Synchrotron Storage Research Articles

Time-domain sampling of x-ray pulses using an ultrafast sample response

We employ the ultrafast response of a 15.4 nm thin SrRuO3 layer grown epitaxially on a SrTiO3 substrate to perform time-domain sampling of an x-ray pulse emitted from a synchrotron storage ring. Excitation of the sample with an ultrashort laser pulse triggers coherent expansion and compression waves in the thin layer, which turn the diffraction efficiency on and off at a fixed Bragg angle during 5 ps. This is significantly shorter than the duration of the synchrotron x-ray pulse of 100 ps. Cross-correlation measurements of the ultrafast sample response and the synchrotron x-ray pulse allow to reconstruct the x-ray pulse shape.

Observation of Picometer Vertical Emittance with a Vertical Undulator

Using a vertical undulator, picometer vertical electron beam emittances have been observed at the Australian Synchrotron storage ring. An APPLE-II type undulator was phased to produce a horizontal magnetic field, which creates a synchrotron radiation field that is very sensitive to the vertical electron beam emittance. The measured ratios of undulator spectral peak heights are evaluated by fitting to simulations of the apparatus. With this apparatus immediately available at most existing electron and positron storage rings, we find this to be an appropriate and novel vertical emittance diagnostic.

Fastin situphase and stress analysis during laser surface treatment: A synchrotron x-ray diffraction approach

An in situ stress analysis by means of synchrotron x-ray diffraction was carried out during laser surface hardening of steel. A single exposure set-up that based on a special arrangement of two fast silicon strip line detectors was established, allowing for fast stress analysis according to the sin(2)ψ x-ray analysis method. For the in situ experiments a process chamber was designed and manufactured, which is described in detail. First measurements were carried out at the HZG undulator imaging beamline (IBL, beamline P05) at the synchrotron storage ring PETRA III, DESY, Hamburg (Germany). The laser processing was carried out using a 6 kW high power diode laser system. Two different laser optics were compared, a Gaussian optic with a focus spot of ø 3 mm and a homogenizing optic with a rectangular spot dimension of 8 × 8 mm(2). The laser processing was carried out using spot hardening at a heating-/cooling rate of 1000 K/s and was controlled via pyrometric temperature measurement using a control temperature of 1150 °C. The set-up being established during the measuring campaign allowed for this first realization data collection rates of 10Hz. The data evaluation procedure applied enables the separation of thermal from elastic strains and gains unprecedented insight into the laser hardening process.

Lifetime broadening of core-excited and -ionized states

Natural line widths are measurable fundamental quantities of quantum states that, in atoms and molecules, characterize the lifetime of the electronic states and therefore carry information about electronic structure and transition matrix elements. For core-levels, their determination is based on various types of spectroscopic measurements such as the photoabsorption or the photoelectron spectroscopy for core-excited and core-ionized states, respectively. The values reported in the literature used to change over the years owing to the improvement of the experimental accuracy available at synchrotron storage rings. We report here, in a broad energy range, the natural line widths for a series of core-levels in atoms (Kr3d, Ar2p, Xe3d) and molecules (S2p in CH3SSCH3, B1s in BF3, Cl2p in HCl, C1s in CO, C2H2, CH4 and CF4, N1s in N2, O1s in O2, CO and CO2), based on ultrahigh resolution total ion yield or X-ray photoelectron spectroscopy (XPS) measurements at the PLEIADES beamline at SOLEIL synchrotron (France). These newest measurements of the lifetime broadening of core levels are compared with previously published experimental results.

Recent advances in imaging of properties and growth of low dimensional structures for photonics and electronics by XPEEM

Spectroscopic Photoemission and Low Energy Electron Microscopy (SPELEEM) is a very powerful and diverse microscopy technique for the investigation of surfaces, interfaces, buried layers and nanoscale objects like nanoparticles and nanowires. The many significant results from photoemission Electron microscopy (PEEM) in recent years are linked with the exploitation of advanced light sources such as synchrotrons and new advanced laser systems. Combined also with low energy electron microscopy (LEEM) it allows a complementary chemical and structural analysis making LEEM/PEEM a versatile multitechnique instrument. To illustrate the extreme diversity, we give a summary of the recent studies with the SPELEEM installed at the soft X-ray beamline I311 at the MAXII synchrotron storage ring and a portable electrostatic PEEM used with ultra-fast XUV laser technology. The examples cover topics such as full-cone 3D band mapping by using the photoelectron diffraction mode of the microscope, growth mechanism and detailed doping profile of III–V nanowires, growth and intercalation of graphene on SiC substrates, droplet dynamics on GaP(111) surface, surface chemistry and control of nanostructure fabrication. Moreover, the first results of PEEM experiments using extreme ultraviolet attosecond pulse trains are discussed.

Beam dynamics issues and synchrotron radiation on TAC-SR

The Turkish Accelerator Center Synchrotron Radiation, TAC-SR, is the first project for accelerator based synchrotron and applied researches supported by Turkish Republic Ministry of Development (TRMOD). This initiative taken by the Turkish Government aims at the construction of advanced research infrastructures based on particle accelerators, considered an important asset to support and foster the national research in science and technology. In this framework, the primary objective of the TAC-SR working group is to produce the preliminary design of the Synchrotron Radiation Source. Achieved beam emittance of the studied design is nominally 1.18nm. Also, the frequency map analysis and the dynamic aperture calculations for the TAC Synchrotron Storage Ring are optimised. For demonstration, parameter sets and performance of some undulators are presented. It is seen that the insertion devices with the proposed parameter sets acquire competitive brilliance values to cover from 10eV to 50keV photon energy range.

X-ray grating interferometer for materials-science imaging at a low-coherent wiggler source

X-ray phase-contrast radiography and tomography enable to increase contrast for weakly absorbing materials. Recently, x-ray grating interferometers were developed that extend the possibility of phase-contrast imaging from highly brilliant radiation sources like third-generation synchrotron sources to non-coherent conventional x-ray tube sources. Here, we present the first installation of a three grating x-ray interferometer at a low-coherence wiggler source at the beamline W2 (HARWI II) operated by the Helmholtz-Zentrum Geesthacht at the second-generation synchrotron storage ring DORIS (DESY, Hamburg, Germany). Using this type of the wiggler insertion device with a millimeter-sized source allows monochromatic phase-contrast imaging of centimeter sized objects with high photon flux. Thus, biological and materials-science imaging applications can highly profit from this imaging modality. The specially designed grating interferometer currently works in the photon energy range from 22 to 30 keV, and the range will be increased by using adapted x-ray optical gratings. Our results of an energy-dependent visibility measurement in comparison to corresponding simulations demonstrate the performance of the new setup.

Dosimetry of intensive synchrotron microbeams

Abstract Intensive synchrotron X-ray microbeams form an integral part of microbeam radiation therapy (MRT). MRT is a novel radiation medicine modality being developed for inoperable and otherwise untreatable brain tumours. The extremely high dose rate (∼20 kGy/s), laterally fractionated radiation field and steep dose gradients utilized in this therapy make real-time dosimetry a significant challenge. In order for this treatment to advance to the clinical trial stage of development real-time dosimetry systems must be developed. This paper demonstrates the capabilities of a new dosimetry system based on an epitaxial silicon detector. The system combines high spatial resolution and real-time readout and we have measured the lateral dose profile of the MRT radiation field which incorporates 59 X-ray microbeams. All microbeam peaks and valley regions between two microbeams are clearly resolved. The measured detector response at any point is reproducible to within 0.5% after scaling for the known synchrotron storage ring beam current lifetime. The variation of the lateral dose profile at different depths in a PMMA phantom has been measured with the results compared to those from Penelope Monte Carlo simulations. The trend in the measured response with depth agrees with the simulation data (within the experimental variation of the central five microbeams peaks and valleys measured). However the measured peak-to-valley ratio response is a factor of 4.5 ± 0.1 times lower than that expected. The disagreement was further investigated and shown to be contributed to by charge recombination effects at the low bias voltages used.

Neutron laminography—a novel approach to three-dimensional imaging of flat objects with neutrons

Abstract Computed tomography (CT) is a three-dimensional (3D) imaging method which, for compact or prolate (i.e. rather isotropically extended around the rotation axis) specimens, can yield artefact-free reconstructed cross-sections. Laterally extended specimens like plate-like objects, however, are much less amenable to CT since reliable projection data cannot be acquired from angles where the plate is oriented parallel to the irradiation direction. To overcome this drawback, computed laminography (CL) was introduced recently to imaging set-ups at synchrotron storage rings. Here, we report on the first implementation of computed laminography with neutron radiation, showing measurements that were performed at the ANTARES neutron imaging facility at the FRM II research reactor of Technische Universitat Munchen. In general, neutrons are highly interesting probes for imaging since they provide a sensitivity to chemical elements very different from X-rays, yielding complementary information about the specimens investigated. Like for X-ray laminography, we avoid the projection directions where the beam is parallel to the long extensions of the specimen. We accomplish this by tilting of the rotation axis with respect to the transmitted-beam to an angle smaller than 90° (which would be the limiting case of CT) and roughly aligning the specimen's surface normal parallel to this rotation axis. The principles of neutron laminography are introduced and first test experiments are described.

Achievement of ultralow emittance coupling in the Australian Synchrotron storage ring

I. INTRODUCTIONThe Australian Synchrotron is a newly operating 3rdgeneration light source facility located in Melbourne,Australia. The 3 GeV storage ring is 216 meters in circum-ference and can store a beam of up to 200 mA current. Astorage ring design overview can be found in [1].The storage ring is a modified Chasman-Green–typelattice, designed for a horizontal emittance of 14 nmradwith dispersion free straights. For user operations a hori-zontal emittance of 10.4 nmrad is achieved by allowing a0.1 m dispersion in the straights. The 0.1 m dispersionsetting, while not the minimal horizontal emittance,achieves the minimal horizontal beam size when takinginto account both emittance and dispersion contributions.The storage ring is divided into 14 identical sectors, eachcontaining a 10.9 m arc and 4.5 m straight section. Of the14straights,twoareusedforrfcavities,onefordiagnosticsand onefor beam injection.Eacharc segmentcontains twodipole magnets (with defocusing gradients), six quadru-pole, and seven sextupole magnets, shown in Fig. 1. Orbitand coupling corrections are achieved via additional wind-ings on the sextupole magnets, fed by power suppliesindependent of the main magnet supply. Four sextupolemagnets in each arc have the required windings to act asskewquadrupoles,althoughonlytwoofthesearecurrentlypowered, giving a total of 28 skew quadrupole magnetsaround the storage ring. The power supplies for these skewquadrupoles are bipolar and can supply a current of up to5A,whichdeliversamaximumkstrengthof0.02perskewquadrupole.II. BEAM DIAGNOSTICSThere are two diagnostic beam lines at the AustralianSynchrotron, an x ray and an optical beam line. Details ofthe diagnostics beam lines can be found in Ref. [2].The x-ray diagnostic beam line (XDB) uses the x-raylight from a bending magnet and passes it through apinhole array. The multiple pinhole images formed arethen projected onto a fluorescent screen and imaged bya CCD camera. By measuring the beam size andknowing the beta functions and dispersion at the sourcepoint, it is possible to extract the beam emittance fromthis image. The CCD camera and beam line optics allowfor beam size measurements with 5 m resolution.However, the resolution limit from diffractive effects is60 m [3], which limits the resolution of vertical emit-tance measurements on this beam line to values above10 pm. Additional effects due to fast beam movementduring relatively slow CCD integration and uncertaintiesin the point spread function of the system make the beamline currently unsuitable for precision beam sizemeasurements.

YBa 2 Cu 3 O 7 − δ quasioptical detectors for fast time-domain analysis of terahertz synchrotron radiation

Thin YBa2Cu3O7−δ (YBCO) film detectors embedded into a log-spiral planar antenna were implemented for the detection and analysis of ultrashort terahertz pulses emitted by electron bunches in a synchrotron storage ring. In the direct detection mode terahertz radiation pulses from single electron bunches were resolved. A response time of 45 ps was determined as the full width at half maximum of the voltage transient at the output of the detection system. The sensitivity of the YBCO detector to pulsed terahertz radiation was 70 mV/pJ along with a sensitivity of 30 V/W for continuous radiation at 0.8 THz and a very broad dynamic range of over 30 dB. We found experimental evidences of a nonbolometric nature of the detection mechanism.

Study of electron transport in a compact storage ring after interaction with target materials

A compact electron storage ring has been studied with tools for 3D electromagnetic field simulation. To produce an intense hard X-ray beam, the electrons interact with a target inside the system. If the impact on the electron trajectory after interaction is small, it is possible to reuse the electron several times as in a conventional synchrotron storage ring. We tracked the electrons in the 3D electromagnetic fields of the storage ring. From our numerical experiments we can determine the maximum thickness of the target materials.

Synchrotron infrared spectroscopic ellipsometry for characterization of biofunctional surfaces

AbstractThe structural and thickness homogeneity of different biofunctional surfaces after coating an Au substrate was studied by infrared spectroscopic ellipsometry (IRSE). Monolayer coverage was achieved by washing the samples in aqueous solution. A selected cysteine‐modified CHL peptide and an anti‐glutathione S‐transfer (GST) antibody produced a characteristic change in the IR ellipsometric spectra after peptide and antibody adsorption, confirming the biosensing ability of this technique. IR ellipsometric mapping at the synchrotron storage ring BESSY II in Berlin allowed laterally resolved characterization of the protein films. The IR ellipsometric tanΨ and Δ maps revealed that the protein films are inhomogeneous in structure and thickness after adsorption of the peptide and antibody. The absolute thickness of the protein films varied considerably by up to 3 to 7 nm. We also studied cytosine films with different thicknesses (d = 58 nm and 125 nm) and a guanine film (d = 84 nm). For the two cytosine films the synchrotron spectra revealed that the thicker film in particular was rather homogeneous in thickness but inhomogeneous in structure. For the guanine film the shape of vibrational bands in the ellipsometric spectra correlated with anisotropic molecular orientations.

Diamond X-ray beam-position monitoring using signal readout at the synchrotron radiofrequency

Single-crystal diamond is a material with great potential for the fabrication of X-ray photon beam-position monitors with submicrometre spatial resolution. Low X-ray absorption combined with radiation hardness and excellent thermal-mechanical properties make possible beam-transmissive diamond devices for monitoring synchrotron and free-electron laser X-ray beams. Tests were made using a white bending-magnet synchrotron X-ray beam at DESY to investigate the performance of a position-sensitive diamond device using radiofrequency readout electronics. The device uniformity and position response were measured in a 25 microm collimated X-ray beam with an I-Tech Libera ;Brilliance' system. This readout system was designed for position measurement and feedback control of the electron beam in the synchrotron storage ring, but, as shown here, it can also be used for accurate position readout of a quadrant-electrode single-crystal diamond sensor. The centre-of-gravity position of the F4 X-ray beam at the DORIS III synchrotron was measured with the diamond signal output digitally sampled at a rate of 130 Msample s(-1) by the Brilliance system. Narrow-band filtering and digital averaging of the position signals resulted in a measured position noise below 50 nm (r.m.s.) for a 10 Hz bandwidth.

Coherence properties of hard x-ray synchrotron sources and x-ray free-electron lasers

A general theoretical approach based on the results of statistical optics is used for the analysis of the transverse coherence properties of third generation hard x-ray synchrotron sources and x-ray free-electron lasers (XFEL). Correlation properties of the wavefields are calculated at different distances from an equivalent Gaussian Schell-model source. This model is used to describe coherence properties of the 5 m undulator source at the synchrotron storage ring PETRA III. In the case of XFEL sources the decomposition of the statistical fields into a sum of independently propagating transverse modes is used for the analysis of the coherence properties of these new sources. A detailed calculation is performed for the parameters of the SASE1 undulator at the European XFEL. It is demonstrated that only a few modes contribute significantly to the total radiation field of that source.

Coincidence technique using synchrotron radiation for triple photoionization: Results on rare gas atoms

Final-state trication spectra and electron distributions produced by soft x-ray single-photon triple ionization of rare gas atoms have been obtained by a multiple-coincidence technique using storage-ring synchrotron radiation. The technique uses electron time of flight with ion detection to overcome the problem of high repetition rates in single-bunch operation. A correction needed to the triple-ionization energy of Kr currently listed in standard tables is confirmed, and the method's ability to examine the three-electron distributions, characterizing the ionization mechanisms and post-collision interactions, is illustrated.

Molecular Orientation in Octanedithiol and Hexadecanethiol Monolayers on GaAs and Au Measured by Infrared Spectroscopic Ellipsometry

Infrared spectroscopic ellipsometry was used for determination of molecular orientation and for lateral homogeneity studies of organic monolayers on GaAs and Au, the organic layer being either octanedithiol or hexadecanethiol (HDT). The laterally resolved measurements were performed with the infrared mapping ellipsometer at the synchrotron storage ring BESSY II. The molecular orientation within the monolayers was determined by optical model simulations of the measured ellipsometric spectra. Different tilt angles were obtained for the monolayers of HDT and octanedithiol on GaAs: 19 degrees and >30 degrees , respectively. The tilt angle of the methylene chains for HDT on Au substrate (22 degrees ) is similar to the 19 degrees tilt which was obtained for the HDT monolayers on GaAs, thus suggesting similar molecular ordering of the thiolates on both substrates.

Ultrathin responsive polyelectrolyte brushes studied by infrared synchrotron mapping ellipsometry

An infrared microfocus spectroscopic mapping ellipsometer was set up at the Berlin electron synchrotron storage ring and used to study ultrathin polyacrylic acid brush films with 3nm thickness. The pH-responsive properties of the brush on a gold-coated glass substrate were investigated. The chemical structure of the brush was resolved with a spatial resolution of 300μm using the synchrotron mapping ellipsometer.

Targets emitting transition radiation for performing X-ray lithography by the tabletop synchrotron MIRRORCLE-20SX

The tabletop storage ring synchrotron (SRS) MIRRORCLE-20SX is a powerful source of soft X-rays emitted from transition radiation (TR) targets. SRS can be used as a source for performing X-ray lithography (XRL) when it emits TR power P XRL⩾50–100 mW of photons having energy in the range 490–1860 eV. One-foil targets in SRS can emit a high TR power, and the electron beam geometry of MIRRORCLE-20SX requires using TR strip targets with a width ≅3 mm. P XRL emitted by one-foil strip TR targets is estimated for several foil materials, and varying foil thickness d. These results show that a target containing one C foil with d≅260 nm can be used for performing XRL. Target made of one collodion foil with d≅290 nm, and target of one Al foil with d≅200 nm emit less, but could also be used for XRL. We manufactured such targets by depositing layers of these materials on slide glass, using Teepol as a releasing agent, and subsequently floating them on a water surface. The C layer is prepared by a horizontal resistance thermal evaporation, and supported by a 270–300 nm thick collodion layer, formed onto the Teepol film. The Al layer is thermally evaporated.

Strange particle production inp+pcollisions ats=200GeV

We present strange particle spectra and yields measured at midrapidity in √s=200 GeV proton-proton (p+p) collisions at the BNL Relativistic Heavy Ion Collider (RHIC). We find that the previously observed universal transverse mass (m_T≡√pT2+m2) scaling of hadron production in p+p collisions seems to break down at higher mT and that there is a difference in the shape of the mT spectrum between baryons and mesons. We observe midrapidity antibaryon to baryon ratios near unity for Λ and Ξ baryons and no dependence of the ratio on transverse momentum, indicating that our data do not yet reach the quark-jet dominated region. We show the dependence of the mean transverse momentum ⟨pT⟩ on measured charged particle multiplicity and on particle mass and infer that these trends are consistent with gluon-jet dominated particle production. The data are compared with previous measurements made at the CERN Super Proton Synchrotron and Intersecting Storage Rings and in Fermilab experiments and with leading-order and next-to-leading-order string fragmentation model predictions. We infer from these comparisons that the spectral shapes and particle yields from p+p collisions at RHIC energies have large contributions from gluon jets rather than from quark jets.