Hard X-ray Detector (HXD)
The HXD consists of the 4x4=16 identical detector units. The four sides of the detector units are surrounded by 20 thick anti-counters made of BGO for background shield. The anti-counters are also expected to detect transient high energy phenomena such as the gamma-ray bursts. Directions of the gamma-ray bursts are determined from the ratios of the numbers of events detected by different anti-counters.
Each detector unit is furthermore divided into four deep wells by the BGO active shields. Although the detector does not have imaging capability, the field of view is limited to by the shielded well. At the bottom of each well, a GSO crystal, which deposits X/gamma-rays above ~50 keV, is glued. Those events which are detected by the GSO but not by the surrounding BGO are considered good X/gamma-ray events ("clean hit" events).
The GSO scintillator emits optical lights when they absorbed X/gamma-ray photons. The optical lights are detected by photo-multiplier attached to the bottom of each well-detector, and signals are read through the pre-amplifiers. On the GSO crystal, two layers of the PIN diodes, which are sensitive to X-rays between 10 and 50 keV, are put. HXD carries 128 PIN diodes in total.
Inside of each well, passive fine collimaters made of phosphor bronze sheet are placed to limit the field of view for soft X-rays (< 100 keV), so that the field of view becomes comparable to those of XRS and XIS. The fine collimaters are also expected to reduce the cosmic diffuse X-ray background, which otherwise might be a significant background source for the PIN diodes.
The on-board electronics consists of the HXD-AE (Analog Electronics) and HXD-DE (Digital Electronics). HXD-AE includes the Analog Control Unit (ACU), Well Processing Units (WPU) and Transient Processing Units (TPU). There are four WPU (WPU0-3) and four TPU (TPU0-3). Each WPU handles PMT and PIN events from adjacent four well-counters. Each TPU processes events detected by adjacent five anti-counters.
For more in-depth information, please refer to the HXD home page.
If you have any questions concerning Suzaku, visit the Feedback form.