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Laboratory of Molecular Biophysics
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In July 2003 we tendered for a new microfocus X-ray generator funded largely by the Wellcome Trust but also with help from the Equipment Fund of the University of Oxford. The Bruker MicroStar was ordered on 20/12/03 and installed in T3 on 8/6/04. The generator was supplied with Montel optics on both the left and right ports. X-rays were produced on 9/6/04, less than 24 hours after the beginning of the installation.
The new generator has a maximum operating power of 2.7 kW. Measurements carried out by Robin Owen using a photodiode calibrated at the ESRF indicate a photon flux at 80% maximum power (40kV / 55mA) of 7.24 x 108 photons s-1, almost 3-fold higher than the 2.5 x 108 photons s-1 measured for the RU200H in T5 operating at maximum power. The attached Montel multilayer optics produce a beam of cross section 150 x 150 µm2 at the sample. This small beam size in combination with the higher flux noted above should now facilitate the in-house study of the increasing number of small crystal samples which we are obtaining from robot crystallisation trials.
The RU200H generator ('Myrtle') with a Mar345 imaging plate detector and Osmic Optics in T5 ran very smoothly this year. The anode annual rebuild was carried out by us on August 5th without incident. Users included numerous members of the LMB and OCMS, and Dr. Arzhang Ardavan's correlated electron systems group from the Clarendon Laboratory collaborating with Robin Owen and Elspeth Garman to investigate the effects of radiation damage on organic superconductors.
The RU200H in T3, which had been used since 1991 and run for around 76,685 hours, was decommissioned in April 2004 by Rigaku/MSC engineers. It was donated to the National University of Mexico in Cuernavaca, and will be reinstalled there. The removal and transportation were carried out by Import Export Services of Bristol, who were extremely efficient and professional. To obtain a Safety Certificate of Compliance prior to donation, the generator had to run for 15 minutes at full power (60kV and 90mA) before being dismantled. It is a tribute to the robust technology of rotating anode generators that this was achieved after 12 years of running.
The false floor in T3 was then removed and a new lino floor fitted with up the wall coving to give the room Biological category 2 status and allow diffraction experiments on virus crystals in the future.
The Dunn School of Pathology decommissioned their X-ray equipment in November 2004 and kindly donated their Mar345 Imaging plate detector (plus their 600 series Oxford Cryostream and blue Osmic mirrors) to us. We have installed the detector on the right side of the MicroStar, and are thus leaving the T5 facility intact for the moment.
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