GeV Proton Beam Research Articles

Distribution of different no-carrier-added radionuclides in Pb and Bi fractions after separation of bulk components of lead bismuth eutectic

Large numbers of radionuclides are produced when 1.4 GeV proton beam hits lead bismuth eutectic (LBE) target. Separation of desired radionuclide from large amount of bulk components and other co-produced radionuclides is a challenging task. In this experiment, such a case has been simulated by irradiating a LBE target with low energy proton beam and spiked with nine radionuclides (56Co, 67 Ga, 90Nb, 149Gd, 157Dy, 172Lu, 182Re, 195mHg, 198Tl). The bulk Pb and bulk Bi were separated from irradiated LBE target matrix by different methods and the distribution pattern of these radionuclides were studied in the separated Pb and Bi fraction.

Blast from the past: Constraints on the dark sector from the BEBC WA66 beam dump experiment

We derive limits on millicharged dark states, as well as particles with electric or magnetic dipole moments, from the number of observed forward electron scattering events at the Big European Bubble Chamber in the 1982 CERN-WA-066 beam dump experiment. The dark states are produced by the 400~GeV proton beam primarily through the decays of mesons produced in the beam dump, and the lack of excess events places bounds extending up to GeV masses. These improve on bounds from all other experiments, in particular CHARM~II.

Search for η’-mesic nuclei using (p,d) reaction with FRS/Super-FRS at GSI/FAIR

We plan a semi-exclusive measurement of the 12C(p,dp) reaction to search for η’-mesic nuclei, aiming at investigating in-medium properties of the η′-meson. We employ a 2.5 GeV proton beam impinging on a carbon target to produce η′-mesic 11C nuclei via the 12C(p,d)η′⊗11C reaction. Using coincidence measurements of the forward going deuterons, important for missing-mass spectroscopy, and decay protons emitted from the η′-mesic nuclei. for event selection will provide a high experimental sensitivity to observe η’-mesic nuclei. We will perform the measurements by combining the WASA detector system with the fragment separator FRS at GSI and also with the Super-FRS at FAIR in the future. The plan of the experiments and the present status are reported.

Proton beam defocusing in AWAKE: comparison of simulations and measurements

In 2017, AWAKE demonstrated the seeded self-modulation (SSM) of a 400 GeV proton beam from the Super Proton Synchrotron at CERN. The angular distribution of the protons deflected due to SSM is a quantitative measure of the process, which agrees with simulations by the two-dimensional (axisymmetric) particle-in-cell code LCODE to about 5%. The agreement is achieved in beam population scans at two selected plasma densities and in the scan of longitudinal plasma density gradient. The agreement is reached only in the case of a wide enough simulation box (several plasma wavelengths) that is closer to experimental conditions, but requires more computational power. Therefore, particle-in-cell codes can be used to interpret the SSM physics underlying the experimental data.

Measurements of an AC-LGAD strip sensor with a 120 GeV proton beam

The development of detectors that provide high resolution in four dimensions has attracted wide-spread interest in the scientific community for several applications in high-energy physics, nuclear physics, medical imaging, mass spectroscopy as well as quantum information. LGAD silicon sensors with finely segmented AC-coupled electrodes can provide precise spatial and timing measurements of incident minimum ionizing particles. Such AC-coupled LGADs, also known as AC-LGADs, are therefore considered as candidates for future detectors to provide 4-dimensional measurements in a single sensing device with 100% fill factor. This article presents the first characterization of an AC-LGAD sensor with a proton beam of 120 GeV momentum at Fermilab. The sensor consists of strips with 80 μm width, fabricated at Brookhaven National Laboratory. The signal properties, efficiency, spatial, and time resolution are presented. The experimental results show that the time resolution of such an AC-LGAD is compatible to standard LGADs with similar gain, and that AC-LGADs can be segmented with fine pitches as standard strip or pixel detectors.

Quantification of radioisotopes produced in 1.4 GeV proton irradiated lead–bismuth eutectic targets

Six cylindrical lead bismuth eutectic (LBE) targets having fixed diameter of 6 mm and varying lengths of 8–50 mm were irradiated with a 1.4 GeV proton beam at CERN-ISOLDE. Both short-lived ( $$5\hbox { h } {<}\hbox {T}_{1/2} {<}5\hbox { days}$$ ) and long-lived ( $$\hbox {T}_{1/2} {>}5\hbox { days}$$ ) radionuclides were identified by off-line $$\upgamma $$ -spectrometry and their activities at the end of bombardment (EOB) were determined. Total 80 $$\upgamma $$ -emitting radionuclides, ranging from $$^{7}\hbox {Be}$$ to $$^{209}\hbox {At}$$ , were identified in the 50 mm long LBE target. The yields of all the radioisotopes were compared with the Monte Carlo Code FLUKA. The spallation reaction was the dominant mode whereas fission induced reactions had no significant contribution. The high energy proton irradiated LBE target may act as a large source of several clinically important and other exotic radionuclides.

Development of monolithic SOI pixel sensors capable of fine measurements of space and time

Silicon-on-insulator (SOI) for fine measurement of space and time (SOFIST) is designed taking full advantage of advanced SOI monolithic pixel detector fabrication technology to record the charge and time information of hit pixels. The aim is to achieve 3 μm position resolution and ultimately identify the International Linear Collider beam bunches of 554 ns separation. SOFIST Ver. 3 includes full circuits to read out the charge and time for each pixel of size 30×30μm. Its performance is evaluated using a 120 GeV proton beam. The time resolution is evaluated to be 1.92 μs (including calibration error), with an intrinsic time resolution of 1.34–1.55 μs. Additionally, multi-memory readout functionality is successfully examined. With SOFIST Ver. 4, the same functionality is to be realized with a 20×20μm pixel size by 3D stacking. The first chip was successfully tested to image β rays. The connection yield of Au micro-bumps is greater than 99.9%.

Beam commissioning and beam loss control for CSNS accelerators

The China Spallation Neutron Source (CSNS) accelerators consist of an 80 MeV H− linac and a 1.6 GeV proton rapid cycling synchrotron (RCS), which provides 1.6 GeV proton beam to the target at a repetition rate of 25 Hz. The beam commissioning of CSNS accelerators had been started since April 2017, and to the end of February 2020, the CSNS reached the design beam power of 100 kW. The most important issue in high-power beam commissioning is the beam loss control, as well as the control of induced activities, to meet the requirement of manual maintenance. A series of beam loss optimization work had been done to reduce the uncontrolled beam loss. Transverse and longitudinal matching in the MEBT was performed. For RCS commissioning, the orbit and lattice correction, the matching between the rf frequency and the dipole field, the tuning of the injection beam were performed. Many efforts have beam made to depress the effects of space charge and collective instability for beam loss control, such as injection optimization, longitudinal beam dynamics optimization, tune optimization. The beam commissioning procedure and results for CSNS accelerators are introduced in this paper.

Impact of 440 GeV Proton beams on Superconductors in a Cryogenic Environment

The superconducting magnets used in high energy particle accelerators such as CERN’s LHC can be impacted by the circulating beam in case of specific failures. This leads to interaction of the beam particles with the magnet components, like the superconducting coils, through direct beam impact or via secondary particle showers. The interaction causes energy deposition in the timescale of microseconds and induces large thermal gradients within the superconductors, which are in the order of 100 K/mm. To investigate the effect on the superconductors, an experiment at CERN’s HiRadMat facility was designed and executed, exposing short samples of Nb-Ti and Nb3Sn strands in a cryogenic environment to microsecond 440 GeV proton beams. The irradiated samples were extracted and analyzed for their critical transport current I c. This paper describes the results and analysis of the measurements of I c as well as thermo-mechanical simulations of the Nb3Sn strands to evaluate the degradation of I c as a function of the mechanical strain present during and after the beam impact.

Preliminary neutron study of a thorium-based molten salt energy amplifier

Present designs for molten salt thermal reactors require complex online processing systems, which are technologically challenging, while an accelerator-driven subcritical molten salt system can operate without an online processing system, simplifying the design. Previous designs of accelerator-driven subcritical systems usually required very high-power proton accelerators (> 10 MW). In this research, a proton accelerator is used to drive a thorium-based molten salt fast energy amplifier (TMSFEA) that improves the neutron efficiency of the system. The research results show that TMSFEA can achieve a long-term stable state for more than 30 years with a rated power of 300 MW and a stabilizing effective multiplication factor (keff) without any online processing. In this study, a physical design of an integrated molten salt energy amplifier with an initial energy gain of 117 was accomplished. According to the burn-up calculation, a molten salt energy amplifier with the rated power of 300 MWth should be able to operate continuously for nearly 40 years using a 1 GeV proton beam below 4 mA during the lifetime. By the end of the life cycle, the energy gain can still reach 76, and 233U contributes 70.9% of the total fission rate, which indicates the efficient utilization of the thorium fuel.

Superbeams and neutrino factories — Two paths to intense accelerator-based neutrino beams

High-energy and high-beam power accelerators are extensively used for the neutrino physics research. At present, the leading operational facilities are the J-PARC facility in Japan, which recently approached 0.5 MW of the 30 GeV proton beam power, and the Fermilab Main Injector complex that delivers over 0.75 MW of 120 GeV protons on the neutrino target. Besides such type of neutrino superbeams, the concept of neutrino factories offers great promise for particle physics research. In this brief review we present the status and planned upgrades of the J-PARC and Fermilab accelerators and leading proposals for the next generation accelerator-based facilities of both types, their challenges and required and ongoing accelerator R&amp;D programs aimed to address corresponding performance and cost risks.

COMET Phase-I technical design report

Abstract The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminum nucleus ($\mu$–$e$ conversion, $\mu^{-}N \rightarrow e^{-}N$); a lepton flavor-violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90% upper limit of a branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the $\mu$–$e$ conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.

R&D on the gas injection system of Beam Induced Fluorescence Monitor toward MW beam power at the J-PARC Neutrino Beam-line

A Beam Induced Fluorescence (BIF) monitor is being developed as an essential part of the monitor update toward MW beam power operation at the J-PARC neutrino beam line, where a 30 GeV proton beam is extracted, bent and struck onto a 90-cm-long graphite target to produce an intense and nearly pure muon (anti-)neutrino beam for the Tokai-to-Kamioka(T2K) experiment. A BIF monitor can measure the proton beam profile non-destructively and continuously spill-by-spill with fluorescence light produced by proton-N 2 interactions. In order to generate enough light to measure the profile precisely, it is necessary to temporarily increase the vacuum pressure near the BIF interaction point up to ~ 10−2 Pa during each beam spill while keeping the average pressure low (10−4 to 10−6 Pa) at other locations to protect vacuum equipment. Therefore, R&D of a pulsed gas injection system satisfying these requirements is in progress. We will report the recent R&D status of the gas injection system and prospects toward operation of a prototype monitor which we plan to install this fall 2019.

Spectroscopy of $\eta ^{\prime }$-mesic Nuclei with WASA at GSI/FAIR

We plan to conduct an experimental search for η0-mesic nuclei in order to investigate in-medium properties of the η0 meson. A 2.5 GeV proton beam is employed to produce η0-mesic 11C nuclei with the 12C(p,d)η0⊗ 11C reaction. Simultaneous measurements of the forward ejected deuterons and decay protons from η0-mesic nuclei will allow us to achieve high experimental sensitivity. The experiment will be performed at GSI by making full use of the fragment separator FRS and the WASA detector system. The plan of this proposed experiment is described.

Design and development of Ionization Profile Monitor for the Cryogenic sections of the ESS Linac

Saclay CEA/IRFU is working for the delivery of five Non-Invasive Profile Monitors in the frame of the in-kind contribution agreement signed with the European Spallation Source. Neutrons will be produced by spallation reactions of 2 GeV proton beam impinging on a Tungsten target. To accelerate protons a powerful linear accelerator of 5MW is under construction. Diagnostic devices are mandatory tools for the tuning and protection of the machine. The non-invasive profile monitors provide a measurement of the beam profile in transverse directions to the beam propagation. This project raises several physical and technical challenges including low signal detection of ions or electrons, profile distortions induced by the beam Space Charge effect and non-uniformities of electric field. Simulation and model of the critical aspects of the detector have been performed in order to prove the performance and the feasibility of the detector. A series of prototypes has been built with different readout types, and tested in real conditions at the 3MeV proton accelerator IPHI. All of them show some advantages and drawbacks revealed by the tests in real beam conditions. In this paper we present the results of the tests for the various configuration readout systems to agree with the model and simulation of the detector. In concluding remarks, we will discuss the performance of the prototypes and point out the camerabased one to be the more suitable for the final design.

Status and Physics of the SHiP experiment at CERN

SHiP is a new general purpose fixed target facility, whose Technical Proposal has been recently reviewed by the CERN SPS Committee and by the CERN Research Board. The two boards recommended that the experiment proceeds further to a Comprehensive Design phase in the context of the new CERN Working group ”Physics Beyond Colliders”, aiming at presenting a CERN strategy for the European Strategy meeting of 2019. In its initial phase, the 400 GeV proton beam extracted from the SPS will be dumped on a heavy target with the aim of integrating 2 × 1020 pot in 5 years. A dedicated detector, based on a long vacuum tank followed by a spectrometer and particle identification detectors, will allow probing a variety of models with light long-lived exotic particles and masses below O(10) GeV/c2. The main focus will be the physics of the so-called Hidden Portals, i.e. search for Dark Photons, Light scalars and pseudo-scalars, and Heavy Neutrinos. The sensitivity to Heavy Neutrinos will allow for the first time to probe, in the mass range between the kaon and the charm meson mass, a coupling range for which Baryogenesis and active neutrino masses could also be explained. Another dedicated detector will allow the study of neutrino cross-sections and angular distributions. ντ deep inelastic scattering cross sections will be measured with a statistics 1000 times larger than currently available, with the extraction of the F4 and F5 structure functions, never measured so far and allow for new tests of lepton non-universality with sensitivity to BSM physics.

Probing the Higgs portal at the Fermilab short-baseline neutrino experiments

The Fermilab Short-Baseline Neutrino (SBN) experiments, MicroBooNE, ICARUS, and SBND, are expected to have significant sensitivity to light weakly coupled hidden sector particles. Here we study the capability of the SBN experiments to probe dark scalars interacting through the Higgs portal. We investigate production of dark scalars using both the Fermilab Booster 8 GeV and NuMI 120 GeV proton beams, simulating kaons decaying to dark scalars and taking into account the beamline geometry. We also investigate strategies to mitigate backgrounds from beam-related neutrino scattering events. We find that SBND, with its comparatively short ${\cal O}(100\ {\rm m})$ baseline, will have the best sensitivity to scalars produced with Booster, while ICARUS, with its large detector volume, will provide the best limits on off-axis dark scalar production from NuMI. The SBN experiments can provide leading tests of dark scalars with masses in the 50 - 350 MeV range in the near term. Our results motivate dedicated experimental searches for dark scalars and other long-lived hidden sector states at these experiments.

Current status of slow extraction from J-PARC Main Ring

A 30 GeV proton beam accelerated in the J-PARC Main Ring (MR) is slowly extracted by the third integer resonant extraction and delivered to the hadron experimental facility. A dynamic bump scheme under achromatic condition drastically reduces beam hit rate on the septa devices, and we have attained 51 kW SX operation at 5.2 s cycle with high slow extraction efficiency of 99.5%. A spill duty factor indicating a uniformity of the time structure of the extracted beam is typically 50%. The current SX performance and future plans for improvements will be presented.

The SeaQuest spectrometer at Fermilab

The SeaQuest spectrometer at Fermilab was designed to detect oppositely-charged pairs of muons (dimuons) produced by interactions between a 120 GeV proton beam and liquid hydrogen, liquid deuterium and solid nuclear targets. The primary physics program uses the Drell-Yan process to probe antiquark distributions in the target nucleon. The spectrometer consists of a target system, two dipole magnets and four detector stations. The upstream magnet is a closed-aperture solid iron magnet which also serves as the beam dump, while the second magnet is an open aperture magnet. Each of the detector stations consists of scintillator hodoscopes and a high-resolution tracking device. The FPGA-based trigger compares the hodoscope signals to a set of pre-programmed roads to determine if the event contains oppositely-signed, high-mass muon pairs.

Prompt neutrinos and intrinsic charm at SHiP

We present a new evaluation of the far-forward neutrino plus antineutrino flux and number of events from charm hadron decays in a 400 GeV proton beam dump experiment like the Search for Hidden Particles (SHiP). Using next-to-leading order perturbative QCD and a model for intrinsic charm, we include intrinsic transverse momentum effects and other kinematic angular corrections. We compare this flux to a far-forward flux evaluated with next-to-leading order perturbative QCD, without intrinsic transverse momentum, that used the angular distribution of charm quarks rather than the neutrinos from their decays. The tau neutrino plus antineutrino number of events in the perturbative QCD evaluation is reduced by a factor of about three when intrinsic transverse momentum and the full decay kinematics are included. We show that intrinsic charm contributions can significantly enhance the number of events from neutrinos from charm hadron decays. Measurements of the number of events from tau neutrino plus antineutrino interactions and of the muon charge asymmetry as a function of energy can be used to constrain intrinsic charm models.