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| MOPCH141 | Fast Argon-Baking Process for Mass Production of Niobium Superconducting RF Cavities | ion, vacuum, lattice, superconducting-RF | 381 | ||
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Baking is a necessary stage to reach high gradients with niobium superconducting cavities. In the standard process, so called "in-situ UHV baking", Nb cavity is baked at 110°C, during 2 days. During this treatment the inner part of the cavity is pumped out under Ultra High Vacuum conditions. In order to save time, "fast UHV baking" at 145 °C during 3 hours, under UHV pumping, has been successfully demonstrated* with similar improvements for cavity performances compare to the standard treatment. With the same simplification concern, we report here about an alternative method to avoid restrictive UHV requirements. Experiments have been carried out to perform "fast baking" in oxygen-free atmosphere, because bad performances have been observed with "fast baking" in air. These degradations are closely connected with a strong oxygen penetration in bulk analysed by Secondary Ion Mass Spectroscopyon on Nb samples .
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*Proceedings of SRF Workshop – Ithaca (July 2005) – TuP05. |
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| MOPCH154 | Dry-ice Cleaning on SRF Cavities | DESY, controls, linac, vacuum | 418 | ||
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High pressure rinsing with ultra-pure water is the well-proven standard cleaning step after chemical or electrochemical surface treatment of SRF cavities. Dry-ice cleaning (DIC) is a powerful additional cleaning option which depends on the sublimation-impulse method. Particles and film contaminations, especially hydro-carbons, are removed without residues. Furthermore DIC offers the possibility of a final horizontal cleaning of a fully equipped cavity because water is not present in the cleaning process. Horizontal cleaning tests on single-cell cavities showed promising high gradient, high Q-value performances, but field emission is still the limiting effect. On the basis of these tests a new IR-heater module is installed to keep a high temperature gradient between the CO2 jet and the cavity surface. New test results for this optimized cleaning set-up will be presented.
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| MOPCH176 | A Comparison of Large Grain and Fine Grain Cavities Using Thermometry | site, cryogenics, superconducting-RF | 475 | ||
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An important limitation for SRF niobium cavities is the ”high field Q-slope.” To investigate this phenomenon we compare the behavior of large grain and fine grain cavities using thermometry. Thermometry allows us to distinguish between different problems which occur in cavities, and to distinguish between different areas showing high field Q-slope. We looked for the difference in heating between grain boundaries and inside grains. We have found interesting differences between the heating of high field slope regions and the heating of point-like defects.
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| MOPLS084 | Experimental Comparison at KEK of High Gradient Performance of Different Single Cell Superconducting Cavity Designs | KEK, DESY, TESLA, controls | 750 | ||
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We have performed a series of vertical tests of three different designs of single cell Niobium superconducting cavities at 2 degrees Kelvin. These tests aimed at establishing that an accelerating gradient of 45 MV/m could be reached in any of the designs, while using the standard KEK surface preparation. The designs tested were the Cornell re-entrant shape (RE), the DESY/KEK low loss shape (LL), and the KEK ICHIRO series. The cavities underwent surface preparation consisting of centrifugal barrel polishing, light chemical polishing, electropolishing, and finally a high pressure water rinse. All three kinds of cavities were used in a series of vertical tests to investigate details of the surface treatment. When using ultra-pure water for the high pressure rinse, the LL cavity reproducibly exceeded a gradient of 45 MV/m, the RE design reproducibly reached a gradient of between 50 MV/m and 52 MV/m, and three of the six ICHIRO cavities reached a gradient of between 45 MV/m and 49 MV/m.
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| MOPLS087 | Series Test of High-gradient Single-cell Superconducting Cavity for the Establishment of KEK Recipe | KEK, vacuum, electron, pick-up | 756 | ||
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We have performed a series of vertical tests of single cell Niobium superconducting cavities at 2 degrees Kelvin. These tests aimed at establishing the feasibility of reaching an accelerating gradient of 45 MV/m on a routine basis. The cavity profiles were all of the KEK low loss design and were fabricated from deep drawn Niobium half shells using electron beam welding. The cavity surface preparation followed an established KEK procedure of centrifugal barrel polishing, light chemical polishing, high temperature annealing, electropolishing, and finally a high pressure water rinse. Of the six cavities tested, three exceeded 45 MV/m on the first test. This clearly establishes the feasibility of this gradient. In this paper we describe these tests and our future program for optimising the surface preparation.
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| TUPCH149 | Design of a 10 MHz Heavy Ion RFQ for a RIA Post Accelerator | rfq, ion, heavy-ion, target | 1370 | ||
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Design of a 10 MHz heavy ion RFQ for the RIA post accelerator is described. Main rf and mechanical parameters of the proposed accelerator are given. This 10 MHz RFQ is capable of accelerating beams from an initial energy of 2 keV/u to 8 keV/u covering a charge to mass ratio from 1/10 to 1/240.
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| WEPLS089 | Feasibility Study of a Permanent Magnet Made from High-Tc Bulk Superconductor | dipole, LEFT, permanent-magnet, shielding | 2580 | ||
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A field trapping experiment using a magnetic field up to ~1.5 T was performed using high-Tc bulk superconductors. Applications of bulk high-Tc superconductors have been investigated in various fields. High-Tc superconductors are attractive since they can trap higher magnetic fields than conventional permanent magnets. The trapping experiment was done with a field of above 1 T, which can be easily produced by conventional magnets. However, achieving the desired field distribution and understanding the characteristics of the trapped field and its decay process would open up the possibility of high-Tc bulk superconductor applications in the design of magnets for particle accelerators The distribution of the trapped field and its decay process was monitored by an array of Hall sensors for different shapes of the bulk superconductors. The observations are reported on in this paper.
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| WEPLS114 | Progress on the MICE Tracker Solenoid | vacuum, radiation, emittance, power-supply | 2646 | ||
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This report describes the 400 mm warm bore tracker solenoid for the Muon Ionization Cooling Experiment (MICE). The 2.923 m long tracker solenoid module includes the radiation shutter between the end absorber focus coil modules and the tracker as well as the 2.780 meter long magnet cryostat vacuum vessel. The 2.554 m long tracker solenoid consists of two sections, a three-coil spectrometer magnet and a two-coil matching section that matches the uniform field 4 T spectrometer solenoid into the MICE cooling channel. The two tracker magnets are used to provide a uniform magnetic field for the fiber detectors that are used to measure the muon beam emittance at the two ends of the cooling channel. This paper describes the design for the tracker magnet coils and the 4.2 K cryogenic coolers that are used to cool the superconducting magnet. Interfaces between the magnet and the detectors are discussed.
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