rf system
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2021 ◽  
Vol 137 (1) ◽  
Author(s):  
Olivier Brunner ◽  
Erk Jensen ◽  
Ivan Karpov ◽  
Eric Montesinos ◽  
Franck Peauger ◽  
...  

AbstractThe RF system is the centrepiece of any future circular lepton collider. In particular, the system is required to support the high intensity beams needed for pushing the luminosity at the lower energy regimes of future energy-frontier circular lepton colliders (e.g. for operation in the Z peak and at the WW threshold). Capturing, storing the beam and replacing energy losses from synchrotron radiation demand low frequency, low shunt resistance cavities, low number of cells and high RF power per cell. Controlling the beam both transversely and longitudinally requires sophisticated beam control and timing systems. Additional RF systems are used to ensure transverse stability (feedback systems) and to increase the luminosity (crab cavities). Operation at high energies (such as the ZH and $${\mathrm{t}{\overline{\mathrm{t}}}}$$ t t ¯ threshold) requires a very large accelerating voltage, since synchrotron radiation leads to significantly higher energy losses per turn which must be compensated. Since the RF system is to be optimised in size and energy efficiency for varying demands for the different operational modes, the spectrum of R&D challenges covers a wide range of technologies.


2021 ◽  
Vol 11 (23) ◽  
pp. 11126
Author(s):  
Riccardo Casagrande ◽  
Alberto Maistrello ◽  
Marco De Nardi ◽  
Mattia Dan ◽  
Mauro Recchia

The operation of SPIDER (Source for the Production of Ions of Deuterium Extracted from Radio-frequency plasma), full-scale prototype of ITER NBI (Neutral Beam Injector) radio-frequency ion source, pointed out deleterious effects caused by stray Radio-Frequency (RF) currents flowing in the electrical equipment not included in the RF power system. MITICA (Megavolt ITER Injector and Concept Advancement), the full-scale prototype of ITER NBI, is characterized by a similar design in terms of layout of the power supplies and connections to the beam source; thus, it is expected to be subject to the RF stray currents problem. SPIDER RF system is composed of four RF generators, four coaxial lines and four RF loads. Each RF generator is rated for operation at 200 kW in the frequency range 0.9 ÷ 1.1 MHz. The power is delivered to the four loads via as many RF coaxial lines, housed inside a multiconductor transmission line. Each load consists of a capacitive matching network and two plasma drivers in series. Due to the presence of stray connections at the generator and beam-source side (e.g., parasitic capacitances), unwanted RF currents can flow through alternative paths and negatively affect the components not intended for transmission of RF power, the output stages of power supplies and several diagnostics installed in the High-Voltage Deck (HVD) and at the beam source. This paper presents the development of a circuital model used to estimate the RF stray currents in SPIDER electrical system; the understanding of this phenomenon and the development of a model with predictive capabilities is fundamental for the assessment of the performance of both SPIDER and MITICA and, in general, of alternative RF system layouts with respect to the stray currents issue.


2021 ◽  
Vol 21 (2) ◽  
pp. 28-33
Author(s):  
Maroš LAPČÁK ◽  
◽  
Ľuboš OVSENÍK ◽  
Jakub ORAVEC ◽  
Norbert ZDRAVECKÝ

The purpose of this publication is to create and correctly analyse a secondary RF line for a hybrid FSO/RF system. Since we want to ensure almost 100% functionality, the design of a secondary RF line is very important. In our case, we have chosen two types of antennas. First, it was a helical antenna that achieves a high level of efficiency and much smaller dimensions compared to horn antennas. The second type was just a horn antenna. Its advantages are high efficiency, high gain, and narrow width of radiation angle. However, large disadvantages are dimensions and the price of these antennas. However, in both cases, we can say that these antennas are suitable for deployment to our hybrid FSO/RF system.


2021 ◽  
Author(s):  
Shagufta Henna

<div>Hybrid FSO/RF system requires an efficient FSO and RF link switching mechanism to improve the system capacity by realizing the complementary benefits of both the links. The dynamics of network conditions, such as fog, dust, and sand storms compound the link switching problem and control complexity. To address this problem, we initiate the study of deep reinforcement learning (DRL) for link switching of hybrid FSO/RF systems. Specifically, in this work, we focus on actor-critic called Actor/Critic-FSO/RF and Deep-Q network (DQN) called DQN-FSO/RF for FSO/RF link switching under atmospheric turbulences. To formulate the problem, we define the state, action, and reward function of a hybrid FSO/RF system. DQN-FSO/RF frequently updates the deployed policy that interacts with the environment in a hybrid FSO/RF system, resulting in high switching costs. To overcome this, we lift this problem to ensemble consensus-based representation learning for deep reinforcement called DQNEnsemble-FSO/RF. The proposed novel DQNEnsemble-FSO/RF DRL approach uses consensus learned features representations based on an ensemble of asynchronous threads to update the deployed policy. Experimental results corroborate that the proposed DQNEnsemble-FSO/RF’s consensus learned features switching achieves better performance than Actor/Critic-FSO/RF, DQN-FSO/RF, and MyOpic for FSO/RF link switching while keeping the switching cost significantly low.</div>


2021 ◽  
Author(s):  
Shagufta Henna

<div>Hybrid FSO/RF system requires an efficient FSO and RF link switching mechanism to improve the system capacity by realizing the complementary benefits of both the links. The dynamics of network conditions, such as fog, dust, and sand storms compound the link switching problem and control complexity. To address this problem, we initiate the study of deep reinforcement learning (DRL) for link switching of hybrid FSO/RF systems. Specifically, in this work, we focus on actor-critic called Actor/Critic-FSO/RF and Deep-Q network (DQN) called DQN-FSO/RF for FSO/RF link switching under atmospheric turbulences. To formulate the problem, we define the state, action, and reward function of a hybrid FSO/RF system. DQN-FSO/RF frequently updates the deployed policy that interacts with the environment in a hybrid FSO/RF system, resulting in high switching costs. To overcome this, we lift this problem to ensemble consensus-based representation learning for deep reinforcement called DQNEnsemble-FSO/RF. The proposed novel DQNEnsemble-FSO/RF DRL approach uses consensus learned features representations based on an ensemble of asynchronous threads to update the deployed policy. Experimental results corroborate that the proposed DQNEnsemble-FSO/RF’s consensus learned features switching achieves better performance than Actor/Critic-FSO/RF, DQN-FSO/RF, and MyOpic for FSO/RF link switching while keeping the switching cost significantly low.</div>


Author(s):  
Jingru Zhang ◽  
Cai Meng ◽  
Dazhang Li ◽  
Dou Wang ◽  
Guoxi Pei ◽  
...  

The CEPC includes a main ring and an injector. The injector consists of a booster and a linac. In order to meet the requirements of the booster, the baseline design of the linac is a 10 GeV electron and positron linac. Two alternative linac designs have also been introduced in this paper. For the linac baseline design, one-bunch-per-pulse is adopted. A 1.1 GeV damping ring is used to reduce the transverse emittance of positron beam. The main RF system of the linac adopts normal conducting S-band structure. Some key technologies of linac are development. The S-band structure and pulse compressor have been researched and studied. In the damping ring, two cavities used to provide 2 MV voltage. The preliminary cavity design has finished.


2021 ◽  
Vol 168 ◽  
pp. 112396
Author(s):  
Cristina de la Morena ◽  
David Regidor ◽  
Daniel Iriarte ◽  
Francisco Sierra ◽  
Eduardo Ugarte ◽  
...  

2021 ◽  
Vol 167 ◽  
pp. 112337
Author(s):  
Alberto Maistrello ◽  
Mauro Recchia ◽  
Andrea Zamengo ◽  
Marco Bernardi ◽  
Giuseppe Chitarin ◽  
...  
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