Measuring emittance growth due to magnetic bunching of an electron beam using the second moment of its image charge

Current thinking about the Next Linear Collider (NLC) places a great deal of importance on magnetic beam compression. However, theoretical work has predicted that a large emittance growth may occur during magnetic compression due to coherent synchrotron radiation and the non-inertial space-charge force. Applications such as the NLC cannot tolerate such beam degradation. To verify this prediction we have measured the emittance of the Sub-Picosecond Accelerator electron beam as a function of compression in our magnetic chicane and compared the results to numerical simulation. These emittance measurements were carried out using a pair of quadrupole magnets and a beam position monitor