Fast wire scanner for intense electron beams

Moore, T.; Agladze, N. I.; Bazarov, Ivan; Bartnik, Adam; Dobbins, John; Dunham, Bruce; Full, Steve; Li, Y.; Liu, X.; Savino, J.; Smolenski, K.

doi:10.1103/physrevstab.17.022801

Cited by 6 publications

(4 citation statements)

References 9 publications

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“…In SwissFEL the wire-fork is indeed motorized by a 2-phase stepper motor which may excite possible low frequency vibration eigenmodes of the wire. According to the experience of several FEL and x-ray facilities such as FLASH and LCLS [9,10,12,13,22], carbon wires are normally preferred to tungsten wires wherever the risk of radiation damage can be a critical issue and/or whenever accuracy and precision are not relevant to a WSC measurement (WSC as a beam-finder). On the other hand, carbon wires are quite rigid and fragile and thus more susceptible than metallic wires to a breaking risk because of an anomalous vibration of the wire-fork.…”

Section: Design Of the Swissfel Wire Scannersmentioning

confidence: 99%

Design and experimental tests of free electron laser wire scanners

Orlandi

Heimgartner

Ischebeck

et al. 2016

Phys. Rev. Accel. Beams

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SwissFEL is a x-rays free electron laser (FEL) driven by a 5.8 GeV linac under construction at Paul Scherrer Institut. In SwissFEL, wire scanners (WSCs) will be complementary to view-screens for emittance measurements and routinely used to monitor the transverse profile of the electron beam during FEL operations. The SwissFEL WSC is composed of an in-vacuum beam-probe-motorized by a stepper motor-and an out-vacuum pickup of the wire signal. The mechanical stability of the WSC in-vacuum hardware has been characterized on a test bench. In particular, the motor induced vibrations of the wire have been measured and mapped for different motor speeds. Electron-beam tests of the entire WSC setup together with different wire materials have been carried out at the 250 MeV SwissFEL Injector Test Facility (SITF, Paul Scherrer Institut, CH) and at FERMI (Elettra-Sincrotrone Trieste, Italy). In particular, a comparative study of the relative measurement accuracy and the radiation-dose release of Alð99Þ∶Sið1Þ and tungsten (W) wires has been carried out. On the basis of the outcome of the bench and electron-beam tests, the SwissFEL WSC can be qualified as a high resolution and machine-saving diagnostic tool in consideration of the mechanical stability of the scanning wire at the micrometer level and the choice of the wire material ensuring a drastic reduction of the radiation-dose release with respect to conventional metallic wires. The main aspects of the design, laboratory characterization and electron beam tests of the SwissFEL WSCs are presented.

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Section: Design Of the Swissfel Wire Scannersmentioning

confidence: 99%

Design and experimental tests of free electron laser wire scanners

Orlandi

Heimgartner

Ischebeck

et al. 2016

Phys. Rev. Accel. Beams

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“…For photon beams, fast photodiodes can be used, for charged particles, scintillators with photomultipliers (see, e.g., Ref. 6), and for neutrons, wires covered by gadolinium layer, 2 etc. We note that for particle beam profiling, special types of photodiodes (such as diamond-based detectors) can be also used.…”

Section: Discussionmentioning

confidence: 99%

Fast resonant target vibrating wire scanner for photon beam

Arutunian

Chung

Harutyunyan

et al. 2016

Review of Scientific Instruments

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We propose a new type of wire scanner for beam profile measurements, based on the use of a vibrating wire as a scattering target. Synchronous measurements with the wire oscillation allow to detect only the signal coming from the scattering of the beam on the wire. This resonant method enables fast beam profiling in the presence of a high level of background. The developed wire scanner, called resonant target vibrating wire scanner, is applied to photon beam profiling, in which the photons reflected on the wire are measured by a fast photodiode. In addition, the proposed measurement principle is expected to monitor other types of beams as well, such as neutrons, protons, electrons, and ions.

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“…In the future, we would like to continue these experiments with a new beam profile monitor capable of operating at high beam current [10]. This diagnostic is currently undergoing bench testing and should be available soon.…”

Section: Discussionmentioning

confidence: 99%

“…Additionally, because the photoinjector is a low energy linac, we are unable to use synchrotron or diffraction radiation to take measurements. Our best option, a fast beam profile monitor recently developed at Cornell for use in high intensity accelerators [10], was unfortunately not available for use at the time of these experiments.…”

Section: Methodsmentioning

confidence: 99%

Detection and clearing of trapped ions in the high current Cornell photoinjector

Full

Bartnik

Bazarov

et al. 2016

Phys. Rev. Accel. Beams

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We have recently performed experiments to test the effectiveness of three ion-clearing strategies in the Cornell high intensity photoinjector: DC clearing electrodes, bunch gaps, and beam shaking. The photoinjector reaches a new regime of linac beam parameters where high CW beam currents lead to ion trapping. Therefore ion mitigation strategies must be evaluated for this machine and other similar future high current linacs. We have developed several techniques to directly measure the residual trapped ions. Our two primary indicators of successful clearing are the amount of ion current removed by a DC clearing electrode, and the absence of bremsstrahlung radiation generated by beam-ion interactions. Measurements were taken for an electron beam with an energy of 5 MeV and CW beam currents in the range of 1-20 mA. Several theoretical models have been developed to explain our data. Using them, we are able to estimate the clearing electrode voltage required for maximum ion clearing, the creation and clearing rates of the ions while employing bunch gaps, and the sinusoidal shaking frequency necessary for clearing via beam shaking. In all cases, we achieve a maximum ion clearing of at least 70 percent or higher, and in some cases our data is consistent with full ion clearing.

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Fast wire scanner for intense electron beams

Cited by 6 publications

References 9 publications

Design and experimental tests of free electron laser wire scanners

Design and experimental tests of free electron laser wire scanners

Fast resonant target vibrating wire scanner for photon beam

Detection and clearing of trapped ions in the high current Cornell photoinjector

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