ORNL, Oak Ridge, Tennessee, USA
ORNL RAD, Oak Ridge, Tennessee, USA
The beam power of the Linac for the Second Target Station (STS) at the Spallation Neutron Source (SNS) will be doubled to 2.8 MW. For the energy upgrade seven additional cryomodules will be installed in the reserved space at the end of the linac tunnel to produce the linac output energy of 1.3 GeV. The cryomodules for STS will have some changes that do not require changes of overall layout based on the lessons learned from operational experience over the last 10 years and the high beta spare cryomodule developed in house. The average macro-pulse beam current for the STS will be 38 mA that is about 40 % increase from that for the present 1.4 MW operation. Plans for the existing cryomodules to support higher beam current for the STS is also presented in this paper.
ORNL, Oak Ridge, Tennessee, USA
Contaminants present at top surface of superconducting radio frequency (SRF) cavities can act as field emitters and restrict the cavity accelerating gradient. A room temperature in-situ plasma processing technology for SRF cavities aiming to clean hydrocarbons from inner surface of cavities has been recently developed at the Spallation Neutron Source (SNS). Surface studies of the plasma processed Nb samples by Secondary ion mass spectrometry (SIMS) and Scanning Kelvin Probe (SKP) showed that the NeO2 plasma processing is very effective to remove carbonaceous contaminants from top surface and improves the surface work function by 0.5 to 1.0 eV.
*M. Doleans et al., Proc. 2013 SRF, Paris, France.
**P. V. Tyagi, et al., Proc. Linac14, Geneva, Switzerland.
***M. Doleans et al., These proceedings.
THBA01
ORNL, Oak Ridge, Tennessee, USA
A new In-situ plasma processing technique is being developed at the SNS (Spallation Neutron Source) to improve the performance of the cavities in operation. The technique utilizes a reactive low-density room-temperature plasma to remove top-surface hydrocarbons. This increases the work function of the cavity surface and reduces the overall amount of electron activity; In particular it increases the field-emission onset, which enables to operate a cavity at higher accelerating gradient. Development of the basic plasma processing parameters and effect on the Niobium surface can be found elsewhere *,**. Details on the results for in-situ plasma processing of dressed cavities in the SNS HTA (horizontal test apparatus) will be reported here.
* M. Doleans et al. “Plasma processing R&D for the SNS superconducting linac RF cavities” SRF2013 Proceedings
** P. V. Tyagi, et al. “Surface Studies of Plasma Processed Nb samples” These proceedings
