2011 Particle Accelerator Conference - List of Authors (Kelly, M.P.)

Paper

Title

Page

A Comparison of Superconducting RF Structures Optimized for β = 0.285

889

Z.A. Conway, R.L. Fischer, M.P. Kelly, A. Kolomiets, B. Mustapha, P.N. Ostroumov
ANL, Argonne, USA

Recent advances in low-beta superconducting RF technology have enabled the proposal and construction of ever-increasing-intensity ion accelerators, e.g. The Facility for Rare Isotope Beams (FRIB) at Michigan State University and Project-X at Fermilab. Superconducting TEM-class structures are required for these accelerators and beam quality preservation and cost efficiency are of the highest importance. This paper presents a comparison of the superconducting TEM-class cavities available for the acceleration of ions in the energy range of 16 to 55 MeV/u in order to guide their selection in future ion accelerator projects.

TUP046

Superconducting 72 MHz β=0.077 Quarter-wave Cavity for ATLAS

892

M.P. Kelly, Z.A. Conway, S.M. Gerbick, M. Kedzie, R.C. Murphy, P.N. Ostroumov, T. Reid
ANL, Argonne, USA

A 72 MHz superconducting (SC) niobium quarter-wave cavity (QWR) optimized for β=0.077 has been built and tested as part of a beam intensity upgrade of the ATLAS SC heavy-ion linac. The two-gap cavity, designed to accelerate ions over the velocity range 0.06<β<0.12 and provide 2.5 MV of accelerating voltage per cavity at T=4.5 Kelvin, is based on a highly optimized electromagnetic design to reduce surface electric and magnetic fields. Horizontal electropolishing on the complete cavity with the helium jacket, is similar to that performed on 1.3 GHz ILC-type cavities and is a first for a low-β TEM cavity. This development is part of a broader effort to demonstrate ~120 mT surface fields with Rs~5 nΩ in 2 K operation for low-β cavities with the aim of substantially reducing the footprint for future ion linacs. First rf cold test results show the highest accelerating gradients (13.4 MV/m, leff=βλ) and voltage/cavity (4.3 MV) achieved for this class of SC cavity.

TUP270

RF and Structural Analysis of the 72.75 MHz QWR for the ATLAS Upgrade

1325

T. Schultheiss, J. Rathke
AES, Medford, NY, USA
J.D. Fuerst, M.P. Kelly, P.N. Ostroumov
ANL, Argonne, USA

Funding: This work was supported by Argonne National Lab under contract # 0F-32381 & 0F32422
An energy upgrade to the heavy-ion accelerator ATLAS at Argonne Lab is progressing*,**. The plans include replacing split-ring cavities with high performance quarter wave resonators. The new 72.75 MHz resonators are designed for optimum ion velocity β=.077 and a record high accelerating voltage of 2.5 MV by modifying the top geometry and reducing the peak surface fields. This new cavity has a longer center conductor than the 10⁹ MHz cavities previously built by ANL with AES assistance, this and the other geometry changes add new engineering requirements to the design. This paper presents the engineering studies that were performed to resolve new issues. These studies include determining structural frequencies of the center conductor and stiffening methods, resonator frequency sensitivity to helium pressure fluctuations, and determining stress levels due to pressure and slow tuning. Evaluation of fast piezoelectric tuner frequency shift to tuner load was also performed and the local cavity shape was optimized based on these results.
* P.N. Ostroumov, et.al, “A New Atlas Efficiency and Intensity Upgrade Project,” SRF2009, tuppo016
** P.N. Ostroumov, et.al., “Efficiency and Intensity Upgrade of the Atlas Facility,” LINAC 2010, MOP045

THOCN5

ATLAS Upgrade

2110

P.N. Ostroumov, A. Barcikowski, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.W.T. MacDonald, B. Mustapha, R.C. Pardo, S.I. Sharamentov
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
ATLAS (Argonne Tandem Linac Accelerator System) upgrade requires several substantial developments in accelerator technologies, such as CW heavy ion RFQ and high-performance cryomodule with low-beta cavities. The upgrade project is well advanced. The physics and engineering design of the RFQ are complete and fabrication of OFE copper parts is in progress. The 3.9-meter length RFQ is composed from 5 strongly coupled segments. High-temperature furnace brazing of the segments is planned for the summer of 2011. The RFQ design includes several innovative features such as trapezoidal vane tip modulation, compact output radial matcher to form an axially symmetric beam. The upgrade project also includes development and construction of a cryomodule containing seven 72.75 MHz SC quarter wave cavities designed for the geometrical β= 0.077 and four SC solenoids. The cavity is designed to obtain an accelerating voltage higher than 2.5 MV. The prototype cavity together with high-power capacitive coupler and piezoelectric tuner has been developed, fabricated and is being tested. This paper reports innovative design features of both RFQ and SRF linac and current status of the project.

Slides THOCN5 [3.070 MB]

Paper	Title	Page
TUP044	A Comparison of Superconducting RF Structures Optimized for β = 0.285	889
	Z.A. Conway, R.L. Fischer, M.P. Kelly, A. Kolomiets, B. Mustapha, P.N. Ostroumov ANL, Argonne, USA
	Recent advances in low-beta superconducting RF technology have enabled the proposal and construction of ever-increasing-intensity ion accelerators, e.g. The Facility for Rare Isotope Beams (FRIB) at Michigan State University and Project-X at Fermilab. Superconducting TEM-class structures are required for these accelerators and beam quality preservation and cost efficiency are of the highest importance. This paper presents a comparison of the superconducting TEM-class cavities available for the acceleration of ions in the energy range of 16 to 55 MeV/u in order to guide their selection in future ion accelerator projects.

TUP046	Superconducting 72 MHz β=0.077 Quarter-wave Cavity for ATLAS	892
	M.P. Kelly, Z.A. Conway, S.M. Gerbick, M. Kedzie, R.C. Murphy, P.N. Ostroumov, T. Reid ANL, Argonne, USA
	A 72 MHz superconducting (SC) niobium quarter-wave cavity (QWR) optimized for β=0.077 has been built and tested as part of a beam intensity upgrade of the ATLAS SC heavy-ion linac. The two-gap cavity, designed to accelerate ions over the velocity range 0.06<β<0.12 and provide 2.5 MV of accelerating voltage per cavity at T=4.5 Kelvin, is based on a highly optimized electromagnetic design to reduce surface electric and magnetic fields. Horizontal electropolishing on the complete cavity with the helium jacket, is similar to that performed on 1.3 GHz ILC-type cavities and is a first for a low-β TEM cavity. This development is part of a broader effort to demonstrate ~120 mT surface fields with Rs~5 nΩ in 2 K operation for low-β cavities with the aim of substantially reducing the footprint for future ion linacs. First rf cold test results show the highest accelerating gradients (13.4 MV/m, leff=βλ) and voltage/cavity (4.3 MV) achieved for this class of SC cavity.

TUP270	RF and Structural Analysis of the 72.75 MHz QWR for the ATLAS Upgrade	1325
	T. Schultheiss, J. Rathke AES, Medford, NY, USA J.D. Fuerst, M.P. Kelly, P.N. Ostroumov ANL, Argonne, USA
	Funding: This work was supported by Argonne National Lab under contract # 0F-32381 & 0F32422 An energy upgrade to the heavy-ion accelerator ATLAS at Argonne Lab is progressing,. The plans include replacing split-ring cavities with high performance quarter wave resonators. The new 72.75 MHz resonators are designed for optimum ion velocity β=.077 and a record high accelerating voltage of 2.5 MV by modifying the top geometry and reducing the peak surface fields. This new cavity has a longer center conductor than the 10⁹ MHz cavities previously built by ANL with AES assistance, this and the other geometry changes add new engineering requirements to the design. This paper presents the engineering studies that were performed to resolve new issues. These studies include determining structural frequencies of the center conductor and stiffening methods, resonator frequency sensitivity to helium pressure fluctuations, and determining stress levels due to pressure and slow tuning. Evaluation of fast piezoelectric tuner frequency shift to tuner load was also performed and the local cavity shape was optimized based on these results. P.N. Ostroumov, et.al, “A New Atlas Efficiency and Intensity Upgrade Project,” SRF2009, tuppo016 ** P.N. Ostroumov, et.al., “Efficiency and Intensity Upgrade of the Atlas Facility,” LINAC 2010, MOP045

THOCN5	ATLAS Upgrade	2110
	P.N. Ostroumov, A. Barcikowski, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.W.T. MacDonald, B. Mustapha, R.C. Pardo, S.I. Sharamentov ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. ATLAS (Argonne Tandem Linac Accelerator System) upgrade requires several substantial developments in accelerator technologies, such as CW heavy ion RFQ and high-performance cryomodule with low-beta cavities. The upgrade project is well advanced. The physics and engineering design of the RFQ are complete and fabrication of OFE copper parts is in progress. The 3.9-meter length RFQ is composed from 5 strongly coupled segments. High-temperature furnace brazing of the segments is planned for the summer of 2011. The RFQ design includes several innovative features such as trapezoidal vane tip modulation, compact output radial matcher to form an axially symmetric beam. The upgrade project also includes development and construction of a cryomodule containing seven 72.75 MHz SC quarter wave cavities designed for the geometrical β= 0.077 and four SC solenoids. The cavity is designed to obtain an accelerating voltage higher than 2.5 MV. The prototype cavity together with high-power capacitive coupler and piezoelectric tuner has been developed, fabricated and is being tested. This paper reports innovative design features of both RFQ and SRF linac and current status of the project.
	Slides THOCN5 [3.070 MB]