| | - 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. | |
