CLASSE, Ithaca, New York, USA
LBNL, Berkeley, California, USA
The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA) with beam energies ranging from 2 GeV to 5 GeV. Measurements of electron cloud densities have been made using a number of techniques, including Shielded Pickups (SPU) and Resonant TE Waves. These measurements include different bunch configurations, from single bunches of positrons and electrons to multibunch trains. The comparison of those results, obtained in the same portion of the vacuum chamber, highlights the peculiarities of the two techniques and helps in identifying their advantages and disadvantages. In many respects, the techniques are complementary. For example, TE Wave measurements are most sensitive to cloud electrons near the horizontal center of the beampipe, while the SPU is sensitive to cloud electrons with velocities that are normal to the inner surface of the beampipe. SPU measurements show the time evolution of the cloud more directly, while the Resonant TE Wave measurements give a more direct absolute measurement of the overall cloud density. We present an outline of our present understanding of these two techniques and a comparison of recent measurements.
