Silicon-based beam-alignment monitor tool keeps X-rays on track
The device, which incorporates the advanced silicon chip Medipix3 technology, will help scientists using Diamond to monitor the alignment of the micrometer-sized X-ray beams as they travel, first through the instrumentation that refines them and then on to the samples being studied with the intense synchrotron light produced by the facility’s 562m storage ring. The stability of the synchrotron radiation beams produced at Diamond is crucial to the success of experiments using smaller and smaller X-ray beams to analyse material or biochemical samples.
The Diamond Light Source, located near Oxford, UK, generates extremely intense pin-point beams of synchrotron light of exceptional quality ranging from X-rays, ultra-violet and infrared. For example Diamond’s X-rays are around 100 billion times brighter than a standard hospital X-ray machine.
The goal of the Lancelot X-ray Beam Position Monitor (XBPM) project has been to devise a ‘transparent’ instrument for measuring in real-time beam intensity, beam position, and the shape of the beam cross section, with better quality images and lower noise profiles than currently available systems. The project has successfully produced a device that can effectively provide live images of the beam without blocking it with highly absorbing media. This is of huge benefit as it gives scientists access to real-time information on the position of the incident beam, enabling them to identify issues that can arise with the X-ray optics.
Julien Marchal, Senior Detector Scientist at Diamond, explains, “The need for improved X-ray beam position control during experiments led us to set up the Lancelot XBPM project with the University of Manchester. The Manchester team had already demonstrated considerable success in the area of in situ beam imaging utilising a pinhole camera system based on commercial CCDs or CMOS sensors, which are similar to the imaging systems used by conventional commercial digital cameras. The idea behind our project was to replace the standard X-ray sensor used in this pinhole camera with the new X-ray photon counting pixel detector developed by the Medipix3 collaboration, which is led by CERN and to which Diamond is contributing together with several other synchrotrons and research organisations. The expertise of Roelof van Silfhout and his colleagues at UoM, coupled with our in-house detector team and access to the Medipix3 detector and Diamond’s B16 Test Beamline, has proved extremely fruitful. We now have a fully operational, portable, system that can be used in any experiments where accurate beam position control is required.”
In essence the device is a pinhole X-ray camera that makes images of the beam by recording the scattered radiation from thin, weakly scattering foils. A unique feature of the instrument is that it acts as a microscope, providing enlarged images with very detailed information of the impinging X-ray beam even for the micrometre-sized beams that are routinely available at Diamond.
Roelof van Silfhout, Reader from the School of Electrical and Electronic Engineering, led the Manchester side of the collaboration. Roelof adds, “This has been a really exciting project for my group because we’ve worked on the whole system; the electronics, the mechanical housing and the software interface for the users. Working with the Diamond team to design, build and commission an instrument that specifically meets their requirements, and will therefore benefit the scientists that use the facility, has been hugely rewarding. Our method of in situ or transparent X-ray beam imaging has been granted a patent in the UK (pending in the EU and US), and we look forward to continuing our relationship with Diamond and other synchrotrons in the future.”
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