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Response of the Saver Dipole Beam Tube to single-phase helium pressure

Description: One Energy Saver Dipole Beam Tube (No. MB 124211) was tested under static and pulsed pressure conditions. Under static pressure, permanent deformation started at about 125 psi and reached .006 inches across flats after 220 psi exposure. Final catastrophic collapse occurred at 325 psi. Pressure pulses of shape and duration approximating the single phase helium pressure during a full house quench had no effect on the tube (previously staticly pressurized to 220 psi) up to 285 psi and a slight yield effect at 305 psi. Repeated pulses at 305 psi appeared to cause little or no further yielding. When compared to static pressure effects the 305 psi pulse produced the same deflection as about 235 psi static pressure.
Date: January 19, 1983
Creator: Biallas, G. & Barner, D.
Partner: UNT Libraries Government Documents Department

Super magnets for interaction regions

Description: The feasibility of using superconducting magnets in the beam interaction regions of particle accelerators is discussed. These higher field magnets can be shorter, leaving more room for detectors, but also must have a large aperture and magnetic shielding. The ''kissing geometry'' was investigated, and design and scaling considerations are given. A rough estimate of the cost of such superconducting magnets is given as an aid to the selection of interaction geometry. (PMA)
Date: January 1, 1977
Creator: Biallas, G.; Fowler, W. & Diebold, R.
Partner: UNT Libraries Government Documents Department

Magnetic measurements of the prototype dipole for the IR-FEL at the Thomas Jefferson National Accelerator Facility

Description: Magnetic measurements have been performed on the prototype dipole for the high power IR-FEL presently under construction at the Thomas Jefferson National Accelerator Facility. The optics-driven requirements for these magnets include low fields, large horizontal apertures, tight field homogeneity, absolute setability of core field & integrated field, and control of the horizontal & vertical focusing terms designed into the magnets. A prototype dipole was fabricated and underwent several iterations of mechanical adjustment and magnetic measurement. Measurements were made to quantify the effects of field clamps on vertical focusing terms and effective length. Additional tests were made using various applications of Purcell gaps and high permeability materials in order to achieve the required homogeneity. Results from the prototype have been integrated into the design of the seven families of dipoles needed for the FEL.
Date: June 1, 1997
Creator: Karn, J.; Biallas, G.; Guerra, A. & Harwood, L.
Partner: UNT Libraries Government Documents Department

Making dipoles to spectrometer quality using adjustments during measurement

Description: Twenty-seven window frame dipole magnets requiring spectrometer-like fields were made for the IR-FEL at the Thomas Jefferson National Accelerator Facility. These magnets incorporate Purcell gaps, {mu} metal pole faces and adjustable field clamps. After outlining their specifications, this paper describes the processes used in magnet manufacturing, the program of magnetic mapping used, as well as adjustments made to meet tight optics-driven requirements. Described are the measurements made to quantify fringe fields, verify field homogeneity, map core and integrated field as a function of current, and characterize the horizontal and vertical focusing terms designed into the dipoles. Also described are the techniques that were successfully used to tune individual magnets to meet the tight tolerancing of all these parameters.
Date: April 1, 1999
Creator: Biallas, G.; Bullard, D. & Douglas, D.
Partner: UNT Libraries Government Documents Department

First results on energy recovery in the Jefferson Lab IR FEL

Description: A recirculating, energy-recovery linac is used as a driver accelerator for Jefferson Lab's high average power FEL. CW beam of 5 mA design current is transported from the superconducting RF (SRF) linac to the wiggler for lasing, and then recirculated back to the linac for deceleration and energy recovery. About 75% of the beam power is extracted before the beam is transported to the beam dump. Energy recovery reduces power consumption, RF equipment capital costs, and beam dump shielding requirements. It is arguably essential as FEL technology is scaled to higher average power levels. To date 4 mA of CW beam has been energy recovered successfully. There is no evidence of RF instabilities due to the energy aperture of the transport system, momentum compaction or the phase of the decelerating beam. HOM power from the beam has interfered with the operation of the IR interlock detectors, designed to protect the warm waveguide window from thermal runaway. Installation of copper screens appears to have solved the problem. More detailed studies of the HOM spectra and their correlation to the beam properties are planned.
Date: August 1, 1999
Creator: Benson, S.; Biallas, G. & Bohn, C.L.
Partner: UNT Libraries Government Documents Department

Magnetic measurement of the pi bend dipole magnets for the IR-FEL at the Thomas Jefferson National Accelerator Facility

Description: A family of large bending dipoles has been successfully magnetically measured, installed and is operational in the high power IR-FEL. These magnets are unique in that they bend the beam 180 {degree} on a 1 meter radius. The optics requirements for the magnets include low fields, large horizontal apertures, tight field homogeneity, high repeatability of core field and integrated field, and control of the horizontal and vertical focusing terms that are designed into the magnets. Quantifying the optics requirements proved to be a difficult task, due to the magnet's mechanical construction and sharp bending radius. The process involved in measuring and achieving the results are discussed.
Date: April 1, 1999
Creator: Biallas, G.; Douglas, D.; Karn, J. & Tremblay, K.
Partner: UNT Libraries Government Documents Department

Experimental results from an injector for an IR FEL

Description: An electron injector capable of delivering the high brightness electron beam necessary for an infrared free-electron laster (FEL) is described. The injector is composed of a high-DC-voltage GaAs photocathode gun coupled with a normal-conducting rf buncher and two superconducting rf cavities operating at 1.497 GHz. The gun pulse structure is mode locked to the fortieth subharmonic of the rf fundamental using a Nd:YLF drive laser. The gun provides 50 picosecond FWHM bunches at 60 pC per bunch with a normalized RMS transverse emittance less than 6 mmmrad at 9.5 MeV/c and an average current of 1.1 mA. Experimental measurements of the transverse and longitudinal beam properties of the injector are described. The results are compared with PARMELA. Operational issues for the injector are also presented.
Date: June 1, 1998
Creator: Piot, P.; Biallas, G. & Bohn, C.L.
Partner: UNT Libraries Government Documents Department

Performance of the accelerator driver of Jefferson Laboratory's free-electron laser

Description: The driver of Jefferson Lab's kW-level infrared free-electron laser (FEL) is a superconducting, recirculating accelerator that recovers about 75% of the electron-beam power and converts it to radiofrequency power. In achieving first lasing, the accelerator operated straight-ahead to deliver 38 MeV, 1.1 mA cw current through the wiggler for lasing at wavelengths in the vicinity of 5 {mu}m. Just prior to first lasing, measured rms beam properties at the wiggler were 7.5{+-}1.5 mm-mr normalized transverse emittance, 26{+-}7 keV-deg longitudinal emittance, and 0.4{+-}0.1 ps bunch length which yielded a peak current of 60{+-}15A. The waste beam was then sent directly to a dump, bypassing the recirculation loop. Stable operation at up to 311 W cw was achieved in this mode. Commissioning the recirculation loop then proceeded. As of this Conference, the machine has recirculated cw average current up to 4 mA, and has lased cw with energy recover up to 710 W.
Date: April 1, 1999
Creator: Bohn, C.L.; Benson, S. & Biallas, G.
Partner: UNT Libraries Government Documents Department

RF device for precision location of the beam-position detectors in the Energy Saver

Description: The task is to measure the center line of the beam detector with respect to the magnetic centerline with a precision of +-0.2 mm; the measurement must be made on 250 magnets (they come in 6 lengths, from 25'' to 99'') by a technician. Optical, mechanical, and electrical techniques for carrying out this procedure were considered. An RF device operating at 53 MHZ was adopted for the following reasons: (a) it provides complete electrical checkout of the hardware at operating frequency, including the bidirectional operation of the pickup, (b) no mechanical contact with the strip lines is required, and (c) the demands of production measurements and maintenance of calibration are better matched to the skills of an average technician. We describe the conceptual design, fabrication, and performance of this device.
Date: March 1, 1983
Creator: Kerns, Q.A.; Biallas, G.H.; Turkot, F.; Webber, R.C. & Wehmann, A.
Partner: UNT Libraries Government Documents Department

Fermilab Tevatron I project target station for antiproton production

Description: Production of 8-GeV antiprotons in the Fermilab Tevatron I project will utilize 120-GeV protons from the Main Ring. The Target Station consists of an entrance collimator, the target itself, a pulsed lithium lens for anti proton collection, a pulsed magnet for the separation of the 8-GeV secondaries, and a beam dump. These components are mounted on vertical modules within the Target Service Building. Allowance has been made for future improvements to increase the collected anti proton flux. The design of the Target Station and its components is discussed.
Date: March 1, 1983
Creator: Hojvat, C.; Biallas, G.; Hanson, R.; Heim, J. & Lange, F.
Partner: UNT Libraries Government Documents Department

A method of producing very high resistivity surface conduction on ceramic accelerator components using metal ion implantation

Description: An important technique used for the suppression of surface flashover on high voltage DC ceramic insulators as well as for RF windows is that of providing some surface conduction to bleed off accumulated surface charge. The authors have used metal ion implantation to modify the surface of high voltage ceramic vacuum insulators to provide a uniform surface resistivity of approximately 5 x 10{sup 10} Q{sup 2}. A vacuum arc ion source based implanter was used to implant Pt at an energy of about 135 MeV to doses of up to more than 5 x 10{sup 16} ions cm{sup 2} into small ceramic test coupons and also into the inside surface of several ceramic accelerator columns 25 cm I. D. by 28 cm long. Here they describe the experimental set-up used to do the ion implantation and summarize the results of their exploratory work on implantation into test coupons as well as the implantations of the actual ceramic columns.
Date: May 1, 1997
Creator: Liu, F.; Brown, I.; Phillips, L.; Biallas, G. & Siggins, T.
Partner: UNT Libraries Government Documents Department

Power tests of the Fermilab Lithium Lens for antiproton collection

Description: A prototpye Lithium Lens to be used for the collection of antiprotons in the Fermilab Tevatron I project has been constructed. Some of the fabrication details, the procedure for lithium filling and the results of the initial operation are discussed.
Date: August 1, 1983
Creator: Biallas, G.; Dugan, G.; Hangst, J.; Hanson, R.; Hojvat, C.; Lange, F. et al.
Partner: UNT Libraries Government Documents Department

Mechanical and electrical design of the Fermilab lithium lens and transformer system

Description: A lithium-lens focusing device will be used for the collection of 8-GeV antiprotons in the Fermilab Tevatron I Project. The details of the mechanical and electrical design of the Fermilab lens and its associated toroidal transformer are discussed. The lens, with a radium of 1 cm and length 15 cm, is expected to achieve gradients of 1000 T/m for a focal distance of 0.225 m. The gradient requires a current on the order of 5 x 10/sup 5/A, resulting in large electromagnetic and thermal stresses. The power-supply discharge current and the effect of the inductance of the power leads and connections are minimized by the use of a toroidal matching transformer surrounding the lens itself.
Date: March 1, 1983
Creator: Dugan, G.; Hojvat, C.; Lennox, A.J.; Biallas, G.; Cilyo, F.; Leininger, M. et al.
Partner: UNT Libraries Government Documents Department

Second Harmonic FEL Oscillation

Description: We have produced and measured for the first time second harmonic oscillation in the infrared region by the high average power Jefferson Lab Infrared Free Electron Laser. Although such lasing is ideally forbidden, since gain is zero on axis for a perfect electron beam in an infinite wiggler, the finite geometry and beam emittance allows sufficient gain for lasing to occur. We were able to lase at pulse rates up to 74.85 MHz and could produce over 4.5 watts average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM01 mode. We present results of initial source performance measurements and comparisons of gain as calculated by different approaches.
Date: September 1, 2001
Creator: Neil, George R.; Benson, S.V.; Biallas, G.; Freund, H.P.; Gubeli, J.; Jordan, K. et al.
Partner: UNT Libraries Government Documents Department

Lasing in Forbidden Regions: Second Harmonic FEL Oscillation

Description: We have produced and measured for the first time second harmonic oscillation in the infrared region by the high average power Jefferson Lab Infrared Free Electron Laser. Although such lasing is ideally forbidden, since gain is zero on axis for a perfect electron beam in an infinite wiggler, the finite geometry allows sufficient gain in this situation for lasing to occur. We were able to lase at pulse rates up to 74.85 MHz and could produce over 4.5 watts average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM-01 mode. We present results of initial source performance measurements and comparisons of gain as calculated by different approaches.
Date: March 1, 2001
Creator: Neil, G.R.; Benson, S.V.; Biallas, G.; Gubeli, J.; Jordan, K.; Myers, S. et al.
Partner: UNT Libraries Government Documents Department

A kilowatt average power laser for sub-picosecond materials processing

Description: The performance of laser pulses in the sub-picosecond range for materials processing is substantially enhanced over similar fluences delivered in longer pulses. Recent advances in the development of solid state lasers have progressed significantly toward the higher average powers potentially useful for many applications. Nonetheless, prospects remain distant for multi-kilowatt sub-picosecond solid state systems such as would be required for industrial scale surface processing of metals and polymers. The authors present operational results from the world's first kilowatt scale ultra-fast materials processing laser. A Free Electron Laser (FEL) called the IR Demo is operational as a User Facility at Thomas Jefferson National Accelerator Facility in Newport News, Virginia, USA. In its initial operation at high average power it is capable of wavelengths in the 2 to 6 micron range and can produce {approximately}0.7 ps pulses in a continuous train at {approximately}75 MHz. This pulse length has been shown to be nearly optimal for deposition of energy in materials at the surface. Upgrades in the near future will extend operation beyond 10 kW CW average power in the near IR and kilowatt levels of power at wavelengths from 0.3 to 60 microns. This paper will cover the design and performance of this groundbreaking laser and operational aspects of the User Facility.
Date: November 1, 1999
Creator: Benson, Stephen V.; Neil, George R.; Bohn, C.; Biallas, G.; Douglas, D.; Dylla, F. et al.
Partner: UNT Libraries Government Documents Department

First operation of an FEL in same-cell energy recovery mode

Description: The driver for Jefferson Lab's kW-level infrared free-electron laser (FEL) is a superconducting, recirculating accelerator that recovers 75% of the electron-beam power and converts it to radio frequency power. As reported in FEL'98, the accelerator operated ''straight-ahead'' to deliver 38 MeV, 1.1 mA cw current for lasing at wavelengths in the vicinity of 5 microns. The waste beam was sent directly to a dump, bypassing the recirculation loop. Stable operation at up to 311 W cw was achieved in this mode. The machine has now recirculated cw average current up to 4.6 mA and has lased cw with energy recovery up to 1,720 W output at 3.1 microns. This is the first FEL to ever operate in the ''same-cell'' energy recovery mode. Energy recovery offers several advantages (reduced RF power and dramatically reduced radio-nuclide production at the dump) and several challenges will be described. The authors have observed heating effects in the mirrors which will be described. They will also report on the additional performance measurements of the FEL that have been performed and connect those measurements to standard models.
Date: September 1, 1999
Creator: Neil, G.R.; Benson, S.; Biallas, G.; Bohn, C.L.; Douglas, D.; Dylla, H.F. et al.
Partner: UNT Libraries Government Documents Department

Sustained Kilowatt Lasing in a Free-Electron Laser with Same Cell Energy Recovery

Description: TJNAF recently commissioned its high-average-power infrared free-electron laser (FEL). It incorporates a superconducting accelerator that recovers about 75% of the electron-beam power and converts it to radio-frequency power. In achieving first lasing, the accelerator operated straight-ahead to deliver 38 MeV, 1.1 mA cw average current through the wiggler for lasing at wavelengths near 5 {micro}m. The waste beam was then sent directly to a dump. Stable operation at up to 311 W cw was achieved in this mode. Using a transport loop to send the waste electron beam back to the linac for energy recovery, the machine recently lased cw at up to 1720 W average power at 3.1 {micro}m, for which the electron-beam energy and average current were 48 MeV and 4.4 mA, respectively.
Date: September 1, 1999
Creator: Neil, G.R.; Benson, S.; Biallas, G.; Bohn, C.L.; Douglas, D.; Dylla, H.F. et al.
Partner: UNT Libraries Government Documents Department

Status of the Jefferson Lab IR/UV High Average Power Light Source

Description: Jefferson Lab is in the process of building an upgrade to our Free-Electron Laser Facility with broad wavelength range and timing flexibility. The facility will have two cw free-electron lasers, one in the infrared operating from 1 to 14 microns and one in the infrared operating from 0.25 to 1 micron [1]. In addition, there will be beamlines for Thompson-backscattered femtosecond X-rays, and broadband THz radiation. The average power levels for each of these devices will exceed any other available sources by at least 2 orders of magnitude. Timing of the available laser pulses can be continuously mode-locked at least 4 different (MHz) repetition rates or in macropulse mode with pulses of a few microseconds in duration with a repetition rate of many kHz. The status of the construction of this facility and a review of its capabilities will be presented.
Date: September 2002
Creator: Neil, G. R.; Benson, S. V.; Biallas, G.; Boyce, J.; Dillon-Townes, L. A.; Douglas, D. et al.
Partner: UNT Libraries Government Documents Department