High-intensity Particle Beams Research Articles

The MUonE DAQ: online track-finding andevent selection in hardware at 40 MHz

High-intensity particle beams provide a significant challenge to DAQ systems, especially in complex architectures reading out many sensors. The MUonE experiment has been conducting beam tests using the M2 muon beam at CERN, with in-spill intensity of 5 × 107 muons/s, using tracking modules equipped with silicon strip sensors and a module readout bandwidth of 5 Gb/s. A pilot run has been performed in late summer 2023, incorporating several such modules arranged in three tracking stations and a prototype of an electromagnetic calorimeter connected to a triggerless readout system. Limits on processing and data storage will necessitate online event selection to be implemented in hardware, on state-of-the-art AMD-Xilinx UltraScale+ FPGAs.The status and plans of the MUonE DAQ operation will be presented, outlining a general purpose platform for online event selection, from simple occupancy cuts, to track reconstruction, vertexing, and particle identification.

Damage experiment with superconducting sample coils - experimental setup and observations during beam impact

The damage mechanisms and limits of superconducting accelerator magnets due to the impact of high-intensity particle beams have been subject to extensive studies in the past years at CERN. Recently an experiment with dedicated sample coils made from Nb–Ti and Nb3Sn strands was performed at CERN’s HiRadMat facility. This paper describes the design and construction of the sample coils as well as the results of their qualification before the beam impact. In addition, the experimental setup will be discussed. Finally, measurements during the beam experiment like the beam-based alignment, the observations during the impact of 440GeV protons on the sample coils and the achieved hot-spots and temperature gradients will be presented.

Radiation protection basis of design for the South African isotope facility - SAIF

To expand on its research agenda and meet the growing demand for nuclear medicine products, the South African Isotope Facility (SAIF) was launched. This study focuses on Radiation Protection aspects for SAIF Phase 1, specifically the verification of existing- and basis of design for supplementary engineering controls for the retrofitted accelerator complex, housing an IBA C70 Cyclone 70 MeV H-minus cyclotron and four in-house designed high intensity particle beam target stations. For the dosimetric assessment, a selection of calibrated instruments were used to determine the ambient dose equivalent rate H*(10) at points of interest. Physical dose rate measurements were performed for various source terms (66 MeV p+ on Cu, Al, Mg, Ga and Li) and beam intensities up to tens of micro Amperes, beyond in-situ bulk shielding material, for compound shielded target stations and streaming through existing labyrinths. Comparisons are drawn between actual measurements and the FLUKA code. Primarily to determine the in-situ shielding characteristics of unverified bulk shielding material cast in the 1980s, as core drill samples yielded vastly divergent aggregate types and material densities.

Fluence Beam Monitor for High-Intensity Particle Beams Based on a Multi-Gap Ionization Chamber and a Method for Ion Recombination Correction

This work presents the tests of a multi-gap detector (MGD), composed of three parallel-plate ionization chambers (ICs) with different gap widths, assembled to prove the capability of correcting for charge volume recombination which is expected to occur when high fluence rates are delivered. Such beam conditions occur with a compact accelerator for charged particle therapy developed to reduce the costs, to accomplish faster treatments and to exploit different beam delivery techniques and dose rates as needed, for example, for range modulation and FLASH irradiations, respectively. The MGD was tested with carbon ions at the Centro Nazionale di Adroterapia Oncologica (CNAO Pavia, Italy), and with protons in two different beam lines: at Bern University Hospital with continuous beams and at the Laboratori Nazionale del Sud (Catania, Italy) of the Italian National Center of Nuclear Physics (INFN) with pulsed beams. For each accelerator, we took measurements with different beam intensities (up to the maximum rate of ionization achievable) and changed the detector bias voltage (V) in order to study the charge collection efficiency. Charge recombination models were used to evaluate the expected collected charge and to measure the linearity of the rate of ionization with the beam fluence rate. A phenomenological approach was used to determine the collection efficiency (f1) of the chamber with thinnest gap from the relative efficiencies, f1/f2 and f1/f3, exploiting the condition that, for each measurement, the three chambers were exposed to the same rate of ionization. Results prove that two calibration curves can be determined and used to correct the online measurements for the charge losses in the ICs for recombination.

A Starry Byte — proton beam measurements of single event upsets and other radiation effects in ABCStar ASIC Versions 0 and 1 for the ITk strip tracker

Single Event Effects (SEEs) — predominately bit-flips in electronics caused by particle interactions - are a major concern for ASICs operated in high radiation environments such as ABCStar ASICs, which are designed to be used in the future ATLAS ITk strip tracker. The chip design is therefore optimised to protect it from SEEs by implementing triplication techniques such as Triple Modular Redundancy (TMR). In order to verify the radiation protection mechanisms of the chip design, the cross-section for Single Event Upsets (SEUs), a particular class of SEEs, is measured by exposing the chip to high-intensity particle beams while monitoring it for observed SEUs. This study presents the setup, the performed measurements, and the results from SEU tests performed using the latest version of the ABCStar ASIC (ABCStar V1) using a 480 MeV proton beam.

High intensity proton beam impact at 440 GeV/c on Mo and Cu coated CfC/graphite and SiC/SiC absorbers for beam intercepting devices

Beam Intercepting Devices (BIDs) are essential protection elements for the operation of the Large Hadron Collider (LHC) complex. The LHC internal beam dump (LHC Target Dump Injection or LHC TDI) is the main protection BID of the LHC injection system; its main function is to protect LHC equipment in the event of a malfunction of the injection kicker magnets during beam transfer from the SPS to the LHC. Several issues with the TDI were encountered during LHC operation, most of them due to outgassing from its core components induced by electron cloud effects, which led to limitations of the injector intensity and hence had an impact on LHC availability. The absorbing cores of the TDIs, and of beam intercepting devices in general, need to deal with high thermo-mechanical loads induced by the high intensity particle beams. In addition, devices such as the TDI — where the absorbing materials are installed close to the beam, are important contributors to the accelerator impedance budget. To reduce impedance, the absorbing materials that make up the core must be typically coated with high electrical conductivity metals. Beam impact testing of the coated absorbers is a crucial element of development work to ensure their correct operation.In the work covered by this paper, the behaviour of several metal-coated absorber materials was investigated when exposed to high intensity and high energy proton beams in the HiRadMat facility at CERN. Different coating configurations based on copper and molybdenum, and absorbing materials such as isostatic graphite, Carbon Fibre Composite (CfC) and Silicon Carbide reinforced with Silicon Carbide fibres (SiC-SiC), were tested in the facility to assess the TDI's performance and to extract information for other BIDs using these materials. In addition to beam impact tests and an extensive Post Irradiation Examination (PIE) campaign to assess the performance of the coatings and the structural integrity of the substrates, extensive numerical simulations were carried out.

An adaptive masking method for beam halo measurement by a digital micro mirror device

In high intensity particle beams, irregularities in cathode emission, scattering effects, dark current and space charge forces can lead to a common phenomenon termed beam halo with associated emittance growth, beam loss and overall beam quality degradation. It is of fundamental interest and practical importance to precisely monitor such beam halo, which could offer valuable insights into the experimental strategy for the suppression of this undesired feature [1]. A Digital Micro mirror Device (DMD) is a computer-controlled micro-electrical-mechanical system that contains a compact array of physically independent reflective mirrors. Using a standard DMD, we come up with an adaptive masking method for halo measurement, which demonstrates superior robustness and efficiency comparing to the conventional approaches as confirmed by simulation and experimental results. Our development includes an integrated package of hardware, software and a graphic user interface (GUI) that is robust and portable and can be applied as a beam halo diagnostic for electron guns or radiating charged particle beams in general.

Photoconductive gain in single crystal diamond detectors

Diamond crystals equipped with two metal electrodes can be operated as solid state ionization chambers for the detection of energetic radiation. Under irradiation with single α particles, the generated free electrons and holes are collected with a maximum efficiency close to 100%. When the same detectors are used for dosimetry in high intensity and high energy photon or particle beams, photoconductive gain G with values up to ≈106 is frequently observed as described in the literature. In this work, we studied theoretically the irradiation induced conductivity of perfect diamond single crystals with ohmic contacts containing nitrogen and boron with concentrations NN and NB, respectively, as only chemical impurities. Based on four rate equations, two considering the charge states of N and B and two the concentrations of free carriers n and p, and, additionally, the neutrality condition, we could derive analytical solutions for the gain G as a function of impurity concentrations, crystal thickness, and excitation density. It turned out that G varies systematically with the compensation ratio R=(NN−NB)/NB over five orders of magnitude. For R≈103, the gain G is close to unity. With decreasing R, the gain increases ∝1/R until saturation is reached for R≪1 and G≈104–105. Our theoretical data yield plausible explanations for the major trends that have been found experimentally in previous studies. They provide a valuable guideline for the future synthesis of diamond crystals to be used for manufacturing UV and radiation detectors.

Silicon crystals for steering high-intensity particle beams at ultrahigh-energy accelerators

Experimental results and simulation models show that crystals might play a relevant role for the development of new generations of high-energy and high-intensity particle accelerators and might disclose innovative possibilities at existing ones. In this paper we describe the most advanced manufacturing techniques of crystals suitable for operations at ultra-high energy and ultra-high intensity particle accelerators, reporting as an example of potential applications the collimation of the particle beams circulating in the Large Hadron Collider at CERN, which will be upgraded through the addition of bent crystals in the frame of the High Luminosity Large Hadron Collider project.

Evaluation of CCD cameras for beam profile monitoring with high intensity particle beams traversing gases

Measurements of the absolute sensitivity of three different optical cameras are presented. An absolutely calibrated tungsten strip-lamp was used for calibrating the devices. An experimental method for determining the solid angle which is accepted by the combination of the cameras with a broadband apochromatic lens is described. The results with five bandpass filters between 337nm and 740nm are shown. The signal to noise ratio and the spatial resolution of the camera systems is also discussed.

Development of a Spark-Detection System for the Quality Assurance of Large-Area GEM-Foils

Gaseous detectors based on large-size GEM-foils are planned to be used for a variety of upgrades and new experiments using high-rate and high-intensity particle beams. An excellent quality control of GEM-foils is a mandatory prerequisite to select the best foils for the assembly of a GEM detector. The high voltage stability of the foils is here of uppermost importance. In particular discharges that occur at the same position need to be detected. A spark detection system has been developed to automatically detect and record the time and position of sparks. The system is based on a commercial web camera installed in a housing for the tests and a custom-made, LabVIEW-based software for control and operation. An automatic Spark-Detection System for GEM foils was designed, built and characterized. It is able to detect and record discharges in large-size GEM foils during the quality control procedure. The spark detection e ciency was estimated to be higher than 97 %, the position resolution was determined to be approximately 0.5 mm. With this system, the characterization of GEM foils can be standardized to a much greater degree than before.

Noninvasive Micrometer-Scale Particle-Beam Size Measurement Using Optical Diffraction Radiation in the Ultraviolet Wavelength Range

We present recent achievements in the application of optical diffraction radiation (ODR) to the measurement of the transverse beam size of a 1.3 GeV micrometer-size electron beam performed with an instrument installed in the extended extraction line of the KEK Accelerator Test Facility. ODR is a recent technique for the measurement of the transverse size and emittance of highly relativistic particle beams. ODR has the advantage of being a noninvasive and relatively inexpensive technique and is a candidate for the operation of linear particle accelerators, where no simple alternatives (e.g., synchrotron radiation) are available. In an effort to improve the resolution and performance, we establish an alternative target microfabrication technology, adopt solutions to improve the signal-to-noise ratio, and perform an experiment in the UV spectrum at 250 nm. With such a configuration, a transverse beam size as low as $3\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ is measured, drastically improving on past measurements reported in the literature. In light of these results, ODR, when combined with a high-resolution optical-transition-radiation monitor, represents a credible diagnostics solution for low-emittance high-intensity particle beams.

Quadrupolar mode measurements for space charge dominated beams

On-line monitoring of beam quality requires non-invasive transverse phase space diagnostics. Emittance measurement is particularly challenging for high-intensity particle beams since space charge complicates the beam dynamics during measurement. Quadrupolar mode measurements have been empirically shown to provide information about the beam emittance, but so far only for small relative space charge effects, where the results depend on a linear theory. We present a quadrupolar mode measurement for space charge dominated beams with unsplit tunes using multi-turn resonant excitation. Results from experiments performed at the University of Maryland Electron Ring are compared to both analytic and numerical analysis of the rms envelope equations.

Dynamics of intense particle beam in axial-symmetric magnetic field

Axial-symmetric magnetic field is often used in focusing of particle beams. Most existing ion Low Energy Beam Transport lines are based on solenoid focusing. Modern accelerator projects utilize superconducting solenoids in combination with superconducting accelerating cavities for acceleration of high-intensity particle beams. Present article discusses conditions for matched beam in axial-symmetric magnetic field. Analysis allows us to minimize power consumption of solenoids and beam emittance growth due to nonlinear space charge, lens aberrations, and maximize acceptance of the channel. Expressions for maximum beam current in focusing structure, beam emittance growth due to spherical aberrations and non-linear space charge forces are derived.

Acceleration of Macroscopic Particle to Hypervelocity by High-Intensity Beams

Hypervelocity (~1000-km/s) impact of a macroscopic particle (macron) has profound influences in high energy density physics and inertial fusion energy researches. As the charge-mass ratio of macrons is too low, the length of an electrostatic accelerator can reach hundreds to thousands of kilometers, rendering macron acceleration impractical. To reduce the accelerator length, a much higher electric field than what the most powerful klystrons can provide is desired. One practical choice may be the high-intensity charged particle beam ldquoblowing-piperdquo approach. In this approach, a high-intensity (~10-kA) medium-energy (0.5-2-MeV) long-pulse (10-1000-mus) positively charged ion beam shots to a heavily charged millimeter-size macron to create a local high-strength electric field (~1010 V/m), accelerating the macron efficiently. We will discuss the physics and challenges involved in this concept and give an illustrative simulation.

Can hydrogen pellets be vaporized by the stored beam?

We outline a potential problem in terms of extra gas load when a high-intensity particle beam with small beam size traverses hydrogen pellets. We also investigate whether secondary electrons can escape the pellets and thereby alleviate the thermal process and thus the rate of evaporation. Finally we model the pellet heating induced by antiproton beam fluxes to be expected at PANDA.

Advances of dense plasma physics with particle accelerators

High intensity particle beams from accelerators induce high energy density states in bulk matter. The SIS-18 heavy ion synchrotron at GSI now routinely delivers intense Uranium beams that deposit about I kJ/g of specific energy in solid matter, e.g. solid lead. Due to the specific nature of the ion-matter interaction a volume of matter is heated uniformly with low gradients of temperature and pressure in the initial phase, depending on the pulse structure of the beam with respect to space and time. The new accelerator complex FAIR (Facility for Antiproton and ion Research) at GSI as well as beams from the CERN large hadron collider (LHC) will vastly extend the accessible parameter range for high energy density states. One special piece of accelerator equipment a superconducting high field dipole magnet, developed for the LHC at CERN is now serving as a key instrument to diagnose the dense plasma of the sun interior plasma, thus providing an extremely interesting combination of accelerator physics, plasma physics and astro-particle physics.

Computations for nonlinear force driven plasma blocks by picosecond laser pulses for fusion

The concept of the fast ignitor for laser fusion has led to some modifications in applying petawatt-picosecond (PW-ps) laser-produced high intensity particle beams to ignite deuterium-tritium (DT) fuel. Some very anomalous measurements of ion emission from targets irradiated by picosecond laser pulses led to the development of a skin depth interaction scheme where a defined control of prepulses is necessary. Based on these experimental facts, we have applied a one-dimensional two-fluid hydrodynamic code to understand how the nonlinear ponderomotive force generates two plasma blocks, one moving against the laser light (ablation) and the other moving into the target. This compressed block produces an ion current density of above 10$^{11}$ A cm$^{-2}$ and an ion energy of about 100 keV. This may be a rather promising option to use PW-ps laser pulses for igniting fusion in solid density DT fuel, realizing very high gain controlled fusion reactions.

Design and construction of a GEM-TPC prototype for research and development purposes

For a number of running and future particle-physics experiments, studies on the readout of time projection chambers (TPCs) based on the gas electron multiplier (GEM) are ongoing. This technology offers higher granularity and intrinsically suppressed ion feedback as the two major advantages compared to a conventional readout with multiwires. We describe the design and construction of a small and flexible TPC prototype, whose cylindrical drift volume can be equipped with endcaps of different gas detector types. Its field cage is designed in a double-ring layout to guarantee high homogeneity of the electric field. All materials facing the gas volume have been selected with special respect to detector aging properties. An endcap with multi-GEM readout is currently set up and successfully operated with a modified version of the STAR-TPC electronics. The functionality of the detector has been verified in system checks, and its performance could recently be tested in high-intensity particle beams.

A GEM-TPC prototype with low-noise highly integrated front-end electronics for linear collider studies

Connected to the linear collider project, studies on the readout of time projection chambers (TPCs) based on the gas electron multiplier (GEM) are ongoing. Higher granularity and intrinsically suppressed ion feedback are the major advantages of this technology. After a short discussion of these issues, we present the design of a small and very flexible TPC prototype, whose cylindrical drift volume can be equipped with endcaps of different gas detector types. An endcap with multi-GEM readout is currently set up and successfully operated with a low-noise highly integrated front-end electronics. We discuss results of measurements with this system in high intensity particle beams at CERN, where 99.3 /spl plusmn/ 0.2 % single-pad-row efficiency could be achieved at an effective gain of 2.5 /spl times/ 10/sup 3/ only, and spatial resolutions down to 63 /spl plusmn/ 3 /spl mu/m could be demonstrated. Finally, these results are extrapolated to the high magnetic field in a linear collider TPC.