Fabrication of DDS-3, an 11.4 GHz damped-detuned structure Page: 3 of 6
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FABRICATION OF DDS-3, AN 11.4 GHz
J. Klingmann, J. Elmer, M. Mugge, K. van Bibber, LLNL, Livermore, CA 94550 USA
K. Asano*, Y. Funahashi, Y. Higashi, T. Higo, N. Hitomi, T. Suzuki, T. Takatomi, N. Toge, Y.
Watanabe, KEK, Tsukuba, Ibaraki 305, Japan
C. Adolphsen, H. Hoag, R. Jones, N. Kroll, R. Miller, C. Pearson, R. Pope, J. Rifkin, R. Ruth, J.
Wang, SLAC, Stanford, CA 94309 USA
Abstract Figure 1: Cross section of the DDS 3 structure.
A 1.8 m X-band Damped-Detuned Structure (DDS-3)
has been fabricated and characterized as part of the
structure development program towards a TeV-scale
e+e- linear collider. In this joint venture, the copper
cells were precision-fabricated by LLNL, diffusion-
bonded into a monolithic structure by KEK, and the
structure completed and tested by SLAC. The overall
process constitutes a baseline for future high-volume
The US-Japan technical baseline for a TeV-scale e+e-
linear collider builds upon a 1.8 m long X-band
accelerator structure for the main linacs. These
structures are of the Damped-Detuned type, whereby
the cell dimensions are varied continuously along the
length in such a way to maintain a uniform 27/3 phase
advance in the accelerating mode at 11.424 GHz, but
distribute the first dipole mode frequencies according
to a broad, smooth function centered around 15 GHz.
Furthermore, the dipole modes excited by off-axis
bunches are effectively coupled out to damping
manifolds, where their energy propagates to
terminations at either end. In this way, the long-range
dipole wakefields may be suppressed. The basic DDS
concepts are discussed in , and an overall summary
of the R&D on Detuned and Damped-Detuned
Structures is found in . This paper will focus mainly
on the production of the 206 different copper cells. The
stacking and two-step bonding of these cells into the
DDS-3 structure is described in detail in . The actual
wakefields of DDS-3 as measured in the SLAC ASSET
facility is reported in . A cross section of the DDS-3
structure is shown in Figure 1.
Input fundamental coupler _ Output fundamental coupler
Input HOM coupler
Output HOM coupler
Now at Akita National College of Technology.
2 CELL FABRICATION
A schematic of the DDS-3 cell is shown with an
isometric rendering in Figure 2. Five dimensions are
specified on the drawing, 'A', 'B', 't', 'H', and 'L',
which vary over the length of the structure. Table 1
shows the dimensions of three cells along the structure
to indicate the magnitudes of the variations. All
dimensions are specified at 20 0C.
Figure 2: Cross-section
and rendering of the DDS-3
2.1 Tolerance Requirements
The axisymmetric features of the DDS-3 cells have
tolerances in the 0.5 to 1.0 micrometer range and
surface finish requirements of less than 500 A Ra. The
primary and secondary datums of the design are the
flat face on the non-cavity side of the cell and the
outside diameter of the cell, respectively. Two
relationships are critical to maintain for proper
performance. The first is parallelism of the two
bonding surfaces to 0.5 micrometer over the diamete r
to prevent a variable "walk" in the straightness of the
structure. The second is 1 micrometer concentricity of
the cavity and iris to the outside diameter, the radial
reference during assembly. The HOM port dimensions
have tolerances in size and position in the 20-
Table 1: DDS -3 Cell Parameters
Cell A B t H L
No. (mm) (mm) (mm) (mm) (mm)
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Adolphsen, C; Asano, K; Elmer, J; Funchasi, Y; Higashi, Y; Higo, T et al. Fabrication of DDS-3, an 11.4 GHz damped-detuned structure, article, March 1, 1999; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc794872/m1/3/: accessed October 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.