The UK Smart X-Ray Optics programme is developing the techniques required to both enhance the performance of
existing X-ray systems, such as X-ray telescopes, while also extending the utility of X-ray optics to a broader class of
scientific investigation. The approach requires the control of the inherent aberrations of X-ray systems using an
active/adaptive method. One of the technologies proposed to achieve this is micro-structured optical arrays, which use
grazing incidence reflection through consecutive aligned arrays of channels. Although such arrays are similar in concept
to polycapillary and microchannel plate optics, they are more flexible. Bending the arrays allows variable focal length,
while flexing parts of them provides adaptive or active systems. Custom configurations can be designed, using ray
tracing and finite element analysis, for applications from sub-keV to several-keV X-rays. The channels may be made
using deep silicon etching, which can provide appropriate aspect ratios, and flexed using piezo actuators. An exemplar
application will be in the micro-probing of biological cells and tissue samples using Ti Kα radiation (4.5 keV) in studies
related to radiation induced cancers.
Cellular micro-irradiation is now seen as a potent method for understanding how radiations interact with living cells and tissues. The strength of this technique lies in its ability to deliver precise doses of radiation to selected individual cells in vitro, or to pre-selected targets within cells. We have recently developed a focused soft X-ray microprobe for targeting individual cells. The use of focused X-rays for this type of study is unique, and is being applied in a number of novel experiments. One important application is to study the so-called bystander effect where un-irradiated cells are seen to respond to signals from nearby irradiated cells. It is also being used as a sub-cellular probe to compare the effects of nuclear versus cytoplasmic targeting. Our facility uses a 0.4-0.8 mm diameter zone plate to focus soft X-rays to a sub-micron beam. This is then aimed at selected sub-cellular targets using rapid automated cell finding and alignment procedures. The zone plate images characteristic-K X-rays of carbon or aluminium, generated by focusing a beam of 5-10 keV electrons on to the appropriate target. The current arrangement will deliver about 10000 photons/sec to the focus (sufficient to irradiate several tens of cells per minute).
Progress with an x-ray microprobe for radiobiological studies is described. The instrument uses laboratory soft x-ray sources to give either continuum radiation or pulsed line radiation. A zone plate forms a fine probe from the x-ray beam which may be used to target individual cells or sub-cellular components with defined radiation doses. A preliminary experiment has shown a definite biological effect.
Ric Allott, I. C. Edmond Turcu, Nicola Lisi, John Spencer, Waseem Shaikh, Adam Whybrew, S. Wang, R. Donovan, K. Lawley, Kenneth Ledingham, Melvyn Folkard, Kevin Prise
Leading edge research in molecular dynamics, photoelectron spectroscopy, surface interactions and radiobiology has pushed forward the requirement for intense, pulsed, tunable sources of vacuum ultraviolet radiation. Presently, only synchrotron radiation sources are sufficiently bright for these applications. A bright, continuously tunable VUV beamline capable of delivering in excess of 1013 photons/sec/cm2/1nm BW 100 nm, 50 Hz repetition rate (BW equals (Delta) (lambda) /(lambda) is the bandwidth) to the sample, has been constructed on a plasma source generated by a high repetition rate, picosecond KrF excimer laser system.
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