MHI, Kobe
MHI's activities for ILC project will be shown.
ANL, Argonne
Recent developments for cryomodules required for various low- and medium beta- CW ion accelerator projects will be presented. Comparisons of the designs, fabrication technology and assembly procedures of cryomodules will be discussed. To date, development in this area has been mostly for basic science applications, however, there is also considerable interest in ion accelerators for other applications such as national defense, medicine and accelerator driven systems. The outlook for and some development requirements of SRF cryomodules for these applications will be discussed.
Fermilab, Batavia
Fermilab is currently focusing its efforts toward the development of Stainless Steel (SS) helium vessels for its 1.3 GHz SRF cavities. The objective is to transition towards the concept of using SS helium vessels to dress the bare SRF cavities, thereby paving way for significant cost reduction and efficient production techniques for future accelerators. The biggest challenge has been to design a reliable interface between the niobium cavity end group and the stainless steel end flange that encloses the helium vessel. Fermilab has been pursuing a brazed joint design to allow this transition. Additional design challenges associated with this transition are ensuring proper cooling of the cavity, compensating for the difference in thermal contraction between the SS helium vessel and niobium cavities, and also modification of the tuning procedure and ensuring the safety and reliability of the blade and piezo tuners. Current efforts on the qualification of the niobium-SS braze joint, finite element simulations of the thermal design aspects, bench testing of actual cavity displacements, and study of the effects on the tuners will be presented.
CLASSE, Ithaca, New York
This talk will give an overview of recent results on the highest gradient SRF cavities, including new, improved surface treatments and cavity repair. Significant recent progress has been made in understanding gradient limiting effects, and how to cure them. Many of these results will be reviewed here.
JLAB, Newport News, Virginia
Recent incorporation of analytic electrochemistry into the development of protocols for electropolishing niobium SRF cavities has yielded new insights for optimizing this process for consistent, high-performance results. Use of reference electrodes in the electrolyte, electrochemical impedance spectroscopy (EIS), rotating disk electrodes (RDE), and controlled sample temperatures has greatly clarified the process dynamics over the empirical understanding developed via years of practice. Minimizing rf losses at high operational gradients is very valuable for CW linacs. Jefferson Lab is applying these new insights to the low-loss 7-cell cavity design developed for the CEBAF 12 GeV Upgrade. Together with controlled cleaning and assembly techniques to guard against field-emission causing particulates, the resulting process is yielding consistent cavity performance that exceeds project requirements. Cavity tests show BCS-limited Q well above 30 MV/m. Detailed process data, interpretation, and resulting rf performance data will be presented.
DESY, Hamburg
For the XFEL cavity production a rather large quantity of niobium sheets from partially new niobium vendors has to be delivered according to the XFEL Cavity Specification. It is of high importance that the material monitoring of this niobium has to be done within the production process to ensure a high performance of the cavities. The quality assurance program includes electrical measurements, mechanical, structural and chemical material analysis. For the surface investigations two eddy current scanning devices have been fabricated on the basis of our specification and experience. The scanning process and evaluation of test result can now be done in a few minutes per sheet. We describe the material test methods and the scanning machine. Measured results of the pre-series niobium will be compared to older material tests results.
DESY, Hamburg
Superconducting cavities have long been used in particle accelerators. The 1.3 GHz cavities developed in the TESLA collaboration will be the basis of the European XFEL and are the cavity of choice for the International Linear Collider (ILC). The fabrication of the cavities has been optimised over the past 20 years and will now be applied in industrial production of the 800 cavities foreseen for the XFEL. The DESY ILC group is developing tools to monitor those aspects of the production that affect the gradient of these cavities. The main obstacle in achieving a high gradient >30 MV/m is the quench induced in surface structures in the niobium. Such features are explored in an optical inspection of the 9-cell cavity structures and supplemented by measurements of the second sound that originates from the phase transition of the liquid helium at the position of the quench. Oscillating Superleak Transducers (OST) are used to record the signal of the second sound. The second sound measurements are thought to replace the time consuming direct temperature measurements on the outer cavity surface with a resistor system. The status of the various tools will be described.
ANL, Argonne
IIT, Chicago, Illinois
JLAB, Newport News, Virginia
NHMFL, Tallahassee, Florida
An effort, centered at Argonne, has started to explore the use of Atomic Layer Deposition (ALD) to study and improve the performance of superconducting rf (SRF) accelerating structures. This effort has a number of parts: a survey the properties of ALD deposited films, a study of loss mechanisms of SRF structures, and a program of coating single cell cavities, to begin to optimize the performance of complete systems. Early results have included improving the performance of individual structures and, identification of magnetic oxides as a loss mechanism in SRF. We describe the program and summarize recent progress.
CERN, Geneva
KHLim, Diepenbeek
CERN is assembling a new vertical electropolishing facility in order to process several niobium cavities of beta 1 and beta 0.65 in the context of the HP-SPL R&D programme. Electrochemical simulations are being used in order to define the optimal cathode geometry to process the cavities in a vertical position. Macroscopic properties of fluid dynamics like the Reynolds number and thermodynamics linked to the power dissipated in the process are taken into account to dimension the main system components. All the materials from the different equipments must be compatible with all chemicals within the required working temperature and pressure. To provide safe operating conditions when handling chemicals or processing cavities, specific safety and protection equipment is also foreseen.
CERN, Geneva
TRIUMF, Vancouver
For the foreseen intensity and energy upgrade of the ISOLDE complex at CERN (HIE-ISOLDE project) a new superconducting LINAC based on sputtered Nb/Cu Quarter Wave Resonators (QWRs) of two different beta families will be installed in the next three to five years. A prototype cavity of the higher beta family is currently being developed. In this paper we will discuss the latest developments on the sputtering technique for this kind of cavity geometry. First cold RF measurements will be reported.
KAERI, Daejon
A superconducting RF cavity with a geometrical beta of 0.42 and a resonant frequency of 700 MHz has been under consideration for an extension program of Proton Engineering Frontier Project (PEFP) to accelerate the proton beam above 100 MeV. A five-cell prototype was fabricated and tested to confirm the fabrication procedure and to check the RF and mechanical properties. High RRR niobium sheets (RRR > 250) were used for the cavity material, whereas reactor grade niobium and NbTi were used for the beam pipe region and the flange, respectively. Double-ring stiffening structure was adopted to reduce the Lorentz force detuning effect. For the vertical test of the prototype cavity, a cryostat with operating temperature of 4.2 K was designed and fabricated. The cryostat was thermally insulated with 40 layers of MLI and the vacuum jacket and equipped with temperature monitors and liquid level sensors. The RF system for driving the cavity is based on PLL to track the resonance condition. The status of the prototype development and the vertical test results will be presented in this paper.
Kyoto ICR, Uji, Kyoto
KEK, Ibaraki
Optical inspections on superconducting cavities seem to become familiar to those who are involved in the cavity fabrications. Further improvements on the Kyoto Camera have been carried out these years together with further investigation technique developments, such as high density T-map or eddy current scan. Improvements on Kyoto Camera includes change of EL sheets to LEDs, which raised the brightness 10 times and the lifetime very long as known well. The resolution was also increased. The high density T-map will help to locate a hot spot during the vertical tests and the eddy current scan will be useful for screening of bare Nb sheets with possible defects. These progresses will be reported.
Texas A&M University, College Station, Texas
JLAB, Newport News, Virginia
A 1.3 GHz superconducting test cavity is being developed to test wafer samples of advanced SRF materials with surface fields at or beyond the Nb BCS limit. The mushroom-shaped Nb cavity is dielectric-loaded, with a hemisphere of high-purity sapphire located just above a detachable end flange. Wafer samples are mounted on the end flange. The cavity is operated in the TE011 mode, so no currents flow from the end flange to the side walls. Fields are concentrated on the wafer sample so that the peak surface field there is 4 times greater than anywhere else on the cavity walls. The loss tangent of ultrapure sapphire is critical to the performance of the test cavity. A separate first experiment has been conducted in a special 1.8 GHz cavity to measure this loss tangent in L band as a function of temperature for the first time. Results of the measurement and the final design of the ultimate-gradient test cavity will be presented.
SLAC, Menlo Park, California
NSCL, East Lansing, Michigan
In the driver linac of the Facility for Rare Isotope Beams (FRIB), multipacting is an issue of concern for the superconducting resonators, which must accelerate the ion beams from 0.3 MeV per nucleon to 200 MeV per nucleon. While most of the multipacting bands can be conditioned and eliminated with RF, hard multipacting barriers may prevent the resonators from reaching the design voltage. Using the ACE3P code suite, multipacting bands can be computed and analysed with the Track3P module to identify potential problems in the resonator design. This paper will present simulation results for multipacting in half-wave and quarter-wave resonators for the FRIB driver linac and compare the simulations with RF measurements on the resonators.
HZB, Berlin
JLAB, Newport News, Virginia
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
BNL, Upton, Long Island, New York
DESY, Hamburg
MBI, Berlin
ERLs have the powerful potential to provide very high current beams with exceptional and tailored parameters for many applications, from next-generation light sources to electron coolers. However, the demands placed on the electron source are severe. It must operate CW, generating a current of 100 mA or more with a normalized emittance of order 1 μm rad. Beyond these requirements, issues such as dark current and long-term reliability are critical to the success of ERL facilities. As part of the BERLinPro project, Helmholtz Zentrum Berlin (HZB) is developing a CW SRF photoinjector in three stages, the first of which is currently being installed at HZB's HoBiCaT facility. It consists of an SRF-cavity with a Pb cathode and a superconducting solenoid. Subsequent development stages include the integration of a high-quantum-efficiency cathode and RF components for high-current operation. This paper discusses the HZB roadmap towards an ERL-suitable SRF photoinjector, the present status of the facility and first cavity tests.
IHEP Beijing, Beijing
KEK, Ibaraki
IHEP Beiing, Beijing
The combination of the low-loss shape and large grain niobium material is expected to be the possible way to achieve higher gradient and lower cost for ILC 9-cell cavities. As the key component of the 'IHEP 1.3 GHz SRF Accelerating Unit and Horizontal Test Stand Project', a low-loss shape 9-cell cavity using Ningxia large grain niobium (IHEP-01) was fabricated and surface treated (CBP, CP, annealing, pre-tuning) at IHEP. Then the cavity was shipped to KEK STF for ultrasonic cleaning, high pressure rinsing, baking and vertical test. The cavity reached 20 MV/m in the first vertical test on July 1st 2010. The quench location has been found by T-mapping and optical inspection. The strong field emission and equator defects will be removed by further treatment. The fabrication procedure, surface treatment recipes and the first test results are summarized in this paper.