Pb Ion Beam Research Articles

First results of running the LHC with lead ions at a beam energy of 6.8 Z TeV

A two-day test of operation with Pb ion beams was carried out in the CERN Large Hadron Collider (LHC) in 2022, with the aim of gaining experience in view of the future high luminosity heavy-ion physics runs from 2023 onwards. The LHC experiments received the first Pb-Pb collisions at a record energy of 5.36 TeV centre-of-mass energy per colliding nucleon pair (beam energy 6.8 Z TeV). Bunch trains created with a new production scheme in the injectors, including slip-stacking, were injected into the LHC, with the collimation of nuclear beams with bent crystals tested along with a new collimation scheme for collision products. This paper describes the conditions and outcomes of these tests, which are critical steps in the upgrade to higher luminosity.

Towards single-charge heavy ion beams driven by an ultra-intense laser

The acceleration of super-heavy ions from an ultra-thin lead target irradiated by a femtosecond laser pulse with an intensity in the range of ∼1022–1023 W cm−2 was investigated using an advanced 2D3V particle-in-cell code. It is shown that by properly selecting the laser pulse parameters, it is possible to produce a practically single-charge Pb ion beam with multi-GeV ion energies and the laser-to-ions energy conversion efficiency approaching 30%. At the laser intensity of 1023 W cm−2, Pb ions with the charge state Z = 72 carry over 90% of the total energy of all ions, while the peak intensity and peak fluence of the Pb+72 ion beam are at least two orders of magnitude higher than for other types of ions. In addition, the Pb+72 ion beam is more compact and has a smaller angular divergence than those for other types of ions. The above properties of the Pb+72 ion beam mean that further energy-efficient purification of the beam from other types of ions is possible, even in simple ion transport and selection systems.

Detailed characterisation of the LEIR intensity limitations for a Pb ion beam

The equilibrium emittance of the Pb beam in the CERN Low Energy Ion Ring (LEIR) results from the interplay of electron cooling and heating processes, as intra-beam scattering and space charge. In this paper we present the measurements of the emittance evolution as a function of intensity, working point and resonance excitation, and compare them with the simulations of the heating processes. Optimum settings for normal and skew sextupoles have been found for the compensation of resonances excited by the lattice.

Recent Beam Performance Achievements with the Pb-Ion Beam in the SPS for LHC Physics Runs

Recent Beam Performance Achievements with the Pb-Ion Beam in the SPS for LHC Physics Runs

Electromagnetic processes in ultra-peripheral Pb+Pb collisions with ATLAS

The large equivalent-photon fluxes accompanying Pb ion beams at the LHC initiate photon–photon interactions, which occur when the colliding nuclei have large impact parameter (ultra-peripheral collisions). The ATLAS collaboration has carried out a range of measurements related with two-photon interactions at high energies using recently recorded Pb+Pb collision data taken at sNN=5.02 TeV.

XPS-and-DFT analyses of the Pb 4f — Zn 3s and Pb 5d — O 2s overlapped ambiguity contributions to the final electronic structure of bulk and thin-film Pb-modulated zincite

The electronic structures of zincite Pb-modulated bulk and thin-films were studied via X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) techniques. Both XPS data and DFT-calculations allowed the derivation of two different Pb-embedding scenarios into the ZnO-hosts. These included the high-interaction mode of Pb-impurity with initial zinc-oxygen host-lattice for the bulk morphology, accompanied with low Pb-metal losses; and the low-interaction mode for thin-films, where there was intake of Pb-impurities into the hollows of the surface. Despite dissimilar mechanisms of Pb-impurity accumulation and distribution in the bulk and thin-films zincite host-matrices, the strong Pb 4f — Zn 3s and Pb 5d — O 2s overlapped ambiguity contribution to the appropriate core-level structure and valence bands was established by XPS analysis and reproduced with the help of DFT-calculations. It was shown that the microscopic structure of the embedded lead-impurity played a crucial role in the Pb ion-beam stimulated synthesis of secondary lead-oxygen phases via large-area defect fabrication, and the difference among zincite and wurzite polymorphs played almost no role in this case.

Comparative results on collimation of the SPS beam of protons and Pb ions with bent crystals

New experiments on crystal assisted collimation have been carried out at the CERN SPS with stored beams of 120 GeV/c protons and Pb ions. Bent silicon crystals of 2 mm long with about 170 μrad bend angle and a small residual torsion were used as primary collimators. In channeling conditions, the beam loss rate induced by inelastic interactions of particles with the crystal nuclei is minimal. The loss reduction was about 6 for protons and about 3 for Pb ions. Lower reduction value for Pb ions can be explained by their considerably larger ionization losses in the crystal. In one of the crystals, the measured fraction of the Pb ion beam halo deflected in channeling conditions was 74%, a value very close to that for protons. The intensity of the off-momentum halo leaking out from the collimation station was measured in the first high dispersion area downstream. The particle population in the shadow of the secondary collimator–absorber was considerably smaller in channeling conditions than for amorphous orientations of the crystal. The corresponding reduction was in the range of 2–5 for both protons and Pb ions.

Measurements of heavy ion beam losses from collimation

The collimation efficiency for Pb ion beams in the LHC is predicted to be lower than requirements. Nuclear fragmentation and electromagnetic dissociation in the primary collimators create fragments with a wide range of Z/A ratios, which are not intercepted by the secondary collimators but lost where the dispersion has grown sufficiently large. In this article we present measurements and simulations of loss patterns generated by a prototype LHC collimator in the CERN SPS. Measurements were performed at two different energies and angles of the collimator. We also compare with proton loss maps and find a qualitative difference between Pb ions and protons, with the maximum loss rate observed at different places in the ring. This behavior was predicted by simulations and provides a valuable benchmark of our understanding of ion beam losses caused by collimation.

In-situ analysis of Pb isotope ratios using laser ablation MC-ICP-MS: Controls on precision and accuracy and comparison between Faraday cup and ion counting systems

This contribution compares in-situlaser ablation multicollector ICP-MS (LA-MC-ICP-MS) measurements of Pb isotope composition using parallel Faraday cup and ion counter detector array to those made using solely Faraday cups. In the former configuration ion counting is used for the low abundance isotope 204Pb as well as 200Hg and 202Hg isotopes required for correction of isobaric interference of 204Hg. Accurate measurement of the differences in gain between ion counters and Faraday cups, required for determination of 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios using ion counting, can be made by analysis of standard glasses to within ±0.3% (2s). For analyses made using Faraday cups or combined Faraday cup and ion counting detector arrays mass bias is effectively controlled by external normalization to 208Pb/206Pb ratios measured in the same standard glasses. Provided that He sweep gas flow rates are kept constant and that adequate time is allowed for stabilization after changes in He flow, mass bias can be controlled to within ±0.05% (2s). The precision of measurements of Pb isotope ratios is strongly dependent on ion beam intensities. Internal precision of ≤ 0.02% (2se) on 208Pb/206Pb and 207Pb/206Pb ratios requires ∑Pb ion beam intensity of > ∼30–50 mV. At beam intensities ∼200 mV, equivalent to ∼100 000 counts per second (cps) 204Pb. Correction for 204Hg interference does not substantially contribute to uncertainty as long as 204Hg comprises less than ∼20% of the total 204 ion beam.

20 years of J/ $\psi$ suppression at the CERN SPS

J/\(\psi\) suppression was predicted to be a signature of deconfinement and has been extensively studied at the CERN-SPS in proton, light and heavy ion induced reactions. Indeed, proton, O, S and Pb ion beams, at various incident energies, have been used at CERN on different targets, in order to precisely quantify J/\(\psi\) production as a function of both the colliding nuclei and the centrality of the collision itself. This paper reviews the results obtained so far with a critical discussion of the experimental conditions and successive improvements implemented for the various data samples. It makes a tentative summary of what has been learned on the subject, from the experimental point of view, in the SPS energy range.

Conducting versus insulating walls in a heavy ion reaction chamber

We first pay attention to the inflight charge state distribution in a Pb ion beam propagating in a reactor-sized chamber delimited by metallic walls. We thus compare Livermore (code BIC) and Orsay (code BPIC) distributions in the presence of a residual Flibe gas pressure. Next, we replace the electron plasma due to Flibe ionization by a gliding plasma produced by the polarization of the incoming ion beam on insulating walls. Corresponding electrons, when attracted by the beam, are demonstrated to yield a very efficient current neutralization.

Dose rate and temperature effects in radiation disorder creation in SrTiO 3

An important aspect of assessing the physical and chemical stability of SrTiO 3 phase under radiation is to evaluate the disorder caused by α-decays in the actinide loaded nuclear waste form during the repository time. Indeed, radiation can affect considerably the chemical durability of the solid waste forms, especially for α-emitter immobilisation. It is already known that amorphisation in SrTiO 3 can be described at room temperature, by the cascade-overlap model with an additional term representing the initial disorder creation. In the present work, it is shown by using Pb-ion beam to simulate the α-recoil nuclei for creating the disorder that Pb-dose rate and sample temperature during irradiation are two important factors that affect SrTiO 3 susceptibility to proceed toward amorphisation.

A new ultra radiation hard cryogenic silicon tracker for heavy ion beams

We have designed and built a new hodoscope for heavy ion beams consisting of two tracking stations equipped with silicon microstrip detectors operated at 130 K. Preliminary results from tests performed in the high intensity CERN-SPS Pb ion beam show that we were able to detect and identify each incoming ion up to a beam intensity of ∼10 7 ions/s. The beam profile could be monitored on-line with 50 μm resolution. The detector performed satisfactory even after a dose of 90±40 Grad.

Simulation techniques for heavy ion fusion chamber transport

Heavy ion-driven inertial confinement fusion requires efficient transport of the ion beam over several meters from the entrance of the accelerator to the target. Currently considered transport modes with high perveance beams require significant charge and current neutralization that will likely require pre-existing dense plasmas. We have developed a hybrid implicit algorithm to treat dense plasmas accurately. Using this algorithm, simulations of neutralized ballistic transport show improved transport efficiency for a 4-GeV, 4-kA Pb ion beam by including a 10 13 cm −3 plasma at initialization.

A new monitoring system for the photon spectrometer LEDA in the WA98 experiment

Abstract We report on the design, construction, and test of a new gain monitoring system developed for the 10 000-module lead-glass calorimeter in the WA98 experiment. The system combines precision monitoring and modularity according to the general detector design. It is based on pulsed LEDs and photodiodes. The complete system was successfully used in an electron calibration and during the first Pb-ion beam time at the CERN SPS.