A study to control charged particle transport across a transverse magnetic field (TMF), popularly known as the magnetic filter in a negative ion source, has been carried out in a double plasma device. In the experimental setup, the TMF placed between the two magnetic cages divides the whole plasma chamber into two distinct regions, viz., the source and the target on the basis of the plasma production and the corresponding electron temperature. The plasma produced in the source region by the filament discharge method diffuses into the target region through the TMF. Data are acquired by the Langmuir probe and are compared in different source configurations, in terms of external biasing applied to metallic plates inserted in the TMF plane but in the orthogonal direction. The effect of the direction of current between the two plates in either polarity of bias in the presence of TMF on the plasma parameters and the cross-field transport of charge particles are discussed.

We have studied the distribution patterns of lateral density, arrival time and angular position of Cherenkov photons generated in Extensive Air Showers (EASs) initiated by γ-ray, proton and iron primaries incident with various energies and at various zenith angles. This study is the extension of our earlier work [1] to cover a wide energy range of ground based γ-ray astronomy with a wide range of zenith angles (≤ 40 • ) of primary particles, as well as the extension to study the angular distribution patterns of Cherenkov photons in EASs. This type of study is important for distinguishing the γ-ray initiated showers from the hadronic showers in the ground based γ-ray astronomy, where Atmospheric Cherenkov Technique (ACT) is being used. Importantly, such study gives an insight on the nature of γ-ray and hadronic showers in general. In this work, the CORSIKA 6.990 simulation code is used for generation of EASs. Similarly to the case of Ref.[1], this study also revealed that, the lateral density and arrival time distributions of Cherenkov photons vary almost in accordance with the functions: ρ ch (r) = ρ0 e −βr and t ch (r) = t0e Γ/r λ respectively by taking different values of the parameters of functions for the type, energy and zenith angle of the primary particle. The distribution of Cherenkov photon's angular positions with respect to shower axis shows distinctive features depending on the primary type, its energy and the zenith angle. As a whole this distribution pattern for the iron primary is noticeably different from those for γ-ray and proton primaries. The value of the angular position at which the maximum number of Cherenkov photons are concentrated, increases with increase in energy of vertically incident primary, but for inclined primary it lies within a small value (≤ 1 • ) for almost all energies and primary types. No significant difference in the results obtained by using the high energy hadronic interaction models, viz., QGSJETII and EPOS has been observed.

A study on the transport of charged particles across a magnetic filter field has been carried out in a double plasma device (DPD) and presented in this manuscript. The DPD is virtually divided into two parts viz. source and target regions by a transverse magnetic field (TMF) which is constructed by inserting strontium ferrite magnets into two stainless steel rectangular tubes. Plasma electrons are magnetized but ions are unmagnetized inside the TMF region. Negative voltages are applied to the TMF tubes in order to reduce the loss of electrons towards them. Plasma is produced in the source region by filament discharge method and allowed to flow towards the target region through this negatively biased TMF. It is observed that in the target region, plasma density can be increased and electron temperature decreased with the help of negatively biased TMF. This observation is beneficial for negative ion source development. Plasma diffusion across the negatively biased TMF follows Bohm or anomalous diffusion process when negative bias voltage is very less. At higher negative bias, diffusion coefficient starts deviating from the Bohm diffusion value, associated with enhanced plasma flow in the target region.

We have investigated some features of the density and arrival time distributions of Cherenkov photons in extensive air showers using the CORSIKA simulation package. The main thrust of this study is to see the effect of hadronic interaction models on the production pattern of Cherenkov photons with respect to distance from the shower core. Such studies are very important in ground based γ-ray astronomy for an effective rejection of huge cosmic ray background, where the atmospheric Cherenkov technique is being used extensively within the energy range of some hundred GeV to few TeV. We have found that for all primary particles, the density distribution patterns of Cherenkov photons follow the negative exponential function with different coefficients and slopes depending on the type of primary particle, its energy and the type of interaction model combinations. Whereas the arrival time distribution patterns of Cherenkov photons follow the function of the form t(r) = t0ewith different values of the function parameters. There is no significant effect of hadronic interaction model combinations on the density and arrival time distributions for the γ-ray primaries. However, for the hadronic showers, the effects of the model combinations are significant under different conditions.

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