Abstracts Brochure - CERN

TUPCH090
TUPCH092
TUPCH093
27-Jun-06 16:00 - 18:00 TUPCH — Poster Session
Electron Beam Profile Measurements with Visible and X-ray Synchrotron Radiation at the
Swiss Light Source
Å. Andersson, M. Rohrer, V. Schlott, A. Streun (PSI) O.V. Chubar
(SOLEIL)
186
Two different methods of beam profile measurements
using a) visible-to-UV range synchrotron
radiation b) X-ray synchrotron radiation
have been realized in a single diag-
nostics beam line at the Swiss Light Source. While the visible-to-UV part uses a focusing lens to create an image
of the electron beam cross section, the X-ray part makes use of the pinhole camera principle. In the visible-to-UV
case the vertically polarized synchrotron radiation renders an image heavily influenced by inherent emission and
diffraction effects of synchrotron radiation. This turns out to be an advantageous influence in order to determine
ultra small beam profiles. For each of the two methods practical point-spread function measurements, including
all beam line components, and high-precision wave-optics based calculations (SRW code) of the synchrotron light
characteristics were performed to ensure correct interpretation of the measured profiles. Results from both monitors
will be presented to allow comparison.
Commissioning of a New Digital BPM System for the PSI Proton Accelerators
A new digital beam position monitor
B. Keil, P.-A. Duperrex, M. U. Müller (PSI)
(DBPM) system has been developed and successfully
tested at the PSI proton accelerators.
The DBPM hardware consists of an analogue RF front-end (RFFE), a VMEbus backplane module (VBM), and the PSI
VME PMC Carrier board (VPC). The RFFE combines the 2nd RF harmonic (101.26 MHz) beam signals of pickup
coils with a 101.31 MHz pilot signal. The RFFE output signals are undersampled and down-converted to base-band
(no analogue mixer) by ADCs and DDCs (Direct Digital Downconverters) on the VBM. The DDCs send the digitised
beam and pilot signal amplitudes to a Virtex2Pro FPGA on the VPC board. The FPGA calculates the beam positions
at different averaging rates, checks interlock limits, and provides triggered storage of beam position waveforms.
Furthermore, the FPGA performs automatic gain control of voltage-controlled amplifiers (VCAs) of RFFE and VBM.
By continuous normalisation of beam to pilot signal, nonlinearities and temperature drifts of the electronics are
eliminated. Compared to the old analogue BPM electronics, the new DBPMs offer an increased dynamic range (0.2
µA to 2 mA instead of 5 µA to 2 mA) and larger bandwidth (10 kHz instead of 10 Hz).
Residual Gas Photon Beam Position Monitor for the Swiss Light Source
The extensive use of photon beam position
V. Schlott, C. Brönnimann, M. Dehler, P. Kramer, B. Schmitt (PSI) monitors (PBPM) will open new possibilities
in achieving even higher levels of beam stability
at synchrotron light sources. To overcome the well known ambiguities in interpreting position readings from
conventional blade-type PBPMs, a new monitor type based on a residual gas cell is under design at the Swiss Light
Source (SLS). When the photon beam from an insertion device is passing the monitor, the residual gas is ionized and
the ions are deflected by a static electrical field onto the so called Mythen strip detector (micro-strip system for time
resolved experiments) at the ground level of the monitor. In this way, not only the photon beam position but also
the profile can be read out as a histogram with 50 µm pitch. The design of the new residual gas PBPM and first test
measurements in the SLS Diagnostics beam line are presented in this paper.