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Title: Room Temperature Accelerator Structures for Linear Colliders

Abstract

Early tests of short low group velocity and standing wave structures indicated the viability of operating X-band linacs with accelerating gradients in excess of 100 MeV/m. Conventional scaling of traveling wave traveling wave linacs with frequency scales the cell dimensions with {lambda}. Because Q scales as {lambda}{sup 1/2}, the length of the structures scale not linearly but as {lambda}{sup 3/2} in order to preserve the attenuation through each structure. For NLC we chose not to follow this scaling from the SLAC S-band linac to its fourth harmonic at X-band. We wanted to increase the length of the structures to reduce the number of couplers and waveguide drives which can be a significant part of the cost of a microwave linac. Furthermore, scaling the iris size of the disk-loaded structures gave unacceptably high short range dipole wakefields. Consequently, we chose to go up a factor of about 5 in average group velocity and length of the structures, which increases the power fed to each structure by the same factor and decreases the short range dipole wakes by a similar factor. Unfortunately, these longer (1.8 m) structures have not performed nearly as well in high gradient tests as the short structures. Wemore » believe we have at least a partial understanding of the reason and will discuss it below. We are now studying two types of short structures with large apertures with moderately good efficiency including: (1) traveling wave structures with the group velocity lowered by going to large phase advance per period with bulges on the iris, (2){pi} mode standing wave structures.« less

Authors:
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Energy Research (ER) (US)
OSTI Identifier:
787225
Report Number(s):
SLAC-PUB-8889
TRN: US0110492
DOE Contract Number:  
AC03-76SF00515
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 10 Sep 2001
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; APERTURES; DIPOLES; HARMONICS; LINEAR COLLIDERS; STANDING WAVES; WAVEGUIDES; DESIGN; X RADIATION; TRAVELLING WAVES

Citation Formats

Miller, Roger H. Room Temperature Accelerator Structures for Linear Colliders. United States: N. p., 2001. Web. doi:10.2172/787225.
Miller, Roger H. Room Temperature Accelerator Structures for Linear Colliders. United States. https://doi.org/10.2172/787225
Miller, Roger H. Mon . "Room Temperature Accelerator Structures for Linear Colliders". United States. https://doi.org/10.2172/787225. https://www.osti.gov/servlets/purl/787225.
@article{osti_787225,
title = {Room Temperature Accelerator Structures for Linear Colliders},
author = {Miller, Roger H},
abstractNote = {Early tests of short low group velocity and standing wave structures indicated the viability of operating X-band linacs with accelerating gradients in excess of 100 MeV/m. Conventional scaling of traveling wave traveling wave linacs with frequency scales the cell dimensions with {lambda}. Because Q scales as {lambda}{sup 1/2}, the length of the structures scale not linearly but as {lambda}{sup 3/2} in order to preserve the attenuation through each structure. For NLC we chose not to follow this scaling from the SLAC S-band linac to its fourth harmonic at X-band. We wanted to increase the length of the structures to reduce the number of couplers and waveguide drives which can be a significant part of the cost of a microwave linac. Furthermore, scaling the iris size of the disk-loaded structures gave unacceptably high short range dipole wakefields. Consequently, we chose to go up a factor of about 5 in average group velocity and length of the structures, which increases the power fed to each structure by the same factor and decreases the short range dipole wakes by a similar factor. Unfortunately, these longer (1.8 m) structures have not performed nearly as well in high gradient tests as the short structures. We believe we have at least a partial understanding of the reason and will discuss it below. We are now studying two types of short structures with large apertures with moderately good efficiency including: (1) traveling wave structures with the group velocity lowered by going to large phase advance per period with bulges on the iris, (2){pi} mode standing wave structures.},
doi = {10.2172/787225},
url = {https://www.osti.gov/biblio/787225}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2001},
month = {9}
}