CURRENT INDUSTRIAL SRF CAPABILITIES AND FUTURE PLANS

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1 CURRENT INDUSTRIAL SRF CAPABILITIES AND FUTURE PLANS Hanspeter Vogel ACCEL Instruments GmbH Friedrich Ebert Strasse 1, Bergisch Gladbach, Germany Corresponding author: Hanspeter Vogel ACCEL Instruments Friedrich Ebert Strasse Bergisch Gladbach, Germany Phone: FAX: vogel@accel.de ABSTRACT Industrial capabilities in view of SRF technology for accelerators cover design, engineering, manufacturing, preparation, test, assembly, and support for taking components and systems into operation. Capabilities will be presented by showing various examples of past and present activities. Future plans in Industry are driven by application of SRF technology in an increasing number of projects in different scale and scope, covering Synchrotrons, small linacs for FEL, up to the X-FEL linac or the ILC. Keywords: Industrial capabilities, SRF technology, Design, Engineering, Manufacturing, Industry.

2 1. INTRODUCTION Industrial capabilities in the field of superconducting radio frequency (SRF) technology for accelerators cover a wide range starting with design and engineering, covering manufacturing, preparation, and testing of SRF cavities and components and finally performing assembly of SRF accelerating modules and installation of complete accelerators at the customers site with taking the accelerator into operation and personnel training. A variety of components are required to build complete SRF modules and SRF accelerators, some of them are standard items, some of them are considered key-components like cavities or rf-couplers. Beside the more general aspects of design and engineering the focus within this review is laid on the key components mentioned above for manufacturing, preparation, testing, and assembly technology. Future planning in industry is depending on the development of projects and application of SRF technology. A review of today s industrial capabilities is given focused on tasks like supporting planning and research, prototype production, and studies in cases of large scale project like the international linear collider (ILC) or the X-FEL project at DESY. 1

3 2. DESIGN OF SRF MODULES AND ACCELERATORS Based on the increasing demand of SRF technology for accelerator projects from not only the institutions with a strong background in SRF R&D, but also from customers and projects with less SRF experience a few specialized companies have built up the capabilities for supporting SRF based projects with increasing design capabilities and resources. The design of complete accelerator modules includes not only the detailed rf design and layout of the cavity, but also the mechanical and the cryogenic layout of the auxiliary components involving other related disciplines like vacuum and cryogenic technology, mechanical aspects Figure 1: the 3 nd harmonic srf Landau module for BESSY and systems technology. As a typical example the completely turn-key delivered Landau- Module is described here, a SRF accelerator module based on a scaled version of the CESR II type cavity, that was delivered to BESSY [1]. The parameters of this accelerating module are summarized in table 1. The available space in the BESSY storage ring limited the overall length of the module to below 800 mm. Nevertheless the cryogenic standby losses of the module were designed to be below 10 Watt by counter flow heat exchangers at the beam tubes, a design that was confirmed later by the measurements. Concerning the cavity design for this particular application the 500 MHz CESR design was scaled to 1,5 GHz including auxiliary components like in-vacuum HOM loads, and a piezo driven tuning system. After cavity manufacturing, preparation with buffered chemical polishing (BCP) and high pressure water rinsing (HPR) a cryogenic rf test was performed at DESY to prove the required performance. 2

4 The cavity was subsequently assembled with all other module components and delivered to BESSY were the cryogenic test of the module was conducted. Frequency 1500 MHz, Mono mode Cavity r/q (V 2 acc/2p diss ) 45.4 Ω V acc 500 kv (5MV/m) I max 500 ma Tuning Range +/- 600 khz Op. temperature 4.5 K Unloaded Q 2.2*10 8 Stand by losses < 10 W Diss. rf power 12.5 W HOM absorber Ferrite loads at room temperature Total length 800 mm Table 1: Parameters of the 3 rd harmonic Landau-Module for BESSY Beside the application in electron linear accelerators and storage rings SRF technology is used in several operating and proposed linear accelerator for light and heavy ions such as ALPI at Legnaro National Laboratory, ATLAS at Argonne National Laboratory, ISSAC at TRIUMF, the Indus project., and the proposed LINAG at GANIL and RIA in US. Furthermore a 40 MeV proton and deuteron linear accelerator in under construction at SOREQ, Israel, based on a complete turn-key supply by ACCEL[2]. Within this project detailed studies were performed resulting in a accelerator design with Figure 2: SRF module with half wave resonators for a 40 MeV proton deuteron linear accelerator superconducting half wave resonators (HWR) for the linac at a particle energy as low as 1,5 MeV/u after particle generation with a standard ECR source and first acceleration and bunching with a radio frequency quadrupole (RFQ) operated in cw mode. Detailed beam dynamics simulation for the complete linac resulted in the layout of the various cavities to accommodate the increasing particle velocity, the two different particle species (protons and deuterons) and the arrangements of accelerating cavities and focusing elements. Figure 2 shows the design of the SRF module with 6 HWR and 3 superconducting solenoids for 3

5 focusing. Figure 3 shows the results of the beam dynamic simulations. Figure 3: beam dynamic simulation for the 40 MeV proton linace showing expected longitudinal emittance and envelope (upper graph) and the transversal emittance (lower graph). Both safely below the target values 3. ENGINEERING OF SRF MODULES AND COMPONENTS Detailed engineering for SRF modules and components is performed in industry either based on developments made in institutes or based on a close cooperation with institutes developing and applying SRF technology. For the electron cooler project at Brookhaven National Laboratory [3] a SRF module with a 700 MHz 5 cell cavity is developed by Advanced Energy Systems (AES) Figure 4: SRF module with a 700 MHz five cell cavity for the BNL Electron Cooler Project as shown in figure 4. 4

6 ACCEL is delivering and offering a SRF module based on the cavities of the TESLA collaboration and the module developed by Forschungzentrum Rossendorf (FZR)[4] under a license agreement. This module houses two TESLA type cavities and was developed for cw operation. After a detailed in house engineering review two such modules are under fabrication for the 4GLS project at Daresbury (GB)[5]. Figure 5 shows the module which will be delivered with guaranteed performance for accelerating field, cavity Q, rf power, and cryogenic parameters. The guaranteed performance in view of the accelerating gradient has been agreed for 25 MV per module. Performance results of TESLA cavities produced and completely prepared (BCP, HPR) at industry are presented in chapter 5. Figure 5: srf accelerating module based on the TESLA cavities, designed for cw operation (Forschungszentrum Rossendorf) 5

7 4. MANUFACTURING OF SRF CAVITES AND MODULES 4.1 CAVITY PROTOTYPING SRF technology is migrating from its original applications with spherical cavities for acceleration of electrons or high beta ions, HWR, QWR, or spoke-shaped cavities for the low velocity ions into new applications. University of Frankfurt has developed a CH mode cavity for ion acceleration with 18 spokes as shown in figure 6 and 7. Fig 6 shows the 3D layout of this cavity and the alternating arranged spokes in the cavity and fig 7 the central part of the cavity with these spokes before completion with the end caps[6]. Figure 7: view into the central part of the cavity before closing with end caps (cmp fig. 6) Figure 6: 3D layout of the CH Mode cavity developer by University of Frankfurt For the manufacturing planning of this cavity the manufacturing sequences for niobium forming, machining, welding, rf-measurements, and intermediate testing has been extensively analyzed. Additional developments for the tooling and fixtures were necessary for the actual production steps. A similar challenging project was the development of a 3 ½ cell cavity based on TESLA technology for a SRF photocathode Electron-Gun (Design FZ Rossendorf [7]) with improved focusing of the electron beam by a superposed TE Mode. The specific feature of this design required a complex mechanical design to allow independent tuning of the accelerating cells and the TE-mode cell. Fig. 8 shows the details of 6

8 this arrangement with the TESLA shaped cell and the special TE-mode cell and the braces for later attachment of a mechanical tuning system. 4.2 SERIES PRODUCTION OF SRF CAVITIES Figure 8 : srf photogun cavity developed by Forschungszentrum Rossendorf The recently completed series production of SRF cavities comprises a total of 109 cavities for the superconducting part of the linear accelerator for the Spallation Neutron Source (SNS) in Oak Ridge, US[8]. Fig. 9 shows a medium beta SNS cavity in comparison with a TESLA cavity. The production of these 109 cavities comprised the following steps Optimization of manufacturing technologies Manufacturing Figure 9: medium beta cavity for the SNS linac (above) compared with a TESLA cavity (below) RF Measurements (tuning, Qext) BCP (internal, external), Guaranteed performance 7

9 and can be characterized by the following schedule. After about a one year of ramp-up of the production (first article production, tooling develpment) 2 types of cavities (medium and high Beta) were delivered with a mean delivery rate of 4 Cavities / Month during the project running time between 08/2001 and 08/2004. Further examples of series production are the 360 cavities for the CEBAF project at Jefferson Laboratory, the series production of about 240 cavities for the LEP project at CERN, using the CERN developed niobium sputter technology, and the almost 80 TESLA cavities produced so far. 4.3 TURN-KEY ACCELERATING MODULES Turn-key accelerating modules have been and will be delivered from industry on a regular basis. These deliveries are based on the design provided by the applying research laboratory as in previous projects like the LEP storage ring at CERN in Geneva. In this case CERN included European industry in the technology transfer and series production for the accelerating modules which have been produced following the CERN developed sputter technology. Other SRF modules are developed and delivered based on industrial in house engineering capabilities and the vital cooperation with leading institutions in SRF technology. As an example the cooperation and technology transfer agreement with CORNELL University is described here which forms the basis for ACCEL production of 500 MHz accelerating modules for storage rings or synchrotron light sources [9]. These single cell 500 MHz modules are based on the CESR II design, that was re-engineered and meanwhile delivered to CORNELL (2 modules), the Taiwan Light Source (NSRRC, 2 modules), and the Canadian Light Source (CLS, 2 modules). The modules are operating since more than?? years now without problems. DIAMOND Light Source (DLS, 3 modules) has also decided to use SRF modules for the synchrotron and 3 modules will be delivered during 8

10 the year Fig 10 shows the accelerating module with the electronic racks housing low level rf control system and instrumentation. In addition the cryogenic valve box housing the control LHe input and gas return control valves for the supply of the cryogenic liquids. The valve operation is controlled directly by the sensors in the module and forms part of the integrated cryogenic control system. Figure 10: complete turn-key accelerating system for storage rings based on CESR 500 MHz technology. Center: SRF Module Left: cryogenic distribution valve box Right: Electronic controls for rf, instrumentation, and cryogenics 5. PREPARATION AND TESTING Turn-key accelerating systems can only be provided if the preparation and testing can be performed within the industrial responsibility. In the following chapter the recent results of cavities prepared at ACCEL for our accelerator modules are summarized. Closed loop chemical processing plants, high pressure high purity water rinsing facilities as well as the necessary clean rooms are used for the preparation of TESLA type, 500 MHz single cell cavities, and Half Wave Resonators. The results of the vertical cold rf test of the 500 MHz cavities are summarized in fig 11 and show the reliability of the achieved results. All nine cavities manufactured and tested so far show basically the same performance and allow for guaranteed accelerating voltage of about 2 MV to 2.3 MV with sufficient cavity quality factors Q 0 to allow sufficient operation in the storage rings or synchrotrons The procedures of assembling these cavities into accelerating 9

11 modules are so far safely established not to deteriorate the cavity performance compared to the vertical test results as is shown in the next paragraph 6. TESLA cavities are well developed and their performance, with the goal of gradients around 35 MV/m necessary for the Linear Collider application, show sufficient room for operation in linacs for ERL or FEL application. TESLA cavities which have been produced and chemically prepared at ACCEL are shown in fig 12 in comparison with TESLA cavities prepared at DESY. ACCEL prepared cavities using the in house infrastructure do almost reach the DESY prepared performance and these cavities fulfill safely the performance parameters of about 15 MV/m at quality factors around Summary 500 MHz Single Cell Cavity vertical cold Tests 1E+10 Cornell1 Cornell2 SRRC1 SRRC2 Figure 11: test results of ACCEL prepared 500 MHz Cavities (vertical test) Qo 1E+09 1E Vacc [MV] CLS1 CLS2 DLS1 DLS2 DLS3 1E+11 Q 0 1E+10 1E E acc [MV/m] AC55 AC56 AC57 AC59 AC60 AC61 AC62 AC63 AC64 BE1 BE2 Figure 12: Comparison of TESLA cavity test results (vertical tests): ACxx cavities are prepared and tested at DESY most of them including 1400 C heat treatment. BE01 and BE02 have been prepared at ACCEL. 800 C heating has been performed using the DESY furnace, not heat treatment at 1400 C has been performed on these two cavities 10

12 6. ASSEMBLY, DELIVERY, AND TAKING-INTO-OPERATION Module assembly includes the integration of cavities with all auxiliary components like helium vessel, tuners, power couplers, eventually HOM couplers, magnetic and cryogenic shielding, instrumentation, all integrated in the vacuum vessel. Procurement of standard components with sufficient Figure 13: Overview on the assembly of the 352 MHz LEP modules. Background: a complete module with 4 cavities before closing of the vacuum tank 3 cavities completed with the Helium vesse land tuner arr prepared and standing in front of the module quality, the preparation of cavities, integration of all components while preserving the cavity performance, intermediate testing and an overall quality control system form the basis for the successful performance of the accelerator module. In Fig. 14 a comparison 1E+10 between the vertical test results of a 500 MHz cavity with the performance Q0 1E+09 Cavity Test Modul Test after module integration is shown. Although the measurement error is larger for the module measurement due to the fact that the cavity Q can only be measured by the rf induced helium losses, a significant difference 13.3 MV/m reached during Modul Test with 2 ms long pulses 1E Eacc [MV/m] Figure 14: vertical test results (blue) in comparison with the cavity performance in the module (red) between vertical and module test can not be observed. Thus the assembly procedures can be regarded as qualified for this kind of application for the 500 MHz modules. 11

13 7. CURRENT INDUSTRIAL CAPABILITIES, CONCLUSION Industrial Capabilities in SRF technology are available at different levels. Companies focused on engineering with a view to application of SRF technology. Companies offering manufacturing resources (prototyping and series production). Companies offering design, engineering, and manufacturing. Companies offering the complete scope from design up to operational training. On the background of the recent (August 2004) announced decision for SRF technology for the International Linear Collider (ILC) the following comments can be summarized: The ILC decision for SRF has given a push also to industry and new interest in SRF technology is visible Companies with capabilities in SRF technology are located in all of the three regions: North America, Europe and Asia/Pacific. For ERL like projects the user will find sufficient support in industry from engineering capability, prototyping, up to delivery of turn key systems. 8. FUTURE PLANS Obviously industrial future plans are driven by the SRF application in future projects. Insofar the decision in favor of SRF technology for the ILC is promising for the industrial future supply of SRF technology. In addition a number of near term projects which are funded or near funding and have decided to use SRF technology can be identified. 12

14 Near term projects which are 4GLS, Peking University FEL, CORNELL-ERL, BNL- Electron Cooler, X-FEL at DESY, CEBAF-upgrade, SNS upgrade, and Synchrotron Light Sources such as SSRF (Shanghai). On the background of the above listed projects industrial support for the development of SRF applications can be summarized: Provide turn-key modules and Systems. Participate in and contribute to development issues (Cavities, Couplers, HOM dampers/absorbers ), provide prototypes, investigate reduction of manufacturing costs. Support project preparation/proposals with studies for large scale series production. Build up capacities and facilities for series production. We believe that industry is ready to support the increasing demand for SRF technology and is also ready to build up or extend further resources for future projects. However the investment in extension of resources must be financed by the budgets of the project or at least be secured by the projects. On the other hand it is obvious that from the project point of view the capabilities in industry should be ready as soon as the project start is visible. Consequently the timing for future investment is of great importance and should be mutually discussed between industry and institutions. ACKNOWLEDGEMENTS We thank our colleagues at ACCEL and at other industrial companies who have contributed to this article. The fruitful discussions with many partners in the institutes on the subject of industrialization and partnerships are appreciated. 13

15 REFERENCES [1] P. v. Stein, et al, A superconducting Landau Accelerator Module for BESSY II, proceedings of the 2001 Particle Accelerator Conference, Chicago. [2] Pekeler et al, A 40 MeV Linear Accelerator for Protons and Deuterons Using Superconducting Half Wave Resonators, proceedings rf the 2002 EPAC, Paris [3] Calaga et al, High Current Superconducting Cavities at RHIC. Proceedings of the 2004 EPAC, Luzern [4] Michael et al, Die Strahlungsquelle ELBE im Forschungszentrum Rossendorf, DACH Jahrestagung 2004, Salzburg [5] The 4 th Generation Light Source at Daresbury: [6] Podlech et al, Status of the Development of a Superconducting 352 MHz CH-Prototype Cavity, Proceedings of the 11 th SRF workshop, Lübeck, 2003 [7] Teichert et al, Status of the Rossendorf SRF-Gun Project, ww.mhf.desy.de/public/care04 [8] The Spallation Neutron Source. [9] Belomestnykh et al, Commissioning and Operations Results of the Industry-Produced CESR-Type SRF Cryomodules, proceedings of the 2005 PAC, Knoxville 14