IPAC2011 - Classification: 03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques / A14 Advanced Concepts

Paper	Title	Page
WEPZ011	Fast Cooling of Bunches in Compton Storage Rings	2790
	E.V. Bulyak NSC/KIPT, Kharkov, Ukraine J. Urakawa KEK, Ibaraki, Japan F. Zimmermann CERN, Geneva, Switzerland
	We propose an enhancement of laser radiative cooling by utilizing laser pulses of small spatial and temporal dimensions, which interact only with a fraction of an electron bunch circulating in a storage ring. We studied the dynamics of such electron bunch when laser photons scatter off the electrons at a collision point placed in a section with nonzero dispersion. In this case of ‘asymmetric cooling', the stationary energy spread is much smaller than under conditions of regular scattering where the laser spot size is larger than the electron beam; and the synchrotron oscillations are damped faster. Coherent oscillations of large amplitude may be damped within one synchrotron period, so that this method can support the rapid successive injection of many bunches in longitudinal phase space for stacking purposes. Results of extensive simulations are presented for the performance optimization of Compton gamma-ray sources and damping rings.

WEPZ012	Influence of Transition Radiation on Formation of a Bunch Wakefield in a Circular Waveguide	2793
	T.Yu. Alekhina, A.V. Tyukhtin Saint-Petersburg State University, Saint-Petersburg, Russia
	Funding: The Education Agency of Russian Federation. Investigation of a field of a particle bunch in a waveguide loaded with a dielectric is important for the wakefield acceleration (WFA) technique and other problems in the accelerator physics. One of subjects of investigation in this area consists in analysis of transition radiation generated by the bunch flying into (out of) the dielectric structure. This radiation can be both destructive (for WFA) and useful (for diagnostics of bunch or material). We investigate the total field of small bunch crossing a boundary between two dielectrics in the waveguide. It includes a “forced” field and a “free” one. The “forced” field is the field of the charge in the unbounded waveguide (it can contain the wakefield). The “free” field is connected with influence of the boundary (it includes transition radiation). Two cases are analyzed in detail: the bunch flies from vacuum into dielectric and from dielectric into vacuum. The behavior of the field depending on distance and time is explored analytically and numerically. Some interesting physical effects are noted. As well, we make a comparison with the case of intersection between vacuum and cold plasma.

WEPZ013	Design Status of LHeC Linac-Ring Interaction Region	2796
	R. Tomás, J.L. Abelleira, S. Russenschuck, F. Zimmermann CERN, Geneva, Switzerland N.R. Bernard UCLA, Los Angeles, California, USA
	The ECFA-CERN-NuPECC design study for a Large Hadron electron Collider (LHeC) based on the LHC, considers two options, using a ring accelerator like LEP on top of the LHC or adding a recirculating energy-recovery linac tangential to the LHC. In order to obtain the required luminosity with an e^- beam from a linac, with average lepton beam current limited to a few mA, reaching the smallest possible proton beam size is essential. Another constraint is imposed by the need to separate e^- and p beams after the collision without losing too much luminosity from a crossing angle. A further constraint is that the ep collision should occur simultaneously to pp collisions at other LHC interaction points such that the second LHC proton beam must be accommodated in the interaction region too. We present a conceptual layout using detector-integrated combination-separation dipoles and challenging Nb3Sn technology quadrupoles for focusing the colliding proton beam and providing a low-field “hole” to accommodate both the non-colliding proton beam and the lepton beam, and the optics for all three beams. We discuss synchrotron radiation fluxes and the chromatic correction for the lepton final focus.

WEPZ014	Upgrade of the Argonne Wakefield Accelerator Facility (AWA): Commissioning of the RF Gun and Linac Structures for Drive Beam Generation	2799
	M.E. Conde, D.S. Doran, W. Gai, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof ANL, Argonne, USA S.P. Antipov, C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357. Research at the AWA Facility has been focused on the development of electron beam driven wakefield structures. Accelerating gradients of up to 100 MV/m have been excited in dielectric loaded cylindrical structures operating in the microwave range of frequencies. Several upgrades, presently underway, will enable the facility to explore higher accelerating gradients, and also be able to generate longer RF pulses of higher intensity. The major items included in the upgrade are: (a) a new RF gun with a higher quantum efficiency photocathode will replace the RF gun that has been used to generate the drive bunches; (b) the existing RF gun will be used to generate a witness beam to probe the wakefields; (c) three new L-band RF power stations, each providing 25 MW, will be added to the facility; (d) five linac structures will be added to the drive beamline, bringing the beam energy up from 15 MeV to 75 MeV. The upgraded drive beam will consist of bunch trains of up to 32 bunches spaced by 0.77 ns with up to 100 nC per bunch. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level.

WEPZ015	Staging in Two Beam Dielectric Wakefield Accelerators	2802
	J.G. Power, M.E. Conde, W. Gai, C.-J. Jing ANL, Argonne, USA
	Funding: The work is supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 with Argonne National Laboratory. A new experimental program to demonstrate staging in a two beam dielectric wakefield accelerator (DWA) is being planned at the Argonne Wakefield Accelerator facility. DWA uses a drive beam to generate acceleration fields to accelerate a main beam and is one of the most promising advanced acceleration methods being pursued for a future high-energy physics linear collider. Staging is the ability to use two accelerating modules back to back to accelerate a charged particle bunch and it is one of basic requirements of any acceleration method. In this paper, a new beamline design consisting of a fast kicker to pick pulses from the drive bunch train and deliver them to the individual acceleration modules will be presented.

WEPZ016	Generation and Characterization of Electron Bunches with Ramped Current Profiles at the FLASH Facility	2805
	P. Piot Fermilab, Batavia, USA C. Behrens, C. Gerth, M. Vogt DESY, Hamburg, Germany F. Lemery, D. Mihalcea Northern Illinois University, DeKalb, Illinois, USA
	Funding: This work was supported the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10^-1-0051, to Northern Illinois University and the German's Bundesministerium f\"ur Bildung und Forschung We report on the successful generation of electron bunches with current profiles that have a quasi-linear dependency on the longitudinal coordinate. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a linac operating at two frequencies (1.3 and 3.9 GHz) and a bunch compressor. Data taken for various accelerator settings demonstrate the versatility of the method. The produced bunches have parameters well matched to drive high-gradient accelerating field with enhanced transformer ratio in beam-driven accelerators based on sub-mm-sizes dielectric or plasma structures.

WEPZ017	ESTB: A New Beam Test Facility at SLAC	2808
	M.T.F. Pivi, H. Fieguth, C. Hast, R.H. Iverson, J. Jaros, R.K. Jobe, L. Keller, T.V.M. Maruyama, D.R. Walz, M. Woods SLAC, Menlo Park, California, USA
	Funding: Work supported by the Director, Office of Science, High Energy Physics, U.S. DOE under Contract No. DE-AC02-76SF00515. End Station A Test Beam (ESTB) is a beam line at SLAC using a small fraction of the bunches of the 13.6 GeV electron beam from the Linac Coherent Light Source (LCLS), restoring test beam capabilities in the large End Station A (ESA) experimental hall. ESTB will provide one of a kind test beam essential for developing accelerator instrumentation and accelerator R&D, performing particle and particle astrophysics detector research, linear collider machine and detector interface (MDI) R&D studies, development of radiation-hard detectors, and material damage studies with several distinctive features. In the past, 18 institutions participated in the ESA program at SLAC. In stage I, 4 new kicker magnets will be added to divert 5 Hz of the LCLS beam to ESA. A new beam dump is installed and a new Personnel Protection System (PPS) is built in ESA. In stage II, we plan to install a secondary hadron target, able to produce pions up to about 12 GeV/c at 1 particle/pulse. We report about the ESTB commissioning, status and plan for tests.

Paper

Title

Page

Fast Cooling of Bunches in Compton Storage Rings

2790

E.V. Bulyak
NSC/KIPT, Kharkov, Ukraine
J. Urakawa
KEK, Ibaraki, Japan
F. Zimmermann
CERN, Geneva, Switzerland

We propose an enhancement of laser radiative cooling by utilizing laser pulses of small spatial and temporal dimensions, which interact only with a fraction of an electron bunch circulating in a storage ring. We studied the dynamics of such electron bunch when laser photons scatter off the electrons at a collision point placed in a section with nonzero dispersion. In this case of ‘asymmetric cooling', the stationary energy spread is much smaller than under conditions of regular scattering where the laser spot size is larger than the electron beam; and the synchrotron oscillations are damped faster. Coherent oscillations of large amplitude may be damped within one synchrotron period, so that this method can support the rapid successive injection of many bunches in longitudinal phase space for stacking purposes. Results of extensive simulations are presented for the performance optimization of Compton gamma-ray sources and damping rings.

WEPZ012

Influence of Transition Radiation on Formation of a Bunch Wakefield in a Circular Waveguide

2793

T.Yu. Alekhina, A.V. Tyukhtin
Saint-Petersburg State University, Saint-Petersburg, Russia

Funding: The Education Agency of Russian Federation.
Investigation of a field of a particle bunch in a waveguide loaded with a dielectric is important for the wakefield acceleration (WFA) technique and other problems in the accelerator physics. One of subjects of investigation in this area consists in analysis of transition radiation generated by the bunch flying into (out of) the dielectric structure. This radiation can be both destructive (for WFA) and useful (for diagnostics of bunch or material). We investigate the total field of small bunch crossing a boundary between two dielectrics in the waveguide. It includes a “forced” field and a “free” one. The “forced” field is the field of the charge in the unbounded waveguide (it can contain the wakefield). The “free” field is connected with influence of the boundary (it includes transition radiation). Two cases are analyzed in detail: the bunch flies from vacuum into dielectric and from dielectric into vacuum. The behavior of the field depending on distance and time is explored analytically and numerically. Some interesting physical effects are noted. As well, we make a comparison with the case of intersection between vacuum and cold plasma.

WEPZ013

Design Status of LHeC Linac-Ring Interaction Region

2796

R. Tomás, J.L. Abelleira, S. Russenschuck, F. Zimmermann
CERN, Geneva, Switzerland
N.R. Bernard
UCLA, Los Angeles, California, USA

The ECFA-CERN-NuPECC design study for a Large Hadron electron Collider (LHeC) based on the LHC, considers two options, using a ring accelerator like LEP on top of the LHC or adding a recirculating energy-recovery linac tangential to the LHC. In order to obtain the required luminosity with an e^- beam from a linac, with average lepton beam current limited to a few mA, reaching the smallest possible proton beam size is essential. Another constraint is imposed by the need to separate e^- and p beams after the collision without losing too much luminosity from a crossing angle. A further constraint is that the ep collision should occur simultaneously to pp collisions at other LHC interaction points such that the second LHC proton beam must be accommodated in the interaction region too. We present a conceptual layout using detector-integrated combination-separation dipoles and challenging Nb3Sn technology quadrupoles for focusing the colliding proton beam and providing a low-field “hole” to accommodate both the non-colliding proton beam and the lepton beam, and the optics for all three beams. We discuss synchrotron radiation fluxes and the chromatic correction for the lepton final focus.

WEPZ014

Upgrade of the Argonne Wakefield Accelerator Facility (AWA): Commissioning of the RF Gun and Linac Structures for Drive Beam Generation

2799

M.E. Conde, D.S. Doran, W. Gai, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
ANL, Argonne, USA
S.P. Antipov, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Research at the AWA Facility has been focused on the development of electron beam driven wakefield structures. Accelerating gradients of up to 100 MV/m have been excited in dielectric loaded cylindrical structures operating in the microwave range of frequencies. Several upgrades, presently underway, will enable the facility to explore higher accelerating gradients, and also be able to generate longer RF pulses of higher intensity. The major items included in the upgrade are: (a) a new RF gun with a higher quantum efficiency photocathode will replace the RF gun that has been used to generate the drive bunches; (b) the existing RF gun will be used to generate a witness beam to probe the wakefields; (c) three new L-band RF power stations, each providing 25 MW, will be added to the facility; (d) five linac structures will be added to the drive beamline, bringing the beam energy up from 15 MeV to 75 MeV. The upgraded drive beam will consist of bunch trains of up to 32 bunches spaced by 0.77 ns with up to 100 nC per bunch. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level.

WEPZ015

Staging in Two Beam Dielectric Wakefield Accelerators

2802

J.G. Power, M.E. Conde, W. Gai, C.-J. Jing
ANL, Argonne, USA

Funding: The work is supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357 with Argonne National Laboratory.
A new experimental program to demonstrate staging in a two beam dielectric wakefield accelerator (DWA) is being planned at the Argonne Wakefield Accelerator facility. DWA uses a drive beam to generate acceleration fields to accelerate a main beam and is one of the most promising advanced acceleration methods being pursued for a future high-energy physics linear collider. Staging is the ability to use two accelerating modules back to back to accelerate a charged particle bunch and it is one of basic requirements of any acceleration method. In this paper, a new beamline design consisting of a fast kicker to pick pulses from the drive bunch train and deliver them to the individual acceleration modules will be presented.

WEPZ016

Generation and Characterization of Electron Bunches with Ramped Current Profiles at the FLASH Facility

2805

P. Piot
Fermilab, Batavia, USA
C. Behrens, C. Gerth, M. Vogt
DESY, Hamburg, Germany
F. Lemery, D. Mihalcea
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work was supported the Defense Threat Reduction Agency, Basic Research Award # HDTRA1-10^-1-0051, to Northern Illinois University and the German's Bundesministerium f\"ur Bildung und Forschung
We report on the successful generation of electron bunches with current profiles that have a quasi-linear dependency on the longitudinal coordinate. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a linac operating at two frequencies (1.3 and 3.9 GHz) and a bunch compressor. Data taken for various accelerator settings demonstrate the versatility of the method. The produced bunches have parameters well matched to drive high-gradient accelerating field with enhanced transformer ratio in beam-driven accelerators based on sub-mm-sizes dielectric or plasma structures.

WEPZ017

ESTB: A New Beam Test Facility at SLAC

2808

M.T.F. Pivi, H. Fieguth, C. Hast, R.H. Iverson, J. Jaros, R.K. Jobe, L. Keller, T.V.M. Maruyama, D.R. Walz, M. Woods
SLAC, Menlo Park, California, USA

Funding: Work supported by the Director, Office of Science, High Energy Physics, U.S. DOE under Contract No. DE-AC02-76SF00515.
End Station A Test Beam (ESTB) is a beam line at SLAC using a small fraction of the bunches of the 13.6 GeV electron beam from the Linac Coherent Light Source (LCLS), restoring test beam capabilities in the large End Station A (ESA) experimental hall. ESTB will provide one of a kind test beam essential for developing accelerator instrumentation and accelerator R&D, performing particle and particle astrophysics detector research, linear collider machine and detector interface (MDI) R&D studies, development of radiation-hard detectors, and material damage studies with several distinctive features. In the past, 18 institutions participated in the ESA program at SLAC. In stage I, 4 new kicker magnets will be added to divert 5 Hz of the LCLS beam to ESA. A new beam dump is installed and a new Personnel Protection System (PPS) is built in ESA. In stage II, we plan to install a secondary hadron target, able to produce pions up to about 12 GeV/c at 1 particle/pulse. We report about the ESTB commissioning, status and plan for tests.