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Title: Analysis of measured post-coupler fields in a ramped-gradient drift-tube linac

Abstract

Post couplers longitudinally stabilize the axial electric field in a drift-tube linac (DTL) against tuning errors. Displacing the post couplers toward one end of the structure results in a ramped field that increases toward the other end. Such a ramped-gradient DTL is also stable, but some of the cavity power is dissipated on the post couplers to maintain the ramp. This paper reports bead-perturbation measurements of the post-coupler magnetic fields near the tank well. A simple physical model reproduces the measured fields with an accuracy of about 2% and yields current-density distributions on the post couplers in terms of the current density on the cavity wall. The peak power density occurs on the sides of the post couplers where the TM/sub 010/ magnetic field adds to the post-coupler magnetic field. In the Los Alamos Ramped-Gradient DTL (RGDTL), the peak power densities on post couplers located in the steepest part of the ramp exceed by more than 10 times the maximum power density on the tank wall far from any post couplers. Methods to reduce such power losses to levels comparable to a flat-gradient DTL will be discussed. 2 refs. , 6 figs., 1 tab.

Authors:
Publication Date:
Research Org.:
Los Alamos National Lab., NM (USA)
OSTI Identifier:
6807935
Alternate Identifier(s):
OSTI ID: 6807935; Legacy ID: DE89000343
Report Number(s):
LA-UR-88-3248; CONF-881049-13
ON: DE89000343
DOE Contract Number:
AC04-76DP00789
Resource Type:
Conference
Resource Relation:
Conference: Linear accelerator conference, Williamsburg, VA, USA, 3 Oct 1988; Other Information: Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; LINEAR ACCELERATORS; MAGNETIC FIELDS; CURRENT DENSITY; DESIGN; EXPERIMENTAL DATA; FREQUENCY MEASUREMENT; TUNING; ACCELERATORS; DATA; INFORMATION; NUMERICAL DATA 430200* -- Particle Accelerators-- Beam Dynamics, Field Calculations, & Ion Optics

Citation Formats

Billen, J.H. Analysis of measured post-coupler fields in a ramped-gradient drift-tube linac. United States: N. p., 1988. Web.
Billen, J.H. Analysis of measured post-coupler fields in a ramped-gradient drift-tube linac. United States.
Billen, J.H. Fri . "Analysis of measured post-coupler fields in a ramped-gradient drift-tube linac". United States. doi:. https://www.osti.gov/servlets/purl/6807935.
@article{osti_6807935,
title = {Analysis of measured post-coupler fields in a ramped-gradient drift-tube linac},
author = {Billen, J.H.},
abstractNote = {Post couplers longitudinally stabilize the axial electric field in a drift-tube linac (DTL) against tuning errors. Displacing the post couplers toward one end of the structure results in a ramped field that increases toward the other end. Such a ramped-gradient DTL is also stable, but some of the cavity power is dissipated on the post couplers to maintain the ramp. This paper reports bead-perturbation measurements of the post-coupler magnetic fields near the tank well. A simple physical model reproduces the measured fields with an accuracy of about 2% and yields current-density distributions on the post couplers in terms of the current density on the cavity wall. The peak power density occurs on the sides of the post couplers where the TM/sub 010/ magnetic field adds to the post-coupler magnetic field. In the Los Alamos Ramped-Gradient DTL (RGDTL), the peak power densities on post couplers located in the steepest part of the ramp exceed by more than 10 times the maximum power density on the tank wall far from any post couplers. Methods to reduce such power losses to levels comparable to a flat-gradient DTL will be discussed. 2 refs. , 6 figs., 1 tab.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 01 00:00:00 EST 1988},
month = {Fri Jan 01 00:00:00 EST 1988}
}

Conference:
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