Cockcroft-Walton Research Articles

Comparative Analysis of an 8 – Stage Cockcroft Walton Voltage Multiplier and A Dickson Voltage Multiplier in The Context of Radio Frequency Energy Harvesting

Purpose: This study seeks to enhance voltage multipliers for Radio Frequency (RF) energy harvesting, with an emphasis on increasing the efficiency of harvested energy. This improvement is vital for sustainable energy applications and reducing environmental pollution caused by fossil fuels. Theoretical reference: RF energy harvesting technology is gaining recognition as a viable sustainable method for capturing ambient energy, with earlier research primarily focused on antenna and circuit design. Nonetheless, the effectiveness of energy harvesting is still constrained by inadequate power output. This study expands on prior research by directly comparing two commonly utilized voltage multipliers, the Cockcroft Walton and Dickson multipliers, in the context of RF energy harvesting. Method: The Cockcroft Walton and Dickson voltage multipliers were optimally designed using Multisim and their performance was analysed using MATLAB. The comparison was conducted at an input voltage of 1V within two frequency ranges: 85 MHz – 110 MHz (FM band) and 1.8 GHz – 3.0 GHz (4G band). Output voltages for both multipliers were recorded and compared across these frequency bands. Results and Conclusion: At an input voltage of 1V within the FM band (85 MHz – 110 MHz), the Dickson voltage multiplier outperformed the Cockcroft Walton multiplier, delivering an output voltage of 11.1V compared to 6.6V. However, in the 4G band (1.8 GHz – 3.0 GHz), the Cockcroft Walton multiplier was more effective, providing a maximum output voltage of 5.2V against Dickson's 4.1V. The study concludes that the Dickson multiplier is more suitable for harvesting RF energy from the FM band, while the Cockcroft Walton multiplier is better for 4G band energy harvesting. Implications of research: The findings suggest that different RF energy harvesting applications may benefit from distinct voltage multipliers, depending on the frequency band in question. This could guide the design of more efficient RF energy harvesting circuits in future technologies aimed at sustainable energy solutions. Originality/value: This study offers a direct comparison of two voltage multipliers under different RF frequency conditions, providing valuable insights into optimizing energy harvesting technologies for green energy applications. The results help advance the understanding of efficient circuit design for specific RF frequency bands, contributing to the development of more effective energy harvesting systems.

Fluence measurement of monoenergetic neutrons from D(d,n) and T(d,n) reactions at the KRISS

A Cockcroft–Walton accelerator from High Voltage Engineering Europa BV was installed at the Korea Research Institute of Standards and Science in June 2022 to generate monoenergetic neutron fields. In this study, the fluences of monoenergetic neutron fields with energy peaks at 2.5, 2.8, and 3.2 MeV from the D(d,n) reaction and at 14.8 MeV from the T(d,n) reaction were measured. To measure neutron fluence, Bonner spheres with diameters of 17.78, 20.32, and 25.40 cm were placed at a distance of 1.50 m from the target. Additionally, a small size long counter was used separately as a neutron reference detector to monitor the stability of neutron production rate. For a deuteron beam current of 1 μA, the neutron fluences of monoenergetic neutron fields with energy peak at 2.5, 2.8, 3.2, and 14.8 MeV were determined to be 0.71 ± 0.03, 1.10 ± 0.04, 13.9 ± 0.5, and 258.0 ± 8.1 cm−2s−1μA−1, respectively.

Review of Cockcroft-Walton High Voltage Low Current DC Power Supplies

High-voltage power supplies are key for developing particle accelerators, neutron generators, x-ray systems, ion implantation, etc. This paper reviews various developed voltage low current power supplies based on Cockcroft-Walton voltage multiplier circuits for accelerator-based neutron sources and other industrial and medical applications. The paper presents a detailed review of the topology of the power supply used for the high voltage generation, the key design parameters, key active and passive components used in the High Voltage (HV) system, key experimental results, protection and measurement circuit used in the power supply and about the system performance. The improvement that occurred in the size and performance of the power supplies due to the development in the technology of the magnetic components, semiconductors and energy storage devices in successive years is apparent in the discussion. Finally challenges and possible solutions for the compact design and system performance are concluded for the development of high voltage low current power supplies.

Measurement of the neutron energy response curve of 4H-SiC detector based fission target detection system at the CSNS Back-n white neutron source

The fission target detection system, which is based on U-235(or U-238)fission target and large area 4H-SiC detector, has been developed for pulsed neutron detection. However, calibration of its neutron energy response curve is challenging due to its very low detection efficiency to fast neutrons. In the past, the calibration of the neutron sensitivity for the fission target detection system was limited to using ∼ 14 MeV neutrons generated by the Cockcroft-Walton accelerator. To obtain the response function for the complete range of neutron energies, extrapolation based on neutron fission cross sections was required. In this paper, we present the calibration of its energy response at the China Spallation Neutron Source (CSNS) Back-n beam line using the time of flight method, both with double-bunch and single-bunch mode in end-station 1(with a flight path of ∼ 55 m). The SiC detector with a thin sensitive thickness of 30 μm has lower scattering background than the traditional Si-PIN detector . As a result, the energy response curve of the fission target detection system above 0.26 MeV has been successfully acquired. The spectrum of the double-bunch mode was unfolded using the Bayesian algorithm, and the results indicate that, under conditions of sufficient counts, this method can yield results similar to those obtained from the single-bunch mode. The issue of pulse height defect of SiC detector to fission fragments is discussed. This experiment confirms that our detection system of SiC+fission target has a strong signal-to-noise ratio and anti-interference capability. At the same time, it demonstrates that this device has its own advantages in measuring the energy response of low sensitivity detectors.

Measurement of Cumulative fission product yields on 235U induced by 2.8 MeV neutrons

Off-line gamma-ray spectrometry was used to accurately measure the Cumulative fission product yields (CFPYs) of fission products in the 235U (n, f) reaction induced by 2.8 MeV neutrons. The 2.8 MeV quasi-monoenergetic neutron beam was produced by the CPNG-600 Cockcroft Walton accelerator at the China Institute of Atomic Energy （CIAE）and the gamma spectra were measured by the HPGe γ-ray Spectrometer. After fully considering and revising the sources of uncertainty, high-precision CFPYs of 4 fission products were obtained. This study has important applications in reactor design and operation and is conducive to the establishment of an evaluated nuclear database.

Design, manufacturing, and testing of 0.35/25kV, 20kHz transformers for particle accelerators.

A high voltage, high frequency transformer unit has been designed and built for powering the Cockcroft-Walton voltage multiplier to be used as part of a particle accelerator power supply at the Institute For Plasma Research, India, for the nuclear fusion research facility. A novel combination of high voltage (25kV), high frequency (20kHz), and high power (70kVA) specifications makes its design distinctive and more challenging. The complete unit is composed of two 0.350/25kV amorphous core transformers connected in center-tap configuration and immersed in an oil-filled tank. To facilitate an iterative design procedure, a spreadsheet method was utilized. The design involved a methodical approach for the core and winding selection, followed by the magnetic analysis and high voltage insulation layout through the finite element method. All the magnetic, electrical, and thermal parameters have been evaluated in detail, assuring a continuous stable operation having an efficiency of greater than 95%. Finally, the transformers were made, and preliminary experiments, including turns ratio, short-circuit, and dielectric tests, were carried out to verify the accuracy of the proposed design. The unit was also field tested under actual load conditions, and the test results were presented and corroborated with the design calculations.

In-air experimental achievement of high-voltage DC power supply to be installed in a tandem electrostatic accelerator system for boron neutron capture therapy application.

The boron neutron capture therapy (BNCT) system developed by the Korea Institute of Radiological and Medical Sciences is a compact neutron source that can be installed at medical institutes. The target energy was accelerated to a maximum of 2.4 MeV-20 mA by introducing a gas stripping device that converts negative hydrogen ions into positive ions. By using the tandem-type accelerator in this way, a high-voltage DC power supply was designed with 1.2 MV-45 mA as the maximum capability. The design was improved to reduce the number of stages of a Cockcroft-Walton voltage multiplier. Hence, the ripple risk of the DC flat top resulting from unwanted stray capacitance was lowered. The overall height and volume of the Cockcroft-Walton voltage multiplier were reduced to less than half those of the existing design method, making miniaturization possible. After such advanced design and manufacturing, performance tests were performed at 750 kV-45 mA under 23 stages of the Cockcroft-Walton voltage multiplier, which is the highest level that can perform at its maximum under in-air conditions. It demonstrated stable performance under in-air conditions without breakdown for 2h, even at 620 kV-35 mA. To reach the final target of 1.2 MV-45 mA, the groundwork is laid for achieving experimental performance while satisfying the optimal requirements in SF6 gas.

Development of a desktop mask charger

Polypropylene mesh, integrated in N95 respirators and surgical masks that are widely used in the current crisis of COVID-19, filters aerosols via electrostatics in addition to the physical block. However, any contact to water such as storage under high humidity, exposure to exhaling breath, and washing in water removes its charges and thus compromises its filtering efficiency. We developed a desk top device based on a Cockcroft-Walton's voltage multiplier that can restore the electrostatic charge of surgical masks within 1 min and recover the filtering efficiency of the polypropylene mesh from 87% to 97%. The device is easy to operate and safe, thus may be applied for the reuse of surgical masks towards reducing the plastic wastes.

A 1-MHz GaN-Based $LCLC$ Resonant Step-Up Converter With Air-Core Transformer for Satellite Electric Propulsion Application

A gallium nitride (GaN)-based resonant step-up converter is proposed for the application in the satellite electric propulsion (EP) system. This converter consists of a full-bridge inverter, a resonant tank, and a multistage Cockcroft–Walton voltage multiplier to provide a high voltage gain. Additionally, the air-core transformer is introduced due to the megahertz switching frequency allowed by the GaN device. Thus, the limited magnetizing inductance of transformer and the remarkable junction capacitance of diode have to be carefully considered in the resonant tank design, especially after considering that this converter normally operates at the light load in the EP system. In this work, the fourth-order <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ LCLC$</tex-math></inline-formula> resonant converter is investigated. The recommended parameter selection for the fourth-order resonant tank is also provided. A 1.2-MHz, 23-V/2.5-kV, and 6-W prototype is demonstrated. It achieves a low harmonics distortion and a low power loss with the zero voltage switching.

A Mini-Marx Generator Powered by a Cockcroft–Walton Voltage Multiplier

A Marx generator generates a high-voltage (HV) pulse by charging two or more capacitors in parallel and then suddenly connecting them in series. In principles, a comparatively lower voltage dc power supply has to be used for the charging to achieve the desired HV. However, a moderate dc HV power supply is still quite expensive and bulky but not in full-time usage. In this work, a mini-Marx generator powered by a Cockcroft–Walton (CW) voltage multiplier has been proposed to form a more efficient, compact, but affordable configuration of pulsed HV power sources. For generating an HV in a range of 20–150 kV with the mini-Marx generator consisting of eight stages, a CW multiplier operating up to 3–20 kV is required. Numerical simulations using PSpice have been performed for validating the concept. For demonstration, a prototype of the 22-stage CW-powered four-stage mini-Marx has been built and tested with an ac voltage of 110 V at 60 Hz. In the experiment, the CW generator can reach 3.6 kV to power the mini-Marx, delivering an HV of 12.7 kV, consistent with the PSpice modeling. With an ac household voltage of 220 V at 60 Hz, a dc voltage of 5.2 kV can be obtained from the CW to charge an eight-stage mini-Marx generator, achieving an output voltage of 33 kV to drive a field emission-based X-ray source. The proposed CW powered mini-Marx generator is general and can be used as a compact pulsed voltage supply for some portable devices.

Development of High Voltage DC Power Supply from Tesla Coil Using Hybrid Energy Sources

Background: High Voltage Direct Current (HVDC) is a well-proven technology used to transmit electricity over long distances by overhead transmission lines or submarine cables. It is also used to interconnect separate power systems, where traditional Alternating Current (AC) connections cannot be used. Objective: In this paper, an HVDC supply has been proposed with the Tesla coil using hybrid energy sources such as solar panels, batteries, and AC main supply with an AC-DC converter. Method: DC voltage is obtained from various hybrid sources and is supplied to the input of the Cockcroft-Walton (C-W) voltage multiplier circuit through DC/AC inversion. Result: The produced HVDC is provided to the Tesla coil to obtain a stable HVDC output. Fractional Order PID (FOPID) controller is used in the system for control purposes to stabilize the output voltage due to load variations. The model was designed in Matlab / Simulink environment. The simulation results show that the proposed design successfully achieved a stable 15 kV HVDC. Conclusion: The advantage of the proposed system is the availability of variable output voltage as per load requirement compared to the fixed limited output voltage generated by conventional HVDC systems.

Cockcroft–Walton Generator: An Effective Voltage Multiplier for Power Supplies of Square Pulses Driving DBD Plasmas

This report gives prominence to the importance of the traditional Cockcroft–Walton voltage multiplier to the design of pulsed power supplies for dielectric barrier discharge (DBD) applications. Following an inventive concept, a simple Cockcroft–Walton generator is combined with a MOSFET-based switch (in either “push” or “pull” mode). Thus, the to-be-chopped stabilized dc high voltage is produced by a compact, transformer-less, modular unit, having high flexibility in terms of engineering. This approach leads to well-defined, square, high-voltage pulses of variable amplitude, frequency, and duty cycle. Design, implementation, and proof test of such a prototype are here demonstrated. The prototype yields square pulses as high as 10 kV (plateau value), as narrow as 350 ns (variable pulsewidth up to millisecond, depending on the frequency), rising or falling time close to 20 ns, pulse repetition rates up to 4 kHz, and output mean power up to 150 W. The functionality of the system is demonstrated by driving coaxial, ambient air DBDs of variable lengths, while principal electrical and optical parameters are recorded. Peak power values higher than 70 kW are measured on the DBD side, while the voltage multiplier power efficiency factor remains close to 95%.

36-5-2] 24V 전원 기반의 60kV 고전압 커패시터 충전기의 설계

In this paper, a 60kV high voltage capacitor charger(HVCC) based on a 24V battery was described. The HVCC should satisfy not only the extreme voltage gain for 60kV output based on 24V input but also compact size and lightweight for portability despite the high current burden due to the low input voltage. In addition, there are other considerations such as the voltage stress of each component and insulation. Considering these matters, the HVCC was designed based on the parallel loaded resonant converter and symmetrical Cockcroft-Walton voltage multiplier(CWVM). The parallel load resonant converter enables high-frequency operation by reducing switching losses through the zero voltage switching turn-on and snubber capacitor for soft turn-off. With proper design followed by analysis, the HVCC is capable of ZVS turn-on from the start of charging to charging the target voltage. Two symmetrical CWVMs are connected in parallel to the center-tapped transformer to alleviate voltage stress and insulation design difficulty of high-voltage devices. Through PSpice simulation, it was verified that the HVCC satisfies the target specification and the soft switching operation, and the electric field analysis was performed.

Measurement of the [formula omitted] reaction cross section induced by 14.8 MeV neutrons

The measurement of the 59Co(n,2n)58Co reaction cross section with the neutron energy of 14.8 MeV has been performed by the activation method and relative measurement principle. The 300 kV Cockcroft Walton Accelerator of China Institute of Atomic Energy was used to produce quasi monoenergetic neutron beams by the T(D, n)4He reaction. Two thin 27Al and 93Nb foils were attached to the 59Co target and performed as monitors. After the irradiation, the HPGe detector and the GammaVision software were used to measure the activity of the irradiated samples and record the counts of γ-rays, respectively. Finally, some relevant physical quantities were corrected after comparing the results with experimental data in the EXFOR database and evaluated data in the ENDF database.

Forward–Flyback Converter With Cockcroft–Walton Voltage Multiplier in DCM: Steady-State Analysis Considering the Parasitic Capacitances to Achieve the Optimal Valley-Switching Operation With 95.11% Efficiency at 3 kV/1.5 W

Nowadays, electrohydrodynamic (EHD) cooling systems are considered a good alternative to rotary fans and heatsinks from industrial electronic applications due to their robustness, high performance, and low weight. The EHD load tested along this article demands high voltage (3 kV) and very low current (500 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> ) to produce the corona discharge and the airflow. The forward–flyback converter with Cockcroft–Walton voltage multiplier (FFCWVM) is proposed in this article as a suitable topology to supply EHD loads. The parasitic capacitances are considered throughout the steady-state analysis, leading to new operating stages and allowing for a very accurate mathematical modeling of the main resonant intervals. Consequently, the impact of a slow voltage transition in the functioning of the circuit is analyzed and the optimal valley-switching operation is calculated analytically. Finally, the theoretical analysis is validated by means of simulations and experimental results, achieving a very high efficiency (95.11%) for such low output power (1.5 W).

A High Gain AC-DC Rectifier Based on Current-Fed Cockcroft-Walton Voltage Multiplier for Motor Drive Applications

This paper proposes a novel high-gain AC-DC converter based on the Cockcroft-Walton (CW) voltage multiplier which can be utilized in motor drive systems with low input voltage. In this topology, use of the voltage multiplier and boost circuit results in the increment of converter gain which has a significant impact on the cost and efficiency of the system. Moreover, in this converter, the AC voltage is directly changed to DC voltage using the switching method in high frequency and, as well, the power factor is corrected. Besides, this high-frequency converter contributes to the reduction of output ripple. On the other hand, cost efficiency, the low voltage stress on capacitors and diodes, compactness, and the high voltage ratio, are achieved from the Cockcroft-Walton circuit. Furthermore, the hysteresis method is presented for converter switching to correct the power factor. The converter is simulated in MATLAB software to demonstrate the effectiveness of the suggested method. Lastly, a laboratory prototype of the suggested converter is built, several tests are done in order to verify the theoretical analysis, and comprehensive comparison with the state-of-the-art converter is done.

Enhanced aerosol deposition by a low‐cost compact nanosecond‐pulsed plasma system

AbstractNanosecond (ns)‐pulsed air plasmas are promising for environmental and biomedical applications. This paper presented a low‐cost ns‐pulsed plasma system that consists of a two‐stage Cockcroft–Walton voltage multiplier, a spark gap gas switch, and a plasma reactor. This ns power supply generated a uniform air plasma with a volume of 25 × 25 × 2 cm and a maximum ion wind of 0.8 m/s. The ion wind transported aerosols through plasma volume. Aerosols were charged and deposited on the grounded mesh electrode. The direct interactions between reactive ns plasma and deposited aerosols can promote the development of plasma applications.

Measurement of the 124Xe (n,2n) reaction cross section induced by 14.8 MeV neutron

The measurement of the 124Xe(n, 2n)123Xe reaction cross section at 14.8 MeV neutron has been performed by the activation method. Quasi monoenergetic neutron beams were produced at the Cockcroft Walton Accelerator of China Institute of Atomic Energy, by the T(d, n)4He reaction. A cell made of polymethyl methacrylate (PMMA) was used as the container of 124Xe (99.95% abundance) gas, and the mass of 124Xe in cell was determined by weighing method. Two high-purity thin 93Nb foils were attached to the cell and performed as monitors of the neutron flux determination by 93Nb(n, 2n)92mNb reaction. After the irradiation, the activities of 123Xe and 92mNb were measured by off-line gamma-ray spectrometric technique using a pre-calibrated HPGe detector. As a result, the cross section has been deduced at 14.8 MeV, and the result was compared with the literature data and evaluations.

PERFORMANCE EVALUATION OF VOLTAGE RECTIFIERS FOR ENERGY HARVESTING APPLICATIONS

Voltage multipliers are used to convert the low AC voltage output of energy harvesters into relatively high DC voltage for portable devices and wireless sensor nodes (WSNs) applications. DC voltage conversion is required to operate an electronic device or recharge battery. In order, to convert the low AC voltage output of the energy harvester into relatively high DC voltage, a voltage multiplier circuit need to be integrated with the energy harvester. In this study, a Prototype-1 (two-stages) and Prototype-2 (three-stage) Dickson voltage multipliers and Prototype-3 (seven-stage) Cockcroft-Walton voltage multiplier circuits are developed. The device is capable of converting a low voltage of 50 mV into 350 mV. The research focuses on the development and characterization of Prototype-1, Prototype-2 and Prototype-3 circuits. Results indicate that the determination of load resistance is important for better output power. The maximum power of 11.97 μW was obtained by prototype-3 elucidating better power compared to prototype-1 and prototype-2 and the power was obtained at an optimum load of 560 kΩ. Furthermore, a rectenna tested at different distances from the source, revealed that a prototype-2 produced a maximum power of 3.01 × 10 -6 μW, at an optimum load of 560 kΩ.

A NOVEL DESIGN OF 17.5 KV HV FEEDTHROUGH FOR ARJUNA 2.0

A NOVEL DESIGN OF 17.5 KV HV FEEDTHROUGH FOR ARJUNA 2.0. A novel design of the 17.5 kV feedthrough for Arjuna 2.0 Cockcroft Walton generator has been proposed. It is used for connecting the output of RF transformer oscillator (in the outside of horizontal vessel) with the input of voltage multiplier (inside of horizontal vessel) of the Cockcroft Walton generator. It was equipped by covers on left and right side. The designed feedthrough was simple, compact, easy to manufacture, high performance to prevent flashover and also it was applied to Arjuna 2.0 Cockcroft Walton. It was made from teflon (PTFE) and solid copper, which have high dielectric strength, capable of withstanding press loads, and easy to manufacture. The shortest distance between grounding with conductor radially was 43.25 mm, and 253.5 mm for feedthrough surface. The design was verified by Finite Element Method software and continued with performance testing. According to simulation, the stress of voltage is high about 16 kV to 17.5 kV on feedthrough conductor and 0 to 3 kV on feedthrough flange. The electric field of the covered feedthrough is lower than the coverless feedthrough. The highest and lowest electric fields are 1.26 x 106 V/m and 1 x 105 to 2 x 105 V/m respectively. Furthermore, feedthrough has been tested up to 120 kV and no discharge occurred. It means this design can be operated for 17.5 kV and it was successful installed on Arjuna 2.0 Cockcroft Walton generator.