Positron Beam Research Articles

Scientific explanation of e+ and Weyl fermion for injecting semiconductor devices

The scientific explanation of utilizing the positron and Weyl fermion in semiconductors is presented. In view of the slow e+ beam-generation development for imaging technology alongside the Weyl fermion which carries charge like an electron, but has no mass, thus moves much faster, injecting semiconductor devices is addressed. The information gained from this prediction has allowed the broadening of its implementation to semiconductor technology with electronic excitation using sources other than e-. Developing the positron microbeam and Weyl fermions can be described with the concept of type I positron beam source is an alternative source of electron beam, thus harnessing the generation of γ-ray radiations inside the semiconductor heterostructures with indicating e+ and e− interaction with materials are different and type II Weyl fermions. Thus, the properties of positrons and Weyl fermion are considered suitable for carrier transport in optoelectronics. Perspectives of the development of alternative beam source for super-transport are provided.

Nonlinear Ion-Acoustic Solitary Waves in a Weakly Relativistic Electron-Positron-Ion Plasma with Relativistic Electron and Positron Beams

In this investigation, compressive and rarefactive solitons are demonstrated to exist in a plasma model that includes unmagnetized weak-relativistic positive ions, negative ions, electrons, electron beam and positron beam. For these weakly relativistic non-linear ion-acoustic waves in unmagnetized plasma with electron inertia and relativistic beam, the existence of compressive and rarefactive soliton is investigated by deriving the Korteweg-de Vries (KdV) equation. It has been observed that the amplitude and width of compressive and rarefactive solitons vary differently in response to pressure variation and the presence of electron inertia. The research determines the requirements that must be met for the existence of the nonlinear ion-acoustic solitons. The fluid equations of motion governing the one-dimensional plasma serve as the foundation for the analysis. Various relational forms of the strength parameter (ε) are chosen to stretch the space and time variables, leading to a variety of nonlinearities. The findings can have implications not only for astrophysical plasmas but also for inertial confinement fusion plasmas.

Measurement of the Spin Polarization of a Slow Positron Beam Using Circularly Polarized Microwave Radiation.

We have measured the spin polarization of a slow positron beam via state-selective depopulation of 2^{3}S_{1} positronium atoms, generated by passing the beam through a gas cell. Our method employs circularly polarized microwave radiation to drive 2^{3}S_{1}→2^{3}P_{1} transitions, for which either Δm_{J}=+1 or Δm_{J}=-1, and relies on the fact that asymmetries between the two cases yield the underlying positron beam polarization. Using this technique we show that the polarization of a positron beam derived from a solid neon moderator may be increased from 30% to 90% by increasing the moderator thickness, with an associated reduction in beam intensity of 60%.

Monte Carlo simulations towards the formation of a positronium coherent beam

Positronium (Ps) has emerged as a promising test particle within the QUantum interferometry with Positrons, positronium and LASers (QUPLAS) project, which aims to measure for the first time the gravitational effect on Ps, the entirely leptonic atom comprising an electron and a positron. In this work, we present a Monte Carlo simulation to generate a mono-energetic and highly coherent Ps beam by creating a negative Ps ion (Ps− consisting of two electrons and one positron) to be used in a Mach–Zehnder interferometer. We propose the equations to estimate the initial velocity distributions in the longitudinal and transversal directions of the Ps− emitted from the target converter (positron/Ps−) necessary for the Monte Carlo simulation. The resulting simulated device needs a very low divergence Ps beam at the interferometer entrance, for this reason an intensive positron beam is necessary, such as a high-flux electron LINAC. Subsequently, we utilize a Fabry–Perot IR laser cavity operating in CW at a wavelength of 1560 nm to selectively remove the extra electron. An alternative pulsed laser operating at a 3600 nm wavelength was studied to reduce broadening due to recoil and excitation. Here, we provide a Monte Carlo simulation to estimate the characteristics of the Ps beam, including its energy distribution and intensity profiles at two different temperatures (10 K and 300 K). Despite the limitations given by the assumptions mentioned in the text within the limit of our knowledge, these first simulation results obtained from our study will provide essential groundwork for future advancements in fundamental particles gravity measurements.

Impact of relativistic positron beam on ion-acoustic solitary, periodic and breather waves in Earths’ ionospheric region through the framework of KdV and modified KdV equation

Abstract This study explores the propagation characteristics of ion-acoustic periodic, soliton, and breather waves in electron-positron-ion (EPI) plasma with a relativistic positron beam. The Korteweg–de Vries (KdV) equation is obtained by applying the traditional reductive perturbation method (RPM) to the fundamental set of fluid equations. When the KdV model is unable to accurately represent the nonlinear system’s evolution, a modified Korteweg–de Vries (mKdV) equation is constructed. In both models, Jacobi elliptic functions are used to derive periodic solutions, and a connection between periodic waves and soliton solutions is established. Hirota’s bilinear method is used to generate breathers directly from the KdV type framework without utilizing the modified Schrödinger framework inferred from the KdV type framework, which is a prevalent method in studies of nonlinear waves. Numerical knowledge of various physical factors in the ionospheric region is incorporated into the model to elucidate wave propagation in the Earth’s upper atmosphere.

Surface and near-surface positron annihilation spectroscopy at very low positron energy

We present a monoenergetic positron beam specifically tailored to the needs of (near-) surface positron annihilation spectroscopy. The Setup for LOw-energy Positron Experiments (SLOPE) comprises a high-activity 22Na source, a tungsten moderator, electrostatic extraction and acceleration, magnetic beam guidance, as well as an analysis chamber with a movable sample holder and a γ-ray detection system. The tungsten moderator foil, biased between 0 and 30 V, in combination with the HV-biasable sample holder, enables positron implantation energies between 3 eV and 40 keV. At low energies (< 20 eV), the count rate typically amounts to 4400 counts per second, and the beam diameter is smaller than (12±3) mm. We conduct phase space simulations of the positron beam using COMSOL Multiphysics® to characterize the beam properties and compare the findings with the experimentally determined energy-dependent beam diameter. To showcase the capabilities of SLOPE, we perform studies of positronium (Ps) formation on boehmite and depth-resolved coincidence Doppler-broadening spectroscopy (CDBS) of copper. In particular, the Ps formation at the hydrogen-terminated surface of boehmite is found to be maximum at a positron implantation energy of 10 eV. The range of positron energies for which we observe Ps formation agrees with the hydrogen ionization energy.

POSITRON SOURCES OF THE MULTIFUNCTIONAL ACCELERATOR COMPLEX OF NSC KIPT

The possibility of producing positron beams using an electron recycler, the conceptual design of which is being developed at KIPT, is considered. The positron flux after the tantalum converter was estimated. The efficiency of the process of injection and acceleration of positrons to 181 and 356 MeV for high-energy physics experiments was calculated. The characteristics of the beam for use in structural studies of solid state physics are considered.

Experimental Demonstration of an Emittance-Preserving Beam Energy Dechirper Using a Hollow Channel Plasma.

Plasma-based acceleration has emerged as a highly promising candidate for future colliders and compact x-ray free electron lasers owing to its capability to efficiently accelerate electron and positron beams with high brightness over short distances. However, a major obstacle to its application in free electron lasers and colliders is the imposition of a substantial energy chirp on the output beams, resulting from the longitudinally dependent acceleration field. This Letter presents the first experimental demonstration of a beam energy dechirper using a hollow plasma channel. This novel approach simultaneously enables the mitigation of energy chirp and preservation of beam emittance. Experimental results demonstrate a substantial reduction in energy spread by nearly 1 order of magnitude (from 0.93% to 0.11% FWHM), while maintaining a negligible increase in emittance. Simulation suggests that the corrected energy spread may have been reduced to ∼10 keV (0.025%), thereby meeting the stringent requirement of colliders or x-ray free electron lasers.

Measurement of the fractional radiation length of a pixel module for the CMS Phase-2 upgrade via the multiple scattering of positrons

High-luminosity particle collider experiments such as the ones planned at the High-Luminosity Large Hadron Collider require ever-greater vertexing precision of the tracking detectors, necessitating reductions in the material budget of the detectors. Traditionally, the fractional radiation length (x/X 0) of detectors is either estimated using known properties of the constituent materials, or measured in dedicated runs of the final detector. In this paper, we present a method of direct measurement of the material budget of a CMS prototype module designed for the Phase-2 upgrade of the CMS detector using a 40–65 MeV positron beam. A total of 630 million events were collected at the Paul Scherrer Institut PiE1 experimental area using a three-plane telescope consisting of the prototype module as the central plane, surrounded by two MALTA monolithic pixel detectors. Fractional radiation lengths were extracted from scattering angle distributions using the Highland approximation for multiple scattering. A statistical technique recovered runs suffering from trigger desynchronisation, and several corrections were introduced to compensate for local inefficiencies related to geometric and beam shape constraints. Two regions of the module were surveyed and yielded average x/X 0 values of (0.72 ± 0.05)% and (0.95 ± 0.09)%, which are compatible with empirical estimates for these regions computed from known material properties of 0.753% and 0.892%, respectively. Two types of higher-granularity maps of the fractional radiation length were produced, subdivided either into rectangular regions of uniform size, or polygonal-shaped regions of uniform material composition. The results bode well for the CMS Phase-2 upgrade modules, which will play a key role in the minimisation of the material of the upgraded detector.

Surface Microstructure Study on Corona Discharge-Treated Polyethylene Using Positron Annihilation Spectroscopy.

The microstructure and chemical properties of the corona discharge process could provide an effective method for predicting the performance of high-voltage cable insulation materials. In this work, the depth profile of the microstructure and chemical characteristics of corona discharge-treated PE were extensively investigated using Doppler broadening of position annihilation spectroscopy accompanied with positron annihilation lifetime spectroscopy, attenuated total reflectance Fourier transform infrared spectra, Raman spectra and contact angle measurement. By increasing corona discharge duration, the oxygen-containing polar groups, including hydroxyl, carbonyl and ester groups, strongly contribute to the deterioration of hydrophobicity and the enhancement of hydrophilicity. And the mean free volume size, with a broadening distribution, decreases slightly. The line shape S parameter decreases because of the decrease in free volume elements and the appearance of oxygen-containing groups. Also, the thickness of the degradation layer, determined from the S parameter with positron injection depth, increases and diffuses into the PE matrix. A linear S-W plot within the degradation layer of different corona treatment duration samples indicates the defect type does not change. The S parameter decreases and the W parameter increases with an increasing corona duration. Using a slow positron beam, the nondestructive probe can be used to profile the microstructure and chemical environment across the corona discharge damage depth, which is beneficial for investigating the surface and interfacial insulation materials.

Characterization of the PADME positron beam for the X17 measurement

This paper presents a detailed characterization of the positron beam delivered by the Beam Test Facility at Laboratori Nazionali of Frascati to the PADME experiment during Run III, which took place from October to December 2022. It showcases the methodology used to measure the main beam parameters such as the position in space, the absolute momentum scale, the beam energy spread, and its intensity through a combination of data analysis and Monte Carlo simulations. The results achieved include an absolute precision in the momentum of the beam to within ~1–2 MeV/c, a relative beam energy spread below 0.25%, and an absolute precision in the intensity of the beam at the level of 2%.

Simulation of deflection and photon emission of ultra-relativistic electrons and positrons in a quasi-mosaic bent silicon crystal

Abstract A comprehensive numerical investigation has been conducted on the angular distribution and spectrum of radiation emitted by 855 MeV electron and positron beams while traversing a ‘quasi-mosaic’ bent silicon (111) crystal. This interaction of charged particles with a bent crystal gives rise to various phenomena such as channeling, dechanneling, volume reflection, and volume capture. The crystal’s geometry, emittance of the collimated particle beams, as well as their alignment with respect to the crystal, have been taken into account as they are essential for an accurate quantitative description of the processes. The simulations have been performed using a specialized relativistic molecular dynamics module implemented in the MBN Explorer package. The angular distribution of the particles after traversing the crystal has been calculated for beams of different emittances as well as for different anticlastic curvatures of the bent crystals. For the electron beam, the angular distributions of the deflected particles and the spectrum of radiation obtained in the simulations are compared with the experimental data collected at the Mainz Microtron facility. For the positron beam such calculations have been performed for the first time. We predict significant differences in the angular distributions and the radiation spectra for positrons versus electrons.&amp;#xD;

Injection and confinement of positron bunches in a magnetic dipole trap.

We demonstrate the efficient injection of a pulsed positron beam into a magnetic dipole trap and investigate the ensuing particle dynamics in the inhomogeneous electric and magnetic fields. Bunches of ∼10^{5}e^{+} were transferred from a buffer-gas trap into the field of a permanent magnet using a lossless E×B drift technique. The Δt≈0.2µs pulses were short compared to the toroidal rotation period, τ_{d}≈16µs, and e^{+} confinement time, τ_{c}≈0.6s. The redistribution dynamics were studied by measuring the delayed γ-ray emission as the trap was emptied. This work extends the record for the number of low-energy positrons held in a dipole trap by two orders of magnitude and represents a significant advance toward the confinement of an electron-positron pair plasma.

Single-pixel positron beam diagnosis via compressive sampling.

The morphology is a crucial indicator for diagnosing a low-energy, low-brightness particle beam. However, conventional positron beam diagnosis, based on the pixel scanning principle, is limited by physical constraints, such as the resolution of detector pixels. Here, we have presented a novel slow positron diagnosis method using compressive sampling. With a 100 × 100 pixel-sized mask, for example, the positron beam morphology can be significantly reconstructed with a peak signal-to-noise ratio of ∼40 dB, even at half the sampling rate compared to pixel scanning. It explores a promising approach for positron beam diagnosis with an ultra-high resolution and fast sampling rates.

Annealing behaviors of open spaces and gas desorption in chemical vapor deposited SiO2 studied with monoenergetic positron beams

The annealing properties of open spaces in 90-nm-thick SiO2 deposited from tetraethylorthosilicate (TEOS) using plasma-enhanced chemical vapor deposition (PECVD) were studied with monoenergetic positron beams. From the lifetime of positronium (Ps) and an empirical model assuming a spherical open space, the mean diameter of open spaces was estimated to be 0.45 nm for PECVD-SiO2 before annealing. In the annealing temperature range below 350 °C, the size of the open spaces and their concentration increased as the temperature increased. Because initial water desorption from PECVD-SiO2 occurred in this temperature range, the observed increases in the size and concentration of spaces were attributed to the detrapping of water from such regions. Above 400 °C annealing, Ps formation was suppressed due to carrier traps introduced by the desorption of gas incorporated during TEOS decomposition. The size of the open spaces reached its maximum value (0.61 nm) after 800 °C annealing and started to decrease above 900 °C. After 1000 °C annealing, although the size of the spaces was close to that in thermally grown SiO2, their concentration remained low, which was attributed to residual impurities in the SiO2 network.

Vacancy-Type Defects and Oxygen Incorporation in NiAl for Advanced Interconnects Probed by Monoenergetic Positron Beams and Atom Probe Tomography

Vacancy-Type Defects and Oxygen Incorporation in NiAl for Advanced Interconnects Probed by Monoenergetic Positron Beams and Atom Probe Tomography

Application of AI Models for Determination of Beam Parameters with an Array of Timepix3 Pixel Detectors

Abstract PADME Run III searched for a resonant production of the X17 particle. The precise knowledge of the beam position is critical for the measurements of X17 and an array of 2 × 6 Timepix3 hybrid pixel detectors were used to measure the parameters of the incident positron beam. During the operation of the Timepix detector, some of the pixels reported missing data which introduced a challenge for the accurate estimation of the center position. A Neural Network Regression algorithm was developed and compared with the conventional Gaussian fitting technique over a simulated data with masked pixels.

In-grown and irradiation-induced Al and N vacancies in 100 keV H+ implanted AlN single crystals

We report positron annihilation results on in-grown and proton-irradiation-induced vacancy defects in AlN single crystals grown by physical vapor transport. The samples were irradiated with 100 keV H+ ions to varying fluences in the range of 5 × 1014 − 2 × 1018 ions cm–2. Doppler broadening of annihilation radiation was recorded in as-grown and irradiated samples with a slow positron beam with varying implantation energy. Doppler results combined with first principles theoretical calculations show that the 100 keV H+ irradiation introduces isolated VAl on the ion track and VN-rich vacancy clusters at the end of the ion range. The results suggest that the excess amount of detected VN originates from a high concentration of in-grown VN. So far, these defects have been considered to be unidentified negative ion-like defects in AlN.

Defect dynamics studies during heat treatments in plastically deformed metals predicted for nuclear applications

We report on defects dynamics during heat treatment in plastically deformed metallic materials using positron annihilation lifetime spectroscopy carried out on the intense pulsed positron beam. The conducted experiment allowed us to observe the changes in the concentration and sizes of vacancy-like defects observed during in situ annealing. We monitored heat treatments up to 300 °C in hydrostatic extruded Ti and cavitation peened V–4Cr–4Ti alloy. We were able to track the recovery processes in Ti and redistribution of large voids at the surface of cavitation peened V–4Cr–4Ti alloy. The relaxation time during recovery was about 20 min. Performed experiments show that in cold-worked metallic materials significant changes in vacancy clusters concentrations occur at mildly elevated temperatures. The presented results give opportunity to the application of in situ observation of defects dynamic to similar problems related to thermomechanical processing of metallic materials.Graphical abstract

Dense Polarized Positrons from Beam-Solid Interaction.

Relativistic positron sources with high spin polarization have important applications in nuclear and particle physics and many frontier fields. However, it is challenging to produce dense polarized positrons. Here we present a simple and effective method to achieve such a positron source by directly impinging a relativistic high-density electron beam on the surface of a solid target. During the interaction, a strong return current of plasma electrons is induced and subsequently asymmetric quasistatic magnetic fields as high as megatesla are generated along the target surface. This gives rise to strong radiative spin flips and multiphoton processes, thus leading to efficient generation of copious polarized positrons. With three-dimensional particle-in-cell simulations, we demonstrate the production of a dense highly polarized multi-GeV positron beam with an average spin polarization above 40% and nC-scale charge per shot. This offers a novel route for the studies of laserless strong-field quantum electrodynamics physics and for the development of high-energy polarized positron sources.