L. Ducimetiere

An improved beam screen for the lhc injection kickers

The two LHC injection kicker magnet systems must produce a kick of 1.3 T.m with a flattop duration variable up to 7860 ns, and rise and fall times of less than 900 ns and 3000 ns, respectively. Each system is composed of two resonant charging power supplies (RCPSs) and four 5 Omega transmission line kicker magnets with matched terminating resistors and pulse forming networks (PFNs). A beam screen is placed in the aperture of the magnets: the screen consists of a ceramic tube with conductors on the inner wall. The conductors provide a path for the image current of the, high intensity,LHC beam and screen the ferrite against Wake fields. The conductors initially used gave adequately low beam coupling impedance however inter-conductor discharges occurred during pulsing of the magnet: an alternative design was discharge free at the nominal operating voltage but the impedance was too high for the ultimate LHC beam. This paper presents the results of a new development undertaken to meet the often conflicting requirements for low beam coupling impedance, fast magnetic field rise- time and good high voltage behaviour. High voltage test results and thermal measurements are also presented.

Experience with Kicker Beam Coupling Reduction Techniques

SPS beam impedance is still one of the worries for operation with nominal LHC beam over longer periods, once the final configuration will be installed in 2006. Several CERN SPS kickers suffer from significant beam induced ferrite heating. In specific cases, for instance beam scrubbing, the temperature of certain ferrite yokes went beyond the Curie point. Several retrofit impedance reduction techniques have been investigated theoretically and with practical tests. We report on experience gained during the 2004 SPS operation with resistively coated ceramic inserts in terms of kicker heating, pulse rise time, operating voltage, and vacuum behaviour. For another technique using interleaved metallic stripes we observed significant improvements in bench measurements. Advantages and drawbacks of both methods and potential combinations of them are discussed and simulation as well as measured data are shown. Prospects for further improvements beyond 2006 are briefly outlined.

High Voltage Measurements on Nine PFNS for the LHC Injection Kicker Systems

Each of the two LHC injection kicker magnet systems must produce a kick of 1.3 T. m with a flattop duration variable up to 7.86 ms, and rise and fall times of less than 900 ns and 3 ms, respectively. A kicker magnet system consists of four 5 W transmission line magnets with matched terminating resistors, four 5 W Pulse Forming Networks (PFNs) and two Resonant Charging Power Supplies (RCPSs). Six RCPSs and nine PFNs, together with associated switch tanks and dump switch terminating resistors, have been built at TRIUMF and all have been tested at up to 60 kV PFN voltage to ensure that the performance is within specification. This paper describes the HV measurements, compares these results with low voltage measurements and analyses the pulse performance of the PFNs. The measurements are compared with results from PSpice simulations.

Advances of Transmission Line Kicker Magnets

Fast pulsed magnets or kickers are widely used in circular accelerators for injection, fast extraction and beam excitation. As from the early 60’ s transmission line type kicker magnets have been employed to produce rectangular field pulses with good rise time. Over some 40 years this technology has evolved with the rising requirements. While the necessary kick strength has increased with the particle beam energy the strive for efficiency has pushed developments towards lower impedance systems and/or short circuited magnets. The flat top ripple is constrained by the maximally tolerable beam oscillation. The beam intensity can impose a screening of the magnet yoke. The most advanced features implemented in recent transmission line kicker magnets are reviewed and illustrated with examples from different laboratories.

Reliability Analysis of the LHC Beam Dumping System

The design of the Beam Dumping System of the Large Hadron Collider at CERN is aimed at ensuring a safe beam extraction and deposition under all circumstances. The system includes redundancy and continuous surveillance for most of its parts. Extensive diagnostics after each beam dumping action will be performed to reduce the risk of a faulty operation upon the subsequent dump trigger. Calculations of the system’s safety and availability are presented for the beam dumping kickers and septa magnets.

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.

A High Power Pulse System for the Beam Extraction from CERN's Large Hadron Collider

CERN, the European Organization for Nuclear Research, is close to starting operation of the large hadron collider (LHC). A beam dumping system must protect the LHC machine from damage, by reliably and safely extracting and absorbing the circulating beams when requested. For this purpose a beam extraction system has been designed, built, installed and tested. It is composed of 15 fast kicker magnets per beam line to extract the particles in one turn of the collider. Each magnet is powered by a dedicated pulse generator through special low impedance coaxial cables. The generator charging voltage is proportional to the beam momentum, which is 450 GeV/c at injection and will be 7 TeV/c at top energy. The current pulse has a maximum amplitude of 19 kA with a rise time of 2.8degs and a fall time of 2 ms; the first 89degs of the fall time are used to dump the beam. Each kicker magnet consists of a window frame of Si-Fe tape wound cores and high voltage insulated single turn conductors. They are built around a ceramic vacuum chamber which is metallized on the inside. The measures taken to ensure a high reliability of the system, which was one of the main considerations during the design, construction and testing of the system, are discussed. Results of measurements on the series systems are presented.

Studies of beam losses from failures of sps beam dump kickers

The SPS beam dump extraction process was studied in detail to investigate the possibility of operation with reduced kicker voltage and to fully understand the trajectories and loss patterns of miss-kicked beam. This paper briefly describes the SPS beam dump process, and presents the tracking studies carried out for failure cases. The simulation results are compared to the results of measurements made with low intensity beam.

Pulsed Power Applications in High Intensity Proton Rings

Pulsed power technology has been applied in particle accelerators and storage rings for over four decades. It is most commonly used in injection, extraction, beam manipulation, source, and focusing systems. These systems belong to the class of repetitive pulsed power. In this presentation, we review and discuss the history, present status, and future challenge of pulsed power applications in high intensity proton accelerators and storage rings.