23121089
A comparison and benchmark of two electron cloud packages
We present results from precision simulations of the electron cloud (EC) problem in the Fermilab Main Injector using two distinct codes. These two codes are (i)POSINST, a F90 2D+ code, and (ii)VORPAL, a 2D/3D electrostatic and electromagnetic code used for self-consistent simulations of plasma and particle beam problems. A specific benchmark has been designed to demonstrate the strengths of both codes that are relevant to the EC problem in the Main Injector. As differences between results obtained from these two codes were bigger than the anticipated model uncertainties, a set of changes to the POSINST code were implemented. These changes are documented in this note. This new version of POSINST now gives EC densities that agree with those predicted by VORPAL, within {approx}20%, in the beam region. The root cause of remaining differences are most likely due to differences in the electrostatic Poisson solvers. From a software engineering perspective, these two codes are very different. We comment on the pros and cons of both approaches. The design(s) for a new EC package are briefly discussed.
16599712
Comparison of tracking codes for the International Linear Collider
In an effort to compare beam dynamics and create a "benchmark" for Dispersion Free Steering (DFS) a comparison was made between different International Linear Collider (ILC) simulation programs while performing DFS. This study consisted of three parts. Firstly, a simple betatron oscillation was tracked through each code. Secondly, a set of component misalignments and corrector settings generated from one program was read into the others to confirm similar emittance dilution. Thirdly, given the same set of component misalignments, DFS was performed independently in each program and the resulting emittance dilution was compared. Performance was found to agree exceptionally well in all three studies.
1161525
Recent studies of dispersion matched steering for the ILC bunch compressor and main linac
The dispersion matched steering (DMS) method is studied in detail in the context of a curved main linac. In the absence of cavity tilts (rotations in the YZ plane), DMS provides a unique and stable solution with negligible emittance growth. If cavity tilts are about 300 murad, the algorithm is not very robust. The emittance growth through the entire linac for positrons is about 5 nm, if the system is strictly static and statistical averaging can be used to improve beam position measurements. This growth is mostly eliminated if the dispersion and its derivative at injection can be adjusted. If anticipated ground motion, beam and klystron jitter, beam position measurement resolution are introduced (i.e. dynamical case), the emittance preservation goal is currently not achieved by DMS alone. Mitigation strategies are outlined.
116622236
Beam simulation tools for GEANT4 (and neutrino source applications)
Geant4 is a tool kit developed by a collaboration of physicists and computer professionals in the High Energy Physics field for simulation of the passage of particles through matter. The motivation for the development of the Beam Tools is to extend the Geant4 applications to accelerator physics. Although there are many computer programs for beam physics simulations, Geant4 is ideal to model a beam going through material or a system with a beam line integrated to a complex detector. There are many examples in the current international High Energy Physics programs, such as studies related to a future Neutrino Factory, a Linear Collider, and a very Large Hadron Collider.
62352767
ASPECTS OF SCIENTIFIC VISUALIZATION FOR HEP ANALYSIS AT FERMILAB
33125511
Beam-Beam Effects in the Tevatron Run II
Electromagnetic long-range and head-on interactions of high intensity proton and antiproton beams are significant sources of beam loss and lifetime limitations in the Tevatron Collider Run II (2001-present). We present observations of the beam-beam phenomena in the Tevatron and results of relevant beam studies. We analyze the data and various methods employed in high energy physics (HEP) operation, predict the performance for planned luminosity upgrades and discuss ways to improve it.
121510080
Design concept and first experimental validation of the superfluid helium system for the Large Hadron Collider (LHC) project at CERN
Abstract The superconducting magnets of the CERN Large Hadron Collider (LHC) project must be kept at their operating temperature of 1.9 K all around the 26.7 km circumference of the machine ring. For this purpose, they are immersed in static baths of pressurized helium II, acting as heat transport medium to a heat exchanger tube running along the magnet string, in which flowing saturated helium II absorbs the deposited heat at constant temperature. Proper operation of this cooling scheme requires stability of the two-phase helium flow and adequate heat transport across the helium II heat exchanger. To investigate these issues, we have conducted tests on heated two-phase flow of saturated helium II in a 24 m long tube simulating the magnet heat exchanger.
121140490
Investigation of quench pressure transients in the LHC superconducting magnets
Abstract In case of resistive transition of a LHC superconducting magnet (“quench”), the stored energy is dissipated in the winding within a few tenths of a second. A fraction of this energy is transferred to the helium inside the windings and around the beam tubes, causing expansion and axial flow. This results in a fast pressure peak (several MPa) at the midlength of the magnet. We present a one-dimensional thermo-hydraulic model aiming at simulation of the quench pressure peak and study the influence of geometrical parameters, such as magnet length and beam pipe diameter. Results of simulations are compared to measurements performed on a short model and on a quasi-full scale prototype of the LHC dipoles.
115247833
Progress in construction of the LHC
118077361
The Superfluid Helium Cryogenic System for the LHC Test String: Design, Construction and First Operation
A major milestone in the preparation of the Large Hadron Collider (LHC) project is the testing and operation of a 50-m long superconducting magnet string, representing a half-cell of the machine lattice. This also corresponds to the length of the elementary cooling loops providing refrigeration at the 1.9 K, 4.5-to-20 K, and 50-to-75 K levels to the LHC cryomagnets. Based on existing large-capacity cryogenic infrastructure, we have designed, built and are operating a dedicated cryogenic system feeding the LHC Test String, with installed capacities of 120 W @ 1.8 K and 10 g/s supercritical helium at 4.5 K. The system also includes 15 kA, 1.6 kA, 500 A, 250 A and 50 A current lead pairs for powering of main and auxiliary magnet circuits, as well as a 120 kW liquid nitrogen vaporizer for controlled cooldown of the 105 kg cold mass. The system is fully instrumented, controlled by dedicated industrial PLCs connected to an industrial supervision system. We report on performance in operation, including response of the system to transients such as current ramp and discharge, as well as magnet resistive transitions.
197436486
CLIC e+e- Linear Collider Studies
This document provides input from the CLIC e+e- linear collider studies to the update process of the European Strategy for Particle Physics. It is submitted on behalf of the CLIC/CTF3 collaboration and the CLIC physics and detector study. It describes the exploration of fundamental questions in particle physics at the energy frontier with a future TeV-scale e+e- linear collider based on the Compact Linear Collider (CLIC) two-beam acceleration technique. A high-luminosity high-energy e+e- collider allows for the exploration of Standard Model physics, such as precise measurements of the Higgs, top and gauge sectors, as well as for a multitude of searches for New Physics, either through direct discovery or indirectly, via high-precision observables. Given the current state of knowledge, following the observation of a \sim125 GeV Higgs-like particle at the LHC, and pending further LHC results at 8 TeV and 14 TeV, a linear e+e- collider built and operated in centre-of-mass energy stages from a few-hundred GeV up to a few TeV will be an ideal physics exploration tool, complementing the LHC. Two example scenarios are presented for a CLIC accelerator built in three main stages of 500 GeV, 1.4 (1.5) TeV, and 3 TeV, together with the layout and performance of the experiments and accompanied by cost estimates. The resulting CLIC physics potential and measurement precisions are illustrated through detector simulations under realistic beam conditions.