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PubMed2002

Observation of broadband self-amplified spontaneous coherent terahertz synchrotron radiation in a storage ring.

Bursts of coherent synchrotron radiation at far-infrared and millimeter wavelengths have been observed at several storage rings. A microbunching instability has been proposed as the source for the bursts. However, the microbunching mechanism has yet to be elucidated. We provide the first evidence that the bursts are due to a microbunching instability driven by the emission of synchrotron radiation in the bunch. Observations made at the Advanced Light Source are consistent with the values predicted by the proposed microbunching model. These results demonstrate a new instability regime for high energy synchrotron radiation sources and could impact the design of future sources.

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PubMed2003

Brilliant, coherent far-infrared (THz) synchrotron radiation.

A new technology for generating steady state, brilliant, broadband, coherent, far-infrared (FIR) radiation in electron storage rings is presented, suitable for FIR spectroscopy. An FIR power increase of up to 100 000 compared to the normal, incoherent synchrotron radiation in the range of approximately 5 to approximately 40 cm(-1) could be achieved. The source is up to 1000 times more brillant compared to a standard Hg arc lamp. The coherent synchrotron radiation is produced in a "low alpha" optics mode of the synchrotron light source BESSY, by bunch shortening and non-Gaussian bunch deformation.

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PubMed2006

New formulation of the equation for synchrotron oscillations.

We develop an orbit theory for synchrotron oscillations using the orbit length, , as an independent variable. This is commonplace for static magnetic fields (storage rings). We extend this to the case of adiabatically varying magnetic fields (synchrotrons). Contrary to conventional treatments, betatron acceleration terms appear in both the energy and phase equations. We derive one-turn difference equations in the linear and adiabatic approximations. By a smooth approximation instead of the traveling-wave approximation, and by combining the two equations, we obtain a differential equation where the betatron acceleration terms are canceled. This equation is an extension of McMillan's equation to the case of strong-focusing synchrotrons.

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PubMed2000

Visualization, quantification and therapeutic evaluation of angiogenic vessels in cancer by synchrotron microangiography.

The usefulness of a synchrotron microangiography system for depicting, quantitating and therapeutically evaluating angiogenic vessels in cancer is illustrated. In 20 mice transplanted with murine colon cancer, sequential changes in the angiogenic vessels were determined by using synchrotron microangiography, using changes in tumor volume for reference. This system allowed the depiction and quantification of angiogenic vessels in the period from one to four weeks after transplantation. The effects of antiangiogenic therapy were evaluated by using a neutralizing antibody against vascular endothelial growth factor. The neutralizing antibody partially suppressed angiogenesis and tumor growth. Synchrotron microangiography is shown to be useful for the depiction, quantification and evaluation of angiogenic vessels in cancer.

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PubMed2003

Development of a one-dimensional detector for the study of explosions with a synchrotron radiation beam.

Investigations of fast dynamic processes with the help of synchrotron radiation allow an understanding of the properties of short-lifetime states of materials at very high temperatures and pressures. Detectors for such studies have to be able to detect X-ray photons from each electron bunch separately with a position resolution of about 0.1 mm. A prototype of a detector (DIMEX) for the imaging of explosions at a synchrotron radiation beam is described here. A spatial resolution of approximately 300 micro m and a time resolution of approximately 100 ns is demonstrated with a synchrotron radiation beam from the VEPP-3 2 T wiggler at an electron beam energy of 2 GeV. Results of the first projective imaging and SAXS experiments are presented.

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PubMed2005

An internet-based synchrotron experiment for students measuring the X-ray magnetic circular dichroism of a PtFe alloy.

A new internet-based synchrotron experiment for students is presented. A polarimeter and computer software have been developed for measuring via the internet the X-ray magnetic circular dichroism of PtFe around its Pt L(II) and L(III) absorption edges. From the experiment, students can examine the X-ray magnetic circular dichroism of a thin PtFe foil utilizing circular-polarized synchrotron radiation emitted by the superconducting asymmetric wiggler at the synchrotron radiation source DELTA of the University of Dortmund.

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PubMed1994

Computing for synchrotron radiation experiments.

Computing provision is of major concern to synchrotron radiation researchers. An overview is presented of the computing facilities for synchrotron radiation work at the Synchrotron Radiation Source, Daresbury Laboratory. Data acquisition, reduction and analysis are seen as an integrated activity essential for full utilization of beam time. We discuss the evolution of data-acquisition systems from stand-alone systems of limited computing power, to a unified project computing village using state-of-the-art equipment for combined-technique, high-data-rate experiments. A brief account of software packages for data reduction and analysis is also given.

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PubMed1995

In Situ Detection of Surface SiH(n) in Synchrotron-Radiation-Induced Chemical Vapor Deposition of a-Si on an SiO(2) Substrate.

The sensitivity and linearity of infrared reflection absorption spectroscopy (IRAS) has been significantly improved by using a buried-metal-layer (BML) substrate having an SiO(2)(15 nm)/Al(200 nm)/Si(100) structure, instead of a plain Si(100) substrate. By applying this BML-IRAS technique to the in situ observation of synchrotron-radiation-induced chemical vapor deposition of amorphous Si (a-Si) on an SiO(2) surface using Si(2)H(6) gas, the vibrational spectra of surface SiH(n) species in this reaction system have been observed for the first time with sufficient sensitivity for submonolayer coverage. The main silicon hydride species after deposition at 423 K are surface SiH(2) and SiH. Surface SiH(3) and SiH(2) are observed to be easily decomposed by synchrotron radiation irradiation. The decomposition rate of SiH by synchrotron radiation irradiation is much slower than those of SiH(2) and SiH(3).

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PubMed1996

Applications of synchrotron radiation to defect characterization and pendellösung fringe-spacing measurement in a natural diamond.

A small polished rectangular block of natural diamond unusually free from impurity zoning was examined by birefringence and synchrotron X-ray topography to map internal defects and assess effects of some accidental mechanical damage. ;Orthogonal-view' projection topographs facilitated comparisons between optical and X-ray images. Speedy and precise positioning of crystal sections cut in synchrotron X-ray section topographic studies was aided by radiographic and fluoroscopic procedures, which are described. Several X-ray reflection and refraction phenomena are illustrated, including high-contrast refraction images of crystal edges, chipping and crack outcrops. It was demonstrated that by combining optical and X-ray goniometry it was possible to record Pendellösung fringe systems employing precisely selected X-ray wavelengths in well defined crystal volumes. Valuable gain in fringe visibility resulted from the use of pure sigma-mode polarized synchrotron radiation. Absolute values of the diamond 004 structure factor were derived from five fringe systems measured, the findings (in upward order) being 11.7, 11.7, 12.0, 12.5, 12.6. Their scatter greatly exceeds the uncertainty in the measurement procedure (believed to be within +/-1%) and is attributed to different strain distributions within the five volumes sampled.

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PubMed1997

Tantalus, a 240MeV Dedicated Source of Synchrotron Radiation, 1968-1986.

Tantalus was a 240 MeV electron storage ring completed and commissioned in 1968. It was the first storage ring operated exclusively for the production of synchrotron radiation, although it was not designed for that purpose. As such, it influenced the operating pattern for subsequent dedicated sources of synchrotron radiation. Pioneering experiments using synchrotron radiation were carried out on this machine, and innovative instrumentation was produced there. It ceased operation in 1986.

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PubMed1997

Synchrotron Radiation Research in the UK.

The origins, development and growth of synchrotron radiation science and technology in the UK, and an account of the expansion of the synchrotron radiation research programme, its highlights, current activities and the prospects for the future expansion of synchrotron radiation activities within the UK, are presented.

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PubMed1997

Early work with synchrotron radiation at stanford.

The use of synchrotron radiation in the soft and hard X-ray spectral region received major impetus with the start of parasitic operation of the Stanford Synchrotron Radiation Project (SSRP) in 1974. This was the first time that synchrotron radiation from a multi-GeV electron storage ring was made available in a user facility for studying the structure of matter. Here we review the early work at SSRP as well as the activities that preceded it, highlighting the scientific accomplishments (soft X-ray photoemission, EXAFS, protein crystallography), beamline instrumentation developments and source improvements. The early work using bending-magnet radiation led to the funding of several dedicated facilities in the US and elsewhere in the world - the so-called second-generation light sources. Early work with wiggler and undulator insertion devices led to funding of third-generation sources better optimized for insertion device sources, particularly undulators.

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PubMed1998

Beam commissioning of the SPring-8 synchrotron.

The beam commissioning of the SPring-8 synchrotron was started in December 1996. In the first ten days, the coarse tuning of the pulse magnets for beam injection from the linac, and the excitation pattern of the dipole and the quadrupole magnets, were accomplished during energy ramping of the beam. The acceleration of the beam up to 8 GeV proceeded smoothly. From January to February 1997, the fine-tuning of the synchrotron was continued and the operating parameters of all of the synchrotron equipment were decided.

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PubMed1998

Experiments with very high energy synchrotron radiation.

The use of synchrotron radiation with very high photon energies has become possible only with the latest generation of storage rings. All high-electron-energy synchrotron sources will have a dedicated program for the use of very high photon energies. The high-energy beamline ID15 at the ESRF was the first beamline built and dedicated to this purpose, and it has now been in user operation for more than three years. The useful energy range of this beamline is 30-1000 keV and the superconducting insertion device for producing the highest attainable photon energies is described in detail. The techniques most often used today are diffraction and Compton scattering; an overview of the most important experiments is given. Both techniques have been used in the investigation of magnetic systems, and, additionally, the high resolution in reciprocal space, which can be achieved in diffraction, has led to a series of applications. Other fields of research are addressed, and attempts to indicate possible future research areas of high-energy synchrotron radiation are made.

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PubMed1998

Spectroscopic Techniques using Synchrotron Radiation and Free-Electron and Conventional Lasers.

Considerable progress in the investigation of the electronic and vibrational properties of atoms, molecules, materials, surfaces and interfaces has been achieved by combining different photon sources of complementary characteristics. In this paper some experimental results obtained recently at LURE by using two synchronized sources, such as the IR free-electron laser (FEL) CLIO, the VUV storage ring FEL, synchrotron radiation and table lasers, are presented. Using CLIO synchronized with a YAG laser allows the investigation of the vibrational properties of adsorbed species by the non-linear optical technique of visible-IR sum (difference) frequency generation, as shown for the adsorption of hydrogen on platinum in the electrochemical environment. The second result reported here relates to the study of the intersubband stimulated emission in GaAs/GaAlAs quantum wells by pump-probe experiments using the two-colour configuration of CLIO. The combination of a mode-locked Ar(+) laser and synchrotron radiation has been used for investigations in a pump-probe arrangement of the ionization of Xe atoms via the resonant state Xe* 5p(5)5d [3/2](1). The final example is a time-resolved core-level spectroscopy study of photoexcited Si(111) 2 x 1 surfaces by using a combination of the naturally synchronized UV storage ring laser and synchrotron radiation.

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PubMed2000

Generation of femtosecond pulses of synchrotron radiation

Femtosecond synchrotron pulses were generated directly from an electron storage ring. An ultrashort laser pulse was used to modulate the energy of electrons within a 100-femtosecond slice of the stored 30-picosecond electron bunch. The energy-modulated electrons were spatially separated from the long bunch and used to generate approximately 300-femtosecond synchrotron pulses at a bend-magnet beamline, with a spectral range from infrared to x-ray wavelengths. The same technique can be used to generate approximately 100-femtosecond x-ray pulses of substantially higher flux and brightness with an undulator. Such synchrotron-based femtosecond x-ray sources offer the possibility of applying x-ray techniques on an ultrafast time scale to investigate structural dynamics in condensed matter.

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PubMed2002

Lack of cell death enhancement after irradiation with monochromatic synchrotron X rays at the K-shell edge of platinum incorporated in living SQ20B human cells as cis-diamminedichloroplatinum (II).

In this paper we describe the results of experiments using synchrotron radiation to trigger the Auger effect in living human cancer cells treated with a widely used chemotherapy drug: cis-diamminedichloroplatinum (II) (cisplatin). The experiments were carried out at the ID17 beamline of the European Synchrotron Radiation Facility, which produces a high-fluence monochromatic beam that is adjustable from 20 to 80 keV. Cisplatin was chosen as the carrier of platinum atoms in the cells because of its alkylating-like activity and the irradiation was done with monochromatic beams above and below the platinum K-shell edge (78.39 keV). Cell survival curves were comparable with those obtained for the same cells under conventional irradiation conditions. At a low dose of cisplatin (0.1 microM, 48 h), no difference was seen in survival when the cells were irradiated above and below the K-shell edge of platinum. Higher cisplatin concentrations were investigated to enhance the cellular platinum content. The results with 1 microM cisplatin for 12 h showed no difference when the cells were irradiated with beams above or below the platinum K-shell edge with the exception of the higher cell death resulting from drug toxicity. The intracellular content of platinum was significant, as measured macroscopically by inductively coupled plasma mass spectrometry. Its subcellular localization and particularly its presence in the cell nucleus were verified by microscopic synchrotron X-ray fluorescence. This was the first known attempt at K-shell edge photon activation of stable platinum in living cells with a platinum complex used for chemotherapy. Its evident toxicity in these cells leads us to put forth the hypothesis that cisplatin toxicity can mask the enhancement of cell death induced by the irradiation above the K-shell edge. However, K-shell edge photon activation of stable elements provides a powerful technique for the understanding of the biological effects of Auger processes. Further avenues of development are discussed.

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PubMed1984

X-ray diffraction studies of tibial plateau cartilage using synchrotron radiation.

X-ray diffraction studies of articular cartilage have been performed using X-rays from two sources: a conventional generator and synchrotron radiation. Blocks of tissue from the tibial plateaux of pigs and dogs were examined to find the orientations of collagen fibrils throughout their depth. Analysis of the resulting diffraction patterns revealed a zonal arrangement of fibrils in both pig and dog tissue. At the articular surface the preferred orientation of fibrils was parallel to the surface, below this was a zone with no obvious preferred orientation and the remaining tissue had fibrils oriented mainly perpendicular to the surface. Using a conventional source of X-rays the exposure time for a single diffraction pattern was a number of days but this was reduced to about 10 min using the more intense synchrotron radiation. This improvement in exposure time facilitates the examination of small areas of tissue. X-ray diffraction using the synchrotron source offers a quick method of determining collagen fibril orientations in small areas of articular cartilage.

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