Janne Holma

The Prototype Inductive Adder With Droop Compensation for the CLIC Kicker Systems

The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity and a nominal center-of-mass energy of 3 TeV. The CLIC predamping rings and damping rings (DRs) will produce, through synchrotron radiation, an ultralow emittance beam with high bunch charge. To avoid beam emittance increase, the DR kicker systems must provide extremely flat, high-voltage, pulses. The specifications for the extraction kickers of the DRs are particularly demanding: the flattops of the pulses must be ±12.5 kV with a combined ripple and droop of not more than ±0.02% (±2.5 V). An inductive adder is a very promising approach to meeting the specifications. Recently, a five-layer prototype has been built at CERN. Passive analog modulation has been applied to compensate the voltage droop, for example of the pulse capacitors. The output waveforms of the prototype inductive adder have been compared with predictions of the voltage droop and pulse shape. Conclusions are drawn concerning the design of the full-scale prototype inductive adder.

Preliminary design of the pulse generator for the CLIC DR extraction system

The Compact Linear Collider (CLIC) study is exploring the scheme for an electron-positron collider with high luminosity (1034 – 1035 cm−2s−1) 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. To limit the beam emittance blowup due to oscillations, the pulse power modulators for the DR kickers must provide extremely flat, high-voltage, pulses: specifications call for a 160 ns duration flattop of 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02%. In order to meet these demanding specifications, a combination of broadband impedance matching, optimized electrical layout and advanced control techniques is required. A solid-state modulator, the inductive adder, is the most promising approach to meeting the specifications; this topology allows the use of both digital and analogue modulation. To effectively use modulation to achieve such low ripple and droop requires an in-depth knowledge of the behaviour of the solid-state switching components and their gate drivers, as well as a thorough understanding of the overall circuit dynamics. Hence, circuit simulation tools have been employed to study the proposed inductive adder and various control schemes. This paper describes the initial design of the inductive adder and the use of active-filtering control algorithms for achieving the required pulse waveform.

Initial measurements on a prototype inductive adder for the CLIC kicker systems

The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the damping ring kicker systems must provide extremely flat, high-voltage, pulses. The specifications for the extraction kickers of the DRs are particularly demanding: the flattops of the pulses must be ±12.5 kV with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications. To achieve ultra-flat pulses with a fast rise time the output impedance of the inductive adder needs to be well matched to the system impedance. The parasitic circuit elements of the inductive adder have a significant effect upon the output impedance and these values are very difficult to calculate accurately analytically. To predict these parameters, the 3D geometry of the adder stack and its primary circuits has been modelled using FastHenry simulation code. Recently, a five layer prototype has been built and measurements have commenced. The parasitic elements of the primary and secondary circuits of the prototype have also been measured and these values are compared with predictions. In this paper, initial results of the measurements are described and conclusions are drawn concerning the design of the prototype inductive adder.

Inductive adders for replacing thyratron based modulators at CERN

Line-type modulators, for example pulse forming lines and pulse forming networks, which use thyratron switches, are currently used in many pulse power systems at CERN. Solid-state modulators implemented with inductive adder technology could replace thyratron based designs in many applications and potentially improve dynamic range, maintainability and reliability of the systems. This paper will discuss the application of an inductive adder for the pulse power modulator of both a future circular collider and as an upgrade to an existing, 45 year old, kicker system.

Measurements on prototype inductive adders with extreme flat-top output pulses for CLIC damping ring extraction kickers

The specifications of the extraction kicker systems for the damping rings of the Compact Linear Collider call for 160 ns duration flat-top pulses of ±12.5 kV, 250 A, with combined ripple and droop of ±0.02 %. Pulse waveforms of two 3.5 kV prototype inductive adders have demonstrated ±0.05 % relative flat-top stability.

Initial measurements on a prototype inductive adder with ultra-flat output pulse for the CLIC kicker systems

The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings (DRs) will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the damping ring kicker systems must provide extremely flat, high-voltage, pulses. The specifications for the extraction kickers of the DRs are particularly demanding: the flattops of the pulses must be ±12.5 kV with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications.

Design and initial measurements of a 12.5 kV prototype inductive adder for CLIC DR kickers

The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse generators for the damping ring kickers must provide extremely flat, high-voltage pulses. The specifications for the damping ring extraction kickers call for 160 ns or 900 ns duration flat-top pulses of +/− 12.5 kV, 250 A, with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meeting the specifications. The first 20-layer prototype inductive adder is being assembled at CERN and initial measurements, with the 5 first layers, have commenced. This paper presents the detailed design of the full-scale, 12.5 kV, 250 A, prototype inductive adder. The prototype adder has an active analogue modulation layer to compensate droop and ripple, in order to reach ultra-low flat-top stability. In this paper, the design of the full-scale 12.5 kV prototype inductive adder is explained in detail and the results of the initial measurements, carried out with the first five assembled layers, are presented.

Sensitivity analysis for the CLIC damping ring inductive adder

The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse generators for the damping ring kickers must provide extremely flat, high-voltage pulses. The specifications for the extraction kickers of the CLIC damping rings are particularly demanding: the flattop of the output pulse must be 160 ns duration, 12.5 kV and 250 A, with a combined ripple and droop of not more than +/-0.02 %. An inductive adder allows the use of different modulation techniques and is therefore a very promising approach to meeting the specifications. PSpice has been utilised to carry out a sensitivity analysis of the predicted output pulse to the value of both individual and groups of circuit components: these results are used to define component performance requirements, nominal values and tolerances. This paper reports the simulation results as well as tests and measurements of the various candidate components, including semiconductor switches, pulse capacitors and transformer cores.