LINAC2014 - List of Keywords (dipole)

Paper	Title	Other Keywords	Page
MOPP033	Design, Hardware Tests and First Results From the CLIC Drive Beam Phase Feed-Forward Prototype at CTF3	kicker, optics, feedback, hardware	128
	J. Roberts, A. Andersson, P.K. Skowronski CERN, Geneva, Switzerland P. Burrows, G.B. Christian, C. Perry JAI, Oxford, United Kingdom A. Ghigo, F. Marcellini INFN/LNF, Frascati (Roma), Italy
	In the CLIC two beam acceleration concept the phase synchronisation between the main beam and the RF power extracted from the drive beam must be maintained to within 0.2 degrees of 12 GHz. A drive beam phase feed-forward system with bandwidth above 17.5 MHz is required to reduce the drive beam phase jitter to this level. The system will correct the drive beam phase by varying the path length through a chicane via the use of fast strip line kickers. A prototype of the system is in the final stages of installation at the CLIC test facility CTF3 at CERN. This paper presents results from preparations for the phase feedforward system relating to optics improvements, the development of a slow phase feedback that will be run in parallel with the feedforward system and first tests of the kicker amplifier and kickers.

MOPP049	Dipole Kick due to Geometry Asymmetries in HWR for PXIE	cavity, multipole, linac, cryomodule	165
	P. Berrutti, T.N. Khabiboulline, V.A. Lebedev, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by D.O.E. Contract No. DE-AC02-07CH11359 Project X Injector Experiment (PXIE) will have a family of half wave resonators having frequency=162.5 MHz and beta optimal=0.11. During cavity production, when the niobium parts are assembled and welded together, it is fundamental to control the frequency of the accelerating mode in order to meet the specified operating value. For the HWR of PXIE the tuning will be achieved by trimming one end of the resonator only, this will introduce unwanted asymmetry in the cavity geometry leading to a dipole kick for the particles traveling through the cavity. The cavity geometry will be different from the ideal, once the cavity is assembled, because of small misalignment of the niobium parts and because of the welding shrinkage. Misalignments of the inner conductor and the beam pipes can be expected. The asymmetry due to tuning process along with production misalignments, have been simulated and the equivalent dipole kick has been calculated.
	Poster MOPP049 [1.441 MB]

MOPP058	Z-slicer: A Simple Scheme for Electron Beam Current Profile Shaping in a Linac	electron, laser, radiation, cavity	183
	J.C.T. Thangaraj, C.M. Baffes, D.R. Broemmelsiek, D.J. Crawford, R.M. Thurman-Keup Fermilab, Batavia, Illinois, USA W.B. Wortley University of Rochester, Rochester, New York, USA
	Short bunches are a premium at accelerator facilities and their applications include THz generation, short bunch production, shaped bunch production, etc. In this work we report on the design of an experiment involving an electron beam about 50 MeV that will be intercepted by a set of metallic slits inside a bunch compressor. After the mask, some electrons are scattered while other pass through un-affected. After exiting the bunch compressor, those electrons that were not affected by the slits will appear as short electron bunches. The key advantage of our scheme is its simplicity, tunability and low cost. The scheme does not require any additional hardware such as lasers, undulator, transverse deflecting cavity. The tuning variable is only the RF-chirp and detection of the bunching requires just a skew quad in the chicane and a transverse screen downstream. A thermal analysis suggests that MHz operation of the linac can be sustained under certain beam conditions without any damage to the slit mask.

MOPP070	Final Design for the BERLinPro Main Linac Cavity	HOM, cavity, linac, emittance	217
	A. Neumann, J. Knobloch HZB, Berlin, Germany K. Brackebusch, T. Flisgen, T. Galek, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany B. Riemann, T. Weis DELTA, Dortmund, Germany
	Funding: This work is partly funded by BMBF contract no. 05K10PEA and 05K10HRC The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW LINAC technology for 100-mA-class ERLs. High-current operation requires an effective damping of higher-order modes (HOMs) of the 1.3 GHz main-linac cavities. We have studied elliptical 7-cell cavities based on a modified Cornell ERL design combined with JLab's waveguide HOM damping approach. This paper will summarize the final optimization of the end-cell tuning for minimum external Q of the HOMs, coupler kick calculations of the single TTF fundamental power coupler as well as multipole expansion analysis of the given modes and a discussion on operational aspects.
	Poster MOPP070 [1.561 MB]

MOPP117	Multipole and Field Uniformity Tailoring of a 750 MHz RF Dipole	multipole, cavity, survey, emittance	326
	A. Castilla, J.R. Delayen ODU, Norfolk, Virginia, USA A. Castilla DCI-UG, León, Mexico A. Castilla, J.R. Delayen JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In recent years great interest has been shown in developing rf structures for beam separation, correction of geometrical degradation on luminosity, and diagnostic applications in both lepton and hadron machines. The rf dipole being a very promising one among all of them. The rf dipole has been tested and proven to have attractive properties that include high shunt impedance, low and balance surface fields, absence of lower order modes and far-spaced higher order modes that simplify their damping scheme. As well as to be a compact and versatile design in a considerable range of frequencies, its fairly simple geometry dependency is suitable both for fabrication and surface treatment. The rf dipole geometry can also be optimized for lowering multipacting risk and multipole tailoring to meet machine specific field uniformity tolerances. In the present work a survey of field uniformities, and multipole contents for a set of 750 MHz rf dipole designs is presented as both a qualitative and quantitative analysis of the inherent flexibility of the structure and its limitations.

MOPP127	Wakefield Effects of the Bypass Line in LCLS-II	wakefield, undulator, operation, acceleration	355
	K.L.F. Bane, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE–AC02–76SF00515. In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

MOPP133	Measurements of Cavity Misalignment by Beam Induced HOM Excited in 9-cell Superconducting Cavities	HOM, cavity, simulation, experiment	370
	A. Kuramoto Sokendai, Ibaraki, Japan N. Baboi DESY, Hamburg, Germany H. Hayano KEK, Ibaraki, Japan
	Detection of cavity misalignment in the ILC superconducting cavities inside of the cryomodules can be done by using beam induced Higher Order Modes (HOM). It is beneficial to identify possible source of emittance growth by cavity misalignment. Beam pipe modes which are localized in both ends of the cavity and TE111 1/9 pi mode which is localized in the center of the cavity are focused in this research. Deviations of these electrical centers from beam trajectory reference indicate cavity misalignment and bending. We measured beam-induced HOM in STF cavities of the STF accelerator at KEK in 2012 – 2013 and TESLA cavities of FLASH at DESY in 2013. We could identify beam pipe modes and TE111 1/9 pi mode in STF cavities and TESLA cavities at around 2.1 GHz and 1.6 GHz, both of which were very small signals. The electrical center of these beam pipe mode are studied by stretched wire method, beads perturbation method and simulations by CST MICROWAVE STUDIO 2012 and HFSS 12. In this paper, the results of these measurements and simulations are summarized.

TUPP004	An In-flight Radioactive Ion Separator Design for the ATLAS Facility	ion, quadrupole, target, simulation	446
	B. Mustapha, B. Back, C.R. Hoffman, B.P. Kay, J.A. Nolen, P.N. Ostroumov 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. An in-flight radioactive beam separator, named AIRIS, is being designed to enhance the radioactive beam capabilities of the ATLAS facility at Argonne. In order to serve all the experimental areas while maintaining the stable beam capabilities, the separator design is of broadband type. This design allows the selected radioactive beam to come back on the ATLAS beam line while stable beams continue on the same straight line with the separator turned off. The separation is performed in two steps, the first is magnetic in a chicane made of four magnets and four multipoles, while the second uses an rf sweeper taking advantage of the time separation between the beam of interest and potential contaminants including the primary beam tail. We will report on the progress of the AIRIS design effort with special emphasis on the performance of the rf sweeper.

TUPP108	HOM and Impedance Study of RF Separators for LCLS II	cavity, HOM, superconducting-RF, impedance	674
	S.U. De Silva, J.R. Delayen, B.R.P. Gamage, G.A. Krafft, T. Satogata ODU, Norfolk, Virginia, USA R.G. Olave Old Dominion University, Norfolk, Virginia, USA
	The LCLS-II upgrade requires an rf spreader system to guide bunches into a switchyard delivering beam to two undulators and the primary beam dump. The beam pattern therefore needs a 3-way beam spreader. An rf deflecting cavity concept was proposed that includes both superconducting and normal conducting options. We characterize the higher order modes (HOM) of these rf separator cavities and evaluate beam dynamics effects due to potential HOM excitation. This study includes both short term wake and multi-bunch effects.
	Poster TUPP108 [1.032 MB]

TUPP116	Status of the FERMI II RF Gun at Sincrotrone Trieste	gun, cathode, coupling, emittance	692
	L. Faillace, R.B. Agustsson, P. Frigola, A. Verma RadiaBeam, Santa Monica, California, USA
	Radiabeam Technologies, in collaboration with UCLA, developed a high gradient normal conducting radio frequency (NCRF) 1.6 cell photoinjector system, termed the Fermi Gun II, for the Sincrotrone Trieste (ST) facility. The RF gun has been already in full operation since mid-2013 as the injector for the ST FEL. We report here the current status of the photoinjector system.

THPP007	Uniform Current Density for BLIP Target at Brookhaven 200 MeV Linac	target, linac, octupole, isotope-production	850
	D. Raparia, B. Briscoe, P. Cerniglia, R. Connolly, C. Cullen, D.M. Gassner, R.L. Hulsart, R.F. Lambiase, V. Lo Destro, L.F. Mausner, R.J. Michnoff, P. Thieberger, M. Wilinski BNL, Upton, Long Island, New York, USA
	Bulk of the beam from the linac is used for Brookhaven linac isotope producer (BLIP). The average current from the linac is up 125 uA. At this current BLIP has several target failures and yield uncertainty due to partially melted target salt. To reduce current density, we have tried octupoles in the past but did not produce uniform beam as calculated due to the x-y coupling present in the linac. A beam painting scheme with help of one x and y steers with 90 phase leg at 5 kHz will provide desire current density at the target. This paper discuss beam optics of the blip transport line and beam footprint on the target with given constrains.

THPP013	Prototype Development of the CLIC Crab Cavities	cavity, damping, simulation, impedance	856
	G. Burt, P.K. Ambattu, A.C. Dexter, M. Jenkins, C. Lingwood, B.J. Woolley Cockcroft Institute, Lancaster University, Lancaster, United Kingdom V.A. Dolgashev SLAC, Menlo Park, California, USA P. Goudket, P.A. McIntosh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom A. Grudiev, G. Riddone, A. Solodko, I. Syratchev, R. Wegner, W. Wuensch CERN, Geneva, Switzerland C. Hill, N. Templeton STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	CLIC will require two crab cavities to align the beams to provide an effective head-on collision with a 20 mdeg crossing angle at the interaction point. An X-band system has been chosen for the crab cavities. Three prototype cavities have been developed in order to test the high power characteristics of these cavities. One cavity has been made by UK industry and one has been made using the same process as the CLIC main linac in order to gain understanding of breakdown behaviour in X-band deflecting cavities. The final cavity incorporates mode-damping waveguides on each cell which will eventually contain SiC dampers. This paper details the design, manufacture and preparation of these cavities for testing and a report on their status.

THPP019	Low Kick Coupler for Superconducting Cavities	cavity, emittance, linac, resonance	876
	R.G. Eichhorn, C. Egerer, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Results from the high current, low emittance photo injector at Cornell revealed that even with two opposing input couplers, the beam emittance is affected by the coupler kick. As a result, a coupler with low transverse kick is proposed for use in superconducting accelerating cavities. In this coupler, a rectangular waveguide transforms into a coaxial line inside the beam pipe. The geometry of the coupler is tuned to minimize the transverse kick that is important for linear accelerators with low emittance. The coupler can be used in ERL injectors or other linacs for high brightness light sources.

THPP022	Efficiency of High Order Modes Extraction in the European XFEL Linac	HOM, cavity, damping, linac	883
	A.A. Sulimov, J. Iversen, D. Kostin, W.-D. Möller, D. Reschke, J.K. Sekutowicz, J.H. Thie DESY, Hamburg, Germany D. Karolczyk, K. Kasprzak, S. Myalski, M. Wiencek, A. Zwozniak IFJ-PAN, Kraków, Poland
	The serial production of components for the European XFEL linac was started in 2011 and reached the planned level of 8 cavities (1 module) per week in 2013. The measurements of High Order Modes (HOM) characteristics under cryogenic conditions (2K) are being done at the Accelerating Module Test Facility (AMTF) by the IFJ-PAN Team in collaboration with DESY groups. More than 50 % of the cavities have been already produced and 30 % of the whole amount were measured during either cavity vertical tests or module tests. We present first statistics of these measurements and analyze the efficiency of HOM extraction.
	Poster THPP022 [0.801 MB]

THPP051	Design of a Quasi-Waveguide Multicell Deflecting Cavity for the Advanced Photon Source	cavity, HOM, impedance, damping	966
	A. Lunin, I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev Fermilab, Batavia, Illinois, USA A. Zholents ANL, Argonne, Ilinois, USA
	This paper reports the electromagnetic design of a 2815 MHz Quasi-waveguide Multicell Resonator (called QMiR) being considered as a transverse RF deflecting cavity for the Advanced Photon Source’s (APS) Short Pulse X-ray project. QMiR forms a trapped dipole mode inside a beam vacuum chamber while High Order Modes (HOM) are heavily loaded. It results a sparse HOM spectrum, makes HOM couplers unnecessary and allows to simplify the cavity mechanical design. The form of electrodes is optimized for producing 2 MV of deflecting voltage and keeping low peak surface electric and magnetic fields of 54 MV/m and 75 mT respectively. Results of detailed EM analysis, including HOM damping at the actual geometry of beam vacuum chamber, will be presented.
	Poster THPP051 [1.250 MB]

THPP069	Status and Outlook of the 325 MHz 4-Rod RFQ	rfq, simulation, HOM, impedance	1010
	B. Koubek, H. Podlech, A. Schempp, J.S. Schmidt IAP, Frankfurt am Main, Germany
	In order to built a Radio Frequency Quadrupole (RFQ) at 325 MHz for the FAIR proton linac, a 4-rod structure has been investigated. The RF design, especially the dipole and fringe fields and higher order modes, has been studied with simulations. A prototype has been built and power tested to verify the simulation results and investigate the high power performance. This paper summarizes the results of the research concerning the 325 MHz 4-rod RFQ and gives an overview about the next steps in this project.

THPP071	Proposal of a 325 MHz Ladder-RFQ for the FAIR Proton-Linac	rfq, proton, simulation, quadrupole	1016
	M. Schütt, U. Ratzinger IAP, Frankfurt am Main, Germany R. M. Brodhage GSI, Darmstadt, Germany
	Funding: BMBF 05P12RFRB9 For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The first rf accelerator element is a 325 MHz RFQ accelerating from 95 keV to 3.0 MeV. RFQ’s beyond 300 MHz were realized in 4-Vane-type geometry so far. At IAP there is a tradition in 4-Rod-type RFQ development. This type of RFQ is dominating at lower frequencies. Very promising results have been reached with a ladder type-RFQ, which has been investigated during 2013. In comparison with a traditional 4-Rod RFQ approach the geometry is more convenient at high frequencies. We will show most recent 3D simulations of the frequency tuning possibilities and of a whole cavity demonstrating the power of a ladder type RFQ. An RFQ layout for the new FAIR proton injector will be shown. (see also R. Brodhage, U. Ratzinger, A. Almomani, “Design Study of a High Frequency Proton Ladder RFQ” , Proc. of the 2013 IPAC Conference, Shanghai, China, p. 3788.)

THPP086	ESS DTL Error Study	emittance, DTL, multipole, linac	1047
	M. Comunian, F. Grespan, A. Pisent INFN/LNL, Legnaro (PD), Italy
	The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is designed to operate at 352.2 MHz with a duty cycle of 4% (3 ms pulse length, 14 Hz repetition period) and will accelerate a proton beam of 62.5 mA pulse peak current from 3.62 to 90 MeV. The error study is decisive to define the DTL manufacturing tolerances and to evaluate its robustness. In this paper the DTL performances are shown.

THPP112	Multipacting Optimization of a 750 MHz RF Dipole	cavity, simulation, electron, collider	1111
	A. Castilla, J.R. Delayen ODU, Norfolk, Virginia, USA A. Castilla DCI-UG, León, Mexico A. Castilla, J.R. Delayen JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Crab crossing schemes have been proposed to re-instate luminosity degradation due to crossing angles at the interaction points in next generation colliders to avoid the use of sharp bending magnets and their resulting large synchrotron radiation generation, highly undessirable in the detector region. The rf dipole has been considered for a different set of applications in several machines, both rings and linear colliders. We present in this paper a study of the effects on the multipacting levels and location depending on geometrical variations on the design for a crabbing/deflecting application in a high current (3/0.5 A), high repetition (750 MHz) electron/proton collider, as a matter to provide a comparison point for similar applications of rf dipoles.

Paper

Title

Other Keywords

Page

MOPP033

Design, Hardware Tests and First Results From the CLIC Drive Beam Phase Feed-Forward Prototype at CTF3

kicker, optics, feedback, hardware

128

J. Roberts, A. Andersson, P.K. Skowronski
CERN, Geneva, Switzerland
P. Burrows, G.B. Christian, C. Perry
JAI, Oxford, United Kingdom
A. Ghigo, F. Marcellini
INFN/LNF, Frascati (Roma), Italy

In the CLIC two beam acceleration concept the phase synchronisation between the main beam and the RF power extracted from the drive beam must be maintained to within 0.2 degrees of 12 GHz. A drive beam phase feed-forward system with bandwidth above 17.5 MHz is required to reduce the drive beam phase jitter to this level. The system will correct the drive beam phase by varying the path length through a chicane via the use of fast strip line kickers. A prototype of the system is in the final stages of installation at the CLIC test facility CTF3 at CERN. This paper presents results from preparations for the phase feedforward system relating to optics improvements, the development of a slow phase feedback that will be run in parallel with the feedforward system and first tests of the kicker amplifier and kickers.

MOPP049

Dipole Kick due to Geometry Asymmetries in HWR for PXIE

cavity, multipole, linac, cryomodule

165

P. Berrutti, T.N. Khabiboulline, V.A. Lebedev, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by D.O.E. Contract No. DE-AC02-07CH11359
Project X Injector Experiment (PXIE) will have a family of half wave resonators having frequency=162.5 MHz and beta optimal=0.11. During cavity production, when the niobium parts are assembled and welded together, it is fundamental to control the frequency of the accelerating mode in order to meet the specified operating value. For the HWR of PXIE the tuning will be achieved by trimming one end of the resonator only, this will introduce unwanted asymmetry in the cavity geometry leading to a dipole kick for the particles traveling through the cavity. The cavity geometry will be different from the ideal, once the cavity is assembled, because of small misalignment of the niobium parts and because of the welding shrinkage. Misalignments of the inner conductor and the beam pipes can be expected. The asymmetry due to tuning process along with production misalignments, have been simulated and the equivalent dipole kick has been calculated.

Poster MOPP049 [1.441 MB]

MOPP058

Z-slicer: A Simple Scheme for Electron Beam Current Profile Shaping in a Linac

electron, laser, radiation, cavity

183

J.C.T. Thangaraj, C.M. Baffes, D.R. Broemmelsiek, D.J. Crawford, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA
W.B. Wortley
University of Rochester, Rochester, New York, USA

Short bunches are a premium at accelerator facilities and their applications include THz generation, short bunch production, shaped bunch production, etc. In this work we report on the design of an experiment involving an electron beam about 50 MeV that will be intercepted by a set of metallic slits inside a bunch compressor. After the mask, some electrons are scattered while other pass through un-affected. After exiting the bunch compressor, those electrons that were not affected by the slits will appear as short electron bunches. The key advantage of our scheme is its simplicity, tunability and low cost. The scheme does not require any additional hardware such as lasers, undulator, transverse deflecting cavity. The tuning variable is only the RF-chirp and detection of the bunching requires just a skew quad in the chicane and a transverse screen downstream. A thermal analysis suggests that MHz operation of the linac can be sustained under certain beam conditions without any damage to the slit mask.

MOPP070

Final Design for the BERLinPro Main Linac Cavity

HOM, cavity, linac, emittance

217

A. Neumann, J. Knobloch
HZB, Berlin, Germany
K. Brackebusch, T. Flisgen, T. Galek, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
B. Riemann, T. Weis
DELTA, Dortmund, Germany

Funding: This work is partly funded by BMBF contract no. 05K10PEA and 05K10HRC
The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW LINAC technology for 100-mA-class ERLs. High-current operation requires an effective damping of higher-order modes (HOMs) of the 1.3 GHz main-linac cavities. We have studied elliptical 7-cell cavities based on a modified Cornell ERL design combined with JLab's waveguide HOM damping approach. This paper will summarize the final optimization of the end-cell tuning for minimum external Q of the HOMs, coupler kick calculations of the single TTF fundamental power coupler as well as multipole expansion analysis of the given modes and a discussion on operational aspects.

Poster MOPP070 [1.561 MB]

MOPP117

Multipole and Field Uniformity Tailoring of a 750 MHz RF Dipole

multipole, cavity, survey, emittance

326

A. Castilla, J.R. Delayen
ODU, Norfolk, Virginia, USA
A. Castilla
DCI-UG, León, Mexico
A. Castilla, J.R. Delayen
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In recent years great interest has been shown in developing rf structures for beam separation, correction of geometrical degradation on luminosity, and diagnostic applications in both lepton and hadron machines. The rf dipole being a very promising one among all of them. The rf dipole has been tested and proven to have attractive properties that include high shunt impedance, low and balance surface fields, absence of lower order modes and far-spaced higher order modes that simplify their damping scheme. As well as to be a compact and versatile design in a considerable range of frequencies, its fairly simple geometry dependency is suitable both for fabrication and surface treatment. The rf dipole geometry can also be optimized for lowering multipacting risk and multipole tailoring to meet machine specific field uniformity tolerances. In the present work a survey of field uniformities, and multipole contents for a set of 750 MHz rf dipole designs is presented as both a qualitative and quantitative analysis of the inherent flexibility of the structure and its limitations.

MOPP127

Wakefield Effects of the Bypass Line in LCLS-II

wakefield, undulator, operation, acceleration

355

K.L.F. Bane, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE–AC02–76SF00515.
In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

MOPP133

Measurements of Cavity Misalignment by Beam Induced HOM Excited in 9-cell Superconducting Cavities

HOM, cavity, simulation, experiment

370

A. Kuramoto
Sokendai, Ibaraki, Japan
N. Baboi
DESY, Hamburg, Germany
H. Hayano
KEK, Ibaraki, Japan

Detection of cavity misalignment in the ILC superconducting cavities inside of the cryomodules can be done by using beam induced Higher Order Modes (HOM). It is beneficial to identify possible source of emittance growth by cavity misalignment. Beam pipe modes which are localized in both ends of the cavity and TE111 1/9 pi mode which is localized in the center of the cavity are focused in this research. Deviations of these electrical centers from beam trajectory reference indicate cavity misalignment and bending. We measured beam-induced HOM in STF cavities of the STF accelerator at KEK in 2012 – 2013 and TESLA cavities of FLASH at DESY in 2013. We could identify beam pipe modes and TE111 1/9 pi mode in STF cavities and TESLA cavities at around 2.1 GHz and 1.6 GHz, both of which were very small signals. The electrical center of these beam pipe mode are studied by stretched wire method, beads perturbation method and simulations by CST MICROWAVE STUDIO 2012 and HFSS 12. In this paper, the results of these measurements and simulations are summarized.

TUPP004

An In-flight Radioactive Ion Separator Design for the ATLAS Facility

ion, quadrupole, target, simulation

446

B. Mustapha, B. Back, C.R. Hoffman, B.P. Kay, J.A. Nolen, P.N. Ostroumov
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.
An in-flight radioactive beam separator, named AIRIS, is being designed to enhance the radioactive beam capabilities of the ATLAS facility at Argonne. In order to serve all the experimental areas while maintaining the stable beam capabilities, the separator design is of broadband type. This design allows the selected radioactive beam to come back on the ATLAS beam line while stable beams continue on the same straight line with the separator turned off. The separation is performed in two steps, the first is magnetic in a chicane made of four magnets and four multipoles, while the second uses an rf sweeper taking advantage of the time separation between the beam of interest and potential contaminants including the primary beam tail. We will report on the progress of the AIRIS design effort with special emphasis on the performance of the rf sweeper.

TUPP108

HOM and Impedance Study of RF Separators for LCLS II

cavity, HOM, superconducting-RF, impedance

674

S.U. De Silva, J.R. Delayen, B.R.P. Gamage, G.A. Krafft, T. Satogata
ODU, Norfolk, Virginia, USA
R.G. Olave
Old Dominion University, Norfolk, Virginia, USA

The LCLS-II upgrade requires an rf spreader system to guide bunches into a switchyard delivering beam to two undulators and the primary beam dump. The beam pattern therefore needs a 3-way beam spreader. An rf deflecting cavity concept was proposed that includes both superconducting and normal conducting options. We characterize the higher order modes (HOM) of these rf separator cavities and evaluate beam dynamics effects due to potential HOM excitation. This study includes both short term wake and multi-bunch effects.

Poster TUPP108 [1.032 MB]

TUPP116

Status of the FERMI II RF Gun at Sincrotrone Trieste

gun, cathode, coupling, emittance

692

L. Faillace, R.B. Agustsson, P. Frigola, A. Verma
RadiaBeam, Santa Monica, California, USA

Radiabeam Technologies, in collaboration with UCLA, developed a high gradient normal conducting radio frequency (NCRF) 1.6 cell photoinjector system, termed the Fermi Gun II, for the Sincrotrone Trieste (ST) facility. The RF gun has been already in full operation since mid-2013 as the injector for the ST FEL. We report here the current status of the photoinjector system.

THPP007

Uniform Current Density for BLIP Target at Brookhaven 200 MeV Linac

target, linac, octupole, isotope-production

850

D. Raparia, B. Briscoe, P. Cerniglia, R. Connolly, C. Cullen, D.M. Gassner, R.L. Hulsart, R.F. Lambiase, V. Lo Destro, L.F. Mausner, R.J. Michnoff, P. Thieberger, M. Wilinski
BNL, Upton, Long Island, New York, USA

Bulk of the beam from the linac is used for Brookhaven linac isotope producer (BLIP). The average current from the linac is up 125 uA. At this current BLIP has several target failures and yield uncertainty due to partially melted target salt. To reduce current density, we have tried octupoles in the past but did not produce uniform beam as calculated due to the x-y coupling present in the linac. A beam painting scheme with help of one x and y steers with 90 phase leg at 5 kHz will provide desire current density at the target. This paper discuss beam optics of the blip transport line and beam footprint on the target with given constrains.

THPP013

Prototype Development of the CLIC Crab Cavities

cavity, damping, simulation, impedance

856

G. Burt, P.K. Ambattu, A.C. Dexter, M. Jenkins, C. Lingwood, B.J. Woolley
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
V.A. Dolgashev
SLAC, Menlo Park, California, USA
P. Goudket, P.A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A. Grudiev, G. Riddone, A. Solodko, I. Syratchev, R. Wegner, W. Wuensch
CERN, Geneva, Switzerland
C. Hill, N. Templeton
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

CLIC will require two crab cavities to align the beams to provide an effective head-on collision with a 20 mdeg crossing angle at the interaction point. An X-band system has been chosen for the crab cavities. Three prototype cavities have been developed in order to test the high power characteristics of these cavities. One cavity has been made by UK industry and one has been made using the same process as the CLIC main linac in order to gain understanding of breakdown behaviour in X-band deflecting cavities. The final cavity incorporates mode-damping waveguides on each cell which will eventually contain SiC dampers. This paper details the design, manufacture and preparation of these cavities for testing and a report on their status.

THPP019

Low Kick Coupler for Superconducting Cavities

cavity, emittance, linac, resonance

876

R.G. Eichhorn, C. Egerer, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Results from the high current, low emittance photo injector at Cornell revealed that even with two opposing input couplers, the beam emittance is affected by the coupler kick. As a result, a coupler with low transverse kick is proposed for use in superconducting accelerating cavities. In this coupler, a rectangular waveguide transforms into a coaxial line inside the beam pipe. The geometry of the coupler is tuned to minimize the transverse kick that is important for linear accelerators with low emittance. The coupler can be used in ERL injectors or other linacs for high brightness light sources.

THPP022

Efficiency of High Order Modes Extraction in the European XFEL Linac

HOM, cavity, damping, linac

883

A.A. Sulimov, J. Iversen, D. Kostin, W.-D. Möller, D. Reschke, J.K. Sekutowicz, J.H. Thie
DESY, Hamburg, Germany
D. Karolczyk, K. Kasprzak, S. Myalski, M. Wiencek, A. Zwozniak
IFJ-PAN, Kraków, Poland

The serial production of components for the European XFEL linac was started in 2011 and reached the planned level of 8 cavities (1 module) per week in 2013. The measurements of High Order Modes (HOM) characteristics under cryogenic conditions (2K) are being done at the Accelerating Module Test Facility (AMTF) by the IFJ-PAN Team in collaboration with DESY groups. More than 50 % of the cavities have been already produced and 30 % of the whole amount were measured during either cavity vertical tests or module tests. We present first statistics of these measurements and analyze the efficiency of HOM extraction.

Poster THPP022 [0.801 MB]

THPP051

Design of a Quasi-Waveguide Multicell Deflecting Cavity for the Advanced Photon Source

cavity, HOM, impedance, damping

966

A. Lunin, I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
A. Zholents
ANL, Argonne, Ilinois, USA

This paper reports the electromagnetic design of a 2815 MHz Quasi-waveguide Multicell Resonator (called QMiR) being considered as a transverse RF deflecting cavity for the Advanced Photon Source’s (APS) Short Pulse X-ray project. QMiR forms a trapped dipole mode inside a beam vacuum chamber while High Order Modes (HOM) are heavily loaded. It results a sparse HOM spectrum, makes HOM couplers unnecessary and allows to simplify the cavity mechanical design. The form of electrodes is optimized for producing 2 MV of deflecting voltage and keeping low peak surface electric and magnetic fields of 54 MV/m and 75 mT respectively. Results of detailed EM analysis, including HOM damping at the actual geometry of beam vacuum chamber, will be presented.

Poster THPP051 [1.250 MB]

THPP069

Status and Outlook of the 325 MHz 4-Rod RFQ

rfq, simulation, HOM, impedance

1010

B. Koubek, H. Podlech, A. Schempp, J.S. Schmidt
IAP, Frankfurt am Main, Germany

In order to built a Radio Frequency Quadrupole (RFQ) at 325 MHz for the FAIR proton linac, a 4-rod structure has been investigated. The RF design, especially the dipole and fringe fields and higher order modes, has been studied with simulations. A prototype has been built and power tested to verify the simulation results and investigate the high power performance. This paper summarizes the results of the research concerning the 325 MHz 4-rod RFQ and gives an overview about the next steps in this project.

THPP071

Proposal of a 325 MHz Ladder-RFQ for the FAIR Proton-Linac

rfq, proton, simulation, quadrupole

1016

M. Schütt, U. Ratzinger
IAP, Frankfurt am Main, Germany
R. M. Brodhage
GSI, Darmstadt, Germany

Funding: BMBF 05P12RFRB9
For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The first rf accelerator element is a 325 MHz RFQ accelerating from 95 keV to 3.0 MeV. RFQ’s beyond 300 MHz were realized in 4-Vane-type geometry so far. At IAP there is a tradition in 4-Rod-type RFQ development. This type of RFQ is dominating at lower frequencies. Very promising results have been reached with a ladder type-RFQ, which has been investigated during 2013. In comparison with a traditional 4-Rod RFQ approach the geometry is more convenient at high frequencies. We will show most recent 3D simulations of the frequency tuning possibilities and of a whole cavity demonstrating the power of a ladder type RFQ. An RFQ layout for the new FAIR proton injector will be shown. (see also R. Brodhage, U. Ratzinger, A. Almomani, “Design Study of a High Frequency Proton Ladder RFQ” , Proc. of the 2013 IPAC Conference, Shanghai, China, p. 3788.)

THPP086

ESS DTL Error Study

emittance, DTL, multipole, linac

1047

M. Comunian, F. Grespan, A. Pisent
INFN/LNL, Legnaro (PD), Italy

The Drift Tube Linac (DTL) of the European Spallation Source (ESS) is designed to operate at 352.2 MHz with a duty cycle of 4% (3 ms pulse length, 14 Hz repetition period) and will accelerate a proton beam of 62.5 mA pulse peak current from 3.62 to 90 MeV. The error study is decisive to define the DTL manufacturing tolerances and to evaluate its robustness. In this paper the DTL performances are shown.

THPP112

Multipacting Optimization of a 750 MHz RF Dipole

cavity, simulation, electron, collider

1111

A. Castilla, J.R. Delayen
ODU, Norfolk, Virginia, USA
A. Castilla
DCI-UG, León, Mexico
A. Castilla, J.R. Delayen
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Crab crossing schemes have been proposed to re-instate luminosity degradation due to crossing angles at the interaction points in next generation colliders to avoid the use of sharp bending magnets and their resulting large synchrotron radiation generation, highly undessirable in the detector region. The rf dipole has been considered for a different set of applications in several machines, both rings and linear colliders. We present in this paper a study of the effects on the multipacting levels and location depending on geometrical variations on the design for a crabbing/deflecting application in a high current (3/0.5 A), high repetition (750 MHz) electron/proton collider, as a matter to provide a comparison point for similar applications of rf dipoles.