SLAC, Menlo Park, California
Stanford University, Stanford, Califormia
The LCLS accelerator produces a 14GeV beam with a normalized emittance on the order of one micron RMS, and peak current exceeding 1000 Amps. The design of the beam measurement system relied heavily on optical transition radiation profile monitors, in conjunction with transverse cavities, and conventional energy spectrometers. It has been found that the high peak currents, and small longitudinal phase space of the beam generate strong coherent optical emission that prevents the use of OTR or other prompt optical diagnostics, requiring the use of wire scanners or fluorescent screen based measurements. We present the results of the beam measurements, measurements of the coherent optical effects, and future plans for diagnostics.
SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) must deliver a high quality electron beam to the undulator. High resolution beam position monitoring is required to accomplish this task. Critical specifications are a dynamic range of 0.08-8.0 nC with a 5 microns resolution at 200 pC. New processor electronics was designed, processing is based on filtering the signals and direct digitization of the resulting pulse train. The processor consists of an Analog Front-End (AFE) and Analog-to-Digital Converter (ADC) boards, all are packed into 19-in rack mount chassis, 1U high. AFE board has a very low input noise, approximately 3 microV rms in a 7 MHz bandwidth centered at 140 or 200 MHz. The maximum gain is 34 dB with attenuation of up to 46 dB in 1 dB step. An on-board pulser sends the short CW burst to the striplines to perform between pulse calibration. The ADC board has four 16-bit digitizers, the sampling frequency is 120 MHz. The low-jitter clock is on a separate board in the same chassis. For the LCLS injector 22 prototypes of the processors were built and installed in 2007. Measured resolution at 200 pC is typically 3-5 microns. The 53 improved and modified processors are in production