pnCCD detectors for eROSITA

pnCCD detector characteristics

• chip thickness (=450µm) fully sensitive
• back-illuminated CCD
• image: 384 ∙ 384 pixels of 75 x 75µm 2 size (≈ 3 cm ∙ 3 cm)
• analog signal processor CAMEX: low-noise 128 parallel channels (multiplexed to 1 output)
• readout time per image: 10 ms
• read noise: 2 electrons rms
• FWHM (6 keV) ≈ 135 eV
• FWHM ( 280 eV) ≈ 52 eV
• no pixel defects
• quantum efficiency still 90% @ 12 keV
• power consumption: 0.7 W per detector (20 images/s)

Energy resolution

Fig.7: Prototype of eROSITA flight CCD detector module: CCD chip (on the left), 3 CAMEX analog signal processors (center), RC filters and interface to flexible lead (on the right)

Fig.4: Noise histogram of eROSITA CCD pixels. Mean pixel noise: 2.2 electrons rms; noisiest pixel: 2.8 electrons rms.

Fig.5: Spectrum at an energy of 280 eV (at synchrotron) measured with an eROSITA pnCCD. FWHM@280eV = 52eV.

Outlook

The measurements with the eROSITA pnCCD devices and the associated CAMEX readout chips revealed excellent performance. The currently assembled prototype of the eROSITA flight detector serves for testing of the complete flight camera system including the supply, control and data acquisition electronics. After verification, we start with the eROSITA flight camera array.

References:

• [1] L. Strüder, U. Briel, K. Dennerl, et al., A&A, 365,1 (2001)
• [2] N. Meidinger, R. Andritschke, S. Ebermayer, et al.,
Proc. SPIE, 7435 (2009)
• [3] N. Meidinger, R. Andritschke, S. Ebermayer, et al.,
Nucl. Instr. and Meth. A (2010),
doi:10.1016/j.nima.2010.03.126