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8 results on '"Brunner, Kristóf"'

1. NbTi/Nb/Cu multilayer shield for the superconducting shield (SuShi) septum

Author

Barna, Daniel, Novak, Martin, Brunner, Kristof, Petrone, Carlo, Atanasov, Miroslav, Feuvrier, Jerome, and Pascal, Max

Subjects
Physics - Accelerator Physics
Abstract

A passive superconducting shield was proposed earlier to realize a high-field (3-4 T) septum magnet for the Future Circular Collider. This paper presents the experimental results of a potential shield material, a NbTi/Nb/Cu multilayer sheet. A cylindrical shield was constructed from two halves, each consisting of 4 layers with a total thickness of 3.2~mm, and inserted into the bore of a spare LHC dipole corrector magnet (MCBY). At 4.2~K, up to about 3.1~T at the shield's surface only a leakage field of 12.5~mT was measured inside the shield. This can be attributed to the mis-alignment of the two half cylinders, as confirmed by finite element simulations. With a better configuration we estimate the shield's attenuation to be better than $\mathbf{4\times 10^{-5}}$, acceptable for the intended application. Above 3.1~T the field penetrated smoothly. Below that limit no flux jumps were observed even at the highest achievable ramp rate of more than 50~mT/s at the shield's surface. A 'degaussing' cycle was used to eliminate the effects of the field trapped in the thick wall of the shield, which could otherwise distort the homogeneous field pattern at the extracted beam's position. At 1.9~K the shield's performance was superior to that at 4.2~K, but it suffered from flux jumps.

Published
2018
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2. Shielded Pair Method for Beam Screen Surface Resistance Measurement at Cryogenic Temperature.

Author

Brunner, Kristóf, Krkotić, Patrick, Calatroni, Sergio, and Barna, Dániel

Subjects
LARGE Hadron Collider, SURFACE resistance, AMORPHOUS carbon, SURFACE structure, MAGNETIC fields
Abstract

The shielded pair resonator method is a useful tool in the measurement of accelerator components, such as the beam screens used in the Large Hadron Collider (LHC), the High-Luminosity (HL) LHC, or future accelerators. It can measure the resistive losses at several frequency points by separating the resistive losses on the sample from other sources of losses. We built a new resonator to be inserted into a superconducting dipole magnet (peak magnetic field of 9.5 T) and to measure the surface resistance of beam screens, such as LHC beam screens coated with amorphous carbon (a-C). The device can measure surface resistance at any temperature between 4.2 K and 300 K, in the frequency range of 400 MHz to 1600 MHz. We conducted the first surface resistance measurements of two a-C coated beam screens at 4.2 K and showed that the 200 nm to 400 nm titanium underlayer plus 50 nm a-C only has a limited effect on the surface resistance. This first result supports the choice of this coating as baseline for the HL-LHC triplets magnets upgrade. The resonator will have an important role in the characterization of next-generation beam screens, such as a beam screen with laser-engineered surface structure (LESS). Further measurements of the LHC beam screen in the presence of magnetic fields up to 9.5 T and throughout the full temperature range are going to be reported separately. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Dielectric resonator to measure surface resistance of accelerator components at room temperature and 77 K

Author

Universitat Politècnica de Catalunya. Departament de Teoria del Senyal i Comunicacions, Universitat Politècnica de Catalunya. CommSensLab-UPC - Centre Específic de Recerca en Comunicació i Detecció UPC, Brunner, Kristóf, Krkotic, Patrick, Costa Pinto, Pedro, Gibbons Díaz-Rato, Eduardo, Pfeiffer, Stephan, Vollenberg, Wilhelmus, Calatroni, Sergio, Barna, Dániel, Pont Montaner, Montserrat, O'Callaghan Castellà, Juan Manuel, Universitat Politècnica de Catalunya. Departament de Teoria del Senyal i Comunicacions, Universitat Politècnica de Catalunya. CommSensLab-UPC - Centre Específic de Recerca en Comunicació i Detecció UPC, Brunner, Kristóf, Krkotic, Patrick, Costa Pinto, Pedro, Gibbons Díaz-Rato, Eduardo, Pfeiffer, Stephan, Vollenberg, Wilhelmus, Calatroni, Sergio, Barna, Dániel, Pont Montaner, Montserrat, and O'Callaghan Castellà, Juan Manuel

Abstract

We measured the surface resistance of titanium, amorphous carbon, and nonevaporable getter (NEG) coatings on copper samples, representative of surface treatments of beam-facing components in the High-Luminosity Large Hadron Collider at CERN. Measurements were done at room temperature as well as at liquid nitrogen temperature (77 K) by means of a novel large dielectric resonator operating at 3.4 GHz. The impact of a 100 to 400 nm titanium layer or a 50-nm amorphous carbon layer was negligible both at room temperature and down to 77 K in comparison to copper, while a thick (1140 nm) NEG layer showed a measurable increase in the surface resistance, being more significant at low temperature. The dielectric resonator proved to be a useful tool to characterize the surface resistance of flat samples with different surface treatments and sizes up to 10 cm for accelerator applications. Furthermore, its construction and operation are much simpler compared to other test devices currently in use, and it can provide accurate experimental data for the evaluation of the beam coupling impedance., Peer Reviewed, Postprint (published version)

Published
2023

5. Shielded Pair Method for Cylindrical Surface Resistance Measurement at Cryogenic Temperature

Author

Brunner, Kristóf, Barna, Daniel, Calatroni, Sergio, and Caspers, Fritz

Subjects
MC7: Accelerator Technology, Physics::Accelerator Physics, Accelerators and Storage Rings, Accelerator Physics
Abstract

The shielded pair resonator method was already used in the past at CERN to measure the surface resistivity of the LHC beam screen both at room temperature and cryogenic temperature. We have refined and adapted the measurement to be able to measure other types of beam screens and also to operate in a strong dipolar magnetic field. This is necessary for testing the properties of HTS coated beam screens or the possible effects of coatings and surface treatments for e-cloud suppression. Several calibration runs were done at cryogenic temperatures (4.2 K) measuring the surface resistivity of a copper pipe to identify the precision, stability and reproducibility achievable using this method. This work describes the challenges of the measurement and ways to mitigate them., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Published
2021
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6. SPS slow extraction losses and activation: update on recent improvements

Author

Fraser, Matthew, Balhan, Bruno, Barna, Daniel, Bartosik, Hannes, Bernhard, Johannes, Bertone, Caterina, Björkman, Daniel, Borburgh, Jan, Brugger, Markus, Brunner, Kristóf, Charitonidis, Nikolaos, Conan, Nadine, Cornelis, Karel, Dutheil, Yann, Esposito, Luigi Salvatore, Garcia Alia, Ruben, Gatignon, Laurent, Genton, Charles-Mathieu, Goddard, Brennan, Heßler, Christoph, Kadi, Yacine, Kain, Verena, Mereghetti, Alessio, Pari, Michelangelo, Patecki, Marcin, Prieto, Javier, Redaelli, Stefano, Roncarolo, Federico, Rossi, Roberto, Scandale, Walter, Solieri, Nicola, Spanggaard, Jens, Stein, Oliver, Stoel, Linda, Velotti, Francesco, and Vincke, Helmut

Subjects
MC4: Hadron Accelerators, Accelerators and Storage Rings, Accelerator Physics
Abstract

Annual high intensity requests of over 10¹⁹ protons on target (POT) from the CERN Super Proton Synchrotron (SPS) Fixed Target (FT) physics program continue, with the prospect of requests for even higher, unprecedented levels in the coming decade. A concerted and multifaceted R effort has been launched to understand and reduce the slow extraction induced radioactivation of the SPS and to anticipate future experimental proposals, such as SHiP* at the SPS Beam Dump Facility (BDF)**, which will request an additional 4·10¹⁹ POT per year. In this contribution, we report on operational improvements and recent advances that have been made to significantly reduce the slow extraction losses, by up to a factor of 3, with the deployment of new extraction concepts, including passive and active (thin, bent crystal) diffusers and extraction on the third-integer resonance with octupoles. In light of the successful tests of the prototype extraction loss reduction schemes, an outlook and implications for future SPS FT operation will be presented., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Published
2019

7. Use of a Massless Septum to Increase Slow-Extraction Efficiency

Author

Brunner, Kristóf, Barna, Daniel, Fraser, Matthew, Goddard, Brennan, Stoel, Linda, and Wiesner, Christoph

Subjects
Physics::Accelerator Physics, T12 Beam Injection/Extraction and Transport, 04 Hadron Accelerators, Nuclear Experiment, Accelerators and Storage Rings, Accelerator Physics
Abstract

The Super Proton Synchrotron (SPS) at CERN provides slow-extracted beam for Fixed Target experiments in the North Area. For the higher extracted beam intensities requested by future experimental proposals, beam-loss induced activation will be one of the limiting factors for the availability of such a facility. In this paper, we present and discuss the concept of using a massless septum magnet to increase the extraction efficiency and decrease losses caused by protons scattering on the electrostatic-septa wires., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Published
2018

8. Conceptual design of a high-field septum magnet using a superconducting shield and a canted-cosine-theta magnet

Author

Barna, Dániel, primary, Novák, Martin, additional, Brunner, Kristóf, additional, Kirby, Glyn, additional, Goddard, Brennan, additional, Borburgh, Jan, additional, Atanasov, Miroslav Georgiev, additional, Sanz Ull, Alejandro, additional, Renner, Elisabeth, additional, Bartmann, Wolfgang, additional, and Szakály, Marcell, additional

Published
2019
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