Y. Raitses

• Doctor of Philosophy
• Principal Investigator at Princeton University

Electron beam (e-beam) generated plasmas with applied crossed electric and magnetic ( E×B) fields are promising for low-damage (gentle) material processing. However, these plasmas can be subject to the formation of plasma non-uniformities propagating in the E×B direction. These rotating plasma structures (or “spokes”) enhance the transport of charg...

Two-dimensional particle-in-cell simulations in the (radial-azimuthal) plane perpendicular to the axial direction of a cylindrical E×B Penning discharge are presented. The low-pressure discharge is self-consistently supported by plasma ionization from the electron beam injected axially, along the direction of the external magnetic field. It is show...

Two-dimensional particle-in-cell simulations in the (radial-azimuthal) plane perpendicular to the axial direction of a cylindrical ExB Penning discharge are presented. The low-pressure discharge is self-consistently supported by plasma ionization from the electron beam injected axially, along the direction of the external magnetic field. It is show...

A direct current arc discharge in a methane atmosphere is a scalable and sustainable method to produce metal-carbon core–shell nanoparticles and single-walled carbon nanotubes, where a metal catalyst can be continuously supplied through evaporation of an anode made from the catalyst material. The size of catalyst particles is of critical importance...

The photon-stimulated emission of bulk electrons has been extensively studied for various types of materials, while the photodetachment of surplus surface electrons has not been fully explored. The photodetachment barrier energy is commonly defined by the surface electron affinity of material, which is typically less than the work function and more...

Electron beam (e-beam) generated plasmas with applied crossed electric and magnetic ( E×B) fields are promising for low damage processing of materials with applications to microelectronics and quantum information systems. In cylindrical e-beam E×B plasmas, radial confinement of electrons and ions is achieved by an axial magnetic field and radial el...

Electron beam (e-beam) generated plasmas with applied cross electric and magnetic $\left( \textbf{E} \times \textbf{B} \right)$ fields are promising for low-damage material processing. However, these plasmas can be subject to the formation of azimuthally propagating structures that enhance the radial transport of energetic charged species, which ca...

A wide variety of feed gases are used to generate low-temperature plasmas for the microelectronics and sustainability applications. These plasmas often have a complex combination of reactive and nonreactive species which may have spatial and temporal variations in density, temperature, and energy. Accurate knowledge of these parameters and their va...

In pursuit of diamond nanoparticles, a capacitively-coupled radio frequency flow-through plasma reactor was operated with methane-argon gas mixtures. Signatures of the final product obtained microscopically and spectroscopically indicated that the product was an amorphous form of graphite. This result was consistent irrespective of combinations of...

A direct current (DC) arc discharge is a widely used method for large-scale production of metal nanoparticles, core–shell particles, and carbon nanotubes. Here, the growth of iron nanoparticles is explored in a modified DC arc discharge. Iron particles are produced by the evaporation of an anode, made from low-carbon steel. Methane admixture into a...

Laser-Induced Fluorescence (LIF) spectroscopy is an essential tool for probing ion and atom velocity distribution functions (VDFs) in complex plasmas. VDFs carry information about the kinetic properties of species that is critical for plasma characterization. Accurate interpretation of these functions is challenging due to factors such as multicomp...

In this work, we present the development and implementation of a high-resolution optical diagnostic system designed for in situ monitoring and measurement of wall erosion in electric propulsion devices, particularly Hall thrusters. The diagnostic system is based on a refined Long-Distance Microscope (LDM) system, positioned externally to simplify o...

Electron beam (e-beam) generated plasmas with applied crossed electric and magnetic $\left(\mathbf{E} \times \mathbf{B}\right)$ fields are promising for low damage processing of materials with applications to microelectronics and quantum information systems. In cylindrical e-beam $\mathbf{E} \times \mathbf{B}$ plasmas, radial confinement of electro...

A wide variety of feed gases are used to generate low-temperature plasmas for the microelectronics and the sustainability applications. These plasmas often have a complex combination of reactive and non-reactive species which may have spatial and temporal variations in the density, the temperature and the energy. Accurate knowledge of these paramet...

We propose the application of helium line intensity ratio spectroscopy in a low-pressure (0.3 mTorr) xenon E×B discharge at an electron temperature of $\sim$2 eV and a density of 10 ¹⁰ -10 ¹¹ cm ⁻³ . We successfully identified the helium atom line emissions at 388.9, 447.1, 501.6, 504.8, and 706.5 nm with helium pressures of up to ~20 mTorr. The me...

Quantum technologies based on quantum point defects in crystals require control over the defect charge state. Here we tune the charge state of shallow nitrogen-vacancy and silicon-vacancy centers by locally oxidizing a hydrogenated surface with moderate optical excitation and simultaneous spectral monitoring. The loss of conductivity and change in...

Several recent experiments have demonstrated low-damage processing of 2D materials, such as graphene and single crystal diamond, using electron beam (e-beam) generated plasmas with applied crossed electric and magnetic (E × B) fields. The low damage of these sensitive materials is commonly attributed to the low energy of ions incident to the substr...

Electron beam (e-beam) generated plasmas are useful for material processing applications such as deposition and etching because the plasmas deliver a large fluence of very low energy of ions to surfaces. Metastable species produced in the beam-region can also transport significant energy to the plasma periphery and surfaces. In this work, we have i...

Cold atmospheric plasma (CAP) in open air hosts numerous chemical species engaged in thousands of chemical reactions. Comprehensive diagnosis of its chemical composition is important across various fields from medicine, where reactive oxygen and nitrogen play key roles, to surface modification. In applications, a centimeter-scale helium-air jet ope...

In this work, we report an annular beam confocal laser-induced fluorescence (LIF) configuration, which allows for high spatial resolution measurements of plasma properties in plasma setups and sources with limited optical access. The proposed LIF configuration utilizes the annular laser beam generated by a pair of diffractive axicons. The LIF signa...

Laser-stimulated electron photo-detachment (LSPD) from nanoscale dust particles is predicted to strongly depend on the particle size. A theory of the electron photo-detachment from charged spherical metallic nanoparticles is presented. This theory is relevant to laser-stimulated photo-detachment applied to measurements of charge of nanoparticles in...

Hall Thrusters typically operate at thrust densities on the order of 10 N/m^2, which appear to be orders of magnitude below the thrust density limits suggested in previous literature. These limits have been considered here and each component of thrust density is analyzed to demonstrate the relative contribution to the total thrust density. Dependen...

In this work, we report a confocal laser induced fluorescence (LIF) configuration, which allows for high spatial resolution measurements of plasma properties in plasma setups and sources with a limited optical access. The proposed LIF configuration utilizes a ring-shaped laser beam generated by a pair of diffractive axicons. LIF signal is collected...

Azimuthal structures in cylindrical Penning discharge are studied with a 2D3V radial–azimuthal PIC/MCC model with the axial magnetic field. The discharge is self-consistently supported by ionization due to the axial injection of electrons. It is shown that the steady-state discharge can be supported in two different regimes with different types of...

Hall Thrusters typically operate at thrust densities on the order of 10 N/m2, which is well below the thrust density limits discussed in previous literature. These limits have been considered here and each component of thrust density is analyzed to demonstrate the relative contribution to the total thrust density. Dependencies of the thrust density...

Azimuthal structures in cylindrical Penning discharge are studied with 2D3V radial-azimuthal PIC/MCC model with the axial magnetic field. The discharge is self-consistently supported by ionization due to the axial injection of electrons. It is shown that the steady-state discharge can be supported in two different regimes with different type of obs...

We discuss the consequences of the quantum uncertainty on the spectrum of the electron emitted by the β-processes of a tritium atom bound to a graphene sheet. We analyze quantitatively the issue recently raised by Cheipesh, Cheianov, and Boyarsky [Phys. Rev. D 104, 116004 (2021)], and discuss the relevant timescales and the degrees of freedom that...

Low-frequency axial oscillations in the range of 5–50 kHz stand out as a pervasive feature observed in many types of Hall thrusters. While it is widely recognized that the ionization effects play the central role in this mode, as manifested via the large-scale oscillations of neutral and plasma density, the exact mechanism(s) of the instabilities r...

The PTOLEMY transverse drift filter is a new concept to enable precision analysis of the energy spectrum of electrons near the tritium β -decay endpoint. This paper details the implementation and optimization methods for successful operation of the filter for electrons with a known pitch angle. We present the first demonstrator that produces the re...

We discuss the consequences of the quantum uncertainty on the spectrum of the electron emitted by the $\beta$-processes of a tritium atom bound to a graphene sheet. We analyze quantitatively the issue recently raised in [Cheipesh et al., Phys. Rev. D 104, 116004 (2021)], and discuss the relevant time scales and the degrees of freedom that can contr...

Low-frequency axial oscillations (5-50 kHz) stand out as a pervasive feature observed in many types of Hall thrusters. While it is widely recognized that the ionization effects play the central role in this mode, as manifested via the large scale oscillations of neutral and plasma density, the exact mechanism(s) of the instabilities remain unclear....

. In the atmospheric pressure anodic carbon arc, ablation of the anode serves as a feedstock of carbon for production of nanomaterials. It is known that the ablation of the graphite anode in this arc can have two distinctive modes with low and high ablation rates. The transition between these modes is governed by the power deposition at the arc att...

In the absence of the channel walls bounding the plasma, a wall-less Hall thruster is a promising configuration with a potentially longer lifetime and easier scalability than conventional Hall thrusters. Because the ion acceleration takes place in the fringing magnetic field with a strong axial component, the operation of a typical wall-less thrust...

Hall effect thrusters operating at power levels in excess of several hundreds of kilowatts have been identified as enabling technologies for applications such as lunar tugs, large satellite orbital transfer vehicles, and solar system exploration. These large thrusters introduce significant testing challenges due to the propellant flow rate exceedin...

In the atmospheric pressure anodic carbon arc, ablation of the anode serves as a feedstock of carbon for production of nanomaterials. It is known that the ablation of the graphite anode in this arc can have two distinctive modes with low and high ablation rates. The transition between these modes is governed by the power deposition at the arc attac...

In wall-less Hall thrusters, the ionization of the propellant and the acceleration of the ions occur outside the thruster [S. Mazouffre, S. Tsikata, and J. Vaudolon, in 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (American Institute of Aeronautics and Astronautics, Cleveland, OH, 2014)]. This reduces interactions between the plasma and the...

Implementation details and optimization methods are presented for operation of the PTOLEMY transverse drift electromagnetic filter in low field. Low field operation introduces new challenges for tritium endpoint electron transport. The growth of the cyclotron radius in low field conditions puts a ceiling on filter performance relative to fixed filt...

The application of the magnetically insulated baffled probe (MIBP) and MIBP cluster for studying properties of low-temperature and peripheral fusion plasmas is reviewed. MIBP operation principles, MIBP design strategy, and MIBP examples of measurement, data analysis, and interpretation are discussed. The implementation convenience and diagnostic us...

Low frequency ionization oscillations involving plasma and neutral density (breathing modes) are the most violent perturbations in Hall thrusters for electric propulsion. Because of its simplicity, the zero-dimensional (0-D) predator-prey model of two nonlinearly coupled ordinary differential equations for plasma and neutral density has been often...

Low-frequency ionization oscillations involving plasma and neutral density (breathing modes) are the most violent perturbations in Hall thrusters for electric propulsion. Because of its simplicity, the zero-dimensional (0D) predator–prey model of two nonlinearly coupled ordinary differential equations for plasma and neutral density has often been u...

Nonlinear plasma structures in the partially magnetized E × B plasma of a cylindrical magnetron are investigated using 2D3V particle-in-cell Monte Carlo collision simulations. In the early phase of the discharge, plasma gradients and radial electric fields excite a lower hybrid type instability that forms long wavelength rotating density spokes. As...

A typical Hall thruster is powered from a DC power supply and operates with a constant discharge voltage. In operation, the discharge current is subject to strong low frequency oscillations (so-called breathing oscillations). Recent studies have shown that not only can these breathing oscillations be correlated with improved performance, but these...

Conventional expressions and definitions describing performance of plasma thrusters, including the thrust, specific impulse, and the thruster efficiency, assume a steady-state plasma flow with a constant flow velocity. However, it is very common for these thrusters that the plasma exhibits unstable behavior resulting in time variations of the thrus...

There is an urgent need for disinfection and sterilization devices accessible to the public that can be fulfilled by innovative strategies for using cold atmospheric pressure plasmas. Here, we demonstrate a successful novel combination of a flexible printed circuit design of a dielectric barrier discharge (flex-DBD) with an environmentally safe che...

The chemical functionalization of two-dimensional materials is an effective method for tailoring their chemical and electronic properties with encouraging applications in energy, catalysis, and electronics. One exemplary 2D material with remarkable properties, graphene, can be exploited for hydrogen storage and large on/off ratio devices by hydroge...

This paper provides perspectives on recent progress in understanding the physics of devices in which the external magnetic field is applied perpendicular to the discharge current. This configuration generates a strong electric field that acts to accelerate ions. The many applications of this set up include generation of thrust for spacecraft propul...

It is known by now that on inanimate surfaces, infectious SARS-CoV2 virions can be detected for up to 3 days which poses challenges for limiting transmission [1]. While heat and chemicals have proven to be effective for inactivating viruses such as SARS-CoV2, those methods cannot be readily applied to all surfaces/materials which may be heat labile...

There is an urgent need for disinfection and sterilization devices accessible to the public that can be fulfilled by innovative strategies for using cold atmospheric pressure plasmas. Here we explore and evaluate an approach combining a flexible printed circuit design of a dielectric barrier discharge (DBD) with an environmentally safe chemical rea...

In this work, solid targets made from boron and boron nitride (BN) materials are ablated by a nanosecond pulsed laser at sub-atmospheric pressures of nitrogen and helium gases. The excited species in the ablation plume from the target are probed by spatiotemporally resolved optical emission spectroscopy (OES). The evaluation of the chemical composi...

This document is a joint response by scientists from the Princeton Plasma Physics Laboratory, IBM T. J. Watson Research Center and Applied Materials, Inc. to the DOE Office of Science (DOE-SC) Request for Information: Basic Research Initiative for Microelectronics (https://www.federalregister.gov/documents/2019/07/12/2019-14869/request-for-informat...

Hall thrusters contain many instabilities which are known to affect thruster performance, with instability strength varying with thruster regime. One such instability, the breathing mode, can dominate the discharge with current oscillation amplitudes equal to the mean current value. Previous works have shown these large amplitude oscillations can b...

This paper provides perspectives on recent progress in the understanding of the physics of devices where the external magnetic field is applied perpendicularly to the discharge current. This configuration generates a strong electric field, which acts to accelerates ions. The many applications of this set up include generation of thrust for spacecra...

In the white paper we describe a national program in Low Temperature Plasma (LTP). The program should take advantage of the research opportunities of 3 rapidly growing areas (nanomaterial plasma synthesis, plasma medicine, microelectronics). The main theme is to achieve a fundamental understanding of Low Temperature Plasmas as they are applied to t...

In this work, solid targets made from boron and boron nitride (BN) materials are ablated by a nanosecond pulsed laser at sub-atmospheric pressures of nitrogen and helium gases. Excited species in the ablation plume from the target are probed with spatiotemporally resolved optical emission spectroscopy (OES). Evaluation of chemical composition in th...

Traditional expressions and definitions describing performance of plasma thrusters, including the thrust, specific impulse, and the thruster efficiency, assume a steady state plasma flow with a constant flow velocity. However, it is very common for these thrusters that the plasma exhibits unstable behavior resulting in time-variations of the thrust...

Plasma-wall interaction in the presence of secondary electron emission (SEE) can lead to a degradation and reduction in the performance of plasma devices. Materials with complex surface architectures such as velvet, fuzz, and feathered surfaces have a lower SEE yield than the same materials with a flat surface and can, therefore, be useful for plas...

DOI:https://doi.org/10.1103/PhysRevLett.123.239903

We propose the application of the helium line intensity ratio spectroscopy to a xenon plasma with the collisional-radiative (CR) model on the ADAS. By mixing helium gas with a xenon discharge up to 20 mtorr, we successfully obtain the He I emission from the plasma. Langmuir probe measurement shows the electron temperature and density did not change...

The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the...

Coagulation growth kinetics of nanoparticles in plasma is affected by interparticle electrostatic forces due to the charging phenomenon. In stationary plasmas, unipolar charging of particles results in retardation of particle growth and may result in a limitation on particle size. We demonstrate the opposite effect of enhanced particle growth in at...

A high-yield production of high-quality boron-nitride nanotubes (BNNTs) was reported recently in several publications. A boron-rich material is evaporated by a laser or plasma in a nitrogen-rich atmosphere to supply precursor gaseous species for nucleation and growth of BNNTs. Either hydrogen was added or pressure was increased in the system to ach...

Self-organization and anomalous transport in gradient-drift driven turbulence in partially magnetized plasmas with crossed electric and magnetic fields is demonstrated in two-dimensional fluid simulations. The development of large scale structures and flows is shown to occur as a result of the inverse energy cascade from short wavelength instabilit...

The spoke instability in an E × B Penning discharge is shown to be strongly affected by the boundary that is perpendicular to B field lines. The instability is the strongest when bounded by dielectric walls. With a conducting wall, biased to collect electron current from the plasma, the spoke becomes faster, less coherent, and localized closer to t...

The spoke instability in an $E\times B$ Penning discharge is shown to be strongly affected by the boundary that is perpendicular to $B$ field lines. The instability is the strongest when bounded by dielectric walls. With a conducting wall, biased to collect electron current from the plasma, the spoke becomes faster, less coherent and localised clos...

We performed self-consistent modeling of the atmospheric-pressure plasmas produced by arc discharges. Special numerical procedure for coupling of the plasma current, emission current, ion current, sheath voltage drop, heat fluxes at plasma-electrode interfaces was developed and implemented into the ANSYS CFX code. Validation of the simulation resul...

The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the...

The Hall thruster exhibits two types of large-scale coherent structures: axially propagating breathing mode (m = 0) and azimuthal, with low m, typically m = 1, spoke mode. In our previous work, it was demonstrated that axial breathing mode can be controlled via the external modulations of the anode potential. Two regimes of the thruster response, l...

We have developed a rapidly swept, back-to-back 100kHz Langmuir probe system using a tunable compensating network to study the temporal evolution of low frequency oscillations in Penning discharges, Hall Thrusters and other ExB discharges. Experimental validation of the probe system is done at low and high sweeping frequencies in a stable Penning d...

Azimuthal spoke-like modes commonly occur in ExB discharges. The natural occurrence of the spoke mode is correlated with changes of plasma parameters. Here, instead of allowing these changes to occur naturally, we report a technique for actively controlling the spoke by adjusting the boundary condition at the anode. The technique is demonstrated us...

A high-yield production of high-quality boron-nitride nanotubes (BNNTs) was reported recently in several publications. A boron-rich material is evaporated by a laser or plasma in a nitrogen-rich atmosphere to supply precursor gaseous species for nucleation and growth of BNNTs. Either hydrogen was added or pressure was increased in the system to ach...

We present a detailed description of the electromagnetic filter for the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Starting with an initial estimate for the orbital magnetic moment, the higher-order drift process of ExB is configured to balance the gradient-B drift motion of the electron in such a way as to guide the t...

The discharge and plasma plume characteristics of the cylindrical Hall thruster were studied in regimes with external modulations of the applied voltage. It is found that the amplitude and the root-mean-square (RMS) value of the discharge and ion currents increase with the amplitude of the external modulation exhibiting two different regimes. For s...

The secondary electron emission from a temperature-controlled Ni(110) sample was examined for 50–1500 eV electrons impacting at 0°–35°, 50°, and 78°. Measurements showed a non-cosine dependence on an electron incidence angle: the yield has a maximum at 0°, minima at ±12°, and increases at larger angles up to 35°. This trend in angular dependence is...

Azimuthal spoke-like modes commonly occur in ExB discharges. The natural occurrence of the spoke mode is correlated with changes of plasma parameters. Here, instead of allowing these changes to occur naturally, we report a technique for actively controlling the spoke by adjusting the boundary condition at the anode. The technique is demonstrated us...

The Electron Cyclotron Drift Instability (ECDI) driven by the electron E × B drift in partially magnetized plasmas is investigated with highly resolved particle-in-cell simulations. The emphasis is on two-dimensional effects involving the parallel dynamics along the magnetic field in a finite length plasma with dielectric walls. It is found that th...

Developments in the recent application of in situ diagnostics to improve understanding of nanomaterial synthesis processes in carbon arc plasma are summarized. These diagnostics measure the plasma conditions in the arc core and the precursor species to nanoparticle formation and the presence and sizes of nanoparticles in the synthesis region surrou...

We propose to achieve the proof-of-principle of the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Each of the technological challenges described in [1,2] will be targeted and hopefully solved by the use of the latest experimental developments and profiting from the low background environment provided by the LNGS undergrou...

Laser-induced fluorescence diagnostic technique is applied here to probe xenon neutrals and single-charged ions in an ambipolar plasma source. A single tunable diode laser is employed for pumping both following transitions: 6s ²[1/2]⁰₁-6p ² [3/2]⁰⠁ (centered at 834.68 nm; air) and 5d[4]7/2-6p[3]5/2 (centered at 834.72 nm; air), for Xe I and Xe II d...

The Electron Cyclotron Drift Instability driven by the electron E × B drift in partially magnetized plasmas is investigated with highly resolved particle-in-cell simulations. The emphasis is on two-dimensional effects involving the parallel dynamics along the magnetic field in a finite length plasma with dielectric walls. It is found that the insta...

A rotating plasma spoke is shown to develop in two-dimensional full-sized kinetic simulations of a Penning discharge cross-section. Electron cross-field transport within the discharge is highly anomalous and correlates strongly with the spoke phase. Similarity between collisional and collisionless simulations demonstrates that ionization is not nec...