LINAC2016 - List of Authors (Suzuki, S.)

Paper	Title	Page
THPLR015	Fifth-Order Moment Correction for Beam Position and Second-Order Moment Measurement	876
	K. Yanagida, H. Hanaki, S. Suzuki JASRI/SPring-8, Hyogo-ken, Japan
	For precise beam position measurement using a beam position monitor (BPM), a recursive correction which is expressed by the higher-order polynomials of beam positions are usually adopted. We recognized that the higher-order polynomials came from the higher-order moments and that beam position measurement is consequently influenced by a transverse beam shape. To investigate what order was required for adequate correction, we performed a successive iteration for the six-electrode BPM holding an inner radius of 16mm (circular cross-section). The successive iteration is a method to obtain a self-consistent solution for the higher-order correction. An amplitude of static electric field due to a beam charge was calculated by two-dimensional mirror charge method. As a result of the successive iteration, the convergence region was large enough for ordinary measurements (from lower than -5mm to higher than 5mm horizontally and vertically). In the convergence region the root mean square of the differences between the set and calculated vertical position were obtained as 0.487mm (without correction), 0.030mm (with third-order correction) and 0.003mm (with fifth-order correction).
	Poster THPLR015 [6.049 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR015
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THPLR021	Identification of Emitting Sources of Dark Currents From Gridded Thermionic Electron Gun and Measures to Suppress Dark Currents From Electron Gun in SPring-8 Linear Accelerator	888
	T. Magome, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi JASRI/SPring-8, Hyogo-ken, Japan
	The dark current is emitted from a gridded thermionic electron gun although the grid-electrode potential against the cathode is negative enough to suppress the cathode emission current. This dark current in the SPring-8 linear accelerator caused satellite bunches unignorable for precise experiments in the downstream electron storage ring. The dark current has been investigated by means of our electron-gun test equipment applying a DC accelerator voltage to the electron gun. The investigations revealed that the dark current was generated from the wehnelt electrode, the gird electrode, and the cathode surface. The dark current from the wehnelt electrode was decreased under the measurement limit 2·10^-15 A by replacing the wehnelt and the anode electrodes with new electro-polished ones. The dark current from the cathode surface was reduced by lowering the grid-electrode potential against the cathode down to -160 V. To reduce the dark current from the grid electrode, the surface of the grid electrode was significantly smoothed by electro-polishing.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Fifth-Order Moment Correction for Beam Position and Second-Order Moment Measurement

876

K. Yanagida, H. Hanaki, S. Suzuki
JASRI/SPring-8, Hyogo-ken, Japan

For precise beam position measurement using a beam position monitor (BPM), a recursive correction which is expressed by the higher-order polynomials of beam positions are usually adopted. We recognized that the higher-order polynomials came from the higher-order moments and that beam position measurement is consequently influenced by a transverse beam shape. To investigate what order was required for adequate correction, we performed a successive iteration for the six-electrode BPM holding an inner radius of 16mm (circular cross-section). The successive iteration is a method to obtain a self-consistent solution for the higher-order correction. An amplitude of static electric field due to a beam charge was calculated by two-dimensional mirror charge method. As a result of the successive iteration, the convergence region was large enough for ordinary measurements (from lower than -5mm to higher than 5mm horizontally and vertically). In the convergence region the root mean square of the differences between the set and calculated vertical position were obtained as 0.487mm (without correction), 0.030mm (with third-order correction) and 0.003mm (with fifth-order correction).

Poster THPLR015 [6.049 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR015

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPLR021

Identification of Emitting Sources of Dark Currents From Gridded Thermionic Electron Gun and Measures to Suppress Dark Currents From Electron Gun in SPring-8 Linear Accelerator

888

T. Magome, H. Hanaki, T. Kobayashi, S. Suzuki, T. Taniuchi
JASRI/SPring-8, Hyogo-ken, Japan

The dark current is emitted from a gridded thermionic electron gun although the grid-electrode potential against the cathode is negative enough to suppress the cathode emission current. This dark current in the SPring-8 linear accelerator caused satellite bunches unignorable for precise experiments in the downstream electron storage ring. The dark current has been investigated by means of our electron-gun test equipment applying a DC accelerator voltage to the electron gun. The investigations revealed that the dark current was generated from the wehnelt electrode, the gird electrode, and the cathode surface. The dark current from the wehnelt electrode was decreased under the measurement limit 2·10^-15 A by replacing the wehnelt and the anode electrodes with new electro-polished ones. The dark current from the cathode surface was reduced by lowering the grid-electrode potential against the cathode down to -160 V. To reduce the dark current from the grid electrode, the surface of the grid electrode was significantly smoothed by electro-polishing.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)