Carbon Targets for IsoTrace AMS
Accession Number: 2017.ph.763.1-2
This collection of artefacts consists of two containers that hold aluminum sample slugs in their plastic containers. The slugs are small (.3 cm diameter x .6 cm) aluminum cylinders that contain carbon from a test sample. The carbon is visible as spots on one or both end surfaces of each sample slug.
Each sample is housed in a roughly cylindrical clear plastic case (1.5 cm diameter x 2.5 cm) with a screw-on lid. Each case has a sample number written on it in black permanent marker. Cardboard boxes and one metal peanut tin, each containing small plastic cylindrical sample holders.
This artefact consists of the following containers:
2017.ph.763.1: A cylindrical metal tin labelled “Planters Unsalted Mixed Nuts” with no lid. The tin contains 44 carbon target slugs in their plastic containers. Some of the targets have been bound together with masking tape, though they have become separated as the tape has aged. The tin also contains a copper slug that does not have a container.
2017.ph.763.2: A small cardboard box with the lid torn off contains 15 carbon target slugs in their plastic containers. The box also contains two slugs without containers and one drill bit.
Primary Materials: Plastic, aluminum.
Each plastic container has a number written on it in black ink on both the top of the cap and the side. In some cases this number has been worn away.
2017.ph.763.1: Diameter = 10, Height = 9; 2017.ph.763.2: Height = 9, Width = 10.5, Length = 10.5
These targets were used in the accelerator mass spectrometry (AMS) method of carbon 14 dating as practised at the IsoTrace laboratory at the University of Toronto. These targets, which hold the carbon sample, are placed in a cesium sputter source. Carbon ions are sent through the AMS apparatus for counting.
Good: Some markings have been worn away.
Aluminum cylinders were provided by local suppliers. Carbon samples were prepared at the IsoTrace Laboratory.
c. 1982 – 2013, likely within the earlier part of that range.
These artefacts were produced at the IsoTrace laboratory. They were recovered, along with a number of other items, during the cleanup process following the closure of the IsoTrace laboratory and the opening of a new facility at the University of Ottawa.
These targets have been labelled using felt pen on the plastic cases. This suggests that they were created relatively early in the laboratory’s operation. Later targets carried a laser-engraved sample number on the aluminum target itself to prevent mix-ups.
These are described in a series of interviews with former IsoTrace director, Dr. Ted Litherland. These interviews may eventually be accessioned by the University of Toronto Archives & Records Management Services.
Published information on the preparation of samples at IsoTrace includes:
Beukens, Roelf P. “High-Precision Intercomparison at IsoTrace.” Radiocarbon 32, 3, 1990: 35-39/
This method of preparing the carbon samples was unique to IsoTrace. It was developed by Dr. Rolf P. Beukens at the Chalk River Nuclear Laboratory, and on the 1 Mv JN Van Der Graaff accelerator that was used at the University of Toronto Department of Physics before the opening of the IsoTrace Laboratory in 1982.