arXiv subjects

E. Sargsyan

Publications and source records attributed to E. Sargsyan.

5 recordsLinked to original sources

arXiv2025

Effects of H$^-$ low beam irradiation and high field pulsing tests in different metals

This work studies the suitability of a set of different materials for manufacturing of more efficient and durable Radio-Frequency Quadrupole (RFQ) structures compared to that currently used in many linear particle accelerators, traditionally made out of copper. RFQs are susceptible to vacuum breakdowns caused by the exposure to high electric fields, resulting in surface degradation. Additionally, a further limitation of present-day copper RFQs is surface blistering under hydrogen ion beam exposure, due to beam halo losses. Irradiation is associated with a further reduction of the breakdown field strength of the metal surface thereby affecting the overall efficiency of the RFQ. The investigated materials, Cu-OFE, CuCr1Zr, CuBe2, Ti6Al4V, SS316LN, Nb and Ta, were submitted to low-energy (45 keV) H$^-$ irradiation and tested in a direct-current (DC) system with pulsed high voltage. For comparison, the maximum surface electric field was measured for both irradiated and pristine (non irradiated) surfaces of the same material. The effects of irradiation on the surface of the materials, before and after being submitted to high electric fields, were studied with the help of microscopic imaging and chemical analysis. Blistering caused by H$^-$ irradiation has been observed in all copper and copper alloy materials. Despite reductions in breakdown field strength post-irradiation, no indications were found that the blisters on the surface have a direct cause in triggering breakdowns during high electric field tests. SS316LN, Ti6Al4V, CuBe2 and CuCr1Zr showed maximum surface electric fields higher than copper, making these promising candidate materials for future RFQs manufacturing. This paper focuses on the results with CuCr1Zr, CuBe2, SS316LN and Ta, complementing and expanding previous work exploring Cu-OFE, Nb and Ti6Al4V.

physics.acc-ph↗

arXiv2024

Investigation on different materials after pulsed high field conditioning and low-energy H- irradiation

During operation, the radio-frequency quadrupole (RFQ) of the LINAC4 at CERN is exposed to high electric fields, which can lead to vacuum breakdown. It is also subject to beam loss, which can cause surface modification, including blistering, which can result in reduced electric field holding and an increased breakdown rate. First, experiments to study the high-voltage conditioning process and electrical breakdown statistics have been conducted using pulsed high voltage DC systems in order to identify materials with high electric field handling capability and robustness to low-energy irradiation. In this paper, we discuss the results obtained for the different materials tested. To complement these, an investigation of their metallurgical properties using advanced microscopic techniques was done to observe and characterize the different materials and to compare results before and after irradiation and breakdown testing.

physics.acc-ph↗

arXiv2006

Error study of CERN Linac 4

LINAC 4 is a normal conducting H- structure proposed to intensify the proton flux currently available for the CERN accelerator chain. This linac is designed to accelerate a 65 mA beam up to 160 MeV to be injected into the CERN Proton Synchrotron Booster. The acceleration is performed up to 3 MeV by a Radio-Frequency Quadrupole resonating at 352 MHz followed by a serie of two drift tube systems (conventional Alvarez and Cell Coupled Drift Tube Linac) boosting the beam up to 90 MeV at 352 MHz and finished by a Side Coupled Linac at 704 MHz. Beam dynamics was studied and optimized performing end-to-end simulations. Robustness of this design was verified by modelling machine errors. This paper presents the results of this error study.

physics.acc-ph↗

arXiv2006

Statistical simulations of machine errors for LINAC4

LINAC 4 is a normal conducting H- linac proposed at CERN to provide a higher proton flux to the CERN accelerator chain. It should replace the existing LINAC 2 as injector to the Proton Synchrotron Booster and can also operate in the future as the front end of the SPL, a 3.5 GeV Superconductingg Proton Linac. LINAC 4 consists of a Radio-Frequency Quadrupole, a chopper line, a Drift Tube Linac (DTL) and a Cell Coupled DTL all operating at 352 MHz and finally a Side Coupled Linac at 704 MHz. Beam dynamics was studied and optimized performing end-to-end simulations. This paper presents statistical simulations of machine errors which were performed in order to validate the proposed design.

physics.acc-ph↗

arXiv2001

Variable-Phase Asynchronous Cyclotron

The conceptual design of a Variable-Phase Asynchronous Cyclotron (VPAC) is describe, which provides longitudinal bunch compression of accelerated proton or ion beams, and thus, permits high current acceleration at higher accelerator efficiency, where the possible beam losses are minimized and the accelerator's mechanical tolerances are relaxed. Beam control is assured by the ability to independently set and vary the acceleration phase and rf voltage amplitude, the inter-cavity harmonic number and the transverse focusing strength, which considerably overcome the space charge effects in each sector and turn of the proposed cyclotron. The new accelerator concept is especially suitable to accelerate intense proton beams up to 800 MeV in energy and average beam current in the 100-mA class. All accelerator elements are based on currently available and feasible technologies. To demonstrate feasibility of design, the detailed calculations and modeling of a 10-turn VPAC prototype for the production of 25.6 MeV, 100 mA proton beam are presented and the key features of the new accelerator concept are discussed.

physics.acc-ph↗