J.C. Wolff, A. Gössel, C. Müller, D. Reschke, L. Steder, D. Tischhauser
DESY, Hamburg, Germany
W. Hillert, J.C. Wolff
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
Funding:This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. Magnetic flux trapped in the Niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity of the cavity to trapped magnetic flux is mainly determined by the treatment, the geometry and the Niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a so-called B-mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities is currently under development at DESY. Contrary to former approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution the design, the development process as well as first performance test results of the B-mapping system are presented.
N. Sakamoto, H. Imao, O. Kamigaito, T. Nagatomo, T. Nishi, K. Ozeki, K. Suda, A. Uchiyama, K. Yamada
RIKEN Nishina Center, Wako, Japan
After commissioning of the RIKEN superconducting linac (SRILAC) in the end of FY2019, heavy ion beams were provided to the nuclear physics experiments. In this paper operation history and evolution of field emission levels through the year will be presented.
Y. Yamamoto, M. Akemoto, D.A. Arakawa, A. Araki, S. Araki, A. Aryshev, T. Dohmae, M. Egi, M.K. Fukuda, K. Hara, H. Hayano, Y. Honda, T. Honma, H. Ito, E. Kako, H. Katagiri, R. Katayama, M. Kawamura, N. Kimura, Y. Kojima, Y. Kondou, T. Konomi, M. Masuzawa, T. Matsumoto, S. Michizono, Y. Morikawa, H. Nakai, H. Nakajima, K. Nakanishi, M. Omet, T. Oyama, T. Saeki, H. Sakai, H. Shimizu, S.I. Takahara, R. Ueki, K. Umemori, A. Yamamoto
KEK, Ibaraki, Japan
Hiroshima University, Higashi-Hiroshima, Japan
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
HU/AdSM, Higashi-Hiroshima, Japan
The University of Tokyo, The School of Engineering, Tokyo, Japan
CERN, Meyrin, Switzerland
In STF at KEK, as the operational demonstration of the SRF accelerator for ILC, the STF-2 cryomodules (CM1+CM2a: one and half size CM with 12 cavities) have achieved 33 MV/m as average accelerating gradient with 7 cavities in Mar/2019. After that, one cavity with the lowest performance installed in CM2a was replaced with one N-infused cavity developed for High-Q/High-G R&D between Japan and US. From this April, the beam operation started again and those CMs achieved 33 MV/m as average accelerating gradient with 9 cavities including one N-infused cavity again. This is the very important milestone for ILC. In this report, the detailed results will be presented.
W. Ma, Y.B. Sun, N. Yuan
Sun Yat-sen University, Zhuhai, Guangdong, People’s Republic of China
SSRF, Shanghai, People’s Republic of China
L. Lu, L. Yang, Z.L. Zhang
IMP/CAS, Lanzhou, People’s Republic of China
Shenzhen industrial synchrotron radiation source is a 3 GeV synchrotron radiation diffraction-limited source. It consists of three parts, linear accelerator, booster, and storage ring. As a basic part of the storage ring, the superconducting radio frequency system provides energy for the beam to supplement the beam power loss caused by synchrotron radiation and higher-order modes, and provide the longitudinal bunch for the electron beam. The superconducting radio frequency cavity of the storage ring consists of two 500 MHz single-cell cavities and a third harmonic 1500 MHz double-cell cavity. This paper will introduce the superconducting cavity, radio frequency amplifier, and low-level radio frequency system in the Shenzhen industrial synchrotron radiation source facility.
H. Jenhani, S. Arsenyev
CEA-IRFU, Gif-sur-Yvette, France
S. Kazakov, N. Solyak
Fermilab, Batavia, Illinois, USA
The Proton Improvement Plan - II (PIP-II) project is underway at Fermilab with an international collaboration involving CEA in the development and testing of 650 MHz cryomodules. One of the first main contributions of the CEA was the participation in the design efforts for the current 50 KW CW 650 MHz power couplers. This paper reports some of the results of thermal and paramet-ric studies carried out by the CEA on these power couplers
H.-W. Glock, J. Knobloch, A. Neumann, A. Veléz
HZB, Berlin, Germany
Industrial X-ray tomography offers the possibility to capture the entire inner and outer shape of an SRF cavity, providing also insights in weld quality and material defects. As a non-contact method this is especially attractive to investigate shape properties of fully processed and closed cavities. A drawback is the inherently strong X-ray damping of niobium, which causes the demand for intense hard X-rays, typically beyond the capabilities of dc-X-ray-tubes. This also limits the accuracy of material borders found by the tomographic inversion. To illustrate both capabilities and limitations, results of X-ray tomography investigations using three different cavities are reported, also describing the fundamental parameters and the hard- and software demands of the technology. We also discuss the non-trivial transferring of tomography data into RF simulation tools.
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K. Turaj, O. Brunner, A.C. Butterworth, F. Gerigk, P. Maesen, E. Montesinos, F. Peauger, M. Therasse, W. Venturini Delsolaro
CERN, Meyrin, Switzerland
The LHC RF cryomodule "Asia" suffered an accidental influx of about 0.5 l of tunnel air during the leak checks of the pumping manifolds. The resulting risk of particle contamination was difficult to assess, and could not be excluded with certainty. If one or more cavities were contaminated, a severe impact on beam operations in the LHC machine was to be expected. In order to minimize the risks, the Asia cryomodule has been replaced with a spare unit. Subsequently, the cryomodule was tested in the SM18 test facility without intermediate venting, and showed high levels of radiation due to field emission above 1.8 MV in one of the cavities. The other cavities were less strongly affected, but clear signs of contamination were observed. The helium processing technique was used to improve the performance of the SRF cavity with respect to field emission. This paper will discuss the results of the above-mentioned test.
Paper is devoted to analysis of the influence of irradiation arising in SRF accelerators on critical current phenomena of HTc multilayered superconductors. Impact of size and concentration of created then nano-defects on current-voltage characteristics and critical current of HTc superconductors as function of the magnetic field and temperature will be investigated. It will be studied basing on analysis of interaction of the magnetic pancake vortices with arising during irradiation defects, for various strengths of capturing. The comparison of the model with experimental data will be given too. The dynamic losses dependent on critical current, generated in the superconducting current leads for varying current, will be considered. Analysis of the dynamic magnetic induction distribution inside superconducting lead for time varying current in the cycle will be given and Joule losses estimated. As the result it has been established the hysteresis behavior of the losses in current leads. The changes of losses have been observed for first and following current increase, which effect should have meaning during multiply charging of the superconducting electromagnets.