Cylindrical Penning Trap Research Articles

Temporal evolution of electron cloud in a cylindrical Penning trap at room temperature.

The temporal evolution of the electron cloud at room temperature has been recorded through a resonance circuit by observing the axial oscillation frequency of its center of mass. The electron cloud undergoes radial expansion by interacting with the residual gas molecules, and it is finally lost upon hitting the Penning trap electrodes. It has been confirmed through detailed experimental investigations that the unique temporal pattern of frequency variation is a consequence of the cloud's radial expansion. Consequently, this approach offers a non-destructive means for single-shot detection, enabling continuous monitoring of the electron cloud's radial expansion during the confinement time. This technique offers a significant advantage over its destructive alternatives.

Design and simulations for a Penning Ion Trap Source for the CHIP-TRAP Mass Spectrometer

At Central Michigan University (CMU) we have been developing the CMU High Precision Penning Trap (CHIP-TRAP) mass spectrometer for precise mass measurements on stable and long-lived radioactive isotopes. As part of this apparatus, we have designed a Penning Ion Trap (PIT) source to produce singly-charged, low intensity (∼100s to 1000s of ions in ∼1 μs duration) ion pulses from gaseous samples. The PIT source is similar to a PIG type source, composed of an electric field superimposed on a magnetic field. The electric field is produced by a cylindrical Penning trap structure consisting of two end caps and a center ring with a trap volume of about 0.8 cm3. The trap structure is housed inside a permanent neodymium ring magnet bore. Gas is inserted into the trapping region and ionized by an ∼1 μA electron beam from a thermal emitter. Ions are extracted from the PIT source by lowering the voltage on one of the end caps. They are then accelerated into the beam line. In this paper, we report on the design of the PIT source and simulations to investigate and characterize the expected beam properties.

The TAMUTRAP facility: A Penning trap facility at Texas A&M University for weak interaction studies

The Texas A&M University Penning Trap (TAMUTRAP) facility aims to test the standard model of the electroweak interaction by measuring the β-ν correlation parameter, aβν, for β-delayed proton emitters in the atomic mass range 20 < A < 40. Precision measurements of this correlation parameter and, inextricably, the Fierz interference parameter, are a sensitive probe of physics beyond the standard model. Using off-line ion sources, the TAMUTRAP facility has been commissioned by demonstrating the ability to manipulate the trapped-ion motions as well as to perform precision mass measurements. Our novel cylindrical Penning trap – the world's largest – differs from typical designs in two key aspects: the electrode structure has an 180-mm inner diameter and an overall length of 334.89 mm leading to a uniquely small length/radius ratio l/r = 3.72; and we do not use the long end cap approximation, instead our short endcap electrodes are closed and capable of being placed at an arbitrary potential. This geometry is optimized for observing β-delayed proton decays, but is also well suited for other in-trap and post-trap precision decay experiments. In addition to presenting an overview of the TAMUTRAP facility, we demonstrate that our unique Penning trap is able to measure masses with a precision similar to typical trap designs.

Design and characterization of Ion sources for CHIP-TRAP

At Central Michigan University, we are developing a high-precision Penning trap mass spectrometer (CHIP-TRAP) for precise mass measurements with stable and long-lived isotopes. Ions will be produced using external ion sources and then transported to the Penning trap at low energy using electrostatic ion optics. Ion sources that will be utilized with CHIP-TRAP include a laser ablation ion source (LAS) that has already been commissioned, and a low current Penning ion trap (PIT) source that is currently being developed. The LAS enables ion production from solid targets via ablation and ionization with a high-powered laser pulse. The PIT source is a novel Penning ionization gauge (PIG) type source, consisting of a 0.55 T NdFeB ring magnet, cylindrical Penning trap, and low current thermal electron emitter that enables ion production via electron impact ionization of gaseous samples. For both ion sources, small bunches of ∼100 – 1000 ions can be produced from a minimal sample of source material. The ion bunches are then transported along the CHIP-TRAP beamline, where time-of-flight mass filtering can be performed before they are captured in the CHIP-TRAP Penning traps.

Properties of a cylindrical Penning trap with conical endcap openings

We describe the results of analytical calculations and numerical simulations of the confinement properties of a mechanically compensated cylindrical Penning trap which has conical endcap openings for large-solid-angle access for example with highly focused laser beams. While the analytical calculations show that under the common geometrical conditions the harmonicity of the confining fields near the centre of the trap does not change when a conical shape of the endcap electrodes is introduced, numerical simulations show significant changes when the opening angle of the cone exceeds a certain critical angle. We also show that these sharp features are due to the fringe-field effects above the critical angle, which are not described by the analytical calculations. These effects are also observed in a cylindrical Penning trap when the length of the endcap electrodes is reduced below a certain critical value.

TAMUTRAP facility: Penning trap facility for weak interaction studies

In the low-energy regime, precision measurements in nuclear β −decay continue to be a sensitive tool to search for new physics beyond the standard model (SM). The primary goal of the Texas A&M University Penning trap facility (TAMUTRAP) is to improve the limits on non-SM processes in the weak interaction. In particular, scalar currents, by measuring the β − ν angular correlation parameter (aβν), for T = 2, super-allowed β −delayed proton emitters. The precise measurement of energy Doppler shift of the proton following β+ −decay is sensitive to β − ν angular correlation coefficient, which is unity (aβν= 1) for pure Fermi transition in the absence of scalar currents. The experiments will be performed in a unique large bore cylindrical Penning trap with an inner radius of 90 mm, which is larger than any existing Penning trap across the world. The TAMUTRAP facility has been commissioned off-line and has demonstrated the ability to perform high precision mass measurements. We describe here the facility overview and summarize the current status towards the first measurement of β − ν angular correlation for T = 2, beta delayed proton emitters using a large bore cylindrical Penning trap with closed end caps.

Thermo-statistical study of evaporation effects in a non neutral plasma under an imperfect magnetic confinement

Experimental studies of non-neutral plasmas in magnetic traps undergo, in some degree of affectation, the incidence of evaporation. For example, the existence of a finite threshold energy for the escaping of plasma constituents can be favored by the external electrostatic forces near the grounded conducting walls of a cylindrical Penning trap. In contrast, the conventional statistical mechanics description of these situations is performed assuming the existence of a rigorous thermodynamic equilibrium (Dubin and O’Neil 1999 Rev. Mod. Phys. 71 87), dismissing thus the existence of evaporation effects. We propose in this work a two-dimensional toy model that describes the incidence of evaporation on thermo-statistics of a pure non-neutral plasma (a system composed of a single charge species like an infinitely long electron column). Considering the existing connections between the macroscopic descriptions of pure non-neutral plasmas and astrophysical systems, the treatment of evaporation along a quasi-stationary regime is developed here in analogy to some astrophysical models proposed in the literature. We start from a regularized microcanonical description that only considers those microscopic configurations where particles are trapped inside a confinement region of radius Rc, which is implemented introducing a truncation of their velocity spectrum. These arguments lead us to a statistical procedure to predict the quasi-stationary particles distribution similar to the maximum entropy approach. According to our analysis, the influence of evaporation for a non-zero temperature T crucially depends on the saturation parameter , whose admissible values are located in the interval , with rB being the radius of Billouin steady state that appears in the limit . The theoretical profiles predicted from this model are then compared to the metastable radial density distribution reported by Huang and Driscoll (1993 Phys. Rev. Lett. 72 2187). This analysis suggests the effects of evaporation in this particular experiment are significant, being these data compatible with the range of values –0.59. To reach a major understanding of this experiment, we analyze the relation between our development and the so-called minimum enstrophy approach, which was invoked by these authors to fit their experimental data. We show that a variant of differential equation for particle density compatible with this extremal principle appears as an asymptotic case of the present proposal.

Non-destructive single-pass low-noise detection of ions in a beamline.

We have conceived, built, and operated a device for the non-destructive single-pass detection of charged particles in a beamline. The detector is based on the non-resonant pick-up and subsequent low-noise amplification of the image charges induced in a cylindrical electrode surrounding the particles' beam path. The first stage of the amplification electronics is designed to be operated from room temperature down to liquid helium temperature. The device represents a non-destructive charge counter as well as a sensitive timing circuit. We present the concept and design details of the device. We have characterized its performance and show measurements with low-energy highly charged ions (such as Ar(13+)) passing through one of the electrodes of a cylindrical Penning trap. This work demonstrates a novel approach of non-destructive, low noise detection of charged particles which is, depending on the bunch structure, suitable, e.g., for ion traps, low-energy beamlines or accelerator transfer sections.

Status of the TAMUTRAP facility and initial characterization of the RFQ cooler/buncher

The Texas A&M University Penning Trap experiment (TAMUTRAP) is an upcoming ion trap facility that will be used to search for possible scalar currents in T = 2 superallowed pure Fermi decays (utilizing β-delayed proton emitters), which, if found, would be an indication of physics beyond the standard model. In addition, TAMUTRAP will provide a low-energy, point-like source of ions for various other applications at the Cyclotron Institute at Texas A&M University. The experiment is centered around a unique, compensated cylindrical Penning trap that employs a specially optimized length/radius ratio in the electrode structure that is not used by any other facility. The radioactive beam, provided by the Texas A&M University Re-accelerated Exotics (T-REX) program at the Cyclotron Institute, will be prepared for loading in the measurement trap via a specially designed Radio Frequency Quadrupole (RFQ) cooler/buncher. These proceedings will describe the current status of the TAMUTRAP facility, paying particular attention to the design and initial characterization of the RFQ cooler/buncher. Future plans will also be discussed.

Toward sub-Kelvin resistive cooling and non destructive detection of trapped non-neutral electron plasma

A resonant circuit tuned to a particular frequency of the motion of charged particles stored in a Penning trap and connected to a low noise amplifier allows, at the same time, cooling and non destructive detection of the particles. Its use is widely diffused when single or few particles are stored near the centre of a hyperbolic Penning trap. We present a consistent model that predicts the shape of the induced signal when the tuned circuit is used to detect and cool the axial motion of a cold non neutral plasma stored in an open-ended cylindrical Penning trap. The model correctly accounts for the not negligible axial plasma size. We show that the power spectrum of the signal measured across the tuned circuit provides information about the particle number and insights about the plasma temperature. We report on the design of a HEMT-based cryogenic amplifier working at 14.4 MHz and 4.2 K and the results of the noise measurements. We have measured a drain current noise in the range from 6 to 17 pA/√Hz, which corresponds to an increase of the tuned circuit equivalent temperature of at maximum 0.35 K. The cryogenic amplifier has a very low power consumption from few tens to few hundreds of μW corresponding to a drain current in the range 100–800 μ A. An additional contribution due to the gate noise has been identified when the drain current is below 300 μA; above that value an upper limit of the increase of the equivalent tuned circuit temperature due to this contribution of 0.02 K has been obtained. These features make the tuned circuit connected to this amplifier a promising device for detecting and cooling the axial motion of an electron plasma when the Penning trap is mounted inside a dilution refrigerator.

Evaporative cooling of hydrogen molecular ions in a Penning trap

Evaporative cooling of singly charged ions in a Penning trap is studied. The ions are created by in-situ electron bombardment of hydrogen molecules and trapped in a cylindrical Penning trap. Cooling of the ions is observed by their axial motion after trapping of a few hundred milliseconds. The ions temperature decreases by a factor of more than 6 in 800 ms, while the bunch density of the coldest ions increases by up to a factor of 10. By studying the time constants of the dependence of ion loss and axial temperature on the magnetic field strength, we exclude the effects of ions loss through the cyclotron motion on the axial ion temperature.

Upgrades at ClusterTrap and latest results

For the last decade the production of polyanionic metal clusters in the gas phase and the investigation of their size- and charge-state dependent properties was the main objective of the ClusterTrap experiment. An upgrading of the ion-trapping devices extends the range of anionic charge states: a recently installed Penning trap with a 12-T superconducting magnet provides an increased mass and thus cluster-size range, crucial to reach higher anionic charge states by means of the electron-bath method. Its cylindrical Penning trap is characterized and compared with respect to the previous asymptotically hyperbolical setup. In addition, polyanionic cluster production in a linear radio-frequency quadrupole (RFQ) trap has been initiated. Preliminary results for gold-cluster polyanion production in the new Penning trap, the RFQ trap, as well as the combined use of these traps are presented.

Half-open Penning trap with efficient light collection for precision laser spectroscopy of highly charged ions

We have conceived, built and operated a ’half-open’ cylindrical Penning trap for the confinement and laser spectroscopy of highly charged ions. This trap allows fluorescence detection employing a solid angle which is about one order of magnitude larger than in conventional cylindrical Penning traps. At the same time, the desired electrostatic and magnetostatic properties of a closed-endcap cylindrical Penning trap are preserved in this configuration. We give a detailed account on the design and confinement properties, a characterization of the trap and show first results of light collection with in-trap produced highly charged ions.

Design of a unique open-geometry cylindrical Penning trap

The Texas A&M University Penning trap facility is an ion trap system currently under construction, and will be used for precision nuclear physics experiments with radioactive beams provided by the Cyclotron Institute. Its primary focus is to carry out experiments to search for possible scalar currents in T=2 superallowed β-delayed proton decays, which, if found, would be an indication of physics beyond the standard model. In addition, TAMUTRAP will provide a low-energy, spatially localized source of ions for various other applications. The experiment is centered around a unique, compensated cylindrical Penning trap that employs a specially optimized length/radius ratio in the electrode structure that is not used by any other facility. This allows the electrode structure to exhibit an unprecedented 90mm inner radius, which is larger than in any existing trap, while at the same time remaining a tractable overall length. The trap geometry was designed from first principles to be suitable for a wide range of nuclear physics experiments. In particular, the electrode structure allows for a near quadrupole electric field at the trap center, a feature necessary for performing precision mass measurements.

Model calculation of amplitudes for FT-ICR ion detection in a cylindrical Penning trap

A Green’s function strategy first proposed by Grosshans et al. is used to calculate the electric charges induced by trapped ions on the 4-fold or 8-fold segmented ring electrode of a cylindrical Penning trap. The ions are assumed to move in the central region of the trap where the harmonic approximation holds. The electric charges induced on each detection segment of the ring electrode are obtained in the form of a triple Fourier series with coefficients that describe the contribution of each frequency combination m+ν++m−ν−+mzνz as a function of R+, R−, Z, where ν+, ν−, νz are the characteristic frequencies and R+, R−, Z the corresponding amplitudes of the ion motion. The sideband structure is analyzed and the origin of the sidebands is tracked. Finally, single-electrode, differential, and additive detection are discussed.

GFactor of HydrogenlikeSi13+28

We determined the experimental value of the g factor of the electron bound in hydrogenlike ²⁸Si¹³⁺ by using a single ion confined in a cylindrical Penning trap. From the ratio of the ion's cyclotron frequency and the induced spin flip frequency, we obtain g = 1.995 348 958 7(5)(3)(8). It is in excellent agreement with the state-of-the-art theoretical value of 1.995 348 958 0(17), which includes QED contributions up to the two-loop level of the order of (Zα)² and (Zα)⁴ and represents a stringent test of bound-state quantum electrodynamics calculations.

Design of a Superconducting Magnet System for the AEGIS Experiment at CERN

The new AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) Experiment will be installed in the Antiproton Decelerator hall at CERN. The main goal is to measure the Earth's gravitational acceleration of antihydrogen atoms. The experiment consists of two high-homogeneity solenoids placed on the same axis. The 5 T magnet is part of a cylindrical Penning trap to catch and to accumulate antiprotons delivered by the decelerator. The antihydrogen is then produced in the 1 T region where sub-kelvin antiproton temperatures provided by the dilution refrigerator are required to form a slowly-moving beam of antihydrogen. The helium bath cooled superconducting magnets; the different traps and the dilution refrigerator are integrated in a common cryostat with an internal vacuum barrier between the insulating cryogenic vacuum and the very high beam vacuum. In addition, the magnet system has to guarantee a smooth transition between the 5 T and the 1 T magnetic field areas required for a loss-free transfer of antiprotons and positrons from the trapping region to the antihydrogen production area. In this paper the design of this AEGIS magnet system is presented and discussed.

Dipolar and quadrupolar detection using an FT-ICR MS setup at the MPIK Heidelberg

Dipolar and single-phase two-electrode quadrupolar detection schemes have been investigated at a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) setup built for the KATRIN experiment at the Max-Planck-Institute for Nuclear Physics (MPIK) in Heidelberg. We present first experimental results of 7Li + signals from a cylindrical Penning trap configuration for both detection schemes. While the prominent signal of the conventional dipolar detection scheme marks the reduced cyclotron frequency, the main signal for the quadrupolar detection appears at the sum of the reduced cyclotron frequency and the magnetron frequency. For ideal trapping fields, this sum frequency equals the ion cyclotron frequency ν c = qB/(2πm). Sidebands due to the combined motions of the cyclotron mode and magnetron mode are observed by quadrupolar detection which allows the determination of the respective combinations of eigenfrequencies.

Initial Experimental Characterization of a New Ultra-High Resolution FTICR Cell with Dynamic Harmonization

A new Fourier transform ion cyclotron resonance (FTICR) cell based on completely new principles of formation of the effective electric potential distribution in Penning type traps, Boldin and Nikolaev (Proceedings of the 58th ASMS Conference, 2010), Boldin and Nikolaev (Rapid Commun Mass Spectrom 25:122-126, 2011) is constructed and tested experimentally. Its operation is based on the concept of electric potential space-averaging via charged particle cyclotron motion. Such an averaging process permits an effective electric force distribution in the entire volume of a cylindrical Penning trap to be equal to its distribution in the field created by hyperbolic electrodes in an ideal Penning trap. The excitation and detection electrodes of this new cell are shaped for generating a quadratic dependence on axial coordinates of an averaged (along cyclotron motion orbit) electric potential at any radius of the cyclotron motion. These electrodes together with the trapping segments form a cylindrical surface like in a conventional cylindrical cell. In excitation mode this cell being elongated behaves almost like an open cylindrical cell of the same length. It is more effective in ion motion harmonization at larger cyclotron radii than a Gabrielse et al.-type (Int J Mass Spectrom Ion Processes 88:319-332, 1989) cylindrical cell with four compensation sections. A mass resolving power of more than twenty millions of reserpine (m/z 609) and more than one million of highly charged BSA molecular ions (m/z 1357) has been obtained in a 7T magnetic field.

Bound electron g-factor measurement by double-resonance spectroscopy on a fine-structure transitionThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.

Precise determination of bound-electron g-factors in highly charged ions provides stringent tests for state of the art theoretical calculations. The scope reaches from relativistic electron-correlation effects on the one hand to bound-state QED terms on the other. Besides, the investigation can contribute to the determination of the fine-structure constant α. In a first approach with boron-like ions of spinless nuclei (e.g., 40Ar13+ and 40Ca15+), we will excite the 22P1/2 – 22P3/2 fine-structure transition with laser radiation and probe microwave transitions between Zeeman sublevels. From this laser-microwave double-resonance technique the g-factor can be determined on a ppb level of accuracy. We have prepared a cryogenic trap assembly with a creation trap and a spectroscopy trap — a half-open compensated cylindrical Penning trap. Argon gas will be injected through a remotely controlled valve, working at cryogenic temperature and in the field of a superconducting magnet. Ions are produced by electron impact ionization and transferred to the spectroscopy trap. In the future, the trap will be connected to the HITRAP facility at GSI, and the method will be applied to hyperfine-structure transitions of hydrogen-like heavy ions to measure electronic and nuclear magnetic moments. We present important techniques employed in the experiment.