IPAC2015 - List of Authors (Stratakis, D.)

Paper	Title	Page
MOAD2	RF Breakdown of 805 MHz Cavities in Strong Magnetic Fields	53
	D.L. Bowring, A.V. Kochemirovskiy, M.A. Leonova, A. Moretti, M.A. Palmer, D.W. Peterson, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA A.A. Haase SLAC, Menlo Park, California, USA P.G. Lane, Y. Torun Illinois Institute of Technology, Chicago, Illlinois, USA D. Stratakis BNL, Upton, Long Island, New York, USA
	Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.
	Slides MOAD2 [10.792 MB]
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MOPJE055	Design of an Intense Muon Source with a Carbon and Mercury Target	423
	D. Stratakis, J.S. Berg BNL, Upton, Long Island, New York, USA X.P. Ding UCLA, Los Angeles, California, USA D.V. Neuffer Fermilab, Batavia, Illinois, USA
	Funding: Authored by employees of Brookhaven Science Associates LLC under Contract DE-SC0012704 and with Fermi Research Alliance LLC under Contract DE-AC02-07CH11359 with the United States Department of Energy In high-intensity sources, muons are produced by firing high energy protons onto a target to produce pions. The pions decay to muons which are captured and accelerated. In the present study, we examine the performance of the channel for two different target scenarios: one based on liquid mercury and another one based on a solid carbon target. We produce distributions with the two different target materials and discuss differences in particle spectrum near the sources. We then propagate the distributions through our capture system and compare the full system performance for the two target types.
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MOPMN028	Design of Bunch Compressing System with Suppression of Coherent Synchrotron Radiation for ATF Upgrade	760
	Y.C. Jing, M.G. Fedurin, D. Stratakis BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Brookhaven National Laboratory Accelerator Test Facility (BNL ATF) is in the process of upgrading to ATF2 with higher electron beam energy thus expanding its capabilities. For the fully upgraded electron beam (500 MeV), it will be of great interest to compress the bunch to femto-seconds scale while maintaining high peak current (~7,800 amps) for users. A bunch compressor composed of magnetic chicanes can be utilized for this purpose. However, during such strong compression, beam quality can easily be deteriorated by Coherent Synchrotron Radiation (CSR). In this paper, we present our study for a bunch compressor where this CSR effect is compensated through careful manipulation of phase space. We also show a beam with good quality is preserved through the system by presenting a start to end simulation.
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TUPWA020	BNL ATF II Beamlines Design	1445
	M.G. Fedurin, Y.C. Jing, D. Stratakis, C. Swinson BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Brookhaven National Lab. Accelerator Test Facility (BNL ATF) is currently undergoing a major upgrade (ATF-II). Together with a new location and much improved facilities, the ATF will see an upgrade in its major capabilities: electron beam energy and quality and CO2 laser power. The electron beam energy will be increased in stages, first to 100-150 MeV followed by a further increase to 500 MeV. Combined with the planned increase in CO2 laser power (from 1-100 TW), the ATF-II will be a powerful tool for Advanced Accelerator research. A high-brightness electron beam, produced by a photocathode gun, will be accelerated and optionally delivered to multiple beamlines. Besides the energy range (up to a possible 500 MeV in the final stage) the electron beam can be tailored to each experiment with options such as: small transverse beam size (<10 um), flat beam, short bunch length (<100 fs) and, combined short and small bunch options. This report gives a detailed overview of the ATF-II capabilities and beamlines configuration.
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TUPWI040	End-to-End Simulation of Bunch Merging for a Muon Collider	2336
	Y. Bao, G.G. Hanson UCR, Riverside, California, USA R.B. Palmer, D. Stratakis BNL, Upton, Long Island, New York, USA
	Muon accelerator beams are commonly produced indirectly through pion decay by interaction of a charged particle beam with a target. Efficient muon capture requires the muons to be first phase-rotated by rf cavities into a train of 21 bunches with much reduced energy spread. Since luminosity is proportional to the square of the number of muons per bunch, it is crucial for a Muon Collider to use relatively few bunches with many muons per bunch. In this paper we will describe a bunch merging scheme that should achieve this goal. We present for the first time a complete end-to-end simulation of a 6D bunch merger for a Muon Collider. The 21 bunches arising from the phase-rotator, after some initial cooling, are merged in longitudinal phase space into 7 bunches, which then go through 7 paths with different lengths and reach at the final collecting ”funnel” at the same time. The final single bunch has a transverse and a longitudinal emittance that matches well with the subsequent 6D rectilinear cooling scheme.
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TUPWI059	Influence of Plasma Loading in a Hybrid Muon Cooling Channel	2381
	D. Stratakis BNL, Upton, Long Island, New York, USA B.T. Freemire IIT, Chicago, Illinois, USA K. Yonehara Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In a hybrid 6D cooling channel, cooling is accomplished by reducing the beam momentum through ionization energy loss in wedge absorbers and replenishing the momentum loss in the longitudinal direction with gas-filled rf cavities. While the gas acts as a buffer to prevent rf breakdown, gas ionization may also occur as the beam passes through a HPRF cavity. The resulting plasma, may gain substantial energy from the rf electric field which it can transfer via collisions to the gas, an effect known as plasma loading. In this paper, we investigate the influence of plasma loading on the cooling performance of a rectilinear hybrid channel. With the aid of numerical simulations we examine the sensitivity in cooling performance and plasma loading to key parameters such as the rf gradient and gas pressure.
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WEPWA057	Design Concepts for Muon-Based Accelerators	2633
	R.D. Ryne LBNL, Berkeley, California, USA Y.I. Alexahin, A.D. Bross, K. E. Gollwitzer, N.V. Mokhov, D.V. Neuffer, M.A. Palmer, K. Yonehara Fermilab, Batavia, Illinois, USA J.S. Berg, H.G. Kirk, R.B. Palmer, D. Stratakis BNL, Upton, Long Island, New York, USA S.A. Bogacz JLab, Newport News, Virginia, USA J.-P. Delahaye SLAC, Menlo Park, California, USA T.J. Roberts Muons, Inc, Illinois, USA P. Snopok Illinois Institute of Technology, Chicago, Illinois, USA
	Muon-based accelerators have the potential to enable facilities at both the Intensity and the Energy Frontiers. Muon storage rings can serve as high precision neutrino sources, and a muon collider is an ideal technology for a TeV or multi-TeV collider. Progress in muon accelerator designs has advanced steadily in recent years. In regard to 6D muon cooling, detailed and realistic designs now exist that provide more than 5 order-of-magnitude emittance reduction. Furthermore, detector performance studies indicate that with suitable pixelation and timing resolution, backgrounds in the collider detectors can be significantly reduced thus enabling high quality physics results. Thanks to these and other advances in design & simulation of muon systems, technology development, and systems demonstrations, muon storage-ring-based neutrino sources and a muon collider appear more feasible than ever before. A muon collider is now arguably among the most compelling approaches to a multi-TeV lepton collider. This paper summarizes the current status of design concepts for muon-based accelerators for neutrino factories and a muon collider.
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WEPMA033	Utilizing Gas Filled Cavities for the Generation of an Intense Muon Source	2829
	D. Stratakis BNL, Upton, Long Island, New York, USA D.V. Neuffer Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. A key requirement for designing intense muon sources is operating rf cavities in multi-tesla magnetic fields. Recently, a proof-of-principle experiment demonstrated that an rf cavity filed with high pressure hydrogen gas could meet this goal. In this study, rigorous simulation is used to design and evaluate the performance of an intense muon source with gas filled cavities. We present a new lattice design and compare our results with conventional schemes. We detail the influence of gas pressure on the muon production rate.
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WEPTY047	Thermal and Lorentz Force Analysis of Beryllium Windows for the Rectilinear Muon Cooling Channel	3381
	T.H. Luo, D. Li, S.P. Virostek LBNL, Berkeley, California, USA D.L. Bowring Fermilab, Batavia, Illinois, USA R.B. Palmer, D. Stratakis BNL, Upton, Long Island, New York, USA
	Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed within thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY047
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THPF042	Rectlinear Cooling Scheme for Bright Muon Sources	3792
	D. Stratakis BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Contract No, DE-AC02-07CH11359 with the US Department of Energy. A fast cooling technique is described that simultaneously reduces all six phase-space dimensions of a charged particle beam. In this process, cooling is accomplished by reducing the beam momentum through ionization energy loss in absorbers and replenishing the momentum loss only in the longitudinal direction rf cavities. In this work we describe its main features and describe the main results.
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Paper

Title

Page

RF Breakdown of 805 MHz Cavities in Strong Magnetic Fields

53

D.L. Bowring, A.V. Kochemirovskiy, M.A. Leonova, A. Moretti, M.A. Palmer, D.W. Peterson, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
A.A. Haase
SLAC, Menlo Park, California, USA
P.G. Lane, Y. Torun
Illinois Institute of Technology, Chicago, Illlinois, USA
D. Stratakis
BNL, Upton, Long Island, New York, USA

Ionization cooling of intense muon beams requires the operation of high-gradient, normal-conducting RF structures in the presence of strong magnetic fields. We have measured the breakdown rate in several RF cavities operating at several frequencies. Cavities operating within solenoidal magnetic fields B > 0.25 T show an increased RF breakdown rate at lower gradients compared with similar operation when B = 0 T. Ultimately, this breakdown behavior limits the maximum safe operating gradient of the cavity. Beyond ionization cooling, this issue affects the design of photoinjectors and klystrons, among other applications. We have built an 805 MHz pillbox-type RF cavity to serve as an experimental testbed for this phenomenon. This cavity is designed to study the problem of RF breakdown in strong magnetic fields using various cavity materials and surface treatments, and with precise control over sources of systematic error. We present results from tests in which the cavity was run with all copper surfaces in a variety of magnetic fields.

Slides MOAD2 [10.792 MB]

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MOPJE055

Design of an Intense Muon Source with a Carbon and Mercury Target

423

D. Stratakis, J.S. Berg
BNL, Upton, Long Island, New York, USA
X.P. Ding
UCLA, Los Angeles, California, USA
D.V. Neuffer
Fermilab, Batavia, Illinois, USA

Funding: Authored by employees of Brookhaven Science Associates LLC under Contract DE-SC0012704 and with Fermi Research Alliance LLC under Contract DE-AC02-07CH11359 with the United States Department of Energy
In high-intensity sources, muons are produced by firing high energy protons onto a target to produce pions. The pions decay to muons which are captured and accelerated. In the present study, we examine the performance of the channel for two different target scenarios: one based on liquid mercury and another one based on a solid carbon target. We produce distributions with the two different target materials and discuss differences in particle spectrum near the sources. We then propagate the distributions through our capture system and compare the full system performance for the two target types.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE055

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MOPMN028

Design of Bunch Compressing System with Suppression of Coherent Synchrotron Radiation for ATF Upgrade

760

Y.C. Jing, M.G. Fedurin, D. Stratakis
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Brookhaven National Laboratory Accelerator Test Facility (BNL ATF) is in the process of upgrading to ATF2 with higher electron beam energy thus expanding its capabilities. For the fully upgraded electron beam (500 MeV), it will be of great interest to compress the bunch to femto-seconds scale while maintaining high peak current (~7,800 amps) for users. A bunch compressor composed of magnetic chicanes can be utilized for this purpose. However, during such strong compression, beam quality can easily be deteriorated by Coherent Synchrotron Radiation (CSR). In this paper, we present our study for a bunch compressor where this CSR effect is compensated through careful manipulation of phase space. We also show a beam with good quality is preserved through the system by presenting a start to end simulation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN028

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TUPWA020

BNL ATF II Beamlines Design

1445

M.G. Fedurin, Y.C. Jing, D. Stratakis, C. Swinson
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Brookhaven National Lab. Accelerator Test Facility (BNL ATF) is currently undergoing a major upgrade (ATF-II). Together with a new location and much improved facilities, the ATF will see an upgrade in its major capabilities: electron beam energy and quality and CO2 laser power. The electron beam energy will be increased in stages, first to 100-150 MeV followed by a further increase to 500 MeV. Combined with the planned increase in CO2 laser power (from 1-100 TW), the ATF-II will be a powerful tool for Advanced Accelerator research. A high-brightness electron beam, produced by a photocathode gun, will be accelerated and optionally delivered to multiple beamlines. Besides the energy range (up to a possible 500 MeV in the final stage) the electron beam can be tailored to each experiment with options such as: small transverse beam size (<10 um), flat beam, short bunch length (<100 fs) and, combined short and small bunch options. This report gives a detailed overview of the ATF-II capabilities and beamlines configuration.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA020

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TUPWI040

End-to-End Simulation of Bunch Merging for a Muon Collider

2336

Y. Bao, G.G. Hanson
UCR, Riverside, California, USA
R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA

Muon accelerator beams are commonly produced indirectly through pion decay by interaction of a charged particle beam with a target. Efficient muon capture requires the muons to be first phase-rotated by rf cavities into a train of 21 bunches with much reduced energy spread. Since luminosity is proportional to the square of the number of muons per bunch, it is crucial for a Muon Collider to use relatively few bunches with many muons per bunch. In this paper we will describe a bunch merging scheme that should achieve this goal. We present for the first time a complete end-to-end simulation of a 6D bunch merger for a Muon Collider. The 21 bunches arising from the phase-rotator, after some initial cooling, are merged in longitudinal phase space into 7 bunches, which then go through 7 paths with different lengths and reach at the final collecting ”funnel” at the same time. The final single bunch has a transverse and a longitudinal emittance that matches well with the subsequent 6D rectilinear cooling scheme.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWI040

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TUPWI059

Influence of Plasma Loading in a Hybrid Muon Cooling Channel

2381

D. Stratakis
BNL, Upton, Long Island, New York, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
K. Yonehara
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In a hybrid 6D cooling channel, cooling is accomplished by reducing the beam momentum through ionization energy loss in wedge absorbers and replenishing the momentum loss in the longitudinal direction with gas-filled rf cavities. While the gas acts as a buffer to prevent rf breakdown, gas ionization may also occur as the beam passes through a HPRF cavity. The resulting plasma, may gain substantial energy from the rf electric field which it can transfer via collisions to the gas, an effect known as plasma loading. In this paper, we investigate the influence of plasma loading on the cooling performance of a rectilinear hybrid channel. With the aid of numerical simulations we examine the sensitivity in cooling performance and plasma loading to key parameters such as the rf gradient and gas pressure.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWI059

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WEPWA057

Design Concepts for Muon-Based Accelerators

2633

R.D. Ryne
LBNL, Berkeley, California, USA
Y.I. Alexahin, A.D. Bross, K. E. Gollwitzer, N.V. Mokhov, D.V. Neuffer, M.A. Palmer, K. Yonehara
Fermilab, Batavia, Illinois, USA
J.S. Berg, H.G. Kirk, R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA
S.A. Bogacz
JLab, Newport News, Virginia, USA
J.-P. Delahaye
SLAC, Menlo Park, California, USA
T.J. Roberts
Muons, Inc, Illinois, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Muon-based accelerators have the potential to enable facilities at both the Intensity and the Energy Frontiers. Muon storage rings can serve as high precision neutrino sources, and a muon collider is an ideal technology for a TeV or multi-TeV collider. Progress in muon accelerator designs has advanced steadily in recent years. In regard to 6D muon cooling, detailed and realistic designs now exist that provide more than 5 order-of-magnitude emittance reduction. Furthermore, detector performance studies indicate that with suitable pixelation and timing resolution, backgrounds in the collider detectors can be significantly reduced thus enabling high quality physics results. Thanks to these and other advances in design & simulation of muon systems, technology development, and systems demonstrations, muon storage-ring-based neutrino sources and a muon collider appear more feasible than ever before. A muon collider is now arguably among the most compelling approaches to a multi-TeV lepton collider. This paper summarizes the current status of design concepts for muon-based accelerators for neutrino factories and a muon collider.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA057

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WEPMA033

Utilizing Gas Filled Cavities for the Generation of an Intense Muon Source

2829

D. Stratakis
BNL, Upton, Long Island, New York, USA
D.V. Neuffer
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
A key requirement for designing intense muon sources is operating rf cavities in multi-tesla magnetic fields. Recently, a proof-of-principle experiment demonstrated that an rf cavity filed with high pressure hydrogen gas could meet this goal. In this study, rigorous simulation is used to design and evaluate the performance of an intense muon source with gas filled cavities. We present a new lattice design and compare our results with conventional schemes. We detail the influence of gas pressure on the muon production rate.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA033

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WEPTY047

Thermal and Lorentz Force Analysis of Beryllium Windows for the Rectilinear Muon Cooling Channel

3381

T.H. Luo, D. Li, S.P. Virostek
LBNL, Berkeley, California, USA
D.L. Bowring
Fermilab, Batavia, Illinois, USA
R.B. Palmer, D. Stratakis
BNL, Upton, Long Island, New York, USA

Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed within thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which will produce out of plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY047

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THPF042

Rectlinear Cooling Scheme for Bright Muon Sources

3792

D. Stratakis
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Contract No, DE-AC02-07CH11359 with the US Department of Energy.
A fast cooling technique is described that simultaneously reduces all six phase-space dimensions of a charged particle beam. In this process, cooling is accomplished by reducing the beam momentum through ionization energy loss in absorbers and replenishing the momentum loss only in the longitudinal direction rf cavities. In this work we describe its main features and describe the main results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THPF042

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