| Paper | Title | Page |
|---|
| WE206 | First test results of half-reentrant single-cell superconducting cavities | 407 |
| | - M. Meidlinger, J. Bierwagen, S. Bricker, C. Compton, T. Grimm, W. Hartung, M. Johnson, J. Popielarski, L. Saxton, R. York
National Superconducting Cyclotron Laboratory - P. Kneisel
TJNAF - E. Zaplatin
Forschungszentrum Julich
| |
| | Particle physicists are on the verge of reaching a new
frontier of physics, the Terascale, named for the teravolts
of kinetic energy per particle required to explore this region.
To meet the demand for more beam energy, superconducting
cavities need to achieve higher accelerating gradients.
It is anticipated that niobium cavities will reach a
performance limit as the peak surface magnetic field approaches
the critical magnetic field. "Low-loss" [1] and
"reentrant" [2] cavity designs are being studied at CEBAF,
Cornell, DESY, and KEK, with the goal of reaching higher
gradients via lower surface magnetic field, at the expense
of higher surface electric field. At present, cavities must
undergo chemical etching and high-pressure water rinsing
to achieve good performance. While these surface treatment
methods have been effective for low-loss and reentrant
single-cell cavity designs, it is not clear whether the
same methods will be adequate for multi-cell versions.
A "half-reentrant" cavity shape has been designed with
RF parameters similar to the low-loss and reentrant cavities,
but with the advantage that the same surface preparation
should be reliable for multi-cell half-reentrant cavities.
Two 1.3 GHz prototype single-cell half-reentrant cavities
have been fabricated and tested at Michigan State University
(MSU). One of the cavities was post-purified, etched
via buffered chemical polishing, and tested at Thomas Jefferson
National Accelerator Facility (TJNAF), reaching a
maximum accelerating gradient of 35 MV/m. The halfreentrant
cavity concept, design, fabrication, and first test
results are presented. | |
 | Slides(PDF) | |
| WEP01 | Studies of alternative techniques for niobium cavity fabrication | 429 |
| | - C. Compton, D. Baars, T. Bieler, J. Bierwagen, S. Bricker, W. Hartung, D. Pendell, R. York
Michigan State University - L. Cooley, H. Jiang, B. Kephart
Fermilab
| |
| | Alternative fabrication techniques for superconducting
radio frequency (SRF) cavities are being investigated.
The main goals are to reduce cavity fabrication costs and
expand possibilities for advanced cavity designs. At
present, SRF cavities are fabricated via deep drawing of
parts from sheet material and electron beam welding
(EBW) to join the parts together. EBW produces welds of
high quality, but the procedures are costly and timeconsuming.
Alternative technologies being explored
include tungsten inert gas (TIG) welding of Nb,
hydroforming of Nb, and electron-beam free form
fabrication (EBFFF) of Nb. If techniques can be
developed which do not degrade the Nb purity, TIG
welding could reduce or eliminate the need for EBW.
Hydroforming could also be an alternative to deep
drawing and EBW. As has been demonstrated by several
other groups, complete cavities can be hydroformed from
Nb tubes in one step using internal pressure and outer
dies. Hydroforming of cavities in an industrial setting is
presently being explored. EBFFF is a new technique for
forming parts from wire stock with an electron beam.
Though it may not be suitable for fabrication of a
complete cavity, EBFFF could be used to produce tubes
for hydroforming or parts for drift tube cavities.
Additionally, the possibility of producing single crystal
tubes using EBFFF is being explored. | |