We present a method to measure the kinetic energy of electrons emitted upon ion impact via their time-of-flight. Pulsed beams of H$^{+}$, D$_2^{+}$, He$^{+}$ and Ne$^{+}$ ions with velocities between 0.4 and 3.5 a.u. are transmitted through thin, self-supporting carbon and gold foils. Transmitted ions and secondary electrons are detected with a position-sensitive detector behind the sample and their respective energies are determined via their flight times. A coincidence criterium can be applied in the acquisition software. Measured electron energies range between 10 and 400 eV. Above ion velocities of 1 a.u. the most probable electron energy scales with ion velocity pointing towards a kinetic emission mechanism. At lower ion velocities, the electron energy stays constant and lies above the maximum energy transfer possible in a classical binary collision between ion and electron. Potential applications and technical challenges of measuring electron energies and yields with a time-of-flight approach are discussed.
We report on spectroscopy and time-of-flight measurements using an 18 keV fast-pulsed photoelectron source of adjustable intensity, ranging from single photoelectrons per pulse to 5 photoelectrons per microsecond at pulse repetition rates of up to 10 kHz. Short pulses between 40 ns and 40 microseconds in length were produced by switching light emitting diodes with central output wavelengths of 265 nm and 257 nm, in the deep ultraviolet (or UV-C) regime, at kHz frequencies. Such photoelectron sources can be useful calibration devices for testing the properties of high-resolution electrostatic s…
We report results of tests of the MISANS technique at the CG-1D beamline at High Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL). A chopper at 40 Hz simulated a pulsed neutron source at the beamline. A compact turn-key MISANS module operating with the pulsed beam was installed and a well characterised MnSi sample was tested. The feasibility of application of high magnetic fields at the sample position was also explored. These tests demonstrate the great potential of this technique, in particular for examining magnetic and depolarizing samples, under extreme sample environment…
A new double time-of-flight (dTOF) neutron spectroscopy technique has been developed for pulsed broad spectrum sources with a duty cycle that results in frame overlap, where fast neutrons from a given pulse overtake slower neutrons from previous pulses. Using a tunable beam at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory, neutrons were produced via thick-target breakup of 16 MeV deuterons on a beryllium target in the cyclotron vault. The breakup spectral shape was deduced from a dTOF measurement using an array of EJ-309 organic liquid scintillators. Simulation of the neutron …
One of our two methods for fast-neutron imaging with spectrometric capability is presented here. It is a neutron-counting technique based on a hydrogenous neutron converter coupled to Gaseous Electron Multipliers (GEM). The principles of the detection techniques and the optimization of the converter, electron amplification and the readout are described. Evaluation of the properties are derived from a experiment in a pulsed neutron beam of spectral distribution between 2 and 10 MeV
The neutron time-of-flight (n_TOF) facility at the European Laboratory for Particle Physics (CERN) is a pulsed white-spectrum neutron spallation source producing neutrons for two experimental areas: the Experimental Area 1 (EAR1), located 185 m horizontally from the target, and the Experimental Area 2 (EAR2), located 20 m above the target. The target, based on pure lead, is impacted by a high-intensity 20-GeV/c pulsed proton beam. The facility was conceived to study neutron-nucleus interactions for neutron kinetic energies between a few meV to several GeV, with applications of interest for nuc…
The velocity of neutrons from a pulsed neutron source is well-defined as a function of their arrival time. Electromagnetic neutron accelerator/decelerator synchronized with the neutron time-of-flight is capable of selectively changing the neutron velocity and concentrating the velocity distribution. Possible enhancement of the neutron intensity at a specific neutron velocity by orders of magnitude is discussed together with an experimental design.
We present an experimental setup for laser-based angle-resolved time-of-flight (LARTOF) photoemission. Using a picosecond pulsed laser, photons of energy 10.5 eV are generated through higher harmonic generation in xenon. The high repetition rate of the light source, variable between 0.2-8 MHz, enables high photoelectron count rates and short acquisition times. By using a Time-of-Flight (ToF) analyzer with angle-resolving capabilities electrons emitted from the sample within a circular cone of up to \pm15 degrees can be collected. Hence, simultaneous acquisition of photoemission data for a comp…
Small-angle neutron scattering (SANS) is an experimental technique to detect material structures in the nanometer to micrometer range. The solution of the structural model constructed from SANS strongly depends on the accuracy of the reduced data. The time-of-flight (TOF) SANS data are dependent on the wavelength of the pulsed neutron source. Therefore, data reduction must be handled very carefully to transform measured neutron events into neutron scattering intensity. In this study, reduction algorithms for TOF SANS data are developed and optimized using simulated data from a virtual neutron …
A new Small Angle Neutron Scattering instrument is proposed for the European Spallation Source. The pulsed source requires a time-of-flight analysis of the gathered neutrons at the detector. The optimal instrument length is found to be rather large, which allows for a polarizer and a versatile collimation. The polarizer allows for studying magnetic samples and incoherent background subtraction. The wide collimation will host VSANS and SESANS options that increase the resolution of the instrument towards um and tens of um, respectively. Two 1m2 area detectors will cover a large solid angle simu…
The MAPS direct geometry time-of-flight chopper spectrometer at the ISIS pulsed neutron and muon source has been in operation since 1999 and its novel use of a large array of position-sensitive neutron detectors paved the way for a later generations of chopper spectrometers around the world. Almost two decades of experience of user operations on MAPS, together with lessons learned from the operation of new generation instruments, led to a decision to perform three parallel upgrades to the instrument. These were to replace the primary beamline collimation with supermirror neutron guides, to ins…
Two generations of a novel detector for high-resolution transmission imaging and spectrometry of fast-neutrons are presented. These devices are based on a hydrogenous fiber scintillator screen and single- or multiple-gated intensified camera systems (ICCD). This detector is designed for energy-selective neutron radiography with nanosecond-pulsed broad-energy (1 - 10 MeV) neutron beams. Utilizing the Time-of-Flight (TOF) method, such a detector is capable of simultaneously capturing several images, each at a different neutron energy (TOF). In addition, a gamma-ray image can also be simultaneous…
The Isochronous Mass Spectrometry (IMS) is a powerful tool for mass measurements of exotic nuclei with half-lives as short as several tens of micro-seconds in storage rings. In order to improve the mass resolving power while preserving the acceptance of the storage ring, the IMS with two Time-Of-Flight (TOF) detectors has been implemented at the storage ring CSRe in Lanzhou, China. Additional velocity information beside the revolution time in the ring can be obtained for each of the stored ions by using the double TOF detector system. In this paper, we introduced a new method of using a 658 nm…
The Time-Resolved Integrative Optical Neutron (TRION) detector was developed for Fast Neutron Resonance Radiography (FNRR), a fast-neutron transmission imaging method that exploits characteristic energy-variations of the total scattering cross-section in the En = 1-10 MeV range to detect specific elements within a radiographed object. As opposed to classical event-counting time of flight (ECTOF), it integrates the detector signal during a well-defined neutron Time of Flight window corresponding to a pre-selected energy bin, e.g., the energy-interval spanning a cross-section resonance of an ele…
Results of experimental investigations of a neutron resonances width in planar waveguides using the time-of-flight reflectometer REMUR of the IBR-2 pulsed reactor are reported and comparison with theoretical calculations is presented. The intensity of the neutron microbeam emitted from the waveguide edge was registered as a function of the neutron wavelength and the incident beam angular divergence. The possible applications of this method for the investigations of layered nanostructures are discussed.
A newly assembled multi-reflection time-of-flight mass spectrograph (MRTOF-MS) at RIKEN's RIBF facility became operational for the first time in spring 2020; further modifications and performance tests using stable ions were completed in early 2021. By using a pulsed-drift-tube technique to modify the ions' kinetic energy in a wide range, we directly characterize the dispersion function of the system for use in a new procedure for optimizing the voltages applied to the electrostatic mirrors. Thus far, a mass resolving power of $R_m > 1\,000\,000$ is reached within a total time-of-flight of onl…
The prompt gamma-ray spectrum from depleted uranium (DU) spherical shells induced by 14 MeV D-T neutrons is measured. Monte Carlo (MC) simulation gives the largest prompt gamma flux with the optimal thickness of the DU spherical shells 3-5 cm and the optimal frequency of neutron pulse 1 MHz. The method of time of flight and pulse shape coincidence with energy (DC-TOF) is proposed, and the subtraction of the background gamma-rays discussed in detail. The electron recoil spectrum and time spectrum of the prompt gamma-rays are obtained based on a 2"*2" BC501A liquid scintillator detector. The ene…
The first lead neutron slowing-down spectrometer (LSDS) from a pulsed source in elastic scattering on lead nuclei has been constructed in the laboratory of the atomic nucleus of the Physics Institute of the Russian Academy of Sciences LPI. Currently, there are several operating lead neutron slowing-down spectrometers: LSDS-100 in Russia, RINS in United States, KULS in Japan and others. A relation between an energy of lead slowing-down moderated neutrons E (eV) and the time delay of t (μs) is described by the expression: E(t) = K/(t + t_0)^2, where values of K=170.5 (keV μs^2), t_0 = 0.3 (μs) i…
Two detection systems based on optical readout were developed: a. Integrative optical detector A 2nd generation of Time-Resolved Integrative Optical Neutron (TRION) detector was developed. It is based on an integrative optical technique, which permits fast-neutron energy-resolved imaging via time-gated optical readout. This mode of operation allows loss-free operation at very high neutron-flux intensities. The TRION neutron imaging system can be regarded as a stroboscopic photography of neutrons arriving at the detector on a few-ns time scale. As this spectroscopic capability is based on the T…
The response of a scintillation detector with a cylindrical 1.5-inch LaBr3:Ce crystal to incident neutrons has been measured in the energy range En = 2-12 MeV. Neutrons were produced by proton irradiation of a Li target at Ep = 5-14.6 MeV with pulsed proton beams. Using the time-of-flight information between target and detector, energy spectra of the LaBr3:Ce detector resulting from fast neutron interactions have been obtained at 4 different neutron energies. Neutron-induced gamma rays emitted by the LaBr3:Ce crystal were also measured in a nearby Ge detector at the lowest proton beam energy. …
In the context of online ion range verification in particle therapy, the CLaRyS collaboration is developing Prompt-Gamma (PG) detection systems. The originality in the CLaRyS approach is to use a beam-tagging hodoscope in coincidence with the gamma detectors to provide both temporal and spatial information of the incoming ions. The ion range sensitivity of such PG detection systems could be improved by detecting single ions with a 100 ps ($σ$) time resolution, through a quality assurance procedure at low beam intensity at the beginning of the treatment session. This work presents the investiga…
The KATRIN experiment is designed for a direct and model-independent determination of the effective electron anti-neutrino mass via a high-precision measurement of the tritium $β$-decay endpoint region with a sensitivity on $m_ν$ of 0.2$\,$eV/c$^2$ (90% CL). For this purpose, the $β$-electrons from a high-luminosity windowless gaseous tritium source traversing an electrostatic retarding spectrometer are counted to obtain an integral spectrum around the endpoint energy of 18.6$\,$keV. A dominant systematic effect of the response of the experimental setup is the energy loss of $β$-electrons from…
