Interactions News Wire
#82-05
14 October 2005
http://www.interactions.org*******************************************************************
Source:
High Energy Accelerator Research Organization (KEK)
Content: Press
Release
Date Issued: 14 October
2005
*******************************************************************
KEK
pushes superconducting cavity to work at its theoretical limitFor press
release including figures:
http://www.kek.jp/intra-e/press/2005/ilc_e.htmlTeam of accelerator physicists led by associate professor
Kenji Saito, High Energy Accelerator Research Organization
(KEK), successfully achieved 52.3 MV/m field gradient on
Niobium superconducting accelerator cavity. This gradient
is an equivalent to connecting 35 million AA battery cells
in series into one meter.
The
high gradient superconducting cavity is one of the most vital components in
designing the next generation high energy accelerators such as the International
Linear Collider (ILC). Existing superconducting cavities, such as the ones
developed by DESY, used to achieve 41 MV/m. Saito's group tested two types of
single-cell cavities designed based on present understanding of the the nature
of the surface field limitation. KEK also contributed with its surface cleaning
technique with ultra-high pressure water cleaning for perfecting the surface of
the cavity, which is originally developed for KEK B-factory.
The
two types of cavities are: the re-entrant shape (RE) figure 1 (left), designed
and manufactured by Cornell University group led by Professor Hasan Padamsee,
and the low-loss shape (LL), designed in collaboration by KEK, JLab and DESY,
and manufactured by KEK Mechanical Engineering Center, figure 1(right). At the
liquid helium temperature (2 K), the RE shape achieved the field gradient 52.3
MV/m at Qo = 0.97 x
1010, which the
LL shape achieved 47.3 MV/m at Qo = 1.13 x
1010 (Fig. 1). These values are the world records, and
considered to be their theoretical limits with these cavity shapes.
*) Qo is
the inverse of superconductivity resistance.
"The gradient
performance of cavities with traditional shape and traditional surface treatment
has been limited at about 41MV/m in the past", says Saito. "Our new result
corroborates a conjecture, which some of us have been trying to prove since
2001, that both the cavity shape and the surface treatment are the keys for
achieving high gradients with superconducting cavities. With further studies I
hope we eventually establish a new standard in building high-gradient cavities
with good yield and reliability."
KEK is now developing a new
9-cell shape high gradient cavity for the ILC, called ICHIRO (for 51 MV/m
objective, named for a famous baseball player's number). ILC in the present
design is expected to deploy over 14,000 units of such 9-cell cavities.