Slow Extraction Research Articles

Exploring the potential of resonance islands and bent crystals for a slow extraction from circular hadron accelerators

New developments in accelerator physics have broadened the set of available techniques for manipulating charged-particle beams. Adiabatic trapping and transport of a beam in resonance islands has been studied and successfully implemented at the CERN Proton Synchrotron to perform multiturn extraction. Bent crystals have been successfully installed in the CERN Large Hadron Collider, improving the cleaning performance of the collimation system, and at the CERN Super Proton Synchrotron for reducing losses at the extraction septum in the case of slow extraction. In this Letter, we discuss the potential of the combined use of resonance islands and bent crystals to devise a technique to perform slow extraction in circular hadron accelerators. The proposed approach is promising, particularly for applications with high-intensity beams, as it could dramatically reduce the losses on the extraction devices. Published by the American Physical Society 2024

Layer-wise-residual-driven approach for soft sensing in composite dynamic system based on slow and fast time-varying latent variables

Driven by the requirements for a comprehensive understanding of composite dynamic systems in industrial processes, this paper investigates a new soft sensor for quality prediction based on slow and fast time-varying latent variables extraction using layer-wise residuals. First, the slow feature partial least squares were expanded into long-term dependency by introducing explicit expressions of the potential state of the process into the objective function. Then, the multilayer regression model for exploring composite dynamics driven by layer-wise residuals is developed using a serial structure that can extract both slow and fast time-varying latent variables that are completely orthogonal. Finally, the exponential-weighted partial least squares are proposed for extracting fast time-varying dynamic latent variables by learning the exponential decay properties of the time-series data correlation. Case studies on the industrial debutanizer and sulfur recovery unit show that the prediction accuracy of the proposed approach outperforms traditional methods.

Fast and Optimal Extraction for Sparse Equality Graphs

Equality graphs (e-graphs) are used to compactly represent equivalence classes of terms in symbolic reasoning systems. Beyond their original roots in automated theorem proving, e-graphs have been used in a variety of applications. They have become particularly important as the key ingredient in the popular technique of equality saturation, which has notable applications in compiler optimization, program synthesis, program verification, and symbolic execution, among others. In a typical equality saturation workflow, an e-graph is used to store a large number of equalities that are generated by local rewrites during a saturation phase, after which an optimal term is extracted from the e-graph as the output of the technique. However, despite its crucial role in equality saturation, e-graph extraction has received relatively little attention in the literature, which we seek to start addressing in this paper. Extraction is a challenging problem and is notably known to be NP-hard in general, so current equality saturation tools rely either on slow optimal extraction algorithms based on integer linear programming (ILP) or on heuristics that may not always produce the optimal result. In fact, in this paper, we show that e-graph extraction is hard to approximate within any constant ratio. Thus, any such heuristic will produce wildly suboptimal results in the worst case. Fortunately, we show that the problem becomes tractable when the e-graph is sparse, which is the case in many practical applications. We present a novel parameterized algorithm for extracting optimal terms from e-graphs with low treewidth, a measure of how “tree-like” a graph is, and prove its correctness. We also present an efficient Rust implementation of our algorithm and evaluate it against ILP on a number of benchmarks extracted from the Cranelift benchmark suite, a real-world compiler optimization library based on equality saturation. Our algorithm optimally extracts e-graphs with treewidths of up to 10 in a fraction of the time taken by ILP. These results suggest that our algorithm can be a valuable tool for equality saturation users who need to extract optimal terms from sparse e-graphs.

Excitation of nonlinear second order betatron sidebands for knock-out slow extraction at the third-integer resonance

Radio frequency knock out resonant slow extraction is a standard method for extracting stored particle beams from synchrotrons by transverse excitation. Classically, the beam is excited with an rf field comprising a frequency band around one of the betatron sidebands. This article demonstrates that the third-integer resonance commonly used for the slow extraction induces nonlinear motion, resulting in the appearance of additional sidebands of higher order at multiples of the betatron tune. Measured and simulated beam spectra are presented, revealing these sidebands and the beam’s response to being excited at first and second order sidebands. The feasibility of using a second order sideband for the purpose of slow extraction is demonstrated. This results in a significant improvement in the temporal structure (spill quality) of the extracted beam, but at the cost of higher excitation power requirements. This is observed both experimentally and in tracking simulations. The mechanism behind the observed improvement is explained using beam dynamics simulations. Published by the American Physical Society 2024

Distinguishing carrier transport and interfacial recombination at perovskite/transport-layer interfaces using ultrafast spectroscopy and numerical simulation

In perovskite solar cells, photovoltaic action is created by charge transport layers (CTLs) either side of the light-absorbing metal halide perovskite semiconductor. Hence, the rates for desirable charge extraction and unwanted interfacial recombination at the perovskite-CTL interfaces play a critical role for device efficiency. Here, the electrical properties of perovskite-CTL bilayer heterostructures are obtained using ultrafast terahertz and optical studies of the charge carrier dynamics after pulsed photoexcitation, combined with a physical model of charge carrier transport that includes the prominent Coulombic forces that arise after selective charge extraction into a CTL, and cross-interfacial recombination. The charge extraction velocity at the interface and the ambipolar diffusion coefficient within the perovskite are determined from the experimental decay profiles for heterostructures with three of the highest-performing CTLs, namely C60, PCBM and Spiro-OMeTAD. Definitive targets for the further improvement of devices are deduced: fullerenes deliver fast electron extraction, but suffer from a large rate constant for cross-interface recombination or hole extraction. Conversely, Spiro-OMeTAD exhibits slow hole extraction but does not increase the perovskite’s surface recombination rate, likely contributing to its success in solar cell devices. Published by the American Physical Society 2024

Generation of 1.6 GeV single-particle proton beams

We present a scattering slow extraction method employing a rotating foil in the Rapid Cycling Synchrotron (RCS) to produce a stable 1.6 GeV single-particle proton beam at CSNS. The foil scatters particles on the beam’s edge over multiple turns, with those at large scattering angles being separated and extracted through a Lambertson magnet. By adjusting the scatter foil’s rotational speed and position, we can precisely control the intensity and repetition rate of the extracted beam. This approach enables the efficient extraction of extremely low-intensity proton beams from CSNS-II/RCS. By setting single-particle collimators in the downstream beamline, a single-particle proton beam is achieved. Using 4y, we simulated the scattering slow extraction process in detail, confirming that a stable 1.6 GeV single-particle proton beam can be extracted, the beam energy can be adjusted from 0.8 to 1.6 GeV using the degrader, the time interval between adjacent single protons can be adjusted from hundreds of nanoseconds to tens of microseconds, to meet the needs of different experiments. Both the beam loss and the residual radiation doses are kept at low levels. Published by the American Physical Society 2024

Fabrication of Efficient and Simple-Structured Perovskite Solar Cells Using a Multifunctional Biocolina Surface Treatment.

The electron transport layer (ETL)-free perovskite solar cells (PSCs) have gained significant interest by simplifying the manufacture process and reducing the time/energy required for the fabrication of ETLs. Unfortunately, the performance of these ETL-free PSCs still lags behind those of the conventional counterparts due to the slow electron extraction and undesired interfacial charge recombination loss at the buried interface. In this work, a facile and multifunctional biocolina thin layer is incorporated on the bottom electrodes to regulate the interface energy level alignment by forming an interface dipole layer, resulting in a suppressed nonradiative recombination and an improved charge extraction. Furthermore, the biocolina thin layer possess the capability to passivate the surface defects within the perovskite films while simultaneously facilitate the formation of perovskite crystals. Consequently, a remarkable enhancement in photovoltaic performance is observed in the biocolina-based ETL-free PSCs with an increase from 15.96 % to an outstanding 20.01 %. Additionally, the biocolina extends the stability and relieves the hysteresis effect through the interface defect passivation and inhibition of interface charge accumulation. This research contributes to the development of cost-effective, simplified designs for highly efficient ETL-free PSCs by modifying the bottom electrodes.

Investigation and improvement of spill quality at XiPAF synchrotron

The Xi’an 200 MeV Proton Application Facility (XiPAF) is a specialized facility designed to simulate space radiation environments. To meet the requirements of space radiation simulation, the proton accelerator must provide a quasi-continuous spill. The facility has achieved this goal by implementing third-order resonance and RF knockout (RF-KO) slow extraction. In this study, the source of the spill ripple at the XiPAF synchrotron was analyzed and a method was developed to calculate the fluctuation ratio of the spill from the spill spectrum. According to the experimental results, the spill quality at XiPAF is mainly affected by the ripple of the magnet power supply. To improve the spill quality, the frequency spectrum of the excitation signal was optimized to suppress the influence of the power supply ripple. We found that the dual-frequency signal, which consists of the two sinusoidal waves corresponding to the extraction and diffusion regions in the third-order resonance, can significantly reduce the influence of the magnet power supply ripple. After adopting the optimized dual-frequency signal, the fluctuation ratio of the spill is reduced from about 0.15 to 0.092 (sample median) at a sampling frequency of 1.24 kHz.

Novel Two-Stream Deep Slow and Nonstationary Fast Feature Extraction for Chemical Process Soft Sensing Application

Novel Two-Stream Deep Slow and Nonstationary Fast Feature Extraction for Chemical Process Soft Sensing Application

Excitation signal optimization for minimizing fluctuations in knock out slow extraction

The synchrotron is a circular particle accelerator used for high energy physics experiments, material and life science, as well as hadron cancer therapy. After acceleration to the desired energies, particle beams are commonly extracted from the synchrotron using the method of resonant slow extraction. The goal is to deliver a steady particle flux—referred to as spill—to experiments and treatment facilities over the course of seconds while slowly emptying the storage ring. Any uncontrolled intensity fluctuations in the spill are detrimental to the efficiency of beam usage, as they lead to detector pileups or detector interlocks, hindering experiments and cancer treatment. Among the most widely used extraction scheme in medical facilities is the Radio Frequency Knock Out (RF-KO) driven resonant slow extraction, where the stored beam is transversely excited with a radio frequency (RF) field and the spill intensity is controlled by the excitation signal strength. This article presents particle dynamics simulations of the RF-KO system with the focus on finding effective mechanism for minimizing the intensity fluctuations while maintaining a good extraction efficiency and other advantages of KO extraction. An improved beam excitation signal which optimizes these main objectives is found, and is rigorously compared experimentally with other commonly applied techniques.

Pulse-stretching out of the CANREB EBIS

The CANadian Rare isotope facility with Electron-Beam ion source (CANREB) at TRIUMF is set to deliver rare isotope beams in high charge states. In the Electron Beam Ion Source (EBIS) ions are charge-bred by collisions with an electron beam of up to 500 mA. A strong magnetic field (up to 6T) maximizes the overlap between ions and electron beam and increases the breeding efficiency. Ion confinement is maintained by a combination of an electrostatic field and the electron beam space-charge potential. Ions are released by lowering the trapping potential with a step function. The system is operated at a pulse repetition frequency up to 100 Hz. Due to the short trap length, this fast extraction scheme produces pulses shorter than 10 µs with high instantaneous rates that can saturate detectors in experiments. Stretching the pulse can be done using a slowly varying voltage function to modify trap electrode potentials instead of a step function. The ideal function produces a pulse with a flat top distribution and can be calculated by knowing the ion energy distribution inside the trap. The latest pulse-stretching results will be discussed including the latest pulse duration up to 1.4 ms that have been produced. The slow extraction scheme has also been used for a measurement of the effective energy distribution of the ions inside the trap.

Environmentally friendly swift and perfect extraction procedures for analysing the phytochemistry and proximate nutritional biochemistry of biomaterial processed from Avicennia marina leaves

Conventional extraction methods have mislaid their best possible performance because of the slow extraction process using demand in inexperienced and innovative technologies. Concerning this view, several eco-friendly novel techniques alienate to develop by us for the entire extraction of nutrients and phytocompounds from plant sources. The specific organic, inorganic chemical compounds have been explored using ultra sonication and GC-MS assisted techniques. The results are evident to facilitate the ultrasonic and GC-MS supported extraction descent that is less solvent consumed, green analytical methods suitable for complete speedy bioactive compounds drawing out. This study has revealed the occurrence of nutrients, phytochemicals, with biological value, and also the GC-MS analysis exposed 20 peaks through 20 individual chemical compounds, and all the compounds are deliberated as energetic medicinal bioactive compounds. Likewise the FE-SEM is used to find out the topographical characteristics of biomaterial and the FTIR analysis.

Transferable adversarial slow feature extraction network for few-shot quality prediction in coal-to-ethylene glycol process

In coal-to-ethylene glycol (CTEG) process, precisely estimating quality variables is crucial for process monitoring, optimization, and control. A significant challenge in this regard is relying on offline laboratory analysis to obtain these variables, which often incurs substantial monetary costs and significant time delays. The resulting few-shot learning scenarios present a hurdle to the efficient development of predictive models. To address this issue, our study introduces the Transferable Adversarial Slow Feature Extraction Network (TASF-Net), an innovative approach designed specifically for few-shot quality prediction in the CTEG process. TASF-Net uniquely integrates the slowness principle with a deep Bayesian framework, effectively capturing the nonlinear and inertial characteristics of the CTEG process. Additionally, the model employs a variable attention mechanism to identify quality-related input variables adaptively at each time step. A key strength of TASF-Net lies in its ability to navigate the complex measurement noise, outliers, and system interference typical in CTEG data. adversarial learning strategy using a min-max game is adopted to improve its robustness and ability to model irregular industrial data accurately and significantly. Furthermore, an incremental refining transfer learning framework is designed to further improve few-shot prediction performance achieved by transferring knowledge from the pre-trained model on the source domain to target domain. The effectiveness and superiority of TASF-Net have been empirically validated using a real-world CTEG dataset. Compared with some state-of-the-art methods, TASF-Net demonstrates exceptional capability in addressing the intricate challenges for few-shot quality prediction in the CTEG process.

Organization of malonamides from the interface to the organic bulk phase

Supramolecular organization of amphiphilic extractant molecules is involved in metal cation selectivity and separation kinetics during solvent extraction. The relationship between extractant associates/aggregates formed in the organic bulk phase and at the liquid–liquid interface is poorly understood even though it affects the extraction mechanism. The nanoscopic structures of the extraction systems N,N,N′,N′-tetrahexylmalonamide (THMA) in toluene and N,N′-dibutyl-N,N′-dimethyl-2-tetradecylmalonamide (DBMA) in n-heptane, used for either Pd(II) or Nd(III) selective extraction from an acidic aqueous phase, were examined. These systems present markedly different affinity for Pd(II) and Nd(III), and extraction kinetics. Extractant organization in the organic bulk phase and at the interface were compared by small-angle X-ray scattering, interfacial tension, and neutron reflectivity. THMA in toluene forms small associates in the organic bulk phase and accumulates in a diffuse layer at the interface, decreasing Pd(II) coordination probability and resulting in slow extraction. DBMA in n-heptane forms large aggregates and a compact, dense interfacial layer, resulting in rapid Pd(II) and Nd(III) extraction. Thus, Pd(II) extraction is driven by interfacial coordination alone, whereas the incorporation of Nd(III) into the core of large aggregates governs Nd(III) extraction in the interfacial layer. These results suggest that the interface should be described as a nanoscale interphase containing a high extractant concentration compared with the organic bulk phase.

Simulation study on the slow extraction for the improvement of the beam shill structure at J-PARC Main Ring

J-PARC Main Ring (MR) delivers a slow extracted 30 GeV proton beam to the Hadron Experimental Facility using third-order resonance. One of the critical properties required for the proton beam is the flatness of the time structure of the extracted beam (spill structure). We performed a simple beam simulation of the MR slow beam extraction to investigate the effect of the current ripples of the main magnet power supplies on the beam spill structure. In addition, we investigated in the simulation the effects of the feedback control system on the betatron tune using fast Q magnets and the transverse RF system to improve the spill structure. The simulation qualitatively reproduced the measured spill structures. Now the attempts to optimize their parameters for better spill structure are ongoing.

Slow Extraction Techniques from Fixed Field Accelerators

Fixed Field Accelerators are a candidate for future hadron cancer therapy facilities as their high repetition rate and large energy acceptance enables novel treatment modalities such as high dose rate FLASH. However, conventional dose delivery mechanisms are still necessary, requiring continuous beam delivery over 1–30s. This work is the first study of slow extraction from a scaling Fixed Field Accelerator, using the LhARA facility for baseline parameters. At a horizontal tune of 10/3, the intrinsic sextupole strength of the nonlinear FFA magnetic field is sufficient to excite the resonance, although extraction is better controlled using an additional excitation sextupole at a tune close to 8/3, with radiofrequency knock-out extraction. Including considerations of issues due to nonlinear fields and limitations required to keep the tune energy-independent, slow extraction from Fixed Field Accelerators is successfully demonstrated.

Differential equation model of the tune ripple effect on beam spill ripple in RFKO slow extraction

Beam uniformity is an important factor that must be considered in slow extraction optimization, and the tune ripple caused by the power supply ripple is an important factor that causes beam uniformity to deteriorate. In this study, based on the beam excitation concept for two regions (extraction and diffusion regions), a differential equation of beam spill under the influence of a mono frequency tune ripple was established. By solving and analysing the differential equation, several conclusions were obtained and verified by simulation.

Optimization of low-energy slow extraction efficiency of XiPAF

Xi’an Proton Application Facility (XiPAF) synchrotron provides 10∼200MeV proton beam for the experimental simulation of the space radiation environment. Due to the space charge effect, the slow extraction of 10 MeV proton beam is a work full of challenges. In a past experiment, the total extraction efficiency was over 65% with 4.5 ∽ 6.5×1010 protons stored before extraction but decreased to 52% with 9×1010 protons stored. In order to study the beam loss caused by a strong space charge effect, based on experimental parameters, the beam loss fractions at different positions of XiPAF synchrotron are obtained through the simulation. According to the beam loss analysis, optimized parameters are found for reference in subsequent experiments. It is also noted that negative beam average momentum spread before extraction is beneficial to the improvement of extraction efficiency.

Investigation of micro spill in RF KO extraction using tailored excitation signals

Radio Frequency Knock Out (RF KO) extraction is used to extract stored particle beams from synchrotrons through transverse excitation, delivering spills of particles for experiments and medical therapy. Minimizing the fluctuations of spill intensity is vital to prevent detector pile-up and interlocks while making most efficient use of the extracted beam. To improve the spill quality, different excitation signals with characteristic frequency spectra are explored. Results of experimental studies at the Heidelberg Ion Beam Therapy Center (HIT) are presented. These demonstrate the possible improvements by tuning multi-band spectra at different harmonics. Particle tracking simulations of the slow extraction process at HIT are used to understand how different excitation signals influence the spill quality.

Feasibility of using crystal channeling for the beam loss mitigation in slow extraction at 8GeV

In the accelerator applications of slow extraction for High Energy Physics (HEP), one of the prime challenges is the mitigation of beam losses, which is becoming increasingly critical with the continuous rise in beam power. A significant breakthrough was achieved earlier at CERN through the successful deployment of proton beam channeling in a crystal at 400 GeV, effectively diverting the beam away from extraction septa and offering new avenues for improving slow extraction efficiency. However, a crucial question remains whether this approach is still effective at lower and medium proton beam energies. In this paper, we present the promising results of the computer simulation studies of the septum shadowing at 8 GeV for the Mu2e project slow extraction at Fermilab. Across the wide range of beam parameters, the beam loss reduction is shown to range between 40 % and factor of three.