Hadron Beams Research Articles

Hadron beam evolution in microbunched electron cooling

The technique of microbunched electron cooling (MBEC) is a coherent cooling scheme with possible applications in high-energy hadron and electron-ion machines. In our previous work we analyzed the cooling of the hadron energy spread and transverse emittance using a one-dimensional (1D) technique that tracked the microscopic fluctuations in the hadron and electron beams. However, in order to obtain analytical expressions for our key quantities, we limited ourselves to calculating and optimizing only the initial values of the cooling rates. In this paper, we extend our approach so that it properly addresses the issue of the long-term, dynamic evolution of the hadron beam. In order to do so, it becomes necessary to consider the synchrotron motion of the hadron beam, in conjunction with the effects of diffusion and intrabeam scattering (IBS). With these modifications, our formalism allows us to develop a simple numerical tool that can effectively model the final state of hadron beam after many passages through the MBEC cooler.

Study of the hadron calorimeters response for CBM and BM@N experiments at hadron beams

The results of beam tests of the hadron calorimeter with transverse and longitudinal segmentation and with the micropixel photodetectors light readout performed at CERN T9 and T10 beamlines in proton momentum range 2-10 GeV/c are shown. The new signal processing technique based on the waveform fitting of calorimeter signals using the Prony least squares method is proposed. This technique allows to identify weak signals comparable to the level of electronic noise, which is important for performing a muon calibration of calorimeter sections. For the energy calibration of the hadron calorimeter sections with cosmic muons, a new approach that uses the reconstruction of the muon track in the calorimeter is proposed.

Activation experiment at the H4IRRAD facility: A comparison between experimental data, FLUKA and ActiWiz predictions after 15 days of cooling time

An experiment was carried out in June 2011 at the H4IRRAD facility, which allows to reproduce the radiation fields commonly encountered in the CERN Large Hadron Collider. The purpose of this study was to create a set of experimental activation data that can be used to benchmark Monte Carlo codes and now the analytical ActiWiz software package, both extensively used by CERN’s Radiation Protection Group. The choice of actual specimens that have been used for the construction of the Large Hadron Collider (LHC) and the LHC experiments has been made specifically in view of future upgrades or dismantling of CERN’s accelerators and experimental areas. Six samples of materials commonly used at CERN were irradiated by the secondary particles generated from the impact of a 280 GeV/c hadron beam on a 100 cm long copper target with the samples having been placed few centimetres below. This paper discusses first the experimental results obtained by γ-spectrometry measurements after 15 days of cooling time. Then, it discusses the FLUKA simulations performed in order to obtain the radionuclide inventories as well as the mixed particle fluence spectra in the samples. Third, it discusses the predictions by the ActiWiz software and compares them with the FLUKA results for the sake of a code comparison. Finally, the experimental and computational results are compared and discussed altogether.

Particle identification using Boosted Decision Trees in the Semi-Digital Hadronic Calorimeter prototype

The CALICE Semi-Digital Hadronic CALorimeter (SDHCAL) prototype using Glass Resistive Plate Chambers as a sensitive medium is the first technological prototype of a family of high-granularity calorimeters developed by the CALICE collaboration to equip the experiments of future leptonic colliders. It was exposed to beams of hadrons, electrons and muons several times in the CERN PS and SPS beamlines between 2012 and 2018. We present here a new method of particle identification within the SDHCAL using the Boosted Decision Trees (BDT) method applied to the data collected in 2015. The performance of the method is tested first with Geant4-based simulated events and then on the data collected by the SDHCAL in the energy range between 10 and 80 GeV with 10 GeV energy steps. The BDT method is then used to reject the electrons and muons that contaminate the SPS hadron beams. The rejection power of the new method is estimated to be as high as 99.0% for the muons and 99.4% for the electrons associated to a pion selection efficiency of about 95.0%.

Upgrade of the ATLAS Hadronic Tile Calorimeter for the High Luminosity LHC

The ATLAS hadronic Tile Calorimeter (TileCal) will undergo major upgrades to the on- and off-detector electronics in preparation for the high luminosity programme of the LHC (HL-LHC) in 2026. The system will cope with the HL-LHC increased radiation levels and out-of-time pileup. The on-detector electronics of the upgraded system will continuously digitize and transmit all photomultiplier signals to the off-detector systems at a 40 MHz rate. The off-detector electronics will store the data in pipeline buffers, reconstruct cell energy, produce digital hadronic cell sums of various granularity and send it to the Level-0 calorimeter trigger system, finally read out selected events. The modular front-end electronics feature radiation-tolerant commercial off-the-shelf components and redundant design to minimise single points of failure. The timing, control and communication interface with the off-detector electronics is implemented with modern Field Programmable Gate Arrays (FPGAs) and high speed fibre optic links running up to 9.6 Gb/s. The TileCal upgrade program has included extensive R&D and test beam studies using the beams from the Super Proton Synchrotron (SPS) accelerator at CERN. A Demonstrator module equipped with the novel electronics for the HL-LHC upgrade and compatible with the existing ATLAS read-out chain inserted in ATLAS in August 2019 for testing in actual detector conditions. We present the status of the upgrade program, the results using muon, electron and hadron beams at various incident energies and impact angles collected in 2015-2018, combined results of Demonstrator tests and calibration runs to evaluate the readiness of the new design.

The National Centre for Oncological Hadron therapy (CNAO): Present Status and Future Perspectives

Some elementary particles used for experiments of fundamental physics have properties useful to the treatments of patients affected by oncological pathologies. They are protons and carbon ions, collectively named hadrons, hence the term hadron therapy. Hadrons, in particular carbon ions, are more precise on the target than conventional X-rays and possess radiobiological characteristics suited to treat radioresistant or inoperable tumors. Italy is at the forefront of these techniques, and in Pavia a clinical facility called CNAO (Italian acronym that stands for National Centre for Oncological Hadron therapy) has treated so far more than 2800 patients with very good results. The CNAO was created by the Health Ministry and was realized by the CNAO Foundation in collaboration with the Italian Institute of Nuclear Physics (INFN), CERN, GSI and other institutions in Italy and abroad. The facility in Pavia delivers beams of hadrons in three treatment rooms with four fixed beam ports: three horizontal and one vertical. A new room, with an horizontal beamline and multiple isocenters, was completed and will be fully devoted to research applications. The CNAO has also launched a development programe to add a new single room for proton therapy with a gantry and a dedicated accelerator. Attention is also devoted to the most interesting aspects of research and development in the hadron therapy domain, like the creation of a new BNCT (Boron Neutron Capture Therapy) facility and the design of a novel gantry for carbon ions.

Timing performance of the LHCb VELO Timepix3 Telescope

We performed a detailed study of the timing performance of the LHCb VELO Timepix3 Telescope with a 180 GeV/c mixed hadron beam at the CERN SPS. A twofold method was developed to improve the resolution of single-plane time measurements, resulting in a more precise overall track time measurement. The first step uses spatial information of reconstructed tracks in combination with the measured signal charge in the sensor to correct for a mixture of different effects: variations in charge carrier drift time; variations in signal induction, which are the result of a non-uniform weighting field in the pixels; and lastly, timewalk in the analog front-end. The second step corrects for systematic timing offsets in Timepix3 that vary from −2 to 2 ns. By applying this method, we improved the track time resolution from 438(16) ps to 276(4) ps.

Leptons in the proton

As is the case for all light coloured Standard Model particles, also photons and charged leptons appear as constituents in ultrarelativistic hadron beams, and admit a parton density function (PDF). It has been shown recently that the photon PDF can be given in terms of the structure functions and form factors for electron-proton scattering. The same holds for lepton PDFs. In the present work we set up a calculation of the lepton PDFs at next-to-leading order, using the same data input needed in the photon case. A precise knowledge of the lepton densities allows us to study lepton-initiated processes even at a hadron collider, with all possible combinations of same-charge, opposite-charge, same-flavour, different-flavour leptons and leptons-quarks, most of which cannot be realized in any other forseable experiment. The lepton densities in the proton are extremely small, so that their contribution to Standard Model processes is generally shadowed by processes initiated by coloured partons. We will show, however, that there are cases where these processes can be relevant, giving rise to rare Standard Model signatures and to new production channels, that can enlarge the discovery potential of New Physics at the LHC and future high energy colliders with hadrons in the initial state.

The forward TPC system of the NA61/SHINE experiment at CERN: a tandem TPC concept

This paper presents the Forward Time Projection Chamber (FTPC) system of the NA61/SHINE experiment at the CERN SPS accelerator. This TPC system applies a novel tandem-TPC design to reduce the background originating from particle tracks not synchronous with the event trigger. The FTPC system is composed of three chambers with alternating drift field directions. The chambers were installed directly along the beamline region of the NA61/SHINE detector in a medium- to high-intensity (10−100 kHz) hadron or ion beam. The tandem TPC system has proved to be capable of rejecting out-of-time background tracks not associated with a primary interaction. In addition, the system performs tracking and inclusive dE/dx particle identification for particles at and near the beam momentum. This shows that a tandem-TPC-based chamber design may be used also in other experimental applications with a demand for low material budget, tracking capability, and the need for dE/dx particle identification, all while in the presence of a relatively high particle flux.

High-Brightness Continuous-Wave Electron Beams from Superconducting Radio-Frequency Photoemission Gun.

Continuous-wave photoinjectors operating at high accelerating gradients promise to revolutionize many areas of science and applications. They can establish the basis for a new generation of monochromatic x-ray free electron lasers, high-brightness hadron beams, or a new generation of microchip production. In this Letter we report on the record-performing superconducting rf electron gun with CsK_{2}Sb photocathode. The gun is generating high charge electron bunches (up to 10 nC/bunch) and low transverse emittances, while operating for months with a single photocathode. This achievement opens a new era in generating high-power beams with a very high average brightness.

Particle identification using Boosted Decision Trees in the semi-digital hadronic calorimeter

The CALICE Semi-Digital Hadronic CALorimeter (SDHCAL) prototype using Glass Resistive Plate Chambers as a sensitive medium is the first technological prototype in a family of high-granularity calorimeters developed by the CALICE collaboration to equip the experiments of future leptonic colliders. It was exposed to beams of hadrons, electrons and muons several times on the CERN PS and SPS beamlines in 2012, 2015 and 2016. We present here a new method of particle identification within the SDHCAL using the Boosted Decision Tree (BDT) method applied to the data collected in 2015. The performance of the method is tested first with GEANT4-based simulated events and then on the data collected in the SDHCAL in the energy range between 10 and 80 GeV with 10 GeV energy steps. The BDT method is then used to reject the electrons and muons which contaminate the SPS hadron beams.

Beam-tests of CMS High Granularity Calorimeter prototypes at CERN

As part of the HL-LHC detector upgrade programme, the CMS experiment is developing a High Granularity Calorimeter (HGCAL) to replace the existing endcap calorimeters. The HGCAL will be realised as a sampling calorimeter, including 36 layers of silicon pads and 14 layers combining silicon and scintillator detectors interspersed with metal absorber plates. Prototype modules based on 6-inch hexagonal silicon pad sensors with pad areas of 1.0 cm2 have been constructed. Beam tests of different sampling configurations made from these modules have been conducted at the CERN SPS using beams of charged hadrons and electrons with momenta ranging from 20 to 300 GeV/c. The setup was complemented with a CALICE AHCAL prototype: a scintillator-based sampling calorimeter, mimicking the proposed design of the HGCAL scintillator part. These proceedings summarise the test beam measurements performed at CERN in 2018, including the calibration of the detector with minimum ionizing particles and energy reconstruction performance of electron- and hadron-induced showers. We also show measurements of the timing capabilities of this prototype system and the steps being taken towards electron and hadron identification.

Extensive beam test study of prototype MRPCs for the T0 detector at the CSR external-target experiment

The Cooling Storage Ring (CSR) External-target Experiment (CEE) will be the first large-scale nuclear physics experimental device at the CSR of the Heavy-Ion Research Facility in Lanzhou (HIRFL) in China. A new T0 detector has been proposed to measure the multiplicity, angular distribution and timing information of charged particles produced in heavy-ion collisions at the target region. Multi-gap resistive plate chamber (MRPC) technology was chosen as part of the construction of the T0 detector, which provides precision event collision times (T0) and collision geometry information. The prototype was tested with hadron and heavy-ion beams to study its performance. By comparing the experimental results with a Monte Carlo simulation, the time resolution of the MRPCs are found to be better than sim 50 ps. The timing performance of the T0 detector, including both detector and readout electronics, is found to fulfil the requirements of the CEE.

Optimization of a Solenoid for an Electron Lens in SIS18

An electron lens – a novel instrument in accelerator physics to manipulate hadron beams with a magnetically confined electron beam - is under development at GSI, Darmstadt. It will be used to compensate the ion beam's space charge by an overlapping electron beam and therefore may help to increase the intensity of primary beams in the synchrotron SIS18 for FAIR. The main element of the lens is a solenoid with the longitudinal magnetic field of Bz = 600 mT and the requirements to the field homogeneity of ΔB/B less than ±5 × 10−4 relative units. The magnetic field in the solenoid will be ramped with the rate of up to 20 T/s. Acceptable geometry of the solenoid has been found by optimization of the coil parameters and the iron shield geometry. For this purpose we have combined the 2D finite element technology for the magnetic field modeling and the Nelder-Mead optimization strategy. Thorough investigation of the solenoid 3D model confirmed a quality and feasibility of the developed magnetic system.

Experimental Demonstration of Hadron Beam Cooling Using Radio-Frequency Accelerated Electron Bunches.

Cooling of beams of gold ions using electron bunches accelerated with radio-frequency systems was recently experimentally demonstrated in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. Such an approach is new and opens the possibility of using this technique at higher energies than possible with electrostatic acceleration of electron beams. The challenges of this approach include generation of electron beams suitable for cooling, delivery of electron bunches of the required quality to the cooling sections without degradation of beam angular divergence and energy spread, achieving the required small angles between electron and ion trajectories in the cooling sections, precise velocity matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched-beam cooling. Here we report on the first demonstration of cooling hadron beams using this new approach.

High-brightness electron beams for linac-based bunched beam electron cooling

A high-current high-brightness electron accelerator for low-energy RHIC electron cooling (LEReC) was successfully commissioned at Brookhaven National Laboratory. The LEReC accelerator includes a dc photoemission gun, a laser system, a photocathode delivery system, magnets, beam diagnostics, a superconducting rf booster cavity, and a set of normal conducting rf cavities to provide enough flexibility to tune the beam in the longitudinal phase space. Cooling with nonmagnetized rf accelerated electron beams requires longitudinal corrections to obtain a small momentum spread while preserving the transverse emittances. Electron beams with kinetic energies of 1.6 and 2.0 MeV with a beam quality suitable for cooling were successfully propagated through 100 m of beam lines, including dispersion sections, maintained through both cooling sections in RHIC and used for cooling ions in both RHIC rings simultaneously. The beam quality suitable for cooling RHIC beams was achieved in 2018, which led to the first experimental demonstration of bunched beam electron cooling of hadron beams in 2019.7 MoreReceived 22 November 2019Accepted 23 January 2020DOI:https://doi.org/10.1103/PhysRevAccelBeams.23.021003Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam coolingBeam opticsHigh intensity beam dynamicsAccelerators & Beams

Modeling of the emittance growth due to decoherence in collision at the Large Hadron Collider

The transverse emittance growth rate of colliding hadron beams driven by external sources of noise is investigated based on existing analytical model as well as on macro-particle simulations and comparison to experimental data at the Large Hadron Collider (LHC). It is shown that an analytical description of the emittance growth rate neglecting the existence coherent beam-beam mode can nevertheless provide accurate estimate for operational conditions, featuring notably a high chromaticity. The model is used to investigate the level of noise experienced by the LHC beams. The results indicate that a significant reduction of the noise floor of the transverse feedback's beam position monitor is required for operation with a large beam-beam tune shift, as the one anticipated for the High Luminosity LHC (HL-LHC).

Channeling efficiency in a target-crystal assembly

In view of possible future fixed target experiments requiring precisely steered charged particle beams, the UA9 Collaboration has undertaken experimental studies of the use of bent silicon crystals for this purpose. The channeling efficiency of positively charged particles inside the crystalline lattice has been investigated in detail for a setup with a tungsten target installed in front of the crystal. Due to multiple Coulomb scattering inside the target, the channeling efficiency was observed to be reduced by a factor of about 6.1 for a 180 GeV/c quasi-parallel hadron beam. The yield of nuclear interaction secondaries as an estimation of the additional machine background is also discussed.

The New CERN Low-energy Facilities for Neutrino Detector Tests

The beamlines at CERN’s North and East Areas offer secondary beams in a wide range of momenta between 0.5 GeV/c and 400 GeV/c for fixed-target experiments as well as for test beam campaigns with a flexible configuration and variable beam composition and intensities. Recently, two new facilities for neutrino detectors tests have been established in an extension of the CERN North Area in context of the CERN Neutrino Platform project. These new tertiary beams extend the current capabilities of the H2 and H4 beamlines towards lower momenta in the range of 0.3 GeV/c to 12 GeV/c, respectively 7 GeV/c, and currently serve the two ProtoDUNE prototype detectors. In addition, a complete overhaul of the CERN East Area is underway, which will provide secondary beams with momenta of up to 15 GeV/c (T9 beam) and 12 GeV/c (T10 beam). New beam optics and an optimised design will allow for electron, hadron and muon beams with high purity. We discuss the layout and performance of both North and East Area beamlines as well as the available infrastructure for the neutrino detector community.

PASSAT: particle accelerator helioScopes for Slim Axion-like-particle deTection

We propose a novel method to search for axion-like particles (ALPs) at particle accelerator experiments. ALPs produced at the target via the Primakoff effect subsequently enter a region with a magnetic field, where they are converted to photons that are then detected. Dubbed Particle Accelerator helioScopes for Slim Axion-like-particle deTection (PASSAT), our proposal uses the principle of the axion helioscope but replaces ALPs produced in the Sun with those produced in a target material. Since we rely on ALP-photon conversions, our proposal probes light (slim) ALPs that are otherwise inaccessible to laboratory-based experiments which rely on ALP decay, and complements astrophysical probes that are more model-dependent. As a first application, we reinterpret existing data from the NOMAD experiment in light of PASSAT, and constrain the parameter space for ALPs lighter than sim 100~mathrm{eV} and ALP-photon coupling larger than sim 10^{-4}~mathrm{GeV}^{-1}. As benchmarks of feasible low-cost experiments improving over the NOMAD limits, we study the possibility of re-using the magnets of the CAST and the proposed BabyIAXO experiments and placing them at the proposed BDF facility at CERN, together with some new detectors. We find that these realizations of PASSAT allow for a direct probe of the parameter space for ALPs lighter than sim 100~mathrm{eV} and ALP-photon coupling larger than sim 4times 10^{-6}~mathrm{GeV}^{-1}, which are regions that have not been probed yet by experiments with laboratory-produced ALPs. In contrast to other proposals aiming at detecting single or two-photon only events in hadronic beam dump environments, that rely heavily on Monte Carlo simulations, the background in our proposal can be directly measured in-situ, its suppression optimized, and the irreducible background statistically subtracted. Sensitivity evaluations with other beams will be the subject of a future paper. The measurements suggested in this paper represent an additional physics case for the BDF at CERN beyond those already proposed.