Cloud computing in nanoHUB powering education and research

In this hands-on workshop, participants are encouraged to bring a laptop computer with Internet access to explore nanoHUB and practise using the open access simulation tools and other special features that are part of this cyberinfrastructure. Creating a free nanoHUB account (www.nanohub.org/register) in advance and installing the latest version of Java (http://www.java.com/en/download/installed.jsp) will expedite the process of running simulation tools. Methods for personalizing your nanoHUB experience and working with groups and projects in nanoHUB will be provided, as well as tips and tricks for using nanoHUB in the classroom. Experts in several areas of computational simulation will be available to give individual guidance on running research-grade simulations

Quasistatic Drift Tube Accelerating Structures For Low Speed heavy Ions

The major attractions of the pulsed drift-tubes are that they are non-resonant structures and that they appear suitable for accelerating a very high current bunch at low energies. The mechanical tolerances of the non-resonant structure are very loose and the cost per meter should be low; the cost of the transport system is expected to be the major cost. The pulse power modulators used to drive the drift-tubes are inexpensive compared to r.f. sources with equivalent peak-power. The longitudinal emittance of the beam emerging from the structure could be extremely low

Induction Linac Pulsers

The pulsers used in most of the induction linacs evolved from the very large body of work that was done in the U.S. and Great Britain during the development of the pulsed magnetron for radar. The radar modulators started at {approx}100 kW and reached >10 MW by 1945. A typical pulse length was 1 {mu}s at a repetition rate of 1,000 pps. A very comprehensive account of the modulator development is Pulse Generators by Lebacqz and Glasoe, one of the Radiation Laboratory Series. There are many permutations of possible modulators, two of the choices being tube type and line type. In earlier notes I wrote that technically the vacuum tube pulser met all of our induction linac needs, in the sense that a number of tubes, in series and parallel if required, could produce our pulses, regulate their voltage, be useable in feed-forward correctors, and provide a low source impedance. At a lower speed, an FET array is similar, and we have obtained and tested a large array capable of >10 MW switching. A modulator with an electronically controlled output only needs a capacitor for energy storage and in a switched mode can transfer the energy from the capacitor to the load at high efficiency. Driving a full size Astron induction core and a simulated resistive 'beam load' we achieved >50% efficiency. These electronically controlled output pulses can produce the pulses we desire but are not used because of their high cost. The second choice, the line type pulser, visually comprises a closing switch and a distributed or a lumped element transmission line. The typical switch cannot open or stop conducting after the desired pulse has been produced, and consequently all of the initially stored energy is dissipated. This approximately halves the efficiency, and the original cost estimating program LIACEP used this factor of two, even though our circuits are usually worse, and even though our inveterate optimists often omit it. The 'missing' energy is that which is reflected back into the line from mismatches, the energy left in the accelerator module's capacitance, the energy lost in the switch during switching and during the pulse, and the energy lost in the pulse line charging circuit. For example, a simple resistor-limited power supply dissipates as much energy as it delivers to the pulse forming line, giving a factor if two by itself, therefore efficiency requires a more complicated charging system

Time Delays, Bends, Acceleration and Array Reconfigurations

This note was originally one of the parts of the work on a 50 MeV and 500 MeV Rb{sup +} driver and part of work on delay lines for a 60 GeV U{sup +12} driver. It is slightly expanded here to make it more generally applicable. The emphasis is on beam manipulations such as joining and separating beams at the two ends of a driver and providing various time delays between beams as required by the target

Simplified Generation of the Input Models of Object Oriented Micromagnetic Framework (OOMMF)

Object Oriented MicroMagnetic Framework (OOMMF) is a micromagnetic simulation tool. It takes a memory initialization file (MIF) as the input and outputs various forms of data such as data table, graph and magnetic configuration plots. It is accurate and fast compared to other existing tools such as MATLAB. Few experimentalists used it in the past, however, due to two main reasons. First, OOMMF requires a specific version of programming environment on the local computer which is difficult to be installed. Second, MIF file is very complicated to code and it also requires users to read a lengthy guidelines. Our solution to these problems is to first install OOMMF on nanoHUB, and second design a MIF generator, which is a separate tool can help users to design their models without understanding how to code a MIF file. By using the MIF generator, a user can enter the parameters of their micromagnetic models, such as dimensions and magnetic fields, and generates a corresponding MIF file which can be loaded into OOMMF as an input for further simulation. As a result, both the MIF generator and OOMMF are published onto nanoHUB so users can run all simulations on a web-based browser. Two different experiments were simulated to prove the success of this project. A cubic micromagnet was simulated in both local and nanoHUB OOMMF and the simulation results are nearly identical. Also, two cylindrical nanowires were modeled through the MIF generator and simulated in OOMMF. The simulation results correspond to the experimental results obtained before. Overall, OOMMF is improved by designing a separate tool which helps users to generator input files for OOMMF

Impact of the Wiggler Coherent Synchrotron Radiation Impedance on the Beam Instability

Coherent Synchrotron Radiation (CSR) can play an important role by not only increasing the energy spread and emittance of a beam, but also leading to a potential instability. Previous studies of the CSR induced longitudinal instability were carried out for the CSR impedance due to dipole magnets. However, many storage rings include long wigglers where a large fraction of the synchrotron radiation is emitted. This includes high-luminosity factories such as DAPHNE, PEP-II, KEK-B, and CESR-C as well as the damping rings of future linear colliders. In this paper, the instability due to the CSR impedance from a wiggler is studied assuming a large wiggler parameter $K$. The primary consideration is a low frequency microwave-like instability, which arises near the pipe cut-off frequency. Detailed results are presented on the growth rate and threshold for the damping rings of several linear collider designs. Finally, the optimization of the relative fraction of damping due to the wiggler systems is discussed for the damping rings.Comment: 10 pages, 7 figure