Optimal signal-to-noise ratio
PILATUS3 Hybrid Photon Counting detectors are inherently free of dark current and readout noise. The absence of any detector noise guarantees data with an excellent signal-to-noise ratio (Fig. 1).
Fig. 1: Comparison of data quality of flatpanel and PILATUS3 X CdTe detector. The photon-counting CdTe detector shows significantly less noise resulting in improved visibility of weak diffraction rings. Acknowledgment: These powder diffraction patterns were measured by Marco Di Michiel at the High-Energy Scattering Beamline ID15A of the European Synchrotron Radiation Facility (ESRF) using the same settings (photon energy of 46.3 keV and 0.1 s exposure time) on both detectors.
Cadmium Telluride Sensors for highest Quantum Efficiency
Each CdTe detector module comprises two large CdTe crystals (sensors) each with dimensions of 42 mm × 34 mm, leaving a horizontal gap of only 3 pixels between the two crystals. The CdTe thickness of 1000 µm provides high quantum efficiency for hard X-ray energies up to 100 keV (Tab. 1).
|Photon energy||CdTe 1000 µm|
|20.0 keV||>90 %|
|40.0 keV||81 %|
|60.0 keV||90 %|
|80.0 keV||77 %|
|100.0 keV||56 %|
Table 1: Quantum efficiency of PILATUS3 CdTe sensors (experimentally verified values, click for more details).
High local and global count rates
The PILATUS3 X CdTe detector is compatible with count rates of more than 5 x 106 counts/s/pixel (Fig. 2), which corresponds to almost 2 × 108 counts/s/mm2. These high count rates are enabled by the DECTRIS instant retrigger technology featured by all PILATUS3 detectors. Count rate correction is applied to provide accurate intensity measurements over the full range of count rates. Excellent long-term stability guarantees stable operation: less than 1 % signal variation (reduction through polarization) is observed at 2.5 × 106 counts/s/pixel over hours.
Fig. 2: Count rate characteristics of PILATUS3 X CdTe detector. Measured data (symbols) was fitted to the theoretical curve (line) acquired at 60 keV X-ray energy, 30 keV energy threshold.
All PILATUS3 detectors are electronically gated and do not require a mechanical shutter; this is a noticeable simplification of the measurement setup. Combined with the noiseless readout of the PILATUS3 detectors, it enables continuous data acquisition; opening new perspectives in imaging and time-resolved experiments.
Electronic gating and external trigger
Exposure times can be varied from a few nanoseconds to several hours and are controlled either internally or by applying an external gate signal. The external trigger input with a programmable delay function makes synchronization between the detector and other hardware extremely easy.
For an example showing picosecond time-resolved laser pump/X-ray probe experiments see [T. Ejdrup et al., J. Synchrotron Radiat. 16, 387 (2009)].
The basic element of every PILATUS3 detector is the detector module. Multiple modules can be combined to form large-area detector setups with different geometries. DECTRIS offers four PILATUS3 X CdTe detector systems covering a wide range of active areas and frame rates to perfectly suit your measurement needs. Moreover, DECTRIS possesses the expertise required to develop and manufacture application and customer-specific systems, such as in-vacuum detectors and custom module arrangements.
Excellent Point-Spread Function
The point-spread function (PSF) describes the spatial resolution of an imaging detector. Due to the direct conversion of X-rays into charge pulses, PILATUS3 detectors spread virtually no intensity between pixels. Even above the absorption edges of the CdTe sensor, only very little signal is spread by fluorescence to the neighboring pixels. The point-spread function of the PILATUS3 detector is thus essentially given by its pixel size (172 µm) and allows optimally sharp images to be taken. These are free of artifacts typical for other detectors (such as blur, intensity tails, blooming, or streaking). With the sharp point-spread function in combination with the high dynamic range of the detector, closely spaced signals even of largely differing intensity, can be accurately resolved and measured.
High dynamic range
A counter depth of 20 bits (~ 1 million counts) in conjunction with the absence of detector noise ensures unprecedented contrast and dynamic range, leading to excellent image and data quality. Extremely strong and weak signals can be accurately detected on a single image (Fig. 3). Especially for high-energy photons, it is an important advantage that each photon only generates a single count independent of the photon energy, as this preserves the detector's high dynamic range at all energies.
Fig. 3: Reciprocal space map showing X-ray Diffuse Scattering of a Bismuth sample studied at 69.7 keV. Acknowledgment: Measurement by Alexei Bosak (ESRF) at beamline ID15A using PILATUS3 X CdTe. Recording 10 frames per second, the measurement was completed within only a few minutes. The detector's high dynamic range is essential for measuring the extremely weak diffuse scattering signal between the strong Bragg peaks.
Short readout times, high frame rates, and still no image lag
PILATUS3 X detectors feature a short readout time of below 1 ms and high frame rates of up to 500 Hz (250 Hz for the 2M) which substantially reduce measurement time and maximize efficiency and throughput. Unlike scintillator-based CCDs and flatpanels, the direct conversion CdTe detector shows no image lag, which enables maximum scanning speed in your experiment that fully exploit the detector's high frame rate. In conjunction with versatile trigger and gating capabilities, dynamic processes on fast time scales can be investigated in-situ.
See as an example [W. Bras and A.M. Beale, "Combined time-resolved X-ray scattering and spectroscopy methods" in Spectroscopic Properties of Inorganic and Organometallic Compounds, Royal Society of Chemistry, Volume 43, 257-288 (2012)].
PILATUS3 detectors provide an adjustable lower energy threshold to suppress fluorescence. Combining the high dynamic range with the excellent point-spread function, fast readout and fluorescence suppression enables the pursuit of exciting new applications, e.g. in diffuse scattering (Fig. 3).
[A. Bosak et al., Phys. Rev. Lett. 103, 076403 (2009)] and [C. Bärlocher et al., Science 333, 1134 (2011)]
The PILATUS3 CMOS readout chips are designed using radiation-tolerant layout techniques developed for high-energy physics to prevent damage from incoming X-rays. The detectors are able to withstand the doses arising from long-term operation at modern synchrotrons.
[P. Kraft et al., J. Synchrotron Radiat. 16, 368–375 (2009)]
Ease of operation
All PILATUS3 detector systems can be operated at room temperature and only require dry air or N2 for operation. They are easy to set up and demand no regular maintenance or service. The CdTe detector software is identical to that of their well-established silicon-based detector complements; guaranteeing simple and fast integration.