Abstracts Brochure - CERN

TUPCH — Poster Session 27-Jun-06 16:00 - 18:00
Turn by Turn Measurements at DAFNE Based on the Libera Beam Position Processor
The BPM detection electronics developed by
Instrumentation Techonologies implements A. Stella, M. Serio (INFN/LNF)
digital receivers technology to measure beam
position from the amplitude of pick-up signals. Besides the closed orbit mode, the Libera module can be operated also
in the Turn-by-Turn mode. Operational experience with Libera at DAFNE, the Frascati e + e − collider, has been focused
on this functionality. Data obtained from DAFNE have been processed with well established extraction algorithms to
accurately measure the betatron tunes from a small number of turns, providing instantaneous information on tune
variations occurred also in fast damped decays after a kick. Hardware and software implementation together with
experimental data are reported.
Bunch Length Characterization Downstream from the Second Bunch Compressor at the
TTF VUV-FEL
The characterization of the longitudinal density
profile of picosecond and sub-picosec- E. Chiadroni (INFN-Roma II)
ond relativistic particle bunches is a fundamental
requirement in many particle accelerator facilities, since knowledge of the characteristics of the accelerated
beams is of utmost importance for the successful development of the next generation light sources and linear colliders.
The development of non-intercepting beam diagnostics is thus necessary to produce and control such beams. First
experimental evidences of the non-intercepting nature of diffraction radiation diagnostics are given. The longitudinal
bunch distribution downstream of the second bunch compressor of the DESY TTF VUV-FEL has been reconstructed
using a frequency-domain technique based on the autocorrelation of coherent diffraction radiation. Due to the low
and high frequency suppression, introduced by the experimental apparatus, only a portion of the CDR spectrum
participates to the reconstruction of the longitudinal bunch profile. The knowledge of the system frequency response
is then crucial in order to correct the results and extrapolate a bunch shape as close as possible to the real one.
Upgrade of Signal Processing of the BPM System at the SPring-8 Storage Ring
SPring-8 is a third generation synchrotron
light source, which is operated stably with T. Fujita, S. Sasaki, M. Shoji, T. Takashima (JASRI/SPring-8)
top-up mode and with optics of low emittance
mode. Along with stabilization of electron beam orbit in the ring, upgrading of the BPM system has also been
required. We have developed a new signal processing circuit for COD measurement with a target of a few microns
of position resolution at 1 kHz band-width and a few hundreds per second to take beam position of all BPMs. In the
new circuit, a multiplexing method is employed and the IF frequency is directory detected with a 2MSPS 16-bit ADC.
The digitized signal is processed with DSP to obtain beam position. Analog components of the circuit are equipped
in a temperature controlled cabinet in order not to be affected by fluctuation of ambient temperature. In this paper
we report schematics and performance of the new circuit, e.g., dependence of position resolution on measurement
band-width and long time stability, etc. In addition, we briefly describe possibility of fast orbit measurement as a
further application of the circuit.
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