LINAC2016 - List of Keywords (plasma)

Paper	Title	Other Keywords	Page
MOPRC029	Experiment of Plasma Discharge on HWR Cavity for In-Situ Surface Cleaning Study	cavity, electron, experiment, operation	133
	A.D. Wu, Y. He, T.C. Jiang, C.L. Li, Y.M. Li, W.M. Yue, S.H. Zhang, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China L.M. Chen Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China L. Yang IHEP, Beijing, People's Republic of China
	Hydrocarbons, which migrate from the vacuum bumps system, will absorb on the cavity surface after periods of operation. The contaminants can reduce the surface electron work function to enhance the field emission effect and restrict the cavity accelerating gradient. The room temperature in-situ plasma surface processing to clean the hydrocarbon contaminants can act as a convenient and efficient technology for the accelerator on line performance recovery. For better control of the discharge inside the cavity, the experiment works on a single HWR cavity aims to research the ignition between the swarm parameters (gas flow, pressure, forward power).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC029
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MOPLR051	Simulation of Gas and Plasma Charge Strippers	target, electron, ion, heavy-ion	248
	O.S.H. Haas, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: This work is supported by the BMBF as part of project 05P15RDRBA. Charge stripping of intense heavy ion beams is a major challenge in current and future linear heavy ion accelerators. Conventional stripping techniques are limited in their applicability, e.g. solid carbon foils suffer from short lifetimes at high intensities. One possible alternative is the use of a plasma as a stripping medium, which the presented work focuses on. The main goal of the studies is the prediction of the final charge state distribution of the ion beam. Rate equations were implemented numerically, taking into account different models for ionization, recombination and energy loss processes. First quantitative results are presented in form of an overview of the charge state distributions of different charge stripping media. For fixed projectile properties and target phase, it is observed that the mean charge state q₀ decreases for increasing nuclear charge Z_\text{T} of the target. Plasmas show significantly increased q₀ for the same Z_T. The width d of the charge state distributions is larger for higher Z_\text{T}. The latter is caused by multiple loss of the projectile and decreases the maximum stripping efficiency by typically less than a factor of 2.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR051
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MOPLR057	Commissioning of the High Intensity Proton Source Developed at INFN-LNS for the European Spallation Source	proton, solenoid, rfq, diagnostics	261
	L. Neri, L. Allegra, A. Amato, G. Calabrese, A.C. Caruso, G. Castro, L. Celona, F. Chines, G. Gallo, S. Gammino, O. Leonardi, A. Longhitano, G. Manno, S. Marletta, D. Mascali, A. Massara, A. Maugeri, S. Passarello, G. Pastore, A. Seminara, A. Spartà, G. Torrisi, S. Vinciguerra INFN/LNS, Catania, Italy M.J. Ferreira, O. Midttun ESS, Lund, Sweden O. Midttun University of Bergen, Bergen, Norway
	At the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) the commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) started some weeks ago. Beam stability at high current intensity is one of the most important parameter for the first steps of the ongoing commissioning. Commissioning plan and preliminary characterization are also presented, with the aim to satisfy the requirement above.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR057
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MOPLR062	European Spallation Source (ESS) Normal Conducting Front End Status Report	rfq, proton, cavity, status	274
	W. Wittmer, P.O. Gustavsson, F. Hellström, G. Hulla ESS, Lund, Sweden I. Bustinduy, P.J. González, G. Harper, S. Varnasseri, C. de la Cruz ESS Bilbao, Zamudio, Spain L. Celona, S. Gammino, L. Neri INFN/LNS, Catania, Italy A.C. Chauveau, D. Chirpaz-Cerbat CEA/IRFU, Gif-sur-Yvette, France F. Grespan, A. Pisent INFN/LNL, Legnaro (PD), Italy P. Mereu INFN-Torino, Torino, Italy O. Midttun University of Bergen, Bergen, Norway O. Piquet, B. Pottin CEA/DSM/IRFU, France
	The European Spallation Source (ESS) will deliver first protons on target by mid 2019. Civil construction of the accelerator tunnel has made good progress and will allow starting installation of the normal conducting frond end (NCFE) by end of 2017. To achieve these milestones the design of all major beam line components have been completed and the construction of the subsystems begun. We report on the advancement of the subsystems and the commissioning progress of the microwave discharge Proton Source (PS-ESS).
	Poster MOPLR062 [1.396 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR062
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TUPRC011	Ongoing Studies of the SuSI ECR Ion Source and Low Energy Beam Transport Line at the MSU NSCL	ion, extraction, ion-source, emittance	438
	A.N. Pham, J. Fogleman, D. Leitner, G. Machicoane, D.E. Neben, S. Renteria, J.W. Stetson, L. Tobos NSCL, East Lansing, Michigan, USA
	Funding: Research supported by Michigan State University and National Science Foundation Award PHY-1415462. Heavy ion accelerator laboratories for nuclear science and rare isotope research require a wide array of high intensity heavy ion beams. Due to their versatility and robustness, Electron Cyclotron Resonance (ECR) ion sources are the choice injectors for the majority of these facilities worldwide. Steady improvements in the performance of ECR ion sources have been successful in providing intense primary beams for facilities such as the National Superconducting Cyclotron Laboratory (NSCL). However, next generation heavy ion beam laboratories, such as the Facility for Rare Isotope Beam (FRIB), require intensities that approaching the limits of current possibility with state of the art ion source technology. In this proceedings, we present the ongoing low energy beam transport characterization efforts of a superconducting ECR ion source injector system at the MSU NSCL.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC011
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TUPRC016	S-Band Booster Design and Emittance Preservation for the Awake e-Injector	emittance, linac, electron, booster	449
	O. Mete Apsimon, R. Apsimon, G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom S. Döbert CERN, Geneva, Switzerland G.X. Xia UMAN, Manchester, United Kingdom
	AWAKE is a proton driven plasma wakefield acceleration experiment at CERN which uses the protons from the SPS. It aims to study the self modulation instability of a proton bunch and the acceleration of an externally injected electron beam in the plasma wakefields, during the so called Phase II until the technical stop of LHC and its injector chain (LS2) in 2019. The external electron beam of 0.1 to 1nC charge per bunch will be generated using an S-band photo injector with a high QE semiconducting cathode. A booster linac was designed to allow variable electron energy for the plasma experiments from 16 to 20 MeV. For an RF gun and booster system, emittance control can be highlighted as a challenging transmission task. Once the beam emittance is compensated at the gun exit and the beam is delivered to the booster with an optimum beam envelope, fringing fields and imperfections in the linac become critical for preserving the injection emittance. This paper summarises the rf design studies in order to preserve the initial beam emittance at the entrance of the linac and alternative mitigation schemes in case of emittance growth.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC016
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TUPRC019	Beam Instabilities in Electron Cyclotron Resonance Ion Sources	ion, cyclotron, ion-source, electron	455
	B.C. Isherwood MSU, East Lansing, Michigan, USA G. Machicoane, G. Pozdeyev NSCL, East Lansing, Michigan, USA G. Machicoane, G. Pozdeyev, Y. Yamazaki FRIB, East Lansing, Michigan, USA
	Funding: This research is funded by joint assistance from the NSF and D.O.E. Accelerator facilities for radioactive beams and low energy nuclear physics such as FRIB require intense, stable ion beam currents in order to achieve required reaction rates for rare and undiscovered isotopes. Presently, the only way to produce intense Continuous Wave beams of highly-charged, medium to heavy-mass ions is with Electron Cyclotron Resonance Ion Sources (ECRIS). The complex nature of these devices causes temporal instabilities to occur, most notably: Slow and fast instabilities. Slow instabilities and drifts, occurring over hours, decay the beam current intensity due to variations in ambient and hardware conditions. These drifts require beam operators to constantly monitor and tune ECRIS plasma parameters in order to maintain experimental beam requirements. Fast instabilities, in the form of ms oscillations, occur at operational parameters needed for high-intensity, high-charge state beams. These oscillations cause sudden drops in beam current of the order of 30%. We present here initial results of recent measurements to investigate these instabilities. Results for slow instabilities indicate a linear decay of beam intensity following a sharp current drop due to a brief source conditioning period. Results for fast instabilities show a relationship between the frequency and amplitude of beam oscillations and the electric potential of the plasma chamber bias disk.
	Poster TUPRC019 [0.817 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC019
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TUPRC032	An Analysis of Fast Sputtering Studies for Ion Confinement Time	ion, electron, ECRIS, ion-source	475
	D.E. Neben, G. Machicoane, A.N. Pham, J.W. Stetson NSCL, East Lansing, Michigan, USA G. Machicoane FRIB, East Lansing, USA G. Parsey MSU, East Lansing, Michigan, USA J.P. Verboncoeur Michigan State University, East Lansing, Michigan, USA
	Funding: This work was supported by Michigan State University and the National Science Foundation: NSF Award Number PHY-1415462 Existing heavy ion facilities such as the National Superconducting Cyclotron Laboratory at Michigan State University rely on Electron Cyclotron Resonance (ECR) ion sources as injectors of highly charged ion beams. Long ion confinement times are necessary to produce dense populations of highly charged ions because of steadily decreasing ionization cross sections with increasing charge state. To further understand ion extraction and confinement we are using a fast sputtering technique first developed at Argonne National Laboratory (ANL) [1] to introduce a small amount of uranium metal into the plasma at a well-defined time. We present an analytical solution to the coupled ion density rate equations for using a piecewise constant neutral density to interpret the fast sputtering method. *R. Vondrasek et al., Rev. Sci. Instrum. 73, 548-551 (2002).
	Poster TUPRC032 [0.699 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC032
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WE2A03	Plasma Processing to Improve the Performance of the SNS Superconducting Linac	cryomodule, linac, cavity, accelerating-gradient	679
	M. Doleans, R. Afanador, J.A. Ball, D.L. Barnhart, W. Blokland, M.T. Crofford, B. DeGraff, S.W. Gold, 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.J. Vandygriff, D.M. Vandygriff 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. An in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help removing adsorbed gases on the RF surface and to reduce its secondary emission yield. Recently, the plasma processing technique has been applied to one offline cryomodule and to two cryomodules in the linac tunnel. Improvement of the accelerating gradient has been observed in all three cryomodules.
	Slides WE2A03 [4.433 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-WE2A03
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THOP11	Ultra-Short Bunch Electron Injector for Awake	electron, gun, wakefield, acceleration	770
	S. Döbert CERN, Geneva, Switzerland
	The proton driven plasma wake field acceleration experiment AWAKE at CERN will start at the end of this year. In 2017 an S-band electron injector producing bunches of a few ps length will be added to probe the wake fields stimulated by a driving proton beam. In the future this electron injector will have to be upgraded to obtain electron bunches with a length of 100 - 200 fs in order to demonstrate injection into a single bucket of the plasma wave and therefore sustainable acceleration with low energy spread. Target bunch parameters for the study are a bunch charge of 100 pC, 100 fs bunch length, an emittance smaller than 2 mm mrad and a beam energy of 100 MeV. The status of a study to achieve these parameters using X-band accelerator hardware and velocity bunching will be presented.
	Slides THOP11 [2.733 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP11
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THPRC030	Plasma Window as Charge Stripper Complement	ion, vacuum, electron, interface	836
	A. Lajoie NSCL, East Lansing, Michigan, USA A. Hershcovitch, P. Thieberger BNL, Upton, Long Island, New York, USA F. Marti FRIB, East Lansing, USA
	Funding: NSF Cooperative Agreement, Award No. PHY-1102511 Modern ion accelerators, particularly heavy ion accelerators, almost universally make use of charge stripping. A challenge facing facilities, as the demand for higher intensity beams rises, is a stripping media that's highly resistant to degradation, such as a recirculating He gas stripper. A method of keeping the He gas localized in a segment along the beamline by means of a Plasma Window (PW) positioned on both sides of the gas stripper has been proposed and the initial design set forth by Ady Hershcovitch. With a cascaded plasma arc being the interface between high pressure stripper and low pressure beamline, the goal is to minimize gas flowrate from the stripper to the beamline in order to maintain sufficient isolation of the He gas. We present the initial results from the test stand developed at Michigan State University and the planned experimental program that will follow.
	Poster THPRC030 [0.626 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPRC030
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THPLR026	Radio Frequency Surface Plasma Source With Solenoidal Magnetic Field	ion, solenoid, ion-source, electron	902
	V.G. Dudnikov, R.P. Johnson Muons, Inc, Illinois, USA G. Dudnikova UMD, College Park, Maryland, USA G. Dudnikova ICT SB RAS, Novosibirsk, Russia B. Han, S. Murrey, C. Stinson ORNL RAD, Oak Ridge, Tennessee, USA T.R. Pennisi, C. Piller, M. Santana, M.P. Stockli, R.F. Welton ORNL, Oak Ridge, Tennessee, USA
	Funding: The work was supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant, DE-SC0011323. Operation of Radio Frequency surfaces plasma sources (RF SPS) with a solenoidal magnetic field are described. RF SPS with solenoidal and saddle antennas are discussed. Dependencies of beam current and extraction current on RF power, gas flow, solenoidal magnetic field are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR026
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Paper

Title

Other Keywords

Page

MOPRC029

Experiment of Plasma Discharge on HWR Cavity for In-Situ Surface Cleaning Study

cavity, electron, experiment, operation

133

A.D. Wu, Y. He, T.C. Jiang, C.L. Li, Y.M. Li, W.M. Yue, S.H. Zhang, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China
L.M. Chen
Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
L. Yang
IHEP, Beijing, People's Republic of China

Hydrocarbons, which migrate from the vacuum bumps system, will absorb on the cavity surface after periods of operation. The contaminants can reduce the surface electron work function to enhance the field emission effect and restrict the cavity accelerating gradient. The room temperature in-situ plasma surface processing to clean the hydrocarbon contaminants can act as a convenient and efficient technology for the accelerator on line performance recovery. For better control of the discharge inside the cavity, the experiment works on a single HWR cavity aims to research the ignition between the swarm parameters (gas flow, pressure, forward power).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPRC029

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MOPLR051

Simulation of Gas and Plasma Charge Strippers

target, electron, ion, heavy-ion

248

O.S.H. Haas, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: This work is supported by the BMBF as part of project 05P15RDRBA.
Charge stripping of intense heavy ion beams is a major challenge in current and future linear heavy ion accelerators. Conventional stripping techniques are limited in their applicability, e.g. solid carbon foils suffer from short lifetimes at high intensities. One possible alternative is the use of a plasma as a stripping medium, which the presented work focuses on. The main goal of the studies is the prediction of the final charge state distribution of the ion beam. Rate equations were implemented numerically, taking into account different models for ionization, recombination and energy loss processes. First quantitative results are presented in form of an overview of the charge state distributions of different charge stripping media. For fixed projectile properties and target phase, it is observed that the mean charge state q₀ decreases for increasing nuclear charge Z_\text{T} of the target. Plasmas show significantly increased q₀ for the same Z_T. The width d of the charge state distributions is larger for higher Z_\text{T}. The latter is caused by multiple loss of the projectile and decreases the maximum stripping efficiency by typically less than a factor of 2.

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR051

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MOPLR057

Commissioning of the High Intensity Proton Source Developed at INFN-LNS for the European Spallation Source

proton, solenoid, rfq, diagnostics

261

L. Neri, L. Allegra, A. Amato, G. Calabrese, A.C. Caruso, G. Castro, L. Celona, F. Chines, G. Gallo, S. Gammino, O. Leonardi, A. Longhitano, G. Manno, S. Marletta, D. Mascali, A. Massara, A. Maugeri, S. Passarello, G. Pastore, A. Seminara, A. Spartà, G. Torrisi, S. Vinciguerra
INFN/LNS, Catania, Italy
M.J. Ferreira, O. Midttun
ESS, Lund, Sweden
O. Midttun
University of Bergen, Bergen, Norway

At the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) the commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) started some weeks ago. Beam stability at high current intensity is one of the most important parameter for the first steps of the ongoing commissioning. Commissioning plan and preliminary characterization are also presented, with the aim to satisfy the requirement above.

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR057

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MOPLR062

European Spallation Source (ESS) Normal Conducting Front End Status Report

rfq, proton, cavity, status

274

W. Wittmer, P.O. Gustavsson, F. Hellström, G. Hulla
ESS, Lund, Sweden
I. Bustinduy, P.J. González, G. Harper, S. Varnasseri, C. de la Cruz
ESS Bilbao, Zamudio, Spain
L. Celona, S. Gammino, L. Neri
INFN/LNS, Catania, Italy
A.C. Chauveau, D. Chirpaz-Cerbat
CEA/IRFU, Gif-sur-Yvette, France
F. Grespan, A. Pisent
INFN/LNL, Legnaro (PD), Italy
P. Mereu
INFN-Torino, Torino, Italy
O. Midttun
University of Bergen, Bergen, Norway
O. Piquet, B. Pottin
CEA/DSM/IRFU, France

The European Spallation Source (ESS) will deliver first protons on target by mid 2019. Civil construction of the accelerator tunnel has made good progress and will allow starting installation of the normal conducting frond end (NCFE) by end of 2017. To achieve these milestones the design of all major beam line components have been completed and the construction of the subsystems begun. We report on the advancement of the subsystems and the commissioning progress of the microwave discharge Proton Source (PS-ESS).

Poster MOPLR062 [1.396 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR062

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TUPRC011

Ongoing Studies of the SuSI ECR Ion Source and Low Energy Beam Transport Line at the MSU NSCL

ion, extraction, ion-source, emittance

438

A.N. Pham, J. Fogleman, D. Leitner, G. Machicoane, D.E. Neben, S. Renteria, J.W. Stetson, L. Tobos
NSCL, East Lansing, Michigan, USA

Funding: Research supported by Michigan State University and National Science Foundation Award PHY-1415462.
Heavy ion accelerator laboratories for nuclear science and rare isotope research require a wide array of high intensity heavy ion beams. Due to their versatility and robustness, Electron Cyclotron Resonance (ECR) ion sources are the choice injectors for the majority of these facilities worldwide. Steady improvements in the performance of ECR ion sources have been successful in providing intense primary beams for facilities such as the National Superconducting Cyclotron Laboratory (NSCL). However, next generation heavy ion beam laboratories, such as the Facility for Rare Isotope Beam (FRIB), require intensities that approaching the limits of current possibility with state of the art ion source technology. In this proceedings, we present the ongoing low energy beam transport characterization efforts of a superconducting ECR ion source injector system at the MSU NSCL.

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC011

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TUPRC016

S-Band Booster Design and Emittance Preservation for the Awake e-Injector

emittance, linac, electron, booster

449

O. Mete Apsimon, R. Apsimon, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
S. Döbert
CERN, Geneva, Switzerland
G.X. Xia
UMAN, Manchester, United Kingdom

AWAKE is a proton driven plasma wakefield acceleration experiment at CERN which uses the protons from the SPS. It aims to study the self modulation instability of a proton bunch and the acceleration of an externally injected electron beam in the plasma wakefields, during the so called Phase II until the technical stop of LHC and its injector chain (LS2) in 2019. The external electron beam of 0.1 to 1nC charge per bunch will be generated using an S-band photo injector with a high QE semiconducting cathode. A booster linac was designed to allow variable electron energy for the plasma experiments from 16 to 20 MeV. For an RF gun and booster system, emittance control can be highlighted as a challenging transmission task. Once the beam emittance is compensated at the gun exit and the beam is delivered to the booster with an optimum beam envelope, fringing fields and imperfections in the linac become critical for preserving the injection emittance. This paper summarises the rf design studies in order to preserve the initial beam emittance at the entrance of the linac and alternative mitigation schemes in case of emittance growth.

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC016

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TUPRC019

Beam Instabilities in Electron Cyclotron Resonance Ion Sources

ion, cyclotron, ion-source, electron

455

B.C. Isherwood
MSU, East Lansing, Michigan, USA
G. Machicoane, G. Pozdeyev
NSCL, East Lansing, Michigan, USA
G. Machicoane, G. Pozdeyev, Y. Yamazaki
FRIB, East Lansing, Michigan, USA

Funding: This research is funded by joint assistance from the NSF and D.O.E.
Accelerator facilities for radioactive beams and low energy nuclear physics such as FRIB require intense, stable ion beam currents in order to achieve required reaction rates for rare and undiscovered isotopes. Presently, the only way to produce intense Continuous Wave beams of highly-charged, medium to heavy-mass ions is with Electron Cyclotron Resonance Ion Sources (ECRIS). The complex nature of these devices causes temporal instabilities to occur, most notably: Slow and fast instabilities. Slow instabilities and drifts, occurring over hours, decay the beam current intensity due to variations in ambient and hardware conditions. These drifts require beam operators to constantly monitor and tune ECRIS plasma parameters in order to maintain experimental beam requirements. Fast instabilities, in the form of ms oscillations, occur at operational parameters needed for high-intensity, high-charge state beams. These oscillations cause sudden drops in beam current of the order of 30%. We present here initial results of recent measurements to investigate these instabilities. Results for slow instabilities indicate a linear decay of beam intensity following a sharp current drop due to a brief source conditioning period. Results for fast instabilities show a relationship between the frequency and amplitude of beam oscillations and the electric potential of the plasma chamber bias disk.

Poster TUPRC019 [0.817 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC019

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TUPRC032

An Analysis of Fast Sputtering Studies for Ion Confinement Time

ion, electron, ECRIS, ion-source

475

D.E. Neben, G. Machicoane, A.N. Pham, J.W. Stetson
NSCL, East Lansing, Michigan, USA
G. Machicoane
FRIB, East Lansing, USA
G. Parsey
MSU, East Lansing, Michigan, USA
J.P. Verboncoeur
Michigan State University, East Lansing, Michigan, USA

Funding: This work was supported by Michigan State University and the National Science Foundation: NSF Award Number PHY-1415462
Existing heavy ion facilities such as the National Superconducting Cyclotron Laboratory at Michigan State University rely on Electron Cyclotron Resonance (ECR) ion sources as injectors of highly charged ion beams. Long ion confinement times are necessary to produce dense populations of highly charged ions because of steadily decreasing ionization cross sections with increasing charge state. To further understand ion extraction and confinement we are using a fast sputtering technique first developed at Argonne National Laboratory (ANL) [1] to introduce a small amount of uranium metal into the plasma at a well-defined time. We present an analytical solution to the coupled ion density rate equations for using a piecewise constant neutral density to interpret the fast sputtering method.
*R. Vondrasek et al., Rev. Sci. Instrum. 73, 548-551 (2002).

Poster TUPRC032 [0.699 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC032

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WE2A03

Plasma Processing to Improve the Performance of the SNS Superconducting Linac

cryomodule, linac, cavity, accelerating-gradient

679

M. Doleans, R. Afanador, J.A. Ball, D.L. Barnhart, W. Blokland, M.T. Crofford, B. DeGraff, S.W. Gold, 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.J. Vandygriff, D.M. Vandygriff
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.
An in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help removing adsorbed gases on the RF surface and to reduce its secondary emission yield. Recently, the plasma processing technique has been applied to one offline cryomodule and to two cryomodules in the linac tunnel. Improvement of the accelerating gradient has been observed in all three cryomodules.

Slides WE2A03 [4.433 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-WE2A03

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THOP11

Ultra-Short Bunch Electron Injector for Awake

electron, gun, wakefield, acceleration

770

S. Döbert
CERN, Geneva, Switzerland

The proton driven plasma wake field acceleration experiment AWAKE at CERN will start at the end of this year. In 2017 an S-band electron injector producing bunches of a few ps length will be added to probe the wake fields stimulated by a driving proton beam. In the future this electron injector will have to be upgraded to obtain electron bunches with a length of 100 - 200 fs in order to demonstrate injection into a single bucket of the plasma wave and therefore sustainable acceleration with low energy spread. Target bunch parameters for the study are a bunch charge of 100 pC, 100 fs bunch length, an emittance smaller than 2 mm mrad and a beam energy of 100 MeV. The status of a study to achieve these parameters using X-band accelerator hardware and velocity bunching will be presented.

Slides THOP11 [2.733 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP11

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THPRC030

Plasma Window as Charge Stripper Complement

ion, vacuum, electron, interface

836

A. Lajoie
NSCL, East Lansing, Michigan, USA
A. Hershcovitch, P. Thieberger
BNL, Upton, Long Island, New York, USA
F. Marti
FRIB, East Lansing, USA

Funding: NSF Cooperative Agreement, Award No. PHY-1102511
Modern ion accelerators, particularly heavy ion accelerators, almost universally make use of charge stripping. A challenge facing facilities, as the demand for higher intensity beams rises, is a stripping media that's highly resistant to degradation, such as a recirculating He gas stripper. A method of keeping the He gas localized in a segment along the beamline by means of a Plasma Window (PW) positioned on both sides of the gas stripper has been proposed and the initial design set forth by Ady Hershcovitch. With a cascaded plasma arc being the interface between high pressure stripper and low pressure beamline, the goal is to minimize gas flowrate from the stripper to the beamline in order to maintain sufficient isolation of the He gas. We present the initial results from the test stand developed at Michigan State University and the planned experimental program that will follow.

Poster THPRC030 [0.626 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPRC030

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THPLR026

Radio Frequency Surface Plasma Source With Solenoidal Magnetic Field

ion, solenoid, ion-source, electron

902

V.G. Dudnikov, R.P. Johnson
Muons, Inc, Illinois, USA
G. Dudnikova
UMD, College Park, Maryland, USA
G. Dudnikova
ICT SB RAS, Novosibirsk, Russia
B. Han, S. Murrey, C. Stinson
ORNL RAD, Oak Ridge, Tennessee, USA
T.R. Pennisi, C. Piller, M. Santana, M.P. Stockli, R.F. Welton
ORNL, Oak Ridge, Tennessee, USA

Funding: The work was supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant, DE-SC0011323.
Operation of Radio Frequency surfaces plasma sources (RF SPS) with a solenoidal magnetic field are described. RF SPS with solenoidal and saddle antennas are discussed. Dependencies of beam current and extraction current on RF power, gas flow, solenoidal magnetic field are presented.

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