SRF2011 - List of Authors (Kneisel, P.)

Paper

Title

Page

Modified SRF Photoinjector for the ELBE at HZDR

39

P. Murcek, A. Arnold, H. Büttig, D. Janssen, M. Justus, P. Michel, G.S. Staats, J. Teichert, R. Xiang
HZDR, Dresden, Germany
P. Kneisel
JLAB, Newport News, Virginia, USA

The superconducting radio frequency photoinjector (SRF photoinjector) with Cs2Te cathode has been successfully operated under the collaboration of BESSY, DESY, HZDR, and MBI. In order to improve the gradient of the gun cavity and the beam quality, a new modified SRF gun (SRF-gun2008) has been designed. The main updates of the new cavity design for the new injector was publisched before. (ID THPPO022 on the SRF09 Berlin.) This cavity is being fabricated in Jefferson Lab. In this paper the ideas of the redesign of the further parts of the SRF-gun2008 will be presented. The most important issue is the special design of half-cell and choke filter. The cathode cooler is also slightly changed, which simplifies the installation of the cathode cooler in the cavity. The next update is the separation of input and output of the liquid nitrogen supply, for the purpose of the stability of the N2 pressure as well as the better possibility of temperature measurement. Another key point is the implementation of the superconducting solenoid inside the cryomodule. The position of the solenoid can be accurately adjusted with two stepmotors, which is thermally isolated to the solenoid itself.

MOPO070

Preliminary Test Results from 650 MHz Single Cell Medium Beta Cavities for Project X

271

P. Kneisel, A. Burrill, P. Kushnick, F. Marhauser, R.A. Rimmer
JLAB, Newport News, Virginia, USA

Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We have fabricated two single cell 650 MHz cavities of a JLab design [1], for possible project X application. Both cavities were manufactured at Jlab from RRR>250 niobium sheet of 4 mm thickness using standard techniques such as deep drawing, EBW, BCP , hydrogen degassing heat treatment, high pressure ultrapure water rinsing and clean room assembly. A detailed description of the design and fabrication procedures is forthcoming [2]. Initially cavity #1 was – after final surface treatment by bcp – measured without any provisions for stiffening . As expected, the pressure sensitivity and the Lorentz Force detuning coefficients were quite high; however, the RF performance was very encouraging: the cavity exhibited a Q-value > 10¹¹ at 1.6K, corresponding to a residual resistance of < 1.5 nOhm The initial gradient was limited to Eacc ~ 18 MV/m, limited by field emission. In a subsequent test, we are re-rinsing the cavity and are making provisions for stiffening up the cavity. By the time of this writing, this test is in progress; the results will be reported at this conference as well as results from the second cavity.
[1] F. Marhauser, JLab-TN-10-043
[2] F. Marhauser et al; IPAC 2011 to be published

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]

TUPO026

Nine - Cell Tesla Shape Cavities Produced From Hydroformed Cells

431

W. Singer, A. Ermakov, G. Kreps, A. Matheisen, X. Singer, K. Twarowski
DESY, Hamburg, Germany
R. Crooks
Black Laboratories, L.L.C., Newport News, USA
P. Kneisel
JLAB, Newport News, Virginia, USA
I.N. Zhelezov
RAS/INR, Moscow, Russia

Production of two types of seamless niobium tubes for hydroforming of RF cavities has been developed. The first type of tubes, developed at DESY, have been spun from sheets and flow formed. The second type of tubing was developed by Black Laboratories in collaboration with the company ATI Wah Chang. These longer length tubes were extruded from a heavily deformed billet, processed for a fine-grained microstructure and flow formed. Several seamless three cell units have been produced by hydroforming at DESY. Some of the units have been treated by buffered chemical polishing and RF tested at JLab. The accelerating gradient Eacc of the units exceeded in most cases 30 MV/m. Three of the 3-cell units from the first type of tubing were combined to three 9-cell niobium cavities at the company E. Zanon. The 3-cell units from extruded tubing are welded together to the fourth 9-cell cavity at JLab. All cavities are in preparation for the RF tests at DESY and JLab. Up to now two of the cavities are electropolished and tested at DESY. The first cavity reached an accelerating gradient of Eacc of ~30 MV/m, the second one ~35 MV/m.

Poster TUPO026 [2.664 MB]

TUPO038

Superconducting RF Cavity Development With UK Industry

464

A.E. Wheelhouse, R. Bate, R.K. Buckley, P. Goudket, A.R. Goulden, P.A. McIntosh, J.F. Orrett
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J.R. Everard, N. Shakespeare
Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom
P. Kneisel, S. Manning, R.A. Rimmer
JLAB, Newport News, Virginia, USA

As part of a STFC Industrial Programme Support Scheme (PIPSS) grant Daresbury Laboratory and Shakespeare Engineering Ltd have fabricated, processed and tested a single cell 1.3 GHz superconducting RF cavity, in collaboration with Jefferson Laboratory. The overall aim of the project through a knowledge exchange programme was to develop the capability of UK industry to fabricate and process a single cell niobium superconducting cavity, as part of a long term strategy to enable UK industry to address the large potential market for superconducting RF structures. As a means of measuring the performance of the fabrication and processing an objective of the programme of work was to achieve an accelerating gradient of greater than 15 MV/m at an unloaded quality factor of 1.0 x 10¹⁰ or better. Three cavities were fabricated by Shakespeare Engineering, and electron beam welded at Jefferson Laboratory in the USA. Processing and testing of the cavities was then performed both at Jefferson Laboratory and at Daresbury Laboratory. The fabrication and process methods are discussed in this paper along with the results obtained from the testing performed in the vertical test facilities.

Poster TUPO038 [0.196 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.

THPO016

Preliminary Results on the Laser Heating Investigation of Hotspots in a Large-Grain Nb Cavity

745

G. Ciovati, C. Baldwin, G. Cheng, R. J. Flood, K. Jordan, P. Kneisel, M.L. Morrone, L. Turlington, K.M. Wilson, S. Zhang
JLAB, Newport News, Virginia, USA
S. M. Anlage
UMD, College Park, Maryland, USA
A.V. Gurevich
Old Dominion University, Norfolk, Virginia, USA
G. Nemes
Astigmat, Santa Clara, USA

Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.

Poster THPO016 [0.983 MB]

THPO057

Superconducting DC and RF Properties of Ingot Niobium

856

P. Dhakal, G. Ciovati, P. Kneisel, R. Myneni
JLAB, Newport News, Virginia, USA

Recently [1, 2], the DC and low frequency magnetic and thermal properties of large-grain niobium samples subjected to different chemical and heat treatment were measured. Here, we extend the similar study to the cylindrical hollow rods of larger diameter, fabricated from new niobium ingots, manufactured by CBMM. The results confirm the influence of chemical and heat-treatment processes on the superconducting properties, with no significant dependence on the impurity concentrations in the original ingots. Furthermore, RF properties such as the surface resistance and quench field of the niobium rods were measured using a TE011 cavity. The hollow niobium rod is the center conductor of this cavity, converting it to a coaxial cavity. The quench field is limited by the critical heat flux through the rods’ cooling channel.
[1] Mondal et al., SRF 2009, Berlin, 2009.
[2] Dhavale et al.,Proc. of the First Int. Symp. on the Superconducting Sci. and Tech. of Ingot Niobium, AIP Conference Proceedings 1352, p. 119 (2011).

Poster THPO057 [1.238 MB]

FRIOA07

SRF Photoinjector Tests at HoBiCat

962

A. Neumann, W. Anders, R. Barday, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A.N. Matveenko, T. Quast, J. Rudolph, S.G. Schubert, J. Völker
HZB, Berlin, Germany
P. Kneisel
JLAB, Newport News, Virginia, USA
G. Lorenz
FHI, Berlin, Germany
R. Nietubyc
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock, Poland
J.K. Sekutowicz
DESY, Hamburg, Germany
J. Smedley
BNL, Upton, Long Island, New York, USA
I. Will
MBI, Berlin, Germany

Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin.
In collaboration with Jefferson Laboratory, DESY and the A. Soltan Institute HZB developed a fully superconducting RF photo-injector as a first step towards a high average current electron source for the BERLinPro ERL. This setup consists of a 1.6 cell superconducting gun cavity with a lead cathode plasma-arc deposited on the half cell backwall and a superconducting solenoid. The system, including a warm diagnostic beam-line section, was recently installed in the HoBiCaT test facility to study beam dynamics within the ERL parameter range. This paper will give an overview of the horizontal cavity tests, dark current studies and beam measurements.

Paper	Title	Page
MOPO004	Modified SRF Photoinjector for the ELBE at HZDR	39
	P. Murcek, A. Arnold, H. Büttig, D. Janssen, M. Justus, P. Michel, G.S. Staats, J. Teichert, R. Xiang HZDR, Dresden, Germany P. Kneisel JLAB, Newport News, Virginia, USA
	The superconducting radio frequency photoinjector (SRF photoinjector) with Cs2Te cathode has been successfully operated under the collaboration of BESSY, DESY, HZDR, and MBI. In order to improve the gradient of the gun cavity and the beam quality, a new modified SRF gun (SRF-gun2008) has been designed. The main updates of the new cavity design for the new injector was publisched before. (ID THPPO022 on the SRF09 Berlin.) This cavity is being fabricated in Jefferson Lab. In this paper the ideas of the redesign of the further parts of the SRF-gun2008 will be presented. The most important issue is the special design of half-cell and choke filter. The cathode cooler is also slightly changed, which simplifies the installation of the cathode cooler in the cavity. The next update is the separation of input and output of the liquid nitrogen supply, for the purpose of the stability of the N2 pressure as well as the better possibility of temperature measurement. Another key point is the implementation of the superconducting solenoid inside the cryomodule. The position of the solenoid can be accurately adjusted with two stepmotors, which is thermally isolated to the solenoid itself.

MOPO070	Preliminary Test Results from 650 MHz Single Cell Medium Beta Cavities for Project X	271
	P. Kneisel, A. Burrill, P. Kushnick, F. Marhauser, R.A. Rimmer JLAB, Newport News, Virginia, USA
	Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. We have fabricated two single cell 650 MHz cavities of a JLab design [1], for possible project X application. Both cavities were manufactured at Jlab from RRR>250 niobium sheet of 4 mm thickness using standard techniques such as deep drawing, EBW, BCP , hydrogen degassing heat treatment, high pressure ultrapure water rinsing and clean room assembly. A detailed description of the design and fabrication procedures is forthcoming [2]. Initially cavity #1 was – after final surface treatment by bcp – measured without any provisions for stiffening . As expected, the pressure sensitivity and the Lorentz Force detuning coefficients were quite high; however, the RF performance was very encouraging: the cavity exhibited a Q-value > 10¹¹ at 1.6K, corresponding to a residual resistance of < 1.5 nOhm The initial gradient was limited to Eacc ~ 18 MV/m, limited by field emission. In a subsequent test, we are re-rinsing the cavity and are making provisions for stiffening up the cavity. By the time of this writing, this test is in progress; the results will be reported at this conference as well as results from the second cavity. [1] F. Marhauser, JLab-TN-10-043 [2] F. Marhauser et al; IPAC 2011 to be published

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]

TUPO026	Nine - Cell Tesla Shape Cavities Produced From Hydroformed Cells	431
	W. Singer, A. Ermakov, G. Kreps, A. Matheisen, X. Singer, K. Twarowski DESY, Hamburg, Germany R. Crooks Black Laboratories, L.L.C., Newport News, USA P. Kneisel JLAB, Newport News, Virginia, USA I.N. Zhelezov RAS/INR, Moscow, Russia
	Production of two types of seamless niobium tubes for hydroforming of RF cavities has been developed. The first type of tubes, developed at DESY, have been spun from sheets and flow formed. The second type of tubing was developed by Black Laboratories in collaboration with the company ATI Wah Chang. These longer length tubes were extruded from a heavily deformed billet, processed for a fine-grained microstructure and flow formed. Several seamless three cell units have been produced by hydroforming at DESY. Some of the units have been treated by buffered chemical polishing and RF tested at JLab. The accelerating gradient Eacc of the units exceeded in most cases 30 MV/m. Three of the 3-cell units from the first type of tubing were combined to three 9-cell niobium cavities at the company E. Zanon. The 3-cell units from extruded tubing are welded together to the fourth 9-cell cavity at JLab. All cavities are in preparation for the RF tests at DESY and JLab. Up to now two of the cavities are electropolished and tested at DESY. The first cavity reached an accelerating gradient of Eacc of ~30 MV/m, the second one ~35 MV/m.
	Poster TUPO026 [2.664 MB]

TUPO038	Superconducting RF Cavity Development With UK Industry	464
	A.E. Wheelhouse, R. Bate, R.K. Buckley, P. Goudket, A.R. Goulden, P.A. McIntosh, J.F. Orrett STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom J.R. Everard, N. Shakespeare Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom P. Kneisel, S. Manning, R.A. Rimmer JLAB, Newport News, Virginia, USA
	As part of a STFC Industrial Programme Support Scheme (PIPSS) grant Daresbury Laboratory and Shakespeare Engineering Ltd have fabricated, processed and tested a single cell 1.3 GHz superconducting RF cavity, in collaboration with Jefferson Laboratory. The overall aim of the project through a knowledge exchange programme was to develop the capability of UK industry to fabricate and process a single cell niobium superconducting cavity, as part of a long term strategy to enable UK industry to address the large potential market for superconducting RF structures. As a means of measuring the performance of the fabrication and processing an objective of the programme of work was to achieve an accelerating gradient of greater than 15 MV/m at an unloaded quality factor of 1.0 x 10¹⁰ or better. Three cavities were fabricated by Shakespeare Engineering, and electron beam welded at Jefferson Laboratory in the USA. Processing and testing of the cavities was then performed both at Jefferson Laboratory and at Daresbury Laboratory. The fabrication and process methods are discussed in this paper along with the results obtained from the testing performed in the vertical test facilities.
	Poster TUPO038 [0.196 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.

THPO016	Preliminary Results on the Laser Heating Investigation of Hotspots in a Large-Grain Nb Cavity	745
	G. Ciovati, C. Baldwin, G. Cheng, R. J. Flood, K. Jordan, P. Kneisel, M.L. Morrone, L. Turlington, K.M. Wilson, S. Zhang JLAB, Newport News, Virginia, USA S. M. Anlage UMD, College Park, Maryland, USA A.V. Gurevich Old Dominion University, Norfolk, Virginia, USA G. Nemes Astigmat, Santa Clara, USA
	Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.
	Poster THPO016 [0.983 MB]

THPO057	Superconducting DC and RF Properties of Ingot Niobium	856
	P. Dhakal, G. Ciovati, P. Kneisel, R. Myneni JLAB, Newport News, Virginia, USA
	Recently [1, 2], the DC and low frequency magnetic and thermal properties of large-grain niobium samples subjected to different chemical and heat treatment were measured. Here, we extend the similar study to the cylindrical hollow rods of larger diameter, fabricated from new niobium ingots, manufactured by CBMM. The results confirm the influence of chemical and heat-treatment processes on the superconducting properties, with no significant dependence on the impurity concentrations in the original ingots. Furthermore, RF properties such as the surface resistance and quench field of the niobium rods were measured using a TE011 cavity. The hollow niobium rod is the center conductor of this cavity, converting it to a coaxial cavity. The quench field is limited by the critical heat flux through the rods’ cooling channel. [1] Mondal et al., SRF 2009, Berlin, 2009. [2] Dhavale et al.,Proc. of the First Int. Symp. on the Superconducting Sci. and Tech. of Ingot Niobium, AIP Conference Proceedings 1352, p. 119 (2011).
	Poster THPO057 [1.238 MB]

FRIOA07	SRF Photoinjector Tests at HoBiCat	962
	A. Neumann, W. Anders, R. Barday, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, A.N. Matveenko, T. Quast, J. Rudolph, S.G. Schubert, J. Völker HZB, Berlin, Germany P. Kneisel JLAB, Newport News, Virginia, USA G. Lorenz FHI, Berlin, Germany R. Nietubyc The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock, Poland J.K. Sekutowicz DESY, Hamburg, Germany J. Smedley BNL, Upton, Long Island, New York, USA I. Will MBI, Berlin, Germany
	Funding: Work funded by the Bundesministerium für Bildung und Forschung and Land Berlin. In collaboration with Jefferson Laboratory, DESY and the A. Soltan Institute HZB developed a fully superconducting RF photo-injector as a first step towards a high average current electron source for the BERLinPro ERL. This setup consists of a 1.6 cell superconducting gun cavity with a lead cathode plasma-arc deposited on the half cell backwall and a superconducting solenoid. The system, including a warm diagnostic beam-line section, was recently installed in the HoBiCaT test facility to study beam dynamics within the ERL parameter range. This paper will give an overview of the horizontal cavity tests, dark current studies and beam measurements.