Download or read book Recirculating Beam Breakup Study for the 12 GeV Upgrade at Jefferson Lab written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two new high gradient C100 cryomodules with a total of 16 new cavities were installed at the end of the CEBAF south linac during the 2011 summer shutdown as part of the 12-GeV upgrade project at Jefferson Lab. We surveyed the higher order modes (HOMs) of these cavities in the Jefferson Lab cryomodule test facility and CEBAF tunnel. We then studied recirculating beam breakup (BBU) in November 2011 to evaluate CEBAF low energy performance, measure transport optics, and evaluate BBU thresholds due to these HOMs. This paper discusses the experiment setup, cavity measurements, machine setup, optics measurements, and lower bounds on BBU thresholds by new cryomodules.

Download or read book Multipass Beam Breakup Study at Jefferson Lab for the 12 GeV CEBAF Upgrade written by Ilkyoung Shin and published by . This book was released on 2013 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Beam Breakup Simulations for the Jefferson Lab FEL Upgrade written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As the Jefferson Lab Free Electron Laser steadily approaches its goal of producing 1 kW of IR radiation at 5 mA of beam current at 42 MeV, plans are being considered for possible upgrade scenarios, which will extend the IR power output and allow generation of UV radiation. The upgrade scenario presently considered will bring the beam current to 10 mA and increase the energy to values close to 200 MeV. These parameters will most likely be realized in a machine configuration with a single recirculation loop for energy recovery and a linac consisting of three IRFEL-type cryomodules. Measurements of frequencies and external Q's of the revealed anomalous high-Q resonances which could lead to transverse BBU instabilities at currents close to the operating current of the machine. In this paper the authors use the simulation code TDBBU to study the BBU behavior of the FEL upgrade and estimate its threshold current under nominal settings. Furthermore, they study its dependencies on small variations of machine parameters, such as the path length of the recirculator and the frequency of selected HOMs, around their nominal points.

Download or read book Experimental Investigation of Beam Breakup in the Jefferson Laboratory 10 KW FEL Upgrade Driver written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In recirculating accelerators, and in particular energy recovery linacs (ERLs), the maximum current has been limited by multipass, multibunch beam breakup (BBU), which occurs when the electron beam interacts with the higher-order modes (HOMs) of an accelerating cavity on the accelerating pass and again on the energy recovered pass. This effect is of particular concern in the design of modern high average current energy recovery accelerators utilizing superconducting RF technology. Experimental observations of the instability at the Jefferson Laboratory 10 kW Free-Electron Laser (FEL) are presented. Measurements of the threshold current for the instability are presented and compared to the predictions of several BBU simulation codes. With BBU posing a threat to high current beam operation in the FEL Driver, several suppression schemes were developed. These include direct damping of the dangerous HOMs and appropriately modifying the electron beam optics. Preliminary results of their effectiveness in raising the threshold current for stability are presented.

Download or read book Beam Breakup Simulations for the Jefferson Lab FEL Upgrade written by I.E. Campisi and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Higher order modes and Beam Breakup Simulations in the Jefferson Lab FEL Recirculating Linac written by Lia Merminga and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Beam Current Limitations in the Jefferson Lab FEL written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of beam experiments is being planned in the Jefferson Lab FEL driver accelerator in order to study multi-pass beam breakup instabilities in the machine and to test the predictions of the numerical code TDBBU. The tests are extensions of previously performed or proposed experiments, and will be considerably more sensitive with the present configuration. The experiments will include: (a) observing the onset of instabilities by lowering the threshold current through manipulation of the beam energy, phase advance, and beam transfer matrices; (b) measurements of beam transfer functions in the recirculating mode; and (c) measurements of the single pass beam transfer functions to obtain direct measurements of the transverse shunt impedance of cavity modes with strong coupling to the beam. Simulations of the different experiments and studies of the sensitivities to the accelerator and beam parameters are presented.

Download or read book Studies of Energy Recovery Linacs at Jefferson Laboratory 1 GeV Demonstration of Energy Recovery at CEBAF and Studies of the Multibunch Multipass Beam Breakup Instability in the 10 KW FEL Upgrade Driver written by Christopher D. Tennant and published by . This book was released on 2006 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: A successful 1 GeV energy recovery demonstration with a maximum-to-injection energy ratio of 51:1 was carried out on the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory in an effort to address issues related to beam quality preservation in a large scale system. With a 1.3 km recirculation length and containing 312 superconducting radio frequency (SRF) cavities, this experiment has demonstrated energy recovery on the largest scale, and through the largest SRF environment, to date.

Download or read book Higher Order Modes and Beam Breakup Simulations in the Jefferson Lab FEL Recirculating Linac written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements were performed of the frequencies and external Q's of the first two Higher-Order Mode (HOM) dipole passbands in the eight superconducting cavities of the cryomodule used in the recirculating linac of the driver accelerator of Jefferson Lab's IR FEL. Anomalous high-Q resonances were found, which could lead to beam instabilities at currents close to the operating current of the machine. These results led to more detailed simulations of its beam breakup (BBU) behavior. The analysis indicates that a few modes are responsible for the relatively low value of 27 mA of the threshold current. A simple modification of the superconducting cavities could lead to an increase of the threshold current by an order of magnitude.

Download or read book The 12 GeV JLab Upgrade Project written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The upgrade of the CEBAF Accelerator at Jefferson Lab to 12 GeV will deliver high luminosity and high quality beams, which will open unique opportunities for studies of the quark and gluon structure of hadrons in the valence region. Such physics will be made accessible by substantial additions to the experimental equipment in combination with the increased energy reach of the upgraded machine. The emphasis of the talk will be on the program in a new experimental Hall D designed to search for gluonic excitations.

Download or read book First Observations and Suppression of Multipass Multibunch Beam Breakup in the Jefferson Laboratory FEL Upgrade written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: It is well known that the multipass, multibunch beam breakup (BBU) instability imposes a potentially severe limitation to the average current that can be accelerated in an energy recovery linac (ERL). Simulation results for Jefferson Lab's FEL Upgrade Driver are presented which predict the occurrence of BBU below the nominal operating current of the machine. In agreement with simulation, BBU was observed and preliminary measurements to identify the higher-order mode (HOM) causing the instability are shown. In addition, measurements performed to experimentally determine the threshold current are described. Using a newly developed two-dimensional BBU simulation code, we study the effect of optical suppression techniques, first proposed by Rand and Smith in 1980 [1], on the threshold current of the FEL. Specifically we consider the effect of (1) reflecting the betatron planes about 45 degrees and (2) rotating the betatron planes by 90 degrees. In two pass recirculators, a 90 degrees rotation significantly increases the threshold current of BBU. The successful installation of a five skew-quadrupole reflector in the backleg of the FEL has been shown to be effective at suppressing the instability and comments on preliminary operational experience will be given.

Download or read book Beam Physics for the 12 GeV CEBAF Upgrade Project written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Beam physics aspects of the 12 GeV Upgrade of CEBAF are presented. The CEBAF Upgrade to 12 GeV is achieved via 5.5 recirculations through the linacs, and the installation of 10 new high-gradient cryomodules. A new experimental hall, Hall D, is envisioned at the end of North Linac. Simulation results for straight-through and recirculated injectors are summarized and compared. Beam transport designs are discussed and evaluated with respect to matching and beam breakup (BBU) optimization. Effects of synchrotron radiation excitation on the beam properties are calculated. BBU simulations and derived specifications for the damping of higher order modes of the new 7-cell cavities are presented. The energies that provide longitudinal polarization in multiple experimental halls simultaneously are calculated. Finally, a detailed optics design for the Hall D transport line has been obtained.

Download or read book A Cure for Multipass Beam Breakup in Recirculating Linacs written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate a method to control the multipass dipole beam breakup instability in a recirculating linac including energy recovery. Effectiveness of an external feedback system for such a goal is shown clearly in a simplified model. We also verify the theoretical result with a simulation study.

Download or read book Beam Break up Simulations in the Jefferson Lab Free electron Laser written by Lia Merminga and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proceedings of Jefferson Lab Physics Instrumentation with 6 12 GeV Beams written by and published by . This book was released on 1998 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simultaneous Four Hall Operation for 12 GeV CEBAF written by and published by . This book was released on 2013 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The CEBAF accelerator at Jefferson lab will have a new experimental hall, Hall D, added to its existing three halls as a part of the ongoing 12 GeV upgrade. Under the present CEBAF design, there is no option for sending beam to all four halls simultaneously. At least one hall has to stay down during the machine operation. A new pattern for interleaving the beam bunches is introduced that allows simultaneous operation of all four halls and provide opportunity for additional future experimental beams. The new configuration presents only a minimal change to the existing CEBAF extraction system. In fact all the lower pass extractions will stay as they are and only the frequency of 5th?pass horizontal RF separator will change. In order to make room for the new Hall D beam among the existing three beams, the beam repetition rate is reduced only for the halls taking beam at the highest pass. This and other details of the new configuration and beam pattern will be presented and discussed. A separate paper in this conference will cover the implementation choices including changes to the beam source and extraction region.*

Download or read book Studies of Multipass Beam Breakup and Energy Recovery Using the CEBAF Injector Linac written by and published by . This book was released on 1993 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Beam breakup (BBU) instabilities in superconducting linacs are a significant issue due to the potentially high Q values of the cavity higher order modes (HOMs). The CEBAF accelerator, which employs high CW current and 5-pass recirculation through two superconducting linacs, poses unique instability problems. An experimental investigation of multipass BBU along with energy recovery has been completed using a single recirculation through the CEBAF injector linac. Experimental results are compared with computer simulation of multipass BBU.