Optimizing illumination for full field imaging at high brilliance hard X-ray synchrotron sources

A new technique is presented to overcome beam size limitation in full field imaging at high brilliance synchrotron sources using specially designed refractive X-ray optics. These optics defocus the incoming beam in vertical direction and reshape the intensity distribution from a Gaussian to a more desirable top-hat-shaped profile at the same time. With these optics X-ray full-field imaging of extended objects becomes possible without having to stack several scans or applying a cone beam geometry in order to image the entire specimen. For in situ experiments in general and for diffraction limited sources in particular this gain in field of view and the optimization of the intensity distribution is going to be very beneficial.

Miniaturized compound refractive X-ray zoom lens

We introduce the concept of a miniaturized compound refractive X-ray zoom lens consisting of SU-8 lenses fabricated by deep X-ray lithography. The focal length can be varied by changing the number of lens elements placed in the beam. We use suitable actuators to move single lens elements reversibly out of the beam. The X-ray zoom lens can accept different X-ray energies while keeping a fixed working distance, or vary the focal distance for a fixed energy. The latter is useful in tuning the magnification factor in full field microscopy.

[Autosomal dominant polycystic kidney disease: should patients' young adult relatives be screened or not?]

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease, with a global prevalence of 10 per 10,000. It is characterized by the formation of numerous cysts in both kidneys, and leads to renal function loss; the majority of patients will eventually need renal replacement therapy. It is possible to screen patients' presymptomatic family members from a young age, but this has not historically been recommended as until recently there were no treatment options. This year, the vasopressin V2 receptor antagonist tolvaptan was approved for prescription in ADPKD, to slow the rate of renal function decline. The availability of this new treatment option, along with other factors such as the possible use of IVF procedures with pre-implantation genetic diagnosis, imply that we have to rethink the issue of presymptomatic screening. Young adults at-risk should be screened, to give them the chance to opt for treatment.

Note: Characterization of a high-photon-energy X-ray imager

The Bragg angle, rocking curve, and reflection efficiency of a quartz crystal x-ray imager (Miller indices 234) were measured at photon energy of 15.6909 keV, corresponding to the K(α2) line of Zr, using the X15A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory. One flat and three spherically curved samples were tested. The peak reflectivity of the best-performing crystal was determined to be (3.6 ± 0.7) × 10(-4) with a rocking-curve full width at half maximum of 0.09°. The Zr K(α2) emission was imaged from a hot Zr plasma generated by a 10-J multiterawatt laser.

Coupling of high-intensity laser light to fast electrons in cone-guided fast ignition

Cu wires attached to Al cones are used to investigate the energy coupling efficiency of laser light to fast electrons through a cone into a dense plasma. We present experimental and simulation results demonstrating the effect on the energy coupling of effectively placing the cone in a surrounding high density plasma as well as the effect of a large preformed plasma inside the cone. Thick cone walls, simulating plasma surrounding the cone in fast ignition, reduce the energy coupling by a factor of up to 4. An increase in prepulse inside the cone by a factor of 50 further reduces coupling by a factor of 3. Simulations with the pic code lsp that include the laser plasma interaction and the preformed plasma from the flash code show that electron refluxing in thin cone-wall targets enhances coupling to the wire. The implications for full-scale cone-guided fast ignition are discussed.

Effect of reentrant cone geometry on energy transport in intense laser-plasma interactions

The energy transport in cone-guided low- Z targets has been studied for laser intensities on target of 2.5x10(20) W cm(-2). Extreme ultraviolet (XUV) imaging and transverse optical shadowgraphy of the rear surfaces of slab and cone-slab targets show that the cone geometry strongly influences the observed transport patterns. The XUV intensity showed an average spot size of 65+/-10 microm for slab targets. The cone slabs showed a reduced spot size of 44+/-10 microm. The shadowgraphy for the aforementioned shots demonstrate the same behavior. The transverse size of the expansion pattern was 357+/-32 microm for the slabs and reduced to 210+/-30 microm. A transport model was constructed which showed that the change in transport pattern is due to suppression of refluxing electrons in the material surrounding the cone.

A dual-channel, curved-crystal spectrograph for petawatt laser, x-ray backlighter source studies

A dual-channel, curved-crystal spectrograph was designed to measure time-integrated x-ray spectra in the approximately 1.5 to 2 keV range (6.2-8.2 A wavelength) from small-mass, thin-foil targets irradiated by the VULCAN petawatt laser focused up to 4x10(20) W/cm(2). The spectrograph consists of two cylindrically curved potassium-acid-phthalate crystals bent in the meridional plane to increase the spectral range by a factor of approximately 10 compared to a flat crystal. The device acquires single-shot x-ray spectra with good signal-to-background ratios in the hard x-ray background environment of petawatt laser-plasma interactions. The peak spectral energies of the aluminum He(alpha) and Ly(alpha) resonance lines were approximately 1.8 and approximately 1.0 mJ/eV sr (approximately 0.4 and 0.25 J/A sr), respectively, for 220 J, 10 ps laser irradiation.

High-current, relativistic electron-beam transport in metals and the role of magnetic collimation

High-resolution coherent transition radiation (CTR) imaging diagnoses electrons accelerated in laser-solid interactions with intensities of approximately 10;{19} W/cm;{2}. The CTR images indicate electron-beam filamentation and annular propagation. The beam temperature and half-angle divergence are inferred to be approximately 1.4 MeV and approximately 16 degrees , respectively. Three-dimensional hybrid-particle-in-cell code simulations reproduce the details of the CTR images assuming an initial half-angle divergence of approximately 56 degrees . Self-generated resistive magnetic fields are responsible for the difference between the initial and measured divergence.

Optimizing electron-positron pair production on kilojoule-class high-intensity lasers for the purpose of pair-plasma creation

Expressions for the yield of electron-positron pairs, their energy spectra, and production rates have been obtained in the interaction of multi-kJ pulses of high-intensity laser light interacting with solid targets. The Bethe-Heitler conversion of hard x-ray bremsstrahlung [D. A. Gryaznykh, Y. Z. Kandiev, and V. A. Lykov, JETP Lett. 67, 257 (1998); K. Nakashima and H. Takabe, Phys. Plasmas 9, 1505 (2002)] is shown to dominate over direct production (trident process) [E. P. Liang, S. C. Wilks, and M. Tabak, Phys. Rev. Lett. 81, 4887 (1998)]. The yields and production rates have been optimized as a function of incident laser intensity by the choice of target material and dimensions, indicating that up to 5 x 10 (11) pairs can be produced on the OMEGA EP laser system [L. J. Waxer, Opt. Photonics News 16, 30 (2005)]. The corresponding production rates are high enough to make possible the creation of a pair plasma.

Bulk heating of solid-density plasmas during high-intensity-laser plasma interactions

K -shell x-ray spectroscopy is used to study the interaction of small-mass copper foil targets (>20x20x2microm;{3}) with a high-intensity (>10;{19}Wcm;{2}) laser pulse. Efficient bulk heating to greater than 200eV is demonstrated using collisional-energy transfer from recirculating fast electrons. K -photon yields and bulk-electron temperatures calculated by three-dimensional numerical target-heating simulations are in good agreement with the experimental measurements.

A high-resolution coherent transition radiation diagnostic for laser-produced electron transport studies (invited)

High-resolution images of the rear-surface optical emission from high-intensity (I approximately 10(19) W/cm(2)) laser illuminated metal foils have been recorded using coherent transition radiation (CTR). CTR is generated as relativistic electrons, generated in high-intensity laser-plasma interactions, exit the target's rear surface and move into vacuum. A transition radiation diagnostic (TRD) records time-integrated images in a 24 nm bandwidth window around lambda=529 nm. The optical transmission at lambda=1053 nm, the laser wavelength, is 15 orders of magnitude lower than the transmission at the wavelength of interest, lambda=527 nm. The detector is a scientific grade charge-coupled device (CCD) camera that operates with a signal-to-noise ratio of 10(3) and has a dynamic range of 10(4). The TRD has demonstrated a spatial resolution of 1.4 microm over a 1 mm field of view, limited only by the CCD pixel size.

Laser heating of solid matter by light-pressure-driven shocks at ultrarelativistic intensities

The heating of solid targets irradiated by 5 x 10(20) W cm(-2), 0.8 ps, 1.05 microm wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo, and V. A surface layer is heated to approximately 5 keV with an axial temperature gradient of 0.6 microm scale length. Images of Ni Ly(alpha) show the hot region has <or=25 microm diameter. These data are consistent with collisional particle-in-cell simulations using preformed plasma density profiles from hydrodynamic modeling which show that the >100 G bar light pressure compresses the preformed plasma and drives a shock into the solid, heating a thin layer.

Fat elimination from autologous blood

Bowl-based autotransfusion devices reduce the amount of fat found in shed blood, but cannot completely eliminate fat particles. When fat is seen on the surface of the processed blood, this blood should be filtered with a leukocyte removal filter before retransfusion.

Fat elimination during intraoperative autotransfusion: an in vitro investigation

Intraoperative autotransfusion of scavenged blood is an established method to reduce the need for perioperative homologous blood transfusion. However, if fat particles contaminate blood suctioned from the wound site, no reliable method is available to remove them during the washing and concentration of the recycled blood. A new generation of autotransfusion devices (e.g., continuous autotransfusion system [CATS]), based on separation chambers used in cell separators or plasmapheresis devices, allows continuous procession of the collected blood, in contrast with the discontinuous process used in conventional autotransfusion devices such as the Cell Saver 5. Theoretically, the continuous system should be more efficient than the discontinuous system in eliminating fat. Outdated, 36-day-old packed red blood cells, 600 mL, were mixed with 500 mL of lactated Ringer's solution and 200 mL of soya oil. Soya oil was used because it has a fatty acid composition similar to that of fat found in bone marrow. The blood mixture was then washed and concentrated by using either the CATS or the Cell Saver 5. Six samples were processed by each device. The CATS eliminated the soya oil (200 mL) completely, whereas the Cell Saver 5 delivered 30.3 +/- 7.8 mL soya oil into the retransfusion bag. The new generation of autotransfusion devices allows complete removal of fat particles.

IMPLICATIONS

Autotransfusion devices serve to wash and retransfuse blood scavenged from the wound site. However, they cannot completely remove fat particles. This in vitro investigation showed that a new device completely removes fat particles and thus prevents retransfusion of fat.

The conservation of mitochondrial function by ischaemia--the ischaemia paradox

The aim of this study was to compare oxidative phosphorylation of rat heart mitochondria, isolated: (i) immediately after excision of the heart; (ii) after 60 min of low flow normoxic perfusion; (iii) after 60 min of high flow normoxic perfusion;: (iv) after 30 min of no-flow ischaemia and (v) after 30 min ischaemia followed by 20 min reperfusion. The results, using a retrogradely perfused rat hart as a model, show that mitochondrial oxidative phosphorylation after 30 min of no-flow ischaemia showed no difference from oxidative phosphorylation measured on mitochondria isolated directly after excision of the heart. However, after 30 min no-flow ischaemia followed by 20 min of reperfusion, oxidative phosphorylation deteriorated in comparison with oxidative phosphorylation after 30 min of ischaemia only. Furthermore, oxidative phosphorylation after 60 min of non-ischaemic high flow perfusion (thus high coronary flow), compared better with oxidative phosphorylation after ischaemia-reperfusion than with oxidative phosphorylation after ischaemia alone.

Concomitant medial facet and dome fractures of the talus

Osteochondral fracture of the dome of the talus is a well known complication of an inversion injury of the ankle. Recently the authors encountered a patient having a talar dome fracture associated with intra-articular fracture of the medial facet after inversion injury of the ankle. The authors have been unable to find a medial facet intra-articular fracture reported in the English literature. The talar dome fragment was removed arthroscopically and the medial facet fragment was removed using an open surgical approach. The mechanism of injury and the operative approach are discussed.