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J. Seeman,
R. Akre,
P. Bellomo,
Kirk J. Bertsche,
Y. Chai,
R. Chestnut, J. Clendenin,
S. DeBarger,
F.J. Decker,
J. Dorfan S. Ecklund, [......],
Y. Yan,
G. Yocky,
M. Zurawel,
W. Barry,
J. Corlett,
T. Elioff,
M. Furman,
M. Zisman,
M. Biagini,
P. Raimondi
ICFA Beam Dynamics Newsletter. 04/2009; 48:72.
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[show abstract]
[hide abstract]
ABSTRACT: A train of 1.3-ns micro bunches of longitudinally polarized electrons are generated in a 140-kV DC-gun based injector in the International Linear Collider electron source; a bunching system with extremely high bunching efficiency to compress the micro-bunch down to 20 ps FWHM is designed. Complete optics to transport the electron bunch to the entrance of the 5-GeV damping ring injection line is developed. Start-to-end multi-particle tracking through the beamline is performed including the bunching system, pre-acceleration, vertical chicane, 5- GeV superconducting booster linac, spin rotators and energy compressor. With optimizations of energy compression, 94% of the electrons from the DC-gun are captured within the damping ring 6-D acceptance - A<sub>x</sub> + A<sub>y</sub> les 0.09 m and DeltaEtimesDeltaz les (plusmn25 MeV) times (plusmn3.46 cm) - at the entrance of the damping ring injection line.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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[show abstract]
[hide abstract]
ABSTRACT: An RF polarized electron gun utilizing the unique features of an integrated, plane-wave-transformer (PWT) photoelectron injector is being developed by DULY Research Inc. in collaboration with SLAC. Modifications to a DULY S-band device include: a re-design of the photocathode/RF backplane interface to accommodate a GaAs cathode; change in the design of the vacuum ports to provide 10<sup>-11</sup> Torr operation; the inclusion of a load-lock photocathode replacement system to allow for reactivation and cesiation of the GaAs photocathode in a vacuum; and alteration of the magnet field coils to make room for the load-lock. The use of a stainless steel outer tank and cooling rods without copper plating may also provide better vacuum performance at the expense of diminished Q-factor. The effectiveness of both the standard cooling rods and synthetic diamond heat sinks for disk cooling is investigated for future linear collider applications operating at a rep rate of 180 Hz and a bunch charge of 2 nC.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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T. B. Humensky,
R. Alley,
A. Brachmann,
M. J. Browne,
G D Cates, J. Clendenin,
J. deLamare,
J Frisch,
T. Galetto,
E. W. Hughes,
K S Kumar,
P. Mastromarino,
J. Sodja,
P. A. Souder,
J Turner,
M Woods
[show abstract]
[hide abstract]
ABSTRACT: SLAC E-158 is an experiment designed to make the first measurement of parity violation in Moller scattering. E-158 will measure the right-left cross-section asymmetry, A_LR^Moller, in the elastic scattering of a 45-GeV polarized electron beam off unpolarized electrons in a liquid hydrogen target. E-158 plans to measure the expected Standard Model asymmetry of ~10^-7 to an accuracy of better than 10^-8. To make this measurement, the polarized electron source requires for operation an intense circularly polarized laser beam and the ability to quickly switch between right- and left-helicity polarization states with minimal right-left helicity-correlated asymmetries in the resulting beam parameters (intensity, position, angle, spot size, and energy), ^beam A_LR's. This laser beam is produced by a unique SLAC-designed flashlamp-pumped Ti:Sapphire laser and is propagated through a carefully designed set of polarization optics. We analyze the transport of nearly circularly polarized light through the optical system and identify several mechanisms that generate ^beam A_LR's. We show that the dominant effects depend linearly on particular polarization phase shifts in the optical system. We present the laser system design and a discussion of the suppression and control of ^beam A_LR's. We also present results on beam performance from engineering and physics runs for E-158. Comment: 64 pages, 28 figures. Submitted to Nuclear Instruments and Methods A
09/2002;
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[show abstract]
[hide abstract]
ABSTRACT: The PEP-II e+e- collider has been operating for two years with the BaBar
detector at the energy of the Upsilon 4S resonance. The peak luminosity
has reached 3.3 x1033/cm2/s with 693 bunches with
a positron current of 1.5 A and an electron current of 0.8 A. PEP-II has
delivered in excess of 38 fb(sub-1) of data to BaBar. The beam-beam tune
shift limits are approaching 0.05-0.07 horizontally and 0.03-0.05
vertically. The electron cloud instability ECI enlarges the positron
beam size at high currents but is reduced by a solenoidal field on the
vacuum chambers. The beam currents in PEP-II are being raised to
increase the number of bunches and the luminosity. Over the next few
years the luminosity goal for PEP-II is 10
34/cm2/s.
NASA STI/Recon Technical Report N. 07/2002; 2:91915.
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P. Mastromarino,
T.B. Humensky,
P. Anthony,
C. Arroyo,
K. Bega,
A. Brachmann,
G. Cates, J. Clendenin,
F.-J. Decker,
T. Fieguth,
E. Hughes,
G.M. Jones,
Y. Kolomensky,
K. Kumar,
D. Relyea,
S. Rock,
O. Saxton,
Z. Szalata,
J. Turner,
M. Woods
[show abstract]
[hide abstract]
ABSTRACT: Experiment E158 at the Stanford Linear Accelerator Center (SLAC) will make the first measurement of parity violation in Moller scattering. The left-right cross-section asymmetry in the elastic scattering of a 45-GeV polarized electron beam with unpolarized electrons in a liquid hydrogen target will be measured to an accuracy of better than 10<sup>-8</sup>, with the expected Standard Model asymmetry being approximately 10<sup>-7</sup>. Because helicity-correlated (left-right) charge and position asymmetries in the electron beam can give rise to systematic errors in the measurement, great care must be given to beam monitoring and control. We have developed beam current monitors that measure the charge per pulse at the 3 × 10<sup>-5</sup> level and RF cavity beam position monitors that measure the position per pulse to 1 μm, which should allow precisions of 1 ppb and 1 nm for the final integrated charge and position asymmetries, respectively. In addition, since most helicity-correlated systematics in the electron beam can be traced back to the laser that drives the photoemission from the GaAs source cathode, we first use careful control of laser beam polarization, point-to-point imaging, and other techniques to minimize systematics. We also provide the capability of modulating in a helicity-correlated way the laser beam's intensity and position as it strikes the photocathode, allowing the implementation of active feedbacks to ensure that the average charge and position asymmetries integrate close to zero over the course of the experiment. We present this system of precision beam monitoring and control and report on its performance during a recent commissioning run, T-437 at SLAC, which demonstrated charge and position asymmetry precisions of 12 ppb and 2 nm, respectively.
IEEE Transactions on Nuclear Science 07/2002; · 1.45 Impact Factor
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Y. Cai, J. Clendenin,
F.J. Decker,
M. Donald,
S. Ecklund,
R. Erickson,
A. Fisher,
S. Heifets,
R. Holtzapple,
R. Iverson, [......],
I. Reichel,
J.T. Seeman,
M. Stanek,
M. Sullivan,
J. Turner,
U. Wienands,
C. Steier,
M. Zisman,
M. Biagini,
W. Kozanecki
[show abstract]
[hide abstract]
ABSTRACT: The PEP-II e<sup>+</sup>e<sup>-</sup> collider has been operating
for two years with the BaBar detector at the energy of the Upsilon 4S
resonance. The peak luminosity has reached 3.3 ×
10<sup>33</sup>/cm<sup>2</sup>/s with 693 bunches with a positron
current of 1.5 A and an electron current of 0.8 A. PEP-II has delivered
in excess of 38 fb<sup>-1</sup> of data to BaBar. The beam-beam tune
shift limits are approaching 0.05-0.07 horizontally and 0.03-0.05
vertically. The electron cloud instability enlarges the positron beam
size at high currents but is reduced by a solenoidal field on the vacuum
chambers. The beam currents in PEP-II are being raised to increase the
number of bunches and the luminosity. Over the next few years the
luminosity goal for PEP-II is 10<sup>34</sup>/cm<sup>2</sup>/s
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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R. Alley,
V. Bharadwaj, J. Clendenin,
P. Emma,
A Fisher,
J Frisch,
T. Kotseroglou,
D.T. Palmer,
J. Schmerge,
M. Woodley,
A D Yeremian,
J. Rosenzweig,
D. D. Meyerhofer,
L. Serafini
[show abstract]
[hide abstract]
ABSTRACT: We report on the design of the rf photoinjector of the Linac Coherent Light Source (LCLS). The rf photoinjector is required to produce a single 150 MeV bunch of ~1 nC and ~100 A peak current at a repetition rate of 120 Hz with a normalized rms transverse emittance of ~1 p mm-mrad. The design employs a 1.6-cell S-band rf gun with an optical spot size at the cathode of a radius of ~1 mm and a pulse duration with an rms sigma of ~3 ps. The peak rf field at the cathode is 150 MV/m with extraction 57 o ahead of the rf peak. A solenoidal field near the cathode allows the compensation of the initial emittance growth by the end of the injection linac. Spatial and temporal shaping of the laser pulse striking the cathode will reduce the compensated emittance even further. Also, to minimize the contribution of the thermal emittance from the cathode surface, while at the same time optimizing the quantum efficiency (QE), the laser wavelength for a Cu cathode should be tunable around 260 nm. Follo...
03/1999;
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U. Wienands,
S. Anderson,
R. Assmannt,
V. Bharadwaj,
Y. Cai, J. Clendenin,
P. Corredoura,
F.J. Decker,
M. Donald,
S. Ecklund, [......],
R. Rimmer,
A. Zholents,
M. Zisman,
W. Kozanecki,
A. Hofmann,
B. Zotter,
C. Steier,
W. Bialowons,
M. Lomperski,
A. Lumpkin
[show abstract]
[hide abstract]
ABSTRACT: The PEP-II High Energy Ring (HER), a 9 GeV electron storage ring,
has been in commissioning since spring 1997. Initial beam commissioning
activities focused on systems checkout and commissioning and on
determining the behaviour of the machine systems at high beam currents,
This phase culminated with the accumulation of 0.75 A of stored
beam-sufficient to achieve design luminosity-in January 1998 after 3.5
months of beam time. Collisions with the 3 GeV positron beam of the Low
Energy Ring (LER) were achieved in Summer of 1998. At high beam
currents, collective instabilities have been seen. Since then,
commissioning activities for the HER have shifted in focus towards
characterization of the machine and a rigorous program to understand the
machine and the beam dynamics is presently underway
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
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K. Abe,
T. Akagi,
P. L. Anthony,
R. Antonov,
R. G. Arnold,
T. Averett,
H. R. Band,
J. M. Bauer,
H. Borel,
P. E. Bosted, [......],
D. Walz,
F. Wesselmann,
J. L. White,
K. Witte,
C. C. Young,
B. Youngman,
H. Yuta,
G. Zapalac,
B. Zihlmann,
D. Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: Measurements are reported of the proton and deuteron spin structure functions g1p and g1d at beam energies of 29.1, 16.2, and 9.7 GeV, and g2p and g2d at a beam energy of 29.1 GeV. The integrals Γp=∫01g1p(x,Q2)dx and Γd=∫01g1d(x,Q2)dx were evaluated at fixed Q2=3(GeV/c)2 using the full data set to yield Γp=0.132±0.003(stat)±0.009(syst) and Γd=0.047±0.003±0.006. The Q2 dependence of the ratio g1/F1 was studied and found to be small for Q2>1(GeV/c)2. Within experimental precision the g2 data are well described by the twist-2 contribution, g2WW. Twist-3 matrix elements were extracted and compared to theoretical predictions. The asymmetry A2 was measured and found to be significantly smaller than the positivity limit √R for both proton and deuteron targets. A2p is found to be positive and inconsistent with zero. Measurements of g1 in the resonance region show strong variations with x and Q2, consistent with resonant amplitudes extracted from unpolarized data. These data allow us to study the Q2 dependence of the integrals Γp and Γn below the scaling region.
Phys. Rev. D. 10/1998; 58(11).
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Slac Gun Test,
P. Sez,
R. Alley, J. Clendenin,
J Frisch,
R Kirby,
R. Mair,
T Maruyama,
R Miller,
G. Mulhollan,
C Prescott,
H Tang,
K Witte
[show abstract]
[hide abstract]
ABSTRACT: The SLAC Gun Test Laboratory apparatus, the first two meters of which is a replica of the SLAC injector, is used to study the production of intense, highly--polarized electron beams required for the Stanford Linear Collider and future linear colliders. The facility has been upgraded with a Mott polarimeter in order to characterize the electron polarization from photocathodes operating in a DC gun. In particular, SLAC utilizes p-type, biaxially-strained GaAs photocathodes which have produced longitudinal electron polarizations greater than 80% while yielding pulses of 5 A/cm 2 at an operating voltage of 120 kV. Among the experiments performed include studying the influences of the active layer thickness, temperature, quantum efficiency and cesiation on the polarization. The results might help to develop strained photocathodes with higher polarization. I. INTRODUCTION The Stanford Linear Accelerator Center (SLAC) conducts experiments in high-energy physics to study the structure of e...
04/1998;
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[show abstract]
[hide abstract]
ABSTRACT: The Linac Coherent Light Source (LCLS) at SLAC is being designed
to produce intense, coherent 0.15-nm X-rays. These X-rays will be
produced by a single pass of a 15 GeV bunched electron beam through a
long undulator. Nominally, the bunches have a charge of 1 nC, normalized
transverse emittances of less than 1.5π mm-mr and an rms bunch length
of 20 μm. The electron beam will be produced using the last third of
the SLAC 3-km linac in a manner compatible with simultaneous operation
of the remainder of the linac for PEP-II. The linac design necessary to
produce an electron beam with the required brightness for LCLS is
discussed, and the specific linac modifications are described
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
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P. Saez,
R. Alley, J. Clendenin,
J. Frisch,
R. Kirby,
R. Mair,
T. Maruyama,
R. Miller,
G. Mulhollan,
G. Prescott,
H. Tang,
K. Witte
[show abstract]
[hide abstract]
ABSTRACT: The SLAC Gun Test Laboratory apparatus, the first two meters of
which is a replica of the SLAC injector, is used to study the production
of intense, highly-polarized electron beams required for the Stanford
Linear Collider and future linear colliders. The facility has been
upgraded with a Mott polarimeter in order to characterize the electron
polarization from photocathodes operating in a DC gun. In particular,
SLAC utilizes p-type, biaxially-strained GaAs photocathodes which have
produced longitudinal electron polarizations greater than 80% while
yielding pulses of 5 A/cm<sup>2</sup> at an operating voltage of 120 kV.
Among the experiments performed include studying the influences of the
active layer thickness, temperature, quantum efficiency and cesiation on
the polarization. The results might help to develop strained
photocathodes with higher polarization
Particle Accelerator Conference, 1995., Proceedings of the 1995; 06/1995
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G. Mulhollan, J. Clendenin,
P. Saez,
D. Schultz,
H. Tang,
A.W. Pang,
H. Hopster,
K. Trantham,
M. Johnston,
T. Gay,
B. Johnson,
M. Magugumela,
F.B. Dunning,
G.K. Walters,
G.F. Hanne
[show abstract]
[hide abstract]
ABSTRACT: A long-standing problem in polarized electron physics is the lack
of a traceable standard for calibrating electron spin polarimeters.
While several polarimeters are absolutely calibrated to better than 2%,
the typical instrument has an inherent accuracy no better than 10%. This
variability among polarimeters makes it difficult to compare advances in
polarized electron sources between laboratories. We have undertaken an
effort to establish 100 nm thick molecular beam epitaxy grown GaAs(110)
as a material which may be used as a derivative standard for calibrating
systems possessing a solid state polarized electron source. The
near-bandgap spin polarization of photoelectrons emitted from this
material has been characterized for a variety of conditions and several
laboratories which possess well calibrated polarimeters have measured
the photoelectron polarization of cathodes cut from a common wafer.
Despite instrumentation differences, the spread in the measurements is
sufficiently small that this material may be used as a derivative
calibration standard
Particle Accelerator Conference, 1995., Proceedings of the 1995; 06/1995
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[show abstract]
[hide abstract]
ABSTRACT: The Stanford Linear Accelerator Center is currently operating with a photocathode electron gun (PEG) to produce polarized electrons for its experimental program. Bunch intensities of up to 10<sup>11</sup> electrons within 2 ns (8 A) are required from the electron gun. Operation of PEG has demonstrated a charge limit phenomenon, whereby the charge that can be extracted from the gun with an intense laser beam saturates at significantly less than 10<sup>11</sup> electrons (the expected space‐charge‐limited charge) when the photocathode quantum efficiency is low. Studies of this charge limit phenomenon observed with a GaAs photocathode are reported.
Journal of Applied Physics 07/1993; · 2.17 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The SLC polarized electron gun operates at 120 kV with very low
dark current to maintain the ultra high vacuum (UHV). This strict
requirement protects the extremely sensitive photocathode from
contaminants caused by high voltage (HV) activity. Thorough HV
processing thus required. An X-ray sensitive photographic film, a
nanoammeter in series with the gun power supply, a radiation meter, a
sensitive residual gas analyzer and surface X-ray spectrometry were used
to study areas in the gun where HV activity occurred. By reducing the
electric field gradients, carefully preparing the HV surfaces and
adhering to very strict clean assembly procedures, we found it possible
to process the gun so as to reduce both the dark current at the
operating voltage and the probability of HV discharge. These HV
preparation and processing techniques are described
Particle Accelerator Conference, 1993., Proceedings of the 1993; 06/1993
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R Alley,
H Aoyagi, J Clendenin,
J Frisch,
C Garden,
E Hoyt,
R Kirby,
L Klaisner,
A Kulikov,
R Miller,
G Mulhollan,
C Prescott,
P Sáez,
D Schultz,
H Tang,
J Turner,
K Witte,
M Woods,
A.D Yeremian,
M Zolotorev
[show abstract]
[hide abstract]
ABSTRACT: The Stanford 3-km linear accelerator at SLAC has operated exclusively since early 1992 using a polarized electron beam for its high-energy physics programs. The polarized electron source now consists of a diode-type gun with a strained-lattice GaAs photocathode DC biased at high voltage and excited with circularly polarized photons generated by a pulsed, Ti:sapphire laser system. The electron polarization at the source is > 80%. To date the source has met all the beam requirements of the SLC and fixed target programs with < 5% downtime.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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K. Abe,
T. Akagi,
P.L. Anthony,
R. Antonov,
R.G. Arnold,
T. Averett,
H.R. Band,
J.M. Bauer,
H. Borel,
P.E. Bosted, [......],
D. Walz,
F. Wesselmann,
J.L. White,
K. Witte,
C.C. Young,
B. Youngman,
H. Yuta,
G. Zapalac,
B. Zihlmann,
D. Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: Measurements were made at SLAC of the cross section for scattering 29 GeV electrons from carbon at a laboratory angle of 4.5°, corresponding to 0.03<x<0.1 and 1.3<Q2<2.7 GeV2. Values of R=σL/σT were extracted in this kinematic range by comparing these data to cross sections measured at a higher beam energy by the NMC collaboration. The results are in reasonable agreement with pQCD calculations and with extrapolations of the R1990 parameterization of previous data. A new fit is made including these data and other recent results.
Physics Letters B.
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K Abe,
T Akagi,
P L Anthony,
R. Antonov,
R.G. Arnold,
T. Averett,
H R Band,
J M Bauer,
H. Borel,
P. E. Bosted, [......],
D. Walz,
F. Wesselmann,
J.L. White,
K Witte,
C C Young,
B. Youngman,
H Yuta,
G Zapalac,
B. Zihlmann,
D Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: We have measured the proton and deuteron spin structure functions g[sup p][sub 1] and g[sup d][sub 1] in the region of the nucleon resonances for W2 < 5GeV2 and Q2(similar, equals)0.5 and Q2(similar, equals)1.2GeV2 by inelastically scattering 9.7 GeV polarized electrons off polarized 15NH3 and 15ND3 targets. We observe significant structure in g[sup p][sub 1] in the resonance region. We have used the present results, together with the deep-inelastic data at higher W2, to extract Gamma (Q2)(equivalent)01 g1(x,Q2)dx. This is the first information on the low-Q2 evolution of Gamma toward the Gerasimov-Drell-Hearn limit at Q2 = 0.
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K Abe,
T Akagi,
P L Anthony,
R. Antonov,
R.G. Arnold,
T. Averett,
H R Band,
J M Bauer,
H. Borel,
P. E. Bosted, [......],
T Usher,
D. Walz,
J.L. White,
K Witte,
C Young,
B. Youngman,
H Yuta,
G Zapalac,
B. Zihlmann,
D. Zimmermann
[show abstract]
[hide abstract]
ABSTRACT: The ratio g1/F1 has been measured over the range 0.03<x<0.6 and 0.3<Q2<10 (GeV/c)2 using deep-inelastic scattering of polarized electrons from polarized protons and deuterons. We find g1/F1 to be consistent with no Q2-dependence at fixed x in the deep-inelastic region Q^2>1 (GeV/c)2. A trend is observed for g1/F1 to decrease at lower Q2. Fits to world data with and without a possible Q2-dependence in g1/F1 are in agreement with the Bjorken sum rule, but Delta_q is substantially less than the quark-parton model expectation.
