Updated 2007-06-24

MacCHESS automounter

MacCHESS has an ALS-style crystal automounter available at beamline F1.

• Making arrangements for use
• Use
• Trial kit
• Required equipment
• Recent Developments

Automounters are intended to help maximize throughput at synchrotron beam lines where heavy shielding and safety interlocks slow manual access to the experiment. A sizable number of crystals (64 in our setup) 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 or 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.

Accomodation for automounter commands has been incorporated into the MacCHESS data collection software.

At present the software interface is not very sophisticated, but we will be improving it as we gain experience. The next key step in this agenda is implementation of auto-centering in the MacCHESS crystal centering interface.

The automounter does not interfere with manual mounting methods, and switching between automatic and manual mounting methods is no problem.

Trial Kit

MacCHESS has two trial kits, each consisting of seven (7) pucks stacked in a tower, all the tools necessary to handle the pucks, and an out-of-date instructional CD-ROM from Brookhaven.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.

Since MacCHESS has only two trial kits, we cannot guarantee that one will be available for you. Please request a trial kit at least a full week in advance to allow for shipping and to give yourself 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. These products should work well:

Pin bases (also sometimes referred to as caps)

• Hampton Research HR4-779 - specifically designed for ALS. These are the ones I recommend. The shoulder-free base is more tolerant of slight misalignment of the automount gripper.
  HR4-904 - vials for HR4-779
  
• ALS lists another source of these bases, Vineburg Machining Inc.
  
• Hampton Research HR8-116 = "CrystalCap HT" (HighThroughput)*
  
• Mitegen Base B1*
  

• HR4-733 - CrystalCap Magnetic
  
• HR4-745 - CrystalCap Copper Magnetic
  
• Any style of base with plastic parts or vial threads.
  

The Hampton "CrystalCap Magnetic" is the most popular base on the market, so if you're not certain what you have, assume that it is not automounter-compatible.

Pins

No bent pins, no copper pins. Pin height should be consistent. Try Hampton 18 mm pins or Mitegen 19 mm pins. The MacCHESS automounter is similar to equipment in use at ALS and at Brookhaven. Our gripper is the ALS Mk II Gripper (with local modifications by Mike Cook), so information from ALS can be considered most relevant:
Brookhaven pin list
LBNL says:

The dimensions are fairly critical here, and the most important one from the automounter's standpoint is the distance from the inside mounting surface (which corresponds with the top of the goniometer magnetic mount) to the center of the crystal = 20.3mm ± 1mm.

Pucks

Sixteen (16) pins fit into a puck. In the automounter DeWar, the puck lid is held in place upside-down, as depicted below, with the crystals pointing up for access by the gripper. The pin bases are held in place on the puck lid magnetically.

When loading the pucks in your own lab, it may be easier to put the pins in the puck body crystal end down, and non-magnetic puck lids are provided in the trial kit for this purpose.

Up to four (4) pucks fit into the DeWar in the hutch, so up to 64 pins may be accessed without manual reloading.

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 same reason.

According to ALS, pucks and tools are available from Boyd Technologies.

SSRL, ALS and the SMB-CAT at APS are collaborating on a new Universal Puck Project that should fit both ALS and SSRL automounters. The puck lid is strongly magnetic, and the puck body has weak magnets inset for use with the SSRL robot. MacCHESS has a sample of the universal puck and will evaluate it soon.

Recent Developments

The MacCHESS automounter has reached a state of consistent mechanical reliability. Soon laser pin sensors will be added, which should help to prevent and detect the most common human and machine errors.

ALS-style Automounter resources at other synchrotron facilities:
Berkeley Center for Structural Biology
NSLS Protein Crystallography Research Resource

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