Photon Source Research Articles

Beam coupling impedance measurement based on Goubau line method

The Goubau line method has been recently proposed and used for the longitudinal beam coupling impedance measurement of vacuum components. To extend the application of this method, the measurement of transverse impedance using the Goubau line method is proposed in this work. The feasibility of measuring the transverse impedance using the Goubau line method has been tested using a pillbox cavity. Additionally, the frequency shift induced by the dielectric-coated wire in the Goubau line measurements has been investigated analytically. The contribution of the dielectric coating to the frequency shift has been studied. Finally, the Goubau line setup has been optimized and used to evaluate the longitudinal and transverse beam coupling impedance of key vacuum components in the High Energy Photon Source.

The magnetic moment for pedestrians

The causal arrangement of the two extended emission and detection sources and the photon source is considered. The emission source emits the charged particle and photon. The photon source which is located between emission and detection sources is capable of the transmitting of space-like momenta. The photon propagates undisturbed between emission and detection sources, while the charged particle is rejected by the extended photon source. The result of such process is the modification of the vacuum-to-vacuum amplitude in form of the additional term which can be interpreted as the additional magnetic moment of electron. The derivation is realized with the mathematical simplicity and the Schwinger pedagogical clarity.

BEATS: BEAmline for synchrotron X-ray microTomography at SESAME.

The ID10 beamline of the SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East) synchrotron light source in Jordan was inaugurated in June 2023 and is now open to scientific users. The beamline, which was designed and installed within the European Horizon 2020 project BEAmline for Tomography at SESAME (BEATS), provides full-field X-ray radiography and microtomography imaging with monochromatic or polychromatic X-rays up to photon energies of 100 keV. The photon source generated by a 2.9 T wavelength shifter with variable gap, and a double-multilayer monochromator system allow versatile application for experiments requiring either an X-ray beam with high intensity and flux, and/or a partially spatial coherent beam for phase-contrast applications. Sample manipulation and X-ray detection systems are designed to allow scanning samples with different size, weight and material, providing image voxel sizes from 13 µm down to 0.33 µm. A state-of-the-art computing infrastructure for data collection, three-dimensional (3D) image reconstruction and data analysis allows the visualization and exploration of results online within a few seconds from the completion of a scan. Insights from 3D X-ray imaging are key to the investigation of specimens from archaeology and cultural heritage, biology and health sciences, materials science and engineering, earth, environmental sciences and more. Microtomography scans and preliminary results obtained at the beamline demonstrate that the new beamline ID10-BEATS expands significantly the range of scientific applications that can be targeted at SESAME.

Room Temperature Emission Line Narrowing and Long‐Range Photon Transport in Colloidal Quantum Wells Coupled to Metasurface Resonance

AbstractHighly efficient and spectrally pure single photon sources are desirable in fundamental studies of quantum physics and in many varied applications like in quantum metrology and quantum cryptography. 2D semiconductor colloidal quantum wells (CQWs) are quite appropriate as nanoscale photon sources because of their giant oscillator strengths and large absorption cross sections. The integration of such sources with dielectric metasurfaces exhibiting narrow resonances provides an excellent platform for highly efficient light‐matter interactions and the development of on‐chip light sources with high spectral purity. Here details on the use of capillary filling method are reported to achieve photonic coupling of CQWs to a metasurface resonator (MSR) featuring a square‐lattice geometry of holes on a slab‐waveguide to achieve strongly enhanced and almost spectrally pure emission of ≈3% of the original out‐of‐plane emission line‐width of the quantum emitters at room temperature. Long‐range exciton‐mediated photon transport facilitated by in‐plane slab waveguide modes is demonstrated and a theoretical basis to explain all the experimental data including that in terms of the MSR‐modified Lamb shifts and Purcell decays is provided. The results demonstrate a new platform with emergent photonic properties and suggest possibility of their use in on‐chip photonic quantum information processing.

Wavelength-tunable high-fidelity entangled photon sources enabled by dual Stark effects

The construction of a large-scale quantum internet requires quantum repeaters containing multiple entangled photon sources with identical wavelengths. Semiconductor quantum dots can generate entangled photon pairs deterministically with high fidelity. However, realizing wavelength-matched quantum-dot entangled photon sources faces two difficulties: the non-uniformity of emission wavelength and exciton fine-structure splitting induced fidelity reduction. Typically, these two factors are not independently tunable, making it challenging to achieve simultaneous improvement. In this work, we demonstrate wavelength-tunable entangled photon sources based on droplet-etched GaAs quantum dots through the combined use of AC and quantum-confined Stark effects. The emission wavelength can be tuned by ~1 meV while preserving an entanglement fidelity f exceeding 0.955(1) in the entire tuning range. Based on this hybrid tuning scheme, we finally demonstrate multiple wavelength-matched entangled photon sources with f > 0.919(3), paving the way towards robust and scalable on-demand entangled photon sources for quantum internet and integrated quantum optical circuits.

Visible-band polarization-entangled photon source by quantum frequency transduction

Visible-band polarization-entangled photon source by quantum frequency transduction

Research and development of the neutron-photon coupled transport method in the fast reactor code system MOSASAUR

In the high-fidelity reactor physics design of fast reactors, the influence of photon effect needs to be explicitly simulated with the neutron-photon coupled transport method. The neutron-photon coupled transport-burnup method was researched based on the fast reactor physics design software package MOSASAUR. Photon library, photon cross-section production, photon source and photon power calculation methods were researched and the related calculation modules were developed and verified with the RBEC-M benchmark and the MET-1000 benchmark. Numerical results showed the good accuracy of the newly-developed neutron-photon coupled transport ability with MOSASAUR. The photon effect introduced the 80% difference for the assembly power in the RBEC-M benchmark, which showed the importance of the neutron-photon coupled transport in the fast reactor design.

Vacuum‐ultraviolet‐photoionization chamber for the investigation of ion‐based surface treatment and thin film deposition at atmospheric pressure

AbstractThe vacuum‐ultraviolet‐photoionization chamber was constructed to allow controlled ion generation and well‐defined surface treatment with these ions at atmospheric pressure. It utilizes atmospheric helium plasma as a photon source and separates the ion generation from the plasma by an aerodynamic window. The ions are guided to the grounded substrate by a weak electric field, while the diffusive transport of neutrals is reduced by a helium gas flow along the substrate. Ionic species and the absolute ion flux were determined in the substrate region. Ion‐based thin film deposition using a precursor was investigated as a model process. The proposed system enables future investigation of e.g. the isolated interaction of ions with biological substrates.

The design and application of magnetic landmark used for magnetic fiducialization of HEPS insertion devices*

Abstract Achieving high performance in synchrotron radiation light sources demands increased precision in fiducialization and alignment of insertion devices (IDs). Conventional sensor systems utilizing Hall probes for high-precision magnetic field measurements face limitations in determining the absolute position of the magnetic center of IDs. In this paper, the Magnetic Landmark (MLK), a novel solution based on a magnetized block structure, is designed to address this challenge. The MLK serves as an intermediary, establishing contact between the magnetic center of IDs and their externally accessible fiducials, thus enabling high-precision alignment. Through analysis of magnetic field distribution, self-calibration precision, and practical application of the MLK, the following conclusions are drawn: when the Hall probe is positioned within 0.5 mm of the magnetic field zero point inside the MLK, the measurement accuracy of the zero point for normal and skew quadrupole magnetic fields reaches 7 and 2 μm, respectively. Additionally, the self-measurement accuracy of the MLK is 10 and 4 μm in the transverse and vertical directions, respectively. These accuracies meet our usage requirements. The MLK demonstrates efficacy in aligning the magnetic center of High Energy Photon Source (HEPS) In-air undulators, achieving alignment accuracies of 16 μm in the transverse direction and 11 μm in the vertical direction, surpassing the 30 μm accuracy stipulated in the physical design. Furthermore, the device proves applicable for measuring the magnetic center of other types of HEPS insertion devices, including Cryogenic undulators.

Dynamic loading platforms coupled to ultra-high speed X-ray imaging at beamline ID19 of the European Synchrotron ESRF

ABSTRACT The intersection of dynamic compression, high-rate material response and X-ray science has seen rapid growth, leading to the establishment of specialized end-stations at international facilities such as Linac Coherent Light Source LCLS (Matter at Extreme Conditions – MEC) and Advanced Photon Source APS (Dynamic Compression Sector – DCS), both USA. Although these facilities excel in working with X-rays tailored for small material volumes (i.e. < 1 mm 3 ), it needs a different approach to delve into subsequent processes. This is particularly the case in the transition from the micro- to mesoscale: here the ESRF distinguishes itself. The large beam size (several cm2) of the ID19 beamline, in conjunction with a strong high energy component, source flux density, and outstanding imaging sensitivity, enables sub-surface visualization of engineering-scale structures as well as natural systems in representative volume, under high rate and shock. This is particularly valuable when studying materials with complex mesostructures and heterogeneities on relevant volumetric scales, which often dominate the dynamic material response. The study of the behavior of materials under dynamic loading presents a unique challenge due to inherently spanning over multiple lengths- and timescales. The evolution of sudden (thermo)mechanical excitation, starting from the lattice scale and progressing through grains, phase domains, and ultimately to structures, exhibits a spectrum of responses spanning from the microscopic to bulk length scales. Consequently, a diverse range of diagnostics as well as driver instrumentation is required to identify, study, and characterize this material response spectrum. This article shall introduce platforms available at beamline ID19 and underline their potential by selected showcase applications. Community access proposals such as the beamtime Block Allocation Group (BAG) allow for access in a routine manner.

Quantitative Investigation of Quantum Emitter Yield in Drop-Casted Hexagonal Boron Nitride Nanoflakes.

Single photon emitters (SPEs) are a key component for their use as pure photon source in quantum technologies. In this study, we investigate the generation of SPEs from drop-casted hexagonal boron nitride (hBN) nanoflakes, examining the influence of the immersion solution and the source of hBN. We show that, depending on the utilized supplier and solution, the number and quality of the emitters change. We perform a comprehensive optical characterization of the deposited nanoflakes to assess the quality of the generated SPEs. Importantly, we provide quantitative data on SPE yields, highlighting significant variations among solvents and different sources of hBN. We find that hBN from Merck drop-casted in acetone provided the best quality emitters with a g (2) < 0.1 and photoluminescence intensities above 300 kCounts/s. Their number of SPEs among all photon emitters was also the highest, with about 14%, rendering a total yield of about 1.25% of all drop-casted flakes. These numbers hold particular significance when evaluating drop-casting as a practical method for the generation of SPEs and their deposition and incorporation within existing nanophotonic systems. By choosing appropriate solvents and source materials' quality and yield of SPEs can be significantly increased, showcasing further optimization potential for the development of future quantum applications.

High-rate intercity quantum key distribution with a semiconductor single-photon source

Quantum key distribution (QKD) enables the transmission of information that is secure against general attacks by eavesdroppers. The use of on-demand quantum light sources in QKD protocols is expected to help improve security and maximum tolerable loss. Semiconductor quantum dots (QDs) are a promising building block for quantum communication applications because of the deterministic emission of single photons with high brightness and low multiphoton contribution. Here we report on the first intercity QKD experiment using a bright deterministic single photon source. A BB84 protocol based on polarisation encoding is realised using the high-rate single photons in the telecommunication C-band emitted from a semiconductor QD embedded in a circular Bragg grating structure. Utilising the 79 km long link with 25.49 dB loss (equivalent to 130 km for the direct-connected optical fibre) between the German cities of Hannover and Braunschweig, a record-high secret key bits per pulse of 4.8 × 10−5 with an average quantum bit error ratio of ~ 0.65% are demonstrated. An asymptotic maximum tolerable loss of 28.11 dB is found, corresponding to a length of 144 km of standard telecommunication fibre. Deterministic semiconductor sources therefore challenge state-of-the-art QKD protocols and have the potential to excel in measurement device independent protocols and quantum repeater applications.

Machine-learning-assisted efficient reconstruction of the quantum states generated from the Sagnac polarization-entangled photon source

Machine-learning-assisted efficient reconstruction of the quantum states generated from the Sagnac polarization-entangled photon source

The Linac Extension Area at the Advanced Photon Source

The Linac Extension Area has been developed into a beamline area for testing accelerator components and techniques. Beginning commissioning activities in February 2023, we have delivered the first electron beam to the Linac Extension Area at the Advanced Photon Source at 425 MeV. In the present work, we summarise the principal accelerator components and review safety controls of the Linac Extension Area.

DENNIS: a design and analysis tool for dynamic material x-ray diffraction experiments

We present DENNIS (Diffraction Experiment desigN and aNalysiS): a graphical software tool useful for the design and analysis of dynamic x-ray diffraction experiments, such as those performed on the Z Pulsed Power Facility, Thor Pulsed Power Generator, and Dynamic Compression Sector (DCS) of the Advanced Photon Source. DENNIS provides rapid powder and single-crystal diffraction pattern predictions and powder diffraction pattern image integration in three-dimensional geometries. Additional features include crystallographic information file reading, image processing, and synthetic diffraction pattern image generation. We overview the software's capabilities, detail the prediction and integration methodologies, and provide example implementations on Z and DCS experiments.

Development of a 166.6MHz β = 1 higher-order-mode-damped superconducting cavity.

The storage ring of the high energy photon source will be driven by five 166.6MHz β = 1 quarter-wave superconducting cavities operating at 4K. A higher-order-mode-damped superconducting cavity was designed with excellent rf and mechanical properties based on the successful development of the proof-of-principle cavity. The mechanical design of the dressed cavity was focused on addressing stress safety throughout the processes, tunability, frequency detuning due to pressure fluctuation, and Lorentz force, among other factors. A new liquid helium vessel was designed along with a comprehensive stiffening scheme to mitigate the surging peak stress on the cavity resulting from the significantly unequal beam pipe size. In the first batch, three cavities were manufactured, and surface preparations were carefully conducted to eliminate defects and etching traces while ensuring cleanliness. The cavity's Q0 at the design voltage of 1.5 MV reached 3.8 × 109 at 4K, comfortably surpassing the design goal. Field emission onset was not observed during the entire test up to a peak electric field of 60 MV/m, thanks to the optimized processing procedures. Subsequently, one cavity was welded with the newly designed helium vessel and vertically tested at 2K, achieving an rf performance comparable to the bare cavities, demonstrating the success of the jacketed cavity. This paper presents the design, fabrication, surface preparation, and cryogenic tests of the first higher-order-mode-damped 166.6MHz β = 1 superconducting cavity.

Development of vertical test stand for SRF cavities at PAPS

The vertical test stand (VTS) plays a crucial role in evaluating the performance of superconducting radio-frequency (SRF) cavities. The VTS at the Platform of Advanced Photon Source Technology R&D (PAPS) has been developed by the Institute of High Energy Physics, Chinese Academy of Sciences (IHEP). In this paper, the digitalization (based on Field Programmable Gate Array, FPGA) and integration functionalities of VTS was carried out, which simplified the vertical test and improved efficiency greatly. Several vertical tests have been conducted at this upgraded VTS successfully, which adopted digital self-excited loop (SEL) and Experimental Physics and Industrial Control System (EPICS).

The HEPS synchrotron unleashes new medical frontiers.

The High Energy Photon Source (HEPS) in Beijing achieved a beam energy of 6 GeV. This milestone enables groundbreaking advances in health sciences and various research fields, promising new insights into biological and quantum processes.

X-ray optics for the cavity-based X-ray free-electron laser.

A cavity-based X-ray free-electron laser (CBXFEL) is a possible future direction in the development of fully coherent X-ray sources. CBXFELs consist of a low-emittance electron source, a magnet system with several undulators and chicanes, and an X-ray cavity. The X-ray cavity stores and circulates X-ray pulses for repeated FEL interactions with electron pulses until the FEL reaches saturation. CBXFEL cavities require low-loss wavefront-preserving optical components: near-100%-reflectivity X-ray diamond Bragg-reflecting crystals, outcoupling devices such as thin diamond membranes or X-ray gratings, and aberration-free focusing elements. In the framework of the collaborative CBXFEL research and development project of Argonne National Laboratory, SLAC National Accelerator Laboratory and SPring-8, we report here the design, manufacturing and characterization of X-ray optical components for the CBXFEL cavity, which include high-reflectivity diamond crystal mirrors, a diamond drumhead crystal with thin membranes, beryllium refractive lenses and channel-cut Si monochromators. All the designed optical components have been fully characterized at the Advanced Photon Source to demonstrate their suitability for the CBXFEL cavity application.

Mango wiggler as a novel insertion device providing a large and symmetrical imaging field of view.

A novel insertion device is introduced, designated as the Mango wiggler, designed for synchrotron radiation (SR) imaging that provides a large field of view. This innovative device is constructed from two orthogonal planar wigglers with a small difference in their period lengths, eliciting the phase difference of the magnetic fields to incrementally transitions from 0 to π/2. Such a configuration enlarges the vertical divergence of the light source, as with the horizontal divergence. The appellation `Mango wiggler' derives from the distinctive mango-shaped contour of its radiation field. A comprehensive suite of theoretical analyses and simulations has been executed to elucidate the radiation properties of the Mango wiggler, employing SPECTRA and Mathematica as calculation tools. In conjunction with the ongoing construction of the High Energy Photon Source in Beijing a practical Mango wiggler device has been fabricated for utilization in SR imaging applications. Theoretical analyses were applied to this particular Mango wiggler to yield several theoretical conclusions, and several simulations were performed according to the measured magnetic field results.