The end station is currently equipped with a large active area detector (Eiger X 16 M) along with two high-precision diffractometers developed in-house, which can be switched to perform conventional cryo-crystal diffraction experiments or in situ crystal diffraction experiments. Additionally, an in-house-developed sample mounting robot enables fully automated rapid sample exchange in less than 30 s. Data collection from the diffractometer and detector is controlled by an in-house-developed data collection software (Finback) with a user-friendly interface and convenient operation.
Fig 1 Endstations
（1）Detector
BSL-2 Macromolecular Crystallography Beamline(BL10U2) is equipped with a large active area detector (Eiger X 16M). Currently, major data processing software (including iMosflm, XDS, DIALS, autoPX, HKL2000 etc.) directly support the experimental data of Eiger X 16M, and there is no need to decompress the data before processing. Unlike traditional detectors, the Eiger detector collects raw diffraction data in a file format called HDF5 instead of one file per diffraction pattern. HDF5 is a popular and open-source container format for storing scientific data. Currently widely used in research fields including artificial intelligence and free electron lasers. There are two types of HDF5 files output by Eiger X 16M, namely master files and data files. Among them, the master file mainly stores metadata, similar to an image header, but provides much more information, and can also save a small amount of original diffraction data. The data file saves the original diffraction data. When viewing diffraction patterns or data processing, simply open the master file to access the entire set of data (except for Adxv, which requires opening the data file).
Tab 1 Specifications of Eiger X 16M
| Eiger X 16M | |
| Pixel size | 75×75 µm2 |
| Pixel count | 4150×4371 |
| Effective area | 311.2×327.8 mm2 |
| Maximum speed | 1 mm/s |
| Movement distance range from Detector sample to point | 135-800 mm |
| Read frame rate | 133 Hz（Full） 750 Hz（4 M） |
| Maximum resolution | 0.685 Å |
（2）In-house-developed two high-precision diffractometers
During the construction of the experimental station, we overcame the engineering difficulties caused by the scientific need for radiation protection and biosafety to coexist. We independently designed and developed two high-precision diffractometers which can be switched to perform conventional cryo-crystal diffraction experiments or in situ crystal diffraction experiments.
Fig 2 In situ crystal diffraction experiments
Fig 3 Conventional cryo-crystal diffraction experiments
（3）In-house-developed sample Changer
Samples can be mounted either manually or using an in-house-developed sample changer called swordfish, which requires approximately 20 s to remove a crystal sample from the goniometer and replace it with a new one in the storage Dewar capable of storing 320 samples (20 pucks) at a time. A barcode reader was used to scan the crystal information, which was useful for recording information during high-throughput crystal screening. A standard pin with a length of 18 mm is recommended. Routine calibration and maintenance ensure reliability, and an increasing number of crystals have been easily screened since the installation of swordfish.
Fig 4 Design drawings of in-house-developed sample Changer (A. Physical diagram B. Overall composition diagram C. Design diagram of new storage Dewar D. Design diagram of new robot gripper)
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