Author: Olvegaard, M.     [Olvegård, M.]
Paper Title Page
MOCL3 Emittance and Momentum Diagnostics for Beams with Large Momentum Spread 37
  • M. Olvegård, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  In the drive beam complex of CLIC, but also in plasma wakefield accelerators, the momentum spread can be on the order of tens of percent while conventional diagnostic methods often assume a very small momentum spread. This leads to systematic misinterpretations of the measurements. Spectrometry and emittance measurements based on quadrupole scan rely on measuring the beam size, which depends on the beam envelope. This, in turn, depends on the momentum distribution. We have studied the systematic errors that arise and developed novel algorithms to correctly analyze these measurements for arbitrary momentum distributions. As an application we consider the CLIC drive beam decelerator, where extraction of up to 90% of the kinetic energy leads to a very large momentum spread. We study a measurement of the time-resolved momentum distribution, based on sweeping the beam in a circular pattern and recording the beam size on a screen using optical transition radiation. We present the algorithm to extract the time-resolved momentum distribution, together with simulation results to prove its applicability.  
slides icon Slides MOCL3 [2.984 MB]  
MOPF30 Novel Diagnostics for Breakdown Studies 287
  • M. Jacewicz, Ch. Borgmann, M. Olvegård, R.J.M.Y. Ruber, V.G. Ziemann
    Uppsala University, Uppsala, Sweden
  • J.W. Kovermann
    CERN, Geneva, Switzerland
  The phenomenon that currently prevents achieving high accelerating gradients in high energy accelerators such as the CLIC linear collider is electrical breakdown at very high electrical field. The ongoing experimental work is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the discharges. The CLIC collaboration has commissioned a dedicated 12 GHz test-stand to validate the feasibility of accelerating structures and observe the characteristics of the RF discharges and their eroding effects on the structure. A versatile system for detection of the dark and breakdown currents and light emission is being developed for the test-stand. It consists of a collimation system with an external magnetic spectrometer for measurement of the spatial and energy distributions of the electrons emitted from the acceleration structure during a single RF pulse. These measurements can be correlated with e.g. the location of the breakdown inside the structure using information from the incident, reflected and transmitted RF powers giving a complete picture of the vacuum breakdown phenomenon.