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| MPPP030 | Analytic Evaluation of the Series over Azimuthal Harmonics at the Analysis of the Stability of Bunched Beams Coherent Oscillations | impedance, multipole, synchrotron, coupling | 2149 | ||
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At the analysis of the stability of coherent motion of multibunch beams including counterrotating beams) one should deal with expressions analogous to the effective impedance - the serieses over harmonics of revolution frequency of the RF structure impedance at the side frequencies to these harmonics, with certain factors depending on the harmonic number, such as the bunch line density spectrum, the phase factor and the factor describing the order of multipole synchrotron oscillations. In this paper, we present the method for analytic summation of these serieses for resonant impedance, which seems not to be made before in the common case including all mentioned factors. Comparison of obtained expressions with formulae used in previous papers shows the limits of validity of simpler approaches. The obtained expressions are used in the computer codes MBIM1 and MBIM2 presented at this conference, which calculate coherent oscillations stability for arbitrary multibunch beams.
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| TPPT035 | High-Power RF Testing of a 352-MHz Fast-Ferrite RF Cavity Tuner at the Advanced Photon Source | resonance, coupling, photon, klystron | 2407 | ||
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Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under contract No. W-31-109-ENG-38. |
A 352-MHz fast-ferrite rf cavity tuner, manufactured by Advanced Ferrite Technology, was high-power tested on a single-cell copper rf cavity at the Advanced Photon Source. These tests measured the fast-ferrite tuner performance in terms of power handling capability, tuning bandwidth, tuning speed, stability, and rf losses. The test system comprises a single-cell copper rf cavity fitted with two identical coupling loops, one for input rf power and the other for coupling the fast-ferrite tuner to the cavity fields. The fast-ferrite tuner rf circuit consists of a cavity coupling loop, a 6-1/8” EIA coaxial line system with directional couplers, and an adjustable 360° mechanical phase shifter in series with the fast-ferrite tuner. A bipolar DC bias supply, controlled by a low-level rf cavity tuning loop consisting of an rf phase detector and a PID amplifier, is used to provide a variable bias current to the tuner ferrite material to maintain the test cavity at resonance. Losses in the fast-ferrite tuner are calculated from cooling water calorimetry. Test data will be presented. |
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| RPPT011 | Optimized Bunch Compression System for the European XFEL | emittance, space-charge, optics, linac | 1236 | ||
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The European XFEL bunch compressor system has been optimized for greater flexibility in parameter space. Operation beyond the XFEL design parameters is discussed in two directions: achieving the uppermost number of photons in a single pulse on one hand and reaching the necessary peak current for lasing with a pulse as short as possible on the other. Results of start-to-end calculations including 3D-CSR effects, space charge forces and the impact on wake fields demonstrate the potential of the XFEL for further improvement or, respectively, its safety margin for operation at design values.
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| FPAT016 | PASTA – An RF Phase and Amplitude Scan and Tuning Application | linac, SNS, Spallation-Neutron-Source, controls | 1491 | ||
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
To assist the beam commissioning in the Spallation Neutron Source (SNS) linac, a general purpose RF tuning application has been written to help set RF phase and amplitude. It follows the signature matching procedure described in Ref.* The method involves varying an upstream Rf cavity amplitude and phase settings and comparing the measured downstream beam phase responses to model predictions. The model input for cavity phase and amplitude calibration and for the beam energy are varied to best match observations. This scheme has advantages over other RF tuning techniques of not requiring intercepting devices (e.g. Faraday Cups), and not being restricted to a small linear response regime near the design values. The application developed here is general and can be applied to different RF structure types in the SNS linac. Example applications in the SNS Drift Tube Linac (DTL) and Coupled Cavity Linac (CCL) structures will be shown. *T.L. Owens, M.B. Popovic, E.S. McCrory, C.W. Schmidt, L. J. Allen, "Phase Scan Signature Matching for Linac Tuning," Particle Accelerators, 1994 Vol 98, p. 169. |
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| FPAT091 | LiTrack: A Fast Longitudinal Phase Space Tracking Code with Graphical User Interface | linac, focusing, acceleration, electron | 4266 | ||
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Funding: Work supported by U.S. Department of Energy contract DE-AC02-76SF00515. |
Many linear accelerators, such as linac-based light sources and linear colliders, apply longitudinal phase space manipulations in their design, including electron bunch compression and wakefield-induced energy spread control. Several computer codes handle such issues, but most require detailed information on the transverse focusing lattice. In fact, in most linear accelerators, the transverse distributions do not significantly affect the longitudinal, and can be ignored initially. This allows the use of a fast 2D code to study longitudinal aspects without time-consuming considerations of the transverse focusing. LiTrack is based on a 15-year old code (same name) originally written by one of us (KB), which is now a MATLAB-based code with additional features, such as a graphical user interface and output plotting. The single-bunch tracking includes RF acceleration, bunch compression to 3rd order, geometric and resistive wakefields, aperture limits, synchrotron radiation, and flexible output plotting. The code was used to design both the LCLS and the SPPS projects at SLAC and typically runs in <1 minute. We describe the features, show some examples, and provide access to the code. |
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