A Proposed High-Power UV Industrial Demonstration Laser at CEBAF

The Laser Processing Consortium, a collaboration of industries, universities, and the Continuous Electron Beam Accelerator Facility (CEBAF) in Newport News, Virginia, has proposed building a demonstration industrial processing laser for surface treatment and micro-machining. The laser is a free-electron laser (FEL) with average power output exceeding 1 kW in the ultraviolet (UV). The design calls for a novel driver accelerator that recovers most of the energy of the exhaust electron beam to produce laser light with good wall-plug efficiency. The laser and accelerator design use technologies that are scalable to much higher power. The authors will describe the critical design issues in the laser such as the stability, power handling, and losses of the optical resonator, and the quality, power, and reliability of the electron beam. They will also describe the calculated laser performance. Finally progress to date on accelerator development and resonator modeling will be reported

RF Stability in Energy Recovering Free Electron Lasers: Theory and Experiment

Phenomena that result from the interaction of the beam with the rf fields in superconducting cavities, and can potentially limit the performance of high average power Energy Recovery Free Electron Lasers (FELs), are reviewed. These phenomena include transverse and longitudinal multipass, multibunch Beam Breakup, longitudinal beam-loading types of instabilities and their interaction with the FEL, Higher Order Mode power dissipation, emittance growth and energy spread due to short range wakefields, and rf control issues. We present experimental data obtained at the Jefferson Lab IR FEL with average current up to 5 mA, compare with analytic calculations and simulations and extrapolate the performance of Energy Recovery FELs to much higher average currents, up to approximately 100 mA. This work supported by U.S. DOE Contract No. DE-AC05-84ER40150, the Commonwealth of Virginia and the Laser Processing Consortium

Design Principles for a Compact High Average Power IR FEL

Progress in superconducting rf (srf) technology has led to dramatic changes in cryogenic losses, cavity gradients, and microphonic levels. Design principles for a compact high average power Energy Recovery FEL at IR wavelengths, consistent with the state of the art in srf, are outlined, High accelerating gradients, of order 20 MV/m at Q{sub 0}{approx}1x10{sup 10} possible at rf frequencies of 1300 MHz and 1500 MHz, allow for a single-cryomodule linac, with minimum cryogenic losses. Filling every rf bucket, at these high frequencies, results in high average current at relatively low charge per bunch, thereby greatly ameliorating all single bunch phenomena, such as wakefields and coherent synchrotron radiation. These principles are applied to derive self-consistent sets of parameters for 100 kW and 1 MW average power IR FELs and are compared with low frequency solutions. This work supported by U.S. DOE Contract No. DE-AC05-84ER40150, the Commonwealth of Virginia and the Laser Processing Consortium

ISAC and ARIEL: The TRIUMF Radioactive Beam Facilities and the Scientific Program

VII, 284 p. 146 illus.online resource

ARIEL begins a new future in rare isotopes

The superconducting electron linac for ARIEL, TRIUMF’s new flagship facility, has achieved its first accelerated beam

ISAC and ARIEL: the TRIUMF radioactive beam facilities and the scientific program

The TRIUMF Isotope Separator and Accelerator (ISAC) facility uses the isotope separation on-line (ISOL) technique to produce rare-isotope beams (RIB). The ISOL system consists of a primary production beam, a target/ion source, a mass separator, and beam transport system. The rare isotopes produced during the interaction of the proton beam with the target nucleus are stopped in the bulk of the target material. They diffuse inside the target material matrix to the surface of the grain and then effuse to the ion source where they are ionized to form an ion beam that can be separated by mass and then guided to the experimental facilities. Previously published in the journal Hyperfine Interactions

An Electron-Ion Collider at CEBAF

Electron-ion colliders with a center of mass energy between 15 and 100 GeV, a luminosity of at least 10{sup 33}cm{sup -1}s{sup -1}, and a polarization of both beams at or above 80% have been proposed for future studies of hadronic structure. The scheme proposed here would accelerate the electron beam using the CEBAF recirculating linac with energy recovery. If all accelerating structures presently installed in the CEBAF tunnel are replaced by ones with a {approx}20 MV/m gradient, then a single recirculation results in an electron beam energy of about 5 GeV. After colliding with protons/light ions circulating in a figure-of-eight storage ring (for flexibility of spin manipulation) at an energy of up to 100 GeV, the electrons are re-injected into the CEBAF accelerator for deceleration and energy recovery. In this report several lay-out options and their respective feasibilities will be presented and discussed, together with parameters which would provide a luminosity of up to 1 x 10{sup 35} cm{sup -2}s{sup -1}. The feasibility of combining such a collider at a center-of-mass energy [sq rt] s of up to 43 GeV with a fixed target facility of 25 GeV is also explored

Transverse Beam Break-Up Study of the SNS SC Linac

Numerical simulation indicates that cumulative beam breakup (BBU) instability is not a concern to SNS SC linac. First, simulation is carried out for CW operation mode where the driving harmonics are those with frequency multiples of bunch frequency 402.5 MHz. Even when the median HOM frequency is exactly on resonance with multiples of bunch frequency of 402.5 MHz, the cavity-to-cavity HOM frequency spread can ensure operation of linac. Second, in the case of pulsed operation mode, additional driving harmonics of 1 MHz and 60 Hz are added on top of those of CW mode. The shunt impedance of these additional modes is relatively small. BBU is not a concern also for pulsed mode operation, as is verified for a few most dangerous modes. More systematic analysis of BBU of pulsed mode operation is done by Sundelin et al [1] and presented at this conference

First observations and suppression of multipass, multibunch beam breakup in the Jefferson Laboratory free electron laser upgrade

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. Simulation results for Jefferson Lab’s free electron laser (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 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 in 1980 [R. E. Rand and T. I. Smith, Part. Accel. 11, 1 (1980)PLACBD0031-2460], on the threshold current of the FEL. Specifically we consider the effect of (1) reflecting the betatron planes about an axis that is at 45° between the vertical and horizontal axes and (2) rotating the betatron planes by 90°. In two-pass recirculators, a 90° rotation can be effective at increasing the threshold current for 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