Muons, Inc, Batavia
Fermilab, Batavia
A Superconducting RF (SRF) Linac can be used for an accelerator-driven subcritical (ADS) nuclear power station to produce more than 5 GW electrical power in an inherently safe region below criticality, generating no greenhouse gases, producing minimal nuclear waste and no byproducts that are useful to rogue nations or terrorists, incinerating waste from conventional nuclear reactors, and efficiently using abundant thorium fuel that does not need enrichment. First, the feasibility of the accelerator technology must be demonstrated. We describe the Linac parameters that can enable this vision of an almost inexhaustible source of power and we discuss how the corresponding reactor technology can be matched to these parameters.
CEA, Gif-sur-Yvette
CIEMAT, Madrid
INFN/LNL, Legnaro (PD)
IFMIF/EVEDA, Rokkasho
Fusion for Energy, Garching
JAEA, Aomori
The objectives of the IFMIF/EVEDA project are to produce the detailed design of the entire IFMIF facility, as well as to build and test a number of prototypes, including a high-intensity CW deuteron accelerator (125 mA @ 9 MeV). Most of the accelerator components (Injector, RFQ, Superconducting RF-Linac, Transport Line and Beam Dump, RF Systems, Local control systems, beam instrumentation) are designed and provided by European institutions (CEA/Saclay, CIEMAT, INFN/LNL, SCK-CEN), while the RFQ couplers, the supervision of the control system and the building including utilities constructed at Rokkasho BA site are provided by JAEA. The coordination between Europe and Japan is ensured by an international project team, located in Rokkasho, where the accelerator will be installed and commissioned. The design and R&D activities are presented, as well as the schedule of the prototype accelerator.
CEA, Gif-sur-Yvette
CIEMAT, Madrid
FZJ, Jülich
In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV, an accelerator prototype is presently under design for the first phase of the project. A superconducting option has been chosen for the 5 MeV RF Linac, based on a cryomodule composed of 8 low-beta Half-Wave Resonators (HWR), 8 Solenoid Packages and 8 RF couplers. This paper will focus on the HWR sub-system: the RF, thermo-mechanical design, and the realization of the first prototype of HWR will be presented. The resonator tuning frequency is controlled by an innovant Cold Tuning System (CTS), located in the central region of the cavity. The different options for tuning will be discussed and the final thermo-mechanical design will be detailed. First validation test results of the CTS are expected for the conference.
IFMIF/EVEDA, Rokkasho
CEA, Gif-sur-Yvette
INFN/LNL, Legnaro (PD)
Fusion for Energy, Garching
CIEMAT, Madrid
JAEA, Rokkasho, Kamikita, Aomori
In the frame of the IFMIF/EVEDA project, a high-intensity (125 mA) CW deuteron accelerator will be installed and commissioned at the Rokkasho's Broader Approach (BA) site. The main objective of this 9 MeV prototype is to provide information on the feasibility of the design, the manufacturing and the operation of the two linacs (up to 40 MeV) foreseen for IFMIF*. Based on the requirements for each System (Accelerators, Lithium target and Tests Facility) which are deduced from the IFMIF fusion material irradiation requirements, given by the users, the objectives of this accelerator prototype are defined and presented here. Also, because of the distributed nature of the design work and the procurement of the accelerator, organization of the installation and commissioning phase is essential. The installation and commissioning schemes, the organization proposed and the overall plans are presented.
*IFMIF International Team, IFMIF Comprehensive Design Report (CDR) 2003.
FZD, Dresden
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
MBI, Berlin
As the first superconducting rf photo-injector (SRF gun) in practice, the FZD 3+1/2 cell SRF gun is successfully connected to the superconducting linac ELBE. This setting will improve the beam quality for ELBE users. It is the first example for an accelerator facility fully based on superconducting RF technology. For high average power FEL and ERL sources, the combination of SRF linac and SRF gun provides a new chance to produce beams of high average current and low emittance with relative low power consumption. The main parameters achieved from the present SRF gun are the final electron energy of 3 MeV, 16 μA average current, and rms transverse normalized emittances of 3 mm mrad at 77 pC bunch charge. A modified 3+1/2 cell niobium cavity has been fabricated and tested, which will increase the rf gradient in the gun and thus better the beam parameters further. In this paper the status of the integration of the SRF gun with the ELBE linac will be presented, and the latest results of the beam experiments will be discussed.
BNL, Upton, Long Island, New York
AES, Medford, NY
PKU/IHIP, Beijing
RF electron guns with strained super lattice GaAs cathodes can produce higher brightness and lower emittance polarized electron beams, due to the higher field gradient at the cathode surface compared with DC guns. The vacuum in the gun must be better than 10-11 torr to obtain a sufficient cathode life time with high quantum efficiency (QE). Such high vacuum cannot be obtained easily in a normal conducting RF gun. We report on an experiment with a superconducting RF (SRF) gun, which can maintain a vacuum of nearly 10-12 torr because of cryo-pumping at the temperature of 4.2K . The GaAs cathode was activated by Cs'O treatment with a QE of 3% and exhibits a long lifetime in a preparation chamber. This cathode will be used in a 1.3 GHz - cell SRF gun to measure the destruction of the QE by ion and electron back-bombardment.
BNL, Upton, Long Island, New York
AES, Medford, NY
PKU/IHIP, Beijing
Superconducting RF (SRF) electron guns deliver higher brightness beams than DC guns because the field gradient at the cathode is higher. SRF guns with metal cathodes have been successfully tested. For the production of polarized electrons a Gallium-Arsenide (GaAs) cathode must be used, and an experiment to test this type of cathode is under way at BNL. Since the cathode will be normal conducting, the primary concern is cathode-driven heat load. We present measurements of the electric resistance of GaAs at cryogenic temperatures, a prediction of the heat load, and verification by measuring the quality factor of the gun with and without the cathode.
NSRRC, Hsinchu
Taiwan Photon Source (TPS) is a new third generation synchrotron storage ring which will be built at the present site of the NSRRC. The paper summarizes results of the impedance studies of the storage ring vacuum components for the TPS project. The main goal of this work was to support the design of the vacuum chamber and, at the same time, to get a detailed model of the machine impedance, which can be used later for detail studies of collective effects. Wake potentials and impedances for each component of the storage ring have been simulated with a 3D electromagnetic code GdfidL. Numerically obtained data have been compared to analytical results for simplified geometries of the vacuum chamber components.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The superconducting LINAC for the proposed New Light Source (NLS) project in the UK, will consist of 18 cryomodules operating at 1.8 K, each having 8, 1.3 GHz cavities operating in CW mode. The cryomodule design and cryogenic distribution scheme will be one of the key elements to achieve the desired performance from the superconducting RF (SRF) linac. Around the world, several large scale facilities (based on SRF linacs) are already operating (for example: CEBAF, SNS, FLASH) and several more have been proposed (XFEL, ILC, Cornell ERL, etc.). In this paper we define the requirements for an appropriate cryomodule, adopting proven L-band technology systems and also describe the cryogenic distribution scheme, in order to develop an effective and economic solution for the NLS.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
A design optimisation has been performed for an L-band, SRF linac adopting cryomodule technology developed as part of the TESLA Technology Collaboration (TTC). A conventional XFEL cryomodule has been adopted as a baseline design and modified to allow for CW operation at a nominally high Qo level. An assessment of appropriate operating gradient, based upon expected sub-system component costs and SRF linac operating costs, has been performed. The associated cryomodule modifications to accommodate such a large dynamic load are also highlighted, along with identifying an appropriate RF control architecture which can achieve the stringent phase and amplitude stability requirements for NLS.
KEK, Ibaraki
Kyungpook National University, Daegu
KNU, Deagu
Start-to-end (S2E) simulation from electron gun to beam dump is required to estimate light source performance and beam loss, which are essential parts in synchrotron light source based on Energy Recovery Linacs (ERL). Since the beam energy is widely varied from eV to GeV order in the ERL, the S2E simulation have to include many effects, e.g., space charge (SC) effect, coherent synchrotron radiation (CSR), cathode model, wake function, ions and beam break up. In order to carry out the S2E simulation, the preparation of it using General Particle Tracer (GPT), which is a particle tracking code including SC routine, has been started for compact ERL (cERL) beamline. The cERL is a test accelerator to establish accelerator technologies for GeV-class synchrotron light source based on ERL, and consists of an injector with photo cathode DC gun, a merger section, SRF cavities for acceleration and energy recovery, return loops, and a beam dump. In this presentation, the result of the S2E simulation from gun to the middle of return loop with SC and CSR effects, and the results of bench marking for each part in cERL, e.g. injector, merger, SRF cavities and return loop section, are shown.
SINAP, Shanghai
Shanghai KEY Laboratory of Cryogenics & Superconducting RF Technology, Shanghai
The superconducting RF system has been operated successfully in the storage ring of SSRF since July, 2008. The superconducting RF modules integrated with 310 kW transmitters and digital low level radio frequency (LLRF) control are adopted to provide about 4.5 MV cavity voltages to 3.5GeV electron beam. The operation status of SRF system is mainly reported here, the problems we met are analyzed, and the operation with normal conducting cavity systems is introduced briefly. The challenge for us is to improve the system reliability and machine performance.
DESY, Hamburg
The prototype of a camera system developed at KEK/Kyoto University for the optical inspection of the inner surface of cavities is in operation at DESY since September 2008. More than 20 prototype nine-cell cavities for the European XFEL have been inspected. The unique illumination system combined with the optical sensors allows for the in-situ search of surface defects in high resolution. Such defects may limit the gradient when causing a breakdown of the superconducting state (quench). The comparison of features detected in the optical inspection and hotspots from the temperature mapping during RF-measurements give evidence for correlations. Consecutive inspections of cavities in different stages of the surface preparation process monitor the evolution of surface defects. There are examples for defects traced from the untreated surface condition to the RF-test with temperature map, which identify the defect as the quench location.
KEK, Ibaraki
Ultra Finish Technology Co., Ltd., Yokosuka
Sokendai, Ibaraki
Niobium electropolishing for SRF cavities are generally considered to be the best technology today. However, hydrofluoric and sulphuric acid mixture usually used in the EP process is harmful and requires us carefully controlled handling of it and the many additional facilities. In this article, we propose a new application of electrochemical buffing onto niobium SRF cavity. In the method of electrochemical buffing, a rotating disk with abrasive fine particles where electrolyte is supplied is pressed against the workpiece. The disk and the work function as a cathode and an anode, respectively and an aqueous solution of sodium nitrate is used for the electrolyte. This technique brings us a couple of advantages like high etching rate, ultra small surface roughness, cost-effective and environment-compatible polishing.
Sokendai, Ibaraki
KEK, Ibaraki
Buffered chemical polishing (BCP) has been widely used as a final recipe of the surface treatment for niobium cavities and there is still much room to improve this technology since it is environment friendly, cheaper and simpler than electro-polishing. To examine BCPed surface in detail, we carried out BCP experiment followed by various rinsing methods on a series of niobium samples at KEK. As a result of the BCP process some contaminants like fluorine, carbon, etc. have been detected at the surfaces which may be the prominent cause of limiting the performance of SRF cavities. To remove these contaminants, various rinsing processes such as ultra pure water rinse, ultrasonic pure water rinse, alcoholic rinse, detergent rinse, high pressure water rinse (HPR) had been tested after the BCP. The preliminary results show that, only HPR had potential to mitigate these contaminants. In this article, we describe the surface analysis results using X-ray photo electron spectroscopy etc and a comparative study of niobium BCPed samples followed by above mentioned rinsing processes.
IHEP Beijing, Beijing
HJL, Beijing
BIAM, Beijing
Ningxia Orient Tantalum Industry Co., Ltd., Dawukou District, Shizuishan city
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 has been fabricated and surface treated at IHEP and will be tested at KEK. The fabrication procedure, surface treatment recipes as well as the SRF facilities are presented in this paper.
PKU/IHIP, Beijing
Peking University is striving for constructing a superconducting radio-frequency accelerator test facility (PKU-SETF) to provide coherent radiations [1]. A cryomodule consisting of a China made 9-cell TESLA type cavity was designed and constructed for this purpose, which is expected to provide 15-20 MeV energy gain at an operating temperature of 2K. Some technical issues in the manufacturing progress are reported, including the tungsten inert gas (TIG) welding of the LHe vessel and the superconducting cavity, the demagnetization of the vacuum vessel made of pure iron, and the manufacturing of the main power coupler.
KAERI, Daejon
PAL, Pohang, Kyungbuk
A superconducting RF cavity with a geometrical beta of 0.42 and a resonant frequency of 700 MHz has been under investigation for an extension program of Proton Engineering Frontier Project (PEFP) to accelerate the proton beam above 100 MeV. We developed and tested a two-cell prototype in order to confirm the fabrication procedure and check the RF and mechanical properties of such a low-beta elliptical cavity. The prototype has been fabricated with high RRR niobium sheets (RRR > 250). Double-ring structure was adopted to reduce the Lorentz force detuning effect. For the vertical test of the prototype cavity, a cryostat was designed and fabricated. Operating temperature is 4.2 K, therefore, pumping to reduce the pressure is not required. We applied 40 layers of superinsulation around the helium vessel in addition to the vacuum insulation between the helium vessel and outer chamber. The status of the prototype development and RF test results will be presented in this paper.
PAL, Pohang, Kyungbuk
The RF system for PLS-II upgrade, of which beam current and emittance are 400 mA and 5.6 nmrad at 3 GeV, becomes much more important compared to PLS. To reduce the HOM intensity in RF cavities for stable beam, a superconducting RF cavity is selected for the PLS-II. The RF system has to compensate beam loss power of 663 kW from 24 bending magnets, 20 insertion devices and other losses by RF HOM and broadband losses along vacuum chambers. For sufficient energy acceptance and lifetime the design RF voltage is 4.5 MV. Three 500 MHz superconducting cavities will be operated from October 2012, following successful commissioning with PLS NC cavities from July 2011. For the 3 SRF cryomodules, a 700 W class He cryogenic system will be prepared in 2011. The design of PLS-II SRF system including cryogenic system will be reported in the paper.
CERN, Geneva
Cockcroft Institute, Lancaster University, Lancaster
Niobium thin film cavities have shown good and reliable performance for LEP and LHC, although there are limitations to overcome if this technique should be used for new accelerators such as the ILC. New coating techniques like High Power Impulse Magnetron Sputtering (HiPIMS) has shown very promising results and we will report on its possible improvements for Nb thin film cavity performance. Current materials used in accelerator SRF technologies operate at temperatures below 4 K, which require complex cryogenic systems. Researchers have investigated the use of High Temperature Superconductors (HTS) to form RF cavities, with limited success*. We propose a new approach to achieve a high-temperature SRF cavity based on the superconducting 'proximity effect'**. The superconducting proximity effect is the effect through which a superconducting material in close proximity to a non-superconducting material induces a superconducting condensate in the latter. Using this effect we hope to overcome the problems that have prevented the use of HTS for accelerating structures so far. We will report the preliminary studies of magnetron sputtered thin films of Cu on Nb.
* E. J. Minehara et al, Superconductivity 3, p277 (1990)
** R. Seviour et al, Superlattices and Microstructures, 25, p647 (1999)
Fermilab, Batavia
Test facilities for high-gradient superconducting RF cavities must be shielded for particle radiation, which is generated by field emitted electrons in the cavities. A major challenge for the shielding design is associated with uncertainty in modeling the field emission. In this work, a semi-empirical method that allows us to predict the intensity of the generated field emission is described. Spatial, angular and energy distributions of the generated radiation are calculated with the Fishpact code*. The Monte Carlo code MARS** is used for modeling the radiation transport in matter. The detailed distributions of the generated field emission were used for studies with ILC-type superconducting RF cavities with accelerating gradients up to 35 MV/m in the Fermilab Vertical Cavity Test Facility. This approach allows us to minimize the amount of shielding inside cryostat which is an essential operational feature.
* E. Donoghue et al., Proc. SRF-2005, Ithaca NY, June 2005, TuP67.
** N. V. Mokhov and S. I. Striganov, Proc. Hadronic Shower Simulation Workshop, Batavia, Illinois, USA, 6-8 September, 2006.
Muons, Inc, Batavia
CLASSE, Ithaca, New York
Superconducting RF (SRF) systems typically contain unwanted frequencies or higher order modes (HOM). For storage ring and linac applications, these higher modes must be damped by absorbing them in ferrite and other lossy ceramic materials. Typically, these absorbers are brazed to substrates that are strategically located, often in the drift tubes adjacent to the SRF cavity. These HOM loads must have broadband microwave loss characteristics and be robust both thermally and mechanically, but the ferrites and their attachments are weak under tensile and thermal stresses and tend to crack. Based on existing work on HOM loads for high current storage rings and for an ERL injector cryomodule, a HOM absorber with improved materials and design will be developed for high-gradient 750 MHz superconducting cavity systems for storage ring and linac radiation sources. This work will build on novel construction techniques to maintain the ferrite in mechanical compression without brazing. 750 MHz RF system designs will be numerically modeled to determine the optimum ferrite load required to meet broadband loss specifications.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
The design and construction of electron-ion colliders will be facilitated by the development of an SRF "crab crossing" cavity with 0.5 to 1.5 GHz frequency and 20 to 50 MV integrated voltage. These RF cavities provide a transverse kick to the particle beam. Current state of the art crab cavities provide 2-5 MV of integrated voltage, and most of the existing designs require complex schemes to damp unwanted RF modes. We propose a novel system for implementing TEM-like two-bar structures. Two phase-locked sources 180° out of phase each drive a half-wavelength coax antenna inside of a cavity designed for the fewest possible unwanted modes. The cavity design will required a high-Q system composed of coax windows designed for maximizing the shunt impedance of the structure. A series of cavities could be installed in a beam line, and individual phase adjustment for each module will accommodate their longitudinal spacing and will provide the required integrated voltage.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
A superconducting RF (SRF) power coupler capable of handling 500 kW CW RF power is required for present and future storage rings and linacs. There are over 35 coupler designs for SRF cavities ranging in frequency from 325 to 1500 MHz. Coupler windows vary from cylinders to cones to disks, and RF power couplers are limited by the ability of ceramic windows to withstand the stresses due to heating and mechanical flexure. We propose a novel robust co-axial SRF coupler design which uses compressed window technology. This technology will allow the use of highly thermally conductive materials for cryogenic windows. Using compressed window techniques on disk co-axial windows will make significant improvements in the power handling of SRF couplers. We present the bench test results of two window assemblies back to back, as well as individual window VSWR in EIA3.125 coax. A vacuum test assembly was made and the windows baked out at 155C. The processes used to build windows is scalable to larger diameter coax and to higher power levels.
CLASSE, Ithaca, New York
The high magnetic and electric radio-frequency fields in superconducting microwave cavities cause heating of the inner cavity surface and generate Lorentz-forces, which deform the shape of the cavity and thereby result in a shift of the fundamental mode frequency. 3-dimensional numerical codes can create complex coupled simulations of the electromagnetic fields excited in a cavity, of heat dissipation and heat transfer, as well as of mechanical effects. In this paper we summarize our simulation results using the engineering simulation package ANSYS.
CLASSE, Ithaca, New York
Cornell University has developed and fabricated a SCRF injector cryomodule for the acceleration of a high current, low emittance beam in the Cornell ERL injector prototype. This cryomodule is based on superconducting rf technology with five 2-cell rf cavities operated in the cw mode, supporting beam currents of up to 100 mA. After a rework of this cryomodule in 2009 to implement several improvements, it is now in beam operation again. In this paper we report on latest results and discuss future test plans.
SLAC, Menlo Park, California
Superconducting RF is increasingly important for particle accelerators. A lot of effort has been made in the SRF material research recently, aiming to find the superconducting materials with better performance. We developed a testing system using a resonant cavity with high quality factor and an interchangeable wall for the testing of different materials. The system is capable for high power RF cryogenic test to find the critical magnetic field at different temperature. The facility can be also used on testing the low temperature properties of the normal conducting material. Different Cu, Nb and MgB2 samples have been tested. In this paper, we will present the most recent development of the system, along with a discussion on the recent testing results.
JLAB, Newport News, Virginia
The College of William and Mary, Williamsburg
ODU, Norfolk, Virginia
NSU, Newport News
In the past years, energetic vacuum deposition methods have been developed in different laboratories to improve Nb/Cu technology for superconducting cavities. Jefferson Lab and collaborators are pursuing energetic condensation deposition via Electron Cyclotron Resonance. As part of this study, the influence of the deposition energy, the coating temperature and the substrate's nature on the material and RF properties of the Nb thin film is investigated. The film surface and structure analyzes are conducted with various techniques like X-ray diffraction, Transmission Electron Microscopy, Auger Electron Spectroscopy and RHEED. The microwave properties of the films are characterized on 50 mm disk samples with a 7.5 GHz surface impedance characterization system. This paper presents surface impedance measurements in correlation with surface and material characterization for Nb films produced on various substrates with different bias voltages. Emerging opportunities for developing multi-layer superconducting rf films are also highlighted with the commissioning results of a new deposition system.
ODU, Norfolk, Virginia
JLAB, Newport News, Virginia
Plasma based surface modification provides an excellent opportunity to eliminate non-superconductive pollutants in the penetration depth region of the SRF cavity surface and to remove mechanically damaged surface layer improving surface roughness. We have demonstrated on flat samples that plasma etching in Ar/Cl2 of bulk Nb is a viable alternative surface preparation technique to BCP and EP methods, with comparable etching rates. The geometry of SRF cavities made of bulk Nb defines the use of asymmetric RF discharge configuration for plasma etching. In a specially designed single cell cavity with sample holders, discharge parameters are combined with etched surface diagnostics to obtain optimum combination of etching rates, roughness and homogeneity in a variety of discharge types, conditions, and sequences. The optimized experimental conditions will ultimately be applied to single cell SRF cavities.
JLAB, Newport News, Virginia
PKU/IHIP, Beijing
Recent experimental results have indicated that Buffered Electropolishing (BEP) is a promising candidate for the next generation of surface treatment technique for Nb superconducting radio frequency (SRF) cavities to be used in particle accelerators. In order to lay the foundation for using BEP as the next generation surface treatment technique for Nb SRF cavities, some fundamental aspects of BEP treatments for Nb have to be investigated. In this report, recent progress on BEP study at JLab is shown. Improvements on the existing vertical BEP are made to allow water cooling from outside of a Nb single cell cavity in addition to cooling provided by acid circulation so that the temperature of the cavity can be stable during processing. Some investigation on the electrolyte mixture was performed to check the aging effect of the electrolyte. It is shown that good polishing results can still be obtained on Nb at a current density of 171 mA/cm when the BEP electrolyte was at the stationary condition and was more than 1.5 years old.
* A.T. Wu et al, Proc. of 14th Conference on SRF, Germany, 2009, THPPO064. ** S. Jin et al, the same as 1, THPPO097.
*** F. Eozenou et al, the same as 1 THPPO068.
JLAB, Newport News, Virginia
PKU/IHIP, Beijing
NSU, Newport News, Virginia
Field emission is still one of the major obstacles facing Nb superconducting radio frequency (SRF) community for allowing Nb SRF cavities to reach routinely accelerating gradient of 35 MV/m that is required for the international linear collider. Nowadays, the well know low temperature backing at 120 oC for 48 hours is a common procedure used in the SRF community to improve the high field Q slope. However, some cavity production data have showed that the low temperature baking may induce field emission for cavities treated by EP. On the other hand, an earlier study of field emission on Nb flat samples treated by BCP showed an opposite conclusion. In this presentation, the preliminary measurements of Nb flat samples treated by BEP, EP, and BCP via our unique home-made scanning field emission microscope before and after the low temperature baking are reported. Some correlations between surface smoothness and the number of the observed field emitters were found. The observed experimental results can be understood, at least partially, by a simple model that involves the change of the thickness of the pent-oxide layer on Nb surfaces.
* L.C. MacIntyre, R. Ike, and A.T. Wu, 2005, unpublished
ODU, Norfolk, Virginia
JLAB, Newport News, Virginia
The tomographic reconstruction of local plasma parameters for nonequilibrium plasma sources is a developing approach, which has a great potential in understanding the fundamental processes and phenomena during plasma processing of SRF cavity walls. Any type of SRF cavity presents a plasma rector with limited or distorted symmetry and possible presence of high gradients. Development of the tomographic method for SRF plasma analysis consists of several steps. First, we define the method based on the inversion of the Abel integral equation for a hollow spherical reactor. Second step is application of the method for the actual elliptical cavity shape. Third step consists of study of the effects of various shapes of the driven electrode. Final step consists of testing the observed line-integrated optical emission data. We will show the typical results in each step and the final result will be presented in the form of correlation between local plasma parameter distributions and local etching characteristics.
BNL, Upton, Long Island, New York
The damper of 56 MHz cavity is designed to extract all modes to the resistance load outside, including the fundamental mode. Therefore a high-pass filter is required to reflect the fundamental mode back into the cavity. A preliminary design of the filter was previously done. In this paper, we optimize all elements to eliminate the poor filter performance above 1 GHz. The circuit diagram is extracted from microwave lumped elements that reproduce the frequency spectrum of the finalized filter. We also show mode damping results with dampers and filters in the desired configuration, determining the final performance of the cavity.
KEK, Ibaraki
We have started high gradient R&D with the combination of ICHIRO shape, sliced large grain niobium, and chemical polishing (CP). We fabricated one large grain ICHIRO single cell cavity that had end cell shape of ICHIRO 9-cell but no end group. We processed this cavity surface by centrifugal barrel polishing (CBP) and CP. This cavity successfully achieved the high gradient of 42MV/m at the first vertical test. We made series test by repeating CP on this cavity. The results of series test will be reported.
KEK, Ibaraki
In our high gradient R&D of ICHIRO cavities at KEK, we have found some problems related to HOM coupler and high power RF input coupler port on beam tube: end group. One is the difficulties of rinsing in complex structures like HOM coupler. The other is Q-slope at high filed more than 40MV/m. The cavities without end group did not show such a high field Q-slope. At first step, we tested much stronger and aggressive rinsing method; wiping, brushing, and mega-sonic rinsing, against end group. The details and results of these rinsing effects will be reported.
KEK, Ibaraki
Dr. Matsumoto in KEK and his colleague have developed the MO flange for vacuum sealing of normal conducting high peak power RF wave-guide. This is impedance free sealing. We have applied this sealing to SRF cavity technology instead of indium sealing. We used pure aluminum gasket for the sealing material. We had a difficulty on the titanium flange but succeeded to establish leak tightness in super-fluid Helium by stainless flange. In this paper, we will report the R&D results.
KEK, Ibaraki
We are developing LL high gradient SRF cavity for ILC. Recently we have observed a Q-slope problem at higher gradient over 35-40MV/m on the full end single cell cavities, which have a HOM coupler and an input coupler on a beam tube. This problem might be due to poor rinsing in such a complicate structure. We have studied to strengthen cleaning by improvement of the nozzle shape used high pressure water rinsing, inside ultrasonic cleaning, steam cleaning, and so on. In this paper we will report these results.
KEK, Ibaraki
We are developing large grain/single crystal niobium material for ILC collaborating with Tokyo Denkai. These materials are very much promising to obtain high SRF cavity performance with cost-effective production. We have fabricated two 9-cell cavities from these large grain niobium materials and made cold test to evaluate the SRF performance. In this paper, we will report cavity fabrications and preparations and cold test results.
Sokendai, Ibaraki
KEK, Ibaraki
We have designed Demountable Damped Cavity (DDC) for ILC main linac. DDC has two design concepts. One is the coaxial waveguide for HOM damping, which can strongly couple HOM's. Accelerating mode is reflected by a choke filter. The axial symmetry can reduce the beam kick effect. The other concept is demountable structure which can make easy cleaning of end group in order to suppress the Q-slope problem at a high field. In this paper we will report the RF design and measurement results in model cavity.
IHEP Beijing, Beijing
IHEP Beiing, Beijing
1.3 GHz superconducting radio-frequency (SRF) technology is one of the key technologies for the ILC and future XFEL / ERL projects of China. With the aim to develop this technology, IHEP has started a program to build an SRF Accelerating Unit in the frame of ILC collaboration. The SRF Accelerating Unit contains a 9-cell 1.3 GHz superconducting cavity, a short cryomodule, a high power input coupler, a tuner, a low level RF system and a high power RF source, etc. The unit can undergo beam test and used as the booster for any SRF linac based test facility. Recent progress of the components R&D is presented.
CERN, Geneva
GSI, Darmstadt
The Chair and Deputy will receive the award of the IPAC'10 Organizing Committee on behalf of the JACoW Collaboration.
FZD, Dresden
TU Dresden, Dresden
The superconducting linear accelerator ELBE at the Forschungszentrum Dresden/Rossendorf has two superconducting accelerator modules and a superconducting photo injector (SRF-Gun). They are operated by a cryogenic Helium plant with a cooling power of 200 W at 1.8 K. Since the commissioning of the plant in 1999 minor and major impurity problems have influenced the operation stability of the plant. The presentation will give an overview of the ELBE cryogenic system and will focus on the different sources of plant contamination and their effects on the plant operation which have been found during the nearly 10 years of plant lifetime. Especially the contamination with residues of oil brake up so as air and water from different sources have limited the run periods of the plant and effected special service and maintenance procedures.
NSRRC, Hsinchu
NEXANS Deutschland Industries AG & Co. KG, Moenchengladbach
The National Synchrotron Radiation Research Center is constructing the Taiwan Photon Source (TPS), a 3-GeV synchroton facility. The superconducting radio frequency (SRF) cavity modules are selected as the accelerating cavities in the electron storage ring. A test area for the SRF modules is established in the RF laboratory, which includes cryogenic environment, RF transmitter, low level RF control system, and radiation shielded space. The liquid helium is transferred from the cryogenic plant in the experimental area of the Taiwan Light Source (TLS), which is not only far from the RF laboratory but also characterized by a complicated route of 205 meters. The main concerns on the cryogenic transfer are the installation difficulty, heat loss, two-phase flow, and pressure loss. Instead of a multi-channel transfer line, which would request a long installation period on radiation-restrict area, flexible cryogenic transfer lines from Nexans were chosen. The installation period was dramatically reduced to one week. With a test Dewar in the RF lab and valve boxes on both ends of the transfer lines, a long distance cryogenic transfer system was completed and proved to work functional.
NSRRC, Hsinchu
The TPS is 3 GeV photon source under construction in Taiwan. The electron needs four superconducting RF cavities to maintain the energy. The construction of a new refrigeration/liquefaction helium plant is under way to supply the liquid helium for superconducting RF cavities. This is the third year of the seven years project and part of the design features and parameters is different from the prilimilary design. This paper presents the design of the cryogenic system, which is including the features of the new cryogenic plant, the pressure drop of warm helium pipeline, the distribution valve box and the multichannel line. The design of liquid nitrogen supply line and the phase separator will be also included.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The proposed New Light Source (NLS) based on a CW superconducting linear accelerator requires large scale cryogenic refrigeration equipment comparable to some of largest installations around the world (for example CEBAF/SNS and LHC). The maximum refrigeration power requirement is estimated to be 3.4 kW at 1.8 K. The ratio of the dynamic to the static heat load is in excess of 20 and handling such large variations in the refrigeration power is the key issue in the development of the cryogenic system for NLS. In this paper we present our approach to address the issues relating to efficient and reliable operability, operational functionality and capital costs, in order to develop an effective and economic solution for NLS.
DESY, Hamburg
JLAB, Newport News, Virginia
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
BNL, Upton, Long Island, New York
In this contribution, we report Quantum Efficiency (QE) test results with a hybrid lead/niobium superconducting RF (SRF) photoinjector at 2K and new Pb arc deposited cathodes at 300K. The ultimate goal of our effort is to build a Nb injector with the superconducting cathode made of lead, which, as reported in the past, demonstrated superior QE compared to other metallic superconducting elements. At first, we present the test results obtained with a 1.6-cell high purity Nb cavity with the emitting lead spot in the center of the back plate. The QE test results at room temperature and the SEM surface analysis of eight Pb cathodes, deposited recently under various conditions, are discussed in the second part of this contribution.
CERN, Geneva
SLAC, Menlo Park, California
In this paper, we present a lattice design for the Large Hadron Electron Collider (LHeC) recirculating Linac. The recirculating Linac consists of one roughly 3km long linac hosting superconducting RF (SRF) accelerating cavities, two arcs and one transfer line for the recirculation. Electron beam will have two passes in the SRF linac to get a maximum energy of 140 GeV, or have four passes with a maximum energy of 60 GeV (two for acceleration and two for deceleration) in the Energy Recovery Linac (ERL) option.
CERN, Geneva
SLAC, Menlo Park, California
In this paper, we estimate the emittance growth in the LHeC recirculating Linac, the lattice design of which is presented in another paper of IPAC10 proceedings. The possible sources for emittance growth included here are: energy spread from RF acceleration in the SRF (superconducting RF) linac plus large chromatic effects from the lattice, synchrotron radiation (SR) fluctuations in the recirculating arcs. 6-D multi-particle tracking is launched to calculate the emittance from the statistical point of view. The simulation results are also compared with a theoretical estimation.