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Dark Currents and Their Effect on the Primary Beam in an X-band Linac

Description: We numerically study properties of primary dark currents in an X-band accelerating structure. For the H60VG3 structure considered for the Next Linear Collider (NLC) we first perform a fairly complete (with some approximations) calculation of dark current trajectories. These results are used to study properties of the dark current leaving the structure. For example, at accelerating gradient of 65 MV/m, considering two very different assumptions about dark current emission around the irises, we find that the fraction of emitted current leaving the structure to be a consistent {approx} 1%. Considering that {approx} 1 mA outgoing dark current is seen in measurement, this implies that {approx} 100 mA (or 10 pC per period) is emitted within the structure itself. Using the formalism of the Lienard-Wiechert potentials, we then perform a systematic calculation of the transverse kick of dark currents on a primary linac bunch. The result is {approx} 1 V kick per mA (or per 0.1 pC per period) dark current emitted from an iris. For an entire structure we estimate the total kick on a primary bunch to be {approx} 15 V. For the NLC linac this translates to a ratio of (final) vertical beam offset to beam size of about 0.2. However, with the assumptions that needed to be made--particularly the number of emitters and their distribution within a structure--the accuracy of this result may be limited to the order of magnitude.
Date: May 27, 2005
Creator: Bane, K.L.F.; Dolgashev, V.A.; Raubenheimer, T.; Stupakov, G.V.; Wu, J.H. & /SLAC
Partner: UNT Libraries Government Documents Department

BEAM DYNAMICS FOR A PHOTOINJECTED ENERGY RECOVERY LINAC AT THE NSLS.

Description: The Photoinjected Energy Recovery Linac (PERL) design study at the NSLS is considering the feasibility of a new synchrotron light source based on a 3-7 GeV energy recovering superconducting linac initiated by a photo-injected RF gun [1]. To be a competitive light source the photoinjector must provide high brightness electron beams with a normalized transverse emittance of 0.5-1 mm-mrad and a bunch charge per of 0.15-0.45 nC at a rep rate of 0.43-1.3 GHz. We provide a first pass assessment of some of the beam dynamics issues that are critical to preserving the high brightness beams.
Date: June 18, 2001
Creator: MURPHY,J.B.; BEN-ZVI,I.; TOWNE,N.; WANG,J.M.; WANG,X.J.; WU,J.H. et al.
Partner: UNT Libraries Government Documents Department

THE DUV-FEL DEVELOPMENT PROGRAM

Description: We discuss the design and output radiation parameters for the Deep Ultra-violet Free Electron Laser at BNL, which will generate coherent output down to 100 nm using High Gain Harmonic Generation. The result of FEL calculation and the status of the experiment are presented.
Date: June 18, 2001
Creator: YU,L.H.; DIMAURO,L.F.; DOYURAN,A.; GRAVES,W.; JOHNSON,E.; KRINSKY,S. et al.
Partner: UNT Libraries Government Documents Department

MAXIMA-1: A Measurement of the Cosmic Microwave BackgroundAnisotropy on angular scales of 10' to 5 degrees

Description: We present a map and an angular power spectrum of the anisotropy of the cosmic microwave background (CMB) from the first flight of MAXIMA. MAXIMA is a balloon-borne experiment with an array of 16 bolometric photometers operated at 100 mK. MAXIMA observed a 124 deg region of the sky with 10' resolution at frequencies of 150, 240 and 410 GHz. The data were calibrated using in-flight measurements of the CMB dipole anisotropy. A map of the CMB anisotropy was produced from three 150 and one 240 GHz photometer without need for foreground subtractions. Analysis of this CMB map yields a power spectrum for the CMB anisotropy over the range 36 {le} {ell} {le} 785. The spectrum shows a peak with an amplitude of 78 {+-} 6 {mu}K at {ell} {approx_equal} 220 and an amplitude varying between {approx} 40 {mu}K and {approx} 50 {mu}K for 400 {approx}< {ell} {approx}< 785.
Date: October 2, 2000
Creator: Ade, P.; Balbi, A.; Bock, J.; Borrill, J.; Boscaleri, A.; deBernardis, P. et al.
Partner: UNT Libraries Government Documents Department