Machine-learning approach for operating electron beam at KEK $e^-/e^+$
injector Linac
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In current accelerators, numerous parameters and monitored values are to be adjusted and evaluated, respectively. In addition, fine adjustments are required to achieve the target performance. Therefore, the conventional accelerator-operation method, in which experts manually adjust the parameters, is reaching its limits. We are currently investigating the use of machine learning for accelerator tuning as an alternative to expert-based tuning. In recent years, machine-learning algorithms have progressed significantly in terms of speed, sensitivity, and application range. In addition, various libraries are available from different vendors and are relatively easy to use. Herein, we report the results of electron-beam tuning experiments using Bayesian optimization, a tree-structured Parzen estimator, and a covariance matrix-adaptation evolution strategy. Beam-tuning experiments are performed at the KEK $e^-$/$e^+$ injector Linac to maximize the electron-beam charge and reduce the energy-dispersion function. In each case, the performance achieved is comparable to that of a skilled expert.This paper presents the results of an experimental study of the effect of injector's geometry on the performance of an internally mixed, air-assisted, liquid injector. In this type of injector a small amount of air is injected into a liquid stream within the injector. The interaction of the liquid with the atomizing air inside the injector induces atomization. The results presented in this paper show that the size of the droplets produced by the investigated injector decreases with a decrease in the air injection area. This is due to the increase in atomizing air injection velocity that accompanies the decrease in the air injection area, which improves atomization. This study also shows that the droplet sizes decrease with an increase in the injector's length, which is attributed to the increase in total interactive force.
Secondary air injection
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The Chinese ADS (C-ADS) project is proposed to build a 1000MW Accelerator Driven sub-critical System before 2032. The accelerator will be operating on CW mode with 10mA average current and the final energy is 1.5GeV. The whole linac are composed of two major sections: the Injector section and the main linac section. There are two different schemes for the Injector section. Injector I is basing on 325MHz RFQ and superconducting spoke cavities and Injector II is basing on 162.5MHz RFQ and superconducting HWR cavities. The main linac design will be different for different Injector choice. If Injector II scheme is adopted, the main linac bunch current will be doubled. In this paper the main linac design basing on Injector II scheme is studied. The design principles and considerations are introduced; the base line design is presented.
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The China ADS (C-ADS) project proposes to build a 1000 MW Accelerator Driven sub-critical System around 2032. The accelerator will work in CW mode with 10 mA in beam current and 1.5 GeV in final beam energy. The linac is composed of two major sections: the injector section and the main linac section. There are two different schemes for the injector section. The Injector- I scheme is based on a 325 MHz RFQ and superconducting spoke cavities of the same RF frequency and the Injector- II scheme is based on a 162.5 MHz RFQ and superconducting HWR cavities of the same frequency. The main linac design will be different for different injector choices. The two different designs for the main linac have been studied according to the beam characteristics from the different injector schemes.
Beam energy
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A 100 MeV "turn-key" injector electron linac for the Swiss Light Source (SLS) is under construction at ACCEL Instruments. The system will be installed, commissioned and handed over to the SLS in late 1999, after a 18 month design and production period. This paper presents the special needs of an injector for a third generation synchrotron light source and the two specific modes of operation for this linac. The specification of the system and a description of the design results as well as the planned technical realisation are given.
Realisation
Synchrotron light source
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The conception of the construction of the fuel spray injector for a turbo engine of a small unmanned aircraft is proposed in this paper. The work out of the injector model made in rapid prototyping method is shortly presented. Methods of the injector investigation were described. The results of the injector flow parameters and macrostructure parameters investigation were presented and discussed. They were used to formulate the main conclusion connected with the relation between the injector construction, the injector feeding parameters and spray parameters.
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Formulas for a transversely-matched beam are derived in terms of the r-matrix representation of accelerating and focusing elements in the first period of a linac structure. The formulas predict beam parameters close to the values actually used in tuning the LAMPF 805 MHz linac, and give reasonable-looking results in the other cases for which they have been applied.
Representation
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The TESLA positron injector linac with a L-band TW normal conducting structure has been studied, which offers both higher shunt impedance and larger aperture. Main parameters of this injector linac have been designed by systematical beam modeling, and a satisfactory positron beam transmission and the beam performance at the output of the injector linac have been obtained.
Aperture (computer memory)
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Detailed beam dynamics calculations of the LANSCE Linac have been performed using multi-particle simulation codes. The LANSCE accelerator produces both H{sup +} and H{sup {minus}} beams and is comprised of Cockcroft-Walton injectors, a 100 MeV drift-tube linac and an 800 MeV side-coupled linac. Several improvements to the simulations of H{sup +} and H{sup {minus}} beams have recently been made. These include the use of more accurate input distributions and a better estimate of beam neutralization in the low-energy beam transport. Better estimates of the accelerating fields in the drift-tube linac have also been determined through measurements and modeling. With these improvements better agreement has been achieved between the predictions and measurements of RMS beam parameters and beam losses for both beams. The details of the simulations along with predictions are presented in comparison with measurements for both H{sup +} and H{sup {minus}} beams.
Drift tube
Dynamics
Beam energy
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The ejector design is defined by the operational conditions and by the system/application the ejector will be used for. By changing the geometrical design of the ejector, the characteristics of the ejector will change and the operational area where the ejector is more efficient will also change. Different system designs will have different requirements and will require/benefit most from ejector designs that are adapted to the unique characteristics of each system type. The present paper is briefly describing an investigation of typical ejector systems along with the characteristics of an ejector dedicated for these systems. Experimental studies were conducted by SINTEF with a multi ejector and different geometrical ejector designs where investigated. Almost 1000 experiments have been performed mapping the various ejectors at different operational conditions.
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Studies of H−‐ion beam injector for a linear accelerator operating at a frequency of 433 MHz were carried out. The results are given. The injector is a system consisting of a Dudnikov’s source, bending magnet, and electrostatic preaccelerator, accelerating beam up to 60–100 keV.
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