The ePixHR5kHz is one of the first in-house LCLS-II detectors in development and is targeted at being a replacement for the ePix10ka, with the capability to run data 5kHz frame rate. The prototype has been built within the mechanical envelope of a front-facing small ePix10k as can be seen in Figure 1.
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Table 1. Design requirements and measured performance of key characteristics.
Requirements | Results | |
Mode of Operation | Integrating with: •auto-ranging high-low •auto-ranging medium-low •fixed high gain •fixed medium gain •fixed low gain | Integrating with: •auto-ranging high-low •auto-ranging medium-low •fixed high gain •fixed medium gain •fixed low gain |
Pixel size | 100x100 µm2 | 100x100 µm2 |
Range | Auto-ranging: >40000 keV (transitions 400keV/1200keV selectable) Fixed high gain: >400 keV Fixed medium gain >1200keV Fixed low gain: >40000 keV | Auto-ranging: 64000 keV (transitions 400keV/1200keV selectable and tunable) Fixed high gain: 880 keV Fixed medium gain 2640keV Fixed low gain: 64,000 keV |
Noise r.m.s. | < ~400eV (~110e-rms) | ~ 270eV* (~75e-rms)* |
As stated in the table, the detector has an a 100um pixel pitch and can be configured in 5 different gain modes; 3 fixed gain modes and 2 auto ranging gain modes. The pixel array size for the detector is 192x144. Figure 2 show a depiction of the ASIC layout with core blocks highlighted.
Figure 2. Image of the ASIC functional blocks.
In order to facilitate the high framerate the number of ADC boards at the edge of the ASIC was increased, giving raise to the balcony seen in both Figures 1 and 2. The structure of the analog channel for the ePixHR5kHz, with the additional optimizations done compared to the ePix10ka channel highligted, can be seen in Figure 3.
Figure 3. Analogue channel layout for the ePixHR5kHz pixel.