The European Spallation Source Design

The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H− beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

/pdf/space-charge-compensation-in-the-linac4-low-energy-beam-3gcxje3umv.pdf

Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions.

As the first step of a long-term programme aiming at an increase in the LHC luminosity, CERN is building a new 160 MeV H linear accelerator, Linac4, to replace the ageing 50 MeV Linac2 as injector to the PS Booster (PSB). Linac4 is an 86-m long normal-conducting linac made of an H source, a Radio Frequency Quadrupole (RFQ), a chopping line and a sequence of three accelerating structures: a Drift-Tube Linac (DTL), a CellCoupled DTL (CCDTL) and a Pi-Mode Structure (PIMS). The civil engineering has been recently completed, and construction of the main accelerator components has started with the support of a network of international collaborations. The low-energy section up to 3 MeV including a 3-m long 352 MHz RFQ entirely built at CERN is in the final construction phase and is being installed on a dedicated test stand. The present schedule foresees beam commissioning of the accelerator in the new tunnel in 2013/14; the moment of connection of the new linac to the CERN accelerator chain will depend on the LHC schedule for long shut-downs. LINAC4 AND THE LHC UPGRADE The peak luminosity of the LHC has been constantly increased during its first two years of operation, reaching in 2011 about 2×10 cms. Some additional steps will be required to reach the nominal value of 10 cms and possibly exceed it, but it is clear that in a few years LHC performance will saturate because of the injectors and because of the collider itself. To overcome this limitation and extend the physics reach an intensive luminosity upgrade programme has been recently launched, aiming at important hardware modifications in the LHC interaction regions and in the injectors that have to provide beams of higher brightness and intensity [1]. Space charge effects represent a first obvious limitation, which is addressed by increasing the injection energy in the first two synchrotrons in the injection chain, starting from the PS Booster (PSB) presently fed by the 50 MeV Linac2. Because of the lack of space and of its obsolete technology an energy upgrade of Linac2 has been ruled out and instead the construction of a new linac injector for the PSB with a final energy of 160 MeV has been approved by the CERN Council in June 2007. The new linac, called Linac4 because it is the 4 hadron linac to be built at CERN, will bring other advantages related to the injection in the PSB of H instead of protons, to a modern construction technology exempt from the reliability concerns of Linac2, and to the possibility of increased beam intensity for non-LHC users. The project started in January 2008 and will be completed in 2014. DESIGN AND MAIN PARAMETERS Linac4 is dimensioned to double the maximum intensity from the PSB with the same transverse emittances, providing up to 10 protons per pulse; this charge will be supplied by 400 s long pulses at 40 mA current. The pulse repetition frequency is limited to a maximum of about 1 Hz by the PSB magnetic cycle and the duty cycle will be only 0.04%. However, in case Linac4 would be used in a future high-intensity facility for neutrino physics, the accelerating structures have been designed for a maximum duty cycle of 10%, leaving infrastructure and power supplies dimensioned only for the low duty cycle; they will have to be replaced in case the high-intensity programme is approved. Chopping of about 35% of the beam at 3 MeV is foreseen to allow low-loss injection in the PSB, bringing the required current out of the ion source to 80 mA. The 3 MeV Front end (source, LEBT, RFQ and chopper line) is followed by three normal-conducting accelerating structures all at 352 MHz, for a total linac length of 86 m (Fig. 1). Figure 1: Linac4 layout. RFQ chopper line DTL CCDTL PIMS 160 MeV 104 MeV 50 MeV 3 MeV 86 m TUOAA03 Proceedings of IPAC2011, San Sebastian, Spain 900 C op yr ig ht c ○ 20 11 by IP A C ’1 1/ E PS -A G — cc C re at iv e C om m on sA tt ri bu tio n 3. 0 (C C B Y 3. 0) 04 Hadron Accelerators A08 Linear Accelerators Three different accelerating sections allow maximising the RF efficiency minimising at the same time the construction costs; the use of superconductivity is not economically justified in this range of energy and duty cycle. A single RF frequency allows standardising the RF system with important cost savings; moreover, it is the same as in the previous LEP machine, from which a stock of klystrons, circulators and waveguides is still available.

/pdf/the-linac4-project-at-cern-256wsrnqki.pdf

The LINAC4 Project at CERN

Within the framework of the LHC Injector Upgrade (LIU), the new LINAC4 is currently being commissioned to replace the existing LINAC2 proton source at CERN. After the expected completion at the end of 2016, the LINAC4 will accelerate H − ions to 160 MeV. To measure the transverse emittance of the H − beam, a method based on photo-detachment is proposed. This system will operate using a pulsed laser with light delivered via an optical fibre and subsequently focused onto the H − beam. The laser photons have sufficient energy to detach the outer electron and create H 0 /e − pairs. In a downstream dipole, the created H 0 particles are separated from the unstripped H − ions and their distribution is measured with a dedicated detector. By scanning the focused laser beam across the H − beam, the transverse emittance of the H − beam can be reconstructed. This paper will first discuss the concept, design and simulations of the laser emittance scanner and then present results from a prototype system used during the 12 MeV commissioning of the LINAC4.

/pdf/experimental-results-of-the-laserwire-emittance-scanner-for-3e02grghda.pdf

Experimental results of the laserwire emittance scanner for LINAC4 at CERN

The European Spallation Source (ESS) [1] , to be built in the south of Sweden, will use a 2 GeV superconducting linac to produce the worlds most powerful neutron source with a beam power of 5 MW. The beam power is a challenge for interceptive beam diagnostics like wire scanner, the thermal load on intercepting devices implies to reduce the beam power in order to preserve the device integrity. For nominal operation, non-disturbing technics for profile measurements are planned, while for commissioning phase, accurate measurements and cross checking, wire scanners will be used. This paper describes the preliminary design of the wire scanner system in the normal conducing linac as well as in the superconducting linac.

Wire scanner design for the european spallation source

LINAC4 [1] is part of the CERN LHC injector chain upgrade and will accelerate H ions from 45 keV to 160 MeV. A movable diagnostics test bench will be used to adjust the machine parameters during different stages of installation. One of the main instruments on this movable bench is a transverse emittance meter. Given the beam properties at 3 MeV and 12 MeV, the slit-grid system already developed for the measurements of the transverse emittance of the 45 keV H source will not be suitable, mainly due to the high thermal load on the steel slit already with a single LINAC4 pulse. For this reason a new slit has been designed based on analytical and numerical simulations for different materials and geometries. The energy deposition patterns for the different cases have been simulated using FLUKA [2] and will be presented in detail. In addition, the choice of wires for the SEM grid will be discussed, in terms of material, diameter and spacing required, to achieve the required measurement accuracy.

/pdf/design-of-the-emittance-meter-for-the-3-and-12-mev-linac4-h-14jabapbah.pdf

Design of the Emittance Meter for the 3 and 12 MeV LINAC4 H- Beam

The CERN LINAC4 will represent the first upgrade of the LHC injection chain, by accelerating H ions from 45 KeV to 160 MeV for charge-exchange injection into the PS Booster. In order to provide its safe and efficient commissioning and operation, a wide variety of beam diagnostics devices has been designed for installation at convenient locations all over the accelerator length and in the transfer line to the PS Booster. This paper gives an overview of all instrumentation devices, including those to measure beam position, transverse and longitudinal profile, beam current and beam loss. The well advanced status of the system design and the main instrument features are discussed

/pdf/overview-of-the-cern-linac4-beam-instrumentation-466dur9q9w.pdf

Overview of the cern linac4 beam instrumentation

The H source and the low energy beam transport (LEBT) line will determine to a large extend the performance of Linac-4, the new machine foreseen at CERN as injector into the PS Booster. For this reason a test stand is being set up, consisting of the source, the LEBT, the RFQ and the chopper line. Up to now only the source and LEBT are installed. First measurements have been performed using a Faraday Cup to measure the total source intensity, a slit and grid emittance meter for transverse emittance measurements as well as a spectrometer for energy spread measurements. Beam intensity, profile, transverse emittance and energy spread have been measured. The paper discusses measurements done on H beams at 35 kV extraction voltage as well as proton beams at 45 keV. Paper presented at DIPAC2011 Conference – Hamburg/DE from 16 to 18 May 2011 FIRST RESULTS FROM BEAM MEASUREMENTS AT THE 3MEV TEST STAND FOR CERN LINAC4* B. Cheymol, CERN, Geneva, Switzerland and Universite Blaise Pascal, Clermont-Ferrand, France J.B. Lallement, A. Lokhovitsky, O. Midttun,U. Raich, F. Roncarolo, R. Scrivens, E. Zorin, CERN, Geneva, Switzerland Abstract The H source and the l ow energy beam transport (LEBT) line will d etermine to a large ex tend the performance of Linac-4 [1], the new machine foreseen at CERN as inj ector into the PS Booster. For this reason a test stand is b eing set up , consisting of the so urce, the LEBT, the RFQ and the chopper line. Up to now only the source and LEBT are installed. First m easurements have been performed using a Faraday Cup to measure the total source intensity, a slit an d grid emittance meter for transverse emittance measurements as well as a spectrometer for energy spread measurements. Beam intensity, profile, transverse emittance and energy spread have been measured. The paper discusses measurements done on H beams at 35 kV extraction voltage as well as proton beams at 45 keV.The H source and the l ow energy beam transport (LEBT) line will d etermine to a large ex tend the performance of Linac-4 [1], the new machine foreseen at CERN as inj ector into the PS Booster. For this reason a test stand is b eing set up , consisting of the so urce, the LEBT, the RFQ and the chopper line. Up to now only the source and LEBT are installed. First m easurements have been performed using a Faraday Cup to measure the total source intensity, a slit an d grid emittance meter for transverse emittance measurements as well as a spectrometer for energy spread measurements. Beam intensity, profile, transverse emittance and energy spread have been measured. The paper discusses measurements done on H beams at 35 kV extraction voltage as well as proton beams at 45 keV.

/pdf/first-results-from-beam-measurements-at-the-3-mev-test-stand-1i8lutzghk.pdf

First Results from Beam Measurements at the 3 MeV Test Stand for CERN LINAC4

The CERN LINAC4 commissioning will start in 2011, at first in a laboratory test stand where the 45 KeV H source is already installed and presently tested, and later in the LINAC4 tunnel. A movable diagnostics bench will be equipped with the necessary sensors capable of characterizing the H beam in different stages, from 3 MeV up to the first DTL tank at 12 MeV. In this paper we will discuss the accuracy of the transverse emittance measurement that will be performed with the slit-grid method. The system’s mechanical and geometric parameters have been determined in order to achieve the required resolution and sensitivity. Space charge effects during the beam transfer from the slit to the grid and scattering effects at the slit have been considered to determine the overall emittance measurement accuracy.

/pdf/accuracy-determination-of-the-cern-linac4-emittance-uyz4a2r9yr.pdf

Accuracy Determination of the CERN LINAC4 Emittance Measurements at the Test Bench for 3 and 12 MeV

As part of the CERN LHC injector chain upgrade, LINAC4 [1] will accelerate H - ions from 45 KeV to 160 MeV. A number of wire grids and wire scanners will be used to characterize the beam transverse profile. This paper covers all monitor design aspects intended to cope with the required specifications. In particular, the overall measurement robustness, accuracy and sensitivity must be satisfied for different commissioning and operational scenarios. The physics mechanisms generating the wire signals and the wire resistance to beam induced thermal loads have been considered in order to determine the most appropriate monitor design in terms of wire material and dimensions.

/pdf/wire-grid-and-wire-scanner-design-for-the-cern-linac4-3drecmvrx9.pdf

Wire grid and wire scanner design for the cern linac4

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

B Cheymol

Author Tools

Chat about Author