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Optically pumped polarized ion sources

Description: Polarization transfer collisions between protons, atomic hydrogen, or deuterium and optically pumped alkali-metal vapour are implemented in the high current optically pumped polarized ion source (OPPIS) and the laser driven source (LDS) of nuclear polarized atoms for target applications. The OPPIS technique overcomes the limitations on intensity of the conventional atomic beam source technique and meets the requirements of the new generation of polarization experiments at multi-GeV accelerators and colliders. 17 refs., 3 figs.
Date: December 31, 1995
Creator: Zelenski, A.N.
Partner: UNT Libraries Government Documents Department

Numerical studies of Siberian snakes and spin rotators for RHIC

Description: For the program of polarized protons in RHIC, two Siberian snakes and four spin rotators per ring will be used. The Snakes will produce a complete spin flip. Spin Rotators, in pairs, will rotate the spin from the vertical direction to the horizontal plane at a given insertion, and back to the vertical after the insertion. Snakes, 180{degrees} apart and with their axis of spin precession at 90{degrees} to each other, are an effective means to avoid depolarization of the proton beam in traversing resonances. Classical snakes and rotators are made with magnetic solenoids or with a sequence of magnetic dipoles with fields alternately directed in the radial and vertical direction. Another possibility is to use helical magnets, essentially twisted dipoles, in which the field, transverse the axis of the magnet, continuously rotates as the particles proceed along it. After some comparative studies, the authors decided to adopt for RHIC an elegant solution with four helical magnets both for the snakes and the rotators proposed by Shatunov and Ptitsin. In order to simplify the construction of the magnets and to minimize cost, four identical super conducting helical modules will be used for each device. Snakes will be built with four right-handed helices. Spin rotators with two right-handed and two left-handed helices. The maximum field will be limited to 4 Tesla. While small bore helical undulators have been built for free electron lasers, large super conducting helical magnets have not been built yet. In spite of this difficulty, this choice is dictated by some distinctive advantages of helical over more conventional transverse snakes/rotators: (i) the devices are modular, they can be built with arrangements of identical modules, (ii) the maximum orbit excursion in the magnet is smaller, (iii) orbit excursion is independent from the separation between adjacent magnets, (iv) they allow ...
Date: April 17, 1995
Creator: Luccio, A.
Partner: UNT Libraries Government Documents Department


Description: With a partial Siberian snake in the AGS and transport lines with interspersed horizontal and vertical bends, the incoming spin direction at the injection points of both the collider rings is not likely to match the ideal vertical stable spin direction of RHIC which has two full helical Siberian snakes per ring. In this paper we examine the matching of a polarized beam transferred from the AGS into RHIC. The present 5% partial solenoidal snake as well as a proposed 20% superconducting helical are considered for the AGS. Solutions with retuned snakes in RHIC to better match the incoming beam have been found.
Date: November 6, 2002
Partner: UNT Libraries Government Documents Department

Run-09 pC polarimeter analysis

Description: Analysis of PC polarimeter data at {radical}s = 200 and 500 GeV from Run9 is presented. Final polarization results, fill-by-fill, for blue and yellow beams, as to be used by RHIC experiments (in collisions) are released and collected in http://www4.rcf.bnl.gov/cnipol/pubdocs/Run09Offline/. Global relative systematic uncertainties {delta}P/P (to be considered as correlated from fill to fill) are 4.7% for 100 GeV beams, and 8.3% (12.1%) for blue (yellow) 250 GeV beams. For a product of two beam polarizations P{sub B} {center_dot} P{sub Y} (used in double spin asymmetry measurements) the relative uncertainty {delta}(P{sub B} {center_dot} P{sub Y})/(P{sub B} {center_dot} P{sub Y}) 8.8% for 100 GeV beams and 18.5% for 250 GeV beams. For the average between two beam polarization (P{sub B} + P{sub Y})/2 (used in single spin asymmetry measurements, when data from two polarized beams are combined) the relative uncertainty is 4.4% for 100 GeV beams and 9.2% for 250 GeV beams. Larger uncertainties for 250 GeV beams relate to significant rate related systematic effects experienced in the first part of Run9 (due to thicker targets used and smaller trans. beam size at higher beam energy).
Date: August 1, 2010
Creator: Alekseev, I.; Aschenauer, E.; Atoyan, G.; Bazilevsky, A.; Gill, R.; Huang, H. et al.
Partner: UNT Libraries Government Documents Department

Spatial and Temporal Characterization of Femtosecond Pulses at High-Numerical Aperture Using Collinear, Background-Free, Third-Harmonic Autocorrelation

Description: We show that a simple plane wave analysis can be used even under tight focusing conditions to predict the dependence of third-harmonic generation on the polarization state of the incident beam. Exploiting this fact, we then show that circularly polarized beams may be used to spatially characterize the beam focus and temporally characterize ultrashort pulses in high numerical aperture systems by experimentally demonstrating, for the first time, novel collinear, background-free, third-harmonic intensity autocorrelations in time and space in a high numerical aperture microscope. We also discuss the possibility of using third harmonic generation with circularly polarized beams for background-free collinear frequency resolved optical gating.
Date: August 9, 2004
Creator: Fittinghoff, D N; der Au, J A & Squier, J A
Partner: UNT Libraries Government Documents Department

Anti-Hyperon polarization in high energy pp collisions withpolarized beams

Description: We study the longitudinal polarization of the {bar {Sigma}}{sup -}, {bar {Sigma}}{sup +}, {bar {Xi}}{sup 0} and {bar {Xi}}{sup +} anti-hyperons in polarized high energy pp collisions at large transverse momenta, extending a recent study for the {bar {Lambda}} antihyperon. We make predictions by using different parameterizations of the polarized parton densities and models for the polarized fragmentation functions. Similar to the {bar {Lambda}} polarization, the {bar {Xi}}{sup 0} and {bar {Xi}}{sup +} polarizations are found to be sensitive to the polarized anti-strange sea, {Delta}{bar s}(x), in the nucleon. The {bar {Sigma}}{sup -} and {bar {Sigma}}{sup +} polarizations show sensitivity to the light sea quark polarizations, {Delta}{bar u}(x) and {Delta}{bar d}(x), and their asymmetry.
Date: November 20, 2007
Creator: Chen, Ye; Liang, Zuo-tang; Sichtermann, Ernst; Xu, Qing-hua & Zhou, Shan-shan
Partner: UNT Libraries Government Documents Department

Polarized proton acceleration program at the AGS and RHIC

Description: Presented is an overview of the program for acceleration of polarized protons in the AGS and their injection into the RHIC collider. The problem of depolarizing resonances in strong focusing circulator accelerators is discussed. The intrinsic resonances are jumped over by the fast tune jump, and a partial Siberian Snake is used to compensate for over forty imperfection resonances in the AGS. Two sets of full Siberian Snake and spin rotators will be employed in RHIC.
Date: June 1995
Creator: Lee, Y. Y.
Partner: UNT Libraries Government Documents Department

Overcoming weak intrinsic depolarizing resonances with energy-jump

Description: In the recent polarized proton runs in the AGS, a 5% partial snake was used successfully to overcome the imperfection depolarizing resonances. Polarized proton beam was accelerated up to the required RHIC injection energy of 25 GeV. However, significant amount of polarization was lost at 0+{nu}{sub y}, 12+{nu}{sub y} and 36+{nu}{sub y}, which is believed to be partially due to the coupling resonances. To overcome the coupling resonance, an energy-jump was generated by rapidly changing the beam circumference using the powerful AGS rf system. It clearly demonstrates that the novel energy-jump method can successfully overcome coupling resonances and weak intrinsic resonances.
Date: July 1, 1997
Creator: Huang, H.; Ahrens, L. & Alessi, J.G.
Partner: UNT Libraries Government Documents Department


Description: The second part of the sixth RHIC Spin Collaboration (RSC) meeting was held on November 15, 2001 at Brookhaven National Laboratory. Previous meetings have elaborated on the new generation of proton spin-structure studies (e.g. gluon polarization and flavor separation of q and {bar q} polarizations via real W{sup {+-}} production) enabled by studying polarized proton collisions at energies and momentum transfers where perturbative QCD models are expected to be applicable. The focus of this meeting was on many of the experimental issues that must be resolved to achieve these physics goals. This summary is written with the benefit of hindsight following the completion of the first-ever run of a polarized proton collider. This first run can be considered as a successfully completed milestone of the RHIC Spin Collaboration. Other milestones remain important. Long term machine items were identified in Waldo Mackay's talk, the most important being the completion of the spin rotator magnets that will be installed in 2002 to allow the flexible orientation of the proton beam polarization at the PHENM and STAR experiments. At the meeting Waldo discussed a stronger partial snake magnet for the AGS as a means of producing highly polarized proton beams to inject into RHIC. Developments subsequent to this meeting suggest that a superconducting helical dipole magnet may be feasible for the AGS, and is likely to be needed to achieve the 70% beam polarization in RHIC. Longer term items were also presented, including potential increases in luminosity by the addition of electron cooling to RHIC and the possibility of increasing the collision energy by {approx}20% by replacement of the DX magnets. These items could be considered for a second generation of RHIC spin experiments. The other topics covered at the meeting were related to polarimetry and to the absolute calibration of the proton ...
Date: November 15, 2001
Creator: Bland, L. & Saito, N.
Partner: UNT Libraries Government Documents Department

An improved limit on jet handedness in Z{sup 0} decays

Description: We present the results of an improved search for jet handedness in hadronic decays of Z{sup degree} bosons collected by the SLD experiment at SLAC. Quark and antiquark jets, expected to be oppositely polarized in Z{sup degree} decays, were separated using the large forward-backward quark asymmetry induced by the highly polarized SLC electron beam. The larger data sample and beam polarization of the 1994/5 SLC/SLD run yield a factor of two improvement in our sensitivity to jet handedness. Assuming Standard Model values of quark polarizations we set an improved upper limit on the analyzing power of the handedness method.
Date: July 1995
Creator: Collaboration, The SLD
Partner: UNT Libraries Government Documents Department

Polarization measurement and vertical aperture optimization for obtaining circularly polarized bend-magnet radiation

Description: Using multilayer linear polarizers, we have studied the polarization state of radiation from bend magnet beamline 9.3.2 at Advanced Light Source as function of vertical oping angle at photon energies 367 and 722 eV. Both a fine slit and a coarse semi-aperture were stepped across the beam to accept different parts of the vertical radiation fan. Polarimetry yields the degree of linear polarization directly and the degree of circular polarization indirectly assuming an immeasurably small amount of unpolarized radiation based on close agreement of theory and experiment for linear polarization. Results are in good agreement with theoretical calculations, with departures from theory owing to uncertainty in effective aperture of the measured beam. The narrow 0.037 mrad aperture on the orbit plane transmits a beam whose degree of linear polarization exceeds 0.99 at these energies. The wide semi-aperture blocking the beam from above and below transmits a beam with a max figure of merit, given by the square root of flux times degree of circular polarization, when the aperture edge is on the orbit plane thus blocking only half of the total available flux.
Date: October 1, 1995
Creator: Kortright, J.B.; Rice, M. & Hussain, Z.
Partner: UNT Libraries Government Documents Department

Polarized proton experiment in the AGS with a partial snake

Description: In three polarized proton runs at the AGS it was recently shown that the imperfection depolarizing resonances in the AGS can be overcome with a 5% partial snake and the intrinsic depolarizing resonances could be jumped with the pulsed tune-jump quadrupoles even in the presence of the partial snake. For the first time polarized proton beam was accelerated up to the required RHIC injection energy of 25 GeV. No polarization was lost due to the imperfection resonances and the depolarization from most intrinsic resonances was avoided with the tune-jump quadrupoles. However, significant amount of polarization was lost at 0+{nu}{sub y}, 12+{nu}{sub y} and 36+{nu}{sub y}, which is believed to be partially due to coupling resonances. A novel energy-jump method and other new schemes to overcome the coupling and intrinsic resonances are discussed.
Date: December 1, 1996
Creator: Huang, H.; Ahrens, L. & Alessi, J.G.
Partner: UNT Libraries Government Documents Department

The polarized electron beam for the SLAC Linear Collider

Description: The SLAC Linear Collider has been colliding a polarized electron beam with an unpolarized positron beam at the Z{sup 0} resonance for the SLD experiment since 1992. An electron beam polarization of close to 80% has been achieved for the experiment at luminosities up to 8 {center_dot} 10{sup 29} cm{sup {minus}2} s{sup {minus}1}. This is the world`s first and only linear collider, and is a successful prototype for the next generation of high energy electron linear colliders. This paper discusses polarized beam operation for the SLC, and includes aspects of the polarized source, spin transport and polarimetry.
Date: October 1, 1996
Creator: Woods, M.
Partner: UNT Libraries Government Documents Department

Conceptual design of a proton polarimeter for RHIC

Description: A two-arm pion polarimeter utilizing toroidal magnets is being considered for use with the polarized protons beam at RHIC. The system will enable measurements of beam polarization at all RHIC energies from injection to flattop. This is a necessary diagnostic tool for tuning the RHIC snake magnets and other polarization controlling elements. Toroidal magnets constrain the pion trajectories allowing the device to be compact so that it can fit within the limited space available. A viable magnet design has been completed and suitable target configuration and operating scenario have been identified.
Date: December 1, 1996
Creator: Alekseev, I.; Belikov, N. & Bunce, G.
Partner: UNT Libraries Government Documents Department

Effect of SiO{sub 2} overcoat thickness on laser damage morphology of HfO{sub 2}/SiO{sub 2} Brewster`s angle polarizers at 1064 nm

Description: HfO{sub 2}/SiO{sub 2} Brewster`s angle polarizers are being developed at LLNL for the National Ignition Facility. Damage threshold studies using a 3-ns pulse length 1064-nm laser have revealed a number of different damage morphologies such as nodular ejection pits, plasma scalds, flat bottom pits, and overcoat delaminations. Of these laser damage morphologies, delaminations have the most negative impact on the multilayer stability. By selecting the proper SiO{sub 2} overcoat thickness, the delamination morphology is eliminated without significantly modifying the spectra characteristics of the coating and the functional damage threshold is increased by 2-4x. A model of the thermal mechanical response of the overcoats is presented for various SiO{sub 2} overcoat thicknesses. The overcoat thickness influences the electric-field profile resulting in different thermal gradients between the outer SiO{sub 2} and HfO{sub 2} layers. This modeling effort attempts to understand the relation between the thermal stress distribution in the overcoat and the occurrence of delamination.
Date: March 3, 1997
Creator: Stolz, C.J.; Genin, F.Y.; Reitter, T.A.; Molau, N.E.; Bevis, R.P.; von Gunten, M.K. et al.
Partner: UNT Libraries Government Documents Department

Polarization and charge limit studies of strained GaAs photocathodes

Description: This thesis presents studies on the polarization and charge limit behavior of electron beams produced by strained GaAs photocathodes. These photocathodes are the source of high-intensity, high-polarization electron beams used for a variety of high-energy physics experiments at the Stanford Linear Accelerator Center. Recent developments on P-type, biaxially-strained GaAs photocathodes have produced longitudinal polarization in excess of 80% while yielding beam intensities of {approximately} 2.5 A/cm{sup 2} at an operating voltage of 120 kV. The SLAC Gun Test Laboratory, which has a replica of the SLAC injector, was upgraded with a Mott polarimeter to study the polarization properties of photocathodes operating in a high-voltage DC gun. Both the maximum beam polarization and the maximum charge obtainable from these photocathodes have shown a strong dependence on the wavelength of illumination, on the doping concentration, and on the negative electron affinity levels. The experiments performed for this thesis included studying the effects of temperature, cesiation, quantum efficiency, and laser intensity on the polarization of high-intensity beams. It was found that, although low temperatures have been shown to reduce the spin relaxation rate in bulk semiconductors, they don`t have a large impact on the polarization of thin photocathodes. It seems that the short active region in thin photocathodes does not allow spin relaxation mechanisms enough time to cause depolarization. Previous observations that lower QE areas on the photocathode yield higher polarization beams were confirmed. In addition, high-intensity, small-area laser pulses were shown to produce lower polarization beams. Based on these results, together with some findings in the existing literature, a new proposal for a high-intensity, high-polarization photocathode is given. It is hoped that the results of this thesis will promote further investigation on the properties of GaAs photocathodes.
Date: March 1, 1997
Creator: Saez, P.J.
Partner: UNT Libraries Government Documents Department

Measurements of {Delta}{sigma}{sub L}(pp) and {Delta}{sigma}{sub L}({bar p}p) at 200 GeV/c

Description: A measurement was made at Fermilab of the difference in the total cross sections between states with beam and target polarizations aligned antiparallel and parallel, {Delta}{sigma}{sub L} = {Delta}{sigma}({r_reversible}) - {Delta}{sigma}({R_arrow}), using 200-GeV/c, polarized proton and antiproton beams and a polarized proton target. This measurement explores the spin dependence of particle interactions and the constituent dynamics. A difference in the spin-dependent total cross sections has been observed in previous experiments at lower energies, and this experiment was the first to explore possible spin effects in {Delta}{sigma}{sub L} at much higher energies. The polarized proton beam is produced from parity-nonconserving decays of the {Lambda}{sup 0} hyperon, where protons emitted from these decays have their spins aligned along the direction of their momenta. The {Lambda} hyperons are produced, along with other particles, when unpolarized, 800-GeV/c protons strike a beryllium target. A virtual source of protons is produced at the target from these decays and the proton polarization is correlated to the transverse distance from the target. A beam of polarized antiprotons can be produced in an analogous manner using {bar {Lambda}{sup 0}} decays. The beam transport system goal was to produce no net spin precession and to preserve the correlation between the beam particle polarization and the transverse position at the virtual source. The beam transport used four sets of quadrupole magnets to focus the beam at intermediate and final focal points. An electronic, particle-tagging system was located at the intermediate focus, while the polarized target was near the final focus.
Date: February 1, 1995
Creator: Grosnick, D.P.
Partner: UNT Libraries Government Documents Department

The SLAC polarized electron source

Description: The SLAC polarized electron source employs a photocathode DC high voltage gun with a loadlock and a YAG pumped Ti:sapphire laser system for colliding beam experiments or a flash lamp pumped Ti:sapphire laser for fixed target experiments. It uses a thin, strained GaAs(100) photocathode, and is capable of producing a pulsed beam with a polarization of {ge}80% and a peak current exceeding 10 A. Its operating efficiency has reached 99%. The physics and technology of producing high polarization electron beams from a GaAs photocathode will be reviewed. The prospects of realizing a polarized electron source for future linear colliders will also be discussed.
Date: June 1, 1995
Creator: Tang, H.; Alley, R. & Frisch, J.
Partner: UNT Libraries Government Documents Department

The Stanford Linear Collider

Description: The Stanford Linear Collider (SLC) is the first and only high-energy e{sup +}e{sup {minus}} linear collider in the world. Its most remarkable features are high intensity, submicron sized, polarized (e{sup {minus}}) beams at a single interaction point. The main challenges posed by these unique characteristics include machine-wide emittance preservation, consistent high intensity operation, polarized electron production and transport, and the achievement of a high degree of beam stability on all time scales. In addition to serving as an important machine for the study of Z{sup 0} boson production and decay using polarized beams, the SLC is also an indispensable source of hands-on experience for future linear colliders. Each new year of operation has been highlighted with a marked improvement in performance. The most significant improvements for the 1994-95 run include new low impedance vacuum chambers for the damping rings, an upgrade to the optics and diagnostics of the final focus systems, and a higher degree of polarization from the electron source. As a result, the average luminosity has nearly doubled over the previous year with peaks approaching 10{sup 30} cm{sup {minus}2}s{sup {minus}1} and an 80% electron polarization at the interaction point. These developments as well as the remaining identifiable performance limitations will be discussed.
Date: June 1, 1995
Creator: Emma, P.
Partner: UNT Libraries Government Documents Department

Polarized neutrons in RHIC

Description: There does not appear to be any obvious way to accelerate neutrons, polarized or otherwise, to high energies by themselves. To investigate the behavior of polarized neutrons the authors therefore have to obtain them by accelerating them as components of heavier nuclei, and then sorting out the contribution of the neutrons in the analysis of the reactions produced by the heavy ion beams. The best neutron carriers for this purpose are probably {sup 3}He nuclei and deuterons. A polarized deuteron is primarily a combination of a proton and a neutron with their spins pointing in the same direction; in the {sup 3}He nucleus the spins of the two protons are opposite and the net spin (and magnetic moment) is almost the same as that of a free neutron. Polarized ions other than protons may be accelerated, stored and collided in a ring such as RHIC provided the techniques proposed for polarized proton operation can be adapted (or replaced by other strategies) for these ions. This paper discusses techniques for accelerating polarized {sup 3}He nuclei and deuterons.
Date: April 20, 1998
Creator: Courant, E.D.
Partner: UNT Libraries Government Documents Department