Cold-cathode Penning discharge-based ionizer for detection of hyperthermal neutral beams

Abstract

Plasmas produced in a cold-cathode Penning discharge have been studied for possible use as an active ionizing medium in commercial quadrupole mass/energy analyzers for detection of low-energy neutral beams. Two distinct Penning discharge modes have been examined: (1) high-pressure (HP) mode and (2) high magnetic field (HMF) mode. It is shown that the ionization efficiency in the HP mode is independent of the length of ionization region; however, somewhat high working pressures (p>10(-4) Torr) and large discharge currents limit the practical use of this mode. This is not the case in the HMF mode, which appears at lower pressures, with an effective ionization region length of the order of electron cyclotron radius. The design and operation of a compact (5x4x4 cm(3)), low-maintenance ionizer based on a Penning cell with permanent magnets is described. The ability to ionize 40 eV neutral-argon beams with subsequent detection in a Hiden EQP energy-resolved mass spectrometer is shown. The ionization efficiency of the ionizer was found to be as high as 10(-3). Unlike conventional electron impact ionizers, the Penning discharge configuration allows to eliminate the thermal background component in the detected signal. The ionizer has potential application for the detection of hyperthermal neutral beams of various species.

Non‐Electrostatic Diagnostics for Ion Beams

“…The obtained momentum transfer coefficient is c rep = 1.20 for a beam energy of E i+n = 100 eV, and increases to c rep = 1.36 for a beam energy of E i+n = 500 eV. (6), and (7). The fit accounts at the same time for the currents shown in Fig.…”

“…Energy selective mass spectrometers could perform this task if they are supplemented with a suitable beam ionizer for the energetic neutral atoms, and its energy dependent ionization efficiency is known [7]. Energy selective mass spectrometers could perform this task if they are supplemented with a suitable beam ionizer for the energetic neutral atoms, and its energy dependent ionization efficiency is known [7].…”

“…For a direct measurement of these neutral beam components, other than purely electrostatic diagnostics are needed. Energy selective mass spectrometers could perform this task if they are supplemented with a suitable beam ionizer for the energetic neutral atoms, and its energy dependent ionization efficiency is known [7]. However, such devices are expensive and bulky, which limits the number of applications.…”

Разрядные Характеристики Плазменного Источника Пеннинга

“…Широкое распространение получили магниторазрядные датчики давления [1], ионные источники как для напылительных установок [2], так и для миниатюрных линейных ускорителей [3][4][5]9,10]. Данный тип разряда применяется и в системах электромагнитной сепарации изотопов [6], в источниках калиброванного светового излучения [7], в источниках гипертермальных пучков нейтральных частиц [12].…”

Non-electrostatic diagnostics for ion beams and sputter effects

“…In other cases, a conversion of the ion beam into a neutral beam is intended, for instance for heating of fusion plasmas. Energy selective mass spectrometers equipped with beam ionizers for the energetic neutral atoms could measure these neutral beam components [7]. However, such devices are expensive and bulky, which limits the number of applications.…”