SRF2011 - List of Authors (Lin, L.)

Paper	Title	Page
TUPO031	Update on the R&D of Vertical Buffered Electropolishing on Nb Samples and SRF Single Cell Cavities	442
	A.T. Wu, J.D. Mammosser, R.A. Rimmer JLAB, Newport News, Virginia, USA S. Jin, L. Lin, X.Y. Lu, K. Zhao PKU/IHIP, Beijing, People's Republic of China
	Electropolishing (EP) has become a popular choice as the final step of the surface removal process during the fabrication of Nb superconducting radio frequency (SRF) cavities. One of the major reasons for the choice is that Nb SRF cavities treated by EP tend to have a better chance to reach an accelerating gradient of 30MV/m or higher. This advantage of EP over BCP can at least be partially attributed to the smoother Nb surfaces that EP can produce. Recently a Nb surface removal technique called buffered electropolishing (BEP) was developed at JLab, which could produce the smoothest surface finish. In this contribution, R&D efforts of vertical BEP on Nb small samples and SRF single cell cavities since the last SRF conference in 2009 will be updated. It is shown that under a suitable condition, BEP can have a Nb removal rate as high as 10 μm/mim that is more than 25 and 5 times quicker than those of EP and BCP(112) respectively. Possible mechanisms responsible for the high Nb removal rate are proposed. Clues on the optimization of vertical BEP and EP treatments on Nb SRF cavities from recent experimental results obtained on a Nb single cell demountable cavity will be discussed. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.

FRIOB01	SRF Activities at Peking University	969
	J.K. Hao, J.E. Chen, L. Lin, K.X. Liu, X.Y. Lu, S.W. Quan, B.C. Zhang, K. Zhao, F. Zhu PKU/IHIP, Beijing, People's Republic of China
	Funding: Work supported by the Major State Basic Research Development Program of China (Grant No. 2008CB817706 and 2011CB808303). Superconducting RF technology has been developed at Peking University for more than 20 years. In the recent years, the researches are mainly focused on producing high performance superconducting cavities and installing the DC-SRF photocathode injector as well as related 2K cryogenic facility and other auxiliary equipment. The cavities designed and fabricated by Peking University mainly include TESLA type 9-cell cavities, 1.3 GHz 5-cell cavity for high current electron beam acceleration and 450 MHz spoke cavity for low energy proton acceleration. Vertical tests of the cavities indicate that the cavities show good performances and can be used for superconducting accelerators. The gradient of a 9-cell TESLA type cavity with end groups (PKU3) reaches 28.6 MV/m. To promote the industrialization process in China, a new company, Ningxia Orient Superconductor Technology Co., Ltd., was founded jointly by Ningxia OTIC and Peking University in 2011. The goal of this company is to produce various types of superconducting cavities and pure niobium materials with high quality.

FRIOB02	STATUS OF THE DC-SRF PHOTOINJECTOR FOR PKU-SETF	973
	F. Zhu, J.E. Chen, J.K. Hao, S. Huang, L. Lin, K.X. Liu, X.Y. Lu, S.W. Quan, F. Wang, H.M. Xie, K. Zhao PKU/IHIP, Beijing, People's Republic of China
	Funding: Supported by Major State Basic Research Development Program(973 Program 2011CB808302) and National Natural Science Foundation of China ( 11075007) DC-SRF photocathode injector developed by Peking University is a good candidate for obtaining high average current, low emittance, short electron beam pulse. Much progress has been made on the 3.5-cell cavity DC-SRF injector since SRF2009. The assembling of the cryomodule was completed with the 3.5-cell SRF cavity which has an accelerating gradient of 23.5MV/m in the vertical test. The preliminary RF experiment has been carried out soon after the installation and commissioning of 2K cryogenic system was finished. The accelerating gradient of the cavity is 11.5MV/m in a horizontal cold test and the Qext is 6×10⁶ . The limitation of the gradient is mainly from our present low RF power source. Higher gradient is expected with a new 20kW solid state RF power source which will be delivered to Peking University soon.

Paper

Title

Page

Update on the R&D of Vertical Buffered Electropolishing on Nb Samples and SRF Single Cell Cavities

442

A.T. Wu, J.D. Mammosser, R.A. Rimmer
JLAB, Newport News, Virginia, USA
S. Jin, L. Lin, X.Y. Lu, K. Zhao
PKU/IHIP, Beijing, People's Republic of China

Electropolishing (EP) has become a popular choice as the final step of the surface removal process during the fabrication of Nb superconducting radio frequency (SRF) cavities. One of the major reasons for the choice is that Nb SRF cavities treated by EP tend to have a better chance to reach an accelerating gradient of 30MV/m or higher. This advantage of EP over BCP can at least be partially attributed to the smoother Nb surfaces that EP can produce. Recently a Nb surface removal technique called buffered electropolishing (BEP) was developed at JLab, which could produce the smoothest surface finish. In this contribution, R&D efforts of vertical BEP on Nb small samples and SRF single cell cavities since the last SRF conference in 2009 will be updated. It is shown that under a suitable condition, BEP can have a Nb removal rate as high as 10 μm/mim that is more than 25 and 5 times quicker than those of EP and BCP(112) respectively. Possible mechanisms responsible for the high Nb removal rate are proposed. Clues on the optimization of vertical BEP and EP treatments on Nb SRF cavities from recent experimental results obtained on a Nb single cell demountable cavity will be discussed.
Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.

FRIOB01

SRF Activities at Peking University

969

J.K. Hao, J.E. Chen, L. Lin, K.X. Liu, X.Y. Lu, S.W. Quan, B.C. Zhang, K. Zhao, F. Zhu
PKU/IHIP, Beijing, People's Republic of China

Funding: Work supported by the Major State Basic Research Development Program of China (Grant No. 2008CB817706 and 2011CB808303).
Superconducting RF technology has been developed at Peking University for more than 20 years. In the recent years, the researches are mainly focused on producing high performance superconducting cavities and installing the DC-SRF photocathode injector as well as related 2K cryogenic facility and other auxiliary equipment. The cavities designed and fabricated by Peking University mainly include TESLA type 9-cell cavities, 1.3 GHz 5-cell cavity for high current electron beam acceleration and 450 MHz spoke cavity for low energy proton acceleration. Vertical tests of the cavities indicate that the cavities show good performances and can be used for superconducting accelerators. The gradient of a 9-cell TESLA type cavity with end groups (PKU3) reaches 28.6 MV/m. To promote the industrialization process in China, a new company, Ningxia Orient Superconductor Technology Co., Ltd., was founded jointly by Ningxia OTIC and Peking University in 2011. The goal of this company is to produce various types of superconducting cavities and pure niobium materials with high quality.

FRIOB02

STATUS OF THE DC-SRF PHOTOINJECTOR FOR PKU-SETF

973

F. Zhu, J.E. Chen, J.K. Hao, S. Huang, L. Lin, K.X. Liu, X.Y. Lu, S.W. Quan, F. Wang, H.M. Xie, K. Zhao
PKU/IHIP, Beijing, People's Republic of China

Funding: Supported by Major State Basic Research Development Program(973 Program 2011CB808302) and National Natural Science Foundation of China ( 11075007)
DC-SRF photocathode injector developed by Peking University is a good candidate for obtaining high average current, low emittance, short electron beam pulse. Much progress has been made on the 3.5-cell cavity DC-SRF injector since SRF2009. The assembling of the cryomodule was completed with the 3.5-cell SRF cavity which has an accelerating gradient of 23.5MV/m in the vertical test. The preliminary RF experiment has been carried out soon after the installation and commissioning of 2K cryogenic system was finished. The accelerating gradient of the cavity is 11.5MV/m in a horizontal cold test and the Qext is 6×10⁶ . The limitation of the gradient is mainly from our present low RF power source. Higher gradient is expected with a new 20kW solid state RF power source which will be delivered to Peking University soon.