Non-hermetic cable connection to enable high voltage in low & medium vacuum: identification of critical cable interface

Higher actuator voltages are required for future generation lithography machines. The operating pressures, down to the medium pressure range, in combination with relevant distances can be situated near gas breakdown according to Paschen curves. Partial discharges may occur, making long-term damage conceivable. Characterization of the partial discharge inception voltage of a cable connection as function of pressure, will reveal limitations. An experimental method is proposed to recognize partial discharges originating from the critical cable interface and is applied for a RG58U cable. The result is characterized in terms of a widened and scaled Paschen curve

Influencing factors in partial discharge cable performance characterization under low and medium vacuum conditions

Prior study has shown that quantifying performance of cables operational under a wide range of gas pressures, based on partial discharge inception voltage in relation to its design, is feasible. However, inception of partial discharges occur at weakest spots, of which the occurrence has a stochastic nature. This raises the question on the reproducibility of the methodology. Multiple cables of the same type are tested as well a single cable multiple times. Analyses of variance is used to evaluate the reproducibility and in some cases a significant difference is found. Besides reproducibility, test factors like method of voltage application may affect results and is investigated as well

Partial discharge detection for characterizing cable insulation under low and medium vacuum conditions

Design of cables for operation in a low pressure environment is challenging, when applications also demand lightweight and flexibility, and material choice is restricted. The operating pressures in combination with relevant distances, can be situated near gas breakdown and cause partial discharges, making long-term damage conceivable. An experimental setup is developed, based on partial discharge detection in a vacuum system, to characterize the partial discharge inception voltage of three coaxial cable designs in an argon and nitrogen environment at controllable pressure. In order to cope with outgassing behavior, a lumped element model is presented to simulate the internal pressure distribution along the cable as a function of settling time. Microscopic cross sections of the cables are analysed with electrostatic voltage simulations. Using scaled Paschen curves, expected partial discharge inception is determined and compared with measurements. Quantifying cable performance, in terms of minimum PD inception voltage and pressure, in relation to its design is feasible, but also deviations occur which are discussed

Non-hermetic cable design to enable high voltage in low & medium vacuum

Future generation lithography machines require a significant increase in actuation power of the moving stages, in order to ensure the continuous demand for improved productivity. Higher current levels to the actuators could achieve this, but it requires thicker conductors which increases mass and hampers flexibility. Operation of modern extreme ultraviolet (EUV) lithography machines demand a high flexibility of the cables to ensure a lifespan of 109 movements. The option pursued here, therefore, is higher voltage, i.e. a value possibly exceeding the Paschen minimum, whereas the operating pressure may go down to 0.1 Pa

Operational conditions influencing the partial discharge performance of cables under low and medium vacuum

The performance of flexible cables for applications at the kilovolt level over a gas pressure range from below 1 Pa to ambient needs to be quantified. Braided cable designs provide the flexibility, but necessarily contain voids where at certain pressure values the Paschen minimum voltage can be exceeded. In our prior research a methodology was proposed based on partial discharge diagnostics. However, the reproducibility needs to be investigated in view of the stochastic occurrence of the discharges in cable voids differing in shape and size. From a cable with braided screen, the variation of the partial discharge inception voltage as function of pressure is characterized, both for tests on different samples and for consecutive tests on the same sample. Variation between different samples is significantly larger, but overall the performance is reproduced within typically 20%. Based on analysis of variance, results are found to be robust against experimental parameters defining the partial discharge inception criteria. In addition, the influence of external parameters such as temperature, magnetic field and radiation exposure, which can be part of the operational conditions of equipment, is investigated. It is found that temperature rise resulted in a performance increase of the cable, which is not in line with expectations from the change in gas density but may be attributed to reduced secondary electron emission. Exposure to magnetic field and γ-radiation did not show noticeable effect

Compact topology for adjustable high-voltage pulse generation with drift step recovery diodes

In this paper we present a circuit topology with driftstep recovery diodes. We will explore the effect of higher forward and reverse currents on the circuit performance. In addition, we realized an adjustable output voltage of the pulser. The primary capacitor voltage can be varied while maintaining proper saturation of the pulse transformer. We will introduce a solution with a pre-magnetizing circuit on the primary winding so that a third winding is not needed

Compact pulse topology for adjustable high-voltage pulse generation using an SOS diode

In this paper, a compact circuit topology is presented for pulsed power generation with a semiconductor opening switch (SOS). Such circuits require the generation of a fast forward current through the diode, followed by a reverse current that activates the recovery process. In general, magnetic switches are used to switch the diode current from forward to reverse. Therefore, adjustment of the output voltage of an SOS pulser is difficult. This paper introduces a circuit that allows an adjustable output voltage of the pulser. A solution is realized with a premagnetizing circuit on the primary winding of a pulse transformer (PT), so that a third winding is not needed. The primary capacitor voltage can now be varied while maintaining proper saturation of the PT