SRF2015 - Classification: SRF Technology - Processing / F04-Cleaning

Paper	Title	Page
MOPB112	SRF Quality Assurance Studies and Their Application to Cryomodule Repairs at SNS	428
	J.D. Mammosser, R. Afanador, D.L. Barnhart, B. DeGraff, B.S. Hannah, J. Saunders, P.V. Tyagi ORNL RAD, Oak Ridge, Tennessee, USA C.M. Campbell Omega Technical Services, Oak Ridge, Tennessee, USA M. Doleans, D.K. Hensley, S.-H. Kim ORNL, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. Many of the SRF activities involve interactions to cavities which presents risk for particulate contamination to RF surfaces. In order to understand and reduce contamination in cavities during cleaning, vacuum pumping and purging, and in-situ cryomodule repairs, a Quality Assurance (QA) studies were initiated to evaluate these activities and improve them where possible. This paper covers the results of investigations on the effectiveness of the SNS ultrasonic cleaning systems, particulate control during pumping and purging, procedure development for in-situ cryomodule repairs, the application of these studies to the repair of a linac cryomodule, and discussion of further improvement in these areas.
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MOPB115	Surface Studies of Plasma Processed Nb Samples	438
	P.V. Tyagi, R. Afanador, B. DeGraff, M. Doleans, B.S. Hannah, M.P. Howell, S.-H. Kim, J.D. Mammosser, C.J. McMahan, J. Saunders, S.E. Stewart ORNL, Oak Ridge, Tennessee, USA
	Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. 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.
	Poster MOPB115 [0.524 MB]
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MOPB116	Developments of Horizontal High Pressure Rinsing for SuperKEKB SRF Cavities	443
	Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki KEK, Ibaraki, Japan
	The Q factors of the eight superconducting accelerating cavities gradually degraded during the long-term operation of the KEKB accelerator. Since we will re-use those SRF cavities for the SuperKEKB, the performance degradation will be a serious problem. Several cavities degraded their performance significantly at high accelerating fields. The Q degradation is still acceptable for the 1.5 MV operations at SuperKEKB. However, further degradation will make the operation difficult. In order to recover the cavity performance, we developed horizontal high pressure water rinsing (HHPR). This method uses a horizontal high pressure water nozzle and inserts it directly into the cavity module. We applied this method to two degraded cavities and their degraded Q factors recovered above 10⁹ at around 2 MV. In this paper we will present the HHPR method, high power test results after the HHPR and the residual gas analysis.
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THAA06	Precise Studies on He-Processing and HPR for Recovery From Field Emission by Using X-Ray Mapping System	1019
	H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori KEK, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	We usually met the degradation of superconducting RF cavity on the cryomodule test and beam operation even if the performance of this cavity is good on the vertical test (V.T). Field emission is the most severe problem for this degradation after reassembly work from vertical test. Not only high pressure rinsing (HPR) but also He-processing, which is more suitable method without the reassembly work for recovery, is recommended and tried to recover this degradation. However, we did not investigate the details of how field emission sources were processed and removed after HPR and He-processing. We deeply investigated the processing procedure during He-processing and how many field emission sources removed after HPR by using rotating X-ray mapping system* in V.T . *H.Sakai et.al., Proc. of IPAC10 p2950-2952.
	Slides THAA06 [4.347 MB]
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THBA01	Plasma Processing to Improve SRF Accelerating Gradient
	M. Doleans, R. Afanador, J.A. Ball, D.L. Barnhart, W. Blokland, M.T. Crofford, B. DeGraff, B.S. Hannah, M.P. Howell, S.-H. Kim, S.W. Lee, J.D. Mammosser, C.J. McMahan, T.S. Neustadt, J. Saunders, S.E. Stewart, W.H. Strong, P.V. Tyagi, D.M. Vandygriff ORNL, Oak Ridge, Tennessee, USA
	Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE 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
	Slides THBA01 [3.565 MB]
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Paper

Title

Page

SRF Quality Assurance Studies and Their Application to Cryomodule Repairs at SNS

428

J.D. Mammosser, R. Afanador, D.L. Barnhart, B. DeGraff, B.S. Hannah, J. Saunders, P.V. Tyagi
ORNL RAD, Oak Ridge, Tennessee, USA
C.M. Campbell
Omega Technical Services, Oak Ridge, Tennessee, USA
M. Doleans, D.K. Hensley, S.-H. Kim
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Many of the SRF activities involve interactions to cavities which presents risk for particulate contamination to RF surfaces. In order to understand and reduce contamination in cavities during cleaning, vacuum pumping and purging, and in-situ cryomodule repairs, a Quality Assurance (QA) studies were initiated to evaluate these activities and improve them where possible. This paper covers the results of investigations on the effectiveness of the SNS ultrasonic cleaning systems, particulate control during pumping and purging, procedure development for in-situ cryomodule repairs, the application of these studies to the repair of a linac cryomodule, and discussion of further improvement in these areas.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB115

Surface Studies of Plasma Processed Nb Samples

438

P.V. Tyagi, R. Afanador, B. DeGraff, M. Doleans, B.S. Hannah, M.P. Howell, S.-H. Kim, J.D. Mammosser, C.J. McMahan, J. Saunders, S.E. Stewart
ORNL, Oak Ridge, Tennessee, USA

Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
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.

Poster MOPB115 [0.524 MB]

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MOPB116

Developments of Horizontal High Pressure Rinsing for SuperKEKB SRF Cavities

443

Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki
KEK, Ibaraki, Japan

The Q factors of the eight superconducting accelerating cavities gradually degraded during the long-term operation of the KEKB accelerator. Since we will re-use those SRF cavities for the SuperKEKB, the performance degradation will be a serious problem. Several cavities degraded their performance significantly at high accelerating fields. The Q degradation is still acceptable for the 1.5 MV operations at SuperKEKB. However, further degradation will make the operation difficult. In order to recover the cavity performance, we developed horizontal high pressure water rinsing (HHPR). This method uses a horizontal high pressure water nozzle and inserts it directly into the cavity module. We applied this method to two degraded cavities and their degraded Q factors recovered above 10⁹ at around 2 MV. In this paper we will present the HHPR method, high power test results after the HHPR and the residual gas analysis.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THAA06

Precise Studies on He-Processing and HPR for Recovery From Field Emission by Using X-Ray Mapping System

1019

H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

We usually met the degradation of superconducting RF cavity on the cryomodule test and beam operation even if the performance of this cavity is good on the vertical test (V.T). Field emission is the most severe problem for this degradation after reassembly work from vertical test. Not only high pressure rinsing (HPR) but also He-processing, which is more suitable method without the reassembly work for recovery, is recommended and tried to recover this degradation. However, we did not investigate the details of how field emission sources were processed and removed after HPR and He-processing. We deeply investigated the processing procedure during He-processing and how many field emission sources removed after HPR by using rotating X-ray mapping system* in V.T .
*H.Sakai et.al., Proc. of IPAC10 p2950-2952.

Slides THAA06 [4.347 MB]

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THBA01

Plasma Processing to Improve SRF Accelerating Gradient

M. Doleans, R. Afanador, J.A. Ball, D.L. Barnhart, W. Blokland, M.T. Crofford, B. DeGraff, B.S. Hannah, M.P. Howell, S.-H. Kim, S.W. Lee, J.D. Mammosser, C.J. McMahan, T.S. Neustadt, J. Saunders, S.E. Stewart, W.H. Strong, P.V. Tyagi, D.M. Vandygriff
ORNL, Oak Ridge, Tennessee, USA

Funding: This work is supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE
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

Slides THBA01 [3.565 MB]

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