Ion Feedback Research Articles

Brown macro-seaweeds derived agro-biostimulant for Zea mays farming in saline conditions: Growth enhancement and optimum biochemical and ion feedback

Salinity negatively affects maize growth, a cereal crop and used as a vital source of food production. Seaweeds are macro-aquatic biocatalysts and might act as a promising biostimulant for conferring crop salinity resistance by providing essential nutrients and growth-promoting regulators. This study was designed for the first time to examine the effects of two commonly found seaweeds, Iyengaria stellata and Colpomenia sinuosa, on the growth of maize under 0, 100, and 200 mM NaCl application. Plants treated with both salinities reduced plant growth, but the application of seaweed I. stellata and C. sinuosa significantly increased growth parameters, especially plant biomass (fresh and dry), length (root and shoot), and total plant height than other treatments. In addition, higher growth under seaweed amends was supported by improved chlorophyll, carbohydrates, carotenoids, and polyphenols as well as lower electrolyte leakages to escape from oxidative stress. Plants treated with both algal species enhanced Na+ and K+, which is important for osmotic balance and precise ion homeostasis and could be effective for optimum leaf metabolism for growth resilience of maize plants under saline-stress conditions. This study emphasizes the potential of C. sinuosa and I. stellata as effective biostimulants. They offer a sustainable approach to cultivating climate-resilient maize that can thrive in salt-affected environments.

Simulating the secondary electron avalanche of MCP by Geant4

Nowadays, Microchannel Plate (MCP), as a kind of electron multipliers based on the secondary electron emission, is widely used in many high-sensitive experiments, such as neutrino detection, which require the noise to be as low as possible, while the conventional straight-channel MCP will inevitably have ion feedback, resulting in the sequential after-pulses being the major source of noise. Normally, the problem can be effectively avoided by coupling two straight-channel MCPs in cascade and combining the channels into a “V” shape known as chevron MCPs, but this method is limited by the manufacturing techniques due to the unavoidable gap between the two pieces that will worsen the resolution and peak-to-valley ratio. However, the ion feedback can be inhibited significantly for MCPs with curved channels. Based on Geant4, we investigate how the geometrical parameters of curved-channel MCP influence the gain and get the optimum pore diameter for an MCP to reach the maximum gain with fixed thickness and applied voltage. Additionally, the track-by-track simulation reveals that the average acceleration distance of a secondary electron inside the curved-channel is approximately 20μm when the applied voltage, length-to-diameter ratio and pore diameter are 950 V, 50:1 and 20μm, respectively.

Study of afterpulsing in optical image intensifiers

We will describe the characteristics of the afterpulsing effect seen in the optical intensifiers. It can be caused by either secondary electrons produced by primary photoelectrons hitting the micro-channel plate surface or by electron emission from the photocathode induced by the ion feedback. The result of this effect are additional pulses delayed with respect to the primary parent pulses. Using a fast data-driven camera, Tpx3Cam, we were able to clearly show afterpulsing present in the data at short time differences and small distances from the primary pulse, as well as to show the evolution of the afterpulsing effect with increasing time difference. We also studied the afterpulsing spatial distribution and observed an azimuthal asymmetry, which we attribute to the afterpulsing ion component.

An investigation into the effect of exposing XMM–Newton’s Optical Monitor to the light of Jupiter

Abstract After nearly 18 yr of successful and safe operations, on 2017 July 17 and 18, XMM–Newton’s Optical Monitor (OM) observed Jupiter – an object 10 magnitudes brighter than safe brightness limits – in its visual (V) filter. The object was exposed 40 arcsec from the nominal European Photon Imaging Cameras pn boresight in the negative Y direction, creating a patch of depleted sensitivity. Two exposures of 4000 s each in the V filter left the sensitivity depleted in an area 70 by 40 arcsec; with the decrease in throughput varying from 34 per cent in the V filter to 15 per cent in the ultraviolet bands, but reaching a depth of 45 per cent in flat-field exposures. The wavelength dependency suggests the majority of the detector damage is due to loss of sensitivity in the photocathode from damage inflicted by ion feedback, while up to 15 per cent could be due to gain depletion of the MCP. The physical mechanisms causing the damage to the detector are discussed as well as possible solutions and opportunities that exist for the future operation of the OM.

Development of Micro-Pattern Gaseous Detectors for Nuclear Reaction Studies

One of the frontiers of today’s nuclear physics research is the synthesis of Super Heavy Elements (SHE). Fusion-fission dynamics, namely the competition between quasi fission and fusion is one of the key challenges to optimize the SHE. To have an insight into the dynamics, one requires the study of fission fragment mass and angular distribution near barrier energies for heavy-ion induced fission reactions. Recent successful installation of linear accelerators in India offers a unique opportunity to study the dynamics of nuclear reactions and formation process of SHE. For the effective utilization of these current, as well as upcoming facilities, development of novel detectors to study reaction dynamics, formation process of SHE with heavier projectiles and higher beam energies is needed. Gaseous detectors have undergone a rapid improvement in terms of spatial, temporal and energy resolution, rate capability, radiation hardness, ion feedback etc., ushering in a new genre of micro-structured devices based on semi-conductor technology, commonly known as Micro-Pattern Gaseous Detectors (MPGDs). Although many of the MPGD structures were primarily developed for high-rate tracking of charged particles in high energy physics experiments, stability of operation, simplicity of construction and relatively low cost make these detectors suitable for other applications, such as low-energy nuclear physics experiments. The present activities encompass a detailed evaluation of the operational conditions of Micromesh-Multi Wire and THGEM-Multi Wire hybrid detector operated in low-pressure isobutane gas with a view to optimizing their use in the detection of charged particles and fission fragments.

Study on the performance of a resistive Micromegas in a controlled O2 environment

Being the state of the art, the Micro-Pattern Gaseous Detectors (MPGD) are widely accepted in almost every particle collider experiment. Micromegas is a type of MPGD which is famous for its simple single-stage amplification, high and stable gain, low ion feedback, and excellent spatial and temporal resolutions.The chance of O2 contamination in a gaseous detector is not negligible as the abundance of O2 in air is nearly 21%. Contamination of detector-gas by O2 may occur due to insufficient gas-tightness or the use of long plastic pipes. Being an electronegative gas, O2 attach with the electrons inside a gaseous detector and influence the performance. The concern is higher when the detector has a large scale extension.We are reporting our measurements on the diffusion of O2 through a couple of commonly used plastic pipes. Then, in a hermetic gas system, by infusing O2 in a controlled and precise way, we have measured the effects of O2 on the performance of a resistive Micromegas. In pure Ar-CO2 mixture, we have also compared the gas-gain of the Micromegas with simulation to better estimate the gas-gap. The effects of temperature and pressure fluctuations on our study have also been investigated.

Maximum Sampling Region Acquisition and Contrast Calculation of Intensified Charge-Coupled Device Rectangular Target Image Under Low Illumination

Accurate acquisition of image contrast is an important factor for measuring modulation transfer function and minimum resolvable contrast of camera. Under low illumination, image from intensified charge-coupled device exhibits ion feedback noise with high brightness, resulting in lower signal-to-noise ratio of the image. Thus, one cannot obtain easily the accurate image contrast results by using the conventional contrast calculation method. In this paper, the ion feedback noise of the rectangular target image under low illumination is first reduced by means of constrained noise screening method and asymmetrical orientation window weighted mean filling algorithm. According to the spatial height correlation of the rectangular target image, the maximum sampling region is then founded by using spatial one-way statistical average algorithm combined with Otsu binarization. The image contrast is finally calculated after removing the fuzzy interval in the boundary between black and white stripes. It is shown that the method proposed can achieve the maximum sampling region acquisition and the contrast calculation for the image captured under low illumination, which reduces the error of calculation contrast caused by manually selecting the sampling region.

Experimental Study of the Positive Ion Feedback from Gas to Liquid in a Dual-Phase Argon Chamber and Measurement of the Ion Mobility in Argon Gas

The dynamics of the positive ions created by particle interactions inside argon time projection chambers plays an important role in characterizing the next generation of massive detectors planned for the direct search for dark matter and the study of neutrino properties. We have constructed a 1 L liquid argon chamber (ARION: ARgon ION experiment) with a high voltage pulse generator capable of injecting, in a controlled manner, a sizeable ion current into the drift region. This chamber is capable of reproducing a volume charge similar to that found in large detectors, allowing its effects to be studied systematically. New experimental results regarding ion dynamics in the liquid and direct demonstration of ion feedback from the gas to the liquid are discussed in this paper. In addition, a novel technique to measure the drift velocity of argon ions is introduced along with preliminary results obtained in gas.

Contribution of microchannel plate luminescence to the noise of 20-inch photomultiplier tubes

Since microchannel plate (MCP) photomultiplier tubes are used mainly to detect weak signals, their utility is greatly affected by their noise. This is true, for example, for the 20-inch MCP photomultiplier tubes used in high-energy physics research. We have built an MCP luminescence test system by coincidence testing method, and have analyzed the sources of such MCP luminescence by contrast test. We find that this MCP luminescence is due to electron multiplication in the photomultiplier tube. In order to analyze the proportion of MCP luminescence noise in an MCP photomultiplier tube, a noise model of the tube is established, including various sources of noise such as thermal electron emission from photocathode, MCP luminescence, MCP noise electron, glass luminescence, and ion feedback. Then we set up a test and evaluation system of MCP luminescence, measuring count-rate variations of 20-inch MCP photomultiplier tubes under incident light with different numbers of photoelectrons per pulse and different pulse rates. Through a series of calculations, the ratio of the noise from the MCP luminescence to the total noise of the 20-inch MCP photomultiplier tubes was determined. The results show that the luminescence noise of the MCP accounts for about 7 to 22% of the noise of the whole tube. Our analytic method can be extended to analyze the main noise sources of other MCP-type photomultiplier tubes, a direction worth pursuing to reduce noise and further improve the overall performance of MCP photomultiplier tubes.

Dark Matter Directionality Detection performance of the Micromegas-based [formula omitted]TPC-MIMAC detector

Directional Dark Matter Detection (DDMD) can open a new signature for Weakly Massive Interacting Particles (WIMPs) Dark Matter. The directional signature provides in addition, an unique way to overcome the neutron and neutrino backgrounds. In order to get the directional signature, the DDM detectors should be sensitive to low nuclear energy recoils in the keV range and have an angular resolution better than 20°. We have performed experiments with low energy (<30keV) ion beam facilities to measure the angular distribution of nuclear recoil tracks in a MIMAC detector prototype. In this paper, we study angular spreads with respect to the electron drift direction (0° incident angle) of Fluorine nuclear tracks in this low energy range, and show nuclear recoil angle reconstruction produced by a monoenergetic neutron field experiment. We find that a high-gain systematic effect leads to a high angular resolution along the electron drift direction. The measured angular distribution is impacted by diffusion, and space charge or ion feedback effects, which can be corrected for by an asymmetry factor observed in the flash-ADC profile. The estimated angular resolution of the 0° incident ion is better than 15° at 10 keV kinetic energy and agrees with the simulations within 20%. As it was not possible to inject ions at angles different from zero with respect to the electric drift field, we have performed experiments with monoenergetic neutrons producing nuclear recoils at all angles. The distributions from the nuclear recoils have been compared with simulated results based on a modified Garfield++ code. Our study shows that protons would be a more adapted target than heavier nuclei for DDMD of light WIMPs. We demonstrate that directional signature from the Galactic halo origin of a Dark Matter WIMP signal is experimentally achievable, with a deep understanding of the operating conditions of a low pressure detector with its diffusion mechanism.

Space charge in liquid argon time-projection chambers: a review of analytical and numerical models, and mitigation methods

The subject of space charge in ionisation detectors is reviewed, with particular attention to the case of liquid argon time projection chambers. Analytical and numerical description of the effects on the reconstructed coordinates along the drift and the transverse directions are presented. The cases of limited electron lifetime, of dual-phase detectors with ion feedback, and of detectors with small and comparable ratio between drift length and width are considered. Two design solutions that mitigates the effects are discussed.

Statistical and numerical analysis of secondary electron avalanches with ion-induced electron emission in air

Statistical and numerical analyses of secondary electron avalanches with ion-induced electron emission and multielectron initiation in air is carried out. Statistical analysis is based on the negative binomial distribution (NBD) and its mixtures and the mean number of electrons in avalanches is determined. The development of successive secondary electron avalanches for ion-induced electron emission from the cathode ($$ \gamma_{i} $$ process) in air is simulated by the fluid model. The statistics of secondary avalanches is described by a mixture of NBDs, and it is found that the mixing weights $$ a_{j} $$ are positively correlated with $$ \mu^{j} $$ for the contribution of secondary avalanche of $$ j $$th generation, where $$ \mu = \gamma_{i} [\exp (\alpha d) - 1] $$ is the avalanche regeneration factor. Gaussian continual approximations for the discrete negative binomial distribution are also applied to the experimental data and the mixing weights are determined. Our models can explain a deviation of the electron number distribution from exponential due to influence of ion feedback processes.

The effect of high-velocity dust particle impacts on microchannel plate (MCP) detectors

The detection efficiency and durability of a microchannel plate (MCP) detector to direct impacts of high-velocity dust particles is investigated experimentally. A new type of in situ time-of-flight cosmic dust analyzer instrument has been developed, where the ion detector is exposed to occasional impacts of cosmic dust particles. The dust accelerator facility operated at the University of Colorado is used to directly measure the effect of dust impacts on a commercial, off-the-shelf microchannel plate (MCP) detector. The MCP is exposed to approx. 480 dust particle impacts from wide size and velocity ranges of 0.05–1.6 μm radii and 2–35 km/s, respectively. The dust impact events are registered with 96% efficiency. Of these, 57% of the output signals are single charge pulses, and 43% are more complex signals that suggest ion feedback mechanisms within the detector. For all dust detection events, the output charge pulse is significantly larger than those from the detection of single ions or photons. The gain of the MCP detector shows no apparent degradation after the bombardment. In the investigated size/velocity range, the dust particles do not pose a risk of damaging the MCP. Scanning electron microscope images show that the impact generated craters are small, on the order of the size of the impacting particles. The performed measurements and the extrapolation of the results to the worst case expected to occur for the duration of a spaceflight mission indicate that MCP detectors require protection from dust impacts in order to reduce the risk of detector damage for these types of dust analyzer instruments, and a mechanism for providing protection is described.

Development of Gating Foils To Inhibit Ion Feedback Using FPC Production Techniques

Positive ion feedback from a gas amplification device to the drift region of the Time Projection Chamber for the ILC can deteriorate the position resolution. In order to inhibit the feedback ions, MPGD-based gating foils having good electron transmission have been developed to be used instead of the conventional wire gate. The gating foil needs to control the electric field locally in opening or closing the gate. The gating foil with a GEM (gas electron multiplier)-like structure has larger holes and smaller thickness than standard GEMs for gas amplification. It is known that the foil transmits over 80 % of electrons and blocks ions almost completely. We have developed the gating foils using flexible printed circuit (FPC) production techniques including an improved single-mask process. In this paper, we report on the production technique of 335 μm pitch, 12.5 μm thick gating foil with 80 % transmittance of electrons in ILC conditions.

Development of Resistive Micromegas for Sampling Calorimetry

Resistive micromegas is proposed as an active element for sampling calorimetry. Future linear collider experiments or the HL-LHC experiments can profit from those developments for Particle Flow Calorimetry. Micromegas possesses remarkable properties concerning gain stability, reduced ion feedback, response linearity, adaptable sensitive element granularity, fast response and high rate capability. Recent developments on Micromegas with a protective resistive layer present excellent results, resolving the problem of discharges caused by local high charge deposition, thanks to its RC-slowed charge evacuation. Higher resistivity though, may cause loss of the response linearity at high rates. We have scanned a wide range of resistivities and performed laboratory tests with X-rays that demonstrate excellent response linearity up to rates of (a few) times 10MHz/cm2, with simultaneous mitigation of discharges. Beam test studies at SPS/CERN with hadrons have also shown a remarkable stability of the resistive Micromegas and low currents for rates up to 15MHz/cm2. We present results from the aforementioned studies confronted with MC simulation

On the Role of Ionospheric Ions in Sawtooth Events

AbstractSimulations have suggested that feedback of heavy ions originating in the ionosphere is an important mechanism for driving sawtooth injections. However, this feedback may only be necessary for events driven by coronal mass ejections (CMEs), whereas in events driven by streaming interaction regions (SIRs), solar wind variability may suffice to drive these injections. Here we present case studies of two sawtooth events for which in situ data are available in both the magnetotail (Cluster) and the nightside auroral region (FAST), as well as global auroral images (IMAGE). One event, on 1 October 2001, was driven by a CME; the other, on 24 October 2002, was driven by an SIR. The available data do not support the hypothesis that heavy ion feedback is necessary to drive either event. This result is consistent with simulations of the SIR‐driven event but disagrees with simulation results for a different CME‐driven event. We also find that in an overwhelming majority of the sawtooth injections for which Cluster tail data are available, the O+ observed in the tail comes from the cusp rather than the nightside auroral region, which further casts doubt on the hypothesis that ionospheric heavy ion feedback is the cause of sawtooth injections.

Numerical Investigation on Electron and Ion Transmission of GEM-based Detectors

ALICE at the LHC is planning a major upgrade of its detector systems, including the TPC, to cope with an increase of the LHC luminosity after 2018. Different R&amp;D activities are currently concentrated on the adoption of the Gas Electron Multiplier (GEM) as the gas amplification stage of the ALICE-TPC upgrade version. The major challenge is to have low ion feedback in the drift volume as well as to ensure a collection of good percentage of primary electrons in the signal generation process. In the present work, Garfield simulation framework has been adopted to numerically estimate the electron transparency and ion backflow fraction of GEM-based detectors. In this process, extensive simulations have been carried out to enrich our understanding of the complex physical processes occurring within single, triple and quadruple GEM detectors. A detailed study has been performed to observe the effect of detector geometry, field configuration and magnetic field on the above mentioned characteristics.

Micro-channel plates in ionization mode as a fast timing device for future hadron colliders

At the high luminosity LHC (HL-LHC) about 200 concurrent interactions are expected, with a spread between the interaction vertices of few centimeters in the beam direction and 200 ps in the collision time. A time of flight resolution of the order of 30 ps would be able to reduce neutral particles pile-up contamination at the calorimeter level of about one order of magnitude, restoring pile-up conditions similar to what is routinely sustained in the current run of the LHC . Micro-channel plates have been used in PMT configuration as fast charged particles detector (resolution of better than 20 ps have been achieved with commercial devices), however they are not particularly radiation tolerant, mostly due to the ion feedback on the photocathode. The possibility of using micro-channel plates without a photocathode (i-MCP) has been studied in several test beams. Different MCP geometries are compared with the goal to identify the optimal configuration. Efficiency of more then 70% with a time resolution of better than 40 ps are achieved for single charged particles, leading to an efficiency close to 100% for EM shower after few radiation lengths. This open the possibility to use i-MCPs as a timing layer in a sampling calorimeter or to use it in a pre-shower device independent from the calorimeter technology.

3D simulation of electron and ion transmission of GEM-based detectors

Time Projection Chamber (TPC) has been chosen as the main tracking system in several high-flux and high repetition rate experiments. These include on-going experiments such as ALICE and future experiments such as PANDA at FAIR and ILC. Different R&D activities were carried out on the adoption of Gas Electron Multiplier (GEM) as the gas amplification stage of the ALICE-TPC upgrade version. The requirement of low ion feedback has been established through these activities. Low ion feedback minimizes distortions due to space charge and maintains the necessary values of detector gain and energy resolution. In the present work, Garfield simulation framework has been used to study the related physical processes occurring within single, triple and quadruple GEM detectors. Ion backflow and electron transmission of quadruple GEMs, made up of foils with different hole pitch under different electromagnetic field configurations (the projected solutions for the ALICE TPC) have been studied. Finally a new triple GEM detector configuration with low ion backflow fraction and good electron transmission properties has been proposed as a simpler GEM-based alternative suitable for TPCs for future collider experiments.

Experimental and numerical simulation of a TPC like set up for the measurement of ion backflow

Ion backflow is one of the effects limiting the operation of a gaseous detector at high flux, by giving rise to space charge which perturbs the electric field. The natural ability of bulk Micromegas to suppress ion feedback is very effective and can help the TPC drift volume to remain relatively free of space charge build-up. An efficient and precise measurement of the backflow fraction is necessary to cope up with the track distortion due to the space charge effect. In a subtle but significant modification of the usual approach, we have made use of two drift meshes in order to measure the ion backflow fraction for bulk Micromegas detector. This helps to truly represent the backflow fraction for a TPC. Moreover, attempt is taken to optimize the field configuration between the drift meshes. In conjunction with the experimental measurement, Garfield simulation framework has been used to simulate the related physics processes numerically.