XNAP (X-ray Nanosecond resolution APD Pixel detector)

X-ray Nano-second resolution APD Pixel Detector. Development of a 32 x 32 pixel array of fast Avalanche Photo Diodes, directly coupled to a pixelated readout chip. This 2D device will provide nano-second time resolution as well as mega-Hz framing rates.

4x 4 pixel prototype XNAP system

Spatial response as determined with micro-beam scanning

The XNAP project (X-ray Nanosecond resolution APD Pixel detector) consists of the development of a two-dimensional counting pixel X-ray detector based on silicon avalanche photodiodes (APDs) bump-bonded to a read-out ASIC. Unlike most silicon sensors, apd’S have internal gain, which is achieved using an avalanche multiplication effect. As a result, these sensors have a fast signal rise time, allowing time resolution capabilities in the nanosecond range. Today such timescales are only accessible with single-element or linear arrays of fast devices.

The development of 2D detectors with high time resolution will increase enormously the experimental possibilities in applications such as fast X-ray diffraction and imaging, nuclear resonance scattering (NRS) or X-ray photon correlation spectroscopy (XPCS). As a consequence of the high time resolution these detectors will also be able to operate at counting rates two orders of magnitude higher than current hybrid pixel detectors, offering excellent possibilities for applications that require very high dynamic range.

The detector produced by this project will not be only a demonstrator but also a usable device for a number of different experiments.
First 4x4 pixel prototype devices, see figure below, have been produced and tested in the laboratory as well as at the ESRF beamlines.

Project Leader: Heinz Graafsma

Project Partners:

- DESY - Development of the interconnection and cooling scheme, detector tests.
Contact person: Heinz Graafsma
- ESRF - Coordination of the XNAP project, development of readout electronics and software, detector tests.
Contact person: Pablo Fajardo 
- PerkinElmer Inc - Design and fabrication of the APD sensors.
Contact person: Henri Dautet 
- Spring8 - Contribution to the specification and detector tests.
Contact person: Alfred Baron
- University of Heidelberg - Design and test of the readout chips (ASICs).
Contact person: Peter Fischer