A multi-stop time-of-flight spectrometer for the measurement of positron annihilation-induced electrons in coincidence with the Doppler-shifted annihilation gamma photon
V. A. Chirayath, R. W. Gladen, A. D. McDonald, A. J. Fairchild, P. V. Joglekar, S. Satyal, Z. H. Lim, T. N. Shead, M. D. Chrysler, S. Mukherjee, B. M. Barnett, … 展开作者
V. A. Chirayath, R. W. Gladen, A. D. McDonald, A. J. Fairchild, P. V. Joglekar, S. Satyal, Z. H. Lim, T. N. Shead, M. D. Chrysler, S. Mukherjee, B. M. Barnett, N. K. Byrnes, A. R. Koymen, R. G. Greaves, A. H. Weiss
Here we describe an advanced multi functional, variable-energy positron beam system capable of measuring the energies of multiple positron-induced electrons in coincidence with the Doppler-shifted gamma photon resulting from the annihilation of the correlated positron. The measurements were carried out using the unique characteristics of the digital time-of-flight spectrometer and the gamma spectrometer available with the advanced positron beam system. These measurements have resulted in (i) the first digital time of flight spectrum of positron annihilation-induced Auger electrons generated using coincident signals from a high-purity Ge detector and a micro-channel plate; (ii) a two-dimensional array of the energy of Doppler-broadened annihilation gamma and the time of flight of positron-annihilation induced Auger electrons or secondary electrons measured in coincidence with the annihilation gamma photon; and (iii) the time of flight spectra of multiple secondary electrons ejected from a bilayer graphene surface as a result of the impact and(or) annihilation of positrons. The novelty of the gamma electron coincidence spectroscopy has been demonstrated by extracting the Doppler-broadened spectrum of gamma photons emitted due to the annihilation of positrons exclusively with 1s electrons of carbon. The width of the extracted Doppler-broadened gamma spectrum has been found to be consistent with the expected broadening of the annihilation gamma spectrum due to the momentum of the 1s electrons in carbon.
Coincidence technique and the coincidence measurement systems have been developed and applied for over 40 years. Most of popular coincidence measurement systems were based on analog electronics techniques such as time to amplitude conversion (TAC) or logic selecting coincidence unit. The above-mentioned systems are relatively cumbersome and complicated to use. With the strong growth of digital electronics techniques and computational science, the coincidence measurement systems will be constructed simpler but more efficient with the sake of application. This article presents the design princip…
The coincidence technique and the coincidence spectroscopy have been developed and applied for over 40 years. Most of popular coincidence measurement systems were based on analog electronics techniques such as time to amplitude conversion (TAC) or logic selecting coincidence unit. The above-mentioned systems are relatively cumbersome and complicated to use. With the strong growth of digital electronics techniques and computational science, the coincidence measurement systems will be constructed simpler but more efficient with the sake of application. This article presents the design principle …
We report on the design and performance of a double-sided coincidence velocity map imaging spectrometer optimized for electron-ion and ion-ion coincidence experiments studying inner-shell photoionization of gas-phase molecules with soft X-ray synchrotron radiation. The apparatus employs two microchannel plate detectors equipped with delay-line anodes for coincident, time- and position-resolved detection of photo- and Auger electrons with kinetic energies up to 300\,eV on one side of the spectrometer and photoions up to 25\,eV per unit charge on the opposite side. We demonstrate its capabilitie…
In the framework of rare event searches, the identification of radioactive contaminants in ultra-pure samples is a challenging task, because the signal is often at the same level of the instrumental background. This is a rather common situation for $α$-spectrometers and other detectors used for low-activity measurements. In order to obtain the target sensitivity without extending the data taking live-time, analysis strategies that highlight the presence of the signal sought should be developed. In this paper, we show how to improve the contaminant tagging capability relying on the time-correla…
The combination of a magnetic spectrometer and ancillary detectors such as silicon detectors is a powerful tool for the study of nuclear reactions and nuclear structure. This paper discusses the recently commissioned silicon array called the CAKE which is designed for use with the K600 magnetic spectrometer at iThemba LABS.
Evaluation of single, coincidence and anticoincidence gamma-ray spectrometry methods has been carried out with the aim to search for double-electron capture in 74Se. This process is unique, because there is probability for transition to the 2+ excited state in 74Ge (1204 keV), and de-excitation through two gamma-quanta cascade with energies of 595.9 keV and 608.4 keV. Long-term measurements with anticosmic shielded HPGe spectrometer and the coincidence HPGe-NaI(Tl) spectrometer did not show any evidence for the double-electron capture in 74Se. The best limit for the half-life of the double ele…
We demonstrate the feasibility of coincidence measurements in a conventional transmission electron microscope, revealing the temporal correlation between electron energy loss spectroscopy (EELS) and energy dispersive X-ray (EDX) spectroscopy events. We make use of a delay line detector with picosecond time resolution attached to a modified EELS spectrometer. We demonstrate that coincidence between both events, related to the excitation and de-excitation of atoms in a crystal, provides added information not present in the individual EELS or EDX spectra. In particular, the method provides EELS w…
MOSARIX is a collaborative project between three research group in Sorbonne University to build a x-ray spectrometer (2-5 keV) portable to large scale facilities with high efficiency and good resolution. X-ray spectroscopy and coincidences experiment are planned. A prototype with a single HADP crystal with von Hamos geometry has been tested (resolution and efficiency). A fast time and position detector has been realized (patent and publication).We plan to build the spectrometer with 8 HADP (or 4) crystals under Helium atmosphere using a TimePix3 or a CCD camera. MOSARIX is a project of an x-ra…
A new data acquisition system for the high resolution magnetic spectrometer Lintott at the superconducting Darmstadt electron linear accelerator S-DALINAC was developed. It allows inclusive and coincidence electron scattering experiments with event rates up to 10 kHz.
We report an analysis of electron-optical properties of a toroidal magnetic sector spectrometer and examine parameters for its implementation in a relativistic heavy-ion storage ring like HESR. For studies of free-free pair production in heavy-ion atom collisions this spectrometer exhibits very high efficiencies for coincident $e^+e^-$ pair spectroscopy over a wide range of momenta of emitted lepton pairs. The high coincidence efficiency of the spectrometer is the key for stringent tests of theoretical predictions for the coincident positron- and electron- emission characteristics and for the …
The Kaos spectrometer is maintained by the A1 collaboration at the Mainz Microtron MAMI with a focus on the study of (e,e'K^+) coincidence reactions. For its electron-arm two vertical planes of fiber arrays, each comprising approximately 10 000 fibers, are operated close to zero degree scattering angle and in close proximity to the electron beam. A nearly dead-time free DAQ system to acquire timing and tracking information has been installed for this spectrometer arm. The signals of 144 multi-anode photomultipliers are collected by 96-channel front-end boards, digitized by double-threshold dis…
The characterization of a liquid scintillator incorporating an aqueous solution of enriched lithium chloride to produce a scintillator with 0.40% Li-6 is presented, including the performance of the scintillator in terms of its optical properties and neutron response. The scintillator was incorporated into a fast neutron spectrometer, and the light output spectra from 2.5 MeV, 14.1 MeV, and Cf-252 neutrons were measured using capture-gated coincidence techniques. The spectrometer was operated without coincidence to perform thermal neutron measurements. Possible improvements in spectrometer perf…
New operation mode, "separated flow mode", has been developed for in-flight proton decay experiments with the SHARAQ spectrometer. In the separated flow mode, the protons and the heavy-ion products are separated and measured in coincidence at two different focal planes of SHARAQ. The ion-optical properties of the new mode were studied by using a proton beam at $246~{\rm MeV}$, and the momentum vector was properly reconstructed from the parameters measured in the focal plane of SHARAQ. In the experiment with the $({}^{16}{\rm O},{}^{16}{\rm F})$ reaction at a beam energy of $247~{\rm MeV/u}$, t…
We report an analysis of electron-optical properties of a toroidal magnetic sector spectrometer and examine parameters for its implementation in a relativistic heavy-ion storage ring like HESR at the future FAIR facility. For studies of free-free pair production in heavy-ion atom collisions, this spectrometer exhibits very high efficiencies for coincident $e^+e^-$ pair spectroscopy over a wide range of momenta of emitted lepton pairs. The high coincidence efficiency of the spectrometer is the key for stringent tests of theoretical predictions for the phase space correlation of lepton vector mo…
Incorrect choice of measuring geometry and signal discrimination thresholds for the BaF2 PAL spectrometer can lead to a significant distortion in the measured spectrum of positron lifetime. The contribution of the distorted events for non-optimal geometry (e.g. "face to face") can exceed 50%. It reduces the lifetime of the spectral components and redistributes intensities. Geant4 simulation permits to evaluate influence of measuring geometry on spectrum distortion and to choose the most appropriate discrimination thresholds. Optimal geometry with a lead absorber between the detectors permits t…
We present a description of the originally developed $β$-spectrometer consisting of two Si(Li)-detectors with sensitive area thickness above 8~mm and $4π$-geometry. The full absorption spectrometer allows for direct measurements of $β$-spectra, disregarding the corrections to the response function induced by the electron backscattering from the crystal surface. In case of $β$-spectra of transitions to the excited state of the daughter isotope additional 3" BGO-detector is used in order to detect the $γ$-quanta in coincidence with the pair of Si(Li)-spectrometers.
In this work, we report on the timing performances of the Time-Of-Flight (TOF) apparatus of the FRACAS large acceptance mass spectrometer designed to measure the fragmentation cross sections of a $^{12}$C beam in hadrontherapy. The TOF system is composed of a Parallel Plate Avalanche Counter and scintillating detectors to create so-called $Δ$E---TOF maps used in the fragment charge identification process. From tests with an alpha source and a $^{12}$C beam experiment, we measured a coincidence resolving time for the apparatus below 300 ps. Those results should lead in the final design to the i…
We present the development and performance of a newly built recoil ion momentum spectrometer to study the fragmentation dynamics of ionized molecules. The spectrometer is based on the two-stage Wiley-McLaren geometry and satisfies both time and velocity focusing conditions. An electrostatic lens has been introduced in the drift region to achieve velocity imaging and higher angular collection. The spectrometer is equipped with a 2D position-sensitive detector with multi-hit coincidence electronics. Ionic fragments with kinetic energy ~ 8 eV can be detected with 4π collection. The overall perfor…
A simplified digital spectrometer for the study of $γ$-rays with energies up to $\sim100$ MeV is presented and tested. The spectrometer is only consisted of a fast digital oscilloscope and three scintillation detectors which can work in single or in coincidence modes: two BGO-detectors comprising $\varnothing\,7.62\times7.62$ cm BGO-crystalls and one plastic detector which includes an organic polystyrene-based scintillator. The basic properties of the spectrometer (energy resolution, time resolution, $γ$-rays detection efficiency) were studied exhaustively also using a Geant4-based Monte-Carlo…
In this report, we present the energy calibration of the Hall B bremsstrahlung tagging system at the Thomas Jefferson National Accelerator Facility. The calibration was performed using a magnetic pair spectrometer. The tagged photon energy spectrum was measured in coincidence with $e^+e^-$ pairs as a function of the pair spectrometer magnetic field. Taking advantage of the internal linearity of the pair spectrometer, the energy of the tagging system was calibrated at the level of $\pm 0.1% E_γ$. The absolute energy scale was determined using the $e^+e^-$ rate measurements close to the end-poin…
The KATRIN experiment is going to search for the mass of the electron antineutrino down to 0.2 eV/c^2. In order to reach this sensitivity the background rate has to be understood and minimised to 0.01 counts per second. One of the background sources is the unavoidable Penning trap for electrons due to the combination of the electric and magnetic fields between the pre- and the main spectrometer at KATRIN. In this article we will show that by sweeping a conducting wire periodically through such a particle trap stored particles can be removed, an ongoing discharge in the trap can be stopped, and…
General Fusion is building the Fusion Demonstration Plant to demonstrate a magnetized target fusion scheme in which a deuterium plasma is heated from 200 eV to 10 keV by piston-driven compression of a liquid-lithium liner. The multilayer coaxial time-of-flight (MCTOF) neutron emission spectrometer is designed to measure the ion temperature near peak compression at which time the neutron yield will approach $10^{18}$ neutrons/s. The neutron energy distribution is expected to be Gaussian since the machine uses no neutral beam or radiofrequency heating. In this case, analysis shows that as few as…
The particle spectrometer SONIC for particle-$γ$ coincidence measurements was commissioned at the Institute for Nuclear Physics in Cologne, Germany. SONIC consists of up to 12 silicon $\mathitΔE$-$E$ telescopes with a total solid angle coverage of 9%, and will complement HORUS, a $γ$-ray spectrometer with 14 HPGe detectors. The combined setup SONIC@HORUS is used to investigate the $γ$-decay behaviour of low-spin states up to the neutron separation threshold excited by light-ion inelastic scattering and transfer reactions using beams provided by a 10 MV FN Tandem accelerator. The particle-$γ$ c…
Since its inception, velocity map imaging (VMI) has been a powerful tool for measuring the 2D momentum distribution of photoelectrons generated by strong laser fields. There has been continued interest in expanding it into 3D measurements either through reconstructive or direct methods. Recently much work has been devoted to the latter of these, particularly by relating the electron time-of-flight (TOF) to the third momentum component. The technical challenge here is having timing resolution sufficient to resolve structure in the narrow (< 10 ns) electron TOF spread. Here we build upon work in…
The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to make a model-independent determination of the effective electron antineutrino mass with a sensitivity of 0.2 eV/c$^{2}$. It investigates the kinematics of $β$-particles from tritium $β$-decay close to the endpoint of the energy spectrum. Because the KATRIN main spectrometer (MS) is located above ground, muon-induced backgrounds are of particular concern. Coincidence measurements with the MS and a scintillator-based muon detector system confirmed the model of secondary electron production by cosmic-ray muons inside the MS. Correlation m…
Suspensions of superheated superconducting grains are a detecting composite material. Each grain in the supension is a microcalorimeter with an energy threshold defined by its equatorial magnetic field for a given temperature. The higher the matrix density, the larger the gamma stopping power. For several years, cylindrical cells of such suspensions about 2 cm long and 0.4 mm in diameter can be read out in real time. As a result, using two independent cells, one can record a time coincidence between them. This could be potentially very useful for positron cameras where two diametrically opposi…
A prototype of DIRC-like Time-of-Flight detector (DTOF), including a pico-second time measurement electronics, is developed and tested preliminarily. The basic structure of DTOF is composed of a fused silica radiator connected to fast micro-channel plate PMTs (MCP-PMT), and readout by a dedicated FPGA (Field Programmable Gate Array) based front-end electronics. The full electronics chain consists of a programmable differential amplifier, a dual-threshold differential discriminator, and a timestamp Time-to-Digital convertor. By splitting a MCP-PMT output signal into two identical electronics ch…
