Energy Jitter Research Articles

In situ/operando method for energy stability measurement of synchrotron radiation.

A novel in situ/operando method is introduced to measure the photon beam stability of synchrotron radiation based on orthogonal diffraction imaging of a Laue crystal/analyzer, which can decouple the energy/wavelength and Bragg angle of the photon beam using the dispersion effect in the diffraction process. The method was used to measure the energy jitter and drift of the photon beam on BL09B and BL16U at the Shanghai Synchrotron Radiation Facility. The experimental results show that this method can provide a fast way to measure the beam stability of different light sources including bending magnet and undulator with meV-level energy resolution and ms-level time response.

Cancellation of klystron-induced energy and arrival-time variations in linear accelerators with arc-type bunch compressors

We explain how the accelerating field amplitude and phase vary with modulator voltage in pulsed radio frequency high-power amplifiers based on klystron tubes. Changes in modulator voltage give rise to correlated changes of amplitude and phase, affecting the properties of the accelerated beam, in particular energy, arrival time, and bunch duration. We show, both theoretically and experimentally, that there exists a postcrest acceleration phase (the ) where the changes of beam energy due to phase and amplitude shifts caused by modulator-voltage variations cancel out. When accelerating at the magic angle, the klystron modulator voltage jitter no longer contributes to energy and arrival-time jitter in the accelerator. Off-crest operation at the magic angle can be implemented for bunch compression schemes in accelerators with arc-type bunch compressors, which have positive momentum compaction. The experimental results, obtained at the MAX IV laboratory, show the benefit of operating close to the magic angle in arc-type bunch compressors. In a direct measurement of normalized electron-energy jitter, the energy jitter was reduced by a factor of 1.8 down to 8.2×10−5 when operating at the magic angle. Published by the American Physical Society 2024

Numerical studies for EuPRAXIA@SPARC_LAB plasma beam driven working point

The realization of a plasma based user facility on the model of EuPRAXIA@SPARC_LAB requires to design a working point for the operation that allows to get an high accelerating gradient preserving a low emittance and low energy spread of the accelerated beam. Such beam is supposed to pilot a soft x-ray free electron laser with a wavelength of 2-4 nm. In this work several simulation scans are presented, varying at the same time the plasma density and driver-witness separation in order to show that, in a realistic working point for EuPRAXIA@SPARC_LAB, it is possible to find an ideal compromise for a witness with a peak current ¿1kA that allows to preserve the energy spread of the core (80% of the charge) below 0.1%, while maintaining an accelerating gradient inside the plasma module around of 1 GV/m. The study is completed with a parametric analysis with the aim of establishing the stability requirements of the RF working point and the plasma channel in order to preserve the energy jitter at the same level of the energy spread.

Characterization of single-pulse photon energy and photon energy jitter at the Shanghai soft X-ray Free-Electron Laser

Characterization of single-pulse photon energy and photon energy jitter at the Shanghai soft X-ray Free-Electron Laser

Intelligent Spectrum Sharing and Sensing in Cognitive Radio Network by Using AROA (Adaptive Rider Optimization Algorithm)

Wireless spectrum has been allocated to licensees for large geographic areas on a long-term basis in recent years. Cognitive Radio Networks (CRN) will offer mobile users with a huge amount of available bandwidth. Due to spectrum management issues such as spectrum sensing and sharing, CRN networks pose some challenges. Hence in this paper, Adaptive Rider Optimization (AROA) is developed to improve the energy efficiency for different spectrum sensing conditions. The proposed algorithm is utilized to compute the sensing time, sequence length, and detection threshold. In order to detect the spectrum with optimal values of transmission power and sensing bandwidth, the AROA uses the adaptive threshold detection method. The spectrum sensing and sharing of the CRN network are achieved with the help of the AROA algorithm. The proposed method is implemented in MATLAB and the performances such as Normalized Energy consumption, delay, SNR, Jitter, blocking probability, convergence analysis, and Throughput are evaluated. The proposed method is contrasted with the existing methods such as Whale Optimization Algorithm (WOA), Particle Swarm Optimization (PSO), and Grey Wolf Optimization (GWO), respectively.

An application of a cavity-based beam arrival time measurement system: Beam energy measurement

A high-resolution cavity-based beam arrival/flight time measurement system has been established at SXFEL (Shanghai soft X-ray free-electron laser facility). During the development of the system, a correlation between the energy jitter and the beam flight time jitter was found which inspires and motivates us to further explore the possibility of using the beam arrival/flight time measurement system to measure the beam energy. On the one hand, beam energy is one of the most fundamental and critical parameters for accelerator facilities. Only precise handling of the beam energy enables precise control of the FEL (free-electron laser) radiation wavelength. On the other hand, there are only a few methods for beam energy measurement. The profile-based beam energy measurement method is commonly used but is interceptive. The BPM-based beam energy measurement scheme is non-interceptive but has a limited dynamic range and requires initial beam position calibration. This paper reports a promising application of a cavity-based high-resolution beam arrival/flight time measurement system: non-intercepting wide-range beam energy measurement. A brief introduction of the method principle and system implementation has been covered in this article. Moreover, a beam-based preliminary test has been performed and the test results show a linear correlation between the beam energy and the beam flight time under the current system configuration. The measured linear factor is 0.692 ps/MeV. In addition, the relative bunch energy measurement resolution is 0.0001.

Highly coherent, flat, and broadband time-stretched swept source based on extra-cavity spectral shaping assisted by a booster semiconductor optical amplifier.

We demonstrate a flat broadband time-stretched swept source based on extra-cavity spectral shaping. By adjusting the polarization-dependent gain profile and driving current of the booster optical amplifier (BOA), extra-cavity spectral shaping is optimized to generate output with a 1-dB bandwidth of ∼100 nm, 3-dB bandwidth of ∼140 nm and output power of ∼21.4 mW. The short-term and long-term stabilities are characterized. The average cross correlation of 183,485 round trips is 0.9997 with a standard deviation of 2×10-5, indicating high single-shot spectral similarity and high coherence. The noise floor of relative spectral energy jitter is -141.7 dB/Hz, indicating a high short-term spectral energy stability. The proposed highly stable flat broadband time-stretched swept source is applied to an optical coherence tomography (OCT) system. The axial resolution is 10.8 µm. The proposed swept source can serve as excellent light sources in ultra-fast coherent detection systems for high precision sensing and imaging.

Energy Compression and Stabilization of Laser-Plasma Accelerators.

Laser-plasma accelerators outperform current radio frequency technology in acceleration strength by orders of magnitude. Yet, enabling them to deliver competitive beam quality for demanding applications, particularly in terms of energy spread and stability, remains a major challenge. In this Letter, we propose to combine bunch decompression and active plasma dechirping for drastically improving the energy profile and stability of beams from laser-plasma accelerators. Realistic start-to-end simulations demonstrate the potential of these postacceleration phase-space manipulations for simultaneously reducing an initial energy spread and energy jitter of ∼1-2% to ≲0.1%, closing the beam-quality gap to conventional acceleration schemes.

Big Data Analytics for MANET Based Sustainable Smart Healthcare Solution

Objective: Collaboration of most promising upcoming technologies like big data and Internet of Things (IoT) plays a significant role in the sustainable development of the smart world. One of the important applications is the amalgamation of such technology in the e-healthcare sector, where private information is being transferred from one end device to other equipment. Sensors and different other instruments engaged in the e-healthcare sector, for transferring important vital information of the patients, are categorized as Wireless Mesh Networks (WMN). An attacker can introduce many malicious activities via different types of attacks; ultimately, such activities can produce an outturn in Denial of Service (DoS) of important routines which need to be completed in stipulated time. Therefore, it is important to showcase the effect of various attacks affecting the routing methodology of the protocols of such networks. Methods: In this research study, the most suitable routing protocol to handle DDoS attacks is simulated and estimated for the Quality of Service (QoS) in smart network infrastructure in terms of energy consumption and jitter in changing nodes scenario, which aids in providing implications to enhance existing protocols and alleviate the consequence of DDoS instigated by such attacks. Results: The performance of AODV (Adhoc on Demand Vector), SAODV (Secured Adhoc On Demand) and HWMP (Hybrid Wireless Mesh Protocol) is compared and tabularized, which are the most popularly utilized protocols in the healthcare environment. Conclusion: The simulation results show that the HWMP outperformed well than the other two routing protocols in terms of evaluation metrics, namely energy consumption and jitter, which could be considered much less vulnerable against DDoS attacks prevailing in the sustainable healthcare sector.

Arrival time fluctuation of the SwissFEL photocathode laser: characterization by a single color balanced cross correlator.

The arrival time jitter and drift of the photocathode drive laser has an important impact on the performance of a Free-Electron-Laser (FEL). It adversely affects the beam energy jitter, bunch length jitter and bunch arrival time jitter, which becomes especially important for pump-probe experiments with femtosecond time resolution. To measure both parameters background free and stabilize the drift of the Yb:CaF2 based laser we use a well designed balanced optical cross correlator. In this paper we present our results using this device and focus particularly on the performance of the amplifier. We achieve a laser drift of less than 200 fs during 60 h, a 4.5 fs rms jitter of the amplifier relative to its seeding oscillator and 11 fs rms for the whole laser relative to a reference clock integrated from 2 mHz to 100 Hz.

High stability 500 Hz MOPA system for planar laser-induced fluorescence

A high pulse energy laser diode-pumped Nd:YAG master oscillator power amplifier (MOPA) laser is demonstrated. The maximum energy of 68 mJ, 9.6 ns, 1064 nm laser at a pulse repetition frequency of 500 Hz is achieved by utilizing the amplifier composed of three LD side-pumped Nd:YAG modules. Moreover, the maximum laser energy of 35.6 mJ is obtained at 532 nm by employing a KTP crystal as a frequency doubler. When ambient temperature ranges from 5 °C to 45 °C, the master oscillator has a pulse energy jitter of <5%. During the shake-environment test, the maximum-pulse-energy jitter of the MOPA laser is less than 2%. The developed MOPA laser has been used in a laser-induced fluorescence system and the variation of the flow field is obtained at a repetition rate of 500 Hz.

Data analysis procedures for time-resolved x-ray photoelectron spectroscopy at a SASE free-electron-laser

The random nature of self-amplified spontaneous emission (SASE) is a well-known challenge for x-ray core level spectroscopy at SASE free-electron lasers (FELs). Especially in time-resolved experiments that require a combination of good temporal and spectral resolution the jitter and drifts in the spectral characteristics, relative arrival time as well as power fluctuations can smear out spectral-temporal features. We present a combination of methods for the analysis of time-resolved photoelectron spectra based on power and time corrections as well as self-referencing of a strong photoelectron line. Based on sulfur 2p photoelectron spectra of 2-thiouracil taken at the SASE FEL FLASH2, we show that it is possible to correct for some of the photon energy drift and jitter even when reliable shot-to-shot photon energy data is not available. The quality of pump–probe difference spectra improves as random jumps in energy between delay points reduce significantly. The data analysis allows to identify coherent oscillations of 1 eV shift on the mean photoelectron line of 4 eV width with an error of less than 0.1 eV.

Design of speed control system for intelligent sorting conveyor belt of coal gangue

With the development of technology, the application of intelligent coal gangue sorting is more and more favored by coal mining enterprises. The coal gangue intelligent sorting system has higher requirements on the coal conveyor belt. The traditional transmission system has the problems of slow speed response, unstable operation, high energy consumption and jitter in the process of speed change. Using PLC, touch screen, frequency converter, RS-485, sensors and so on, the speed control and speed monitoring system of belt transport mechanism is constructed. By analyzing the error law of the system speed control and using Numpy system analysis and calculation, speed pre-compensation can be made. Then by controling speed precision through the PID and monitoring display through the time-speed curve, the real-time automation gives an alarm for abnormal speed situation. According to the speed requirement of the intelligent sorting system of coal gangue, the system can quickly reach the predetermined speed value, and effectively eliminate the shaking phenomenon in the process of changing speed. The system has strong universality, easy maintenance, and stable speed control, which is conducive to improving the reliability and efficiency of the intelligent sorting system for coal gangue and reduceing transmission mechanism wear caused by dithering.

Design of a prototype laser-plasma injector for an electron synchrotron

The present state of progress in laser wakefield acceleration encourages considering it as a practical alternative to conventional particle accelerators. A promising application would be to use a laser-plasma accelerator as an injector for a synchrotron light source. Yet, the energy spread and jitter of the laser-plasma beam pose a significant difficulty for an efficient injection. In this paper, we propose a design of a prototype injector to deliver 500 MeV low-intensity electron bunches to the DESY-II electron synchrotron. The design utilizes presently available conventional accelerator technology, such as a chicane and an X-band radio frequency cavity, to reduce the energy spread and jitter of the electron beam down to a sub-per-mille level.

Optical system design for a hyperspectral imaging lidar using supercontinuum laser and its preliminary performance.

To meet the urgent need for surveying and mapping using remote sensing instruments, a hyperspectral imaging lidar using a supercontinuum laser is proposed. This novel lidar system can solve the problem of the mismatching of the traditional lidar retrieved elevation data and hyperspectral data obtained by passive imaging instruments. The optical design of the lidar receiving system is described, developed, and tested in this study. An off-axis parabolic mirror is used as the receiving telescope of the system, and a transmissive grating is used to split the received hyperspectral light to each detection channel. A fiber array equipped with a micro-lens is used to guide the split light to the detectors. In practice, several fibers can be coupled to one detector according to the wavelength sensitivity of different objects. A reference laser is used to monitor the possible energy jitter of each transmitted laser pulse in real time. A spectrum calibration of the receiving system is accomplished in the laboratory, and radiation calibration is applied by receiving the backscattered light reflected by a standard white board. The spectral resolution of a single fiber is approximately 3 nm. An outdoor 500-m distance experiment was carried out for green and yellow leaves in day and evening settings. During the experiment, the wavelength of the laser was 460-900 nm. The reflection spectra collected by the lidar system in day and evening were consistent, indicating that the design of the optical receiving system is reliable and can be used for airborne hyperspectral imaging lidar.

Beyond integration: modeling every pixel to obtain better structure factors from stills

Most crystallographic data processing methods use pixel integration. In serial femtosecond crystallography (SFX), the intricate interaction between the reciprocal lattice point and the Ewald sphere is integrated out by averaging symmetrically equivalent observations recorded across a large number (104-106) of exposures. Although sufficient for generating biological insights, this approach converges slowly, and using it to accurately measure anomalous differences has proved difficult. This report presents a novel approach for increasing the accuracy of structure factors obtained from SFX data. A physical model describing all observed pixels is defined to a degree of complexity such that it can decouple the various contributions to the pixel intensities. Model dependencies include lattice orientation, unit-cell dimensions, mosaic structure, incident photon spectra and structure factor amplitudes. Maximum likelihood estimation is used to optimize all model parameters. The application of prior knowledge that structure factor amplitudes are positive quantities is included in the form of a reparameterization. The method is tested using a synthesized SFX dataset of ytterbium(III) lysozyme, where each X-ray laser pulse energy is centered at 9034 eV. This energy is 100 eV above the Yb3+ L-III absorption edge, so the anomalous difference signal is stable at 10 electrons despite the inherent energy jitter of each femtosecond X-ray laser pulse. This work demonstrates that this approach allows the determination of anomalous structure factors with very high accuracy while requiring an order-of-magnitude fewer shots than conventional integration-based methods would require to achieve similar results.

Toward monochromated sub-nanometer UEM and femtosecond UED

A preliminary design of a mega-electron-volt (MeV) monochromator with 10−5 energy spread for ultrafast electron diffraction (UED) and ultrafast electron microscopy (UEM) is presented. Such a narrow energy spread is advantageous in both the single shot mode, where the momentum resolution in diffraction is improved, and the accumulation mode, where shot-to-shot energy jitter is reduced. In the single-shot mode, we numerically optimized the monochromator efficiency up to 13% achieving 1.3 million electrons per pulse. In the accumulation mode, to mitigate the efficiency degradation caused by the shot-to-shot energy jitter, an optimized gun phase yields only a mild reduction of the single-shot efficiency, therefore the number of accumulated electrons nearly proportional to the repetition rate. Inspired by the recent work of Qi et al. (Phys Rev Lett 124:134803, 2020), a novel concept of applying reverse bending magnets to adjust the energy-dependent path length difference has been successfully realized in designing a MeV monochromator to achieve the minimum energy-dependent path length difference between cathode and sample. Thanks to the achromat design, the pulse length of the electron bunches and the energy-dependent timing jitter can be greatly reduced to the 10 fs level. The introduction of such a monochromator provides a major step forward, towards constructing a UEM with sub-nm resolution and a UED with ten-femtosecond temporal resolution. The one-to-one mapping between the electron beam parameter and the diffraction peak broadening enables a real-time nondestructive diagnosis of the beam energy spread and divergence. The tunable electric–magnetic monochromator allows the scanning of the electron beam energy with a 10−5 precision, enabling online energy matching for the UEM, on-momentum flux maximizing for the UED and real-time energy measuring for energy-loss spectroscopy. A combination of the monochromator and a downstream chicane enables “two-color” double pulses with femtosecond duration and the tunable delay in the range of 10 to 160 fs, which can potentially provide an unprecedented femtosecond time resolution for time resolved UED.

A novel nondestructive diagnostic method for mega-electron-volt ultrafast electron diffraction

A real-time, nondestructive, Bragg-diffracted electron beam energy, energy-spread and spatial-pointing jitter monitor is experimentally verified by encoding the electron beam energy and spatial-pointing jitter information into the mega-electron-volt ultrafast electron diffraction pattern. The shot-to-shot fluctuation of the diffraction pattern is then decomposed to two basic modes, i.e., the distance between the Bragg peaks as well as its variation (radial mode) and the overall lateral shift of the whole pattern (drift mode). Since these two modes are completely decoupled, the Bragg-diffraction method can simultaneously measure the shot-to-shot energy fluctuation from the radial mode with 2·10−4 precision and spatial-pointing jitter from the drift mode having wide measurement span covering energy jitter range from 10−4 to 10−1. The key advantage of this method is that it allows us to extract the electron beam energy spread concurrently with the ongoing experiment and enables online optimization of the electron beam especially for future high charge single-shot ultrafast electron diffraction (UED) and ultrafast electron microscopy (UEM) experiments. Furthermore, real-time energy measurement enables the filtering process to remove off-energy shots, improving the resolution of time-resolved UED. As a result, this method can be applied to the entire UED user community, beyond the traditional electron beam diagnostics of accelerators used by accelerator physicists.

Multienergy operation analysis in a superconducting linac based on off-frequency detune method

The free-electron laser facilities driven by a superconducting radio-frequency (SRF) linac provide high-repetition-rate electron beam, which makes it feasible to feed multiple undulator lines at the same time. In this paper, we study a method of controlling the energy of multiple electron bunches by off-frequency detuning in the SRF linac. Based on the theoretical analysis, we present the available discrete frequency detunes and the optimal linac energy allocation solutions with given energy overhead and periodic energy pattern. The required off-frequency detune is not larger than half of the beam repetition rate, which can be realized with the frequency tuner in SRF cavities. We adopt the configuration of the high energy upgrade of the Linac Coherent Light Source II (LCLS-II-HE) as an example to discuss the possible schemes in practice to support two undulator lines simultaneously. We also discuss the energy jitter increase due to the off-crest acceleration, the tunable energy range with fixed total SRF linac energy capacity, the beam energy chirp and lattice design for multienergy beam transport.

Experimental observations of seed growth and accompanying pedestal contamination in a self-seeded, soft x-ray free-electron laser

Measurements of the soft x-ray, self-seeding spectrum at the Linac Coherent Light Source (LCLS) free-electron laser generally display a pedestal-like distribution around the central seeded wavelength. This pedestal limits the spectral purity and can negatively affect some user applications not employing a post-undulator monochromator. In this paper, we investigate the detailed experimental characteristics of both the amplified seed and its accompanying pedestal using data from a number of separate LCLS shifts over the 2015-2018 time period. We find that the amplified seed shows excellent wavelength stability and an exponential growth rate whose dependence upon energy detuning is consistent with theory. The pedestal's spectral distribution and integrated strength vary strongly shot by shot, independent of electron beam energy jitter. Its shot-averaged strength relative to that of the seed grows at least linearly with $z$ and can approach values of 15% or more. The pedestal is comprised of two separate components: (1) normal self-amplified spontaneous emission (SASE) whose total strength is nominally insensitive to energy detuning and laser heater (LH) strength; (2) sideband-like emission whose strength positively correlates with that of the amplified seed and negatively with energy detuning and LH strength. We believe this latter, non-SASE component arises from comparatively long wavelength (i.e., $\ensuremath{\lambda}\ensuremath{\sim}0.3--3\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$) amplitude and phase modulations of the main seeded radiation line. Its shot to shot variability and LH sensitivity suggests an origin connected to growth of the longitudinal microbunching instability on the electron beam.