A photon couting pixel detector for Materials Science

The increase in experimental possibilities associated with the new synchrotron sources are often limited by the quality of available detectors. In order to increase the experimental possibilities of the D2AM-CRG@ESRF SAXS camera and goniometer, a new 2D detector is developed using the pixel hybrid technology. Its aim is to provide a large dynamical range and a high counting rate as required by materials science studies using X-ray scattering. The project started in 1999, with a 1st prototype XPAD1 tested in 2000-2001. Then, followed a 2nd version XPAD2 (2002-2006) which corrected a few problems. The 3rd generation XPAD3 has been processed and is under test.

The project involves 3 laboratories :

• Institut Neel, CNRS, Grenoble and CRG D2AM at ESRF with J.F. Bérar, N. Boudet, B. Caillot, S. Arnaud

• Centre de Physique des Particules de Marseille, IN2P3 with P. Delpierre, P. Breugnon, J.-C. Clemens, B. Dinkespiler, S. Godiot, M. Menouni, Ch. Morel, P. Pangaud, R. Potheau, E. Vigeolas

• Synchrotron Soleil, Paris with S. Hustache, K. Medjoubi.

XPAD3 (2005 to present)

New chips have been designed using a radiation-hard submicronic technology (IBM 0.25μm) which allowed to reduce the pixel size to 130 μm with similar or enhanced performances. Si modules consist in 7 XPAD3 chips of 80x120 pixels each and CdTe modules use 2 XPAD3 chips. A wide Si detector build with 8 modules has been assembled.

The chip allows a counting rate above 2.105 photons/pixel/s that is more than 2.107 photons/mm^2/s. Detectors using Si diode work in the range 5-25keV and those using CdTe diodes will allow to extend the working energy range up to 60keV.
Side and front views of the detector installed on the ESRF-D2AM goniometer		one Si module
Ag Behenate recorded at 24keV using CdTe diodes bump-bonded to 2 chips .	A lysosyme crystal diffraction at 5.9keV	Surface diffraction of AsGa dots at SOLEIL- DIFFABS (Thanks to M. Gailhanou - IM2NP)

XPAD2 (2002-2006)

These chips use a similar geometry as the XPAD1 ones. The dispersion of the threshold observed in XPAD1 was corrected. A new design of the bounding was used to enhance the counting rate.

XPAD2 detector : 8 modules x 8 chips

Designed according D2AM-CRG/ESRF detector requirements : dynamic range > 109 counts/pixel, saturation rate > 107 photons/s/pixel , energy range 5 to 25, keV Berar et al., IEEE/TNS 52-5(2005) 1994-1998
Chip of 24x25 pixel of 330x330μm², AMS CMOS 0.8 μm
Diodes of 500 μm Si thick -> efficiency 78 % @15keV, 21 % @25keV
	Diode array -> PCB card : drivers, regulators. Modules -> acquisition card (ethernet). Tiled as close as possible -> reduce shading Size : 200 x 192 pixels , Surface 68x68 mm^2.
	XPAD2 applications : ← Multilayers reciprocal space mapping        Powder diffraction →

XPAD1 (2000-2001)

These chips of 24x25 pixels were used for the first prototypes with Delphi diodes. Each pixel is 330x330μm². Modules of 10 chips, 6000 pixels, have been tested at the BM2-CRG beamline of the ESRF in 2000-2001. A summary of their characteristic is given as a short booklet.

Boudet et al., NIM A 510 (2003) 41-44 Berar et al., J. Appl. Cryst. 35 (2002) 471-476	Quasicrystal Bragg peak and diffuse scattering
	Linearity

Some references : The following lists some papers or presentations related to this project.

last modified by J.F. Bérar and N. Boudet