Quantum Design Helium Recycler for SQUID Magnetometer
About the Instrument:
The new Quantum Design Helium Recycler removes this cost altogether. It has its own refrigerator and simply recycles the helium. “I’ve been trying for years to get this helium recycler” says Callaghan Innovation researcher Jeff Tallon, “and the business case for it is unbeatable.” The SQUID is a very sensitive instrument for measuring the strength and direction of magnetic fields in a material. It can detect extremely small fields as well as large fields up to 7 Tesla and has a very low noise level. The temperature can be held constant anywhere from 1.5 K (-271ºC) up to around 800 K (527ºC). The system allows you to measure properties such as magnetic susceptibility, the onset of superconductivity and super-fluid density. The team have built a little pressure cell that can be inserted inside the instrument for doing high pressure measurements up to around 14,000 times atmospheric pressure.
The SQUID is the only machine of its kind in the country and provides invaluable insights for a wide range of materials research. “Now that the basic operational cost has gone there will be more people using it,” Jeff says. At CI, Jeff has a number of projects with Grant Williams in the areas of strongly correlated materials, high temperature superconductors and spintronics – materials which allow control of the spin as well as the charge of electrons and could dramatically increase the power and capacity of computers. They are also working on some cheap magnetic materials that could be simply painted onto a surface. MacDiarmid chemist Sally Brooker from Otago University was a big supporter of this upgrade. SQUID measurements are a major part of her research into “spin cross-over materials” which change their magnetic properties as the temperature changes. Victoria physicist and Institute Principal Investigator Ben Ruck and his team are using the SQUID to characterise the materials they are developing for spintronics devices.
In the past MacDiarmid researchers who have wanted to use the SQUID just haven’t been able to afford it. From the goodness of his heart, Jeff made the SQUID freely available to some outside research groups but the running costs had to come from his own Marsden funding. At times the machine had to be turned off for weeks at a time to save money. The MacDiarmid funding has eased the situation and encouraged openness and collaboration amongst its users. Jeff is so grateful to have the helium recycler that he is happy to waive the small running costs and make the SQUID available for free. “There’s no point in charging,” he says. “There’s a small amount of helium used but it’s so transformed our capability having this purchase that we’re very happy to share it with others primarily within the Institute but also outside.”