NZ scientists fire up $3.4 million mass spectrometer

By Peter Griffin 19/05/2010

Scientists at the Crown Research Institute GNS Science are this morning showing media through its Lower Hutt Rafter Radiocarbon Laboratory where a new accelerator mass spectrometer has been installed.

Caption:  Scientists Johannes Kaiser (left) and Albert Zondervan with the new $3.4 million accelerator mass spectrometry facility at GNS Science's National Isotope Centre in Lower Hutt. It is the only facility of its type in the Southern Hemisphere and its applications include climate resaearch, archaeology, oceanography, geology, earthquake and volcano research, marine biology, and dating antiquities. Photo - Margaret Low, GNS Science
Caption: Scientists Johannes Kaiser (left) and Albert Zondervan with the new $3.4 million accelerator mass spectrometry facility at GNS Science's National Isotope Centre in Lower Hutt. Photo - Margaret Low, GNS Science

What will this expensive gadget, which represents the largest single investment in equipment since GNS became a CRI in 1992, actually do?

Well, GNS is the go-to place in the country for radiocarbon dating, which uses a carbon radioisotope (carbon-14) to date material up to around 50,000 years old. This is generally used for carbon-dating organic material like sediments, wood, bones and plant matter.

The really interesting stories to do with radiocarbon dating emerge when the technique is used to date ancient relics that are uncovered, particularly our distant human ancestors.  But the impetus behind the upgrade from the existing aging particle accelerator is climate science research. Part of the overall effort underway in New Zealand to try and reduce greenhouse gas emissions from agriculture is research to better understand how carbon influences soil and the exchange of carbon between soil and the atmosphere.

Here’s a Q&A on radiocarbon dating from GNS Science:

1. In very simple terms, how does an accelerator mass spectrometer work?

It first converts sample atoms into a stream of ions. Using static electric and magnetic fields, it then accelerates, deflects, focuses and separates individual charged ions on the basis of their mass. It then measures the intensity of each separated beam to arrive at an abundance ratio. Further ‘offline’ analysis is needed to convert this data into environmental parameters such as a calendar year.

2. How many radiocarbon laboratories are there in the world?

There are about 50 radiocarbon dating laboratories in the world, with 28 having accelerator mass spectrometry facilities. The new accelerator mass spectrometer is an integral part of the Rafter Radiocarbon Laboratory, which is recognised as part of the worldwide accelerator mass spectrometry (AMS) laboratory network.

3. How many laboratories operate the same type of compact accelerator?

Ten other laboratories use the same type and size of accelerator mass spectrometer for radiocarbon measurements. However, the new facility at GNS Science is unique worldwide because it has been modified to measure the isotopes of beryllium-10 and aluminium-26 in addition to carbon-14. This versatility ensures it will contribute to a wide range of science applications in New Zealand.

4. What are the main advantages of the new facility?

High reliability, high precision, and low operating costs. It represents significant gains in efficiency and gives New Zealand a modern accelerator mass spectrometry facility that ranks among the best in the world.

5. What is the life expectancy of this new facility?

A minimum of 15 years.

6. How compact is the new facility compared to the one it has replaced?

The new facility occupies about 25 percent of the floor area of the one it replaces. The (old) Van de Graaff accelerator mass spectrometer is from a much earlier era and was imported from Australia in the early 1980s. It has been a worthy workhorse for New Zealand science and has dated about 50,000 samples during the past three decades.

7. How easy is the new facility to operate and can it work around the clock?

The modern operator system incorporates several layers of automation. Once a batch of 40 samples has been started and the optimal parameters set, the system can proceed unattended.

8. How many staff are needed to operate the new AMS facility?

Two full-time staff.

9. What materials can you date with radiocarbon dating?

Anything that once lived and containing carbon up to about 50,000 years old. This includes wood, leather, bone, paper, seawater, gases, ice cores, pollen, pottery, coral, seeds, charcoal, blood residues, human remains, sediment, soil, shell, textiles, plant and animal tissue, insect remains, cave paintings, and natural resins. The Rafter Radiocarbon Laboratory also plays a role in international radiocarbon calibration programmes.

10. What is the point of difference of the Rafter Radiocarbon Laboratory?

The new AMS system places the Laboratory in the top bracket of such facilities worldwide. Its high precision and reliability will enable GNS Science to provide an improved level of service to clients, particularly those who have special requirements such as very high precision, express service, or very small sample size — less than 0.0005g of carbon.

11. How much does it cost to have a sample dated?

The standard charge is $NZ820. This price reflects the complexity of the dating process, the expertise of the scientists and technicians, and the high-end equipment involved. This price is internationally competitive.

12. How long does it take to produce a date for a client?

It usually takes eight weeks from the time a sample is received. This can be shortened by several weeks if a client requests an urgent turnaround. An extra fee applies to express handling of samples.

13. What is the accuracy of AMS radiocarbon dating?

Usually plus or minus 35 years. With some samples, GNS Science can offer an enhanced accuracy service which delivers plus or minus 20 years.

14. What are the practical applications of carbon-14 dating?

Applications include dating antiquities, atmospheric studies, archaeology, climate research, oceanography, geology, earthquake and volcano research, marine biology and carbon dynamics.

15. Can you give examples of age-dating and tracing assignments the Rafter Radiocarbon Laboratory undertakes?

Earthquakes: Work with geologists to age-date pre-historic ruptures on major New Zealand faults including the Wellington Fault, the Alpine Fault, and the Wairarapa Fault to elucidate past fault behaviour and possible future earthquake threat. Landslides: Age-date significant pre-historic landslides in New Zealand to elucidate possible future threat from this hazard.

Tsunami: Age-date pre-historic tsunami deposits on New Zealand’s coastline to elucidate size and frequency of these events and possible future threat.

Volcanoes: Age-date pre-historic eruptions from volcanoes in Auckland and the central North Island to elucidate past behaviour and possible future threat.

Archaeology: Work with archaeologists in numerous countries in the study of pre-historic societies and early human settlement.

Antiquities: Age-date antiquities and detect fakes for museums and art dealers internationally.

Marine biology: Help in the study of life cycles of commercial fish species in New Zealand to aid fisheries management.

Oceanography: Help with research on circulation pathways and quantity of inorganic carbon in Southern Hemisphere oceans to monitor changes in ocean chemistry.

Atmosphere: Help with research on atmospheric circulation in the Southern Hemisphere. Work with NIWA to maintain a record of carbon-14 concentration in the atmosphere in the Southern Hemisphere that dates back to the early 1950s. Environment & climate research: Trace movement of carbon atoms through the environment to aid carbon accounting and thus enable the government and private sector to make informed decisions on how best to respond to the impact of, and adaptation to, climate change.

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