Dynamic Faraday cup signal analysis and the measurement of energetic ions emitted by plasma focus

Abstract

A theoretical model is developed to study the signals from a typical dynamic Faraday cup, and using this model the output signals from this structure are obtained. A detailed discussion on the signal structure, using different experimental conditions, is also given. It is argued that there is a possibility of determining the total charge of the generated ion pulse, the maximum velocity of the ions, ion velocity distribution, and the number of ion species for mixed working gases, under certain conditions. In addition, the number of different ionization stages, the number of different pinches in one shot, and the number of different existing acceleration mechanisms can also be determined provided that the mentioned conditions being satisfied. An experiment is carried out on the Filippov type 90 kJ Sahand plasma focus using Ar as the working gas at the pressure of 0.25 Torr. The data from a typical shot are fitted to a signal from the model and the total charge of the related energetic ion pulse is deduced using the values of the obtained fit parameters. Good agreement between the obtained amount of the total charge and the values obtained during other experiments on the same plasma focus device is observed.

Angular distribution of energetic argon ions emitted by a 90 kJ Filippov-type plasma focus

“…This effect may have several causes such as (1) existence of ions with several ionization degrees. 22,23 We have modeled the dynamical Faraday cup signals already 24 and shown that this may be the main cause of the signal broadening, (2) the existence of heavy charged impurities (such as Cu ions sputtered from copper anode of PF) can be another cause of broadening. This may be investigated using another diagnostics such as mass or X-ray spectrometry, and (3) other source of signal broadening can be the RC value of the related circuit.…”

Numerical Experiments on Ion-Beam Features Emitted from Different-Energy DPF Devices for Deuterium Gas

“…Dense Plasma Focus (DPF) devices are pulsed sources of neutrons [1][2][3][4][5], electron beams [6-8], soft x-ray radiation (SXR) [9][10][11][12][13][14][15] and ion beams [16][17][18][19][20][21][22][23]. Column of a pinched plasma in a PF device is believed to typically produce pulsed ions from several of 100 keV to several of MeV (considering ions emitted from the nuclear fusion reactions) [24][25][26][27][28][29].…”

“…Space-and time-resolved investigation of high energy deuterons emitted from three DPF devices was conducted [33]. Ion beams have been investigated using Faraday Cup (FC) as a diagnostic tool for ion current density alongside ion time-of-ight (ToF) measurements [18][19][20][21][22]. The ion energies are predominantly in the tens to hundreds of keV range, the pulse durations are tens of ns, and the currents are typically tens of kA [34].…”

Fast Faraday cup for fast ion beam TOF measurements in deuterium filled plasma focus device and correlation with Lee model

“…[4][5][6] For plasma focus devices, a Faraday Cup (FC) is a very useful diagnostic tool for ion current density and ion time of flight measurements. [7][8][9] The ion energies are predominantly in the tens to hundreds of keV range, the pulse durations are tens of ns, and the currents are typically tens of kA. 10,11 The velocity, energy, and density of nitrogen ions have been estimated using the FC TOF technique in a plasma focus device by Mohanty in 2005.…”