Measurements of the transverse wakefields due to varying collimator characteristics

Abstract

We report on measurements of the transverse wakefields induced by collimators of differing characteristics. An apparatus allowing the insertion of different collimator jaws into the path of a beam was installed in End Station A (ESA) in SLAC. Eight comparable collimator geometries were designed, including one that would allow easy comparison with previous results, and were installed in this apparatus. Measurements of the beam kick due to the collimator wakefields were made with a beam energy of 28.5 GeV, and beam dimensions of 100 microns vertically and a range of 0.5 to 1.5 mm longitudinally. The trajectory of the beam upstream and downstream of the collimator test apparatus was determined from the outputs of ten BPMs (four upstream and six downstream), thus allowing a measurement of the angular kick imparted to the beam by the collimator under test. The transverse wakefield was inferred from the measured kick. The different aperture designs, data collection and analysis, and initial comparison to theoretical and analytic predictions are presented here.

Cavity BPM system tests for the ILC energy spectrometer

“…These systems are described in more detail below. Among other experimental setups, a collimator wakefield experiment is located downstream of the BPM 1 and 2 doublet and uses the BPM system for measuring wakefield kick angles [9].…”

GDFIDL simulations of non-linear tapers for ILC collimators

“…Such a collimator profile was built, and tested with a beam at at SLAC [8]. For this experiment it was known as Collimator 16.…”

Computations of wakefields in the ILC collimators

“…Improvements in GdfidL [3], and availability of time on a 54 node cluster [4] have allowed the refinement of the simulations, and results are available for comparison with other simulation codes. In addition, simulations have been carried out on the collimators tested in March 2007, which are described separately in these proceedings [5]. There are only five different geometries present in these more recent runs, the first of which was also tested last year.…”