Author: Bellodi, G.
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TUPOPA06 Microscopy Investigation on Different Materials After Pulsed High Field Conditioning and Low Energy H-Irradiation 422
SUPCJO06   use link to see paper's listing under its alternate paper code  
 
  • C.F. Da Palma Serafim, G. Bellodi, S. Calatroni, A. Grudiev, A.M. Lombardi, R.C. Peacock, A.T. Perez Fontenla, S. Ramberger, E. Sargsyan, S. Sgobba, W. Wuensch
    CERN, Meyrin, Switzerland
  • F. Djurabekova
    HIP, University of Helsinki, Finland
 
  During operation the LINAC4 RFQ (Radio-Frequency-Quadrupole) is exposed to high electric fields which can lead to vacuum breakdown. It is also subject to beam loss that can cause surface modification, including blistering, which can result in reduced electric field handling and an increased breakdown rate. An experimental study has been made to identify materials with high electric field capability and robustness to low-energy irradiation. In this paper we briefly discuss the selection criteria and we analyze these materials investigating their metallurgical properties using advanced microscopic techniques such as Scanning Electron Microscope, Electron Back Scattered Diffraction, Energy-dispersive X-ray Spectroscopy and conventional optical microscopy. These allow to observe and characterize the different materials on aμand a nano-scale, allowing us to compare results before and after irradiation and breakdown testing.  
poster icon Poster TUPOPA06 [2.771 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TUPOPA06  
About • Received ※ 14 August 2022 — Revised ※ 23 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 31 August 2022
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TUPOPA10 Beam Dynamics and RF Design Studies for the New RFQ for CERN Linac4 Upgrade 430
 
  • H.W. Pommerenke, G. Bellodi, A. Grudiev, S. Kumar, A.M. Lombardi
    CERN, Meyrin, Switzerland
 
  The 352 MHz Linac4-RFQ is the first rf accelerating structure of the CERN accelerator complex, accelerating an H beam to 3 MeV. After successful commissioning in 2013, superficial vane damage has been observed in 2020. In view that the RFQ is a single point of failure, in parallel to the production of a near identical spare (RFQ2), design studies on a longer-term upgrade have been launched: Linac4-RFQ3. Main goals are to achieve a design with higher beam acceptance, reduced beam losses, and reduced RF breakdown rate. Two versions of RFQ are under study: a conventional RFQ built by brazing copper, as well as an RFQ with titanium vane tips (brazed on copper). High-gradient experiments suggest that titanium vane tips support higher surface fields compared to copper, up to 40 MV/m, and are more resistant against beam irradiation. In this paper, we present beam dynamics and rfdesign of both variants of RFQ3.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TUPOPA10  
About • Received ※ 12 August 2022 — Revised ※ 19 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 02 September 2022
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TUPOPA13 Pulsed DC High Field Measurements of Irradiated and Non-Irradiated Electrodes of Different Materials 441
SUPCJO07   use link to see paper's listing under its alternate paper code  
 
  • R.C. Peacock, G. Burt
    Lancaster University, Lancaster, United Kingdom
  • G. Bellodi, S. Calatroni, C.F. Da Palma Serafim, A. Grudiev, A.M. Lombardi, A.T. Perez Fontenla, S. Ramberger, E. Sargsyan, S. Sgobba, W. Wuensch
    CERN, Meyrin, Switzerland
 
  Beam loss occurs in Radio Frequency Quadrupoles (RFQ), and has been observed in the H linear accelerator Linac4 (L4) at CERN. To determine if beam loss can induce breakdowns, and to compare the robustness of different materials, tests have been done using pulsed high-voltage DC systems. Electrical breakdown phenomena and conditioning processes have been studied using these systems. Cathodes of different materials were irradiated with 1.2x1019 H p/cm2, the estimated beam loss of the L4 RFQ over 10 days. The irradiated electrodes were installed in a system to observe if the irradiated area coincided with the breakdown locations, with pulsing parameters similar to the RFQ. Tests of irradiated and non-irradiated electrodes of the same material were done for comparison. The main difference observed was an increase in the number of breakdowns during the initial conditioning that returned to non-irradiated sample values with further running. Visual observations after irradiation show the beam centre and a halo the same diameter of the beam pipe. Breakdown clusters occur in the centre and halo regions, suggesting irradiation is not the only factor determining the breakdown probability.  
poster icon Poster TUPOPA13 [3.845 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TUPOPA13  
About • Received ※ 23 August 2022 — Revised ※ 29 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 07 September 2022
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