Charge State Measurements Research Articles

Impurity transport study based on measurement of visible wavelength high-n charge exchange transitions at W7-X

A recently installed high-speed charge exchange diagnostic at the W7-X stellarator has been used to identify several high-n Rydberg emission lines near 500 nm following impurity injections. The wavelengths of observed high-n Rydberg transitions are independent of the impurity species and originate from ions with ionization states ranging from 14+ to 45+ suggesting that this approach can be applied to a variety of heavy impurities. Moreover, little to no passive signal is observed since the high-n energy levels are unlikely to be populated by electron impact excitation. The combination of the newly developed diagnostic and the observation of high-n Rydberg states provides spatially resolved, high-speed measurements of multiple charge states which are analyzed in a Bayesian inference framework to determine both impurity diffusion and convection profiles. Measurements from the 2023 experimental campaign conclusively show high diffusion and an inward pinch in the core, well above predictions by neoclassical theory.

Accurate simultaneous lead stopping power and charge-state measurements in gases and solids: Benchmark data for basic atomic theory and nuclear applications

We have measured for the first time simultaneously both the mean charge states and stopping powers of (35–280) MeV/u 208Pb ions in gases and solids with an accuracy of 1%. The existence at lower energies and disappearance at higher of density effects in the charge-state distribution and the corresponding stopping power are directly confirmed and comparisons with widely used theories and simulations for heavy ions demonstrate strong deviations of up to 27%. However, an unprecedented prediction power of better than 3% has been achieved for the energy loss when the measured mean charge-states are implemented in the Lindhard-Sørensen theory. Our present benchmark data contribute to an improved understanding of the basic atomic collision processes and to numerous applications in nuclear physics. Extending the GANIL data [1] to higher accuracy and energies, we can now answer at which velocities the Bohr-Lindhard density effect in stopping will vanish.

Target Density Effects on Charge Transfer of Laser-Accelerated Carbon Ions in Dense Plasma.

We report on charge state measurements of laser-accelerated carbon ions in the energy range of several MeV penetrating a dense partially ionized plasma. The plasma was generated by irradiation of a foam target with laser-induced hohlraum radiation in the soft x-ray regime. We use the tricellulose acetate (C_{9}H_{16}O_{8}) foam of 2 mg/cm^{3} density and 1mm interaction length as target material. This kind of plasma is advantageous for high-precision measurements, due to good uniformity and long lifetime compared to the ion pulse length and the interaction duration. We diagnose the plasma parameters to be T_{e}=17 eV and n_{e}=4×10^{20} cm^{-3}. We observe the average charge states passing through the plasma to be higher than those predicted by the commonly used semiempirical formula. Through solving the rate equations, we attribute the enhancement to the target density effects, which will increase the ionization rates on one hand and reduce the electron capture rates on the other hand. The underlying physics is actually the balancing of the lifetime of excited states versus the collisional frequency. In previous measurement with partially ionized plasma from gas discharge and z pinch to laser direct irradiation, no target density effects were ever demonstrated. For the first time, we are able to experimentally prove that target density effects start to play a significant role in plasma near the critical density of Nd-glass laser radiation. The finding is important for heavy ion beam driven high-energy-density physics and fast ignitions. The method provides a new approach to precisely address the beam-plasma interaction issues with high-intensity short-pulse lasers in dense plasma regimes.

Noise-robust classification of single-shot electron spin readouts using a deep neural network

Single-shot readout of charge and spin states by charge sensors such as quantum point contacts and quantum dots are essential technologies for the operation of semiconductor spin qubits. The fidelity of the single-shot readout depends both on experimental conditions such as signal-to-noise ratio, system temperature, and numerical parameters such as threshold values. Accurate charge sensing schemes that are robust under noisy environments are indispensable for developing a scalable fault-tolerant quantum computation architecture. In this study, we present a novel single-shot readout classification method that is robust to noises using a deep neural network (DNN). Importantly, the DNN classifier is automatically configured for spin-up and spin-down traces in any noise environment by tuning the trainable parameters using the datasets of charge transition signals experimentally obtained at a charging line. Moreover, we verify that our DNN classification is robust under noisy environment in comparison to the two conventional classification methods used for charge and spin state measurements in various quantum dot experiments.

Identifying the Coronal Source Regions of Solar Wind Streams from Total Solar Eclipse Observations and in situ Measurements Extending over a Solar Cycle

Abstract This letter capitalizes on a unique set of total solar eclipse observations acquired between 2006 and 2020 in white light, Fe xi 789.2 nm (T fexi = 1.2 ± 0.1 MK), and Fe xiv 530.3 nm (T fexiv = 1.8 ± 0.1 MK) emission complemented by in situ Fe charge state and proton speed measurements from Advanced Composition Explorer/SWEPAM-SWICS to identify the source regions of different solar wind streams. The eclipse observations reveal the ubiquity of open structures invariably associated with Fe xi emission from Fe10+ and hence a constant electron temperature, T c = T fexi, in the expanding corona. The in situ Fe charge states are found to cluster around Fe10+, independently of the 300–700 km s−1 stream speeds, referred to as the continual solar wind. Thus, Fe10+ yields the fiducial link between the continual solar wind and its T fexi sources at the Sun. While the spatial distribution of Fe xiv emission from Fe13+ associated with streamers changes throughout the solar cycle, the sporadic appearance of charge states >Fe11+ in situ exhibits no cycle dependence regardless of speed. These latter streams are conjectured to be released from hot coronal plasmas at temperatures ≥T fexiv within the bulge of streamers and from active regions, driven by the dynamic behavior of prominences magnetically linked to them. The discovery of continual streams of slow, intermediate, and fast solar wind characterized by the same T fexi in the expanding corona places new constraints on the physical processes shaping the solar wind.

Temperature in Solar Sources of 3He-rich Solar Energetic Particles and Relation to Ion Abundances

Abstract 3He-rich solar energetic particles (SEPs) are believed to be accelerated in solar flares or jets by a mechanism that depends on the ion charge-to-mass (Q/M) ratio. It implies that the flare plasma characteristics (e.g., temperature) may be effective in determining the elemental abundances of 3He-rich SEPs. This study examines the relation between the suprathermal (≲0.2 MeV nucleon−1) abundances of the He–Fe ions measured on the Advanced Composition Explorer and temperature in the solar sources for 24 3He-rich SEP events in the period 2010–2015. The differential emission measure technique is applied to derive the temperature of the source regions from the extreme ultraviolet imaging observations on the Solar Dynamics Observatory. The obtained temperature distribution peaks at 2.0–2.5 MK that is surprisingly consistent with earlier findings based on in situ elemental abundance or charge state measurements. We have found a significant anticorrelation between 3He/4He ratio and solar source temperature with a coefficient −0.6. It is most likely caused by non-charge-stripping processes, as both isotopes would be fully ionized in the inferred temperature range. This study shows that the elemental ratios 4He/O, N/O, Ne/O, Si/O, S/O, Ca/O, Fe/O generally behave with temperature as expected from abundance enhancement calculations at ionization equilibrium. The C and Mg, the two species with small changes in the Q/M ratio in the obtained temperature range, show no such behavior with temperature and could be influenced by similar processes as for the 3He/4He ratio.

Certification of spin-based quantum simulators

Quantum simulators are engineered devices controllably designed to emulate complex and classically intractable quantum systems. A key challenge is to certify whether the simulator truly mimics the Hamiltonian of interest. This certification step requires the comparison of a simulator's output to a known answer, which is usually limited to small systems due to the exponential scaling of the Hilbert space. Here, in the context of Fermi-Hubbard spin-based analogue simulators, we propose a modular many-body spin to charge conversion scheme that scales linearly with both the system size and the number of low-energy eigenstates to discriminate. Our protocol is based on the global charge state measurement of a 1D spin chain performed at different detuning potentials along the chain. In the context of semiconductor-based systems, we identify realistic conditions for detuning the chain adiabatically in order to avoid state mixing while preserving charge coherence. Large simulators with vanishing energy gaps, including 2D arrays, can be certified block-by-block with a number of measurements scaling only linearly with the system size.

Quantifying the Effects of Charge Regulation on Disorder-Order Transitions of Highly Charged Protein Sequences

Charge regulation, which refers to the modulation of charge states of ionizable residues due to shifted pKa values, is an important albeit often overlooked determinant of sequence-ensemble and sequence-structure relationships of intrinsically disordered and intrinsically ordered proteins. We have developed complimentary computational and experimental approaches that account for the complete ensemble of charge states for a given sequence. This combined approach enables the computational calculation of conformational ensembles as a function of pH, and experimental measurement of charge states as a function of pH, allowing us to quantify the effects of charge regulation on archetypal sequences that are predicted to be intrinsically disordered. Here, we present results from a joint experimental and computational analysis of the effects of charge regulation on block-copolypeptides composed entirely of acidic and basic residues, (E4K4)n. These sequences form stable single alpha helices, although they are erroneously predicted to form disordered ensembles if one assumes fixed charge states for the ionizable residues. We employ a novel capillary electrophoresis method for measuring charge as a function of pH. These data, combined with potentiometric analysis, show that glutamate residues have highly shifted pKa values when compared to those of model compounds. This preferential neutralization of glutamate residues that are internal to the block co-polypeptide sequence engenders alpha helix formation by lowering the free energy of desolvation and enabling the favorable propagation of the alpha helix. These findings are readily explained using simulations based on the recently developed q-canonical Monte Carlo sampling method. Our results suggest that sequence-specific charge regulation can engender large-scale conformational transitions and even underlie the driving forces for phase separation. Further, our results highlight the need for refining disorder predictors based on an improved understanding of context dependent charge regulation effects.

Protons and carbon ions acceleration in the target‐normal‐sheath‐acceleration regime using low‐contrast fs laser and metal‐graphene targets

Abstractfs pulsed lasers at an intensity of the order of 1018 W/cm2, with a contrast of 10−5, were employed to irradiate thin foils to study the target‐normal‐sheath‐acceleration (TNSA) regime. The forward ion acceleration was investigated using 1/11 µm thickness foils composed of a metallic sheet on which a thin reduced graphene oxide film with 10 nm thickness was deposited by single or both faces. The forward‐accelerated ions were detected using SiC semiconductors connected in time‐of‐flight configuration. The use of intense and long pre‐pulse generating the low contrast does not permit to accelerate protons above 1 MeV because it produces a pre‐plasma destroying the foil, and the successive main laser pulse interacts with the expanding plasma and not with the overdense solid surface. Experimental results demonstrated that the maximum proton energies of about 700 keV and of 4.2 MeV carbon ions and higher were obtained under the condition of the optimal acceleration procedure. The measurements of ion energy and charge states confirm that the acceleration per charge state is measurable from the proton energy, confirming the Coulomb–Boltzmann‐shifted theoretical model. However, heavy ions cannot be accelerated due to their mass and low velocity, which does not permit them to be subjected to the fast and high developed electric field driving the light‐ion acceleration. The ion acceleration can be optimized based on the laser focal positioning and on the foil thickness, composition, and structure, as it will be presented and discussed.

Spatial Distribution of Element Abundances and Ionization States in Solar Energetic-Particle Events

We have studied the spatial and temporal distribution of abundances of chemical elements in large "gradual" solar energetic-particle (SEP) events, and especially the source plasma temperatures, derived from those abundances, using measurements from the Wind and Solar TErestrial RElations Observatory (STEREO) spacecraft, widely separated in solar longitude. A power-law relationship between abundance enhancements and mass-to-charge ratios [A/Q] of the ions can be used to determine Q-values and source plasma temperatures at remote spacecraft with instruments that were not designed for charge-state measurements. We search for possible source variations along the accelerating shock wave, finding one clear case where the accelerating shock wave appears to dispatch ions from 3.2+-0.8 MK plasma toward one spacecraft and those from 1.6+-0.2 MK plasma toward another, 116 deg away. The difference persists three days and then fades away. Three other SEP events show less-extreme variation in source temperatures at different spacecraft, in one case observed over 222 deg in longitude. This initial study shows how the power-law relation between abundance enhancements and ion A/Q-values pro-vides a new technique to determine Q and plasma temperatures in the seed population of SEP ions over a broad region of space using remote spacecraft with instruments that were not originally designed for measurements of ionization states.

Reversing the Landauer's erasure: Single‐electron Maxwell's demon operating at the limit of thermodynamic efficiency

AbstractAccording to Landauer's principle, erasure of information is the only part of a computation process that unavoidably involves energy dissipation. If done reversibly, such an erasure generates the minimal heat of per erased bit of information. The goal of this work is to discuss the actual reversal of the optimal erasure which can serve as the basis for the Maxwell's demon operating with ultimate thermodynamic efficiency as dictated by the second law of thermodynamics. The demon extracts of heat from an equilibrium reservoir at temperature T per one bit of information obtained about the measured system used by the demon. We have analyzed this Maxwell's demon in the situation when it uses a general quantum system with a discrete spectrum of energy levels as its working body. In the case of the effectively two‐level system, which has been realized experimentally based on tunneling of individual electron in a single‐electron box , we also studied and minimized corrections to the ideal reversible operation of the demon. These corrections include, in particular, the non‐adiabatic terms which are described by a version of the classical fluctuation–dissipation theorem. The overall reversibility of the Maxwell's demon requires, beside the reversibility of the intrinsic working body dynamics, the reversibility of the measurement, and feedback processes. The single‐electron demon can, in principle, be made fully reversible by developing a thermodynamically reversible single‐electron charge detector for measurements of the individual charge states of the single‐electron box.

A novel experimental setup for energy loss and charge state measurements in dense moderately coupled plasma using laser-heated hohlraum targets

We report on a new experimental setup for ion energy loss measurements in dense moderately coupled plasma which has recently been developed and tested at GSI Darmstadt. A partially ionized, moderately coupled carbon plasma (ne ≤ 0.8• 1022 cm-3, Te = 15 eV, z = 2.5, Γ = 0.5) is generated by volumetrical heating of two thin carbon foils with soft X-rays. This plasma is then probed by a bunched heavy ion beam. For that purpose, a special double gold hohlraum target of sub-millimeter size has been developed which efficiently converts intense laser light into thermal radiation and guarantees a gold-free interaction path for the ion beam traversing the carbon plasma. This setup allows to do precise energy loss measurements in non-ideal plasma at the level of 10 percent solid-state density.

Interaction of highly charged ions with carbon nano membranes

Charge state and energy loss measurements of slow highly charged ions (HCIs) after transmission through nanometer and sub-nanometer thin membranes are presented. Direct transmission measurements through carbon nano membranes (CNMs) show an unexpected bimodal exit charge state distribution, accompanied by charge exchange dependent energy loss. The energy loss of ions in CNMs with large charge loss shows a quadratic dependency on the incident charge state, indicating charge state dependent stopping force values. Another access to the exit charge state distribution is given by irradiating stacks of CNMs and investigating each layer of the stack with high resolution imaging techniques like transmission electron microscopy (TEM) and helium ion microscopy (HIM) independently. The observation of pores created in all of the layers confirms the assumption derived from the transmission measurements that the two separated charge state distributions reflect two different impact parameter regimes, i.e. close collision with large charge exchange and distant collisions with weak ion-target interaction.

A novel double hohlraum target to create a moderately coupled plasma for ion stopping experiments

We present a new double hohlraum target for the creation of a moderately coupled (0.1<Γ<1) carbon plasma for energy loss and charge state measurements of projectile ions interacting with this plasma. A spherical cavity of 600μm in diameter is heated with a 150-J laser pulse (λL=527nm) within 1.2ns to produce a quasi-Planckian X-ray source with a radiation temperature of Tr≈100eV. These X-rays are then used to heat volumetrically two thin carbon foils in a secondary cylindrical hohlraum to a dense plasma state. An axi-symmetric plasma column with a free-electron density of up to 8×1021cm-3, a temperature of T≈10eV, and an average ionization degree of Z≈3 is generated. This plasma stays in a dense and an almost uniform state for about 5ns. Ultimately, such targets are supposed to be used in experiments where a heavy ion beam is launched through the sample plasma, and the ion energy losses as well as the charge distributions are to be measured. The present paper is in a certain sense a symbiotic one, where the theoretical analysis and the experimental results are combined to investigate the basic properties and the prospects of this type of plasma targets.

Generation of multipartite entangled coherent states via a superconducting charge qubit

In this paper, we propose a method to generate multipartite entangled coherent states (MECS) using a multi-mode superconducting cavity containing an SQUID-based charge qubit. After the projective measurement of simple charge states, MECS representing nonlocal electromagnetic fields of cavity modes have been generated. Furthermore, we investigate the nonlocal properties of the generated MECS by constructing the new concurrence-like entanglement based on the Bell–Klyshko argument.

The Solar Connection of Enhanced Heavy Ion Charge States in the Interplanetary Medium: Implications for the Flux-Rope Structure of CMEs

We investigated a set of 54 interplanetary coronal mass ejection (ICME) events whose solar sources are very close to the disk center (within 15 degrees from the central meridian). The ICMEs consisted of 23 magnetic cloud (MC) events and 31 non-MC events. Our analyses suggest that the MC and non-MC ICMEs have more or less the same eruption characteristics at the Sun in terms of soft X-ray flares and CMEs. Both types have significant enhancements in charge states, although the non-MC structures have slightly lower levels of enhancement. The overall duration of charge state enhancement is also considerably smaller than that than that in MCs as derived from solar wind plasma and magnetic signatures. We find very good correlation between the Fe and O charge state measurements and the flare properties such as soft X-ray flare intensity and flare temperature for both MCs and non-MCs. These observations suggest that both MC and non-MC ICMEs are likely to have a flux-rope structure and the unfavorable observational geometry may be responsible for the appearance of non-MC structures at 1 AU. We do not find any evidence for active region expansion resulting in ICMEs lacking a flux rope structure because the mechanism of producing high charge states and the flux rope structure at the Sun is the same for MC and non-MC events.

SAMPEX to Reenter Atmosphere: Twenty‐Year Mission Will End

SAMPEX to Reenter Atmosphere: Twenty‐Year Mission Will End

Preparing arbitrary mode superconducting LC entangled coherent state via a superconducting charge qubit

We design a pure solid-device comprised by LC circuits, which are coupled to superconducting charge qubit to entangle superconducting LC coherent modes. The operation time of the state of the system does not increase with the increase of the number of LC modes. Based on the measurement of charge states, an arbitrary mode of the state can be easily generated. A brief discussion about the experimental feasibility of the scheme is also shown.

Phonon Effects on the Weak Measurement of Charge States in Quantum Dots with a Quantum Point Contact

We study theoretically the process of a weak measurement of charge states in a double quantum dotperformed bycoupling to a quantumpointcontact. Wefocus on the interplayof the measurementprocess withphonon-induced dephasing of delocalized superpositions of electron states and compare the time scales relevantforthedynamicsoftheopensystemandforthemeasurementprocess: thedecoherencerate,thelocalizationrateof the state conditioned on the measurement outcome and the time scale on which information on the systemstateisgainedintheprocessofthemeasurement.PACS:73.63.Kv,03.65.Ta,63.20.kd

CONSTRAINTS ON CORONAL MASS EJECTION EVOLUTION FROM IN SITU OBSERVATIONS OF IONIC CHARGE STATES

We present a novel procedure for deriving the physical properties of coronal mass ejections (CMEs) in the corona. Our methodology uses in situ measurements of ionic charge states of C, O, Si, and Fe in the heliosphere and interprets them in the context of a model for the early evolution of interplanetary CME (ICME) plasma, between 2 and 5 R� . We find that the data are best fit by an evolution that consists of an initial heating of the plasma, followed by an expansion that ultimately results in cooling. The heating profile is consistent with a compression of coronal plasma due to flare reconnection jets and an expansion cooling due to the ejection, as expected from the standard CME/flare model. The observed frozen-in ionic charge states reflect this time history and, therefore, provide important constraints for the heating and expansion timescales, as well as the maximum temperature the CME plasma is heated to during its eruption. Furthermore, our analysis places severe limits on the possible density of CME plasma in the corona. We discuss the implications of our results for CME models and for future analysis of ICME plasma composition.