Characterization of a plasma window as a membrane free transition between vacuum and high pressure

TL;DR

This paper characterizes a plasma window that acts as a membrane-free transition between vacuum and high-pressure environments, detailing its properties, operational parameters, and durability for potential accelerator applications.

Contribution

It provides new insights into plasma window properties, including pressure behavior, plasma parameters, and durability, without ceramic insulators and with optical analysis of component wear.

Findings

Pressure up to 750 mbar achieved at low pressure side

No significant damage observed after 10 hours of operation

Cathode needle requires replacement after 5 hours

Abstract

A plasma window (PW) is a device for separating two areas of different pressures while letting particle beams pass with little to no loss. It has been introduced by A. Hershcovitch. In the course of this publication, the properties of a PW with apertures of 3.3 mm and 5.0 mm are presented. Especially the link between the pressure properties relevant for applications in accelerator systems and the underlying plasma properties depending on external parameters are presented. At the low pressure side around some mbar, high-pressure values reached up to 750 mbar while operating with volume flows between 1 slm and 4 slm (standard liter per minute) and discharge currents ranging from 45 A to 60 A. Unique features of the presented PW include simultaneous plasma parameter determination and the absence of ceramic insulators between the cooling plates. Optical analysis reveals no significant damage or wear to the components after an operation time well over 10 h, whereas the cathode needle needs replacement after 5 h.