Fully spectral imaging detector with central hole: ideal for XRD, SAXS or SEM

The AdvaPIX TPX3 Quad presents a new line of ADVACAM detectors optimized for XRD, SAXS, or similar tasks where a primary pencil beam of radiation passes through the detector without interaction. For this purpose, we developed a Quad detector with a monolithic sensor with a central hole (the device version without a central hole exists as well).

The detector is based on the Timepix3 chip developed by Medipix collaboration in CERN. Four Timepix3 chips (256 x 256 pixels each, pixel pitch 55 micrometers) are assembled to a single monolithic Silicon sensor 3×3 cm with a circular hole with a diameter of 2.04 mm in the center.

The foldable design allows two basic geometries with different detector orientations for specific applications of users. The amount of material behind the sensor is minimized so that several modules can be layered. A combination of Silicon and CdTe layer can be especially advantageous in maximizing detection efficiency and energy resolution.

Readout electronics and hardware

The AdvaPIX TPX3 Quad uses a single USB3.0 interface providing synchronized operation of all four Timepix3 chips. The maximal speed of 40 million hits per second for the whole device is provided in fully spectral mode (called pixel mode or data-driven mode). The PiXet software is adapted for this new device.

The detector design is vacuum compatible. It can be optionally connected to a water cooling circuit for better temperature stabilization.

Detector properties

Most of the functional properties are very similar to other Timepix3 based devices of ADVACAM: AdvaPIX TPX3 or MiniPIX TPX3. The minimal threshold is about 2 keV (depending on sensor type and thickness). The energy resolution in counting mode is about 0.3 keV (sigma) at 8 keV (Cu K-alpha) for Silicon sensors.

This spectrum was measured with a 0.3 mm thick Si sensor performing threshold scan in frame mode.

The typical energy resolution in pixel mode is shown in the table below for XRF K-alpha lines of several common metals (measured with 0.3 mm thick Si sensor).

Typical applications

X-rays: The functional properties of Timepix3 detectors for Energy Dispersive XRD (and WAXS or SAXS) were described in my previous article by Dr. Jan Jakubek. There are clear benefits: Photon counting with energy discrimination, the high spatial resolution of 55 micrometers (or better), fully spectral mode, effective suppression of radiation background, and compact size.

The Quad Timepix3 detector with a central hole offers 4 times larger solid angle coverage and does not require the beam-stop. The primary X-ray beam transmitted through the sample passes the hole in the sensor and can be detected downstream with an additional detector bringing additional information.

The modularity of the detector can be used with great advantage combining transmission XRD, WAXS, and SAXS into a single system with three stationary detectors: The first plane with silicon sensor is placed close to the sample recording XRD and WAXS signal. The transmitted beam continues through the hole carrying SAXS information which is detected by the second layer at a suitable distance. The primary beam continues through the hole in the second layer and can be finally measured by a third layer composed of a single device such as MiniPIX TPX3.

Electrons: electron microscopy SEM, STEM, channeling

Ions: RBS, ERDA, channeling …

When it will be available?

The detector is currently intensively debugged and software tuned. The first batch of devices for beta testing should be available in the summer. Any suggestions, remarks, or requirements for the mechanical design are very welcome!

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