microscope or beamline. ASI supplies mechanical drawings and instrument-specific or vacuum-compatible mounts for each system, so send us your setup and we will match the mount.
Yes. Because control runs through the open Serval HTTP API, detectors can be scripted and integrated with beamline or instrument control systems, and synchronised with external hardware through trigger and Time-to-Digital converter inputs.
Three tools cover control and processing. Serval is an HTTP API server providing unified control and data acquisition across the entire ASI detector portfolio, so any language or tool that speaks HTTP can control the detector, and it can stream raw events, processed images, and live previews simultaneously. Accos is the graphical interface for real-time control, configuration, live image and histogram preview, guided per-pixel equalisation, and pixel masking across Timepix3, Timepix4, and Medipix3 systems, and includes a dedicated 4D-STEM mode. Luna is a high-performance post-processing suite, written in Rust, that converts raw .tpx3 and .tpx4 event data into analysis-ready HDF5, with clustering, timewalk correction, and Time of Flight computation, plus tools for 4D-STEM workflows with LiberTEM-compatible output.
Head to our Technology section to browse available documentation. For each product, ASI provides spec sheets, brochures, user manuals, and a list of publications. Can't find what you need, or using a software version with additional features? Contact ASI or your local representative for the documents specific to your system.
Tell us your technique, your energy or wavelength range, your timing requirements, and your instrument, and we will recommend a chip (Timepix3, Medipix3, or Timepix4), a sensor, and a product configuration to match.
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