Papers by Ralph J . Steinhagen
LHC-Performance- …, 2008
A series of LHC injection tests was performed in August and September 2008. The first saw beam in... more A series of LHC injection tests was performed in August and September 2008. The first saw beam injected into sector 23; the second into sectors 78 and 23; the third into sectors 78-67 and sectors 23-34-45. The fourth, into sectors 23-34-45, was performed the ...
Emittance measurements through the 2012 LHC proton cycle examined possible major sources for the ... more Emittance measurements through the 2012 LHC proton cycle examined possible major sources for the large blowup through the LHC cycle already seen in 2011. The behavior of single bunch and 50 ns beams from LHC injection to collisions has been investigated. Accuracy and limitations of the LHC transverse profile monitors will be discussed. The effect of 50 Hz noise on the emittance growth and the influence of different transverse damper gains are presented. Intra beam scattering is one of the major sources of blow-up in the horizontal plane at injection. RF batch-by-batch blow-up has been put into operation towards the end of the year to counteract this effect. The impact of these measures on specific luminosity will be presented. The creation of tails through the LHC cycle will also be briefly discussed and an outlook for future LHC upgrade scenarios with low emittance beams will be given. INTRODUCTION Measurement campaigns during the 2011 proton run revealed substantial transverse emi...
Proceedings of the 2005 Particle Accelerator Conference
The transverse impedance of the LHC collimators will likely dominate the overall transverse imped... more The transverse impedance of the LHC collimators will likely dominate the overall transverse impedance in the LHC at high energies and potentially limit the maximum intensity. A prototype collimator was recently tested in the SPS. Small, but significant tune shifts depending on the collimator position have been observed using different independent high resolution tune measurement methods. In addition trapped modes predicted from numerical simulation at the ends of the collimator jaws have been identified by bench measurement techniques as well as with the beam. We present a description of the measurements and an analysis of the results.
About 30 % of the potential luminosity performance is lost through the different phases of the LH... more About 30 % of the potential luminosity performance is lost through the different phases of the LHC cycle, mainly due to transverse emittance blow-up. Measuring the emittance growth is a difficult task with high intensity beams and changing energies. Improvements of the LHC transverse profile instrumentation helped to study various effects. A breakdown of the growth through the different phases of the LHC cycle is given as well as a comparison with the data from the LHC experiments for transverse beam size. In 2012 a number of possible sources and remedies have been studied. Among these are intra beam scattering, 50 Hz noise and the effect of the transverse damper gain. The results of the investigations are summarized in this paper. Requirements for transverse profile instrumentation for post LHC long shutdown operation to finally tackle the emittance growth are given as well.
2007 IEEE Particle Accelerator Conference (PAC), 2007
The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most... more The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
Some of the upgrade scenarios of the high-luminosity LHC require large intensity per bunch from t... more Some of the upgrade scenarios of the high-luminosity LHC require large intensity per bunch from the injector chain. Single bunch beams with intensities of up to 3.5 to 4e11 p/b and nominal emittances were successfully produced in the PS Complex and delivered to the SPS in 2010. This contribution presents results of studies with this new intense beam in the SPS to probe single bunch intensity limitations with nominal gamma transition. In particular, the vertical Transverse Mode Coupling Instability (TMCI) threshold with low chromaticity was observed at 1.6e11 p/b for single nominal LHC bunches in the SPS. With increased vertical chromaticity, larger intensities could be injected, stored along the flat bottom and accelerated up to 450 GeV/c. However, significant losses and/or transverse emittance blow up were then observed. Longitudinal and transverse optimization efforts in the PSB, PS and SPS were put in place to minimize this beam degradation and succeeded to obtain single 2.5e11 p/b LHC type bunches with satisfying parameters at extraction of the SPS.
The accurate graphical representation of accelerator- or beam-based parameters is crucial for com... more The accurate graphical representation of accelerator- or beam-based parameters is crucial for commissioning and operation in any modern accelerator. Charts are one of the most visible but at the same time often underappreciated accelerator control system components even though these are crucial for easing and improving a quick intuitive understanding of complex or large quantities of data, which in turn is used to efficiently control, troubleshoot or improve the accelerator performance. While the Java SDK and other third-party libraries provide some charting components, we found that these lack either functionality, performance, or are based on outdated complex APIs. Based on earlier GSI and CERN designs and careful analysis of missing functionalities, performance bottlenecks, and long-term maintenance risks for the necessary workarounds, we decided that it was worth to re-engineer a new scientific charting library that preserves the functionality of established other libraries whil...
The ’Facility for Anti-Proton and Ion Research’ (FAIR) presently under construction, extends and ... more The ’Facility for Anti-Proton and Ion Research’ (FAIR) presently under construction, extends and supersedes GSI’s existing infrastructure. Its core challenges include the precise control of highest proton and uranium ion beam intensities, the required extreme high vacuum conditions, machine protection and activation issues while providing a high degree of multi-user mode of operation with facility reconfiguration on time-scales of a few times per week. To optimise turn-around times and to establish a safe and reliable machine operation, a comprehensive suite of semi-automated measurement applications, as well as fullyautomated beam-based feedbacks will be deployed, covering the control of orbit, Q/Q’, spill structure, optics, and other machine parameters. These systems are based on the LSA settings management framework, code-shared with and also used at CERN. The concepts, software architecture and first prototype beam tests at the SIS18 in 2016 are presented. As an initial proof-of...
An improved understanding of intra-bunch instabilities in synchrotron light source electron bunch... more An improved understanding of intra-bunch instabilities in synchrotron light source electron bunches is crucial to overcoming the imposed limitations of the achievable intensity. A Multiband Instability Monitor, designed specifically for the short bunches of a synchrotron light source, has been developed to perform measurements of intra-bunch dynamics. The MIM performs real-time measurements at a diagnostic beamline using optical synchrotron radiation incident on a high speed photodetector. Three frequency bands up to 12 GHz were used to identify characteristic frequency signatures of intra-bunch instabilities. Mixed to baseband using RF detectors, these high frequency measurements can be performed without the need for similarly high frequency digitisers. This paper reports on the performance of the system at the Australian Synchrotron.
Accelerator Operations
Accelerators and Colliders, 2013
First field test of FiDeL The magnetic field description for the LHC
The start-up of the LHC has provided the first field test for the concept, functionality and accu... more The start-up of the LHC has provided the first field test for the concept, functionality and accuracy of FiDeL, the Field Description for the LHC. FiDeL provides the parametric model of the transfer function of the main field integrals generated by the series of magnets in the ...
The cost of building a particle accelerator is a major capital investment. Commissioning should b... more The cost of building a particle accelerator is a major capital investment. Commissioning should be swift and the subsequent exploitation of a facility must provide an effective return. This return may be difficult to quantify unambiguously but generally acceptable measures of performance can be established. These measures might include: machine availability; integrated luminosity; protons on target; beam hours to users and so on. The role of accelerator operations is to maximize the performance of an accelerator or accelerator complex by: minimizing downtime; maximizing the amount of beam delivered to the users; fully optimizing the quality of beam delivered to the users; and doing it all safely. Accelerators and the control of particles beams have advanced considerably over recent years. There is deep understanding of particle dynamics, innovative measurement techniques, in-depth simulation and modelling, and widespread leverage of Coordinated by M. Lamont.
The relation between field and current in each family of the Large Hadron Collider magnets is mod... more The relation between field and current in each family of the Large Hadron Collider magnets is modeled with a set of empirical equations (FiDeL) whose free parameters are fitted on magnetic measurements. They take into account of residual magnetization, persistent currents, hysteresis, saturation, decay and snapback during initial part of the ramp. Here we give a first summary of the reconstruction of the magnetic field properties based on the beam observables (orbit, tune, coupling, chromaticity) and a comparison with the expectations based on the large set of magnetic measurements carried out during the 5-years-long production. The most critical issues for the machine performance in terms of knowledge of the relation magnetic field vs current are pinned out.
An upgrade of LHC beam instrumentation has been performed during the Long Shutdown 1. In this con... more An upgrade of LHC beam instrumentation has been performed during the Long Shutdown 1. In this context both the beam position and tune monitoring systems, as well as their respective feedback systems have been reviewed and modified. This contribution presents an overview of the major hardware and software modifications performed during LS1 and the expected performance with 6.5TeV beams in 2015.
What You Get" - Orbit and tune measurements and feedback
The Large Hadron Collider (LHC) has now been operated successfully for 3 years relying on the goo... more The Large Hadron Collider (LHC) has now been operated successfully for 3 years relying on the good performance of its beam instrumentation, including position and tune monitors and their respective feedback systems. This contribution gives an overview of the performance and limitations of the current orbit and tune systems. The major hardware and software modifications performed in 2012 are presented as well as the developments and improvements planned during the Long Shutdown 1 (LS1). The last part of the paper discusses the expected performances of both systems with 6.5TeV beams after LS1
The proposed SPS Wideband Transverse Feedback sys- tem requires a wide-band pick-up system to be ... more The proposed SPS Wideband Transverse Feedback sys- tem requires a wide-band pick-up system to be able to de- tect intra-bunch motion within the SPS proton bunches, captured and accelerated in a 200 MHz bucket. We present the electro-magnetic design of transverse beam position pick-up options optimised for installation in the SPS and evaluate their performance reach with respect to direct time domain sampling of the intra-bunch motion. The analy- sis also discusses the achieved subsystem responses of the associated cabling with new low dispersion smooth wall coaxial cables, wide-band generation of intensity and posi- tion signals by means of 180 degree RF hybrids as well as passive techniques to electronically suppress the beam off- set signal, needed to optimise the dynamic range and posi- tion resolution of the planned digital intra-bunch feedback system.
BPM: status, measurement reliability and outlook for 2011
The Achromatic Telescopic Squeezing (ATS) scheme is a novel squeezing mechanism enabling the prod... more The Achromatic Telescopic Squeezing (ATS) scheme is a novel squeezing mechanism enabling the production of very low β* in circular colliders. The basic principles of the ATS scheme will be reviewed together with its strong justification for the High-Luminosity LHC Project. In this context, a few dedicated experiments with beam were meticulously prepared and took place at the LHC in
Injection into LHC of single bunches with nominal intensity
As part of the 2010 LHC commissioning, the intensity of a single INDIV injected bunch was increas... more As part of the 2010 LHC commissioning, the intensity of a single INDIV injected bunch was increased from 1×10 10 to 1.1×10 11 . The injection protection systems TDI and TCDI were first set up around the beam to their nominal settings, and preliminary tests with high intensity bunches to the transfer line TEDs were made to verify the beam stability and transverse profiles. The machine protection system requires overinjection of the beam onto a low intensity circulating beam, which was also commissioned. This note briefly describes the problems encountered together with the main results, and lists the issues which remain to be solved.
Following intensive numerical simulations to compute the dynamic aperture for the LHC in the desi... more Following intensive numerical simulations to compute the dynamic aperture for the LHC in the design phase, the successful beam commissioning and the ensuing beam operations opened the possibility of performing beam measurements of the dynamic aperture. In this paper the experimental set-up and the first observations based on the few experimental sessions performed will be presented and discussed in details.
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Papers by Ralph J . Steinhagen