PIXI-III main characteristics

  • very large area (31.7×25.0 mm2) organized as a 512×402 pixels on a square matrix at 62 µm pitch
  • shaped pulse duration < 450 ns at the base
  • linear range > 12000 electrons (> 60 keV for CdTe)
  • saturation level > 18000 electrons (> 90 keV in CdTe)
  • ENC: 50 electrons rms
  • residual offset after auto-calibration: ± 50 electrons
  • 2 independent discriminator/counter
  • windowed counting mode

PIXII-III can be configured in several modalities, the most important being:

  • Pixel mode (PM). Each pixel works in windowed counting mode independently  from the others. Read-out < 6 ms. Highest rate capability ( > 1MHz), no sharp color separation, multiple counts if thr. very low.
  • Neighbor Pixel Inhibit  mode (NPI).  Only one counter per event allowed to count. The hit is  allocated to the pixel receiving the highest fraction of the total charge. Highest position resolution and the lowest possible noise but sharpness of the color separation not completely solved yet
  • Pixel Summing mode (PSM). The signals of 4 neighbor pixels are summed together in each pixel to correctly evaluate the total energy of any event involving up to 4 pixels. Since the SUM is performed in each pixel, i.e. at the same  pitch of 62 μm in both X&Y directions, the PSM mode, when used in combination with NPI, ensures that both the spatial accuracy and energy resolution are finally preserved.  A factor 2 increase of the pixel noise and a factor 4 increase  of pulse pile-up  is the unavoidable trade-off.