The Multiwire Secondary Emission Monitor and the Emittance Measurement of the AGS Beam

Abstract

For CBA injection the transverse emittances and the Twiss parameters of the AGS beam have to be well defined to minimize the phase space dilution in CBA. Although there exists a profile monitor device at U165, there are three reasons why construction of a multiwire profile monitor system at three locations from U500 to U168 is required. 1) The dispersion function is not zero at U165 which makes it harder to interpret the measurement. 2) The original single wire device takes five minutes to traverse the whole beam. 3) A three station multiwire system can provide the profile information at all locations in one pulse which makes on-line analysis possible. In summary, a set of three stations of Multiwire Secondary Emission Monitor (MSEM) has been built and installed in the fast external beam line for the measurement of beam profiles. Each unit consists of two planes each with 30 nickel wires having a diameter of 5 mils. The signal is linear within the range of 1010 to 1013 incident protons on the wire and the resolution of the signal is well within a few percent. A least-square fitting routine has been used to extract the emittance and phase space parameters of the beam. The emittances obtained at various intensities will help us to understand the AGS acceleration process and to choose the optimal injection scheme for CBA.