Control of the MKQA tuning and aperture kickers of the LHC

The large hadron collider (LHC) at CERN has been equipped with four fast pulsed kicker magnets in RA43 situated at point 4 which are part of the measurement system for the tune and the dynamic aperture of the LHC beam (Beam 1 and Beam 2). For the tune measurement 'Q', the magnets will excite oscillations in part of the beam. This is achieved by means of a generator producing a 5 µs base half-sine pulse of 1.2 kA [1] amplitude, superimposed with a 3rd harmonic to produce a 2 µs flat top. A kick repetition rate of 2 Hz will be possible. To measure the dynamic aperture 'A' of the LHC at different beam energies, the same magnets will also be driven by a more powerful generator which produces a 43 µs base half-sine current pulse of 3.8 kA. For the 'A' mode a thyristor is used as switching element inside the generator. A final third mode named 'AC dipole' will rely on the beam being excited coherently at a frequency close but outside its Eigen-frequencies by an oscillating dipole field. The beam is expected to oscillate at the exciter frequency of 3 kHz with a phase shift of π/2. The 'AC dipole' will use two 18 kW audio amplifiers capable of driving the magnets at 1 kHz(rms) around 3 kHz or between 2.7 kHz and 4 kHz. The complete system uses supervisory control implemented with Siemens PLC technology with added Siemens PROFIsafe safety feature to treat the various interlocks that have been introduced in the circuits and to assu re a safe functioning and provide 'LOCAL' and 'REMOTE' control (via CCC) of the complete installation

Sub-Nanosecond Switching of HV SiC MOS Transistors for Impact Ionisation Triggering

Pulse generators with multi kV/kA pulses are necessary for the particle accelerator environment for beam transfer magnets. Traditionally these generators are using thyratrons - until recently the only switches capable of switching such pulses within tens of ns. There is a strong demand to replace thyratrons with semiconductor switches to avoid their future obsolescence. Very promising candidates are components from the family of fast ionization dynistors triggered by impact ionization. Their sub-nanosecond switching time and extreme current densities can provide performances superior to that of thyratrons. Recent investigations showed that impact ionization triggering is feasible also in cheap industrial thyristors. The main issue is the generation of triggering pulses with slew rates in the multi kV/ns region and with the required output current for charging the parasitic capacitance of the thyristor. We present an approach of generating > 1 kV/ns pulses by ultra-boosted gate driving of HV SiC MOS transistors. We found that the MOS lifetime under these extreme triggering conditions can still reach more than 10⁸ pulses, enough for kicker generator applications

Ultra-Fast Generator for Impact Ionization Triggering

Impact ionization triggering can be successfully applied to standard thyristors, thus boosting their dI/dt capability by up to 1000x. This groundbreaking triggering requires applying significant overvoltage on the anode-cathode of thyristor with a slew rate > 1kV/ns. Compact pulse generators based on commercial off-the-shelf (COTS) components would allow the spread of this technology into numerous applications, including fast kicker generators for particle accelerators. In our approach, the beginning of the triggering chain is a HV SiC MOS with an ultra-fast super-boosting gate driver. The super boosting of a 1.7kV rated SiC MOS allows to reduce the MOS rise time by a factor of > 25 (datasheet tr = §I{20}{ns} vs. measured tr 1kV/ns and an amplitude > 1kV. Additional boosting is obtained by a Marx generator with GaAs diodes, reaching an output voltage slew rate > 11kV/ns. The final stage will be a Marx generator with medium size thyristors triggered in impact ionization mode with sufficient voltage and current rating necessary for the triggering of a big thyristor. This paper presents the impact ionization triggering of a small size thyristor

Injection and dump considerations for a 16.5 TeV HE-LHC

Injection and beam dumping is considered for a 16.5 TeV hadron accelerator in the current LHC tunnel, with an injection energy in the range 1 - 1.3 TeV. The present systems are described and the possible upgrade scenarios investigated for higher beam rigidity. In addition to the required equipment performance, the machine protection related aspects are explored. The expected constraints on the machine layout are also given. The technological challenges for the different equipment subsystems are detailed, and areas where R&D is necessary are highlighted.Comment: 6 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 2010; CERN Yellow Report CERN-2011-003, pp. 128-13

Measurement and analysis of SPS kicker magnet heating and outgassing with Different Bunch Spacing

Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, over several hours, even above the Curie temperature of the ferrite. At present the nominal bunch spacing in the SPS is 25 ns, however for an early stage of LHC operation it is preferable to have 50 ns bunch spacing. Machine Development (MD) studies have been carried out with an inter-bunch spacing of 25 ns, 50 ns or 75 ns. For some of the SPS kicker magnets the 75 ns bunch spacing resulted in considerable beam induced heating. In addition the MDs showed that 50 ns bunch spacing could result in a very rapid pressure rise in the kicker magnet and thus cause an interlock. This paper discusses the MD observations of the SPS kickers and analyses the available data to provide explanations for the phenomena: possible remedies are also discussed

Fast high-power thyristors triggered in impact-ionization wave mode

GTO-like thyristors 5STH-2045H0002 (4.5 kV, 18 kA/µs) developed by ABB semiconductors are currently used at CERN in LHC Beam Dumping System (LBDS): high-power switches with high dI/dt capability and low turn-on delay time are required. Implementation of the impact-ionization triggering in GTO-like thyristor enhances its switching performance and gives new information about semiconductor physics. In this work thyristors of 5STH-2045H0002 type triggered in impact-ionization wave mode are investigated. A semiconductor opening switch (SOS) generator providing a dV/dt of several kV/ns was used as a source of triggering pulses. A thyristor switching time of approximately 200-300 ps was observed. Maximum discharge parameters were obtained for two series connected thyristors at a charging voltage of 10 kV, and a capacitor stored energy of 300 J: peak current of 43 kA, dI/dt of 120 kA/µs (limited by the discharge circuit), Full Width at Half Maximum (FWHM) of 1.5 µs. A single thyristor was tested in the repetitive mode at the charging voltage of 4.2 kV, and the stored energy of 18 J: peak current of 5.5 kA, dI/dt of 40 kA/µs, FWHM of 1.5 µs were obtained. No thyristor degradation was observed after more than one million pulses at a PRF up to 1 kHz in burst mode. Thyristor recovery time was 250 µs. The switching efficiency was up to 98% depending on dV/dt and stored energy. © 2019 CERN.Russian Foundation for Basic Research, RFBR: 17-08-00406, 18-08-01390Russian Academy of Sciences, RAS: 10.The work was supported by RFBR Grants Nos. 17-08-00406 and 18-08-01390, and by RAS Program Project No. 10. The study in part was carried out on the equipment of the Collective use centre at the Institute of Electrophysics, Ural Branch, Russian Academy of Sciences

P I SPS I B

Abstract The SPS internal beam dump has been designed for beam specifications well below the HL-LHC ones, and for modes of operation which may not be adequate for the HL-LHC era. The present system suffers from several limitations in the allowed intensity and energy range, and its vacuum performance affects nearby high-voltage kicker systems. In this report the limitations of the internal beam dump system are reviewed, and the possible improvements compared. Preliminary upgrade proposals are presented, taking into consideration the expected operational HL-LHC parameters

Future circular collider injection and extraction kicker topologies and solid state generators

A 100 TeV center-of-mass energy frontier proton collider, in a new tunnel of 80–100 km circumference, is a central part of CERN’s Future Circular Colliders (FCC) design study. The designs of the injection and extraction systems of the FCC are initially based upon the parameters of the injection and extraction systems of the Large Hadron Collider and a preliminary study of the FCC beam optics and lattice. The injection and, in particular, the extraction systems of the FCC have to be highly reliable. In order to achieve high reliability, solid state switches will be used for the generators of the injection and extraction systems. This paper discusses topologies of these kicker systems, which are presently under consideration