A charged particle accelerator is a complex machine that takes elementary charged particles and accelerates them to very high energies. Accelerator physics is a field of physics encompassing all the aspects required to design and operate the equipment and to understand the resulting dynamics of the charged particles. There are software packages associated with each domain. The 1990 edition of the Los Alamos Accelerator Code Group's compendium [1] provides summaries of more than 200 codes. Certain codes are still in use today, although many are obsolete. Another index of existing and historical accelerator simulation codes is located at the CERN CARE/HHH website. [2]
For many applications it is sufficient to track a single particle through the relevant electric and magnetic fields. Old codes no longer maintained by their original authors or home institutions include: BETA, [3] AGS, ALIGN, COMFORT, DESIGN, DIMAD, HARMON, LEGO, LIAR, MAGIC, MARYLIE, PATRICIA, PETROS, RACETRACK, SYNCH, [4] TRANSPORT, TURTLE, and UAL. Some legacy codes are maintained by commercial organizations for academic, industrial and medical accelerator facilities that continue to use those codes. TRACE 3-D and TURTLE are among the historic codes that are commercially maintained. [5]
Major maintained codes include:
Single Particle Dynamics | Spin Tracking | Taylor Maps | Weak-Strong Beam-Beam Interaction | Electromagnetic Field Tracking | Higher Energy Collective Effects | Synchrotron Radiation Effects | Radiation Tracking | Wakefields | Extensible | Notes | |
---|---|---|---|---|---|---|---|---|---|---|---|
Accelerator Toolbox (AT), [6] | Yes | Yes [7] | No | No | No | Yes | No | No | No | Yes | |
ASTRA [8] | Yes | No | No | No | Yes | Yes | No | No | Yes | No | For space-charge simulations |
BDSIM [9] | Yes | No | No | No | Yes | No | No | No | No | Yes | For particle-matter simulations. |
Bmad (contains PTC) [10] | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Reproduces PTC's unique beam line structures. Simulates X-rays. |
COSY INFINITY [11] | Yes | Yes | Yes | No | Yes | No | No | No | No | Yes | Arbitrary-order differential-algebraic transfer maps |
DYNAC [12] | Yes | No | No | No | No | No | No | No | No | No | |
Elegant [13] | Yes | No | No | No | Yes | Yes | Yes | No | Yes | No | |
MAD8 and MAD-X (includes PTC) [14] | Yes | No | Yes | Yes | No | No | Yes | No | No | No | |
MAD-NG [14] | Yes | No | Yes | Yes | No | No | Yes | No | No | Yes | Extensible, embeds LuaJIT |
MERLIN++ [15] [16] | Yes | Yes | No | No | No | No | No | No | Yes | Yes | Other: beam-matter interactions, sliced-macroparticle tracking |
OCELOT [17] | Yes | No | No | No | No | Yes | Yes | Yes | Yes | Yes | |
OPA [18] | Yes | No | No | No | No | No | No | No | No | No | |
OPAL [19] | Yes | No | Yes | No | Yes | Yes | No | No | Yes | Yes | runs on laptops and on x 10k cores. |
PLACET [20] | Yes | No | No | No | No | Yes | Yes | No | Yes | Yes | LINAC including wakefields simulations. |
Propaga [21] | Yes | No | No | No | No | No | No | No | No | Yes | |
PTC [22] | Yes | Yes | Yes | Yes | Yes | No | No | No | No | Yes | |
SAD [23] | Yes | No | No | Yes | No | Yes | Yes | No | Yes | No | |
SAMM [24] | Yes | Yes | No | No | No | No | No | No | No | No | |
SixTrack [25] | Yes | No | Yes | Yes | No | No | No | No | No | No | Can run on BOINC |
Zgoubi [26] [27] | Yes | Yes | No | No | Yes | No | Yes | No | No | Yes |
Can simulate the effect of synchrotron radiation emission on the particles being tracked.
This is not the same as simulating the effect of synchrotron radiation emission on the particles being tracked.
The self interaction (e.g. space charge) of the charged particle beam can cause growth of the beam, such as with bunch lengthening, or intrabeam scattering. Additionally, space charge effects may cause instabilities and associated beam loss. Typically, at relatively low energies (roughly for energies where the relativistic gamma factor is less than 10 or so), the Poisson equation is solved at intervals during the tracking using particle-in-cell algorithms. Space charge effects lessen at higher energies so at higher energies the space charge effects may be modeled using simpler algorithms that are computationally much faster than the algorithms used at lower energies. Codes that handle low energy space charge effects include:
At higher energies, space charge effects include Touschek scattering and coherent synchrotron radiation (CSR). Codes that handle higher energy space charge include:
When two beams collide, the electromagnetic field of one beam will then have strong effects on the other one, called beam-beam effects. So called "weak-strong" simulations model one beam (called the "strong" beam since it affects the other beam) as a fixed distribution (typically a Gaussian distribution) which interacts with the particles of the other "weak" beam. This greatly simplifies the simulation. A full "strong-strong" simulation is more complicated and takes more simulation time. Strong-strong codes include
An important class of collective effects may be summarized in terms of the beams response to an "impedance". An important job is thus the computation of this impedance for the machine. Codes for this computation include
To control the charged particle beam, appropriate electric and magnetic fields must be created. There are software packages to help in the design and understanding of the magnets, RF cavities, and other elements that create these fields. Codes include
Given the variety of modeling tasks, there is not one common data format that has developed. For describing the layout of an accelerator and the corresponding elements, one uses a so-called "lattice file". There have been numerous attempts at unifying the lattice file formats used in different codes. One unification attempt is the Accelerator Markup Language, and the Universal Accelerator Parser. [52] Another attempt at a unified approach to accelerator codes is the UAL or Universal Accelerator Library. [53] As of 2023 neither of these formats are maintained.
The file formats used in MAD may be the most common, with translation routines available to convert to an input form needed for a different code. Associated with the Elegant code is a data format called SDDS, with an associated suite of tools. If one uses a Matlab-based code, such as Accelerator Toolbox, one has available all the tools within Matlab.
For the interchange of particle positions and electromagnetic fields, the OpenPMD [54] standard defines a format which can then be implemented with a file format like HDF5.
There are many applications of particle accelerators. For example, two important applications are elementary particle physics and synchrotron radiation production. When performing a modeling task for any accelerator operation, the results of charged particle beam dynamics simulations must feed into the associated application. Thus, for a full simulation, one must include the codes in associated applications. For particle physics, the simulation may be continued in a detector with a code such as Geant4.
For a synchrotron radiation facility, for example, the electron beam produces an x-ray beam that then travels down a beamline before reaching the experiment. Thus, the electron beam modeling software must interface with the x-ray optics modelling software such as SRW, [55] Shadow, [56] McXTrace, [57] or Spectra. [58] Bmad [10] can model both X-rays and charged particle beams. The x-rays are used in an experiment which may be modeled and analyzed with various software, such as the DAWN science platform. [59] OCELOT [60] also includes both synchrotron radiation calculation and x-ray propagation models.
Industrial and medical accelerators represent another area of important applications. A 2013 survey estimated that there were about 27,000 industrial accelerators and another 14,000 medical accelerators world wide, [61] and those numbers have continued to increase since that time. [62] Codes used at those facilities vary considerably and often include a mix of traditional codes and custom codes developed for specific applications. The Advanced Orbit Code (AOC) [63] developed at Ion Beam Applications is an example.
Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combination of protons and neutrons is called nuclear physics.
A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. A cyclotron accelerates charged particles outwards from the center of a flat cylindrical vacuum chamber along a spiral path. The particles are held to a spiral trajectory by a static magnetic field and accelerated by a rapidly varying electric field. Lawrence was awarded the 1939 Nobel Prize in Physics for this invention.
A linear particle accelerator is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beamline. The principles for such machines were proposed by Gustav Ising in 1924, while the first machine that worked was constructed by Rolf Widerøe in 1928 at the RWTH Aachen University. Linacs have many applications: they generate X-rays and high energy electrons for medicinal purposes in radiation therapy, serve as particle injectors for higher-energy accelerators, and are used directly to achieve the highest kinetic energy for light particles for particle physics.
Accelerator physics is a branch of applied physics, concerned with designing, building and operating particle accelerators. As such, it can be described as the study of motion, manipulation and observation of relativistic charged particle beams and their interaction with accelerator structures by electromagnetic fields.
ATLAS is the largest general-purpose particle detector experiment at the Large Hadron Collider (LHC), a particle accelerator at CERN in Switzerland. The experiment is designed to take advantage of the unprecedented energy available at the LHC and observe phenomena that involve highly massive particles which were not observable using earlier lower-energy accelerators. ATLAS was one of the two LHC experiments involved in the discovery of the Higgs boson in July 2012. It was also designed to search for evidence of theories of particle physics beyond the Standard Model.
A dipole magnet is the simplest type of magnet. It has two poles, one north and one south. Its magnetic field lines form simple closed loops which emerge from the north pole, re-enter at the south pole, then pass through the body of the magnet. The simplest example of a dipole magnet is a bar magnet.
The Large Electron–Positron Collider (LEP) was one of the largest particle accelerators ever constructed. It was built at CERN, a multi-national centre for research in nuclear and particle physics near Geneva, Switzerland.
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Gargamelle was a heavy liquid bubble chamber detector in operation at CERN between 1970 and 1979. It was designed to detect neutrinos and antineutrinos, which were produced with a beam from the Proton Synchrotron (PS) between 1970 and 1976, before the detector was moved to the Super Proton Synchrotron (SPS). In 1979 an irreparable crack was discovered in the bubble chamber, and the detector was decommissioned. It is currently part of the "Microcosm" exhibition at CERN, open to the public.
Microcosm or CERN Museum was an interactive exhibition presenting the work of the CERN particle physics laboratory and its flagship accelerator the Large Hadron Collider (LHC). It first opened to the public in 1990 and closed permanently in September 2022, to be replaced by the Science Gateway in 2023. The final version of the exhibition opened in January 2016, developed by CERN in collaboration with Spanish design team Indissoluble.
A particle beam is a stream of charged or neutral particles. In particle accelerators, these particles can move with a velocity close to the speed of light. There is a difference between the creation and control of charged particle beams and neutral particle beams, as only the first type can be manipulated to a sufficient extent by devices based on electromagnetism. The manipulation and diagnostics of charged particle beams at high kinetic energies using particle accelerators are main topics of accelerator physics.
The AWAKE facility at CERN is a proof-of-principle experiment, which investigates wakefield plasma acceleration using a proton bunch as a driver, a world-wide first. It aims to accelerate a low-energy witness bunch of electrons from 15 to 20 MeV to several GeV over a short distance by creating a high acceleration gradient of several GV/m. Particle accelerators currently in use, like CERN's LHC, use standard or superconductive RF-cavities for acceleration, but they are limited to an acceleration gradient in the order of 100 MV/m.
The Bevatron was a particle accelerator — specifically, a weak-focusing proton synchrotron — at Lawrence Berkeley National Laboratory, U.S., which began operating in 1954. The antiproton was discovered there in 1955, resulting in the 1959 Nobel Prize in physics for Emilio Segrè and Owen Chamberlain. It accelerated protons into a fixed target, and was named for its ability to impart energies of billions of eV.
Electron scattering occurs when electrons are displaced from their original trajectory. This is due to the electrostatic forces within matter interaction or, if an external magnetic field is present, the electron may be deflected by the Lorentz force. This scattering typically happens with solids such as metals, semiconductors and insulators; and is a limiting factor in integrated circuits and transistors.
The EGS computer code system is a general purpose package for the Monte Carlo simulation of the coupled transport of electrons and photons in an arbitrary geometry for particles with energies from a few keV up to several hundreds of GeV. It originated at SLAC but National Research Council of Canada and KEK have been involved in its development since the early 80s.
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies to contain them in well-defined beams. Small accelerators are used for fundamental research in particle physics. Accelerators are also used as synchrotron light sources for the study of condensed matter physics. Smaller particle accelerators are used in a wide variety of applications, including particle therapy for oncological purposes, radioisotope production for medical diagnostics, ion implanters for the manufacture of semiconductors, and accelerator mass spectrometers for measurements of rare isotopes such as radiocarbon.
A storage ring is a type of circular particle accelerator in which a continuous or pulsed particle beam may be kept circulating, typically for many hours. Storage of a particular particle depends upon the mass, momentum, and usually the charge of the particle to be stored. Storage rings most commonly store electrons, positrons, or protons.
The Research Institute for Nuclear Problems of Belarusian State University is a research institute in Minsk, Belarus. Its main fields of research are nuclear physics, particle physics, materials science and nanotechnology.
The NA63 experiment aims to study the radiation process in strong electromagnetic fields. Located at CERN, in the North Area. It is a fixed-target experiment which uses the H4 secondary electron beams from the SPS, which are directed onto different targets. Those are made from a variety of elements, ranging from the relatively light carbon and silicon, through the heavier iron and tin to tungsten, gold and lead and are either amorphous or mono-crystals.
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