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Positrons for linear colliders

Description: The requirements of a positron source for a linear collider are briefly reviewed, followed by methods of positron production and production of photons by electromagnetic cascade showers. Cross sections for the electromagnetic cascade shower processes of positron-electron pair production and Compton scattering are compared. A program used for Monte Carlo analysis of electromagnetic cascades is briefly discussed, and positron distributions obtained from several runs of the program are discussed. Photons from synchrotron radiation and from channeling are also mentioned briefly, as well as positron collection, transverse focusing techniques, and longitudinal capture. Computer ray tracing is then briefly discussed, followed by space-charge effects and thermal heating and stress due to showers. (LEW)
Date: November 1, 1987
Creator: Ecklund, S.
Partner: UNT Libraries Government Documents Department

Status of SLC

Description: The current construction status of the Stanford Linear Collider (SLC) is described along with a brief overview of the project. Tests of completed parts of the machine are summarized.
Date: May 1, 1985
Creator: Ecklund, S.D.
Partner: UNT Libraries Government Documents Department

Survey of beam instrumentation used in SLC

Description: A survey of beam instruments used at SLAC in the SLC machine is presented. The basic utility and operation of each device is briefly described. The various beam instruments used at the Stanford Linear Collider (SLC), can be classified by the function they perform. Beam intensity, position and size are typical of the parameters of beam which are measured. Each type of parameter is important for adjusting or tuning the machine in order to achieve optimum performance. 39 refs.
Date: March 1, 1991
Creator: Ecklund, S.D.
Partner: UNT Libraries Government Documents Department

Performance of the 1994/95 SLC final focus system

Description: A major upgrade to the SLC final focus was installed in 1994 to eliminate the dominant third-order aberration of the system, and thereby to reduce the vertical beam size at the IP by a factor of two. At low current, the optimal beam size of about 400 nm is now routinely established, and its sensitivity to orbit variations, to changes of emittance and energy spread, and to other beam parameters has been studied. For intensities above 3 {times} 10{sup 10} particles per bunch, tuning is more difficult due to increased fluctuations of energy, orbit, and emittances. Nonetheless, the expected beam size of about 600 nm has been observed. New procedures and diagnostics allow easier tuning and optimization of the final focus, and also a first measurement of the emittance increase in the arcs.
Date: June 1, 1995
Creator: Zimmermann, F.; Barklow, T. & Ecklund, S.
Partner: UNT Libraries Government Documents Department

The high-gradient S-band linac for initial acceleration of the SLC (SLAC linear collider) intense positron bunch

Description: Although short lengths of S-band standing-wave, disk-loaded waveguide have been successfully RF-processed to accelerating gradients equivalent to about 175 MeV/m in a traveling-wave structure, the 20 MeV/m gradient of the SLC 50 GeV linac has been the highest gradient S-band accelerator in operation. However, the 1.5 m traveling-wave constant impedance capture section for the SLC positron source, operating with a dedicated 60 MW klystron, is now routinely accelerating single-bunch beams of more than 7 /times/ 10/sup 10/ e/sup +//pulse at rates of up to 60 Hz with an accelerating gradient section are described. 11 refs., 1 fig. 1 tab.
Date: August 1, 1989
Creator: Clendenin, J.E.; Ecklund, S.D. & Hoag, H.A.
Partner: UNT Libraries Government Documents Department

Results from a prototype permanent magnet dipole-quadrupole hybrid for the PEP-II B-factory

Description: We describe the construction of a prototype hybrid permanent magnet dipole and quadrupole. The magnet consists of two concentric rings of Sm{sub 2}Co{sub 17} magnetic material 5 cm in length. The outer ring is made of 16 uniformly magnetized blocks assembled as a Halbach dipole and the inner ring has 32 blocks oriented in a similar fashion so as to generate a quadrupole field. The resultant superimposed field is an offset quadrupole field which allows us to center the field on the high-energy beam in the interaction region of the PEP-II B-factory. The dipole blocks are glued to the inside surface of an outer support collar and the quadrupole blocks are held in a fixture that allows radial adjustment of the blocks prior to potting the entire assembly with epoxy. An extensive computer model of the magnet has been made and from this model we developed a tuning algorithm that allowed us to greatly reduce the n=3 17 harmonics of the magnet.
Date: June 1, 1997
Creator: Sullivan, M.; Bowden, G. & Ecklund, S.
Partner: UNT Libraries Government Documents Department

SLC positron source pulsed flux concentrator

Description: SLC positron beams produced by a high energy electron beam, impinging on a high Z target, have initially small transverse size but large divergence, a situation ill matched to the following S-band accelerator. The flux concentrator is an adiabatic matching device placed between the target and this accelerator, which trades divergence versus size. It produces a magnetic field with a sharp rise over less than 5 mm to its peak value, and then falling off adiabatically over 10 cm. It is a 12 turn, 10 cm long copper coil with a cylindrical outside radius of 4 cm and a conical inside radius growing from 3.5 mm to 2.6 cm. The 0.2 mm gaps between the individual windings were manufactured by electric discharge machining out of one copper block. Excitation current and water cooling is provided by a hollow rectangular copper conductor brazed to the outside of the coil (also 12 turns). The pulsed magnetic field has a maximum strength of 58 kG at 16 kA. At the terminals, the coil has an inductance of 0.8 {mu}H. Current shape is a half sinusoidal wave with a bottom width of 5 {mu}s, and the system operates at a repetition rate of 120 Hz. The coil has only one supporting ceramic insulator at the low voltage front end. The flux concentrator has improved the positron yield approximately 3 times and had no failure in operation during several years. 10 refs., 5 figs.
Date: June 1, 1991
Creator: Kulikov, A.V.; Ecklund, S.D. & Reuter, E.M.
Partner: UNT Libraries Government Documents Department

A Preliminary Interaction Region Design for a Super B-Factory

Description: The success of the two B-Factories (PEP-II and KEKB) has encouraged us to look at design parameters for a B-Factory with a 30-50 times increase in the luminosity of the present machines to a luminosity of L {approx} 1 x 10{sup 36} cm{sup -2} sec{sup -1}. We present an initial design of an interaction region for a ''SuperB'' accelerator with a crossing angle of {+-}14 mrad and include a discussion of the constraints, requirements and concerns that go into designing an interaction region for these very high luminosity e{sup +}e{sup -} machines.
Date: June 10, 2005
Creator: Sullivan, M.; Donald, M.; Ecklund, S.; Novokhatski, A.; Seeman, J.; Wienands, U. et al.
Partner: UNT Libraries Government Documents Department

The beam-stay-clear definition of the PEP-II B Factory

Description: We describe the definition of the beam-stay-clear (BSC) for the PEP-II project collaboration of SLAC, LBNL, and LLNL. We devote special attention to the region near the collision point where both beams, the low energy beam (LEB) and the high energy beam (HEB) have large beta function values. The BSC of each beam is defined so as to maximize the flexibility of the accelerator design while at the same time satisfying the mechanical constraints imposed by getting the beams separated after collision and by keeping the beams inside the good field region of the final focusing magnets. The beam separation scheme, which plays an important role in the BSC definition, is also described. The flexibility of the design is explored by studying various parameter values for luminosity, tune shift, {beta}{sub y}{sup *} and vertical-to-horizontal beam aspect ratio and verifying that the beam envelopes generated by these changes remain inside the defined BSC.
Date: June 1, 1996
Creator: Sullivan, M.; Ecklund, S.; Seeman, J.; Wienands, U. & Zisman, M.
Partner: UNT Libraries Government Documents Department

Isochronous 180 degree turns for the SLC positron system

Description: The design of the compact, achromatic, second order isochronous 180{degrees} turn for the SLC positron transport system will be described. Design criteria require an energy range of 200{plus minus}20 MeV, energy acceptance of {plus minus}5%, transverse admittance of 25{pi} mm-mr, and minimal lengthening of the 3 to 4 mm (rms) positron bunch. The devices had to fit within a maximum height or width of about 10 ft. Optics specifications and theoretical performance are presented and compared to experimental results based on streak camera measurements of bunch length immediately after the first isochronous turn (200 MeV) and positron beam energy spread after S-band acceleration to 1.15 GeV. 5 refs., 7 figs.
Date: May 1, 1991
Creator: Helm, R.H.; Clendenin, J.E.; Ecklund, S.D.; Kulikov, A.V. & Pitthan, R.
Partner: UNT Libraries Government Documents Department

Update on the high-current injector for the Stanford Linear collider

Description: The high current injector has become operational. There are two crucial areas where improvements must be made to meet collider specifications: while the injector can produce up to 10/sup 11/ e/sup -/ in a single S-band bucket, initially much of this charge was captured in a low energy tail and was this not suitable for transport through the accelerator and injection into the damping ring. Pulse to pulse position jitter has been observed, resulting in transverse wake field which increases beam emittance. The problems described above contribute to substantial current loss during transport from the injector (40 MeV) to the SLC damping ring (1.2 GeV). Experimental studies are continuing with the aim of understanding and improving beam characteristics including bunch length, pulse to pulse stability and emittance. The present status of these studies is reported.
Date: March 1, 1983
Creator: James, M.B.; Clendenin, J.E.; Ecklund, S.D.; Miller, R.H.; Sheppard, J.C.; Sinclair, C.K. et al.
Partner: UNT Libraries Government Documents Department

Virtual Accelerator for Accelerator Optics Improvement

Description: Through determination of all quadrupole strengths and sextupole feed-downs by fitting quantities derivable from precision orbit measurement, one can establish a virtual accelerator that matches the real accelerator optics. These quantities (the phase advances, the Green's functions, and the coupling ellipses tilt angles and axis ratios) are obtained by analyzing turn-by-turn Beam Position Monitor (BPM) data with a model-independent analysis (MIA). Instead of trying to identify magnet errors, a limited number of quadrupoles are chosen for optimized strength adjustment to improve the virtual accelerator optics and then applied to the real accelerator accordingly. These processes have been successfully applied to PEP-II rings for beta beating fixes, phase and working tune adjustments, and coupling reduction to improve PEP-II luminosity.
Date: September 30, 2005
Creator: Yan, Y.T.; Cai, Y.; Decker, F-J.; Ecklund, S.; Irwin, J.; Seeman, J. et al.
Partner: UNT Libraries Government Documents Department

Parameters for a Super-Flavor-Factory

Description: A Super Flavor Factory, an asymmetric energy e{sup +}e{sup -} collider with a luminosity of order 10{sup 36} cm{sup -2} s{sup -1}, can provide a sensitive probe of new physics in the flavor sector of the Standard Model. The success of the PEP-II and KEKB asymmetric colliders in producing unprecedented luminosity above 10{sup 34} cm{sup -2} s{sup -1} has taught us about the accelerator physics of asymmetric e{sup +}e{sup -} collider in a new parameter regime. Furthermore, the success of the SLAC Linear Collider and the subsequent work on the International Linear Collider allow a new Super-Flavor collider to also incorporate linear collider techniques. This note describes the parameters of an asymmetric Flavor-Factory collider at a luminosity of order 10{sup 36} cm{sup -2} s{sup -1} at the Y(4S) resonance and about 10{sup 35} cm{sup -2} s{sup -1} at the {tau} production threshold. Such a collider would produce an integrated luminosity of about 10,000 fb{sup -1} (10 ab{sup -1}) in a running year (10{sup 7} sec) at the Y(4S) resonance. In the following note only the parameters relative to the Y(4S) resonance will be shown, the ones relative to the lower energy operations are still under study.
Date: June 27, 2006
Creator: Seeman, J.T.; Cai, Y.; Ecklund, S.; Novokhatski, A.; Seryi, A.; Sullivan, M. et al.
Partner: UNT Libraries Government Documents Department

Orbit Response Matrix Analysis Applied at PEP-II

Description: The analysis of orbit response matrices has been used very successfully to measure and correct the gradient and skew gradient distribution in many accelerators. It allows determination of an accurately calibrated model of the coupled machine lattice, which then can be used to calculate the corrections necessary to improve coupling, dynamic aperture and ultimately luminosity. At PEP-II, the Matlab version of LOCO has been used to analyze coupled response matrices for both the LER and the HER. The large number of elements in PEP-II and the very complicated interaction region present unique challenges to the data analysis. All necessary tools to make the analysis method useable at PEP-II have been implemented and LOCO can now be used as a routine tool for lattice diagnostic.
Date: May 17, 2005
Creator: Steier, C.; Wolski, A.; /LBL, Berkeley; Ecklund, S.; Safranek, J.A.; Tenenbaum, P. et al.
Partner: UNT Libraries Government Documents Department

Interaction region design at the PEP-II B Factory

Description: We describe the Interaction Region (IR) for the PEP-II project, a collaboration of SLAC, LBNL, and LLNL. The near IR region inboard of 3 m from the interaction point (IP) is designed to focus the 3.1 GeV low energy beam (LEB) and bring it into head-on collision with the 9 GeV high energy beam (HEB). We describe the overall design parameters of this area and the integration with the detector geometry. Permanent magnet (PM) dipoles and quadrupoles inside the 1.5 T solenoidal field of the detector are described. The beam separation is initiated by a dipole field made from PM blocks in a stepped conical geometry in order to maximize detector solid angle coverage. The beam separation is completed by a hybrid PM quadrupole - dipole. The vacuum chamber is designed to mask synchrotron radiation (SR) away from the beam pipe located around the IP and to absorb the power (70 kW) generated by the SR, image current losses and higher-order-mode (HOM) losses.
Date: June 1, 1996
Creator: Sullivan, M.; Bowden, G.; DeStaebler, H.; Ecklund, S.; Hodgson, J.; Mattison, T. et al.
Partner: UNT Libraries Government Documents Department

The NLC positron source

Description: A baseline design for the NLC positron source based on the existing SLC positron system is described. The proposed NLC source consists of a dedicated S-band electron accelerator, a conventional positron production and capture system utilizing a high Z target and an adiabatic matching device, and an L-band positron linac. The invariant transverse acceptance of the capture system is 0.06 m{center_dot}rad, ensuring an adequate positron beam intensity for the NLC.
Date: May 1, 1995
Creator: Tang, H.; Kulikov, A.V.; Clendenin, J.E.; Ecklund, S.D. & Miller, R.A.
Partner: UNT Libraries Government Documents Department

Design of a high yield position source

Description: The Stanford Linear Collider (SLC) requires a positron source with a yield large enough to give equal number of positrons and electrons at the interaction point. In addition, the colliding positrons must have an emittance and bunch length similar to the electron beam. This report describes the design of a high yield positron source to give these characteristics.
Date: April 1, 1985
Creator: Bulos, F.; DeStaebler, H.; Ecklund, S.; Helm, R.; Hoag, H.; Le Boutet, H. et al.
Partner: UNT Libraries Government Documents Department

Making electron beams for the SLC linac

Description: A source of high-intensity, single-bunch electron beams has been developed at SLAC for the SLC. The properties of these beams have been studied extensively utilizing the first 100-m of the SLAC linac and the computer-based control system being developed for the SLC. The source is described and the properties of the beams are summarized. 9 references, 2 figures, 1 table.
Date: January 1, 1984
Creator: Clendenin, J.E.; Ecklund, S.D.; James, M.B.; Miller, R.H.; Sheppard, J.C.; Sodja, J. et al.
Partner: UNT Libraries Government Documents Department

ASYMMETRY IN n+ PHOTOPRODUCTION FROM A POLARIZED TARGET AT 5 AND16 GeV

Description: The authors have measured the asymmetry in the cross section for the reaction {gamma}p {yields} {pi}{sup +}n between the two stages of polarization of the initial proton normal to the plane of scattering. The initial laboratory photon energies, k, were 5 GeV and 16 GeV, and the regions of momentum transfer, t, covered were 0.14 {le} {radical}-t {le} 1.01 GeV/c and 0.14 {le} {radical}-t {le} 0.78 GeV/c respectively. A butanol polarized target was used with the SLAC 20 GeV/c magnetic spectrometer. The data show a sizeable asymmetry at both 5 GeV and 16 GeV. The 16 GeV data peak at {radical}-t {approx} 0.30 GeV/c with an asymmetry of about -0.70, and the 5 GeV data pak at {radical}-t {approx} 0.80 GeV/c with an asymmetry of about -0.70. The direction of our normal to the scattering plane is along (photon in) x (pion out).
Date: June 1, 1970
Creator: Morehouse, C.C.; Borghini, M.; Chamberlain, O.; Fuzesy, R.; Gorn,W.; Powell, T. et al.
Partner: UNT Libraries Government Documents Department

Parameters of a Super-B-Factory Design

Description: Parameters are being studied for a high luminosity e{sup +}e{sup -} collider operating at the Upsilon 4S that would deliver a luminosity in the range of 7 to 10 x 10{sup 35}/cm{sup 2}/s. Particle physics studies dictate that a much higher luminosity collider than the present B-Factory accelerators will be needed to answer future new key physics questions. The success of the present B-Factories, PEP-II and KEKB, in producing unprecedented luminosity with very short commissioning times has taught us about the accelerator physics of asymmetric e{sup +}e{sup -} colliders in a new parameter regime. Such a collider could produce an integrated luminosity of 10,000 fb{sup -1} (10 ab{sup -1}) in a running year. A Super-B-Factory [1-8] with 30 to 50 times the performance of the present PEP-II accelerator would incorporate a higher frequency RF system, lower impedance vacuum chambers, higher power synchrotron radiation absorbers, and stronger bunch-by-bunch feedback systems. The present injector based on the SLAC linac needs no improvements and is ready for the Super-B-Factory.
Date: March 3, 2006
Creator: Seeman, J.; Cai, Y.; Ecklund, S.; Fox, J.D.; Heifets, S.A.; Li, N. et al.
Partner: UNT Libraries Government Documents Department

Commissioning the 90 Degree Lattice for the PEP II High Energy Ring

Description: In order to benefit from further reduction of the vertical IP beta function of the PEP-II high energy ring (HER) the bunch length should be reduced. This will be achieved by changing the phase advance from 60 degree to 90 degree in the four arcs not adjacent to the IR region, thus reducing momentum compaction by about 30% and reducing bunch length from a present 12 mm down to 8.5 mm at low beam current. In preparation to implement the 90 degree lattice the main HER quadrupole and sextupole strings and their power supplies have been reconfigured. The synchrotron tune initially will be lower but can be brought back by raising the rf voltage. Beam emittance is held at 48 nmr by introducing a significant dispersion beat in the arcs. The lattice was successfully commissioned at currents up to 800 mA in August 2007. In this paper we will compare the actual machine with the predicted behaviour, explain the correction strategies used and give an overall assessment of the operation and the benefit of the new lattice configuration.
Date: November 2, 2011
Creator: Wittmer, W.; Cai, Y.; Cheng, W.X.; Colocho, W.S.; Decker, F.J.; Ecklund, S. et al.
Partner: UNT Libraries Government Documents Department