The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development by international collaborations hosted by CERN. This document provides an overview of the design, technology, and implementation aspects of the CLIC accelerator. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, for a site length ranging between 11 km and 50 km. CLIC uses a Two-Beam acceleration scheme, in which normal-conducting high-gradient 12 GHz accelerating structures are powered via a high-current Drive Beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments, and system tests have resulted insignificant progress in recent years. Moreover, this has led to an increased energy efficiency and reduced power consumption of around 170 MW for the 380 GeV stage, together with a reduced cost estimate of approximately 6 billion CHF. The construction of the first CLIC energy stage could start as early as 2026 and first beams would be available by 2035, marking the beginning of a physics programme spanning 25-30 years and providing excellent sensitivity to Beyond Standard Model physics, through direct searches and via a broad set of precision measurements of Standard Model processes, particularly in the Higgs and top-quark sectors.

The Compact Linear Collider (CLIC) – Project Implementation Plan

This paper describes the design and implementation of a three-phase resonant converter with low ripple and high control accuracy. Based on a three-phase LCC-type resonant converter-which has advantages of low ripple, highefficiency, and high-power density compared with a single-phase converter-a high-voltage power supply with low ripple (<;0.1%) was designed. In addition to the general merits of an LCC-type resonant converter operating at continuous conduction mode- including soft switching, low conduction loss, and current source characteristics-the proposed scheme uses only one phase under a light-load condition by having different leg designs of the gate drive circuit and snubber parameters. This allows the design to overcome the operational constraints of the general LCC-type resonant converter. The distinctive design of the three-phase converter structure provides high efficiency and low ripple not only during rated operation, but also under light-load conditions. In order to analyze the high performance of the proposed scheme from no load to rated load, a PSPICE simulation was carried out. Comparison results with a conventional LCC-type resonant converter based on a single-phase structure are analyzed from the viewpoints of output ripple, losses, and operable load range. Using the proposed converter, a 20-kV, 20-kW high-voltage dc power supply design and implementation was presented with a superior gate drive circuit. Finally, the superiority of the proposed converter was verified through a simulation and experimental results. It was experimentally confirmed that the developed power supply achieves high performance in terms of efficiency (98%), operable load range (0.5-20 kV), and low ripple (0.05%), with a high power density.

Low-Ripple and High-Precision High-Voltage DC Power Supply for Pulsed Power Applications

In this paper, an analytical method to model the thermal resistance of windings made either of solid or litz wire is presented and validated by measurements. In addition, an extended numerical approach for litz wire windings, which also considers the twist pitch, is shown. With the presented model, it is possible to describe the thermal resistance of arbitrary wire arrangements. This approach can be used in straightforward thermal designs of magnetic devices, or it can be integrated in optimization procedures to improve the thermal designs of magnetic components. The analytical models are verified by measurements with nonpotted and epoxy-potted solid wire test setups and test setups for litz wire, which all show a good matching between the calculated and measured values. Besides the models for the thermal resistance between the winding layers, a method to simplify the thermal network of multilayer windings is presented. Finally, a thermal equivalent circuit of a test transformer has been calculated, which shows a good match between the measured and the predicted temperature distribution.

General Analytical Model for the Thermal Resistance of Windings Made of Solid or Litz Wire

In this paper, a unified equivalent circuit model which can simplify the design and analysis of a family of high-voltage (HV) generation architectures based on the series–parallel ( LCC ) resonant converter is proposed. First, four HV generation architectures are reviewed in terms of the modularization level of HV transformers and rectifiers. Next, the steady-state, unified equivalent resistor and capacitor ( RC ) model that can be easily embedded into the resonant tank to replace the complex HV transformers and rectifiers is derived. The generic model can be applied to the HV generators with different architectures, different voltage multiplier topologies, stage, and polarities number. Further analysis of the power factor of the resonant tank, the voltage gain of HV generators, and electrical stresses of power components is achieved with the derived equivalent circuit model. The analysis reveals the inherent circuit properties among HV generators with different configurations. Subsequently, a comprehensive design methodology considering the power factor, conduction angle, and quality factor is presented, which leads to low electrical stresses on the components and high efficiency. Furthermore, the parameter selection constraint based on the power factor, conduction angle, and quality factor is derived, which can ensure the effective design outputs. Finally, the proposed unified equivalent model and comprehensive design methodology are validated by the experimental results of a 250 V input, 20 kV output 500 W HV generator hardware prototype with distributed transformers and voltage multipliers.

Unified Equivalent Steady-State Circuit Model and Comprehensive Design of the LCC Resonant Converter for HV Generation Architectures

A design and optimization procedure for high-voltage pulse transformers is presented. The procedure is enhanced by the integration of core loss measurements under pulsed excitation, by electrical peak field calculations and by checking of the isolation distances, which are compared to scaled high-voltage breakdown data. The procedure is applied with specifications of the compact linear collider, and the sensitivity of system parameters such as the number of primary turns, core material, transformer oil, and high-voltage cable length is investigated by comparing their Pareto fronts. With amorphous core material, the highest efficiency is achieved. Replacing mineral oil by natural ester results in an efficiency reduction of 0.5%, and an increase in HV cable length from 1.5 to 5 m reduces the efficiency by 0.6%. Finally, the optimized transformer’s pulse shape is investigated over the entire load range.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/Design_and_Optimization_Procedure_for_High_Voltage_Pulse_Power_Transformers_01.pdf

Design and Optimization Procedure for High-Voltage Pulse Power Transformers

In this paper, a procedure for optimal transformer design with a variable set of constraints for pulse transformers with a pulse range of 3-140 μs is presented. During the optimization procedure, the pulse shape is analyzed in the time domain, ensuring that the pulse constraints, such as rise time and overshoot are met. For accurate prediction of the pulse shape, analytical approaches are proposed to estimate the distributed capacitance and leakage inductance of the transformer. The analytical approach is verified by 2-D-FEM simulations and measurements. The optimization procedure considers pulse, core, winding, demagnetization losses, and losses of the primary switches. First, the procedure is applied to an existing pulse transformer with specifications for SwissFEL. An improvement of 16.6% in conversion efficiency is achieved in comparison with the existing design. In a second step, the procedure is applied to specifications of the compact linear collider, which demands high conversion efficiency. The resulting optimal transformer consists of three cores with five primary turns and requires a tank volume of 0.915 m3. In an optimal configuration, an overall conversion efficiency of 97.7% is achieved for the considered system including pulse losses.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/Transformer.pdf

Optimal Transformer Design for Ultraprecise Solid State Modulators

In this paper, the design procedure of a 14.4 kV output voltage, 100 kHz transformer with an isolation voltage of 115 kV using Litz wire is presented. All design models, including a generalized magnetic model for the leakage and the loss calculations as well as an electrical model for the parasitic capacitance estimation for the transformer are derived and proven by measurements. For designing the insulation, a comprehensive design method based on an analytical maximum electrical field evaluation and an electrical field conform design is used. The resulting design is verified by long and short term partial discharge measurements on a prototype transformer.

Design procedure of a 14.4 kV, 100 kHz transformer with a high isolation voltage (115 kV)

In this paper, a general lumped parameter bearing current model is presented. The lumped parameters are derived from the analytical descriptions of the bearing current paths and the numerical field simulations based on the finite element method. The model considers frequency dependence. The resulting model delivers the common mode current and the circulating bearing current is determined by modeling the magnetic coupling between the common mode current path and the circulating bearing current path. The derived circuit can be applied to AC machines and is verified by measurements of a permanent magnet excited synchronous machine, which is supplied by an off-the-shelf motor drive inverter.

An Improved Model for Circulating Bearing Currents in Inverter-Fed AC Machines

Long pulse modulator systems like the electron-positron compact linear collider (CLIC) with a pulse length of 140μs require a bouncer for voltage drop compensation. In this paper, an active bouncer system, consisting of four bouncer modules, in series to the main capacitor bank, is investigated. The system's transfer function including the matrix pulse transformer is analysed and the output voltage ripple induced by the bouncer system is designed to be smaller than 5 ppm due to demanding repeatability requirement of CLIC. Based on a loss analysis is conducted resulting in a total bouncer system volume of 52dm3 and a reduction in the global efficiency (grid to klystron) of the modulator system of only 0.45%.

https://www.hpe.ee.ethz.ch/uploads/tx_ethpublications/06627653.pdf

Sebastian Blume

Papers

Optimal Transformer Design for Ultraprecise Solid State Modulators

Design and Optimization Procedure for High-Voltage Pulse Power Transformers

Design procedure of a 14.4 kV, 100 kHz transformer with a high isolation voltage (115 kV)

An Improved Model for Circulating Bearing Currents in Inverter-Fed AC Machines

Design procedure of an active bouncer for an ultra precise long pulse solid state modulator