Final Report DE-FG02-041353

Abstract

There were two major objectives of the work supported by this grant: 1) tests of a high voltage pulser for the ILC damping ring kickers; 2) ILC undulator based positron source tests and simulations.Damping Ring Kicker Pulser (04-05, 05-06) The ILC damping rings require kickers able to inject and extract bunches of approximately 3 ns spacing without disturbing neighboring bunches. In addition, the kickers must be able to operate in 3.25 MHz bursts with an average pulse rate of 14.1 kHz, driven by 10 kV pulsers. The work reported here focused on the pulser itself. Bench and beam tests of a commercial pulser built by FID Technology were carried out. The pulser, model FPG2-3000-MC2 has a nominal output of + and -1 kV with advertised rise and fall times and rep rate capability close to that needed by the ILC. Details of the specification derivation and the pulser tests can be found in the appended paper (THPCH148) which was published in the proceedings of EPAC2006, Figure 1 shows waveforms of the positive and negative 1.08 kV outputs measured with an oscilloscope Fig. 1 Waveform obtained from the FPG2-3000-MC2 pulser with 46 db attenuation. The waveform shown is for the first pulse in a burst and is the accumulation of several hundred sweeps, 1 ns per horizontal square.If we define the full width of the pulse to be the period between the 10% points we see that the pulse is about 5 ns, somewhat wider than desirable for use with bunch spacing of 3 ns and 1 ns long stripline kicker. A large portion of this width is due to the approximately 2.4 ns fall-time of the pulse. Since this will only impact the trailing "hot" bunch, it may be acceptable. A variation of 2% in amplitude over the pulses measured was recorded.As a further test of the performance of the pulser under accelerator operating conditions, it was used to drive an existing 2.1 ns long stripline kicker on the A0 photo-injector beamline at Fermilab. The kick delivered to a nominal 15 MeV beam was measured and simulated using a digitized recording of the waveforms above. The measured result is shown in Fig. 2 and agrees well with the simulation.While the measured parameters of the pulser approach that required by the ILC, issues remain: a unit operating at 10 kV must be demonstrated; amplitude stability must be improved by a factor of 2; a detailed characterization of the pulses throughout the train is required. Fig. 2 Beam kick obtained by scanning the pulser trigger relative to the beam arrival time taken at the A0 photo-injector.ILC Undulator Based Positron Source (06-07) After due consideration of positron sources based on electrons on a heavy metal target, inverse Compton effect, and high energy gamma rays on a relatively thin heavy metal target, the ILC Reference Design selected the undulator source as the baseline. Considerations of efficiency, and the possibility of creating polarized positrons, led to the choice of a superconducting, helical undulator approach.In the work supported by this grant, a design for modules comprising the full scale undulator ...