MacCHESS has ALS-style sample automounters available at beamlines A1 and F1. The F1 automounter is a BAM-1 model with pneumatic actuators, while the model at A1 is a BAM-2 with a 3-axis Cartesian robot. Both accept Uni-, ALS, and Rigaku pucks and ALS-compatible bases with 18 mm pins. See "required equipment" for more details.
Automounters are intended to help maximize throughput at synchrotron beam lines where safety measures slow access to the experiment. A sizable number of samples can be stored in the hutch, accessed randomly, mounted and dismounted; all without entering the hutch.
Making arrangements for use
If you wish to use the MacCHESS automounter, please specify this when you apply for beam time. Automounter requests may affect scheduling, since we may want to schedule equipment setup by our technical staff during weekday working hours and schedule automounter users consecutively.
If you need to borrow a trial kit from MacCHESS, allow enough time for us to ship the kit and for you to familiarize yourself with the equipment. See below for more details.
Some other facilities use elaborate database tracking, which requires advance registration of every crystal. MacCHESS does not have this, so advance database registration of your crystals is not required nor available.
If your crystals or reagents are hazardous, advance notification is required, as for all other MacCHESS experiments.
Use of equipment at MacCHESS
If you wish to transfer crystals from vials to pucks at MacCHESS, we can provide Dewars and nitrogen. Be sure to allow for adequate time for such activity before your scheduled beam time.
MacCHESS personnel will set up the automounter and train you in its use.
Software control of
Accommodation for automounter commands has been incorporated into the MacCHESS data collection software.
The automounter does not interfere with manual mounting methods, and switching between automatic and manual mounting methods is no problem. With the BAM-2, manual mounting will probably require stepping on the safety mat in front of the automounter. See the Software instructions for a procedure to recover from this.
MacCHESS has a limited number of trial kits consisting of seven (7) ALS or Uni-pucks stacked in a tower, all the tools necessary to handle the pucks, and an out-of-date instructional CD-ROM from Brookhaven. Pins and bases are not included.
Please request a trial kit at least a full week in advance to allow for shipping and to provide sufficient time to familarize yourself with the equipment and load the pucks. Also, please return the kit when you visit CHESS or in a timely manner afterwards. Regular users of automounters might consider purchasing their own equipment.
Required equipment: pins and pucks
The automounter requires the use of pins and bases with tight tolerances to ensure that they can be reproducibly accessed by the gripper.
BAD: Do not use any sample base with a square shoulder, such as Hampton Research CrystalCap or Mitegen B1, B2 or B3. That square shoulder is likely to cause a crash if the sample or the gripper is slightly out of position, since the gripper approaches the base from the top. Do not use any sample base with a plastic body or screw threads.
GOOD: Choose bases compatible with ALS automounters. These have an all-metal base with a sloping shoulder which provides self-centering correction to the automounter gripper, which approaches the base from the top. Hampton Research CrystalCap ALS or CrystalCap ALS HT should be fine; as should Mitegen B1A or B3S. Bases meeting the SPINE spec should also work (HR CrystalCap SPINE HT, Mitegen B5). Barcodes are irrelevant, MacCHESS does not have barcode readers on its automounters.
Pin height should be 18-19 mm, so that crystal height with the base on a level surface is about 22 mm. No bent pins. Slightly bent pins will work (~< 2mm), but slow the task of centering the crystal. Severely bent pins may cause a gripper crash which could destroy the sample, along with other samples in the puck. Copper pins may work but are not recommended. The sample mount itself may be a nylon loop, a micro-manufactured polymer loop, or a mesh; they all should work.
Our automounters support ALS pucks, Uni-pucks and Rigaku/MSC pucks. ALS and Uni-pucks hold up to sixteen (16) samples each. A Rigaku puck holds 12 samples. In the automounter Dewar, the puck base is held in place magnetically as depicted below, with the crystals pointing up for access by the gripper. The BAM-1 sample Dewar at beamline F1 holds up to 4 pucks for a maximum of 64 samples. The BAM-2 sample Dewar at beamline A1 holds up to 9 pucks for a maximum of 144 samples at a time. Note the position of the alignment posts. In the BAM-1 these are toward the center of the circle. In the BAM-2, these are toward the user.
BAM-1 sample plate BAM-2 sample plate
To load fresh crystals into a puck, put the puck cap upside down in a bowl of nitrogen. Harvest
a crystal with a sample holder on a magnet-on-a-stick, and plunge it stright into a position in
the puck cap. If you do not complete a full puck in one session, you can use the non-magnetic
puck bases included in the trial kit. Once you put the regular magnetic puck
base in place, the sample holders will stick to the puck base rather than the puck cap.
Up to seven (7) pucks fit into a tower, which fits right into a Taylor-Wharton
CP-100 travel Dewar. Store pins in the lower pucks first for best liquid nitrogen
coverage. Note that the crystal end of the pins point towards the bottom for the
Pucks and accessories are available from Crystal Positioning Systems, Mitegen, Hampton Research, The University of Georgia Instrument Shop, and who knows, possibly elsewhere.
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