| Paper |
Title |
Page |
| MOPP012 |
DC Breakdown Experiments for CLIC
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577 |
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- A. Descoeudres, S. Calatroni, M. Taborelli
CERN, Geneva
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For the production of the Compact Linear Collider (CLIC) RF structures, a material capable of sustaining high electric field, with a low breakdown rate and showing low damages after breakdowns is needed. A DC breakdown study is underway at CERN in order to test candidate materials and surface preparations, and also to have a better understanding of the breakdown mechanism. The saturated breakdown fields of several metals and alloys have been measured, ranging from 100MV/m for Al to 900MV/m for stainless steel, being around 150MV/m for Cu, CuZr and Glidcop, 300MV/m for W, 400MV/m for Mo, Nb and Cr, 650MV/m for V, and 750MV/m for Ti for example. Titanium shows a strong material displacement after breakdowns, while Cu, Mo and stainless steel are more stable. The conditioning speed of Mo can be significantly improved by removing oxides at the surface with a heat treatment, typically at 875°C for 2 hours. DC breakdown rate measurements have been done with Cu and Mo electrodes, showing similar results as in RF experiments: the breakdown probability seems to exponentially increase with the applied field.
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| WEPP084 |
Fabrication of a Quadrant-type Accelerator Structure for CLIC
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2716 |
| |
- T. Higo, Y. Higashi, H. Kawamata, T. T. Takatomi, K. Ueno, Y. Watanabe, K. Yokoyama
KEK, Ibaraki
- A. Grudiev, G. Riddone, M. Taborelli, W. Wuensch, R. Zennaro
CERN, Geneva
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In order to heavily damp the higher order modes of an accelerator structure for CLIC, two kind of damping mechanisms are implemented in one of the designs. Here each cell is equipped with electrically coupled damping channels in addition to the magnetically coupled waveguides. This design requires an assembly of longitudinally cut four quadrants to form a structure and the parts are necessarily made with milling. Since KEK has developed a high-precision machining of X-band accelerator cells with milling and turning at the same time, the experience was extended to the milling of this quadrant. Firstly, the fabrication test of a short quadrant was performed with multiple vendors to taste the present-day engineering level of milling. Following this, a full-size quadrant is also made. In this course, some of the key features are addressed, such as flatness of the reference mating surfaces, alignment grooves, 3D profile shape of the cells, surface roughness and edge treatment. In this paper, these issues are discussed from both fabrication and evaluation point of views.
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| MOPP081 |
Engineering Design of a PETS Tank Prototype for CTF3 Test Beam Line
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739 |
| |
- D. Carrillo, L. García-Tabarés, J. L. Gutierrez, I. Rodriguez, E. Rodríguez García, S. Sanz, F. Toral
CIEMAT, Madrid
- G. Arnau-Izquierdo, N. C. Chritin, S. Doebert, G. Riddone, I. Syratchev, M. Taborelli
CERN, Geneva
- J. Calero
CEDEX, Madrid
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In the CLIC concept, PETS (Power Extraction and Transfer Structure) role is to decelerate the drive beam and transfer RF power to the main beam. One of the CTF3 test beam line (TBL) aims is to study the decelerated beam stability and evaluate PETS performance. The PETS core is made of eight 800 mm long copper rods, with very tight tolerances for shape (± 20 micron), roughness (less than 0.4 micron) and alignment (± 0.1 mm). Indeed, they are the most challenging components of the tank. This paper reports about the methods of fabrication and control quality of these bars. A special test bench has been designed and manufactured to check the rod geometry by measuring the RF fields with an electric probe. Other parts of the PETS tank are the power extractor, the waveguides and the vacuum tank itself. Industry is partially involved in the prototype development, as the series production consists of 15 additional units, and some concepts could be even applicable to series production of CLIC modules
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| TUPC037 |
Development, Production and Testing of 4500 Beam Loss Monitors
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1134 |
| |
- E. B. Holzer, P. Chiggiato, B. Dehning, G. Ferioli, V. Grishin, J. M. Jimenez, M. Taborelli, I. Wevers
CERN, Geneva
- A. Koshelev, A. Larionov, V. Seleznev, M. Sleptsov, A. Sytin
IHEP Protvino, Protvino, Moscow Region
- D. K. Kramer
TUL, Liberec
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Beam-loss monitoring (BLM) is a key element in the LHC machine protection. 4250 nitrogen filled ionization chambers (IC) and 350 secondary emission monitors (SEM) have been manufactured at the Institute for High Energy Physics (IHEP) in Protvino, Russia, following their development at CERN. Signal speed and robustness against ageing were the main design criteria. Each monitor is permanently sealed inside a stainless-steel cylinder. The quality of the welding was a critical aspect during production. The SEMs are requested to hold a vacuum of 1·10-7 bar. Impurity levels from thermal and radiation-induced desorption should remain in the range of parts per million in the ICs. The difference in sensitivity is about 3·104. To avoid radiation aging (up to 2·108 Gy in 20 years) production of the chambers followed strict UHV requirements. IHEP designed and built the UHV production stand. Due to the required dynamic range of 1·109, the leakage current of the monitors has to stay below 1 pA. Several tests during and after production were performed at IHEP and CERN. A consistently high quality during the whole production period was achieved and the tight production schedule kept at the same time.
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