ANALYTICAL AND LABORATORY EQUIPMENT11


facility on the I11 beamline (the only one in the world that has been specially designed for experiments that need to be monitored over long periods of time – months, or even years) the facility can run a long-term experiment on the formation of meridianiite. However, it needed a temperature-controlled environment, allowing for very slow cooling rates of around 0.3°C per day. Tis presented an engineering challenge. Although Diamond has a lot of temperature-controlled environments, they normally use a cryostat where the detector and the samples can be sealed in together. Tat won’t work on the LDE, where the detector needs to be free to move into position for each experiment. Diamond engineers Jon Kelly and


Andy Male solved this problem by designing a new cold cell for the LDE, which provides the necessary thermal insulation while remaining transparent to the X-ray beam. Tey went through a couple of design iterations for the cold cell, which needed to be small and light enough to move easily, with flexible connections. Te finished design is made from Palight insulating foam, which is durable and easy to engineer, with triple glazing of Kapton for the beam windows. Within the cold cell


Examining the slow in situ precipitation of meridianiite


is a copper block, through which cooled anti-freeze is circulated by a commercial chiller. Te small sample chambers have diamond windows that allow transmission of the X-ray beam


Te cold cell has been in use on the LDE for a year, and is still going strong. Te first results from the meridianiite study show that it’s an effective design for this


type of sub-zero temperature formation studies. Meridianiite formed by the fourth week of the experiment, between -7 and -8°C. Te relatively quick speed at which it formed and locked away water could well explain why we don’t see long-standing bodies of water on Mars. Te full results of the long-term study will be published in due course.


The Diamond Sample Manipulator M


any beamlines rely on a Sample Manipulator to hold samples securely in an X-ray beam less


than a tenth of a millimetre across, whilst also enabling them to move and rotate around multiple axes and rotate around each axis. The differing requirements of each beamline mean that the basic design of the Sample Manipulator is customised for each one. One assembly is required to


electrically isolate the sample from the support, enabling measurement of the low current pico amp (10-12A) signal from the X-rays hitting the sample. It also needs to provide enough thermal conductivity to lower the sample temperature to a few degrees above absolute zero. The solution to this particular engineering challenge lies in single crystal sapphire, which can be manufactured using a chemical vapour deposition (CVD) method to provide thin sections of


material with the thermal conductivity and high resistivity properties required. For heating samples up to 600°C it is


possible to use a resistive heating, but for higher temperatures up to 1,200°C an electron beam (e-beam) heater is required. E-beam heaters use the energy of electrons to deliver energy to a small spot. Electrons are accelerated by raising the voltage of the sample to +500V and passing current through a tungsten coil filament in close proximity with a free path to the back of the sample holder.


All of this needs to be fitted into a space not much larger than a pocket watch. The drive parts and fasteners used are selected from the minimum size a supplier can deliver,


and Diamond’s engineers are constantly searching for specialist materials that can make seemingly impossible combinations of requirements possible.


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