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The UK Smart X-Ray Optics (SXO) programme is developing active/adaptive optics for terrestrial applications. One of the technologies proposed is microstructured optical arrays (MOAs), which focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels. Although such arrays are similar in concept to polycapillary and microchannel plate optics, they can be bent and adjusted using piezoelectric actuators providing control over the focusing and inherent aberrations. Custom configurations can be designed, using ray tracing and finite element analysis, for applications from sub-keV to several-keV X-rays, and the channels of appropriate aspect ratios can be made using deep silicon etching. An exemplar application will be in the microprobing of biological cells and tissue samples using Ti Kα radiation (4.5 keV) in studies related to radiation-induced cancers. This paper discusses the optical design, modelling, and manufacture of such optics.

Piezoelectric actuators are widely utilised in adaptive optics to enable mirrors having an actively controlled reflective surface for the purpose of the wavefront correction by reducing the effects of rapidly changing optical distortion. Two new prototype adaptive X-ray optical systems are under development with the aim of approaching the fundamental diffraction limit. One proposed technology is microstructured optical arrays (MOAs) involving two or four piezoelectric strips bonded to a silicon wafer to produce a micro-focused X-ray source for biological applications, and which uses grazing incidence reflection through consecutive aligned arrays of channels obtained using deep silicon etching. Another technology is large scale optics which uses a thin shell mirror bonded with 20–40 piezoelectric actuators for the next generation of X-ray telescopes with an aim to achieve a resolution greater than that currently available by Chandra (0.5"). PZT-based piezoelectric actuators are being developed in this programme according to the design and implementation of the proposed mirror and array structures. Viscous plastic processing is chosen for the preparation of the materials system, which is subsequently formed and shaped into the suitable configurations. Precise controls on the thickness, surface finish and the curvature are the key factors to delivering satisfactory actuators. Unimorph type piezoelectric actuators have been proposed for the applications and results are presented regarding the fabrication and characterisation of such piezo-actuators, as well as the related design concepts and comparison to modelling work.

A soft X-ray scintillator phosphor (Gd2O2S:Pr) has been synthesised which is composed of discrete crystals of 120×150 nm average size. This material has been deposited onto a transparent substrate so that it can be used to detect X-rays generated by a laser generated plasma. A photodiode has then been used to quantify the intensity of emission by the phosphor slide. This nano-crystalline Gd2O2S:Pr phosphor shows greatly enhanced signal over a commercially available phosphor with larger particle size.

Aperiodic molybdenum/silicon broadband multilayer analyzers with constant reflectivity over a wide spectral range for a fixed incidence angle have been designed using a combined analytical/numerical method. The analyzers were fabricated using direct current magnetron sputtering and characterized using the soft X-ray polarimeter at the BESSY facility. Nearly constant s-reflectivity, up to 37%, is observed over the 15–17 nm wavelength range at a grazing incidence angle of 50°, and the degree of polarization is over 98%. Furthermore, the analyzer also exhibits high s-reflectivity and polarization over a broad angular range, 43–53°, at a fixed wavelength of 15.5 nm. This kind of broadband multilayer analyzer can be used in extreme ultraviolet polarization measurements, and will greatly simplify experimental arrangements.

Radiation microbeams represent a unique and powerful tool to study and quantify the effects of precise doses of radiation delivered with micron precision to selected biological samples. The Gray Cancer Institute has developed two independent but complementary micro-irradiation facilities, specifically developed for the targeted irradiation of cells and structured tissues; a charged-particle microbeam that uses collimated protons or helium ions and an ultra-soft X-ray microprobe. The ultra-soft X-ray facility employs a focused electron bombardments source to produce a near monochromatic C K X-ray beam. Highly efficient zone plates optimised for the appropriate wavelength are used to focus the characteristic X-rays into a sub-micron spot. The facility is also equipped with a three-axis micro-positioning stage, an epi-fluorescent UV microscope with intensified CCD camera coupled to a fast PC for a automatic, fast and accurate samples recognition and alignment with the probe. Recent experiments have been directed to investigate the bystander effect by irradiating only one cell within a population of V79 cells that are subsequently individually revisited for colony formation. A clear bystander effect has been detected (- 10 % reduction in survival) when a single cell has been irradiated. The effect is triggered by very low doses (∼ 100) mGy) and it is largely dose independent.

We are developing two independent, but complementary microbeams for irradiating cells individually in vitro. Firstly, a charged-particle microbeam that uses a fine-bore glass capillary, combined with a transmission detector to precisely irradiate cells with exact numbers of energetic charge-particles and secondly, a soft X-ray microprobe that produces a very fine beam of carbon-K (278 eV) ultrasoft X-rays, focused to a spot size

The Smart X-Ray Optics (SXO) project comprises a UK-based consortium developing active/adaptive micro-structured optical arrays (MOAs). MOA devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels. Adaptability is achieved using a combination of piezoelectric actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the edges of the chip with the active area at the centre, effectively amplifying the bend radius. The spider actuation concept, in combination with deep silicon etching stopped close to the surface, can also be used to create deformable mirrors where the curvature and tip/tilt angles of the mirror can be controlled. Finite Element Analysis (FEA) modelling, carried out for the optimization of the spider MOA device, indicates that deformable mirrors with curvature varying from flat to 5cm ROC and control over the tip/tilt angles of the mirror of +/-3mrad could be achieved. Test spider structures, manufactured using a Viscous Plastic Processing Process for the PZT piezoelectric actuators and a single wet etch step using planes in a (110) silicon wafer for both the silicon channels and the spider structure, have been bent to a radius of curvature smaller than 5 cm. This paper evaluates the spider MOA's concept as a means to achieve deformable mirrors with controllable ROC and control over the tip/tilt angles. FEA modelling results are compared with obtained characterization data of prototype structures. Finally, manufacturing and integration methods and design characteristics of the device, such its scalability, are also discussed.

The Smart X-Ray Optics (SXO) project comprises a U.K.-based consortium developing active/adaptive micro-structured optical arrays (MOAs). These devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels etched in silicon. Adaptability is achieved using a combination of piezoelectric actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the edges of the chip with the active area at the centre, effectively amplifying the bend radius. Test spider structures, have been bent to a radius of curvature smaller than 5 cm, indicating that in complete devices a suitable focal length using a tandem pair configuration could be achieved. Finite Element Analysis (FEA) modelling has been carried out for the optimization of the spider MOA device design. Prototype devices have been manufactured using a Viscous Plastic Processing technique for the PZT piezoelectric actuators, and a single wet etch step using {111} planes in a (110) silicon wafer for both the silicon channels and the spider structure. A surface roughness of 1.2 nm was achieved on the silicon channel walls. Characterisation techniques have been developed in order to evaluate the device performance in terms of the bending of the MOA channels produced by the actuators. This paper evaluates the progress to date on the development of spider MOA's comparing FEA modelling with the results obtained for prototype structures.

The Smart X-Ray Optics (SXO) project comprises a U.K.-based consortium developing active/adaptive micro-structured optical arrays (MOAs). These devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels etched in silicon. The silicon channels have been produced both by dry and wet etching, the latter providing smoother channel walls. Adaptability is achieved using piezoelectric actuators, which bend the device and therefore change its focal distance. We aim to achieve a 5 cm radius of curvature which can provide a suitable focal length using a tandem pair MOA configuration. Finite Element Analysis (FEA) modelling has been carried out for the optimization of the MOA device design, consider different types of actuators (unimorph, bimorph and active fibre composites), and different Si/piezoelectric absolute and relative thicknesses. Prototype devices have been manufactured using a Viscous Plastic Processing Process for the piezoelectric actuators and dry etched silicon channels, bonded together using a low shrinkage adhesive. Characterisation techniques have been developed in order to evaluate the device performance in terms of the bending of the MOA channels produced by the actuators. This paper evaluates the progress to date on the actuation of the MOAs, comparing FEA modelling with the results obtained for different prototype structures.

Piezoelectric actuators are widely employed in adaptive optics to enable an actively controlled mirror surface and improve the optical resolution and sensitivity. Currently two new prototype adaptive X-ray optical systems are under development through the Smart X-ray Optics project in a UK based consortium. One proposed technology is micro-structured optical arrays (MOAs) which uses aligned micro-channels structures obtained by deep silicon etching using both dry and wet techniques and bonded piezoelectric actuators to produce a micro-focused X-ray source for biological applications. The other technology is large scale optics which uses a thin shell mirror segment with 20-40 bonded piezo-actuators for the next generation of X-ray telescopes with an aim to achieve a resolution greater than that currently available by Chandra (0.5"). The Functional Materials Group of Birmingham University has the capability of fabricating a wide range of piezo-actuators including, for example, unimorph, bimorph and active fibre composites (AFC) by using a viscous plastic processing technique. This offers flexibility in customising the shapes (from planar to 3-D helix) and feature sizes (>20 μm) of the actuators, as well as achieving good piezoelectric properties. PZT unimorph actuators are being developed in this programme according to the design and implementation of the proposed mirror and array structures. Precise controls on the dimension, thickness, surface finishing and the curvature have been achieved for delivering satisfactory actuators. Results are presented regarding the fabrication and characterisation of such piezo-actuators, as well as the progress on the large optic and MOAs prototypes employing the piezo-actuators.

The Smart X-ray Optics (SXO) programme is developing advanced active-adaptive optics for X-rays. There are two main themes: large optics for applications in astronomy and small scale optics for micro-probing of biological cells and tissue samples using Ti or Cr Kα radiation (4.5keV and 5.4keV, respectively) in studies related to radiation induced cancers. For the latter objective, microstructured optical arrays (MOAs) have been proposed. These consist of an array of channels deep etched in silicon. They use grazing incidence reflection to focus the X-rays through consecutive aligned arrays of channels, ideally reflecting once off a channel wall in each array. Bending the arrays allows variable focal length. The adaptivity is achieved by flexing the arrays using PZT (Lead Zirconate Titanate)-based piezo actuators. The array bending has been modelled using finite element analysis (FEA) and the results showed that for reasonable efficiency, the wall roughness of the channels should not exceed 2nm. This paper describes two techniques of fabrication the MOAs: dry etching and wet etching. The first method requires a special equipment called "inductively coupled plasma" (ICP) using Bosch processes that are designed to produce features with a high aspect ratio with vertical walls. The second method involves using an alkaline solution for etching silicon wafers. This type of wafer was selected because of the large wet etch ratio between the (111) and (100) planes that leads to smooth vertical walls. For our application tetra-methyl-ammonium hydroxide (TMAH) was used as it is fully compatible with CMOS integrated circuit processes.

The UK Smart X-Ray Optics consortium is developing novel reflective adaptive/active x-ray optics for small-scale laboratory applications, including studies of radiation-induced damage to biological material. The optics work on the same principle as polycapillaries, using configured arrays of channels etched into thin silicon, such that each x-ray photon reflects at most once off a channel wall. Using two arrays in succession provides two reflections and thus the Abbe sine condition can be approximately satisfied, reducing aberrations. Adaptivity is achieved by flexing one or both arrays using piezo actuation, which can provide further reduction of aberrations as well as controllable focal lengths. Modelling of such arrays for used on an x-ray microprobe, based on a microfocus source with an emitting region approximately 1μm in diameter, shows that a focused flux approximately two orders of magnitude greater than possible with a zone plate of comparable focal length is possible, assuming that the channel wall roughness is less than about 2nm.

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.

In the foreseeable future silicon based electronics will reach limits in miniaturization and switching speeds, imposed by fundamental physical constraints. The quest for smaller gates and higher processing speeds with the attendant increase of chip functional density will reach the point where quantum effects dominate. Alternative strategies will then be required to overcome the limitations of silicon; among the most promising are those exploiting the properties of biological molecules, notably microtubules. These have the advantages associated with carbon chemistry, including the scope for constructing large highly complex macromolecular assemblies, and share the exciting electronic properties of semi- and superconductors. Biological systems have the potential to bypass the limiting effects of single particle quantum systems through the interactions of complex molecules, necessarily based on hydrocarbon polymers.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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).© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An Electron-Tubes-LTD 129EM electron multiplier tube has been modified to act as a detector of soft x-rays. The first dynodewas coated with lOOnm ofCsl and the assembly was mounted in a small vacuum chamber with lOOnm thick silicon nitrideentrance window. Initial tests show the detector is linear up to an input flux of-IMHz on a synchrotron source and has provedeffective in providing pulse height discrimination when used on a pulsed laser plasma source.Keywords: detector, soft x-rays, microscopy, electron, multiplier, synchrotron, laser-plasma 1. INTRODUCTION X-rays are typically detected by interactions that produce charged particles which are collected and their number amplified toform an electronic signal. Ideally, the interaction ofthe x-ray photon with the sensitive volume ofthe detector will produce manycharged particles resulting in an electronic signal which is considerably greater than the electronic noise in the system. Soft x-rayshave energies in the range 200 to 700eV and will generally produce a small number of charged particles. Where small numbers ofphotons are involved (as is often the case in soft x-ray microscopy), the detector will typically need an intrinsic amplificationprocess in order to produce an electronic signal of sufficient magnitude.Here we introduce a modified electron multiplier tube as a detector for both photon counting and pulse height analysisapplications in x-ray microscopy. Initial tests on synchrotron and laser plasma sources indicate that the prototype has some pulse-height non-linearity, but is both useful and competitive with existing scanning soft x-ray microscope detectors.

Two laboratory scale x-ray microscopes using laser generated plasma sources are being developed at King's College. One systemuses dark field imaging while the other is a scanning x-ray microscope and progress with both is described. In particular,preliminary results from an extensive characterisation of the laser plasma source at the Lasers for Science Facility, CLRCRutherford Appleton Laboratory, are discussed. This characterisation has shown that the source is eminently suitable for x-ray microscopy. Keywords: x-ray microscopy, laser generated plasma sources 1. INTRODUCTION In a laser generated plasma (LGP) source a high power pulsed laser beam is focused to a small spot on an appropriate target suchas Mylar or a metal. Such sources provide an attractive alternative to synchrotrons for various applications of soft x-rays, inparticular x-ray microscopy.' Both ofthe microscopes described here will use such a source, namely that at the Lasers for ScienceFacility at the CLRC Rutherford Appleton Laboratory (RAL), UK. In section 2, the design and current status ofa dark field x-raymicroscope (DFXM) are discussed, while in section 3 a scanning transmission x-ray microscope (SSXM) based on a scannedsource is described.The main advantages of LGPs, as compared to synchrotrons, are well knwn1 Briefly, these result from the relatively lowcost and small size of the lasers, meaning that such sources can be situated in users' own laboratories. This alleviates thedisadvantages associated with synchrotrons, i.e., remoteness, high cost and competition for beam time. In the past. the maindisadvantages of LGPs for x-ray microscopy have been their relatively low brilliances and their limited tunability. However, aswill be discussed in section 4, the LGP source at RAL can now approach in brilliance (albeit at selected wavelengths) secondgeneration synchrotrons such as the National Synchrotron Light Source at Brookhaven where much pioneering work on x-raymicroscopy has been carried out. Additionally, recent experiments carried out by the authors using metal targets have shown thatthe source can, in principle, offer tunability; these results will be discussed in a subsequent paper.

The structures of ultrathin sputtered Cr/C multilayers were determined by high-resolution transmission electron microscopy. The evolution of layer thickness errors, interdiffusion and interfacial roughness were simulated using time series models. The results show that with increasing of interdiffusion and roughness the multilayer thickness ratio changes, thereby influencing the optical performance. All structural parameters show good correlation with and influence adjacent layers. The system errors of the deposition equipment can also be evaluated by the models.

Understanding the structural properties of wood fibre composites, widely used in building and other applications, is an important area of research in devising robust new materials for a range of environmental conditions, including those encountered in developing countries. Wood fibre composites are prepared by mixing fibres with prescribed amounts of glue, but exactly where the glue distributes in relation to the fibre components is unclear. Characterisation of the bonding conditions has largely been a matter of trial and error, which is time consuming and imprecise. In soft x-ray spectromicroscopy experiments carried out at the NSLS, a range of wood fibre composites, with different glues and glue loadings, was studied in order to attempt to quantify the relative glue content in different components of the composite.

The polarization state of the BESSY UE56/1-PGM beamline radiation in the broad wavelength range of 12.7–15.5nm was measured using a molybdenum/silicon transmission phase retarder and a reflection analyzer with aperiodic multilayer interference structures, which can broaden the spectral response of these optical elements. The characteristics of the circular polarized undulator radiation, as well as the polarization properties of the two polarizing elements, were determined by a complete polarization analysis. Furthermore, the polarization of the radiation as a function of the undulator shift setting was also measured at the wavelength of 13.1nm by use of the broadband phase retarder-analyzer pair.

Experimental results on aperiodic broadband transmission molybdenum/silicon multilayer phase retarders for the extreme ultraviolet range are presented. The broadband phase retarders were designed using a numerical method and made using direct current magnetron sputtering on silicon nitride membrane. The polarization properties of these aperiodic transmission phase retarders have been investigated using the soft x-ray polarimeter at BESSY-II. The measured phase shift was about 42° in the wavelength range of 13.8–15.5nm, and the corresponding s-component transmission (Ts) decreased from 6% to 2% with increasing wavelength.

Broadband extreme ultraviolet molybdenum/yttrium aperiodic multilayer analyzers were designed for polarization experiments in 8.5–11.7nm wavelength range. The multilayer analyzers were made using direct current magnetron sputtering and characterized using the soft x-ray polarimeter at BESSY-II facility. Measured s reflectivities at the Brewster angle are 5.5% for a multilayer designed for 8.5–10.1nm wavelength range and 6.1% for one designed for 9.1–11.7nm. The multilayers also exhibit high polarization degree up to 98.79%. In addition, the multilayer was also measured over 38°–52° angular range at the fixed wavelength of 10.2nm and the mean s reflectivity is 6.2%.

Nonperiodic molybdenum/silicon broadband multilayer polarizers have been designed using numerical optimization algorithm and fabricated using direct current magnetron sputtering. Their performances have been characterized using the high precision eight-axis soft x-ray polarimeter at the BESSY facility. Different multilayers have measured s-polarized reflectivities of 27% at 13.1nm and higher than 15% over the wavelength range of 13–19nm. Nearly constant s reflectivity, up to 37%, is observed over the 15–17nm wavelength range, where the degree of polarization is more than 98%. Furthermore, these multilayer polarizers also show high s reflectivity and polarization over a broad angular range at fixed wavelength.