Review of Scientific Instruments最新文献

Advances in x-ray free-electron laser and ultra-low-emittance synchrotron radiation facilities have enabled high-intensity, highly coherent x rays, driving significant progress in x-ray analytical techniques. To fully exploit these sources, reflective optics with sub-nanometer figure accuracy, capable of preserving both wavefront quality and beam intensity, are essential. Achieving such accuracy while accommodating increasingly steep and aspheric surface profiles required for next-generation optics poses substantial challenges in surface figure metrology. This study introduces a non-contact scanning profilometer that overcomes cumulative errors typically observed in conventional stitching interferometry. The instrument, referred to as the ZSP (Zero-method Scanning-probe Profilometer), integrates a chromatic confocal sensor with a measurement technique based on the zero method, effectively eliminating linearity errors in the sensor output. The ZSP achieves a root-mean-square reproducibility of 1.3 nm when measuring a steeply curved elliptical-cylindrical mirror with a sag of 105 μm and a grazing-incident angle distribution of 11 mrad. Furthermore, it was employed in the fabrication of the x-ray nanofocusing mirror, validating its designed focusing performance. The proposed approach is inherently applicable to the measurement of increasingly complex two-dimensional aspheric surfaces, thereby contributing to the advancement of ultra-precision metrology.

The Taishan Antineutrino Observatory (TAO) is a high-energy resolution reactor antineutrino experiment designed to measure the fine structure of the reactor antineutrino energy spectrum. It employs silicon photomultipliers (SiPMs) to detect photons produced by secondary particles from antineutrino interactions in a gadolinium-doped liquid scintillator. The physics event rate of the TAO is ∼520 Hz. However, the use of 4024 SiPM arrays results in a high dark noise event rate, leading to a total event rate of up to 1 GHz. This presents a significant challenge in the trigger system design: how to accurately and efficiently select rare effective physics events in real-time amidst a vast amount of noise. This paper introduces a fully digital hardware trigger system. The system features a flexible, reconfigurable two-level processing architecture, combined with a real-time triggering algorithm based on the multiplicity trigger criterion. The trigger system has been tested with the simulation data, and a preliminary joint test with the detector system has been completed. The results of the simulation test with a single module suggest that the trigger system can accurately extract the 1 kHz simulation physics events from the substantial amount of dark noise and upload the triggered data to the DAQ system. Besides, in the preliminary joint test, the trigger system accurately extract the given effective physics event data while compressing the hit rate of dark noise from 2 MHz to 500 Hz. The trigger system has been successfully installed and deployed at the TAO experimental site. It has undergone integrated debugging with the full-scale detector and Front-End Electronics (FEC), and preliminary data acquisition tests have been completed. The design objectives of the triggering system have been fulfilled, demonstrating its correctness and reliability in practical application scenarios.

We report on a scanned superconducting quantum interference device (SQUID) microscope operating in a cryogen-free cryostat, with the capability of up to forty RF connections with 20 GHz bandwidth to a device under test. The system utilizes planar gradiometric DC SQUIDs, which are fully shielded except for a pair of pickup coils with radii as small as 250 nm and have on-chip field coils allowing for susceptometry. The system noise is 1.3 μΦ0/Hz at the base temperature of 3.3 K. The sample temperature is variable, and both magnetometry and susceptibility measurements are simultaneously possible with the sample temperature above 40 K. Through the use of a cryogenic chip socket and silicon interposer, round-trip RF losses to a sample are ∼15 dB at 20 GHz. A combination of both active and passive magnetic shielding results in a residual magnetic field of less than 100 nT at the sample location.

Autocollimators are used in profilometers for the precise form measurement of beam-shaping optics for synchrotron light sources and x-ray free-electron lasers. This application requires using an aperture stop, typically 2.5 mm in diameter, which limits the footprint of the autocollimator's measuring beam on the optics to achieve a sufficiently high lateral resolution. Central to the development of profilometry has been the availability of commercial autocollimators, such as the Elcomat 3000 from Möller-Wedel Optical. Although autocollimators are generally not designed for use with small apertures, this device has proven capable and has become the de facto standard. Now that it has been replaced by the Elcomat 5000, we evaluate the performance of several autocollimators of this type at small apertures, including the characterization of instrument transfer functions with a chirped height profile. We demonstrate that the Elcomat 5000 is capable of repeatable angle measurements with a standard deviation of 0.014 arcsec at an aperture diameter of 1.6 mm, whereas the Elcomat 3000 achieves 0.03 arcsec at 2.5 mm, comparing models with modified reticle designs. We also investigate the influence of optical aberrations of the autocollimator's objective and their changes with the path length to the surface under test. We characterize the sensitivity of the angle measurement to changes in environmental parameters, in particular, barometric pressure. These efforts are aimed at approaching fundamental limits in the characterization of the shape of optical surfaces with autocollimator-based profilometers so that these are ready for characterizing the next generation of synchrotron and XFEL beamline optics.

We investigated proton emission from titanium hydride (TiH2) targets irradiated in vacuum by a 6-ns, 1064-nm Nd:YAG laser. Time-of-flight measurements with a Faraday cup and an electrostatic ion analyzer resolved distinct proton peaks at high pulse energies, with yields on the order of 109 protons per shot. Systematic scans over pulse energy and up to 1000 repeated shots showed that, while the peak amplitude gradually decreased, the integrated proton number remained nearly constant. This behavior is consistent with surface-induced broadening of the plasma expansion while bulk hydrogen is replenished by diffusion and repeated ablation of fresh TiH2 layers. Using the measured proton numbers and pulse widths, a simple direct-plasma-injection-style scaling indicates peak currents of ∼100 mA and sub-microsecond pulse durations. The pulse structure and yield satisfy key ultra-high-dose-rate criteria and, together with sustained output over 1000 shots, support TiH2-based laser ion sources as practical candidates for FLASH-therapy (ultra-high-dose-rate)-oriented studies and injector development using direct plasma injection.

Double multilayer monochromators for high-flux, high-energy x-ray imaging have been developed at SPring-8. Although state-of-the-art mirrors are fabricated with root-mean-square (RMS) figure errors of 100 pm, they still introduce horizontal stripes in beam images. Suppressing these stripes remains a significant challenge, as it requires controlling figure errors to levels well beyond current fabrication capabilities. To evaluate the impact of such errors on high-energy x-ray beams, given the partially coherent nature of the 100 keV pink beam, we performed coherent mode decomposition to represent realistic radiation fields. Wave field propagation was computed using the angular spectrum method, which is computationally efficient. The simulation results were in agreement with the measured beam image in terms of beam size and intensity variation. Further simulations using modulated spatial spectra of figure errors demonstrated that suppressing mid-spatial-frequency components (2-50 mm) to below 10 pm RMS reduced the intensity variation to 1%.

Nuclear activation is a well-established technique for inferring neutron yields in laser direct-drive deuterium-tritium (DT) and deuterium-deuterium (D2) implosions at the OMEGA Laser Facility. Zirconium has long been considered an excellent candidate for measuring DT neutron fusion yields by observing decays of the 90Zr(n,2n)89Zr ground-state reaction. As it has a higher energy threshold than present activation detectors utilizing copper, zirconium provides a means to infer primary neutron yields that are less susceptible to being skewed due to neutron scattering within the experimental environment. However, with a 78.41-h half-life, it is not operationally practical to utilize this reaction for OMEGA experiments, which have a 1-h shot cycle. Zirconium's 90Zr(n,2n)89mZr reaction presents itself as a viable candidate to infer neutron yields within a shot cycle, given its half-life of 4.16 min. We present an overview of the approach and methodology, utilizing first principles techniques, to infer the primary neutron yields from OMEGA DT fusion experiments by using both the isomeric and the ground-state reaction. Yields inferred from both reactions are compared, which are in good agreement between the two.

An analytical model of a square or a rectangular aperture iron dominated quadrupole electromagnet is presented with a fixed core aperture for any coil size, with a strength ∼70% of hyperbolic iron pole quadrupoles for the same excitation and current density. It is up to four times stronger than the Panofsky quadrupole electromagnet with better field quality for square aperture, same excitation, and low current density with ambient air cooled coils. Similar to the gap tuning in Halbach quadrupoles, the presented model can reduce the first harmonic 12th pole field, by fine-tuning the coil and core geometry with an air gap. For the square aperture Panofsky quadrupole too, a coil design is presented to cancel the 12th pole. For rectangular aperture, up to the aspect ratio of 1:4, the model is 40% stronger but with more octupoles. The presented model is a stronger alternative to the Panofsky quadrupole electromagnet using thick air cooled coils with low current density and compares better with conventional hyperbolic iron pole quadrupoles.

Atomic cells made by anodically bonding silicon and borosilicate glasses are widely used in atomic devices. One inherent problem in these cells is that the silicon material blocks beams with wavelengths shorter than 1000 nm, which limits available optical access when alkali metal atoms are involved. In this work, we investigate the possibility of the silicon carbide material as an alternative to silicon materials in fabricating anodically bonded cells. We demonstrate that the optical, thermal, and mechanical properties of silicon carbide help to improve the performance of atomic devices in certain applications.

Atomic vapor cells with anti-relaxation coatings (ARCs) are critical components in atomic devices, such as atomic clocks and atomic magnetometers. However, widespread adoption of these vapor cells is hindered by poor performance convergence and limited manufacturing yields, stemming from the lack of systematic preparation protocols. Herein, we present an in situ monitoring system that enables real-time optimization of the spin coherence time and vapor density during the preparation of ARC vapor cells. By integrating real-time process monitoring and closed loop feedback control into cell curing, our system dynamically adjusts the curing parameters to optimize the spin coherence time to an order of magnitude of seconds. The proposed system can potentially improve the manufacturing yield of ARC vapor cells and provides a foundational platform for the advancement of quantum sensors.