Effect Of Earth's Magnetic Field Research Articles

EMF Shielding of One Set of Circular Coils with Slight Distortion

Jiangmen Undergroud Neutrino Observatory (JUNO) is a reactor antineutrino experiment with the main purpose for determining the neutrino mass hierarchy by precisely measuring the energy spectrum of nuclear reactor electron antineutrinos. The JUNO central detector consists of 20 kilotons an organic liquid scintillator filling the spherical CD or acrylic sphere whose diameter is 35.4 meters, surrounded by a water pool, approximately 18, 000 20″ and 25, 000 3″ photomultiplier tubes (PMTs) on the inner CD truss and 2,400 20″ Veto-PMT on the outer CD truss. The PMTs are very sensitive to external magnetic fields, the earth magnetic field (EMF) passing through the PMTs without any shielding would largely reduce the efficiency of the PMTs. In order to minimize the effect of EMF inside the detector, JUNO has been planing to use the DC coils to shield EMF, aiming at the residual EMF to less than 10 % on PMT areas.

Electron optics design of an 8-in. spherical MCP-PMT

This paper discusses the electron optical system of an 8-in. spherical MCP-PMT. The MCP assembly, the supporting pole and the supply voltages are carefully designed to optimize the photoelectron collection efficiency and the transit time spread. Coating the MCP nickel-chromium electrode with an additional high secondary emission material is employed to make a breakthrough on the collection efficiency. With the simulation software CST, the Finite Integration method and the Monte Carlo method are combined to evaluate the collection efficiency, the time properties and the Earth's magnetic field effects. Simulation results show that the photocathode active solid angle is over 3.5 πsr, the average collection efficiency can exceed 95% with the coated MCP and the mean transit time spread is 2.2ns for a typical electric potential of 500V applied between the photocathode and the MCP input facet. The prototype and the measured single photoelectron spectrum are also presented.

A new type of aerospace engine to remove space debris

We present a design concept for a space engine that can continuously remove orbital debris by using the debris powder as a propellant. Space debris represents a great potential threat to operational satellites, especially certain high-value spaceships. With the increasing risk of debris, researches reveal that it would reach a phenomenon named the Kessler syndrome that numerous operational satellites being destroyed in a chain reaction in low orbit in the not-far distant future. Initiative removing enough of the debris for the safety of space flight is an inevitable problem for human. Major space organizations are monitoring debris constantly with space debris environment models. At the same time, researchers have proposed a series of methods for removing the debris, such as using electrically conductive tethers to deorbit the debris, using robots with claws, nets or gecko-like suction cups to capture the debris and deploying ground-based or space-based laser to deorbit the debris. Nevertheless, large consumption of fuel for orbital transfer especially noncoplanar, chasing and rendezvousing with the debris is the leading restricting factor. In the concept of debris engine, a robotic space cleaner is used to capture the targeted debris and transfer it to engine. Large debris is firstly disintegrated into small pieces with diameters smaller than one centimeter using a mechanical method. A planetary ball mill is used to grind the pieces into powder with diameters of one micrometer or less. The energy required for this process is obtained from solar power or nuclear. The debris powder is then charged by electron beam. This charged condition can be used to accelerate the movement of the powder in a tandem electrostatic particle accelerator. Continuous thrust is generated by ejecting charged powder from the nozzle of engine because of momentum transfer. This thrust allow the spacecraft and robotic cleaner to perform orbital maneuvers and to rendezvous with other debris. The ejected charged particles will be blown away from the circumterrestrial orbit by solar wind and the effect of Earth magnetic field. Thus, digesting the space debris not only removes the orbital debris but also provides the necessary thrust to propel cleaner. Numerical simulation reveals the specific impulse of debris engine is determined by the accelerating electrostatic potential, charging potential and the charge-to-mass ratio of powder. In addition, the thrust of engine is largely dependent on the mass flow rate of the charged powder at the nozzle and nozzle jet velocity of the powder. With optimal regulation of the specific impulse and thrust, spacecraft can follow an optimal trajectory. In addition, this approach provides a new concept for asteroid exploration and interplanetary flight using a sustainable fuel supplement.

Earth magnetic field effects on Swarm electric field instrument

Earth magnetic field effects on the particle sensors carried by the Swarm satellites are investigated using particle in cell (PIC) and test-particle modelling. In the reference frame of the spacecraft in which plasma flows at relative velocity v→, Earth magnetic field leads to an ambient electric field E→=−v→×B→, which affects the shape of particle distribution functions at the particle sensors. This in turn impacts the distribution of particle fluxes on the microchannel plate (MCP) in the ram face mounted thermal ion imagers (TIIs). Shifts in the centroid of these distributions depend on the direction and magnitude of the local magnetic field and, as such, are expected to vary periodically along the spacecraft orbit. The magnitude of these shifts is estimated quantitatively, and the effect of their variation on the calibration and interpretation of the electric field instrument (EFI) are also discussed.

Earth magnetic field effects on the cosmic electron flux as background for Cherenkov Telescopes at low energies

Cosmic ray electrons and positrons constitute an important component of the background for imaging atmospheric Cherenkov Telescope Systems with very low energy thresholds. As the primary energy of electrons and positrons decreases, their contribution to the background trigger rate dominates over protons, at least in terms of differential rates against actual energies. After event reconstruction, this contribution might become comparable to the proton background at energies of the order of few GeV. It is well known that the flux of low energy charged particles is suppressed by the Earth’s magnetic field. This effect strongly depends on the geographical location, the direction of incidence of the charged particle and its mass. Therefore, the geomagnetic field can contribute to diminish the rate of the electrons and positrons detected by a given array of Cherenkov Telescopes.In this work we study the propagation of low energy primary electrons in the Earth’s magnetic field by using the backtracking technique. We use a more realistic geomagnetic field model than the one used in previous calculations. We consider some sites relevant for new generations of imaging atmospheric Cherenkov Telescopes. We also study in detail the case of 5@5, a proposed low energy Cherenkov Telescope array.