In order to make efficient use of the available luminosity and to 
protect detector  components, detectors at the future linear collider 
must be kept tolerably free of  accelerator-related backgrounds. This 
requires the use of mechanical collimators  that intercept particles 
with large transverse amplitudes while transmitting the  core of the 
beam to the collision point. Since collimators must be placed very 
close  to the beam line to achieve the desired level of background 
suppression, the  wakefields induced in collimators by the passing beam 
act back on the beam particles  and cause them to deviate from their 
original trajectories, resulting in jitter  amplification and emittance 
dilution. This, in turn, reduces the luminosity,  increases detector 
backgrounds, and results in machine protection issues. The  ability to 
reliably predict and reduce collimator wakefields is therefore critical 
for optimizing the linear collider design.
 
We will describe the facility that has been built at SLAC Linac for 
precise measurements  of short-range transverse wakefields in 
collimators of various geometries and  materials, present preliminary 
results of measurements with the first three collimator sets, and 
compare the results with existing analytical models and  numerical 
simulations. Current status of the experiment and future plans will be  
discussed.