MIXS on BepiColombo and its DEPFET based focal ... - MPG HLL

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J. Treis et al. / Nuclear Instruments and Methods in Physics Research A 624 (2010) 540–547 545 Fig. 7. Photos of front- (left) and backside (top right) of a Macropixel matrix prototype, being an representative sample for the <strong>MIXS</strong> detectors. The overall sensor sensitive area is 3.2 3.2 cm 2 , the envelope size of the hybrid is 4 in. 4 in. The pixel array dimension is 64 64 and the pixels (bottom right) have five drift rings each and a size of 500 500 mm 2 . The pixel structure and the control- and read-out electronics on the frontside is clearly visible, as well as the completely homogeneous entrance window on the backside. 60 Offset (ADU) 50 2600 Row number 60 50 40 30 20 Noise (ADURMS) 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00 20.00 Row number 40 30 20 10 60 50 10 20 30 40 50 60 Columnnumber 2800 3000 3200 3400 3600 Residual Offset (A DU) 10 10 20 30 40 50 60 Column number Row number 40 30 20 -500.0 -300.0 -100.0 100.0 300.0 10 10 20 30 40 50 60 Columnnumber Fig. 8. Offset (right) and noise (left) map of the tested Macropixel device. The offset map entries are the mean values of typically 1000 offset values per pixel, the noise map values are their variances. The column-like structure on the offset map (top right) is due to the ASTEROID’s channel-to-channel offset variation, the sensor itself shows in the residual offset map (bottom right) no bright pixels at all, and no systematic variation, except for a slightly higher offset values at the edges, which is due to thermal reasons. The noise map is also very homogeneous, the noise dispersion is at the order of 7%. The mean value of the noise map entries translates in an ENC value of 4.1e rms. The slightly higher noise at the bottom sensor rim is due to additional thermal load from the front end ICs. successfully taken into operation and have been tested. These devices, originally being manufactured as prototypes for the SIMBOL-X focal plane [15], have the identical pixel structure and array dimension compared to the <strong>MIXS</strong> detectors, but the pixels have five drift rings instead of three to cover the larger active area. In addition, the sensor is not divided into hemispheres. As the
546 J. Treis et al. / Nuclear Instruments and Methods in Physics Research A 624 (2010) 540–547 scaling behavior of the drift ring structure is very well known, the prototypes are being considered as representative samples for <strong>MIXS</strong>. The sensors also possess the same entrance window configuration. Fig. 7 shows photographs of the sensors frontand backside, and of the pixel structure itself. The completely homogeneous aluminized entrance window can be recognized, as well as the pixel structure on the frontside, together with the two control-ICs and the ASTEROID IC. The overall hybrid size is 4 in. 4 in. A total number of five hybrids of that type was built. Three devices were homogeneous and defect-free, one had only one defective row, and only one structure had a larger number of defective pixels. Given the larger area of the devices compared to the <strong>MIXS</strong> flight detectors, a production yield of around 70% can be expected. The sensors have been tested in a vacuum environment at a relatively low sensor temperature around 90 1C, with a 18000 16000 10000 14000 12000 1000 Pattern multiplicity Singles Doubles Triples Quadruples Counts 10000 8000 6000 4000 Counts 100 2000 0 5600 5800 6000 6200 6400 6600 6800 7000 Energy(eV) 14000 12000 10 10000 1 1000 2000 3000 4000 5000 6000 7000 8000 Energy(eV) Counts 8000 6000 4000 2000 0 5600 5800 6000 6200 6400 6600 6800 7000 Energy(eV) Fig. 9. Sample spectra taken with the Macropixel array using an 55 Fe source. No inefficient pixels were found. The left figure shows the spectra for the various multiplicities (gray coded), the right figures show the peak region for the singles spectrum and the integral spectrum taking into account all multiplicities. The energy resolution measured was 126 eV FWHM at 5.9 keV taking only singles, i.e. events without charge sharing, and 128 eV FWHM taking all valid event patterns, which is in agreement with the expectations. The peak to background ratio of 3000 shows the suitability of the devices for spectroscopic measurements. 60 60 Row number 50 40 30 20 10.00 133.8 257.5 381.3 505.0 628.8 752.5 876.3 1000 Row number 50 40 30 20 10.00 133.8 257.5 381.3 505.0 628.8 752.5 876.3 1000 10 10 10 20 30 40 50 60 Column number 10 20 30 40 50 60 Column number Fig. 10. Imaging test using an silicon baffle of 0.45 mm thickness. The smallest feature size is 0.4 mm. The left image shows an intensity plot (photons per pixel), the right image an extrapolated contour plot.
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MIXS on BepiColombo and its DEPFET based focal ... - MPG HLL

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