SRF2011 - List of Authors (Eremeev, G.V.)

Paper

Title

Page

High Gradient Results of ICHIRO 9-Cell Cavity in Collaboration With KEK and Jlab

386

F. Furuta, T. Konomi, K. Saito
KEK, Ibaraki, Japan
G.V. Eremeev, R.L. Geng
JLAB, Newport News, Virginia, USA

KEK and Jlab have continued S0-study collaboration on ICHIRO 9-cell cavities since 2008. In 2010, we have started S0 study on ICHIRO#7, full 9-cell cavity with end groups. Surface treatments and vertical tests have been repeated at Jlab. Maximum gradient of 40MV/m was achieved so far. We will describe the details of that and further plan of S0-study on ICHIRO 9-cell.

Poster TUPO014 [1.682 MB]

TUPO019

Fabrication, Tuning, Treatment and Testing of Two 3.5 Cell Photo-Injector Cavities for the ELBE Linac

405

A. Arnold, P. Murcek, J. Teichert, R. Xiang
HZDR, Dresden, Germany
G.V. Eremeev, P. Kneisel, M. Stirbet, L. Turlington
JLAB, Newport News, Virginia, USA

As part of a CRADA (Cooperative Research and Development Agreement) between Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Thomas Jefferson Lab National Accelerator Facility (TJNAF) we have fabricated and tested two 1.3 GHz 3.5 cell photo-injector cavities from polycrystalline RRR niobium and large grain RRR niobium, respectively. The cavity with the better performance will replace the presently used injector cavity in the ELBE linac*. The cavities have been fabricated and pre-tuned at TJNAF, while the more sophisticated final field tuning, the adjustment of the external couplings and the field profile measurement of transverse electric modes for RF focusing** was done at HZDR. The following standard surface treatment and the vertical test was carried out at TJNAF’s production facilities. A major challenge turned out to be the rinsing of the cathode cell, which has small opening (Ø10mm) to receive the cathode stalk. Another unexpected problem encountered after etching, since large visible defects appeared in the least accessible cathode cell. This contribution reports about our experiences, initial results and the on-going diagnostic work to understand and fix the problems.
* J. Teichert, et al., Proc. FEL 2010, Malmoe, Sweden, p. 453.
** V. Volkov, D. Janssen, Phys. Rev. ST Accel. Beams 11, 061302 (2008).

Poster TUPO019 [1.211 MB]

TUPO049

Q0 Improvement of Large-Grain Multi-Cell Cavities by Using JLab’s Standard ILC EP Processing

501

R.L. Geng, G.V. Eremeev, P. Kneisel
JLAB, Newport News, Virginia, USA
K.X. Liu, X.Y. Lu, K. Zhao
PKU/IHIP, Beijing, People's Republic of China

Funding: This work was authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
As reported previously at the Berlin workshop, applying the JLab standard ILC EP recipe on previously BCP etched fine-grain multi-cell cavities results in improvement both in gradient and Q0. We recently had the opportunity to experiment with two 1300 MHz 9-cell large-gain niobium cavities manufacture by JLab and Peking University. Both cavities were initially BCP etched and further processed by using JLab’s standard ILC EP recipe. Due to fabrication defects, these two cavities only reached a gradient in the range of 20-30 MV/m. Interestingly both cavities demonstrated significant Q0 improvement in the gradient range of 15-20 MV/m. At 2K, a Q0 value of 2·10¹⁰ is achieved at 20 MV/m. At a reduced temperature of 1.8K, a Q0 value of 3·10¹⁰ is achieved at 20 MV/m. These results suggest that a possible path for obtaining higher Q0 in the medium gradient range is to use the large-grain material for cavity fabrication and EP and low temperature bake for cavity processing.

THPO005

Exploration of Very High Gradient Cavities

698

G.V. Eremeev
JLAB, Newport News, Virginia, USA

Several of the 9-cell ILC cavities processed at Jlab within ongoing ILC R&D program have shown interesting behavior at high fields, such as mode mixing and sudden field emission turn-on during quench. Equipped with thermometry and OST system for quench detection, we couple our RF measurements with local dissipation measurements. In this contribution we report on our findings with high gradient SRF cavities.

Poster THPO005 [1.673 MB]

THPO017

Probing the Fundamental Limit of Niobium in High Radiofrequency Fields by Dual Mode Excitation in Superconducting Radiofrequency Cavities

746

G.V. Eremeev, R.L. Geng, A.D. Palczewski
JLAB, Newport News, Virginia, USA

Funding: *Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We have studied thermal breakdown in several multicell superconducting radiofrequency cavity by simultaneous excitation of two TM010 passband modes. Unlike measurements done in the past, which indicated a clear thermal nature of the breakdown, our measurements present a more complex picture with interplay of both thermal and magnetic effects. JLab LG-1 that we studied was limited at 40.5 MV/m, corresponding to Bpeak = 173 mT, in 8pi9 mode. Dual mode measurements on this quench indicate that this quench is not purely magnetic, and so we conclude that this field is not the fundamental limit in SRF cavities.

Poster THPO017 [1.110 MB]

THPO018

Quench Studies of ILC Cavities

750

G.V. Eremeev, R.L. Geng, A.D. Palczewski
JLAB, Newport News, Virginia, USA
J. Dai
PKU/IHIP, Beijing, People's Republic of China

Funding: *Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Quench limits accelerating gradient in SRF cavities to a gradient lower than theoretically expected for superconducting niobium. Identification of the quenching site with thermometry and OST, optical inspection, and replica of the culprit is an ongoing effort at Jefferson Lab aimed at better understanding of this limiting phenomenon. In this contribution we present our finding with several SRF cavities that were limited by quench.

Poster THPO018 [1.064 MB]

THPO019

Design, Construction, and Initial Test of High Spatial Resolution Thermometry Arrays for Detection of Surface Temperature Profiles on SRF Cavities in Super Fluid Helium

755

A.D. Palczewski, G.V. Eremeev, R.L. Geng
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We designed and built two high resolution (0.6-0.55mm special resolution [1.1-1.2mm separation]) thermometry arrays prototypes out of the Allen Bradley 90-120 Ω 1/8 watt resistor to measure surface temperature profiles on SRF cavities. One array was designed to be physically flexible and conform to any location on a SRF cavity; the other was modeled after the common G-10/stycast 2850 thermometer and designed to fit on the equator of an ILC (Tesla 1.3GHz) SRF cavity. We will discuss the advantages and disadvantages of each array and their construction. In addition we will present a case study of the arrays performance on a real SRF cavity TB9NR001. TB9NR001 presented a unique opportunity to test the performance of each array as it contained a dual (4mm separation) cat eye defect which conventional methods such as OST (Oscillating Superleak second-sound Transducers) and full coverage thermometry mapping were unable to distinguish between. We will discuss the new arrays ability to distinguish between the two defects and their preheating performance.

THPO020

Exploration of Quench Initiation Due to Intentional Geometrical Defects in a High Magnetic Field Region of an SRF Cavity

759

J. Dai, K. Zhao
PKU/IHIP, Beijing, People's Republic of China
G.V. Eremeev, R.L. Geng, A.D. Palczewski
JLAB, Newport News, Virginia, USA

Funding: *Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
A computer program which was used to simulate and analyze the thermal behaviors of SRF cavities has been developed at Jefferson Lab using C++ code. This code was also used to verify the quench initiation due to geometrical defects in high magnetic field region of SRF cavities. We built a CEBAF single cell cavity with 4 artificial defects near equator, and this cavity has been tested with T-mapping. The preheating behavior and quench initiation analysis of this cavity will be presented here using the computer program.
daijin@pku.edu.cn

THPO029

Commissioning Cornell OSTs for SRF Cavity Testing at JLab

781

G.V. Eremeev
JLAB, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Understanding the current quench limitations in SRF cavities is a topic essential for any SRF accelerator that requires high fields. This znderstanding crucially depends on correct and precise quench identification. Second sound quench detection in superfluid liquid helium with oscillating superleak transducers is a technique recently applied at Cornell University as a fast and versatile method for quench identification in SRF cavities. Having adopted Cornell design, we report in this contribution on our experience with OST for quench identification in different cavities at JLab.
Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.

Poster THPO029 [1.530 MB]

Paper	Title	Page
TUPO014	High Gradient Results of ICHIRO 9-Cell Cavity in Collaboration With KEK and Jlab	386
	F. Furuta, T. Konomi, K. Saito KEK, Ibaraki, Japan G.V. Eremeev, R.L. Geng JLAB, Newport News, Virginia, USA
	KEK and Jlab have continued S0-study collaboration on ICHIRO 9-cell cavities since 2008. In 2010, we have started S0 study on ICHIRO#7, full 9-cell cavity with end groups. Surface treatments and vertical tests have been repeated at Jlab. Maximum gradient of 40MV/m was achieved so far. We will describe the details of that and further plan of S0-study on ICHIRO 9-cell.
	Poster TUPO014 [1.682 MB]

TUPO019	Fabrication, Tuning, Treatment and Testing of Two 3.5 Cell Photo-Injector Cavities for the ELBE Linac	405
	A. Arnold, P. Murcek, J. Teichert, R. Xiang HZDR, Dresden, Germany G.V. Eremeev, P. Kneisel, M. Stirbet, L. Turlington JLAB, Newport News, Virginia, USA
	As part of a CRADA (Cooperative Research and Development Agreement) between Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Thomas Jefferson Lab National Accelerator Facility (TJNAF) we have fabricated and tested two 1.3 GHz 3.5 cell photo-injector cavities from polycrystalline RRR niobium and large grain RRR niobium, respectively. The cavity with the better performance will replace the presently used injector cavity in the ELBE linac. The cavities have been fabricated and pre-tuned at TJNAF, while the more sophisticated final field tuning, the adjustment of the external couplings and the field profile measurement of transverse electric modes for RF focusing* was done at HZDR. The following standard surface treatment and the vertical test was carried out at TJNAF’s production facilities. A major challenge turned out to be the rinsing of the cathode cell, which has small opening (Ø10mm) to receive the cathode stalk. Another unexpected problem encountered after etching, since large visible defects appeared in the least accessible cathode cell. This contribution reports about our experiences, initial results and the on-going diagnostic work to understand and fix the problems. * J. Teichert, et al., Proc. FEL 2010, Malmoe, Sweden, p. 453. ** V. Volkov, D. Janssen, Phys. Rev. ST Accel. Beams 11, 061302 (2008).
	Poster TUPO019 [1.211 MB]

TUPO049	Q0 Improvement of Large-Grain Multi-Cell Cavities by Using JLab’s Standard ILC EP Processing	501
	R.L. Geng, G.V. Eremeev, P. Kneisel JLAB, Newport News, Virginia, USA K.X. Liu, X.Y. Lu, K. Zhao PKU/IHIP, Beijing, People's Republic of China
	Funding: This work was authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 As reported previously at the Berlin workshop, applying the JLab standard ILC EP recipe on previously BCP etched fine-grain multi-cell cavities results in improvement both in gradient and Q0. We recently had the opportunity to experiment with two 1300 MHz 9-cell large-gain niobium cavities manufacture by JLab and Peking University. Both cavities were initially BCP etched and further processed by using JLab’s standard ILC EP recipe. Due to fabrication defects, these two cavities only reached a gradient in the range of 20-30 MV/m. Interestingly both cavities demonstrated significant Q0 improvement in the gradient range of 15-20 MV/m. At 2K, a Q0 value of 2·10¹⁰ is achieved at 20 MV/m. At a reduced temperature of 1.8K, a Q0 value of 3·10¹⁰ is achieved at 20 MV/m. These results suggest that a possible path for obtaining higher Q0 in the medium gradient range is to use the large-grain material for cavity fabrication and EP and low temperature bake for cavity processing.

THPO005	Exploration of Very High Gradient Cavities	698
	G.V. Eremeev JLAB, Newport News, Virginia, USA
	Several of the 9-cell ILC cavities processed at Jlab within ongoing ILC R&D program have shown interesting behavior at high fields, such as mode mixing and sudden field emission turn-on during quench. Equipped with thermometry and OST system for quench detection, we couple our RF measurements with local dissipation measurements. In this contribution we report on our findings with high gradient SRF cavities.
	Poster THPO005 [1.673 MB]

THPO017	Probing the Fundamental Limit of Niobium in High Radiofrequency Fields by Dual Mode Excitation in Superconducting Radiofrequency Cavities	746
	G.V. Eremeev, R.L. Geng, A.D. Palczewski JLAB, Newport News, Virginia, USA
	Funding: *Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. We have studied thermal breakdown in several multicell superconducting radiofrequency cavity by simultaneous excitation of two TM010 passband modes. Unlike measurements done in the past, which indicated a clear thermal nature of the breakdown, our measurements present a more complex picture with interplay of both thermal and magnetic effects. JLab LG-1 that we studied was limited at 40.5 MV/m, corresponding to Bpeak = 173 mT, in 8pi9 mode. Dual mode measurements on this quench indicate that this quench is not purely magnetic, and so we conclude that this field is not the fundamental limit in SRF cavities.
	Poster THPO017 [1.110 MB]

THPO018	Quench Studies of ILC Cavities	750
	G.V. Eremeev, R.L. Geng, A.D. Palczewski JLAB, Newport News, Virginia, USA J. Dai PKU/IHIP, Beijing, People's Republic of China
	Funding: *Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Quench limits accelerating gradient in SRF cavities to a gradient lower than theoretically expected for superconducting niobium. Identification of the quenching site with thermometry and OST, optical inspection, and replica of the culprit is an ongoing effort at Jefferson Lab aimed at better understanding of this limiting phenomenon. In this contribution we present our finding with several SRF cavities that were limited by quench.
	Poster THPO018 [1.064 MB]

THPO019	Design, Construction, and Initial Test of High Spatial Resolution Thermometry Arrays for Detection of Surface Temperature Profiles on SRF Cavities in Super Fluid Helium	755
	A.D. Palczewski, G.V. Eremeev, R.L. Geng JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. We designed and built two high resolution (0.6-0.55mm special resolution [1.1-1.2mm separation]) thermometry arrays prototypes out of the Allen Bradley 90-120 Ω 1/8 watt resistor to measure surface temperature profiles on SRF cavities. One array was designed to be physically flexible and conform to any location on a SRF cavity; the other was modeled after the common G-10/stycast 2850 thermometer and designed to fit on the equator of an ILC (Tesla 1.3GHz) SRF cavity. We will discuss the advantages and disadvantages of each array and their construction. In addition we will present a case study of the arrays performance on a real SRF cavity TB9NR001. TB9NR001 presented a unique opportunity to test the performance of each array as it contained a dual (4mm separation) cat eye defect which conventional methods such as OST (Oscillating Superleak second-sound Transducers) and full coverage thermometry mapping were unable to distinguish between. We will discuss the new arrays ability to distinguish between the two defects and their preheating performance.

THPO020	Exploration of Quench Initiation Due to Intentional Geometrical Defects in a High Magnetic Field Region of an SRF Cavity	759
	J. Dai, K. Zhao PKU/IHIP, Beijing, People's Republic of China G.V. Eremeev, R.L. Geng, A.D. Palczewski JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 A computer program which was used to simulate and analyze the thermal behaviors of SRF cavities has been developed at Jefferson Lab using C++ code. This code was also used to verify the quench initiation due to geometrical defects in high magnetic field region of SRF cavities. We built a CEBAF single cell cavity with 4 artificial defects near equator, and this cavity has been tested with T-mapping. The preheating behavior and quench initiation analysis of this cavity will be presented here using the computer program. daijin@pku.edu.cn*

THPO029	Commissioning Cornell OSTs for SRF Cavity Testing at JLab	781
	G.V. Eremeev JLAB, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Understanding the current quench limitations in SRF cavities is a topic essential for any SRF accelerator that requires high fields. This znderstanding crucially depends on correct and precise quench identification. Second sound quench detection in superfluid liquid helium with oscillating superleak transducers is a technique recently applied at Cornell University as a fast and versatile method for quench identification in SRF cavities. Having adopted Cornell design, we report in this contribution on our experience with OST for quench identification in different cavities at JLab. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
	Poster THPO029 [1.530 MB]