Neutron beam monitors with high efficiency, low gamma sensitivity, high time and space resolution are required in neutron beam experiments to continuously diagnose the delivered beam. In this work, commercially available neutron beam monitors have been characterized using the R2D2 beamline at IFE (Norway) and using a Be-based neutron source. For the gamma sensitivity measurements different gamma sources have been used. The evaluation of the monitors includes, the study of their efficiency, attenuation, scattering and sensitivity to gamma. In this work we report the results of this characterization.
Neutron beam monitors are an essential diagnostic component of neutron scattering facilities. They are used to measure neutron flux, calibrating experiments performed on the instruments, allowing measurement of facility performance, understanding of the effect on the neutrons of beam-line components (such as choppers), calibration of detectors and tracking of beam stability. Ideally beam monitors {should} not perturb the beam. Previous work shows commercial beam monitors attenuate the beam by a few percent in the worst case due to the 1-2 mm thick Aluminium entrance and exit windows and the ma…
Uranium fission chambers are commonly used for neutron beam monitoring in neutron research facilities. The challenges brought with the renewing or commissioning of new neutron facilities encourage to minimize the interaction between the monitor and the neutron beam. In order to characterize both their detection efficiency and transmission factor, several fission chambers, have been scanned on the CT1 monochromatic beam line of the ILL. Results show that the monitor transparency, measured at the center of the monitor, varies from 90% to 96%, and that the detection efficiency varies by as much a…
With the renewal of many neutron science instruments and the commissioning of new neutron facilities, there is a rising demand for improved neutron beam monitoring systems with reduced beam perturbations and higher counting rate capability. Fission chambers are the most popular beam monitors; however, their use on some instruments may be prevented by the background generated by fast neutrons emitted during neutron captures in 235U and by neutrons scattered in the material of the fission chamber. Multitube detectors, on the other hand, offer a good alternative with minimum beam perturbations. T…
In Chinese Spallation Neutron Source (CSNS), proton beam is used to hit metal tungsten target, and then high flux neutrons are generated for experiments on instruments. For neutron flux spectrum correction, boron-coated GEM, lithium glass and 3He are used as neutron beam monitor in instruments. To be integrated into neutron instrument control, a new DAQ software for neutron beam monitor is developed, called NEROS (Neutron Event Readout System). NEROS is based on EPICS V4 and a unified data format for CSNS neutron beam monitor is defined. The framework and software design of NEROS is introduced…
The back-streaming white neutron source (Back-n) is a comprehensive neutron experimental platform for nuclear data measurement, nuclear astrophysics, neutron irradiation, detector calibration, etc. In order to meet a variety of experimental requirements, an attempt of various combinations of collimators has been made for the current collimation system. The basic parameters such as beam flux and beam spot characteristics under different beam operation modes have been studied. According to the change of the CSNS proton beam operation mode, the influence of different proton beam spots on the Back…
Two types of neutron monitors with fine spatial resolution are proposed based on vibrating wire. In the first type, neutrons interact with the vibrating wire, heat it, and lead to the change of natural frequency, which can be precisely measured. To increase the heat deposition during the neutron scattering, use of gadolinium layer which has the highest thermal neutron capture cross section among all elements is proposed. The second type of the monitor uses vibrating wire as a resonant target. Besides the measurement of beam profile according to the average signal, the differential signal synch…
At the International Linear Collider (ILC), measurement of the beam profile at the interaction point (IP) is a key issue to achieve high luminosity. We studied the beam size measurement by combination of Pair Monitor and BeamCal. We obtained measurement accuracies of 2.7%, and 6.6% for the horizontal, and vertical beam sizes, respectively, for 50 bunch crossings.
A prototype quasi-parasitic thermal neutron beam monitor based on isotropic neutron scattering from a thin natural vanadium foil and standard $^3$He proportional counters is conceptualized, designed, simulated, calibrated, and commissioned. The European Spallation Source designed to deliver the highest integrated neutron flux originating from a pulsed source is currently under construction in Lund, Sweden. The effort to investigate a vanadium-based neutron beam monitor was triggered by a list of requirements for Beam Monitors permanently placed in the ESS neutron beams in order to provide reli…
The measurement of the neutron capture cross-section as a function of energy in the thermal range requires a precise knowledge of the absolute neutron flux. In this paper a new method of calibrating a thermal neutron beam using the controlled activation of sodium is described. The method is applied to the FP-14 Time Of Flight neutron beam line at the Los Alamos Neutron Science Center to calibrate the beam to a precision of $\pm5$%.
A white neutron beam line using the back-streaming neutrons from the spallation target at China Spallation Neutron Source (CSNS) is under construction. Different spectrometers mainly for nuclear data measurements to be installed in the so-called Back-n beam line are also under development in phases. The physics design of the beam line includes the overview of the characteristics of the neutron beam including energy spectrum, flux and time structure, and the optimizations of neutron beam spots and in-hall background with the help of a complicated collimation system and a sophisticated neutron d…
A scintillating-fiber beam profile detector has been designed, built and tested, for the monitoring of the position and size of the electron beam of the DAFNE, the recently commissioned electron beam-test facility at the Frascati LNF. A description of the detector construction and assembly, together with the results achieved during the 2003-2004 run, are here reported.
During 2014 the second experimental area EAR2 was completed at the n-TOF neutron beam facility at CERN. As the neutrons are produced via spallation, by means of a high-intensity 20 GeV pulsed proton beam impinging on a thick target, the resulting neutron beam covers an enormous energy range, from thermal to several GeV. In this paper we describe two beam diagnostic devices, designed and built at INFN-LNS, both exploiting silicon detectors coupled with neutron converter foils containing 6Li. The first one is based on four silicon pads and allows to monitor the neutron beam flux as a function of…
The CMS Beam Conditions and Radiation Monitoring System, BRM, will support beam tuning, protect the CMS detector from adverse beam conditions, and measure the accumulated dose close to or inside all sub-detectors. It is composed of different sub-systems measuring either the particle flux near the beam pipe with time resolution between nano- and microseconds or the integrated dose over longer time intervals. This paper presents the Fast Beam Conditions Monitor, BCM1F, which is designed for fast flux monitoring measuring both beam halo and collision products. BCM1F is located inside the CMS pixe…
The results of an experimental feasibility study of a position sensitive thermal neutron detector based on a resistive plate chamber (RPC) are presented. The detector prototype features a thin-gap (0.35 mm) hybrid RPC with an aluminium cathode lined with a 2 $μ$m thick $^{10}B{_4}C$ neutron converter layer enriched in $^{10}B$ and a float glass anode. A detection efficiency of ${\approx}$ 6.2 ${\%}$ was measured for the neutron beam ($λ$ =2.5 $Å$) at normal incidence. A spatial resolution better than 0.5 mm FWHM was demonstrated.
We demonstrate neutron beam focusing by axisymmetric mirror systems based on a pair of mirrors consisting of a confocal ellipsoid and hyperboloid. Such a system, known as a Wolter mirror configuration, is commonly used in x-ray telescopes. The axisymmetric Wolter geometry allows nesting of several mirror pairs to increase collection efficiency. We have implemented a system containing four nested Ni mirror pairs, which was tested by focusing a polychromatic neutron beam at the MIT Reactor. In addition, we have carried out extensive ray-tracing simulations of the mirrors and their performance in…
The Advanced Photon Source (APS) was commissioned in 1995 as a third-generation x-ray user facility. At that time orbit control was performed exclusively with broadband rf beam position monitors (BPMs). Since then, emphasis has been placed on incorporating x-ray beam position monitors into the orbit control algorithms. This has resulted in an order of magnitude improvement in long-term beam stability vertically, using x-ray BPMs (X-BPMs) on bending magnet beamlines. Additional processing will allow similar improvements horizontally, once systematic effects associated with variable insertion de…
We present a first experimental demonstration of a new method to extract a well-collimated beam of ultra-cold neutrons (UCN) from a storage vessel. Neutrons with too large divergence are not removed from the beam by an absorbing collimation, but a diffuse or semidiffuse channel with high Fermi potential reflects them back into the vessel. This avoids unnecessary losses and keeps the storage time high, which may be beneficial when the vessel is part of a UCN source with long buildup time of a high UCN density.
Evaluation of a method for time-of-flight, wavelength and distance calibration for neutron scattering instruments by means of a mini-chopper and standard neutron monitors
In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time is conducted with static objects mainly due to the limited flux intensity of neutron beamline faciliti…
In Chinese Spallation Neutron Source (CSNS), proton beam is used to hit metal tungsten target, and then high flux neutron are generated for experiments on instruments. For neutron flux spectrum correction, the current of proton beam is for each instrument. A real time monitor system is developed in CSNS, to monitor, broadcast and record each pulse of proton. Each proton pulse charge is measured and marked with high-precision timestamp. Then, the result of measurement will be broadcasted to control room and each neutron instrument. In control room, the proton charge of each pulse is listened an…
The capability of performing accurate measurements of neutron beam polarization opens a number of exciting opportunities in fundamental neutron physics and in neutron scattering. At the LANSCE pulsed neutron source we have measured the neutron beam polarization with absolute accuracy of 0.3% in the neutron energy range from 40 meV to 10 eV using an optically-pumped polarized 3He spin filter and a relative transmission measurement technique. 3He was polarized using the Rb spin-exchange method. We describe the measurement technique, present our results, and discuss some of the systematic effects…
For holographic gratings recorded in superparamagnetic nanoparticle-polymer composites the diffraction efficiency should -- next to grating spacing, nanoparticle concentration and grating thickness -- depend on the strength of an external magnetic field and the incident neutron spin state. As a consequence, diffraction gratings should be tunable to act as mirrors for one spin state, while being essentially transparent for the other. Thus, polarizing beam splitters for cold neutrons become feasible.
A beam monitor detector prototype based on doped silica fibres coupled to optical fibres has been designed, constructed and tested, mainly for accelerators used in medical applications. Scintillation light produced by Ce and Sb doped silica fibres moving across the beam has been measured, giving information on beam position, shape and intensity. Mostly based on commercial components, the detector is easy to install, to operate and no electronic components are located near the beam. Tests have been performed with a 2 MeV proton pulsed beam at an average current of 0.8 μA. The response character…
The Neutrinos at the Main Injector (NuMI) facility is a conventional neutrino beam which produces muon neutrinos by focusing a beam of mesons into a long evacuated decay volume. We have built four arrays of ionization chambers to monitor the position and intensity of the hadron and muon beams associated with neutrino production at locations downstream of the decay volume. This article describes the chambers' construction, calibration, and commissioning in the beam.
In view of the trend towards smaller samples and experiments under extreme conditions it is important to deliver small and homogeneous neutron beams to the sample area. For this purpose, elliptic and/or Montel mirrors are ideally suited as the phase space of the neutrons can be defined far away from the sample. Therefore, only the useful neutrons will arrive at the sample position leading to a very low background. We demonstrate the ease of designing neutron transport systems using simple numeric tools, which are verified using Monte-Carlo simulations that allow to take into account effects of…
A high-performance Scintillator Ion Beam Monitor (SIBM) provides diagnostics across a range of isotopes, energies, and intensities employing a machine-vision camera with two novel scintillator targets movable into/out of the beam without breaking vacuum. Scintillators are: 1) a semicrystalline polymer material (PM) film, 1-200 microns thick; 2) A 100-400 micron thick opaque wafer consisting of a hybrid of inorganic-polymer (HM) plastic matrix. The SIBM was demonstrated at the Facility of Rare Isotope Beams (FRIB, East Lansing, MI) real-time beam profile and rate analysis spanning more than fiv…
Prototypes of newly developed boron-coated straw (BCS) detectors have been tested in the thermal and cold neutron energy ranges. Their neutron detection performance has been benchmarked against the industry standard (detector tubes filled with 3He gas). The tests show that the BCS straws perform near their theoretical limit regarding the detection efficiency, which is adequate for scientific instruments in the cold neutron energy range. The BCS detectors perform on par with 3He tubes in terms of signal to noise and timing resolution, and superior regarding longitudinal spatial resolution.
The Beam Conditions and Radiation Monitoring System, BRM, is implemented in CMS to protect the detector and provide an interface to the LHC. Seven sub-systems monitor beam conditions and the radiation level inside the detector on different time scales. They detect adverse beam conditions, facilitate beam tuning close to CMS, and measure the doses accumulated in different detector components. Data are taken and analysed independently of the CMS data acquisition, displayed in the control room, and provide inputs to the trigger system and the LHC operators. In case of beam conditions dangerous to…
China Spallation Neutron Source (CSNS) will start commissioning in early 2018. The neutron spectra from the tungsten target bombarding by 1.6 GeV proton beam are very wide, namely white neutron spectra. Two white neutron beams schemed by CSNS are simulated by FLUKA. And the beam spectrum and intensity comparisons with other neutron sources in service are made. The fidelity of neutron spectra of these two white-neutron beam lines for chip irradiation experiments are estimated. The CSNS atmospheric-like neutron beams will be the first white neutron beam lines in China and the most intensive ones…
The puzzle remains in the large discrepancy between neutron lifetime measured by the two distinct experimental approaches -- counts of beta decays in a neutron beam and storage of ultracold neutrons in a potential trap, namely, the beam method versus the bottle method. In this paper, we propose a new experiment to measure the neutron lifetime in a cold neutron beam with a sensitivity goal of 0.1% or sub-1 second. The neutron beta decays will be counted in a superfluid helium-4 scintillation detector at 0.5 K, and the neutron flux will be simultaneously monitored by the helium-3 captures in the…
The near-Earth cosmic ray flux has been monitored for more than 70 years by a network of ground-based neutron monitors (NMs). With the ever-increasing importance of quantifying the radiation risk and effects of cosmic rays for, e.g., air and space-travel, it is essential to continue operating the existing NM stations, while expanding this crucial network. In this paper, we discuss a smaller and cost-effective version of the traditional NM, the mini-NM. These monitors can be deployed with ease, even to extremely remote locations, where they operate in a semi-autonomous fashion. We believe that …
We report the design and test results of a beam monitor developed for online monitoring in hadron therapy. The beam monitor uses eight silicon pixel sensors, \textit{Topmetal-${II}^-$}, as the anode array. \textit{Topmetal-${II}^-$} is a charge sensor designed in a CMOS 0.35 $μ$m technology. Each \textit{Topmetal-${II}^-$} sensor has $72\times72$ pixels and the pixel size is $83\times83$ $μ$m$^2$. In our design, the beam passes through the beam monitor without hitting the electrodes, making the beam monitor especially suitable for monitoring heavy ion beams. This design also reduces radiation …
After a short review of modern beam monitors, ionization and proportional counters and discussion on the necessity to have thinner wires, we propose and consider construction and parameters of nanotube particle beam monitors and counters
Accurately measuring the neutron beam polarization of a high flux, large area neutron beam is necessary for many neutron physics experiments. The Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) is a pulsed neutron beam that was polarized with a supermirror polarizer for the NPDGamma experiment. The polarized neutron beam had a flux of $\sim10^9$ neutrons per second per cm$^2$ and a cross sectional area of 10$\times$12~cm$^2$. The polarization of this neutron beam and the efficiency of a RF neutron spin rotator installed downstream on this beam were measured b…
We describe the Fundamental Neutron Physics Beamline (FnPB) facility located at the Spallation Neutron Source at Oak Ridge National Laboratory. The FnPB was designed for the conduct of experiments that investigate scientific issues in nuclear physics, particle physics, astrophysics and cosmology using a pulsed slow neutron beam. We present a detailed description of the design philosophy, beamline components, and measured fluxes of the polychromatic and monochromatic beams.
We report on the Beam EDM experiment, which aims to employ a pulsed cold neutron beam to search for an electric dipole moment instead of the established use of storable ultracold neutrons. We present a brief overview of the basic measurement concept and the current status of our proof-of-principle Ramsey apparatus.
In present work, we report an experimental method to measure the density and distribution of a supersonic gas jet used for charged particle beam profile monitoring. The density of the gas jet used in this monitor was in the range of $10^{14}$ - $10^{17}$ molecules/$m^3$.
Ultracold neutrons (UCNs) are a useful tool for fundamental physics experiments. They can be used to probe the lifetime of free neutrons, search for new CP violating processes and exotic interactions beyond the Standard Model, perform Ramsey spectroscopy, and carry out neutron-optical interference experiments. All of these experiments require high neutron count rates for good statistics. For optimal exploitation of experimental beam time, these experiments need to be prepared and, at times, even simulated in advance. To this end, it is crucial to know the velocity-dependent UCN flux at each be…
The analysis of beamstrahlung radiation, emitted from a beam of charged particles due to the electromagnetic interaction with a second beam of charged particles, provides a diagnostic tool that can be used to monitor beam-beam collisions in a $e^{+}e^{-}$ storage ring. In this paper we show that the beamstrahlung time profile is related to the timing of the collisions and the length of the beams, and how its measurement can be used to monitor and optimize collisions at the interaction point of the SuperKEKB collider. To measure the time dependence of beamstrahlung, we describe a method based o…
The beam position monitor (BPM) system for Fermilab Switchyard (SY) provides the position, intensity and integrated intensity of the 53.10348 MHz RF bunched resonant extracted beam from the Main Injector over 4 seconds of spill. The total beam intensity varies from 1x10^11 to 1x10^13 protons. The spill is measured by stripline beam postion monitors and resonant circuit. The BPMs have an external resonant circuit tuned to 53.10348 MHz. The corresponding voltage signal out of the BPM has been estimated to be between -110 dBm and -80 dBm.
This paper describes the Plateau de Bure Neutron Monitor (PdBNM), an instrument providing continuous ground-level measurements of atmospheric secondary neutron flux resulting from the interaction of primary cosmic rays with the Earth's atmosphere. The detector is installed on the Plateau de Bure (Devoluy mountains, south of France, latitude North 44° 38' 02", longitude East 5° 54' 26", altitude 2555 m) as a part of the ASTEP Platform (Altitude Single-event effects Test European Platform), a permanent installation dedicated to the study of the impact of terrestrial natural radiation on microele…
The intensity of charged particle beams at Fermilab must be kept within pre-determined safety and operational envelopes in part by assuring all beam within a few percent has been transported from any source to destination. Beam intensity monitors with toroidial pickups provide such beam intensity measurements in the transport lines between accelerators at FNAL. During Run II, much effort was made to continually improve the resolution and accuracy of the system.
A concept to search for a neutron electric dipole moment (nEDM) is presented, which employs a pulsed neutron beam instead of the nowadays established use of storable ultracold neutrons (UCN). The technique takes advantage of the high peak flux and the time structure of a next-generation pulsed spallation source like the planned European Spallation Source. It is demonstrated that the sensitivity for a nEDM can be improved by several orders of magnitude compared to the best beam experiments performed in the 1970's and can compete with the sensitivity of UCN experiments.
Muon beam monitoring is indispensable for indirectly monitoring accelerator-produced neutrino beams in real time. Though Si photodiodes and ionization chambers have been successfully used as muon monitors at the T2K experiment, sensors that are more radiation tolerant are desired for future operation. We have investigated the electron-multiplier tube (EMT) as a new sensor for muon monitoring. Secondary electrons produced by the passage of muons at dynodes are multiplied in the tube and produce signal. Two prototype detectors were installed at the T2K muon monitor location, and various EMT prop…
In order to test the capabilities of Barium Fluoride (BaF2) Crystal for dark matter direct detection, nuclear recoils are studied with mono-energetic neutron beam. The energy spectra of nuclear recoils, quenching factors for elastic scattering neutrons and discrimination capability between neutron inelastic scattering events and γ events are obtained for various recoil energies of the F content in BaF2.
The monocrystalline silicon neutron beam window is one of the key components of neutron spectrometers and thin circular plate.Monocrystalline silicon is a brittle material and its strength is not constant but is consistent with the Weibull distribution. The window is designed not simply through the average strength, but according to the survival rate. Bending deformation is the main form of the window, so dangerous parts of the neutron beam window is stress-linearized to the combination of membrane stress and bending stress. According to the Weibull distribution of bending strength of monocrys…
This introduction on beam position monitors (BPM) summarizes the fundamental parts of the tutorial presented at the CAS 2018 on beam instrumentation. The focus is on the signal detection and normalization, and on the principle of operation of commonly used broadband pickups, i.e.\ button and stripline BPMs. Other BPM types, such as split-plane and cavity BPMs are also discussed, as well as the detection of low-$β$ beams. Finally, a note on BPM signal processing techniques is given.
The Belle II experiment will be at the forefront of indirect searches for non-Standard-Model physics using billions of heavy quarks and $τ$ leptons produced in high-intensity 10 GeV electron-positron collisions from the SuperKEKB collider. The intense beams needed to achieve the required precisions are associated with high beam-background radiation that may damage the inner detectors. A dedicated radiation-monitoring and beam-abort system, based on artificial diamond sensors, ensures protection and safe data taking conditions. I briefly outline the system and illustrate the operational experie…
The results of measurements performed using UCN storing method are in good agreement. The latest most accurate measurements of the neutron decay asymmetry and neutron lifetime measurements by storage method are in agreement within the Standard Model. However, there is a significant discrepancy at $3.6σ$ (1% of decay probability) level with beam method experiment. This article discusses the possible causes of discrepancy in the measurements of the neutron lifetime with beam method experiment. The most probable cause, apparently, is the loss of protons in beam method experiment during storage in…
The scintillating fiber-SiPM beam monitor detectors, designed to deliver beam informations for the R484 and R582 experiments at the high intensity, low energy pulsed muon beam at the RIKEN-RAL facility, have been successfully constructed and operated. Details on their construction and first performances in beam are reported
The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) aims to make a unique measurement of neutron yield from neutrino-nucleus interactions and to perform R&D for the next generation of water-based neutrino detectors. In this paper, we characterize beam-induced neutron backgrounds in the experimental hall at Fermi National Accelerator Laboratory. It is shown that the background levels are sufficiently low to allow the next stage of the experiment to proceed. These measurements are relevant to other Booster Neutrino Beam (BNB) experiments located adjacent to ANNIE Hall, where dirt neu…
