Download or read book A New Chicane Experiment in PEP II to Test Mitigations of the Electron Cloud Effect for Linear Colliders written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Beam instability caused by the electron cloud has been observed in positron and proton storage rings, and it is expected to be a limiting factor in the performance of future colliders [1-3]. The effect is expected to be particularly severe in magnetic field regions. To test possible mitigation methods in magnetic fields, we have installed a new 4-dipole chicane experiment in the PEP-II Low Energy Ring (LER) at SLAC with both bare and TiN-coated aluminum chambers. In particular, we have observed a large variation of the electron flux at the chamber wall as a function of the chicane dipole field. We infer this is a new high order resonance effect where the energy gained by the electrons in the positron beam depends on the phase of the electron cyclotron motion with respect to the bunch crossing, leading to a modulation of the secondary electron production. Presumably the cloud density is modulated as well and this resonance effect could be used to reduce its magnitude in future colliders. We present the experimental results obtained during January 2008 until the April final shut-down of the PEP-II machine.

Download or read book Experimental Measurements of the Secondary Electron Yield in the Experimental Measurement of the Secondary Electron Yield in the PEP II Particle Accelerator Beam Line written by and published by . This book was released on 2010 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron Damping Ring (DR) of future Linear Colliders (LC) such as ILC and CLIC. To test a series of promising possible electron cloud mitigation techniques as surface coatings and grooves, in the Positron Low Energy Ring (LER) of the PEP-II accelerator, we have installed several test vacuum chambers including (i) a special chamber to monitor the variation of the secondary electron yield of technical surface materials and coatings under the effect of ion, electron and photon conditioning in situ in the beam line; (ii) chambers with grooves in a straight magnetic-free section; and (iii) coated chambers in a dedicated newly installed 4-magnet chicane to study mitigations in a magnetic field region. In this paper, we describe the ongoing R & D effort to mitigate the electron cloud effect for the LC damping ring, focusing on the first experimental area and on results of the reduction of the secondary electron yield due to in situ conditioning.

Download or read book New Simulation Results for the Electron cloud Effect at the PEP II Positron Ring written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present simulation results for the emittance blowup due to the head-tail effect induced by the electron-cloud effect (ECE) in the low-energy ring (LER) at the PEP-II B factory at SLAC.

Download or read book Secondary Electron Yield and Groove Chamber Tests in PEP II written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Possible remedies for the electron cloud in positron damping ring (DR) of the International Linear Collider (ILC) includes thin-film coatings, surface conditioning, photon antechamber, clearing electrodes and chamber with grooves or slots [1]. We installed chambers in the PEP-II Low Energy Ring (LER) to monitor the secondary electron yield (SEY) of TiN, TiZrV (NEG) and technical accelerator materials under the effect of electron and photon conditioning in situ. We have also installed chambers with rectangular grooves in straight sections to test this possible mitigation technique. In this paper, we describe the ILC R & D ongoing effort at SLAC to reduce the electron cloud effect in the damping ring, the chambers installation in the PEP-II and latest results.

Download or read book Effect of the Electron Cloud and CSR on the Upgrade of the PEP II written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Effects of the electron cloud and of the coherent synchrotron radiation (CSR) on the possible upgrade of the PEP-II B-factory are studied.

Download or read book The Electron cloud Instability in PEP II written by and published by . This book was released on 1997 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present an update on the estimate of the growth time of the multi-bunch transverse instability in the PEP-II collider arising from the interaction of the positron beam with the accumulated electron cloud. They estimate the contributions to the growth rate arising from the dipole magnets and from the pumping straight sections. They emphasize those quantities upon which the instability is most sensitive. The simulation includes measured data on the secondary emission yield for TiN-coated samples of the actual vacuum chamber. Although the analysis is still in progress, they conclude that the instability risetime is of order 1 ms, which is well within the range controllable by the feedback system.

Download or read book The Electron cloud Instability in the Arcs of the PEP II Positron Ring written by and published by . This book was released on 1998 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have applied our simulation code ''POSINST'' to evaluate, in linear approximation, the contribution to the growth rate of the electron-cloud instability (ECI) from the pumping sections and the dipole bending magnets in the arcs of the PEP-II positron ring. A key ingredient in our model is a detailed description of the secondary emission process off the TiN-coated chambers. Another important element is the analytic computation of the electric field produced by the beam, including the effects from surface charges. Space-charge forces of the electron cloud upon itself are also included, although these forces are negligible under nominal conditions. Bunch-length effects are optionally included by slicing the bunch into several kicks. We conclude that the growth rate is dominated by the pumping sections and scales linearly with the photoelectric yield Y'. For Y' = 1, our present estimate is in the range (almost equal to) 1000-1300 s−1, depending upon the value of the photon reflectivity R. This is in the range controllable by the transverse feedback system. The contributions to the growth rate from other magnets and from other sections of the ring remain to be evaluated.

Download or read book Results and Plans of the PEP II B Factory written by and published by . This book was released on 2004 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEP-II is an ee− B-Factory Collider located at SLAC operating at the Upsilon 4S resonance (3.1 GeV x 9 GeV). PEP-II has delivered, over the past five years, an integrated luminosity to the BaBar detector of about 240 fb−1 and has reached a luminosity of 9.21 x 1033/cm2/s. Steady progress is being made in reaching higher luminosity. The goal over the next several years is to reach a luminosity of at least 2.4 x 1034/cm2/s. The accelerator physics issues being addressed in PEP-II to reach this goal include the electron cloud instability, beam-beam effects, parasitic beam-beam effects, high RF beam loading, shorter bunches, lower beta y interaction region operation, and coupling control. A view of the PEP-II tunnel is shown in Figure 1. The present parameters of the PEP-II B-Factory are shown in Table 1 compared to the design. The present peak luminosity is over three times the design and the best integrated luminosity per month is 16 fb−1 that is five times the design. The highest luminosity per month is shown in Figure 2. The integrated luminosity over a month is shown in Figure 3 and the total integrated luminosity in Run 4 in shown in Figure 4. The progress in integrated luminosity has come from correcting the orbits, lowering beta y, moving the fractional horizontal tunes in both rings to just above the half integer (

Download or read book Overview and Actual Understanding of the Electron Cloud Effect and Instabilities in the Future Linear Colliders written by M. Pivi and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The electron cloud is potentially an important effect in linear colliders. Many of the effects have been evaluated. Actions to suppress the electron cloud are required for the GLC/NLC positron main damping ring (MDR or DR) and the low emittance transport lines as well as for the TESLA damping ring. There is an ongoing R & D program studying a number of possible remedies to reduce the secondary electron yield below that required.

Download or read book THE ELECTRON CLOUD INSTABILITY AT PEP II written by and published by . This book was released on 2002 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The electron cloud instability (ECI) at PEP-II enlarges the positron beam size at high currents and reduces the luminosity. The electrons for this instability come from multipacting electrons in the straight section vacuum chambers and, perhaps, photo-emission and secondary emission of electrons from the vacuum ante-chambers in the arcs. Solenoid and transverse field magnets have been placed over the vacuum chambers with about a 30 gauss field to suppress ECI. These fields have been successful in reducing the positron beam size blow up. Only about half of the drift vacuum chambers in LER have been wound with solenoids. Earlier ECI measurements are described in reference [1].

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Download or read book Performance of the PEP II B Factory Collider at SLAC written by M. C. Ross and published by . This book was released on 2006 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEP-II is an e{sup +}e{sup -} asymmetric B-Factory Collider located at SLAC operating at the Upsilon 4S resonance (3.1 GeV x 9 GeV). It has reached a luminosity of 9.21 x 10{sup 33}/cm{sup 2}/s and has delivered an integrated luminosity of 710 pb{sup -1} in one day. PEP-II has delivered, over the past six years, an integrated luminosity to the BaBar detector of over 262 fb{sup -1}. PEP-II operates in continuous injection mode for both beams boosting the integrated luminosity. The peak positron current has reached 2.45 A in 1588 bunches. Steady progress is being made in reaching higher luminosity. The goal over the next several years is to reach a luminosity of 2.1 x 10{sup 34}/cm{sup 2}/s. The accelerator physics issues being addressed in PEP-II to reach this goal include the electron cloud instability, beam-beam effects, parasitic beam-beam effects, high RF beam loading, shorter bunches, lower {beta}*{sub y} interaction region operation, and coupling control. Figure 1 shows the PEP-II tunnel.

Download or read book Investigation Into Electron Cloud Effects in the International Linear Collider Positron Damping Ring written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report modeling results for electron cloud buildup and instability in the International Linear Collider positron damping ring. Updated optics, wiggler magnets, and vacuum chamber designs have recently been developed for the 5 GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effects of diffuse and specular photon scattering on the interior surfaces of the vacuum chamber. The results provide input to the cloud buildup simulations for the various magnetic field regions of the ring. The modeled cloud densities thus obtained are used in the instability threshold calculations. We conclude that the mitigation techniques employed in this model will suffice to allow operation of the damping ring at the design operational specifications.

Download or read book PEP II Status Report written by and published by . This book was released on 1998 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main design features of the PEP-II asymmetric two-ring electron-positron B Factory collider, built at the Stanford Linear Accelerator Center, are described. This facility will complete construction in June 1998. The high energy ring, completed in May 1997, has had 3 months of commissioning and successfully stored 0.75 A of electrons. The success of the high energy ring testing validates not only its ring components, but also the injection system, the RF system and the control system all of which are common to the two rings.

Download or read book Experimental Study of Crossing Angle and Parasitic Effects at the PEP II E e Collider written by M. Sullivan and published by . This book was released on 2005 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a series of dedicated accelerator experiments, we measure the dependence of the PEP-II luminosity performance on small horizontal crossing angles and on the horizontal separation at the first parasitic crossing. The experiment is carried out by varying the IP angle of one of the beams in two different bunch patterns, one with and one without parasitic crossings. The measurements show satisfactory agreement with three-dimensional beam-beam simulations.

Download or read book PEP II Status and Future Plans written by and published by . This book was released on 2002 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The PEP-II B-Factory at SLAC has reached a luminosity of 4.6 x 1033/cm2/s and has delivered 94 fb−1 of data to the BaBar physics detector by the end of May 2002. PEP-II has delivered over 309 pb−1 in 24 hours and over 6.35 fb−1 in one month. The accelerator physics issues for these performance levels include electron cloud, beam-beam effects, parasitic beam-beam collisions, and RF beam loading. Upgrades to PEP-II are underway to increase the luminosity to 2 to 4 x 1034/cm2/s by FY2007. The accelerator physics effects that must be dealt with during these upgrades include RF loading, multi-bunch feedback, IR beta function, bunch length reduction, and interaction region vacuum chamber upgrades.

Download or read book Status Report on PEP II Performance written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEP-II [1-9] is an ee− collider with asymmetric energies (3.1 and 9 GeV, respectively) in a 2200 m tunnel at the Stanford Linear Accelerator Center. The collider produces B mesons to study a particle physics effect called CP violation as well as other physics topics. PEP-II was completed in 1998 with the first luminosity generated in July of that year. The installation of the BaBar Detector was finished in May 1999. The overall layout of PEP-II is shown in Figure 1 and the interaction region of PEP-II in Figure 2. The accelerator parameters and achievements of the High Energy Ring (HER) are listed in Table 1 and those for the Low Energy Ring (LER) in Table 2. The two beams collide at a single point in the IR2 hall where the BaBar detector is located. Beam parameters at the best luminosity are shown in Table 3 and PEP-II milestones in Table 4. In August 1999 PEP-II passed the world's record for luminosity which was 8.1 x 1032/cm2/s. The present luminosity in PEP-II is 2.15 x 1033/cm2/s which is 72% of the design. In June 2000 PEP-II delivered an integrated luminosity of 150 pb−1 in one day, which is above the design integrated luminosity per day of 135 pb−1. Over the past year PEP-II has delivered over 12 fb−1 to BaBar. BaBar has logged over 11 pb−1. The present plan is collide until the end of October 2000 followed by a three month installation period.