-
Pty-Chi: A PyTorch-based modern ptychographic data analysis package
Authors:
Ming Du,
Hanna Ruth,
Steven Henke,
Yi Jiang,
Viktor Nikitin,
Ashish Tripathi,
Junjing Deng,
Jeffrey Klug,
Peco Myint,
Tao Zhou,
Nicholas Schwarz,
Mathew Cherukara,
Alec Sandy,
Stefan Vogt
Abstract:
Ptychography has become an indispensable tool for high-resolution, non-destructive imaging using coherent light sources. The processing of ptychographic data critically depends on robust, efficient, and flexible computational reconstruction software. We introduce Pty-Chi, an open-source ptychographic reconstruction package built on PyTorch that unifies state-of-the-art analytical algorithms with a…
▽ More
Ptychography has become an indispensable tool for high-resolution, non-destructive imaging using coherent light sources. The processing of ptychographic data critically depends on robust, efficient, and flexible computational reconstruction software. We introduce Pty-Chi, an open-source ptychographic reconstruction package built on PyTorch that unifies state-of-the-art analytical algorithms with automatic differentiation methods. Pty-Chi provides a comprehensive suite of reconstruction algorithms while supporting advanced experimental parameter corrections such as orthogonal probe relaxation and multislice modeling. Leveraging PyTorch as the computational backend ensures vendor-agnostic GPU acceleration, multi-device parallelization, and seamless access to modern optimizers. An object-oriented, modular design makes Pty-Chi highly extendable, enabling researchers to prototype new imaging models, integrate machine learning approaches, or build entirely new workflows on top of its core components. We demonstrate Pty-Chi's capabilities through challenging case studies that involve limited coherence, low overlap, and unstable illumination during scanning, which highlight its accuracy, versatility, and extensibility. With community-driven development and open contribution, Pty-Chi offers a modern, maintainable platform for advancing computational ptychography and for enabling innovative imaging algorithms at synchrotron facilities and beyond.
△ Less
Submitted 23 October, 2025;
originally announced October 2025.
-
Accelerated deep self-supervised ptycho-laminography for three-dimensional nanoscale imaging of integrated circuits
Authors:
Iksung Kang,
Yi Jiang,
Mirko Holler,
Manuel Guizar-Sicairos,
A. F. J. Levi,
Jeffrey Klug,
Stefan Vogt,
George Barbastathis
Abstract:
Three-dimensional inspection of nanostructures such as integrated circuits is important for security and reliability assurance. Two scanning operations are required: ptychographic to recover the complex transmissivity of the specimen; and rotation of the specimen to acquire multiple projections covering the 3D spatial frequency domain. Two types of rotational scanning are possible: tomographic and…
▽ More
Three-dimensional inspection of nanostructures such as integrated circuits is important for security and reliability assurance. Two scanning operations are required: ptychographic to recover the complex transmissivity of the specimen; and rotation of the specimen to acquire multiple projections covering the 3D spatial frequency domain. Two types of rotational scanning are possible: tomographic and laminographic. For flat, extended samples, for which the full 180 degree coverage is not possible, the latter is preferable because it provides better coverage of the 3D spatial frequency domain compared to limited-angle tomography. It is also because the amount of attenuation through the sample is approximately the same for all projections. However, both techniques are time consuming because of extensive acquisition and computation time. Here, we demonstrate the acceleration of ptycho-laminographic reconstruction of integrated circuits with 16-times fewer angular samples and 4.67-times faster computation by using a physics-regularized deep self-supervised learning architecture. We check the fidelity of our reconstruction against a densely sampled reconstruction that uses full scanning and no learning. As already reported elsewhere [Zhou and Horstmeyer, Opt. Express, 28(9), pp. 12872-12896], we observe improvement of reconstruction quality even over the densely sampled reconstruction, due to the ability of the self-supervised learning kernel to fill the missing cone.
△ Less
Submitted 10 April, 2023;
originally announced April 2023.
-
Attentional Ptycho-Tomography (APT) for three-dimensional nanoscale X-ray imaging with minimal data acquisition and computation time
Authors:
Iksung Kang,
Ziling Wu,
Yi Jiang,
Yudong Yao,
Junjing Deng,
Jeffrey Klug,
Stefan Vogt,
George Barbastathis
Abstract:
Noninvasive X-ray imaging of nanoscale three-dimensional objects, e.g. integrated circuits (ICs), generally requires two types of scanning: ptychographic, which is translational and returns estimates of complex electromagnetic field through ICs; and tomographic scanning, which collects complex field projections from multiple angles. Here, we present Attentional Ptycho-Tomography (APT), an approach…
▽ More
Noninvasive X-ray imaging of nanoscale three-dimensional objects, e.g. integrated circuits (ICs), generally requires two types of scanning: ptychographic, which is translational and returns estimates of complex electromagnetic field through ICs; and tomographic scanning, which collects complex field projections from multiple angles. Here, we present Attentional Ptycho-Tomography (APT), an approach trained to provide accurate reconstructions of ICs despite incomplete measurements, using a dramatically reduced amount of angular scanning. Training process includes regularizing priors based on typical IC patterns and the physics of X-ray propagation. We demonstrate that APT with 12-time reduced angles achieves fidelity comparable to the gold standard with the original set of angles. With the same set of reduced angles, APT also outperforms baseline reconstruction methods. In our experiments, APT achieves 108-time aggregate reduction in data acquisition and computation without compromising quality. We expect our physics-assisted machine learning framework could also be applied to other branches of nanoscale imaging.
△ Less
Submitted 29 November, 2022;
originally announced December 2022.
-
Ptychopy: GPU framework for ptychographic data analysis
Authors:
Ke Yue,
Junjing Deng,
Yi Jiang,
Youssef Nashed,
David Vine,
Stefan Vogt
Abstract:
X-ray ptychography imaging at synchrotron facilities like the Advanced Photon Source (APS) involves controlling instrument hardwares to collect a set of diffraction patterns from overlapping coherent illumination spots on extended samples, managing data storage, reconstructing ptychographic images from acquired diffraction patterns, and providing the visualization of results and feedback. In addit…
▽ More
X-ray ptychography imaging at synchrotron facilities like the Advanced Photon Source (APS) involves controlling instrument hardwares to collect a set of diffraction patterns from overlapping coherent illumination spots on extended samples, managing data storage, reconstructing ptychographic images from acquired diffraction patterns, and providing the visualization of results and feedback. In addition to the complicated workflow, ptychography instrument could produce up to several TB's of data per second that is needed to be processed in real time. This brings up the need to develop a high performance, robust and user friendly processing software package for ptychographic data analysis. In this paper we present a software framework which provides functionality of visualization, work flow control, and data reconstruction. To accelerate the computation and large datasets process, the data reconstruction part is implemented with three algorithms, ePIE, DM and LSQML using CUDA-C on GPU.
△ Less
Submitted 24 January, 2022;
originally announced February 2022.
-
C-Arm Non-Circular Orbits: Geometric Calibration, Image Quality, and Avoidance of Metal Artifacts
Authors:
Pengwei Wu,
Niral Sheth,
Alejandro Sisniega,
Tongyu Wang,
Ali Uneri,
Runze Han,
Rohan Vijayan,
Prasad Vagdargi,
Bjoern Kreher,
Holger Kunze,
Gerhard Kleinszig,
Sebastian Vogt,
Sheng-Fu Larry Lo,
Nicholas Theodore,
Jeffrey Siewerdsen
Abstract:
Metal artifacts present a frequent challenge to cone-beam CT (CBCT) in image-guided surgery, obscuring visualization of metal instruments and adjacent anatomy. Recent advances in mobile C-arm systems have enabled 3D imaging capacity with non-circular orbits. We extend a previously proposed metal artifacts avoidance (MAA) method to reduce the influence of metal artifacts by prospectively defining a…
▽ More
Metal artifacts present a frequent challenge to cone-beam CT (CBCT) in image-guided surgery, obscuring visualization of metal instruments and adjacent anatomy. Recent advances in mobile C-arm systems have enabled 3D imaging capacity with non-circular orbits. We extend a previously proposed metal artifacts avoidance (MAA) method to reduce the influence of metal artifacts by prospectively defining a non-circular orbit that avoids metal-induced biases in projection domain. Accurate geometric calibration is an important challenge to accurate 3D image reconstruction for such orbits. We investigate the performance of interpolation-based calibration from a library of circular orbits for any non-circular orbit. We apply the method to non-circular scans acquired for MAA, which involves: (i) coarse 3D localization of metal objects via only two scout views using an end-to-end trained neural network; (ii) calculation of the metal-induced x-ray spectral shift for all possible views; and (iii) identification of the non-circular orbit that minimizes the variations in spectral shift. Non-circular orbits with interpolation-based geometric calibration yielded reasonably accurate 3D image reconstruction. The end-to-end neural network accurately localized metal implants with just two scout views even in complex anatomical scenes, improving Dice coefficient by ~42% compared to a more conventional cascade of separately trained U-nets. In a spine phantom with pedicle screw instrumentation, non-circular orbits identified by the MAA method reduced the magnitude of metal "blomming" artifacts (apparent width of the screw shaft) in CBCT reconstructions by ~70%. The proposed imaging and calibration methods present a practical means to improve image quality in mobile C-arm CBCT by identifying non-circular scan protocols that improve sampling and reduce metal-induced biases in the projection data.
△ Less
Submitted 30 September, 2020;
originally announced October 2020.
-
A transportable interrogation laser system with an instability of $\mathrm{mod}\,σ_{\rm y} = 3\times10^{-16}$
Authors:
Sebastian Häfner,
Sofia Herbers,
Stefan Vogt,
Christian Lisdat,
Uwe Sterr
Abstract:
We present an interrogation laser system for a transportable strontium lattice clock operating at 698 nm, which is based on an ultra-low-expansion glass reference cavity. Transportability is achieved by implementing a rigid, compact, and vibration insensitive mounting of the 12 cm-long reference cavity, sustaining shocks of up to 50 g. The cavity is mounted at optimized support points that indepen…
▽ More
We present an interrogation laser system for a transportable strontium lattice clock operating at 698 nm, which is based on an ultra-low-expansion glass reference cavity. Transportability is achieved by implementing a rigid, compact, and vibration insensitive mounting of the 12 cm-long reference cavity, sustaining shocks of up to 50 g. The cavity is mounted at optimized support points that independently constrain all degrees of freedom. This mounting concept is especially beneficial for cavities with a ratio of length $L$ over diameter $D$ $L/D>1$. Generally large $L$ helps to reduce thermal noise-induced laser frequency instability while small $D$ leads to small cavity volume. The frequency instability was evaluated, reaching its thermal noise floor of $\mathrm{mod}\,σ_{\rm y} \approx 3 \times 10^{-16}$ for averaging times between 0.5 s and 10 s. The laser system was successfully operated during several field studies.
△ Less
Submitted 19 May, 2020; v1 submitted 3 March, 2020;
originally announced March 2020.
-
Geodesy and metrology with a transportable optical clock
Authors:
Jacopo Grotti,
Silvio Koller,
Stefan Vogt,
Sebastian Häfner,
Uwe Sterr,
Christian Lisdat,
Heiner Denker,
Christian Voigt,
Ludger Timmen,
Antoine Rolland,
Fred N. Baynes,
Helen S. Margolis,
Michel Zampaolo,
Pierre Thoumany,
Marco Pizzocaro,
Benjamin Rauf,
Filippo Bregolin,
Anna Tampellini,
Piero Barbieri,
Massimo Zucco,
Giovanni A. Costanzo,
Cecilia Clivati,
Filippo Levi,
Davide Calonico
Abstract:
The advent of novel measurement instrumentation can lead to paradigm shifts in scientific research. Optical atomic clocks, due to their unprecedented stability and uncertainty, are already being used to test physical theories and herald a revision of the International System of units (SI). However, to unlock their potential for cross-disciplinary applications such as relativistic geodesy, a major…
▽ More
The advent of novel measurement instrumentation can lead to paradigm shifts in scientific research. Optical atomic clocks, due to their unprecedented stability and uncertainty, are already being used to test physical theories and herald a revision of the International System of units (SI). However, to unlock their potential for cross-disciplinary applications such as relativistic geodesy, a major challenge remains. This is their transformation from highly specialized instruments restricted to national metrology laboratories into flexible devices deployable in different locations. Here we report the first field measurement campaign performed with a ubiquitously applicable $^{87}$Sr optical lattice clock. We use it to determine the gravity potential difference between the middle of a mountain and a location 90 km apart, exploiting both local and remote clock comparisons to eliminate potential clock errors. A local comparison with a $^{171}$Yb lattice clock also serves as an important check on the international consistency of independently developed optical clocks. This campaign demonstrates the exciting prospects for transportable optical clocks.
△ Less
Submitted 11 May, 2017;
originally announced May 2017.
-
A transportable optical lattice clock with $7\times10^{-17}$ uncertainty
Authors:
S. B. Koller,
J. Grotti,
St. Vogt,
A. Al-Masoudi,
S. Dörscher,
S. Häfner,
U. Sterr,
Ch. Lisdat
Abstract:
We present a transportable optical clock (TOC) with $^{87}$Sr. Its complete characterization against a stationary lattice clock resulted in a systematic uncertainty of ${7.4 \times 10^{-17}}$ which is currently limited by the statistics of the determination of the residual lattice light shift. The measurements confirm that the systematic uncertainty is reduceable to below the design goal of…
▽ More
We present a transportable optical clock (TOC) with $^{87}$Sr. Its complete characterization against a stationary lattice clock resulted in a systematic uncertainty of ${7.4 \times 10^{-17}}$ which is currently limited by the statistics of the determination of the residual lattice light shift. The measurements confirm that the systematic uncertainty is reduceable to below the design goal of $1 \times 10^{-17}$. The instability of our TOC is $1.3 \times 10^{-15}/\sqrt{(τ/s)}$. Both, the systematic uncertainty and the instability are to our best knowledge currently the best achieved with any type of transportable clock. For autonomous operation the TOC is installed in an air-conditioned car-trailer. It is suitable for chronometric leveling with sub-meter resolution as well as intercontinental cross-linking of optical clocks, which is essential for a redefiniton of the SI second. In addition, the TOC will be used for high precision experiments for fundamental science that are commonly tied to precise frequency measurements and it is a first step to space borne optical clocks
△ Less
Submitted 20 September, 2016;
originally announced September 2016.
-
Development of a strontium optical lattice clock for the SOC mission on the ISS
Authors:
S. Origlia,
S. Schiller,
M. S. Pramod,
L. Smith,
Y. Singh,
W. He,
S. Viswam,
D. Świerad,
J. Hughes,
K. Bongs,
U. Sterr,
Ch. Lisdat,
S. Vogt,
S. Bize,
J. Lodewyck,
R. Le Targat,
D. Holleville,
B. Venon,
P. Gill,
G. Barwood,
I. R. Hill,
Y. Ovchinnikov,
A. Kulosa,
W. Ertmer,
E. -M. Rasel
, et al. (3 additional authors not shown)
Abstract:
The ESA mission "Space Optical Clock" project aims at operating an optical lattice clock on the ISS in approximately 2023. The scientific goals of the mission are to perform tests of fundamental physics, to enable space-assisted relativistic geodesy and to intercompare optical clocks on the ground using microwave and optical links. The performance goal of the space clock is less than…
▽ More
The ESA mission "Space Optical Clock" project aims at operating an optical lattice clock on the ISS in approximately 2023. The scientific goals of the mission are to perform tests of fundamental physics, to enable space-assisted relativistic geodesy and to intercompare optical clocks on the ground using microwave and optical links. The performance goal of the space clock is less than $1 \times 10^{-17}$ uncertainty and $1 \times 10^{-15} τ^{-1/2}$ instability. Within an EU-FP7-funded project, a strontium optical lattice clock demonstrator has been developed. Goal performances are instability below $1 \times 10^{-15} τ^{-1/2}$ and fractional inaccuracy $5 \times 10^{-17}$. For the design of the clock, techniques and approaches suitable for later space application are used, such as modular design, diode lasers, low power consumption subunits, and compact dimensions. The Sr clock apparatus is fully operational, and the clock transition in $^{88}$Sr was observed with linewidth as small as 9 Hz.
△ Less
Submitted 19 March, 2016;
originally announced March 2016.
-
Development of a strontium optical lattice clock for the SOC mission on the ISS
Authors:
K. Bongs,
Y. Singh,
L. Smith,
W. He,
O. Kock,
D. Swierad,
J. Hughes,
S. Schiller,
S. Alighanbari,
S. Origlia,
S. Vogt,
U. Sterr,
Ch. Lisdat,
R. Le Targat,
J. Lodewyck,
D. Holleville,
B. Venon,
S. Bize,
G. P. Barwood,
P. Gill,
I. R. Hill,
Y. B. Ovchinnikov,
N. Poli,
G. M. Tino,
J. Stuhler
, et al. (2 additional authors not shown)
Abstract:
Ultra-precise optical clocks in space will allow new studies in fundamental physics and astronomy. Within an European Space Agency (ESA) program, the Space Optical Clocks (SOC) project aims to install and to operate an optical lattice clock on the International Space Station (ISS) towards the end of this decade. It would be a natural follow-on to the ACES mission, improving its performance by at l…
▽ More
Ultra-precise optical clocks in space will allow new studies in fundamental physics and astronomy. Within an European Space Agency (ESA) program, the Space Optical Clocks (SOC) project aims to install and to operate an optical lattice clock on the International Space Station (ISS) towards the end of this decade. It would be a natural follow-on to the ACES mission, improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Within the EU-FP7-SPACE-2010-1 project no. 263500, during the years 2011-2015 a compact, modular and robust strontium lattice optical clock demonstrator has been developed. Goal performance is a fractional frequency instability below 1x10^{-15}, tau^{-1/2} and a fractional inaccuracy below 5x10^{-17}. Here we describe the current status of the apparatus' development, including the laser subsystems. Robust preparation of cold {88}^Sr atoms in a second stage magneto-optical trap (MOT) is achieved.
△ Less
Submitted 29 March, 2015;
originally announced March 2015.
-
8E-17 fractional laser frequency instability with a long room-temperature cavity
Authors:
Sebastian Häfner,
Stephan Falke,
Christian Grebing,
Stefan Vogt,
Thomas Legero,
Mikko Merimaa,
Christian Lisdat,
Uwe Sterr
Abstract:
We present a laser system based on a 48 cm long optical glass resonator. The large size requires a sophisticated thermal control and optimized mounting design. A self balancing mounting was essential to reliably reach sensitivities to acceleration of below $Δν/ ν$ < 2E-10 /g in all directions. Furthermore, fiber noise cancellations from a common reference point near the laser diode to the cavity m…
▽ More
We present a laser system based on a 48 cm long optical glass resonator. The large size requires a sophisticated thermal control and optimized mounting design. A self balancing mounting was essential to reliably reach sensitivities to acceleration of below $Δν/ ν$ < 2E-10 /g in all directions. Furthermore, fiber noise cancellations from a common reference point near the laser diode to the cavity mirror and to additional user points (Sr clock and frequency comb) are implemented. Through comparison to other cavity-stabilized lasers and to a strontium lattice clock an instability of below 1E-16 at averaging times from 1 s to 1000 s is revealed.
△ Less
Submitted 31 March, 2015; v1 submitted 9 February, 2015;
originally announced February 2015.
-
A transportable strontium optical lattice clock
Authors:
N. Poli,
M. Schioppo,
S. Vogt,
St. Falke,
U. Sterr,
Ch. Lisdat,
G. M. Tino
Abstract:
We report on a transportable optical clock, based on laser-cooled strontium atoms trapped in an optical lattice. The experimental apparatus is composed of a compact source of ultra-cold strontium atoms including a compact cooling laser set-up and a transportable ultra-stable laser for interrogating the optical clock transition. The whole setup (excluding electronics) fits within a volume of less t…
▽ More
We report on a transportable optical clock, based on laser-cooled strontium atoms trapped in an optical lattice. The experimental apparatus is composed of a compact source of ultra-cold strontium atoms including a compact cooling laser set-up and a transportable ultra-stable laser for interrogating the optical clock transition. The whole setup (excluding electronics) fits within a volume of less than 2 m$^3$. The high degree of operation reliability of both systems allowed the spectroscopy of the clock transition to be performed with 10 Hz resolution. We estimate an uncertainty of the clock of $7\times10^{-15}$.
△ Less
Submitted 17 September, 2014; v1 submitted 16 September, 2014;
originally announced September 2014.
-
A strontium lattice clock with $3 \times 10^{-17}$ inaccuracy and its frequency
Authors:
Stephan Falke,
Nathan Lemke,
Christian Grebing,
Burghard Lipphardt,
Stefan Weyers,
Vladislav Gerginov,
Nils Huntemann,
Christian Hagemann,
Ali Al-Masoudi,
Sebastian Häfner,
Stefan Vogt,
Uwe Sterr,
Christian Lisdat
Abstract:
We have measured the absolute frequency of the optical lattice clock based on $^{87}$Sr at PTB with an uncertainty of $3.9\times 10^{-16}$ using two caesium fountain clocks. This is close to the accuracy of today's best realizations of the SI second. The absolute frequency of the 5s$^2$ $^1$S$_0$-5s5p $^3$P$_0$ transition in $^{87}$Sr is 429,228,004,229,873.13(17) Hz. Our result is in excellent ag…
▽ More
We have measured the absolute frequency of the optical lattice clock based on $^{87}$Sr at PTB with an uncertainty of $3.9\times 10^{-16}$ using two caesium fountain clocks. This is close to the accuracy of today's best realizations of the SI second. The absolute frequency of the 5s$^2$ $^1$S$_0$-5s5p $^3$P$_0$ transition in $^{87}$Sr is 429,228,004,229,873.13(17) Hz. Our result is in excellent agreement with recent measurements performed in different laboratories worldwide. We improved the total systematic uncertainty of our Sr frequency standard by a factor of five and reach $3\times 10^{-17}$, opening new prospects for frequency ratio measurements between optical clocks for fundamental research, geodesy, or optical clock evaluation.
△ Less
Submitted 15 August, 2014; v1 submitted 12 December, 2013;
originally announced December 2013.
-
The GERDA experiment for the search of 0νββ decay in ^{76}Ge
Authors:
GERDA Collaboration,
K. -H. Ackermann,
M. Agostini,
M. Allardt,
M. Altmann,
E. Andreotti,
A. M. Bakalyarov,
M. Balata,
I. Barabanov,
M. Barnabe Heider,
N. Barros,
L. Baudis,
C. Bauer,
N. Becerici-Schmidt,
E. Bellotti,
S. Belogurov,
S. T. Belyaev,
G. Benato,
A. Bettini,
L. Bezrukov,
T. Bode,
V. Brudanin,
R. Brugnera,
D. Budjas,
A. Caldwell
, et al. (114 additional authors not shown)
Abstract:
The GERDA collaboration is performing a search for neutrinoless double beta decay of ^{76}Ge with the eponymous detector. The experiment has been installed and commissioned at the Laboratori Nazionali del Gran Sasso and has started operation in November 2011. The design, construction and first operational results are described, along with detailed information from the R&D phase.
The GERDA collaboration is performing a search for neutrinoless double beta decay of ^{76}Ge with the eponymous detector. The experiment has been installed and commissioned at the Laboratori Nazionali del Gran Sasso and has started operation in November 2011. The design, construction and first operational results are described, along with detailed information from the R&D phase.
△ Less
Submitted 17 December, 2012;
originally announced December 2012.
-
The 87-Sr optical frequency standard at PTB
Authors:
St. Falke,
H. Schnatz,
J. S. R. Vellore Winfred,
Th. Middelmann,
St. Vogt,
S. Weyers,
B. Lipphardt,
G. Grosche,
F. Riehle,
U. Sterr,
Ch. Lisdat
Abstract:
With 87-Sr atoms confined in a one dimensional optical lattice, the frequency of the optical clock transition 5s^2 ^1S_0 - 5s5p ^3P_0 has been determined to be 429 228 004 229 872.9(5) Hz. The transition frequency was measured with the help of a fs-frequency comb against one of PTB's H-masers whose frequency was measured simultaneously by the PTB Cs fountain clock CSF1. The Sr optical frequency st…
▽ More
With 87-Sr atoms confined in a one dimensional optical lattice, the frequency of the optical clock transition 5s^2 ^1S_0 - 5s5p ^3P_0 has been determined to be 429 228 004 229 872.9(5) Hz. The transition frequency was measured with the help of a fs-frequency comb against one of PTB's H-masers whose frequency was measured simultaneously by the PTB Cs fountain clock CSF1. The Sr optical frequency standard contributes with a fractional uncertainty of 1.5 10^-16 to the total uncertainty. The agreement of the measured transition frequency with previous measurements at other institutes supports the status of this transition as secondary representation of the second with the currently smallest uncertainty.
△ Less
Submitted 26 August, 2011; v1 submitted 26 April, 2011;
originally announced April 2011.
-
Demonstration of a Transportable 1 Hz-Linewidth Laser
Authors:
Stefan Vogt,
Christian Lisdat,
Thomas Legero,
Uwe Sterr,
Ingo Ernsting,
Alexander Nevsky,
Stephan Schiller
Abstract:
We present the setup and test of a transportable clock laser at 698 nm for a strontium lattice clock. A master-slave diode laser system is stabilized to a rigidly mounted optical reference cavity. The setup was transported by truck over 400 km from Braunschweig to Düsseldorf, where the cavity-stabilized laser was compared to a stationary clock laser for the interrogation of ytterbium (578 nm). Onl…
▽ More
We present the setup and test of a transportable clock laser at 698 nm for a strontium lattice clock. A master-slave diode laser system is stabilized to a rigidly mounted optical reference cavity. The setup was transported by truck over 400 km from Braunschweig to Düsseldorf, where the cavity-stabilized laser was compared to a stationary clock laser for the interrogation of ytterbium (578 nm). Only minor realignments were necessary after the transport. The lasers were compared by a Ti:Sapphire frequency comb used as a transfer oscillator. The thus generated virtual beat showed a combined linewidth below 1 Hz (at 1156 nm). The transport back to Braunschweig did not degrade the laser performance, as was shown by interrogating the strontium clock transition.
△ Less
Submitted 18 May, 2011; v1 submitted 13 October, 2010;
originally announced October 2010.
-
Mapping cellular magnesium using X-ray microfluorescence and atomic force microscopy
Authors:
Stefano Lagomarsino,
Stefano Iotti,
Giovanna Farruggia,
Alessia Cedola,
Valentina Trapani,
Michela Fratini,
Inna Bukreeva,
Andrea Notargiacomo,
Lucia Mastrototaro,
Ian McNulty,
Stefan Vogt,
Daniel Legnini,
Sangsoo Kim,
Jeanette A M Maier,
Federica I Wolf
Abstract:
Magnesium is the most abundant intracellular divalent cation. We present an innovative experimental approach to localizing intracellular magnesium that combines elemental and morphological information from individual cells with high-resolution spatial information. Integration of information from scanning fluorescence X-ray microscopy with information from atomic force microscopy was used to genera…
▽ More
Magnesium is the most abundant intracellular divalent cation. We present an innovative experimental approach to localizing intracellular magnesium that combines elemental and morphological information from individual cells with high-resolution spatial information. Integration of information from scanning fluorescence X-ray microscopy with information from atomic force microscopy was used to generate a magnesium concentration map and to determine the X-ray linear absorption coefficient map within a whole dehydrated mammary epithelial cell.
△ Less
Submitted 10 July, 2010;
originally announced July 2010.
-
Takagi-Taupin Description of X-ray Dynamical Diffraction from Diffractive Optics with Large Numerical Aperture
Authors:
Hanfei Yan,
Jorg Maser,
Albert Macrander,
Qun Shen,
Stefan Vogt,
Brian Stephenson,
Hyon Chol Kang
Abstract:
We present a formalism of x-ray dynamical diffraction from volume diffractive optics with large numerical aperture and high aspect ratio, in an analogy to the Takagi-Taupin equations for strained single crystals. We derive a set of basic equations for dynamical diffraction from volume diffractive optics, which enable us to study the focusing property of these optics with various grating profiles…
▽ More
We present a formalism of x-ray dynamical diffraction from volume diffractive optics with large numerical aperture and high aspect ratio, in an analogy to the Takagi-Taupin equations for strained single crystals. We derive a set of basic equations for dynamical diffraction from volume diffractive optics, which enable us to study the focusing property of these optics with various grating profiles. We study volume diffractive optics that satisfy the Bragg condition to various degrees, namely flat, tilted and wedged geometries, and derive the curved geometries required for ultimate focusing. We show that the curved geometries satisfy the Bragg condition everywhere and phase requirement for point focusing, and effectively focus hard x-rays to a scale close to the wavelength.
△ Less
Submitted 30 April, 2007;
originally announced April 2007.