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Y Honda,
K Kubo,
S Anderson,
S Araki,
K Bane,
A Brachmann,
J Frisch,
M Fukuda,
K Hasegawa,
H Hayano, [......],
N Toge, J Urakawa,
V Vogel,
M Woodley,
A Wolski,
I Yamazaki,
Yoshio Yamazaki,
G Yocky,
A Young,
F Zimmermann
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ABSTRACT: For high luminosity in electron-positron linear colliders, it is essential to generate low vertical emittance beams. We report on the smallest vertical emittance achieved in single-bunch-mode operation of the Accelerator Test Facility, which satisfies the requirement of the x-band linear collider. The emittances were measured with a laser-wire beam-profile monitor installed in the damping ring. The bunch length and the momentum spread of the beam were also recorded under the same conditions. The smallest vertical rms emittance measured at low intensity is 4 pm at a beam energy of 1.3 GeV, which corresponds to the normalized emittance of 1.0x1.0(-8) m. It increases by a factor of 1.5 for a bunch intensity of 10(10) electrons. The measured data agreed to the calculation of intrabeam scattering within much better than a factor of 2.
Physical Review Letters 03/2004; 92(5):054802. · 7.37 Impact Factor
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M Fukuda,
T Aoki,
K Dobashi,
T Hirose,
T Iimura,
Y Kurihara,
T Okugi,
T Omori,
I Sakai, J Urakawa,
M Washio
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ABSTRACT: We have developed a polarimetry of ultrashort pulse gamma rays based on the fact that gamma rays penetrating in the forward direction through a magnetized iron carry information on the helicity of the original gamma rays. Polarized, short-pulse gamma rays of (1.1+/-0.2)x10(6)/bunch with a time duration of 31 ps and a maximum energy of 55.9 MeV were produced via Compton scattering of a circularly polarized laser beam of 532 nm off an electron beam of 1.28 GeV. The first demonstration of asymmetry measurements of short-pulse gamma rays was conducted using longitudinally magnetized iron of 15 cm length. It is found that the gamma-ray intensity is in good agreement with the simulated value of 1.0x10(6). Varying the degree of laser polarization, the asymmetry for 100% laser polarization was derived to be (1.29+/-0.12)%, which is also consistent with the expected value of 1.3%.
Physical Review Letters 11/2003; 91(16):164801. · 7.37 Impact Factor
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V Yakimenko,
I V Pogorelsky,
I V Pavlishin,
I Ben-Zvi,
K Kusche,
Yu Eidelman,
T Hirose,
T Kumita,
Y Kamiya, J Urakawa,
B Greenberg,
A Zigler
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ABSTRACT: We describe our studies of the generation of plasma wake fields by a relativistic electron bunch and of phasing between the longitudinal and transverse fields in the wake. The leading edge of the electron bunch excites a high-amplitude plasma wake inside the overdense plasma column, and the acceleration and focusing wake fields are probed by the bunch tail. By monitoring the dependence of the acceleration upon the plasma's density, we approached the beam-matching condition and achieved an energy gain of 0.6 MeV over the 17 mm plasma length, corresponding to an average acceleration gradient of 35 MeV/m. Wake-induced modulation in energy and angular divergence of the electron bunch are mapped within a wide range of plasma density. We confirm a theoretical prediction about the phase offset between the accelerating and focusing components of plasma wake.
Physical Review Letters 08/2003; 91(1):014802. · 7.37 Impact Factor
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Y. Fukui,
D.B. Cline,
F. Zhou,
M. Ross,
P. Bolton, J. Urakawa,
M. Tobiyama,
R. Hamatsu,
T. Muto,
P.V. Karataev,
A.P. Potylitsyn,
G.A. Naumenko,
A.S. Aryshev
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ABSTRACT: We design a single bunch transverse beam size monitor which will be tested to measure the 28.5 GeV electron/positron beam at the SLAC FFTB beam line. The beam size monitor uses the CCD images of the interference pattern of the optical diffraction radiation from two slit edges which are placed close to the beam path. In this method, destruction of the accelerated electron/positron beam bunches due to the beam size monitoring is negligible, which is vital to the operation of the Linear Collider project.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: Linear collider (LC) interaction region beam sizes and component position stability requirements are expected to be a few nanometers. It is important to show that the related tolerances can be achieved, with an electron beam if possible. Using recently developed component stabilization technology, very high-resolution beam position monitors (BPM's), and the ultra-low emittance beam at the KEK ATF, we plan to demonstrate the required stabilization. Our first step is to develop high-resolution RF cavity beam position monitors, using either C or X band frequencies. A C-band cavity BPM with a resolution of 25 nm has been reported in tests at FFTB. By correcting for the effects of nonaxial trajectories and using both position and angle BPM movers, we expect to be able to demonstrate a resolution of 2 to 3 nm over a dynamic range of ± 20 um. We report on the progress of the tests here.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: An experiment to investigate the diffraction radiation from a single edge target has been performed at the accelerator test facility of KEK with the aim of developing noninvasive beam diagnostics. The yield and the angular distribution of diffraction radiation as a function of the impact parameter was measured in the visible light region. The distributions were qualitatively consistent with the theoretical expectation. This work exhibits the first observation of the incoherent diffraction radiation in the visible light region.
Physical Review Letters 04/2003; 90(10):104801. · 7.37 Impact Factor
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K Kubo,
M Akemoto,
S Anderson,
T Aoki,
S Araki,
K L F Bane,
P Blum,
J Corlett,
K Dobashi,
P Emma, [......],
Seishi Takeda,
N Terunuma,
N Toge,
J Turner, J Urakawa,
V Vogel,
M Woodley,
J Yocky,
A Young,
F Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.
Physical Review Letters 06/2002; 88(19):194801. · 7.37 Impact Factor
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ABSTRACT: We derive a simple relation for estimating the relative emittance growth in x and y due to intrabeam scattering (IBS) in electron storage rings. We show that IBS calculations for the ATF damping ring, when using the formalism of Bjorken-Mtingwa, a modified formalism of Piwinski (where eta squared divided by beta has been replaced by the dispersion invariant), or a simple high-energy approximate formula all give results that agree well. Comparing theory, including the effect of potential well bunch lengthening, with a complete set of ATF steady-state beam size vs. current measurements we find reasonably good agreement for energy spread and horizontal emittance. The measured vertical emittance, however, is larger than theory in both offset (zero current emittance) and slope (emittance change with current). The slope error indicates measurement error and/or additional current-dependent physics at the ATF; the offset error, that the assumed Coulomb log is correct to within a factor of 1.75. Comment: 17 pages, 6 figures, .bbl file
06/2002;
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ABSTRACT: 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).
07/2001;
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ABSTRACT: 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.
06/2001;
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I. V. Pogorelsky,
I. Ben-Zvi,
T. Hirose,
S. Kashiwagi,
K. Kusche,
T. Kumita,
T. Omori,
V. Yakimenko,
K. Yokoya, J. Urakawa,
M. Washio
[show abstract]
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ABSTRACT: The counter-propagating picosecond CO2 laser pulse and picosecond or femtosecond electron bunch produced by the photocathode linac shape the optimum configuration for the ultra-bright relativistic Thomson scattering x-ray source. Using these components, a proof-of-principle experiment at the ATF reached the x-ray photon yield of 8×106 measured in the 1.8–2.3 Å window per 3.5 ps pulse. Upon completion of the ongoing upgrade of the ATF laser and linac, 300 fs x-ray pulses with intensity of 5×1022 photon/second will be obtained. This will provide also an opportunity for fundamental study of the nonlinear Thomson scattering at the laser strength parameter close to 1. Finally, we discuss the feasibility of a high repetition rate Thomson source and how plasma channels facilitate this design. © 2001 American Institute of Physics.
AIP Conference Proceedings. 05/2001; 569(1):571-582.
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ABSTRACT: An 1.6 cell rf-gun system has been installed at Waseda University
for the generation of high charge, short pulse and low emittance
electron beam. The gun is one of essential components for X-ray
generation using inverse Compton scattering between a photo electron
bunch and laser pulse. An all-solid-state picosecond Nd:YLF laser system
has been installed at Waseda University and will be used not only for
photo electron generation in the rf-gun but also for collision with the
photo electron bunch. The laser system has the frequency conversion
section, which is operated to produce the UV (262 nm) using BBO crystals
from the amplified fundamental (1047 nm). An extremely stable laser
system is required for the generation of a high quality electron beam,
and the system is the essential component for the generation of X-rays
through inverse Compton scattering. Timing and intensity stabilities of
the laser pulse have been measured using time domain demodulation
technique. As results a timing stability of 0.26 ps against the local
oscillator of rf and an intensity stability of 0.11% have been achieved.
We have carried out a numerical simulation to calculate the number of
photons and the energies of X-rays by changing the crossing angles
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: We have conducted the research project named "High-Tech Research
Center Project" at Waseda University, which is supported by the Ministry
of Education, Culture, Sports, Science and Technology. In this project,
a laser photocathode rf-gun with 1.6 acceleration cells with Mg cathode
has been installed for production of a low emittance and short bunched
electron beam. The main parts of the rf source for the rf-gun consists
of a 10 MW s-band klystron and a small pulse modulator. The pulse
modulator has good stability and flatness of the output pulse. The
amplitude jitter of klystron voltage was realized down to 0.38% (p-p)
for 20000 pulses and the pulse flatness down to 0.25% (within >1.5
μs pulse flat-top). A high quality electron beam is very powerful
tool for the study of radiation physics, radiation chemistry, material
science, etc. The development of short X-ray pulse generation by the
inverse Compton scattering between a high quality electron beam and
laser light, will be started in the 2001 fiscal year. The system will be
applied to pulse radiolysis experiments for studies on radiation physics
and chemistry
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: In future e<sup>+</sup>e<sup>-</sup> linear colliders, such as the
JLC/NLC, damping rings are needed to generate beams of intense bunches
with very low emittances. The Accelerator Test Facility (ATF) at KEK is
a prototype for such damping rings. In April 2000 the single bunch
energy spread, bunch length, and horizontal and vertical emittances of
the beam in the ATF were all measured as functions of current, and all
exhibited significant growth. We want to know if the results agree with
intrabeam scattering (IBS) theory
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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[show abstract]
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ABSTRACT: In April 2000 the single bunch energy spread, bunch length, horizontal emittance, and vertical emittance were measured as functions of current in KEK's ATF damping ring. In this report the measurement results are analyzed in light of intrabeam scattering theory. The measurements are found to be relatively consistent with theory, although the measured effects appear to be stronger than theory. In addition, the factor of 3 growth in vertical emittance at a current of 3 mA does not seem to be supported.
01/2001;
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ABSTRACT: This report presents bunch length and energy spread measurements performed in April 2000 at the ATF Damping Ring, at KEK. Measurements were performed with the beam on and then off the linear (difference) coupling resonance. Due to strong intra-beam scattering in the ATF ring, the results depended strongly on the coupling.
11/2000;
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ABSTRACT: A double kicker system which extracts the ultra-low emittance multi-bunch beam stably from ATF damping ring was developed. The performance of the system was studied comparing an orbit jitter with single kicker extraction in single bunch mode. The position jitter reduction was estimated from the analysis of the extraction orbits. The reduction was confirmed for the double kicker system within a resolution of BPMs. More precise tuning of the system with a wire scanner has been tried by changing a beta function at the second kicker to get more reduction of kick angle jitter. The results of these studies are described in detail.
09/2000;
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ABSTRACT: The rf distribution system for the linear collider requires stable x-band(11.424GHz) rf phase signal over 25km length. In order to realize the distribution system, a fiber optic link using a phase stabilized optical fiber was tested. The phase stabilized optical fiber has been employed at LEP, KEKB, etc.. This paper describes the hardware system and result of the preliminary test of the feed back system for stabilization of the phase change.
09/2000;
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T. Hirose,
T. Okugi,
Y. Takayama,
H. Hayano,
S. Kamada,
K. Kubo,
T. Naito, J. Urakawa,
S. Kashiwagi,
M. Takano,
M. Minty,
J. Turner,
M. Woodley,
F. Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: We applied three methods in order to measure the vertical
emittance of KEK-ATF. The first is a SR interferometer, the second
method is the emittance measurement by using wire scanners at the beam
extraction line. The last method is emittance estimation by measuring an
intensity dependence of a momentum spread, which is caused by the
intra-beam scattering. The measured vertical emittance for KEK-ATF is
0.02-0.06 nm, which is a few times larger than the design target of
KEK-ATF
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
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A. Tsunemi,
A. Endo,
I. Pogorelsky,
I. Ben-Zvi,
K. Kusche,
J. Skaritka,
V. Yakimenko,
T. Hirose, J. Urakawa,
T. Omori,
M. Washio,
Y. Liu,
P. He,
D. Cline
[show abstract]
[hide abstract]
ABSTRACT: Laser-Compton scattering with picosecond CO<sub>2</sub> laser
pulses is proposed for generation of high-brightness X-rays. The
interaction chamber has been developed and the experiment is scheduled
for the generation of the X-rays of 4.7 keV, 10<sup>7</sup> photons in
10-ps pulse width using 50-MeV, 0.5-nC relativistic electron bunches and
6 GW CO<sub>2</sub> laser
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
