XRD1 Sample Changer
A new Sample Changer (SC) is available on the XRD1 as a result of an in-house development project at ELETTRA. The SC has been designed to handle only SPINE standard sample holders and vials stored into cryo-vial baskets: 5 baskets (i.e. up to 50 samples) can be loaded into the dispensing dewar of the SC where they lie in a liquid nitrogen bath.
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The SC has been designed to handle only SPINE standard sample holders and vials stored into cryo-vial baskets [Fig.1], following the standard already established at ESRF beamlines (SC3 system as sample changer). 5 baskets (i.e. up to 50 samples) can be loaded into the dispensing dewar of the SC where they lie in a liquid nitrogen bath. The control of the instrumentation is performed through a GUI (called ‘Sample Changer Control’), which can be opened from the main Beamline Control Panel, both inside and outside the experimental hutch of the beamline [Fig.2]. Basket Loading The first step deals with the loading of the cryo-vial baskets. Each basket must be inserted into (and later removed from) the loading aperture of the dispensing dewar by means of the proper transfer tool available at the experimental table. The loading aperture is made available by removing the plug with the handle; this of course must be repositioned once the loading/unloading procedure is terminated. Once catched the basket with the transfer tool, the angular positioning groove of the basket must be oriented as indicated by the arrow on the box of the SC in order to properly insert the basket into the basket holder [Fig. 3]. There are 5 different basket holders in the inner carousel, so the loaded baskets are labeled from 1 to 5 in order to distinguish them. The loading procedure can be managed by means of a button panel available at the experimental table:
During the procedure the GUI shows the basket position and can also be used instead of the button panel to select the desired basket to be loaded/unloaded/changed. Sample Decoding
One can rely on a DataMatrix decoding procedure in order to use the datamatrix code of the sample holders (see SPINE standard) to identify the samples. Once loaded the baskets the user can start through the GUI the “Scan All Baskets” procedure, which takes about 15 minutes to try to decode each sample of each basket. Also “Scan selected basket” procedure can be launched, for example when only one basket has been inserted or changed. Sample Mounting Decoding procedure is available but not mandatory, of course. Once loaded the baskets the samples are ready to be safely mounted (and then dismounted) by the SC: the user selects the desired sample and press the ‘Pick up’ button to get it transferred on the goniometer head in vertical position; this ‘Top’ geometry assures the wet transfer of the samples to (and from) the measurement position, where they are cooled by a Oxford crycooler. At this point the usual centering procedure (2-click centering on the ‘Crystal Centering’ window) can be used to center the sample on the beam trajectory, in order to prepare the crystal exposition. After the exposure (be it one shot to check the crystal quality or any data collection set) the user can remove the sample by pressing the ‘Remove’ button, getting ready for the mounting of some other sample.
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 Fig.1. Top-left. SPINE standard for sample holders and vials: it also imposes a fixed length of 22 mm for the whole sample holder (18 mm for the pin) and presents a 10 character identification code. SPINE sample holders and vials can be obtained from Molecular Dimensions Limited (MDL). Vials from Hampton Research (HR) are not fully supported at the present, but can still be used. Bottom. Datamatrix codes on the base of the caps; on the left two caps from MDL, on the right one from HR: according to our experience MDL caps may become rusty by use as shown, so we recommend to pay attention to the conditions of your sample holders or use HR model, if you want to rely on the possibility to perform Datamatrix recognition. Top-right. Cryo-vial baskets can be obtained from crystallographic kits of MDL: each can store 10 cryo-vials. One can distinguish also the groove which is used determine the angular positioning.  Fig.2. The Graphical User Interface. On the right frame, the possibility to load/unload and scan for decoding a selected basket (as well as all baskets): the list shows the result of decoding for the 10 basket samples. In the central frame, the possibility to mount (unmount) the selected sample on the measurement position.  Fig.3. An overview of the top of the SC with the components involved in the loading basket procedure. The transfer tool (1) catching the cryo-basket to be inserted into the loading aperture (2). The arrow (3) indicates the position of the angular groove of the basket so to help it enter inside the basket holder in the SC. The aperture must be finally closed by remounting the plug (4).
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