DESY, Hamburg
The internationally organized European XFEL free-electron laser is under construction at the Deutsches Elektronen-Synchrotron (DESY). The project is the first large scale application of the TESLA technology developed over the last 15 years. Superconducting accelerating cavities will be used to accelerate the electron beam to an energy of up to 17.5 GeV. Recently an energy reduction by 20% to 14 GeV was discussed as a reasonable compromise between cost aspects and scientific potential of the facility. With realistic assumptions on lower beam emittance, the design photon beam parameters will be achieved. The talk will briefly summarize the overall XFEL design before presenting details about the status of the superconducting linac. The activities within the international collaboration will be described. Final prototyping, industrialization and commissioning new infrastructure are the actual challenges. Contracts for long lead items are placed.
Fermilab, Batavia
Muons, Inc, Batavia
In the last 20 years, superconducting RF (SRF) cavities have been developed to the point that a CW SRF linac is the best candidate driver for subcritical reactors. We discuss how one appropriately designed 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. Such a station will generate no greenhouse gases, produce minimal nuclear waste and no byproducts that are useful to rogue nations or terrorists, incinerate waste from conventional nuclear reactors, and efficiently use abundant thorium fuel that does not need enrichment. 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.
Fermilab, Batavia
The High Intensity Neutrino Source (HINS) R&D program requires super conducting single spoke resonators operating at 325 MHz. After coupler installation, these cavities are tested at the HINS-SRF facility at Fermilab. The LLRF requirements for these tests include support for continuous wave and pulsed mode operations, with the ability to track the resonance frequency of the tested cavity. Real-time measurement of the cavity loaded Q and Q0 are implemented using gradient decay techniques, allowing for Q0 versus Eacc plots. A real time cavity simulator was also developed to test the LLRF system and verify its functionality.
KEK, Ibaraki
Nagoya University, Nagoya
MO sealing developed by Prof. H. Matsumoto in KEK and his collaborator M. Ohotsuka has been successfully applied to SRF cavities. Its leak ratio is smaller than 3·10-8 Pam3/s or much better in the superfluid Helium, which is the allowed level to successfully measure the cavity performance for more than 3 hours at 2K. Tightening torque is 15Nm and the bolt material is SUS304 (JIS). Titanium is usable as cavity flange material. Copper looks better than pure Aluminium as the gasket material. We have observed an additional residual surface resistance about 5nΩ Zero impedance characteristics of the MO sealing is a remained issue. In this paper we report the results in detail.
JLAB, Newport News, Virginia
Energy Recovering Linacs have become an important approach to providing high brightness electron beams for photon production, nuclear physics research, and cooling ions. The technology takes advantage of the ability of superconducting rf cavities to accelerate high average current beams with low losses. After the desired interaction the electrons can be decelerated to low energy so as to minimize the required rf power and electrical draw. When this approach is coupled with advanced continuous wave injectors, very high power, ultra-short electron pulse trains of high brightness can be achieved. This talk will review the status of worldwide programs including the on-going BNL and Cornell efforts, the Novosibirsk Multipass ERL, ALICE at Daresbury, the KEK/JAEA ERL, and the Peking ERL among others. We will also touch on the prospects for proposed machines such as the JLAMP advanced ERL FEL efforts at Jefferson Lab designed to produce ultra-high brightness beams of photons in the 10-100 nanometer soft X-ray region.
CLASSE, Ithaca, New York
The Cornell Energy Recovery Linac (ERL) Injector cryomodule is part of a prototype electron beam source to demonstrate production of CW 1.3 GHz, 100 mA average current, 2 ps, 77 pC bunches with emittance of 1 mm-mrad. After a successful initial run of the cryomodule with beam, an improvement program was initiated in the Fall 2009. The goals of the reconfiguration were to replace the RF absorbers in the beamline HOM loads that were subject to static charging, re-process the SRF cavities that exhibited a low Q that further decreased by 50% during the run, and improve diagnostic sensor accuracy within the cryomodule. The upgraded cryomodule was re-commissioned in early 2010 with excellent performance. Details of the investigation and remedies for HOM load charging, cavity Q recovery, and module assembly logistics will be presented along with the ERL Injector beam performance.
HZB, Berlin
Energy recovery linacs (ERLs) are proving to be a powerful option to provide very high current beams with exceptional beam parameters and the flexibility to tailor these for many applications, from next-generation light sources to electron coolers. Helmholtz Zentrum Berlin (HZB) is focusing on ERLs for future x-ray light sources. Although ERL facilities exist for the IR and THz range, their moderate parameters (current, emittance, energy) are insufficient for future x-ray sources. HZB is therefore proposing to develop the 100-MeV ERL facility BERLinPro for accelerator studies and technology development to demonstrate the feasibility of an x-ray user facility. This paper presents an overview of the project and the key components of the facility.
DESY, Hamburg
JLAB, Newport News, Virginia
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
The European XFEL will use superconducting TESLA cavities operating with 650 μs long bunch trains. With 220 ns bunch spacing and 10 Hz RF-pulse repetition rate up to 27000 high quality bunches/s will be delivered to insertion devices generating unprecedented high average brilliance photon beams at very short wavelength. While many experiments can take advantage of full bunch trains, others prefer an increased several μ-seconds intra pulse distance between bunches, or short bursts with kHz repetition rate. With the nominal RF-pulse structure these features will lead to a substantially reduced number of bunches per second and therefore to significantly lower average brilliance. We discuss here an R&D program aiming for a far future upgrade of the European XFEL; operation in the cw and/or near-cw mode. The program profits from the continuous improvement in performance of TESLA cavities, which allows for longer RF-pulses in comparison with the current design. We present test results of a SRF electron injector and a new RF-power source, and some modification of the HOM damping scheme, which will avoid the necessity of re-assembly of the XFEL accelerator for the upgraded operations.
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.
Fermilab, Batavia
Fermilab has produced two cryomodules for superconducting RF (SRF) applications to date. The first of these is an ILC prototype containing eight 1.3 GHz Tesla-type cavities and a superconducting quadrupole. This cryomodule is of the 'Type 3+' design developed by the TESLA collaboration. The assembly of this cryomodule was accomplished at Fermilab with much assistance from DESY and INFN-Milano. The cryomodule was tested at Fermilab in the summer of 2010. The second cryomodule produced at Fermilab contains four 3.9 GHz nine-cell cavities. The cavities and cryomodule were designed at Fermilab; the design concepts are quite similar to the 1.3 GHz Type 3+ cryomodule. This cryomodule was shipped to DESY, tested, and is now operating as part of a third-harmonic system in the FLASH facility. Fermilab plans to build five more 1.3 GHz cryomodules over the next several years for a total of six, which will be installed and operated in the New Muon Lab beam test facility at Fermilab.
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.
HZB, Berlin
A review of the SRF and cryomodule R&D for various ERL projects around the world. Many challenging R&D problems will be addressed such as high average current SRF injectors and CW high gradient SRF modules.
CEA, Gif-sur-Yvette
Recent developments and promising results are showing the feasibility of 1 MW power couplers for superconducting cavities accelerating high intensity proton beam for projects such as SPL, ESS, EURISOL.
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.
Fermilab, Batavia
ANL, Argonne
The superconducting RF (SRF) cavity production program at Fermilab supports 9-cell 1.3 GHz cavity qualification and preparation for assembling cavities into cryomodules, in support of Project X, ILC, or other future projects. Cavity qualification includes cavity inspection, surface processing, clean assembly, and one or more cryogenic qualification tests which typically include performance diagnostics. The overall goals of the program, facilities and accomplishments are described.
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.
LANL, Los Alamos, New Mexico
JLAB, Newport News, Virginia
An update on the study of 805 MHz elliptical SRF cavities that have been optimized for high gradient will be presented. An optimized cell shape, which is still appropriate for easy high pressure water rinsing, has been designed with the ratios of peak magnetic and electric fields to accelerating gradient being 3.75 mT/(MV/m) and 1.82, respectively. A total of 3 single-cell cavities have been fabricated and tested with various conditions. In addition, a 6-cell cavity design has been completed including multipacting simulations.
LANL, Los Alamos, New Mexico
SLAC, Menlo Park, California
STI, Santa Barbara, California
In order to overcome the theoretical limit of ~200 mT peak surface magnetic field for niobium SRF cavities, an idea of coating multi-layer thin film superconductors separated with thin dielectric layers has been suggested. We are testing MgB2, NbN and NbC as candidates for the realization of this idea. The results of surface characterization, Auger depth profile, DC magnetization measurements with SQUID, low- and high-field measurements with a TE013-like mode copper cavity coupled with a 11.4 GHz short-pulse Klystron will be presented.
FZD, Dresden
To fulfil the demand of future high power and high luminosity FEL and Storage Ring sources, an intensive electron beam with short bunch length, small emittance and large bunch charge is required. Laser driven superconducting radio frequency (SRF) photocathode guns in combination with SRF LINACs appear to be the best solution. First long term operation was demonstrated at the FZD*. In difference to the normal conducting guns, the application of static magnetic fields is not possible. Instead, the use of a transverse electric (TE) mode in parallel to the accelerating mode was proposed. Numerical simulations have shown that such RF focusing can be applied to compensate emittance growth**. This contribution will introduce a possibility to use the existing coaxial RF coupler of TESLA like cavities, as RF power input for TE modes in parallel. An additional coupler component outside the module satisfies the job of combining two frequencies from different sources to one load. Thus, it corresponds to the working principle of a high power RF diplexer. Based on the 3 1/2 cell FZD SRF gun, a concrete technical implementation and results of its operation at the cold cavity will be presented.
* J. Teichert et al., AIP Conf. Proc. 1149, 1119 - 1124 (2009).
** K. Flöttmann, D. Janssen, V. Volkov, Phys. Rev. ST Accel. Beams 7, 090702 (2004).
ANL, Argonne
An upgrade project is underway at the ATLAS superconducting RF (SRF) heavy-ion linac at Argonne National Laboratory to dramatically increase the intensity of both stable beams and short-lived isotopes from the CARIBU fission source. The upgrade includes a new normal conducting RFQ injector and an SRF cryomodule consisting of seven high-performance 72.75 MHz quarter-wave cavities optimized for ions with velocity of 0.077c. The module will deliver more than 17.5 MV of accelerating potential over 5 meters and replace three existing split-ring cryomodules. Key to this performance will be a new cavity fast tuning system that replaces the voltage-controlled-reactance (VCX) fast tuner. The recently completed ATLAS upgrade cryomodule installed in June 2009 has a real estate gradient of 14.5 MV over 4.6 meters, the highest for any low-beta cryomodule, however, performance is 40% less than could be achieved without the VCX. As such, the VCX is being replaced with a high-power rf coupler and a fast piezoelectric-based tuner to be used together to control the cavity phase. Cold test results of a prototype power coupler and piezo-tuner are presented here.
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.