Search

In the framework of the LIU project, several modifications have been made to the CERN PS injection kicker system during the winter stop 2016-2017 (EYETS). Current waveform and beam-based measurements were carried out in 2017 to validate the implemented design changes by observing the magnetic field impact on the beam. During these long-term measurements, increased values for the rise and fall times were observed when compared to single shot observations of the current waveform. An unknown source of jitter-like pre-firing in the main switch has been identified, creating an additional challenge to meet the already tight system rise and fall time specifications. This paper briefly describes the efforts made to fine tune the pulse generator after the EYETS, summarises the optimised configuration and analyses the observed jitter events. A new triggering system design is briefly outlined to address the issue., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Prior to Long Shutdown 1 (LS1) one of the LHC injection kickers (MKIs) occasionally exhibited high temperatures leading to significant turnaround times. After a successful impedance mitigation campaign during LS1, the MKI ferrite yokes have remained below their Curie point and have not limited LHC's availability. However, for HL-LHC operation the MKI yokes are expected to exceed their Curie temperatures after long physics runs. To ensure uninterrupted future HL-LHC operation, a modified beam screen design, relocating some of the heat load to more easily cooled parts, and a suitable cooling system are under development as the current baseline for the HL-LHC upgrade of the MKIs. An upgraded beam screen providing such relocation has been designed, simulated and compared to the existing model. To validate simulations, two longitudinal beam coupling impedance measurement techniques have been used and the results are compared to predictions. The modified beam screen was implemented in an upgraded MKI installed in the LHC during the Year End Technical Stop (YETS) 2017/18., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The HEPS plans to adopt on-axis injection scheme because the dynamic aperture of machine is not large enough for off-axis injection for its baseline 7BA lattice design. A sets of super fast kicker and pulser of ±15kV amplitude, 15ns pulse bottom width are needed for bunch spacing of 10ns to minimize perturbation on adjacent bunches. To achieve these requirement, a multifaceted R&D program including the strip-line kicker and HV pulser, was initiated last 2 years. So far, the prototype development of a 750mm long strip-line kicker and a DSRD pulser was completed and the preliminary test results show they can meet the baseline requirement of the HEPS., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The modulators of the European XFEL produce high voltage, at the 10kV level, having a power of up to 16.8 MW for 1.54 ms. The operation frequency of the super-conducting inac is 10 Hz. The series production of the 29 modulators started in 2012. The first modulator began operation in 2014 and the start of linac was beginning 2017. The R&D phase for the modulators started directly with the development of superconducting cavities. Besides the pulse generation, the modulator had to suppress the 10 Hz repetition rate in order not to disturb the grid. Another unique demand was the development of pulse cables. Since the power RF had to be generated in the tunnel, the klystrons were installed near the cavities. However, the modulators had to be installed outside of the tunnel for space, maintenance reasons and radiation concerns. This transmission of high power pulses via long cables is unique in the world and the suppression of EMI effects was mandatory. During the first year operation no EMI disturbances of other systems were detected and the modulator system works as expected., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The electron-ion collider eRHIC requires a variety of kickers and septa for injection and extraction of beams throughout the entire collider complex. We plan to use pulsed systems for beam injection and extraction in Electron RCS, Electron Storage Ring, and Hadron ring. In this paper, we describe the pulsed systems required for beam transfer in the eRHIC Ring-Ring Pre-conceptual Design. We will outline the parameter ranges, technology choices, and opportunities for research and development in pulsed power technology., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

A next generation electron storage ring represented by a diffraction-limited light source pursues an extremely low emittance leading to a small dynamic aperture and short beam lifetime. The top-up injection is hence indispensable to keep the stored beam current. The beam orbit fluctuation caused by the injection magnets should seriously obstruct utilization of an electron beam with sharp transverse profile. In order to solve these problems, a novel off-axis in-vacuum beam injection system was proposed. In the system, twin kicker magnets driven by a single solid-state pulsed power supply to launch a linear pi- bump orbit is the key to suppress the horizontal orbit fluctuation down to a level of several microns. Here, a big challenge is to achieve the magnetic field identity of the two kickers within an accuracy of 0.1%. This presentation overviews the proposed injection system and reports the development status focusing on the solid-state pulse generator., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The CERN Large Hadron Collider (LHC) is equipped with two fast pulsed magnet systems (MKIs) that inject particle beams from the injector chain. Future operation for High Luminosity LHC (HL-LHC) with high intensity beams will cause heating of the ferrite yokes of the MKIs beyond their Curie temperature, preventing injection until the yokes cool down. Beam coupling impedance studies show that it is possible to move a substantial portion of the beam induced power deposition from the upstream ferrite yokes, which are the yokes with the highest power deposition, to ferrite rings located at the upstream end of the magnet. Thermal predictions show that this power redistribution, combined with the installation of a cooling system around the rings, will maintain the temperatures of all the yokes and ferrite rings below their Curie point. Since the rings are not pulsed to high voltage, whereas the ferrite yokes are, the installation of a cooling system is feasible around the rings. The proposed design of the cooling system will be tested to ensure good performance before its installation on the MKIs. The details of the simulations and the design process are reported., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The PIP-II project is a program to upgrade the Fermilab accelerator complex. The PIP-II linac includes a 2.1 MeV Medium Energy Beam Transport (MEBT) section that incorporates a unique chopping system to perform arbi-trary, bunch-by-bunch removal of 162.5 MHz structured beam. The MEBT chopping system will consist of two identical kickers working together and a beam absorber. One design of two having been proposed has been a 200 Ω characteristic impedance traveling wave dual-helix kicker driven with custom designed high-speed switches. This paper reports on the first performance results of one prototype kicker built, installed and tested with beam at the PIP-II Injector Test (PIP2IT) facility. The helix deflector design details are discussed. The electrical performance of the high-speed switch driver operating at 500 V bias is presented. Tests performed were chopping beam at 81.25 MHz for microseconds as well as with a truly arbitrary pattern for 550 us bursts having a 45 MHz average switching rate and repeating at 20 Hz., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

An upgrade of the LHC injection kickers is necessary for HL-LHC to avoid excessive beam induced heating of these magnets: the intensity of the HL-LHC beam will be twice that of LHC. In addition, in the event that it is necessary to exchange an injection kicker magnet, the newly installed kicker magnet would limit HL-LHC operation for a few hundred hours due to dynamic vacuum activity. Extensive studies have been carried out to identify practical solutions to these problems: these include redistributing a significant portion of the beam induced power deposition to ferrite parts of the kicker magnet which are not at pulsed high voltage and water cooling of these parts. Furthermore a surface coating, to mitigate dynamic vacuum activity, has been selected. The results of these studies, except for water cooling, have been implemented on an upgraded LHC injection kicker magnet: this magnet was installed in the LHC during the 2017-18 Year End Technical Stop. This paper presents the upgrades, including some test and measurement results., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

An ultra-high-speed short pulse switch for high power have been developed by using SIC - MOSFET which is one of next generation semiconductors. Semiconductor switches using SIC-MOSFETs are expected to replace the thyratron, and they are composed of circuits in which many semiconductor switches are multiplexed in series and parallel for high power. Semiconductor switches using SIC-MOSFETs are expected to replace the thyratron, and they are also designed by connecting many semiconductor switches in parallel-series. To realize a low switching noise, it is common to form a symmetrical circuit. However, as the number of parallel connections increases, the circuit length between input and output becomes longer, so the output waveform is distorted due to any timing jitter or level fluctuation. Therefore, we propose a radially symmetric type of a module switch which does not cause level fluctuation due to the timing jitter by equalizing the circuit length independently of the number of semiconductor switches. The design and preliminary test results of two types of switch circuits, radially symmetric type and line symmetric type are presented here., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Diversified Technologies, Inc. (DTI) has developed a unique short pulse klystron modulator system for the Compact Linear Advanced Research Accelerator (CLARA) Project at Daresbury Laboratory. One unit has been delivered and three more are on contract. This system is based on the combination of a high voltage solid-state switch, with a conventional 1:7 pulse transformer, and a passive pulse corrector with automated adjustment. This unique passive circuitry delivers the extremely flat output pulse required for advanced accelerator applications. The CLARA modulators share design elements with previous DTI modulators which provides both a lower cost and easier to maintain system. The modulators are designed to pulse 80 MW-class klystrons at an avg power of 250 kW and provides adjustable high efficiency operation in the 45 kV to 450 kV range for currents up to 545 A and pulse lengths of 1.5 to 4.0 μs. One key objective of modulator development is optimization of voltage flatness (± 0.02 %), stability (± 0.05 %), and reproducibility (± 0.05 %)., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

A highly reliable kicker system is required as part of the injection for the FCC. A significant weak point of conventional kicker systems is often the pulse generator, where a Pulse Forming Network/Line (PFN/PFL) is discharged through a thyratron switch to generate the current pulse for the kicker magnet. This design has several disadvantages: in particular the occasional erratic turn-on of the switch which cannot be accepted for the FCC. A potential replacement is the inductive adder (IA) that uses semiconductor switches and distributed capacitors as energy storage. The modular design, low maintenance and high flexibility make the IA a very interesting alternative. In addition, the ability to both turn-on and off the current also permits the replacement of PFN/PFL by the capacitors. A first FCC prototype IA, capable of generating 9 kV and 2.4 kA pulses, has been designed and built at CERN. It will be upgrade to a full-scale prototype (15 kV, 2.4 kA) in 2018. This paper presents measurement results from the 9 kV prototype and outlines the conceptual changes and expected performance of the 15 kV prototype., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The CLIC study is investigating the technical feasibility of an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. Pre-damping rings and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. The DR kicker systems must provide extremely stable field pulses to avoid beam emittance increase. The DR extraction kicker system consists of a stripline kicker and two pulse modulators. Specifications for the electromagnetic field pulses require that the modulator produce pulses of 160 or 900 ns flattop duration, ±12.5 kV and 305 A, with ripple and droop of not more than ±0.02 % (±2.5 V) with respect to an ideal waveform. Inductive adder topology has been chosen for the pulse modulators where the output waveform can be adjusted by applying analogue modulation methods. Two full-scale, 20-layer, 12.5 kV prototype inductive adders have been designed and built, and they are being tested at CERN. These modulators will be tested with a prototype stripline kicker, installed in a beamline at ALBA Synchrotron Light Source in Spain. The results of the laboratory tests and measurements are presented., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

During Run 1 of the LHC, one of the injection kicker magnets (MKIs) exhibited an excessively high ferrite temperature, caused by coupling of the high intensity beam to the real impedance of the magnet. Beam-screen upgrades, implemented during Long Shutdown 1 (LS1), have been very effective in reducing beam coupling impedance and since then the MKIs have not limited LHC's availability. However, temperature measurements during operation have shown that one end of the MKI's ferrite yoke is consistently hotter than the other. Detailed simulation models and data post-processing algorithms have been developed to understand and mitigate the observed behaviour. In the present paper, the model used to obtain the power loss distribution along the magnet is presented. The model is subsequently applied to two MKI design configurations under study: (i) the one currently in operation and (ii) an upgraded magnet that was installed in the LHC tunnel during the Year End Technical Stop (YETS) 2017/18. In order to validate the expected behaviour a novel measurement technique was developed, applied in both configurations and compared to predictions. The results obtained are reported and conclusions regarding the effectiveness of the design are drawn., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Diversified Technologies, Inc. (DTI) assembled a prototype pulse generator capable of meeting the original specifications for the Next Generation Light Source (NGLS) fast deflector. The ultimate NGLS kicker driver must drive a 50 Ω terminated Transverse Electromagnetic (TEM) deflector blade at 10 kV, with flat-topped pulses and a sustained repetition rate of 100 kHz. Additional requirements of the specification include a 2 ns rise time (10 – 90%), a highly repeatable flattop with pulse width from 5 – 40 ns, and a fall time less than 1 μs (down to 10-4 of the peak value). The driver must also effectively absorb high-order mode signals emerging from the deflector itself. It is envisioned that a scintilla of deflection will be imparted by a symmetric pair of shaped parallel deflection blades, pulsed in opposition at 10 kV. Within the guide, each TEM wave produced by the two pulse generators traverses the guide synchronously with the selected (relativistic) charge packet. The DTI team has designed and demonstrated the key elements of a solid state kicker driver capable of meeting the NGLS requirements, with possible extension to a wide range of fast-pulse applications., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The injection system is one of the important systems which determine efficiency and reliability of the accelerator facility. The spark gap switches (SGS), which were used before at Siberia-2 in high voltage nanosecond pulse generators, are the critical components requiring permanent maintenance. SGS has a series of limitations such as a relatively large pulse jitter and a work at a high pressure nitrogen atmosphere. The new injection system uses new half-sine microsecond pulse generators which based on Pseudo-Spark Switches. Some technical aspects of the new injection system are considered and results of generators operation are shown in the article., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

Saturable pulse transformers (SPTs) based on multiple batches of windings in parallel combination and coaxial cylindrical conductors are presented. The proposed SPT can be employed as the transformer and magnetic switch simultaneously for pulse capacitor or high-voltage pulse modulator of several hundred kV range. The SPT, with important features such as auto-resetting of core, high step-up ratio and low saturation inductance, achieves a compact integration of common transformer and magnetic switch. In the SPT, The physical suppression effect caused by reversed magnetic coupling mechanism among primary and secondary windings can reduce the saturation inductance of the SPT windings to a level lower than their structure inductances, which helps to achieve a magnetic switch with low saturation inductance. The proposed SPTs were applied in a high power pulse modulator based on a helical Blumlein pulse forming line (HBPFL). When the SPT played as a pulse transformer, the HBPFL can be charged to 200 kV. When the SPT played as a main magnetic switch of the HBPFL, it helped to form a quasi-square voltage pulse with amplitude of 180 kV，pulse duration of 130 ns, rise time of 60 ns., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

For initial operation of the MAX-IV and Solaris storage rings the single dipole kickers were decided to use. The pulsers wich drive the magnets have the following requirements: current amplitude up to 4kA (3 GeV ring), pulse length 0.6us (1.5 GeV ring) and 3.5us (3 GeV ring), pulse amplitude stability ±0.1%, timing jitter, Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

Four lumped inductance injection kicker magnets for the J-PARC main ring (MR) produce a kick of 0.1096 T·m with a 1% to 99% rise-time of about 400 nsec. A residual field of about 6% of the flat-top exists at the tail of the pulse due to an impedance mismatching. The residual field is required to be suppressed less than 1% to reduce injection losses. For a higher intensity beam operation, the kicker rise-time of less than 300nsec is required to inject longer beam bunches which reduces a space charge effect. During the long shutdown in FY2013, 140Ω resistor and 7nF capacitor were connected to the thyratron to improve the post-pulse shape. In addition, an optimization of a capacitance in the matching circuit was carried out to optimize the waveform. As the result, the rise-time of 195nsec and the residual tail field of 2% were achieved. However, another reflection peak of about 9% is appeared. We plan to compensate the effect of the new peak by using a new small kicker magnet. This paper discusses the detail of the circuit and the beam test results., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

In October 2013, Diversified Technologies, Inc. (DTI) successfully installed and began operation of a 120 kV, 120 A, 1.7 ms Marx modulator for the High Energy Accelerator Research Organization (KEK) in Japan. Originally conceived, and built under a DOE SBIR grant to support SLAC (completed in 2010), the Marx bank modulator demonstrates a new technology for compact and economic ILC-class performance; the design meets the performance requirements for ILC, does so in a more compact form factor than other known technologies, and, we believe, will be more economic than other technologies. The basic concept of a Marx modulator is that it charges an array of capacitors in parallel (low voltage), then erects them in series to form a high-voltage discharge. Using DTI’s solid-state switches (instead of traditional spark gaps or SCRs) to construct a Marx modulator enables it to open and close; thus the capacitors serve as storage capacitors rather than fully exhausting during each pulse. The opening capability of the DTI switches also provides for arc protection of the load, exactly as they would in a hard-switch. Such a system requires no crowbar protection to protect the load against arcs., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

This report presents an overview of the magnetic horn and its pulsed power system at the upcoming FAIR (Facility for Antiproton and Ion Research) complex at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. In the planned antiproton (pbar) separator scheme a magnetic horn will be used as a device for collection and focusing of highly divergent antiprotons emerging from the target with energies around 3 GeV and within a cone of about 80 mrad .To achieve the desired focusing effect, the horn needs to be powered with a current pulse of 400 kA peak amplitude at the same repetition rate as the primary proton beam, i.e. 0.1 Hz. In future, operation up to 0.2 Hz is planned without major design alterations. Due to civil construction and radiation protection limitations, possible technical realization of this system has some key design issues. The aim is to develop a reliable and efficient magnetic horn system for effective focusing of antiprotons by producing a very strong pulsed magnetic field., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

A new induction synchrotron system using an induction cell has been developed and constructed at KEK*. In that system, the switching power supply is one of the key devices that realize digital acceleration. The requirements of the switching power supply are high voltage (2 kV) and high repetition frequency (1 MHz). In the present system, we used series connected MOSFETs as the switching device. However, series connection gives large complexity and less reliability. Among various switching devices, a SiC-JFET should be a promising candidate because it has ultrafast switching speed and high voltage blocking capability. We have developed a new and original SiC-JFET switching device and a compact switching power supply employing this switching element**. Now it is integrated into the induction acceleration system for the KEK-DA. Furthermore we have started development of the next generation of SiC package, which has higher voltage capability (2.4 kV) and 2 in 1 module construction. At the conference, the first experimental demonstration of heavy ion acceleration utilizing the SiC-JFET and the design status of the new device package will be presented., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

A terminated power cable is typically applied not only for terminated ends but also to connect two or more cables. The electric field inside the insulation layer becomes disturbed when a coaxial cable structure is broken and the electric stress increases near the ground edge. A structure of cone type is a major method to alter the lines of equi- potential and to relieve the electric stress around the ground. The dimensions of the cone depend on the cable structure. In this paper we introduce a way to calculate the displacement of equi-potential lines when a cone is brought into a coaxial cable, RG220, and then determine a suitable angle and length of the cone, which are important factors to withstand tens of kV and even greater. The corresponding high-voltage tests are also presented here., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

TPS requires highly precise and stable pulsed magnets for top-up mode operation. One injection and two extraction in vacuum kicker magnets in the booster ring are designed and noticed to minimize driving voltage. The HV insulation for magnet itself and vacuum feedthrough need to be tested. A DC withstand voltage tester MUSASHI 3802 (Model: IP-701G) is used to test the DC breakdown voltage, which the maximum driving voltage is 37 kV. And the AC withstand voltage tester was also test the AC breakdown voltage. Thicker than 10 mm ceramic plate could effectively avoid the breakdown occurred with 37 kV DC charging. Thus HV withstand voltage will be higher in vacuum chamber and the insulation with HV will not be the problem., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

Solid state is one of the most important development directions for pulsed power technologies. For GW level pulse generators, switches and pulse forming units are difficult to implement with solid state components restricted by high power tolerance and high voltage insulation. Under certain pulse power, operation voltage is decided by impedance of the pulse forming unit, which means that pulse modulation with low impedance method should help improve insulation strength of a pulsed power system. Therefore, a high power, low impedance pulse forming network is developed based on solid components of ceramic capacitors in this research. It is designed that the impedance is 1.6 Ω, the pulse width is about 150 ns, and the output power is above 1 GW. Low impedance is accomplished via several pulse forming units connected in parallel with a circumferential structure, which could reduce the stray inductance due to good symmetrical characteristics. Key factors influencing pulse modulation process are investigated, stray parameters are examined by electromagnetic calculations and preliminary experiments are carried out, with results giving reasonable agreement with the theoretical cases., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

LHC operation with high intensity beam, stable for many hours, resulted in significant heating of the ferrite yoke of the LHC Injection Kicker Magnets. For one kicker magnet the ferrite yoke approached its Curie temperature. As a result of a long thermal time-constant the yoke can require several hours to cool sufficiently to allow re-injection of beam, thus limiting the running efficiency of the LHC. The beam screen, which screens the ferrite yoke from wakefields, has been upgraded to limit ferrite heating. In addition it is important to improve the cooling of the ferrite yoke: one method is to increase the internal emissivity of the cylindrical vacuum tank, in which the kicker magnet is installed. This paper describes a method developed for measuring the emissivity of the inside of the tanks, which has been benchmarked against measurements of the ferrite yoke temperature during heat treatment in an oven and transient thermal simulations. Conclusions are drawn regarding an ion bombardment technique evaluated for improving emissivity without degrading vacuum properties. In addition initial concepts for improved cooling are presented., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

High energy, short-pulse modulators are being re-examined for the Compact Linear Collider (CLIC) and numerous X-Band accelerator designs. At the very high voltages required for these systems, all of the existing designs are based on pulse transformers, which significantly limit their performance and efficiency. There is not a fully optimized, transformerless modulator design capable of meeting the demanding requirements of very high voltage pulses at short pulse widths. Under a U.S. Department of Energy grant, Diversified Technologies, Inc. (DTI) is developing a short pulse, solid-state Marx modulator. The modulator is designed for high efficiency in the 100 kV to 500 kV range, for currents up to 250 A, pulse lengths of 0.2 to 5.0 μs, and risetimes, Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity (10³⁴ - 10³⁵ cm²/s) and a nominal centre-of-mass energy of 3 TeV: CLIC would complement LHC physics in the multi-TeV range. The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve the very low emittance, through synchrotron radiation, needed for the luminosity requirements of CLIC. In order to limit the beam emittance blow-up due to oscillations the combined flat-top ripple and droop of the field pulse, for the DR extraction kickers, must be less than 0.015%. In addition, the allowed beam coupling impedance for the kicker systems is also very low: a few Ohms longitudinally and a few MΩ/m transversally. This paper discusses initial ideas for achieving the extremely demanding requirements for the PDR and DR kickers., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

A five-turn continuous extraction is currently used to transfer the proton beam from the CERN PS to the SPS. This extraction uses an electrostatic septum to cut the filament beam into five slices, causing losses of about 15 %. These losses would be an even greater drawback when the beam intensity is further increased for the CERN Neutrinos to Gran Sasso facility. To overcome this, a Multi-Turn Extraction (MTE) has been implemented, in which the beam is separated, prior to extraction, into a central beam core and four islands. Each beamlet is extracted using a set of kickers and a magnetic septum. For the kickers two new pulse generators have been built, each containing a lumped element Pulse Forming Network (PFN) of 12.5 Ohms, 80 kV and 10.5 μs. For cost reasons existing 15 Ω transmission line kicker magnets are reused. The PFN characteristic impedance deliberately mismatches that of the magnets to allow a higher maximum kick. The PFN design has been optimised such that undesirable side-effects of the impedance mismatch on kick rise-time and flat-top remain within acceptable limits. The kicker systems put in place for the current first phase of MTE are presented., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

In many particle accelerators considerable amounts of RF power reaching the megawatt level are converted into heat in dummy loads. After an overview of RF power in the range 200 MHz to 1 GHz dissipated at CERN we discuss several developments that had come up in the past using vacuum tube technology for RF-DC conversion. Amongst those the developments the cyclotron wave converter CWC appears most suitable. With the availability of powerful Schottky diodes the solid state converter aspect has to be addressed as well. One of the biggest problems of Schottky diode based structures is the junction capacity. GaAs and GaN Schottky diodes show a significant reduction of this junction capacity as compared to silicon. Small rectenna type converter units which had been already developed for microwave powered helicopters can be used in waveguides or with coaxial power dividers., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The goal of the present CLIC Test Facility (CTF3) is to demonstrate the technical feasibility of specific key issues of the CLIC scheme. The extracted drive beam from the combiner ring (CR), a pulse of 35 A magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX). A Tail Clipper (TC) kicker is required, in the CR to CLEX transfer line, to allow the duration of the beam pulse to be adjusted: the unwanted bunches are kicked into a collimator. The TC must have a fast field rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss. Striplines are used for the TC: to establish the required fields, the applied pulse wave front must fully propagate along the striplines. To reduce the wave front propagation time, the overall length of the stripline assembly is sub-divided into 4 sections. The TC has been designed with the aid of detailed numerical modelling: the stripline cross-section and coaxial-to-stripline transitions were carefully optimized using a 3D code. The results of simulations and the measured behaviour of the striplines are presented; in addition measured current pulses are shown., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Vacuum insulators composed of alternating layers of metal and dielectric, known as high-gradient insulators (HGIs), have been shown to withstand higher electric fields than conventional insulators. Generally, vacuum insulator failure is due to surface flashover, initiated by electrons emitted from the triple junction. These electrons strike the insulator surface and produce secondary electrons, which also strike the insulator surface to create more secondary electrons and lead to avalanche. Magnetic field from the external sources, the high-current electron beam, the conduction current in the transmission line or the displacement current in the insulator can deflect primary and secondary electrons’ trajectories either toward to or away from the insulator surface, and hence affect the performance of the high-voltage vacuum insulator. The displacement current effects are particularly interesting for short pulse applications. This paper presents the displacement current effects with various short applied voltage pulses on performance of high-gradient insulators. Optimal HGI configurations will also be discussed., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Diversified Technologies, Inc. (DTI) recently delivered a 500 kW CW, 33 kV solid-state test stand for the evaluation and conditioning of high power tetrodes employed in accelerator and radar systems. The test system consists of DTI-manufactured and commercially-sourced power supplies, a DTI high voltage opening switch, and DTI controls. Combining an opening switch and fast responding power supplies allows the hi-potting and high power burn-in to be consolidated in one test stand. Faulty tubes, which would not operate in a crowbar-equipped modulator, and could not be processed to health on a high potter, can be revived to health with this fast opening switch circuitry. By limiting peak fault current and follow-on-current, the total energy in an arc event is greatly minimized, reducing damage inside the tube. If greater energy (or action) is required for initial tube processing, additional load capacitance downstream of the switch can be added into the circuit for ¿spot knocking¿ purposes. This test stand is capable of operation in pulsed mode as well as CW. This paper will address the design and construction of the test stand and discuss results since its installation., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

SLAC National Accelerator Laboratory has built and is currently operating a first generation prototype Marx klystron modulator to meet ILC specifications. Under development is a second generation prototype, aimed at improving overall performance, serviceability, and manufacturability as compared to its predecessor. It is designed around 32 cells, each operating at 3.75 kV and correcting for its own capacitor droop. Due to the uniqueness of this application, high voltage gate drivers needed to be developed for the main 6.5 kV and droop correction 1.7 kV IGBTs. The gate driver provides vital functions such as protection of the IGBT from over-voltage and over-current, detection of gate-emitter open and short circuit conditions, and monitoring of IGBT degradation (based on collector-emitter saturation voltage). Gate drive control, diagnostic processing capabilities, and communication are digitally implemented using an FPGA. This paper details the design of the gate driver circuitry, component selection, and construction layout. In addition, experimental results are included to illustrate the effectiveness of the protection circuit., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The Next Generation Light Source (NGLS) at Lawrence Berkeley Laboratory is a 2.4 GeV linear accelerator with up to ten FELs. Each of the FELs require a fast kicker, with the exception of the final one which can use a normal bend magnet. The requirements for the kickers are to deflect the linac beam by an angle of 3 mrad with a magnetic length of 2 m, and an aperture size of 17 by 17 mm. A strip line magnet with an impedance of 50 Ohms being feed from the opposite direction as the beam has been selected for prototyping. The modulator requirements to drive such a magnet are ±15 kV and ±300 A, with rise and fall times of 5 ns and a flat top of 10 ns. The pulse to pulse stability must be better than 0.01% of the peak value. The design of the modulator is an inductive adder with 20 cells, each driven by 12 power MOSFETs. This paper describes details of the design as well as present preliminary test data., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

3 GeV rapid cycling synchrotron (RCS) of J-PARC accelerates proton beams from the 181 MeV up to 3 GeV. The RCS injects the beam to the Main Ring and transports it to the muon production target and neutron production target in the Materials and Life Science Experimental Hall. Proton beams in the RCS are fast extracted by kicker magnets at the repetition rate of 25 Hz. The rise time of the magnetic field is approximately 260 ns due to the propagation time through the coaxial cable and the kicker magnet itself. The flat-top length of it is required to 840 ns in order to extract two beam bunches. Pulse forming lines (PFL) and thyratrons are used to make the rise time and the flat-top, at the maximum charging voltage of 80 kV. Two thyratrons, which is a CX1193C made by e2V Ltd., are used for a power supply. 16 thyratrons are used in the eight power supplies of the kicker system. Since thyratrons are gaseous discharge switching devices, they often make misfire or self-breakdown in several hours. In this paper, present status of operation and voltage adjustment method of the reservoir and cathode heater power supply of the thyratrons in the kicker system are described., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

A Marx-topology klystron modulator is under development for the International Linear Collider (ILC) project*. It is envisioned as a lower cost, smaller footprint, and higher reliability alternative to the present, bouncer-topology, baseline design. The application requires 120 kV (±0.5%), 140 A, 1.6 ms pulses at a rate of 5 Hz. The Marx constructs the high voltage pulse by combining, in series, a number of lower voltage cells. The Marx employs solid state elements; IGBTs and diodes, to control the charge, discharge and isolation of the cells. Active compensation of the output is used to achieve the voltage regulation while minimizing the stored energy. The developmental testing of a first generation prototype, P1, has been completed. This modulator has been integrated into a test stand with a 10 MW L-band klystron, where each is undergoing life testing. Development of a second generation prototype, P2, is underway. The P2 is based on the P1 topology but incorporates an alternative cell configuration to increase redundancy and improve availability. Status updates for both prototypes are presented., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

XFEL/SPring-8 will use 72 line type modulator pulse-power supply for 66 C-band klystrons, 4 S-band, one L-band and pulsed 500 kV electron gun. In order to make the size smaller to fit the space available in the high gradient C-band accelerator, we have developed all in one box design of modulator. Using metal monocok design, filled with oil, it becomes possible to fit all circuitry: PFN, thyratron, pulse transformer, klyston socket, and protection circuit into a metal box of W 1m x L 1.7m x H 1m, which provides strong support for massive klystron and solenoide with lead shield and functions as superior EM shiled. We developed high precission HV charger for PFN, which has stability better than 100 ppm.pp. Modulator and PFN chargers are under mass prodution., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Diversified Technologies, Inc.(DTI) has delivered a fully solid state Klystron Power Supply for the ISIS Front End Test Stand to Rutherford Appleton Laboratory in the UK. The new pulsed power supply drives a Toshiba E3740A klystron in preparation for construction of a system to demonstrate high quality intense chopped beams. DTI’s system represents a significant advance in solid-state high power accelerator technology based upon a hard switch developed for the US Department of Energy (DOE) to meet similar requirements for the International Linear Collider(ILC). The system includes two 220 kW switching power supplies, a 110 kV solid state hard switch pulse modulator, mod anode and filament power supplies, klystron fault protection, and interfaces to the ISIS controls. This paper will address the design and construction of the KPS system, as well as test results from the installation at RAL in May 2009., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Proton and ion beams will be injected into LHC at 450 GeV by two kicker magnet systems, producing magnetic field pulses of up to 7.8 µs flat top duration with rise and fall times of not more than 900 ns and 3 µs, respectively. Both systems are composed of four traveling wave kicker magnets, powered by pulse forming networks. One of the stringent design requirements of these systems is a field flat top and post pulse ripple of less than ±0.5 %. A carefully matched high bandwidth system is required to obtain the stringent pulse response. Screen conductors are placed in the aperture of the kicker magnet to provide a path for the image current of the, high intensity, LHC beam and screen the ferrite against Wake fields: these conductors affect the field pulse response. Recent injection tests provided the opportunity to directly measure the shape of the kick field pulse with high accuracy using a pilot beam. This paper details the measurements and compares the results with predictions and laboratory measurements., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

A test unit of a pulse-forming-network (PFN) kicker power supply has been designed and fabricated for Taiwan Photon Source (TPS) beam injection/extraction of the booster ring. In order to fulfill the requirements, the performance of the designed unit has been bench tested and the results are examined for evaluation purpose. The pulse-to-pulse stability and the flattop specifications are specified according to the beam injection/extraction requirements. Effort has been made to enhance the rise/fall time of the delivered pulse current. The engineering evaluation and its possible application for beam diagnostics purpose are briefly discussed., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

A description is given of the development of slow-wave chopper structures for the 3.0 MeV, 60 mA, H‾ MEBT on the RAL Front-End Test Stand (FETS) [1]. ’Helical’ and ’Planar’ electrode designs [2] have been developed by simulating their high frequency (HF) electromagnetic properties in a commercial 3D code [3], and the manufacture of prototypes has helped to validate the predictive accuracy of the design code, and the selection of suitable machine-able ceramics and alloys of copper and aluminium. A description is also given of a novel abrasive brushing process that enables fine tuning of stripline characteristic impedance by facilitating control of stripline edge radius. The transmission line properties of the previously described ’Helical’ test assembly [4] are compared with those of the recently completed ’Planar’ test assembly. Finally, the development status of a related prototype high voltage pulse generator is presented., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The vertical beam dump system of the CERN Super Proton Synchrotron (SPS) uses two matched magnets with an impedance of 2 Ω and combined kick strength of 1.152 Tm at 60 kV supply voltage. For historical reasons the two magnets are powered from three 3 Ω pulse forming networks (PFN) through three thyratron-ignitron switches. Recently flashovers were observed at the entry of one of the magnets, which lead, because of the electrical coupling between the kickers, to a simultaneous breakdown of the pulse in both magnets. To improve the reliability an upgrade of the system was started. In a first step the radii of surfaces at the entry of the weak magnet were increased, and the PFN voltage was reduced by 4 %; the kick strength could be preserved by reducing the magnet termination resistance by 10 %. The PFNs were protected against negative voltage reflections and their last cells were optimised. In a second step the two magnets will be electrically separated and powered individually by new 2 Ω PFNs with semiconductor switches., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

This paper describes a long-pulse 1.3 GHz klystron modulator that was recently developed for the Superconducting RF Test Facility (STF) at High Energy Accelerator Research Organization (KEK). The modulators is a direct-switched-type design with a 1:15 step-up transformer and a bouncer circuit to compensate for the output pulse droop within ±0.5%; it can drive a klystron with up to 10 MW peak power, 1.5 ms rf pulse width, and up to 5 pps repetition rate. The main features of this modulator are the use of four 50 kW switching power supplies in parallel to charge the storage capacitors to 10 kV, self-healing-type capacitor to realize a compact storage capacitor bank, and a highly reliable IGBT switch which enables elimination of a crowbar circuit. Design considerations and its performance are presented. An IEGT (Injection Enhanced Gate Transistor) switch, composed of six series devices with a rating of 4.5 kV and 2100 A-DC, has been also developed and tested for R to realize a compact modulator., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

At the J-PARC 3-GeV injection, the injection painting area is designed to be different for supplying the MLF (Material Life Science Facility) and MR (50GeV Main Ring) beams. Along with the injection system in the ring, pulsed switching magnets which are installed in the injection beam-line should also have a function to control the beam orbit at 25Hz. The deflection angle ranges from 3 to 38 mrad to meet the user operation as well as the beam physics run., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

Fast kicker systems are required for the proposed upgrade of ALS to a diffraction-limited light source (ALS-U). The main approach is to have multiple stripline kicker magnets driven by inductive adders. The design details of the kicker structures and the inductive adder options will be discussed., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wakefields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. The design of the beam screen has been upgraded to overcome limitations and permit LHC operation with increasingly higher bunch intensity and short bunch lengths: the new design also significantly reduces the electric field associated with the screen conductors, decreasing the probability of electrical breakdown. The high voltage conditioning process for the upgraded kicker magnets is presented and discussed. In addition a test setup has been utilized to study flashover, on the inner wall of the ceramic tube, as a function of both applied voltage and vacuum pressure: results from the test setup are presented., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The possible issues related to the use of last-generations Insulated Gate Bipolar Transistors (IGBTs) switches into a Marx-topology klystron modulator are discussed. Experimental results obtained from two cells Marx prototypes using two different solutions, including single device and series connected devices both hard-switched, are presented. The use of single high voltage device per cell allowed us to obtain lower on-state voltage drop but much slower switching times. On the other side the series connection of lower voltage IGBTs results in much faster commutations and lower devices costs accompanied by a larger on state voltage drop., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan