Beam position monitors (BPM) are very important for optimization of beam characteristics and alignment in the TESLA Test Facility (TTF) linac. To achieve this goal stripline monitors were designed, built, tested and installed into the TTF linac in 1995 and 1996, with a design position resolution of about 100 micron around the center. The monitors consist of four 50 Ω coaxial striplines, positioned 90 degrees in azimuthal around the beam pipe.
The BPM body was machined from a single block of stainless steel, and four holes and the beam aperture were drilled. Each electrode is 175 mm long and shortened at the end; its geometric coupling factor is about 3 %. The signals are transmitted from the electrode into the cable by feedthrougs, selected for mechanical reasons.
The front end electronics originally designed and built for phase one of the TTF (low bunch charge (40pC) and high bunch repetition rate (216.7 MHz)) had been redesigned for phase two (high bunch charge (1 - 8 nC) and low repetition rate (1 MHz)) by colleagues from INFN, Frascati. The new design provides for single bunch response. Details on the electronics may be found in Castellano et al., EPAC 1996, 1633 and L. Cacciotti et al., TESLA Note 98-18.
Nine BPM's were installed into the TTF linac. Their resolution is better than 50 micron; they provide a linear response in the range of ± 5mm anf the relative gain error is within ± 10%. The stability of the stripline BPM reachings is good, allowing to detect beam position jitter. More details of the experience with this kind of BPM's in the TTF linac can be found in P. Castro et al., Proc. 4th European Workshop on Diagnostics and Instrumentation for Particle Accelerators, Chester, UK, May 16 - 18, 1999.