Comparison of implosion core metrics: A 10 ps dilation X-ray imager vs a 100 ps gated microchannel plate

Simulation study of an x-ray sub-picosecond resolution detection system based on time-domain amplification

This study proposes what we believe to be a novel x-ray detection system that achieves a temporal resolution of 930 fs with photorefractive and four-wave mixing effects. The system comprises two parts: a signal-conversion system and signal-acquisition system. The signal-conversion system is based on the photorefractive effect, which converts x-ray evolution into the variation of infrared interference intensity. The signal-conversion sensor consists of ultra-fast response LT-GaAs and a high-resolution interference cavity, achieving a resolution of  767 fs. The signal-acquisition system consists of a time-domain amplification system based on four-wave mixing and a high-resolution signal-recording system with a resolution of 21 ps, providing a temporal resolution of 525 fs.

Numerical study and improvement of the dynamic performance of dilation x-ray imager

We present in this Note a numerical study on the dynamic performance of a Dilation X-ray Imager (DIXI). The DIXI including a photoelectron tube (PT) and a magnetic solenoid is modeled in 3D space. The initial parameters of the photoelectrons are sampled with a Monte Carlo code. The trajectories of the photoelectrons are calculated by using the particle-in-cell method, and the transit time spread (TTS) and temporal magnification are analyzed in detail. We have designed a PT with a double-microstrip structure and compared the performance of the double-microstrip PT with the traditional single-microstrip PT. The results show that the sensitivity of the TTS and the temporal magnification to the emission time of the photoelectrons can be significantly reduced by using the double-microstrip PT, resulting in an improvement of the time window. Therefore, the dynamic performance of the DIXI is improved.

Theoretical study on temporal and spatial performance of magnetic solenoid used in dilation x-ray imager

In the Dilation X-ray Imager (DIXI), which is characterized by an ultra-short gating time, a magnetic solenoid is used to keep the photoelectrons from defocusing during the drift process. The performance of the magnetic solenoid has an important influence on the performance of the DIXI. We present in this paper the efforts on studying the spatial and temporal performance of the magnetic solenoid used in the DIXI by tracking the photoelectrons with the particle-in-cell method. The initial parameters of the photoelectrons of the Au cathode were sampled with a Monte Carlo code. A novel magnetic solenoid with a shielding shell made of soft iron was proposed. We compared the performance of this solenoid with a normal solenoid. The simulation results of magnetic field distribution, spatial resolution, transit time spread, and temporal distortion were presented in detail to demonstrate that the performance of the DIXI can be significantly improved by using the magnetic solenoid with the proposed iron shell.

Measurement of dilation pulses using a pulse-dilation framing camera

A pulse-dilation framing camera (PFC) and its working principle are introduced. The influence of the dilation pulse on the exposure time is discussed. The measurement of the dilation pulse using the PFC are theoretically analyzed and experimentally verified. The waveform and the entire time history of the potential of the dilation pulse are simulated by the known dilation factors of the PFC in theory, with the potential deviation at the end of the dilation time of pulse being approximately 3.2%. In the experiment, the exposure time and dilation factors of the PFC are measured by using an array of fiber bundles and in taking many measurements, the waveform and the entire time history of the potential of dilation pulse are achieved by the dilation factors, with the potential deviation at the end of the dilation time of pulse being approximately 6.3%. The research results show that the experimental measurement is consistent with theoretical analysis, although there are some deviations, and it is feasible to measure the waveform and the entire time history of the potential of dilation pulse using the PFC. Moreover, the research may provide an idea for new applications of the framing camera.

GSK3787-Loaded Poly(Ester Amide) Particles for Intra-Articular Drug Delivery

Osteoarthritis (OA) is a debilitating joint disorder affecting more than 240 million people. There is no disease modifying therapeutic, and drugs that are used to alleviate OA symptoms result in side effects. Recent research indicates that inhibition of peroxisome proliferator-activated receptor δ (PPARδ) in cartilage may attenuate the development or progression of OA. PPARδ antagonists such as GSK3787 exist, but would benefit from delivery to joints to avoid side effects. Described here is the loading of GSK3787 into poly(ester amide) (PEA) particles. The particles contained 8 wt.% drug and had mean diameters of about 600 nm. Differential scanning calorimetry indicated the drug was in crystalline domains in the particles. Atomic force microscopy was used to measure the Young's moduli of individual particles as 2.8 MPa. In vitro drug release studies showed 11% GSK3787 was released over 30 days. Studies in immature murine articular cartilage (IMAC) cells indicated low toxicity from the drug, empty particles, and drug-loaded particles and that the particles were not taken up by the cells. Ex vivo studies on murine joints showed that the particles could be injected into the joint space and resided there for at least 7 days. Overall, these results indicate that GSK3787-loaded PEA particles warrant further investigation as a delivery system for potential OA therapy.

Synchronous gating in dilation x-ray detector without 1:1 image ratio

An x-ray detector using a pulse-dilation technology to achieve high temporal resolution is reported. The electron pulse generated from the photo-cathode (PC) is first dilated by a pulse-dilation device and then imaged onto the microchannel plate (MCP) by a magnetic lens imaging system. Finally, the dilated electron pulse is detected by a gated MCP. A resolution of 14 ps is achieved. In addition, the synchronous gating is studied in the dilation x-ray detector without a 1:1 image ratio. The results show that while the time of flight (TOF) of the electrons is identical, the MCP gating pulse can be timed relative to the PC excitation pulse to gate the dilated electron signal in a single area, and they are unsynchronized in the other area. To avoid the single area synchronization effect, the magnetic lens imaging system used in the detector should allow photoelectrons with a large energy spread to be imaged onto the MCP. This effect can also be reduced by using an MCP gating pulse with a width larger than 500 ps. Moreover, a 1:1 image ratio can avoid this effect. Furthermore, a decreasing electron TOF can eliminate the single area synchronization effect.

Dilation x-ray framing camera and its temporal resolution uniformity

An x-ray framing camera based on pulse-dilation technology is reported. This camera first dilates the electron signal generated from a pulsed photo-cathode (PC), and then detects the dilated electron pulse by using a gated microchannel plate (MCP). While the PC is only applied with a direct current (DC) voltage, the camera's temporal resolution without pulse-dilation is about 81 ps. It is the gated MCP's temporal resolution. While an excitation pulse is applied on the PC, the electron pulse's temporal width is dilated, and the resolution is improved to 14 ps. Furthermore, the camera's temporal resolution uniformity is measured and simulated. The results show a 3.5 × drop in temporal resolution along the pulse propagation direction, due to the 5 × decrease of the PC excitation pulse gradient.

The dilation aided single-line-of-sight x-ray camera for the National Ignition Facility: Characterization and fielding

Crystal x-ray imaging is frequently used in inertial confinement fusion and laser-plasma interaction applications as it has advantages compared to pinhole imaging, such as higher signal throughput, better achievable spatial resolution, and chromatic selection. However, currently used x-ray detectors are only able to obtain a single time resolved image per crystal. The dilation aided single-line-of-sight x-ray camera described here was designed for the National Ignition Facility (NIF) and combines two recent diagnostic developments, the pulse dilation principle used in the dilation x-ray imager and a ns-scale multi-frame camera that uses a hold and readout circuit for each pixel. This enables multiple images to be taken from a single-line-of-sight with high spatial and temporal resolution. At the moment, the instrument can record two single-line-of-sight images with spatial and temporal resolution of 35 μm and down to 35 ps, respectively, with a planned upgrade doubling the number of images to four. Here we present the dilation aided single-line-of-sight camera for the NIF, including the x-ray characterization measurements obtained at the COMET laser, as well as the results from the initial timing shot on the NIF.

Sub-nanosecond single line-of-sight (SLOS) x-ray imagers (invited)

A new generation of fast-gated x-ray framing cameras have been developed that are capable of capturing multiple frames along a single line-of-sight with 30 ps temporal resolution. The instruments are constructed by integrating pulse-dilation electron imaging with burst mode hybrid-complimentary metal-oxide-semiconductor sensors. Two such instruments have been developed, characterized, and fielded at the National Ignition Facility and the OMEGA laser. These instruments are particularly suited for advanced x-ray imaging applications in Inertial Confinement Fusion and High energy density experiments. Here, we discuss the system architecture and the techniques required for tuning the instruments to achieve optimal performance. Characterization results are also presented along with planned future improvements to the design.

Simplified model of pinhole imaging for quantifying systematic errors in image shape

We examine systematic errors in x-ray imaging by pinhole optics for quantifying uncertainties in the measurement of convergence and asymmetry in inertial confinement fusion implosions. We present a quantitative model for the total resolution of a pinhole optic with an imaging detector that more effectively describes the effect of diffraction than models that treat geometry and diffraction as independent. This model can be used to predict loss of shape detail due to imaging across the transition from geometric to diffractive optics. We find that fractional error in observable shapes is proportional to the total resolution element we present and inversely proportional to the length scale of the asymmetry being observed. We have experimentally validated our results by imaging a single object with differently sized pinholes and with different magnifications.

Calcitonin gene-related peptide (CGRP): A novel target for Alzheimer's disease

Alzheimer's disease (AD) is leading cause of death among older characterized by neurofibrillary tangles, oxidative stress, progressive neuronal deficits, and increased levels of amyloid-β (Aβ) peptides. Cholinergic treatment could be the best suitable physiological therapy for AD. Calcitonin gene-related peptide (CGRP) is a thirty-seven-amino acid regulatory neuropeptide resulting from different merging of the CGRP gene, which also includes adrenomedullin, amylin, calcitonin, intermedin, and calcitonin receptor-stimulating peptide. It is a proof for a CGRP receptor within nucleus accumbens of brain that is different from either the CGRP1 or CGRP2 receptor in which it demonstrates similar high-affinity binding for salmon calcitonin, CGRP, and amylin, a possession which is not shared by any extra CGRP receptors. Binding of CGRP to its receptor increases activated cAMP-dependent pkA and PI3 kinase, resulting in N-terminal fragments that are shown to exert complex inhibitory as well facilitator actions on nAChRs. Fragments such as CGRP1-4, CGRP1-5, and CGRP1-6 rapidly as well as reversibly improve agonist sensitivity of nAChRs without straight stimulating those receptors and produce the Ca2+ -induced intracellular Ca2+ mobilization. Renin-angiotensin-aldosterone system (RAAS)-activated angiotensin-type (AT4) receptor is also beneficial in AD. It has been suggested that exogenous administration of CGRP inhibits infiltration of macrophages and expression of various inflammatory mediators such as NFkB, IL-1b, TNF-α, iNOS, matrix metalloproteinase (MMP)-9, and cell adhesion molecules like intercellular adhesion molecule (ICAM)-1 which attenuates consequence of inflammation in AD. Donepezil, a ChEI, inhibits acetylcholinesterase and produces angiogenesis and neurogenesis, in the dentate gyrus of the hippocampus of WT mice after donepezil administration. However, none of the results discovered in CGRP-knockout mice and WT mice exposed to practical denervation. Therefore, selective agonists of CGRP receptors may become the potential candidates for treatment of AD.