342 research outputs found
The application of the SXF lattice description and the UAL software environment to the analysis of the LHC
A software environment for accelerator modeling has been developed which includes the UAL (Unified Accelerator Library), a collection of accelerator physics libraries with a Perl interface for scripting, and the SXF (Standard eX-change Format), a format for accelerator description which extends the MAD sequence by including deviations from design values. SXF interfaces have been written for several programs, including MAD9 and MAD8 via the doom database, Cosy, TevLat and UAL itself, which includes Teapot++. After an overview of the software we describe the application of the tools to the analysis of the LHC lattice stability, in the presence of alignment and coupling errors, and to the correction of the first turn and closed orbit in the machine. (7 refs)
Beam Based Measurements of Field Multipoles in the RHIC Low Beta Insertions and Extrapolation of the Method to the LHC
The multipolar content of the dipoles and quadrupoles is known to limit the stability of the beam dynamics in super-conducting machines like RHIC and even more in LHC. The low-beta quadrupoles are thus equipped with correcting coils up to the dodecapole order. The correction is planned to rely on magnetic measurements. We show that a relatively simple method allows an accurate measurement of the multipolar field aberrations using the beam. The principle is to displace the beam in the non-linear fields by local closed orbit bumps and to measure the variation of sensitive beam observable. The resolution and robustness of the method are found appropriate. Experimentation at RHIC showed clearly the presence of normal and skew sextupolar field components in addition to a skew quadrupolar component in the interaction regions. Higher-order components up to decapole order appear as well
RHIC heavy ion operations performance
The Relativistic Heavy Ion Collider (RHIC) completed its fifth year of operation in 2005, colliding copper ion beams with ps=200 GeV/u and 62.4 GeV/u[1]. Previous heavy ion runs have collided gold ions at ps=130 GeV/u, 200 GeV/u, and 62.4 GeV/u[2], and deuterons and gold ions at ps=200 GeV/u[3]. This paper discusses operational performance statistics of this facility, including Cu- Cu delivered luminosity, availability, calendar time spent in physics stores, and time between physics stores. We summarize the major factors affecting operations efficiency, and characterize machine activities between physics stores
Extrasolar Trojan Planets close to Habitable Zones
We investigate the stability regions of hypothetical terrestrial planets
around the Lagrangian equilibrium points L4 and L5 in some specific extrasolar
planetary systems. The problem of their stability can be treated in the
framework of the restricted three body problem where the host star and a
massive Jupiter-like planet are the primary bodies and the terrestrial planet
is regarded as being massless. From these theoretical investigations one cannot
determine the extension of the stable zones around the equilibrium points.
Using numerical experiments we determined their largeness for three test
systems chosen from the table of the know extrasolar planets, where a giant
planet is moving close to the so-called habitable zone around the host star in
low eccentric orbits. The results show the dependence of the size and structure
of this region, which shrinks significantly with the eccentricity of the known
gas giant.Comment: 4 pages, 4 figures, submitted to A&
A study of the stability regions in the planetary system HD 74156 - Can it host earthlike planets in habitable zones?
Using numerical methods we thoroughly investigate the dynamical stability in
the region between the two planets found in HD 74156. The two planets with
minimum masses 1.56 M_JUP (HD 74156b) and 7.5 M_JUP (HD 74156c), semimajor axes
0.276 AU and 3.47 AU move on quite eccentric orbits (e=0.649 and 0.395). There
is a region between 0.7 and 1.4 AU which may host additional planets which we
checked via numerical integrations using different dynamical models. Besides
the orbital evolution of several thousands of massless regarded planets in a
three-dimensional restricted 4-body problem (host star, two planets + massless
bodies) we also have undertaken test computation for the orbital evolution for
fictive planets with masses of 0.1, 0.3 and 1 M_JUP in the region between
HD74156b and HD74156c. For direct numerical integrations up to 10^7 years we
used the Lie-integrator, a method with adaptive stepsize; additionally we used
the Fast Lyapunov Indicators as tool for detecting chaotic motion in this
region. We emphasize the important role of the inner resonances (with the outer
planet) and the outer resonances (with the inner planet) with test bodies
located inside the resonances. In these two "resonance" regions almost no
orbits survive. The region between the 1:5 outer resonance (0.8 AU) and the 5:1
inner resonance (1.3 AU), just in the right position for habitability, is also
very unstable probably due to three-body-resonances acting there. Our results
do not strictly "forbid" planets to move there, but the existence of a planet
on a stable orbit between 0.8 and 1.3 AU is unlikely.Comment: submitted to A&A, 4 pages, 5 figure
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Preparing accelerator systems for the RHIC sextant commissioning
The Relativistic Heavy Ion Collider (RHIC) construction is progressing steadily towards completion in 1999 when beams will circulate in both collider rings. One of the major tests of the RHIC project was the commissioning of the first sextant with gold ion beams in early 1997. This is a report on preparation of the RHIC accelerator systems for the first sextant test. It includes beam position monitors, timing, injection correction through the magnetic septum and kickers, current transformers, flags and the ionization beam profile monitors, beam loss monitors, beam and quench permit link system, power supply controls, and the configuration database system. The software and hardware development and coordination of the different systems before commissioning were regularly checked during bi-weekly, and (later) weekly, progress report meetings
Planets in habitable zones: A study of the binary Gamma Cephei
The recently discovered planetary system in the binary GamCep was studied
concerning its dynamical evolution. We confirm that the orbital parameters
found by the observers are in a stable configuration. The primary aim of this
study was to find stable planetary orbits in a habitable region in this system,
which consists of a double star (a=21.36 AU) and a relatively close (a=2.15 AU)
massive (1.7 Mjup sin i) planet. We did straightforward numerical integrations
of the equations of motion in different dynamical models and determined the
stability regions for a fictitious massless planet in the interval of the
semimajor axis 0.5 AU < a < 1.85 AU around the more massive primary. To confirm
the results we used the Fast Lyapunov Indicators (FLI) in separate
computations, which are a common tool for determining the chaoticity of an
orbit. Both results are in good agreement and unveiled a small island of stable
motions close to 1 AU up to an inclination of about 15 deg (which corresponds
to the 3:1 mean motion resonance between the two planets). Additionally we
computed the orbits of earthlike planets (up to 90 earthmasses) in the small
stable island and found out, that there exists a small window of stable orbits
on the inner edge of the habitable zone in GamCep even for massive planets.Comment: 4 pages, 5 figures, changed 2 references made minor changes due to
referees advic
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RHIC tracking studies with real magnets in real places
Results from RHIC tracking studies in which measured magnetic field errors are used in all arc magnets are reported. the dependence of betatron tunes on initial amplitudes, aspect ratio, and momentum are reported and are not significantly different from measured tune dependences when randomly generated magnetic field errors are used in all magnets. Survival plots at injection and storage are also consistent with previous determinations
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