136 research outputs found
Impedance Analysis of Bunch Length Measurements at the ATF Damping Ring
We present energy spread and bunch length measurements at the Accelerator
Test Facility (ATF) at KEK, as functions of current, for different ring rf
voltages, and with the beam both on and off the coupling resonance. We fit the
on-coupling bunch shapes to those of an impedance model consisting of a
resistor and an inductor connected in series. We find that the fits are
reasonably good, but that the resulting impedance is unexpectedly large.Comment: 9 pages, 5 figures, presented at 10th International Symposium on
Applied Electromagnetics and Mechanics (ISEM2001
Intrabeam Scattering Analysis of ATF Beam Measurements
At the Accelerator Test Facility (ATF) at KEK intrabeam scattering (IBS) is a
strong effect for an electron machine. It is an effect that couples all
dimensions of the beam, and in April 2000, over a short period of time, all
dimensions were measured as functions of current. In this report we derive a
simple relation for the growth rates of emittances due to IBS. We apply the
theories of Bjorken-Mtingwa, Piwinski, and a formula due to Raubenheimer to the
ATF parameters, and find that the results all agree (if in Piwinski's formalism
we replace the dispersion squared over beta by the dispersion invariant).
Finally, we compare theory, including the effect of potential well bunch
lengthening, with the April 2000 measurements, and find reasonably good
agreement in the energy spread and horizontal emittance dependence on current.
The vertical emittance measurement, however, implies that either: there is
error in the measurement (equivalent to an introduction of 0.6% x-y coupling
error), or the effect of intrabeam scattering is stronger than predicted (35%
stronger in growth rates).Comment: 4 pages, 3 figures, Presented at IEEE Particle Accelerator Conferenc
Measurement of Resonance driving terms in the ATF Damping Ring
The measurement of resonance driving terms in the Damping Ring of the Accelerator Test Facility in KEK could help finding possible machine imperfections and even to optimize single particle stability through the minimization of non-linearities. The first experimental attempts of this enterprise are reported in this note
Photon generation by laser-Compton scattering at the KEK-ATF
We performed a photon generation experiment by laser-Compton scattering at
the KEK-ATF, aiming to develop a Compton based polarized positron source for
linear colliders. In the experiment, laser pulses with a 357 MHz repetition
rate were accumulated and their power was enhanced by up to 250 times in the
Fabry-Perot optical resonant cavity. We succeeded in synchronizing the laser
pulses and colliding them with the 1.3 GeV electron beam in the ATF ring while
maintaining the laser pulse accumulation in the cavity. As a result, we
observed 26.0 +/- 0.1 photons per electron-laser pulse crossing, which
corresponds to a yield of 10^8 photons in a second.Comment: 3 pages, 5 figures, Preprint submitted to TIPP09 Proceedings in NIM
A sub-micron resolution, bunch-by-bunch beam trajectory feedback system and its application to reducing wakefield effects in single-pass beamlines
A high-precision intra-bunch-train beam orbit feedback correction system has
been developed and tested in the ATF2 beamline of the Accelerator Test Facility
at the High Energy Accelerator Research Organization in Japan. The system uses
the vertical position of the bunch measured at two beam position monitors
(BPMs) to calculate a pair of kicks which are applied to the next bunch using
two upstream kickers, thereby correcting both the vertical position and
trajectory angle. Using trains of two electron bunches separated in time by
187.6~ns, the system was optimised so as to stabilize the beam offset at the
feedback BPMs to better than 350~nm, yielding a local trajectory angle
correction to within 250~nrad. The quality of the correction was verified using
three downstream witness BPMs and the results were found to be in agreement
with the predictions of a linear lattice model used to propagate the beam
trajectory from the feedback region. This same model predicts a corrected beam
jitter of c.~1~nm at the focal point of the accelerator. Measurements with a
beam size monitor at this location demonstrate that reducing the trajectory
jitter of the beam by a factor of 4 also reduces the increase in the measured
beam size as a function of beam charge by a factor of c.~1.6.Comment: 16 pages, 10 figure
Nanometer Order of Stabilization for Precision Beam Size Monitor (Shintake Monitor)
Original publication available at http://www.jacow.org/International audienceA precision beam size monitor using interference fringes as a reference called Shintake monitor[1] has been developed. Relative position between the beam and the interference fringes should be stabilized within few nm to measure the beam size of 37 nm with resolution of better than 10%. This paper presents concept and performances for stabilization of the Shintake monitor with respect to vibrations. We stabilized the table for the interferometer using a method, "Rigid mount on floor", and the table motions relative to the floor are estimated to be 2 and 6 n
- …