Ceramic motor system supplied for I12 JEEP beamline

Heason Technology has recently supplied a two metre travel, high-vacuum compatible ceramic motor system to Diamond Light Source for the I12 JEEP (Joint Engineering, Environmental and Processing) beamline. Capable of positioning within a 50 nanometre resolution over the full travel range and with speeds up to 80mm per second, the linear motor is used in a specially built cryo-cooled Laue monochromator, helping to deliver high-energy X-rays for a variety of exciting scientific experiments.

The I12 beamline which is currently being commissioned, is somewhat different in concept to other beamlines at the UK's national synchrotron facility in that it has two in-line experimental hutches rather than a single area where samples are analysed. The first hutch (EH1) is in the main Diamond Experimental Hall whilst the second hutch (EH2) is in a large purpose-built external building. The widely adjustable beam energy range (from 50 keV to 150 keV), which is due to the Lau© monochromator, allows a very broad range of applications including imaging and tomography, X-ray diffraction and small angle X-ray scattering. Furthermore the second hutch is able to accommodate exceptionally large-scale engineering and processing experiments which could involve for instance, fully assembled structures such as complete aircraft engines undergoing detailed creep-fatigue testing during high temperature cycling or historical artefact analysis which preserves the complete and possibly priceless object.

The Lau© monochromator was designed and built by the I12 beamline team at Diamond. The photograph (fig1) details the construction during build with the vacuum cover removed showing the fixed (1) and moving (2) silicon crystals and approximate position and direction of the X-ray beam passing through them. Bending of the individual crystals increases the energy bandwidth and available flux, which is useful for imaging experiments. For diffraction experiments, the crystals can be adjusted to use different diffraction planes, providing a narrower bandwidth and better energy resolution. The Heason supplied ceramic motor system provides the full translation of the crystal (2) along the beam over a two metre travel range, positioning the stack of equipment that is used to bend the second crystal to achieve the desired characteristics. A second pair of Heason supplied ceramic motors also translates the crystal and bending stack orthogonally across the beam with a 200mm travel range. One of the primary reasons for selecting ceramic motor technology for this application is the motors' inherent stability - with power removed the motor locks and holds its position completely with no drift, removing a potential vibration source which is critical to the monochromator's performance.

The long travel axis motor comprises two pairs of HR8 ceramic motors from Heason's distribution partner Nanomotion; arranged in pairs and interacting with ceramic drive strips on either side of the beam. The motor was installed by the Diamond beamline team with linear motion guide bearings and a tape-style optical encoder system with a 50 nanometre resolution. The two metre drive strips are an intrinsic part or the motor system ensuring smooth motion and optimal performance. For such long travel requirements the ceramic material is bonded to a steel strip for maximum durability.

The total mass acting on the ceramic motor system is in the order of 25kg and a force of 128N was specified to move the load at the desired speeds of up to 80mm/sec. Another specification for the ceramic motor included operation in vacuum up to 10-10 Torr.

The HR-8 ceramic motor is a compact high precision ceramic motor with a maximum speed capability to 250mm/sec. 32 N of force It can be supplied in high vacuum or ultra high vacuum versions for operation at 10-10 Torr. Heason also supplied Nanomotion AB1a Driver Amplifiers for this application.