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The POKER (POsitron resonant annihilation into dark mattER) project aims to perform a missing-energy measurement employing a ∼ 100 GeV positron beam impinging on an active thick target. The beam interaction with this detector could produce feebly interacting massive particles, exiting from it undetected and carrying away a significant fraction of the primary positron energy. The crucial element of the POKER project is a high-resolution PbWO 4 electromagnetic calorimeter employed as the active target. A prototype of this calorimeter, POKERINO, consists of a 3 × 3 matrix of PbWO 4 crystals with a SiPM-based readout system. In the summer of 2023, the POKERINO's response to high-energy particles was measured for the first time at the H8 beamline of the Super Proton Synchrotron (SPS) at CERN. This manuscript summarises the most important results obtained during the test beam of POKERINO at CERN, highlighting how this study influenced the perspectives of the POKER experimental effort. [ABSTRACT FROM AUTHOR]

For a long time the necessity of having intense positron beams to get a high rate of events with fixed targets as with e+e− collisions, led to conventional positron sources using high energy and high intensity electron beams generating bremsstrahlung photons in thick high Z targets. The inconveniences for such scheme, heat load and large emittance, are underlined. Alternative ways aiming to provide a high number of photons impinging on rather thin conversion targets have been developed: they are using magnetic undulators, laser Compton backscattering and channeling radiation in axially oriented crystals. A brief description of these methods is given. However, the emphasis is put here on the channeling radiation. The advantages of channeling radiation, described by M.Kumakhov and others, were confirmed by many simulations and experiments. We are reporting, hereafter, on two schemes: positron all-crystal converters involving thick crystals where photon radiation and e+e− pair creation are occurring in the crystal and hybrid sources where the two functions are separated. With the hybrid scheme, including a thin crystal-radiator and a thick amorphous-converter, the heat load and the local deposited energy density can be lowered. Simulations and experiments related to these two schemes are reported. Further developments concerning the converter, granular instead of bulk, are providing additional advantages. The promising, already gathered results led to consider these kinds of positron sources for future e-e+ colliders. More physicists, from different laboratories, concerned by the studies on positron sources are now contributing in this field. [ABSTRACT FROM AUTHOR]

In the study, using the Moliere, Firsov and Barrett approximations, the interaction potentials of positively charged particles channeled along the c-axes in hexagonal crystals such as Be, Mg, Sc, Ti, Co, Zn, Se, Y, Zr, Tc, Ru, Cd, Te, La are calculated at T = 300K. For the Co crystal, the Doyle – Turner approximation was additionally used. It is demonstrated that in these directions, sufficiently deep potential wells are formed. Using optimal approximation functions, energy levels and their corresponding wave functions are determined for channeled positrons with Lorentz-factors of 25, 50, 75. Using these data for positron beams with various angular dispersions, spontaneous radiation spectra are calculated for all the investigated hexagonal crystals. [ABSTRACT FROM AUTHOR]

In this work, the progress made by the positron group from ELI-NP in the design of a new slow positron beam line is summarized. The rays of a brilliant gamma beam will be used to produce a slow positron beam of high intensity. The main results of the simulations, done for the geometry optimization of the Converter/Moderator Assembly (CMA) for γ -to-slow e + conversion, are reported. By using the γ -beam with energy of up to 3.5 MeV and intensity of 2. 4 × 1 0 10 γ s − 1 , the slow e + beam can be obtained with a maximum intensity of ∼ 2 × 1 0 6 s−1 with tungsten or platinum CMA. Solid neon moderation is applicable, and a successful implementation will result in a slow e + beam of intensity > 1 0 7 s − 1. The CMA can be operated with a central hole (⌀ = 2. 5 mm) in the foils in parasitic mode, i. e. , simultaneously with other γ -beam experiments, at the cost of reduced intensity by 18%. Furthermore, details on the slow positron transport and the spectroscopic systems, which are under construction, are provided. [ABSTRACT FROM AUTHOR]

Accelerator-based searches for dark matter are aiming for high sensitivity and need an experimental setup with high luminosity. This field of research is often called intensity frontier physics. One of the best motivated portals of interaction between dark matter and ordinary matter is a dark photon which could be observed as a resonance in the invariant mass of the decay products. Electron–positron collisions are known to be the cleanest interaction for such a study. In this paper we propose a scheme for a collider which allows for a luminosity of a few orders of magnitude higher than could be obtained in a conventional symmetric collider and with a few times higher accessible mass than is possible using a positron beam and a fixed target approach. The key concept is based on asymmetric energies: a high-energy circulating positron beam and a low-energy high-intensity electron beam, and optimization of the beam interaction region. We present here a configuration of a collision region of 10 MeV electron and 4 GeV positron beams. [ABSTRACT FROM AUTHOR]

A novel method for the measurement of the number of positrons contained in intense positron bunches is presented. The technique is based on the Poisson distribution of the number of gamma rays emitted by many simultaneous positron–electron annihilations in a small solid angle. The results have been found in good agreement with those achieved with a calibrated CsI(Tl) detector coupled to a photodiode. The small dimension of the required equipment and the reduced constraints of the technique open the possibility of monitoring, in complex positrons systems, the number of positrons at different positions that are too difficult to reach with other devices. [ABSTRACT FROM AUTHOR]

Abstract: A performance test has been made for an electro-magnetic calorimeter prototype comprised four identical BSO crystals arranged in a 2×2 matrix by utilizing a positron beam in the energy range from 100 to 800MeV. The size of each crystal is 40×40×210mm3. This is the world''s largest BSO single crystal ever used as a photon detector. The obtained energy resolution is at room temperature, where E is the incident positron energy given in GeV. A BGO calorimeter having the same geometry has been employed in the performance test for comparison. The basic scintillation characteristics of BSO crystals measured without the beam are also presented. [Copyright &y& Elsevier]

The design optimization of a magnetic bottle device for high-efficiency positron moderation is described herein. The interaction between positrons and matter, including positron tracking, was performed via GEANT and COMSOL simulation. Optimization was performed for a 10 kW power supply for the excitation of two magnetic coils and were established geometry sizes of the device, namely a chamber with a radius of 100 mm and a length of 300 mm. The irradiation of a Ti foil with a thickness of 1 ÷ 10 μ m at the TR19 cyclotron for 8 h with a proton current of 10 μ A can produce 48V with an activity of 6 ÷ 60 MBq. Given such a source of fast positrons for use in the optimized magnetic bottle device, a slow positron beam intensity of 2 ÷ 10 × 104 s−1 can be achieved. [ABSTRACT FROM AUTHOR]

A positron camera, consisting of a pair of Anger-type scintillation detectors, has been developed to verify ranges by using positron emitter beams. Each detector head is equipped with a NaI(Tl) crystal (diameter: 600 mm, thickness: 30 mm) for high detection efficiency. To get a low counting rate for this application, the electric circuit was designed for flexibility in measurement and analysis by software. The energy and position were calibrated for high measurement accuracy. A spatial resolution of 8.6 mm in FWHM within a ±50 mm region (field of view) and a linear response of a 0.3 mm standard deviation within a ±200 mm region were obtained. The camera was designed so as to measure the ranges within an accuracy of 1 mm under a dose limitation (about 100 mGyE) to reduce the safety margin for the irradiation field, and it met the required characteristics. [Copyright &y& Elsevier]

Injectors and in particular the positron production systems are a crucial element in linear and circular colliders. The proposed FCC-ee injector linac accelerates both electrons and positrons up to 6 GeV in order to be injected into the Pre-Booster Ring (PBR) with a high intensity of 3.5 nC per bunch for the Z running mode. The current design baseline of the FCC-ee injector linac is based on the SuperKEKB scheme, in which the electron and the positron beams share the same linacs with a fixed target configuration on-axis hole for electron beam passage. One of the main drawbacks of this scheme is the positron production efficiency at the exit of the injector linac. In order to achieve a better performance and a higher positron yield, in this paper we study different bypass injection options. Start-to-end design and optimization for beam production, acceleration and transport from the feeding electron source to the positron damping ring are also being presented. [ABSTRACT FROM AUTHOR]

Abstract: A new in-pile -converter and Pt-moderator was recently installed at the neutron induced positron source NEPOMUC. The intensity of the moderated positron beam is unprecedented and amounts to moderated positrons per second at an energy of 1keV. Hence, the beam facility NEPOMUC provides the world highest intensity of a monoenergetic positron beam reported so far. Up to now, no degradation of the positron yield has been observed for several weeks of operation. Thus, the long-term stability of the positron beam enables experiments with high reliability. [Copyright &y& Elsevier]

QUPLAS (QUantum interferometry and gravitation with Positrons and LASers) is an experimental project for the study of antimatter; it makes use of positrons and positronium and mainly aims at performing quantum interferometry, decoherence and gravitational studies. The first phase of the project, called QUPLAS-0, consisted in the first successful demonstration of quantum interference of an antimatter particle: the positron. The experimental apparatus is composed by the positron beam, the interferometer, and the detector. This paper describes these three elements of QUPLAS-0 and how they were combined to achieve the goal of positron interference. [ABSTRACT FROM AUTHOR]