Abstracts Brochure - CERN

TUPCH055
TUPCH056
TUPCH057
27-Jun-06 16:00 - 18:00 TUPCH — Poster Session
Beam Phase Measurement of Stored Bunch
We developed a system to measure synchro-
T. Ohshima, A. Yamashita (JASRI/SPring-8) M. Yoshioka (SES) nous phase angles for all bunches stored in
the storage ring using an oscilloscope with
high sampling rate. Precise phase measurement of specific bunch is required from the synchrotron radiation (SR)
users, especially from the time resolved spectroscopy users. In a pump and probe experiment, the trigger timing for
pumping laser should be precisely adjusted to the probe SR light. The timing of SR light is affected by the accelerating
RF voltages, filling pattern, bunch currents, gap positions of insertion devices and so on. At the SPring-8, the bunch
currents and the synchronous phase angles for all stored bunches can be measured within 30seconds using newly
developed system. The precision of the phase angle is less than 8ps. We are now preparing to deliver the information
of synchronous phase angle to SR users. The detail of the measurement system and achieved performance will be
presented.
A Simpler Method for SR Interferometer Calibration
J.W. Flanagan, H. Fukuma, S. Hiramatsu, H. Ikeda, T. Mitsuhashi
(KEK)
176
Previous methods of performing absolute
calibration of the SR interferometer used at
KEKB (measuring mirror distortion with a
pinhole mask, virtual beam broadening via
local bumps, physical beam broadening via dispersion bumps) are very time-consuming, and require dedicated machine
time to take the necessary data. We report on a new, simpler method we have developed, wherein we create
small local bumps at the SR source point and observe the resulting shifts in the phase of the interference fringes.
From these data we can calibrate the total magnification of the system, including the effects of mirror distortion. The
calibration data can be taken in a very small amount of time (tens of minutes), and in parallel with physics running,
without stopping the beam-size measurement system or interfering with its use for luminosity tuning. By taking
the calibration data at different beam currents and correlating the magnification at each current with the appropriate
interference pattern fit parameters, we can also obtain the parameters needed for real-time mirror distortion
correction.
A Diagnostic System for Beam Aborts at KEKB
H. Ikeda, K. Akai, J.W. Flanagan, T. Furuya, S. Hiramatsu, M.
Suetake, Y. Suetsugu, M. Tobiyama, T. Tsuboyama (KEK) S. Stanic
(Tsukuba University)
A controlled beam abort system has been
installed at KEKB for the protection of the
hardware components of the accelerator and
detector from damage by ampere-class beam
currents. In order to identify the reason for
each abort and optimize the abort system to handle each type of problem as well as improve machine operation, a
diagnostic system has been developed. Fast signals, such as beam currents, accelerating voltages of the RF cavities
and beam loss monitor signals from PIN photo-diodes are recorded and analyzed by a data logger system with a high
sampling rate at the moment of each abort. Beam oscillations, radiation dose at the detector and vacuum pressure
are also examined to classify the reasons for beam loss and aborts. Statistics and typical examples of these aborts will
be discussed.