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| MOPAS066 | Fast Neutron Radioactivity and Damage Studies on Materials | radiation, radioactivity, controls, multipole | 581 | ||
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Funding: Work supported by U. S. Dept. of Energy under contracts DE-AC02-76SF00515, DE-AC02-76CH03000 and LCRD DE-FG02-03ER41280. |
Many materials and electronics need to be tested for the radiation environment expected at linear colliders (LC) to improve reliability and longevity since both accelerator and detectors will be subjected to large fluences of hadrons, leptons and gammas. Examples include NdFeB magnets, considered for the damping rings, injection and extraction lines and final focus, electronic and electro-optic devices to be utilized in detector readout, accelerator controls and the CCDs required for the vertex detector, as well as high and low temperature superconducting materials (LTSMs) because some magnets will be superconducting. Our first measurements of fast neutron, stepped doses at the UC Davis McClellan Nuclear Reactor Center (UCD MNRC) were presented for NdFeB materials at EPAC04 where the damage appeared proportional to the distances between the effective operating point and Hc. We have extended those doses, included other manufacturer's samples and measured induced radioactivities. We have also added L and HTSMs as well as a variety of relevant semiconductor and electro-optic materials including PBG fiber that we studied previously only with gamma rays. |
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| TUPMN013 | Dynamic Multipole Shimming of the APPLE Undulator UE112 | undulator, multipole, simulation, dynamic-aperture | 941 | ||
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The dynamic off axis field integrals of the BESSY UE112 are of the order of 3 Tmm. They reduce the dynamic aperture significantly which is not tolerable for top-up operation. The dynamic multipoles have successfully been shimmed for the elliptical mode using distributed Fe-shims. In the inclined mode the multipoles are minimized actively with rotatable permanent magnets which are adjusted dependent on gap and phase position. The dynamic properties of the unshimmed and the shimmed device have been simulated using an analytic model for the field description and a generating function algorithm for tracking.
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| TUPMS023 | Measurement of Permanent Magnet Material Demagnetization Due to Irradiation by High Energy Electrons | radiation, electron, undulator, synchrotron | 1230 | ||
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Funding: Work supported by the National Science Foundation under contract PHY 0202078 |
The design of insertion device depends on the properties of the permanent magnet material used. While magnetic material properties such as coercive force, residual induction and magnetization variation with temperature are provided by manufacturer, demagnetization caused by radiation can be only roughly estimated based on very few published data. To obtain data which can be reliably used in ERL insertion device design, we irradiated two materials of very different coercive forces and measured their demagnetization as function of radiation dose. For irradiation we used 5GeV electron beam from Cornell 12GeV Synchrotron. Radiation dose was measured using the calorimetric technique. One of the materials was similar to what we plan to use in construction of ERL undulators. Detailed information on experimental setup, radiation dose measurement techniques, results and analysis will be presented. |
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| TUPAS064 | Helicon Plasma Generator-assisted H- Ion Source Development at Los Alamos Neutron Science Center | plasma, ion, ion-source, electron | 1802 | ||
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Funding: Work supported by the US Department of Energy under contract DE-AC52-06NA25396 |
The aim of the helicon plasma generator-assisted negative ion source development at Los Alamos Neutron Science Center (LANSCE) is to use high-density helicon plasmas for producing intense beams of H- ions. Our work consists of two development paths, construction of a hybrid ion source and replacement of the LANSCE surface converter ion source filaments by helicon plasma generators. The hybrid ion source is a combination of a long-life plasma cathode, sustained by a helicon plasma generator, with a stationary, pulsed main discharge (multi-cusp H- production chamber) directly coupled to each other. The electrons are transferred from the helicon plasma to the cusp-chamber by thermal flow process to ignite and sustain the main discharge. Replacing the filaments of the surface converter source by two helicon plasma generators is a low-cost solution, building upon the well-proven converter-type ion sources. Both development paths are aimed at meeting the beam production goals of the LANSCE 800 MeV linear accelerator refurbishment project. The design and status of both ion source types is discussed. |
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| THPMN006 | Modification and Measurement of the Adjustable Permanent Magnet Quadrupole for the Final Focus in a Linear Collider | quadrupole, linear-collider, collider, optics | 2719 | ||
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Funding: This research was partially supported by JSPS, Grant-in-Aid for Scientific Research, 14204023-2002, 18204023-2006 and the U. S. DOE under contract DE-AC02-76SF00515. |
An adjustable permanent magnet quadrupole has been developed for the final focus in an electron-positron linear collider. The design has two concentric rings of permanent magnets. Recent activities include a newly fabricated inner ring that demonstrates the strongest field gradient at a small bore diameter of 15mm and a new magnetic field measurement system based on a rotating coil. The prospects of the R&D will be discussed. |
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| THPMS020 | Beam-Driven Dielectric Wakefield Accelerating Structure as a THz Radiation Source | radiation, electron, dipole, simulation | 3041 | ||
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Funding: United States Department of Energy |
Experimental work is planned to study the performance of a beam-driven cylindrical dielectric wakefield accelerating structure as a source of THz coherent Cerenkov radiation. For an appropriate choice of dielectric tube geometry and driving electron bunch parameters, the device operates in a single-mode regime, producing narrow-band radiation in the THz range. This source can potentially produce high power levels relative to currently available sources, with ~50 μJ radiated energy per pulse achievable using the electron beam currently in operation at the Neptune Advanced Accelerator Research Laboratory at UCLA (~13 MeV beam energy, ~200 μm RMS bunch length, ~500 pC bunch charge). Preparations underway for installation of the experiment are discussed. |
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| THPMS026 | The UCLA Helical Permanent-Magnet Inverse Free Electron Laser | undulator, laser, electron, simulation | 3055 | ||
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The Inverse Free Electron Laser (IFEL) is capable, in principle, of reaching accelerating gradients of up to 1 GV/m making it a prospective accelerator scheme for linear colliders. The Neptune IFEL at UCLA utilizes a 15 MeV Photoinjector-generated electron beam of 0.5 nC and a CO2 laser with peak energy of up to 100 J, and will be able to accelerate electrons to 100 MeV over an 80 cm long, novel helical permanent-magnet undulator. Past IFELs have been limited in their average accelerating gradient due to the Gouy phase shift caused by tight focusing of the drive laser. Here, laser guiding is implemented via an innovative Open Iris-Loaded Waveguide Structure scheme which ensures that the laser mode size and wave front are conserved through the undulator. The results of the first phase of the experiment are discussed in this paper, including the design and construction of a short micro-bunching undulator, testing of the OILS waveguide, as well as the results of corresponding simulations.
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| THPMS078 | Status of the Microwave PASER Experiment | acceleration, dipole, electron, resonance | 3166 | ||
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Funding: Work supported by US Department of Energy |
The PASER is a new method for particle acceleration, in which energy from an active medium is transferred to a charged particle beam. The effect is similar to the action of a maser or laser with the stimulated emission of radiation being produced by the virtual photons in the electromagnetic field of the beam. We are developing a demonstration PASER device operating at X-band, based on the availability of a new class of active materials that exhibit photoinduced electron spin polarization. We will report on the status of active material development and measurements, numerical simulations, and preparations for microwave PASER experiments at the Argonne Wakefield Accelerator facility. |
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| THPAS058 | Lowering the Vertical Emittance in the LER Ring of PEP-II | emittance, quadrupole, coupling, luminosity | 3621 | ||
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Funding: *Work supported by Department of Energy contract DE-AC03-76SF00515. |
The low energy ring (LER) in PEP-II has a design emittance of 0.5 nm-rad in the vertical, compared to nearly 0.1 nm-rad for the HER ring. This was thought to come from the "vertical step" of about 1 m in the interaction straight, where the LER beam after horizontal separation gets bend vertical so it sits on top of the HER in the rest of the ring. Since the program MAD does not easily reveal the location of the major emittance contribution, a program was written to calculate the coupled "curly H" parameter of mode 2 (mainly vertical) along z. Weighting it with the magnet bending revealed that the weak long bends inside the "vertical step" did less than 20% of the emittance growth. More than 80% comes from the ends of the adjacent arcs with strong bends. This is caused by the coupling cancellation of the solenoid starting already there with the skew quadrupoles SK5 and 6. By introducing additional skews in the straight instead of SK5 and 6 the emittance could be reduced by a factor of ten in simulations, but with very strong skews. Reasonable strong magnets might generate a workable compromise, since a factor of two in emittance promises 50% more luminosity in beam-beam simulations. |
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