Do you need an imaging detector with a hole in the middle?

An instant development of new imaging structures in ADVACAM results in a new line of detectors optimized for XRD, SAXS, or similar tasks where a primary pencil beam of radiation needs to pass through the detector without interaction. For this purpose, we developed a Quad detector with a monolithic sensor with a central hole as shown in the pictures below.

The detector consists of four Timepix or Timepix3 readout chips flip-chip bonded to a single monolithic silicon sensor. The sensor layout is designed with a small offset for chips making a square space of 39 x 39 pixels in the sensor center for drilling a hole. The hole diameter is 2.04 millimeters.

These detectors are fabricated in several standard versions differing in thickness: 100, 300, and 500 micrometers. The other thicknesses are possible too.

The performance of these new quads is equivalent to standard single chip assemblies. The hole machined in the middle doesn’t affect the noise floor, stability, imaging nor spectral properties.

Readout electronics

There are multiple options for readout electronics: either ADVACAM’s existing readouts (four synchronized AdvaPIX TPX3 devices or four MiniPIX TPX3 in their flex versions) with an independent readout channel for each chip or a brand new device AdvaPIX TPX3 Quad being currently intensively tested.

The AdvaPIX TPX3 Quad has been developed for the Timepix3 version of the Quad detector. It uses a single USB3.0 interface providing synchronized operation of all four Timepix3 chips. The PiXet software is being adapted for this new device.

Detector mechanics: What shape suits your application best?

The final detector mechanics is being designed now. It addresses several simple requirements:

• electronics placed aside of sensitive area (similarly to AdvaPIX),
• the minimum amount of material behind sensors,
• a completely free path for primary X-ray beam passing through the hole,
• vacuum compatibility,
• attachable heatsink for temperature stabilization of Timepix3 chips.

Any suggestions, remarks or requirements for mechanical design are very welcome! (maximal sizes, connector types, mounting holes placement …).

Primary application: XRD/SAXS

The functional properties of Timepix3 detectors for Energy Dispersive XRD 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 need for beam-stop reduces the sensitive area of the imaging detector and limits the maximal energy to be used for XRD of heavy samples since higher energy penetrates the beam-stop.

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