| Paper | Title | Page |
|---|
| TUP65 | JLAB CW Cryomodules for 4th Generation Light Sources | 288 |
| | - R. A. Rimmer, R. Bundy, G. Cheng, G. Ciovati, W. Clemens, E. F. Daly, J. Henry, W. R. Hicks, P. Kneisel, S. Manning, R. Manus, F. Marhauser, J. Preble, C. Reece, K. Smith, M. Stirbet, L. Turlington, H. Wang, K. M. Wilson
JLab
| |
| | Fourth generation light sources hold the prospect of
unprecedented brightness and optical beam quality for a
wide range of scientific applications. Many of the
proposed new facilities will rely on large superconducting
radio frequency (SRF) based linacs to provide high
energy, low emittance CW electron beams. For high
average power applications there is a growing acceptance
of energy recovery linac (ERL) technology as the way to
support large recirculating currents with modest RF
power requirements. CW SRF and high current ERLs are
two core competencies at Jefferson Lab. JLab has
designed and built a number of CW cryomodules of
several different types starting with the original CEBAF
design, with variations for higher current in the two
generations of JLab's free-electron laser (FEL), through
two intermediate prototypes to the final high-performance
module for the 12 GeV upgrade. Each of these represent
fully engineered and tested configurations with a variety
of specifications that could be considered for possible use
in fourth generation light sources. Furthermore JLab has
been actively pursuing advanced concepts for highcurrent
high-efficiency cryomodules for next generation
ERL based FEL's. These existing and proposed designs
span the range from about 1mA single-pass to over 100
mA energy recovered current capability. Specialized
configurations also exist for high-current non-energy
recovered sections such as the injector region where very
high RF power is required. We discuss the performance
parameters of these existing and proposed designs and
their suitability to different classes of fourth generation
light sources. | |
| WEP31 | Optimization of the SRF Cavity Design for the CEBAF 12 GeV Upgrade | 536 |
| | - C. E. Reece, E. F. Daly, J. Henry, W. R. Hicks, J. Preble, H. Wang, G. Wu
JLab
| |
| | Based on initial testing of the "HG" and "LL" 7-cell
cavities in the prototype cryomodule Renascence, several
opportunities for improved optimization were identified.
The HOM damping configuration was refined so as to
meet the requirements for damping key dipole modes
while simultaneously dramatically reducing risk of HOM
pickup probe heating and also creating beamline clearance
for mounting the tuner to stainless steel helium vessel
endplates (rather than NbTi/Ti transitions to a titanium
helium vessel). Code modeling and bench measurements
were performed. The new design maintains the 7-cell LL
cells and incorporates a brazed transition between Nb and
the SS helium vessel. The resulting configuration is now
called the "C100" design. Cavity design details as well as
vertical dewar and horizontal test bed performance are presented. | |
| WEP32 | Performance of the CEBAF prototype cryomodule renascence | 540 |
| | - C. E. Reece, E. F. Daly, G. K. Davis, M. Drury, W. R. Hicks, J. Preble, H. Wang
JLab
| |
| | The prototype cryomodule Renascence was constructed as
an energy building block for securing 6 GeV operation of
CEBAF and to validate design elements for future
CEBAF upgrade modules. These elements include the
new "HG" and "LL" 7-cell cavity designs and a new tuner
design.[1,2] Issues were identified during initial testing in
2005. The module has been reworked to address the issues
with thermal stability, component breakage, and tuner
motion. In addition, opportunity was taken to employ
upgraded cleaning and assembly techniques for the cavity
string. The HOM coupler heating issue was resolved, and
seven of the eight cavities in the cryomodule have run
stably at an average of 20 MV/m CW. The cryogenic, rf,
and mechanical performance of the cryomodule are presented. Commissioning in CEBAF has just been completed in October 2007. | |
| WEP62 | Diagnosis, analysis, and resolution of thermal stability issues with HOM couplers on prototype CEBAF SRF cavities | 656 |
| | - C. E. Reece, E. F. Daly, G. K. Davis, W. R. Hicks, T. Rothgeb, H. L. Phillips, J. Preble, H. Wang, G. Wu
TJNAF
| |
| | During initial testing of the prototype cavities
incorporated into the developmental cryomodule
Renascence severe thermal stability issues were
encountered during CW operation. Additional diagnostic
instrumentation was added. This enabled identification of
an unanticipated thermal impedance between the HOM
coupler probe feedthrough assembly and the cavity
beamtube. Subsequent detailed FE analysis successfully
modeled the situation and indicated the need for alternate
cooling path for the couplers on those cavities. HOM
damping was measured to be adequate employing only
two of the four HOM couplers. The two pickup probes on
the couplers at the input power coupler side of each cavity
were removed, the remaining HOM probe feedthroughs
were heat stationed to two-phase helium supply piping,
and a novel heat sink was added to station both the inner
and outer conductors of the remaining HOM rf cables.
The characterization measurements, analysis,
modifications, and resulting performance are presented. | |
| WEP85 | Waveguide coupler kick to beam bunch and current dependency on SRF cavities | 721 |
| | - G. Wu
Fermilab - H. Wang, C. E. Reece, R. A. Rimmer
JLab
| |
| | JLAB SRF cavities employ waveguide type
fundamental power couplers (FPC). The FPC design for
the 7-cell upgrade cavities was optimized to minimize the
dipole field kick. For continuous wave (CW) operation,
the forwarding RF power will be at different magnitude to
drive the different beam current and cavity gradient. This
introduces some deviation from optimized FPC field for
varying beam loading. This article analyzes the beam
behavior both in centroid kick and head-tail kick under
different beam loading conditions. | |