DC testing and phase resolved partial discharge measurements of the new trigger transformers for the LHC beam dump kickers

During LS2, the LHC beam dump kicker pulse generators will be subject to a substantial consolidation program. One major part is the replacement of the existing GTO stack trigger transformer by a new more performant one. The transformer is assembled, moulded, and tested in-house. Part of the validation procedure are standard DC tests and subsequent discharge monitoring as well as newly introduced phase resolved partial discharge measurements. This paper briefly highlights the trigger transformer parameters and construction and outlines in detail the testing and partial discharge measurements. It concludes with a comparison and analysis of the results of the different measurement techniques

Eradication of Mercury Ignitron from the 400 kA Magnetic Horn Pulse Generator for CERN Antiproton Decelerator

The CERN Antiproton Decelerator (AD) produces low-energy antiprotons for studies of antimatter. A 26 GeV proton beam impacts the AD production target which produces secondary particles including antiprotons. A magnetic Horn (AD-Horn) in the AD target area is used to focus the diverging antiproton beam and increase the antiproton yield enormously. The horn is pulsed with a current of 400 kA, generated by capacitor discharge type generators equipped with ignitrons. These mercury-filled devices present a serious danger of environmental pollution in case of accident and safety constraints. An alternative has been developed using solid-state switches and diodes. Similar technology was already implemented at CERN for ignitron eradication in the SPS Horizontal beam dump in the early 2000s. A project was launched to design and set up a full-scale test-bench, to install and test a dedicated solid-state solution. Following the positive results obtained from the test-bench, the replacement of ignitrons by solid-state devices in the operational AD-Horn facility is currently under preparation. This paper describes the test-bench design and results obtained for this very high current pulser

Considerations on an Upgrade Possibility of the LHC Beam Dump Kicker System

The LHC Beam Dump System (LBDS) is designed to safely dispose the circulating beams over a wide range of energy from 450 GeV up to 7 TeV, where the maximum stored energy is 362 MJ per beam. One of the most critical components of the LBDS are the extraction kickers that must reliably switch on within the 3 us particle-free abort gap. To ensure this functionality, even in the event of a power-cut, the power generator capacitors remain charged and hence the Gate Turn-Off (GTO) switch stack has to hold the full voltage throughout beam operation. The increase of the LHC collision energy to 13 TeV has increased the voltage levels at the GTO stacks and during re-commissioning an increased rate of high-voltage (HV) related issues at the level of the GTO stack was observed. Different solutions have been analysed and an improved GTO stack will be implemented. This paper also outlines the benefit of adding more kicker magnets to improve the voltage hold off issues and to improve the tolerance to missing kickers during extraction

SPS Beam Dump System (SBDS) Commissioning After Relocation and Upgrade

In order to overcome several machine limitations, the SBDS has been relocated from LSS1 (Long Straight Section 1) to LSS5 during LS2 (Long Shutdown 2) with an important upgrade of the extraction kicker installation. An additional vertical deflection kicker magnet (MKDV) was produced and installed while the high voltage (HV) pulse generators have been upgraded by changing gas-discharge switches (thyratrons and ignitrons) to semiconductor stacks operating in oil. Furthermore the horizontal sweep generators have been upgraded to allow for a lower kick strengths. The controls, previously consolidated during LS1, went through an additional light consolidation phase with among others the upgrade of the trigger & retrigger distribution system and the installation of a new fast-interlocks detection system. This paper describes the commissioning without and with beam and elaborates on the measured improvements and encountered problems with corrective mitigations

Studies for Mitigating Flashover of CERN-LHC Dilution Kicker Magnets

The LHC beam dump system is used for extracting beam from the LHC and, as such, is a safety critical system whose proper functionality must be assured. Dilution kicker magnets (MKBs) sweep the extracted beam over the cross-sectional area of a dump block as the energy density would otherwise be too high and damage the block. In 2018, a high voltage flashover occurred in a vertical MKB (MKBV) vacuum tank, during a beam dump, which resulted in non-ideal sweep of the beam over the block. The location of the flashover could not be identified during a subsequent inspection of the magnet. Hence, electrical field simulations have been carried out to identify potentially critical regions, to determine the most probable region of the flashover. One potentially critical region is a rectangular beam pipe (RBP) between the end of the tank and the MKBV magnet, whose purpose is to reduce plasma propagation to the adjacent tank in the event of a flashover. Mitigating measures were studied and are reported in this paper

Feasibility Study of the Fast SPS Ion Injection Kicker System

As part of the upgrade project for ions the rise time of the injection kicker system into the SPS needs to be improved. The changes being studied include the addition of a fast Pulse Forming Line parallel to the existing Pulse Forming Network for the fast kicker magnets MKP-S. With the PFL an improved magnetic field rise time of 100 ns is targeted. Two different configuration utilizing a 2nd thyratron or two fast diode stacks have been outlined in the past. This paper presents the recent progress on the analogue circuit simulations for both options as well as measurements carried out on a test system. Modelling, optimization and simulation of the entire system with diodes and a second configuration with two thyratron switches are outlined. Measurement results are given and the feasibility of the upgrade is discussed

Considerations for the Injection and Extraction Kicker Systems of a 100 TeV Centre-of-Mass FCC-hh Collider

A 100 TeV center-of-mass energy frontier proton collider in a new tunnel of ~100 km circumference is a central part of CERN's Future Circular Colliders (FCC) design study. One of the major challenges for such a machine will be the beam injection and extraction. This paper outlines the recent developments on the injection and extraction kicker system concepts. For injection the system requirements and progress on a new inductive adder design will be presented together with first considerations on the injection kicker magnets. The extraction kicker system comprises the extraction kickers itself as well as the beam dilution kickers, both of which will be part of the FCC beam dump system and will have to reliably abort proton beams with stored energies in the range of 8 Gigajoule. First concepts for the beam dump kicker magnet and generator as well as for the dilution kicker system are described and its feasibility for an abort gap in the 1 μs range is discussed. The potential implications on the overall machine and other key subsystems are outlined, including requirements on (and from) dilution patterns, interlocking, beam intercepting devices and insertion design

Consolidation of Re-Triggering System of LHC Beam Dumping System at CERN

The Trigger Synchronization and Distribution System (TSDS) is a core part of the LHC Beam Dump System (LBDS). It comprises redundant Re-Trigger Lines (RTLs) that allow fast re-triggering of all high-voltage pulsed generators in case one self-triggers, resulting in a so-called asynchronous dump. For reliability reasons, the TSDS relies on many RTL redundant trigger sources that do not participate directly to the execution of a normal dump. After every dump, signals propagating on the RTLs are analyzed by Post Operation Check (POC) systems, to validate the correct performance and synchronization of all redundant triggers. The LBDS operated reliably since the start-up of LHC in 2008, but during the Run 2 of the LHC, new failure modes were identified that could incur damage for the beam dump block. In order to correct these failure modes, an upgrade of the TSDS is realized during the LS2. This paper reviews the experience gained with the LBDS during Run 2 of the LHC operation and describes the new architecture of the TSDS being implemented. Measurements and simulations of signals propagating on the RTL are presented, and the analysis performed by the POC systems are explained

Changes to the LHC Beam Dumping System for LHC Run 2

The LHC beam dumping system performed according to expectations during Run 1 of the LHC (2009 – 2013). A brief overview of the experience is given, including a summary of the observed performance by comparison to expectations. An important number of changes are applied to the beam dumping system during the present Long Shutdown in order to further improve its safety and performance. They include the addition of a direct link between the Beam Interlock System and the re-triggering system of the dump kickers, the modification of the uninterrupted electrical power distribution architecture, the upgrade of the HV generators, the consolidation of the trigger synchronisation system, the modifications to the triggering system of the power switches and the changes to the dump absorbers TCDQ

Injection and Dump Systems for a 13.5 TeV Hadron Synchrotron HE-LHC

One option for a future circular collider at CERN is to build a 13.5 TeV hadron synchrotron, or High Energy LHC (HE-LHC) in the LHC tunnel. Injection and dump systems will have to be upgraded to cope with the higher beam rigidity and increased damage potential of the beam. The required modifications of the beam transfer hardware are highlighted in view of technology advancements in the field of kicker switch technology. An optimised straight section optics is shown