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The Beam-Gas Curtain or BGC is the baseline instrument for monitoring the concentricity of the LHC proton beam with a hollow electron beam for the hollow e-lens (HEL) beam halo suppression device which is part of the High-Luminosity LHC upgrade. The proof-of-principles experiments of this gas-jet monitor have now been developed into a prototype instrument which has been built for integration into the LHC ring and is now under phased installation for operation in the upcoming LHC run. This paper describes the challenges overcome to produce a gas-jet fluorescence monitor for the ultra-high vacuum accelerator environment. It also presents preliminary results from the installation of the instrument at CERN., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

A gas jet beam profile monitor was designed for measuring the electron beam at the electron beam test stand (EBTS) for the Hollow electron lens (HEL) and the proton beam in the large hadron collider (LHC). It is partially installed in the LHC during the second long shutdown. The current monitor is tailored to the accelerator environment including vacuum, geometry, and magnetic field for both the EBTS and the LHC. It features a compact design, a higher gas jet density, and a wider curtain size for a better integration time and a larger detecting range. In this contribution, the commissioning of this monitor at the Cockcroft Institute will be discussed., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

In a gas jet monitor, a supersonic gas curtain is injected into the beam pipe and interacts with the charged particle beam. The monitor exploits fluorescence induced by beam-gas interactions, thus providing a minimally invasive transverse profile measurement. Such a monitor is being developed as part of the High Luminosity LHC upgrade at CERN. As a preliminary study, the fluorescence cross section of relevant gases must be measured for protons at 450 GeV and 6.8 TeV (i.e. the LHC injection and flat top energies). In these measurements, neon, or alternatively nitrogen gas, will be injected into the LHC vacuum pipe by a regulated gas valve to create an extended pressure bump. This work presents the optical detection system that was installed in 2022 in the LHC to measure luminescence cross-section and horizontal beam profile. Preliminary measurements of background light and first signals are presented in this paper., Proceedings of the 11th International Beam Instrumentation Conference, IBIC2022, Kraków, Poland

A dedicated proton injector Linac (pLinac) for the Facility of Antiproton and Ion Research (FAIR) at GSI, Darmstadt, is currently under construction. It will pro-vide a 68 MeV, up to 70 mA proton beam at a duty cycle of max. 35µs / 4 Hz for the SIS18 synchrotron, using the UNILAC transfer beamline. After further acceleration in SIS100, the protons are mainly used for antiproton production at the Antiproton Annihilation Darmstadt (PANDA) experiment. The Linac will operate at 325 MHz and consists of a novel so called ’Ladder’ RFQ type, followed by a chain of CH-cavities, partially coupled by rf-coupling cells. In this paper we present the beam diagnostics system for the pLinac with special emphasis on the Secondary Electron Emission (SEM) Grids and the Beam Position Monitor (BPM) system. We also describe design and status of our diagnostics testbench for stepwise Linac commissioning, which includes an energy spectrometer with associated optical system. The BPMs and SEM grids have been tested with proton and argon beam during several beamtimes in 2022. The results of these experiments are presented., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

Gas jet based profile monitors inject a usually curtain shaped gas jet across a charged particle beam and exploit the results of the minimally invasive beam-gas interaction to provide information about the beam’s transversal profile. Such monitor will be installed as part of the High Luminosity LHC upgrade at CERN in the Hollow Electron Lens (HEL). The HEL represents a new collimation stage increasing the diffusion rate of halo particles by placing a high intensity hollow electron beam concentrically around the LHC beam. The gas jet monitor will use the fluorescence radiation resulting due to the beam-gas interaction to create an image of the profiles of both hollow electron and LHC beams However, the high beam space-charge and strong guiding magnetic field of the electron beam cause significant displacements of the excited molecules, as they are also ionized, and thus image distortions. This work presents preliminary simulation results showing expected fluorescence images of the hollow electron profile as affected by space-charge and guiding fields using simulation tools such as IPMsim. The influence of the estimated electron beam and gas jet curtain parameters are investigated., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

A Hollow Electron Lens (HEL) is currently under development for the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC). In this device, a hollow electron beam co-propagates with a central proton beam and provides active halo control in the LHC. To ensure the concentricity of the two beams, a non-invasive diagnostic instrument is currently being commissioned. This instrument is a compact version of an existing prototype that leverages beam induced fluorescence with supersonic gas curtain technology. This contribution includes the design features of this version of the monitor, recent progress, and future plans for tests at the Cockcroft Institute and the electron lens test stand at CERN., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

For the planned antiproton experiments at FAIR a dedicated proton injector Linac is currently under construction. It will be connected via the old UNILAC transfer beamline to SIS18 and has a length of ~30 m. The Linac will accelerate protons up to a final energy of 68 MeV, at a pulse length of 35 µs and a maximum repetition rate of 4 Hz. It will operate at 325 MHz and consists of a new so called "Ladder" RFQ type, followed by a chain of CH-cavities, partially coupled by rf-coupling cells. We have worked out a diagnostics system, which allows detailed measurement and study of all beam parameters during commissioning and later during regular operation. The diagnostics devices will - in a first step - be installed on a diagnostics testbench for stepwise commissioning. We present the concepts for Linac and testbench with some special emphasis on energy measurements with spectrometer and SEM Grid profile measurements., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

For the high-luminosity upgrade of the Large Hadron Collider, active control of proton/ion beam halo will be essential for safe and reliable operation. Hollow Electron Lenses can provide such active control by enhancing the depletion of halo particles, and are now an integral part of the high luminosity LHC collimation system. The centring of the proton beam within the hollow electron beam will be monitored through imaging the fluorescence from a curtain of supersonic gas. In this contribution we report on the recent progress with this monitor and its subsystems, including the development of an LHC compatible gas-jet injection system, the fluorescence imaging setup and preliminary test measurement in the LHC, Proceedings of the 9th International Beam Instrumentation Conference, IBIC2020, Santos, Brazil

Non-destructive beam profile monitoring is very desirable, essentially for any particle accelerator but particularly for high-energy and high-intensity machines. Supersonic gas jet-based monitors, detecting either the ionization or fluorescence of a gas sheet interacting with the primary beam to be characterized, allow for minimally invasive measurements. They can also be used over a wide energy range, from keV to TeV beams. This contribution gives an overview of the jet-based ionization and fluorescence beam profile monitors which have been developed, built and tested at the Cockcroft Institute. It discusses gas sheet generation, vacuum considerations, choice of gas species and detection methods., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

A new supersonic gas-jet curtain based beam profile monitor is under development for minimally invasive simultaneous transverse profile diagnostics of proton and electron beams, at pressures compatible with LHC. The monitor makes use of a thin gas-jet curtain angled at 45 degrees with respect to the charged particle beams. The fluorescence caused by the interaction between the curtain and the beam can then be detected using a dedicated imaging system to determine its transverse profile. This contribution details design features of the monitor, discusses the gas-jet curtain formation and presents various experimental tests, including profile measurements of an electron beam using nitrogen and neon curtains. The gas-jet density was estimated by correlating it with the number of photons detected by the camera. These measurements are then compared with results obtained using a movable pressure gauge. This monitor has been commissioned in collaboration with CERN, GSI and the University of Liverpool. It serves as a first prototype of a final design that will be placed in the LHC beam line to measure the profile of the proton beam., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

High luminosity upgrades to the LHC at CERN and future energy frontier machines will require a new generation of minimally invasive profile measurement instruments. Production of a dense, focussed gas target allows beam-gas fluorescence to be exploited as an observable, giving an instrument suitable for installation even in regions of high magnetic field. This paper describes the development of a device based on these principles that would be suitable for operation in the LHC. It focusses on mechanisms for the production of a homogeneous gas curtain, the selection of an appropriate working gas and the optical fluorescence detection system., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

A dedicated proton injector for FAIR (the pLinac) is presently under construction at GSI Darmstadt. This accelerator is designed to deliver a beam current of up to 70 mA with a final energy of 68 MeV for the FAIR anti-proton program. For the commissioning of the pLinac a movable beam diagnostics test bench will be used to characterize the proton beam at different locations during the stepwise installation. The test bench will consist of all relevant types of diagnostic devices as BPM’s, ACCT’s, SEM grids, a slit-grid emittance device and a bunch shape monitor. Moreover, a magnetic spectrometer is supposed to measure the energy spread of the proton beam. Point-to-point imaging is foreseen to enable high energy resolution independently on the transverse emittance. Due to the limited space in the accelerator tunnel a special design must be chosen with the inclusion of quadrupole magnets. The present contribution gives an overall presentation of the test bench and its devices with a special emphasis on the magnetic spectrometer design., Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

A hollow electron lens is presently under study as a possible addition to the collimation system for the high luminosity upgrade of the LHC (HL-LHC), while an electron lens system is also proposed for space charge compensation in the SIS-18 synchrotron for the high intensities at the future FAIR facility. For effective operation, a precise alignment is necessary between the high energy hadron beam and the low energy electron beam. In order to achieve this, a beam diagnostics setup based on an intersecting gas sheet and the observation of beam-induced fluorescence is under development. In this contribution we give an account of the design and performance of the optical detection system and report on recent preparatory experiments performed using a laboratory gas curtain Setup., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

The High-Luminosity Large Hadron Collider (HL-LHC) project aims to increase the machine luminosity by a factor of 10 as compared to the LHC's design value. To achieve this goal, a special type of electron lens is being developed. It uses a hollow electron beam which co-propagates with the hadron beam to act on any halo particles without perturbing the core of the beam. The overlapping of both beams should be carefully monitored. This contribution presents the design principle and detailed characteristics of a new supersonic gas jet-based beam profile monitor. In contrast to earlier monitors, it relies on fluorescence light emitted by the gas molecules in the jet following interaction with the primary hadron beams. A dedicated prototype has been designed and built at the Cockcroft Institute and is being commissioned. Details about monitor integration, achievable resolution and dynamic range will be given., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Supersonic gas jets have been used in transverse beam profile monitoring as Ionization Profile Monitors (IPMs) and Beam Induced Fluorescence (BIF) monitors. The former method images ions generated by the projectile beam, whilst the latter is based on the detection of photons. This is a promising technology for use in high energy accelerators, such as the High Luminosity Large Hadron Collider (HLLHC). In this paper, the suitability of a supersonic gas jet in combination with a BIF detection system for the measurement of the transverse beam profile of a low energy electron beam is discussed. The technical layout and experimental results from measurements at a test installation at the Cockcroft Institute are also presented., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

Electron lenses (e-lens) have been proposed and used to mitigate several issues related to beam dynamics in high current synchrotrons. A hollow electron lens system is presently under development as part of the collimation upgrade for the high luminosity up-grade of LHC. Moreover, at GSI an electron lens system also is proposed for space charge compensation in the SIS-18 synchrotron to decrease the tune spread and allow for the high intensities at the future FAIR facility. For effective operation, a very precise alignment is necessary between the ion beam and the low energy electron beam. For the e-lens at CERN a beam diagnostics setup based on an intersecting gas sheet and the observation of beam induced fluorescence (BIF) is under development within a collaboration between CERN, Cockcroft Institute and GSI. In this paper we give an account of recent preparatory experiments performed at the Cockcroft Institute's gas curtain experimental setup with the aim to find the optimum way of distinguishing between the signals due to the low energy electron beam and the relativistic proton beam., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

Nonuniformities of the extraction fields, the velocity distribution of electrons from ionization processes and strong bunch fields are just a few of the effects affecting Ionization Profile Monitor measurements and operation. Careful analysis of these phenomena require specialized simulation programs. A handful of such codes has been written independently by various researchers over the recent years, showing an important demand for this type of study. In this paper we describe the available codes and discuss various approaches to Ionization Profile Monitor simulations. We propose benchmark conditions to compare these codes between themselves and we collect data from various devices to benchmark codes against the measurements. Finally we present a community effort with a goal to discuss the codes, exchange simulation results and to develop and maintain a new, common codebase., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

Intensive Ionenstrahlen sind besonders geeignet große Volumina von hoher Energiedichte in Materie mit einer guten Homogenität der Verteilung physikalischer Parameter zu erzeugen. Die experimentelle Erforschung von Materie unter extremen Zuständen von Druck, Temperatur und Dichte ist von hohem Interesse sowohl für die Grundlagenforschung als auch für die angewandte Physik. Dazu gehören Fragen der Astrophysik, Geophysik und der Energiegewinnung mit Hilfe der Trägheitsfusion. Zur Erforschung der Materie bei hoher Energiedichte gehören insbesondere Experimente zur thermodynamischen Zustandsgleichung und zu Transporteigenschaften. Die elektrische Leitfähigkeit ist eine der fundamentalen Eigenschaften der Materie. Obwohl in den letzten Jahrzehnten das theoretische Verständnis der elektrischen Leitfähigkeit bedeutende Fortschritte gemacht hat, gibt es weiterhin keine allgemeine Theorie, welche das Verhalten dieses Transportkoeffizienten unter unterschiedlichen Bedingungen vorhersagen kann. Deswegen sind Messungen dieser Größe von besonderer Bedeutung für die Grundlagenforschung. Zum ersten Mal wurden am Hochtemperaturmessplatz (HHT) der Plasmaphysikgruppe der Gesellschaft für Schwerionenforschung (GSI) Darmstadt Messungen zur elektrischen Leitfähigkeit dichter, schwerioneninduzierter Plasmen durchgeführt. Zu diesem Zweck wurden Drahtförmige Festkörpertargets aus unterschiedlichen Materialien (Kupfer, Blei, Silber) mit hochintensiven Schwerionenstrahlen bis auf Temperaturen im Bereich von 0,1 eV innerhalb von 0.001 ms geheizt. Wegen der kurzen Heizzeit bleibt die Dichte der Targets in der Nähe der Festkörperdichte und der Druck steigt bis zu einigen kbar. Die Leitfähigkeit dieser Targets wurde mit Hilfe von am HHT neu entwickelten experimentellen Techniken untersucht. Die durchgeführten Messungen lieferten zeitaufgelöste Daten sowohl zur Änderung des elektrischen Widerstandes der Targets als auch zu ihrer hydrodynamischen Expansion, und ermöglichten dadurch die Bestimmung des spezifischen elektrischen Widerstandes, beziehungsweise der elektrischen Leitfähigkeit. Darüber hinaus wurden komplexe Simulationen durchgeführt, um theoretische Vorhersagen mit den Resultaten dieser Messungen zu vergleichen. Wir sind davon überzeugt, dass die gewonnenen Erfahrungen und entwickelten Diagnostikmethoden für zuküftige Experimente sehr wichtig sein werden, insbesondere im Rahmen des GSI Zukunftprojektes.