LINAC2012 - Table of Session: TUPLB (Poster Orals)

Paper

Title

Page

The Swiss FEL RF Gun: RF Design and Thermal Analysis

442

J.-Y. Raguin, M. Bopp, A. Citterio, A. Scherer
PSI, Villigen, Switzerland

We report here on the design of a dual-feed S-band 2.5 cell RF gun, developed in the framework of SwissFEL, capable of operating at 100 Hz repetition rate. As in the LCLS RF gun, z-coupling, to reduce the pulsed surface heating, and a racetrack coupling cell shape, to minimize the quadrupolar component of the fields, have been adopted. The cell lengths and the iris thicknesses are as in the PHIN gun operating at CERN. However the irises aperture has been enlarged to obtain a frequency separation between the operating π mode and the π/2 mode higher than 15 MHz. An amplitude modulation scheme of the RF power, which allows one to obtain a flat plateau of 150 ns for multibunch operation and a reduced average power is presented as well. With an RF pulse duration of 1μs it is shown that operation at 100 MV/m and 100 Hz repetition rate is feasible with very reasonable thermal stresses.

Slides TUPLB01 [1.679 MB]

TUPLB02

Deflecting Structures with Minimized Level of Aberrations

445

V.V. Paramonov
RAS/INR, Moscow, Russia

Funding: in part RBFR N 12-02-00654a
Deflecting structures are now widely used for bunch phase space manipulations either in bunch rotation for special bunch diagnostic or in emittance exchange experiments. As a tool for manipulation, the structure itself should provide the minimal phase space perturbations due to non linear additives in the field distribution. Even if the field of synchronous harmonic is aberration free, the higher space harmonics provide significant non linear additives in the field distribution, leading to emittance growth during phase space manipulation. Criterion of the field quality estimation is developed and deflecting structures are considered for minimization of non linear additives. Examples with almost aberration free total field distributions are presented.

Slides TUPLB02 [0.727 MB]

TUPLB04

Results of Testing of Multi-beam Klystrons for the European XFEL

448

V. Vogel, L. Butkowski, A. Cherepenko, S. Choroba, I. Harders, J. Hartung
DESY, Hamburg, Germany

For the European XFEL multi-beam klystrons, which can produce RF power of 10 MW at an RF frequency of 1.3 GHz, at 1.5 ms pulse length and 10 Hz repetition rate, were chosen as RF power sources. Twenty-seven of horizontal multi-beam klystrons (MBK) together with connection modules (CM) will be installed in the XFEL underground tunnel. The CM will be installed on the MBK and connects the MBK to the pulse transformer with only one HV cable, because the CM has a filament transformer inside as well as all diagnostics for HV and cathode current measurements. MBK prototypes together with CM prototypes have been tested for long time at a test stand at DESY, about 3000 hours of operation for each of horizontal MBK with full RF output power, full pulse length and repetition rate of 10 Hz. Testing of first MBKs from series production has been started. In this paper we will give an overview of the test procedure, summarize the current test results and we will give a comparison of the most important parameters.

TUPLB05

Computational Model Analysis for Experimental Observation of Optical Current Noise Suppression below the Shot-Noise Limit

451

A. Gover
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
A. Nause
University of Tel Aviv, Tel Aviv, Israel

Funding: We acknowledge support of the Israel Science Foundation grant
We report first demonstration of optical frequency current shot-noise suppression in a relativistic e-beam. This process is made possible by collective Coulomb interaction between the electrons of a cold intense beam during beam drift, and is essentially a process of longitudinal beam-plasma oscillation [1]. Suppression of beam current noise below the classical “shot-noise” level has been known in the microwave tubes art [2]. This is the first time that it is demonstrated in the optical regime. We predict that the scheme can be extended to the XUV and possibly to shorter wavelengths with further development of technology. The fundamental current shot-noise determines the level of incoherent spontaneous radiation emission from electron-beam optical radiation sources and SASE-FELs [3]. Suppressing shot-noise would make it possible to attain spontaneous emission sub-radiance [4] and surpass the classical coherence limits of seed-injected FELs. The effect was demonstrated by measuring sub-linear growth as a function of current of the OTR Radiation. This finding indicates that the beam charge homogenizes due to the collective interaction, and its distribution becomes sub-Poissonian.
[1] A. Gover, E. Dyunin, PRL, 102, 154801, 2009
[2] H. Haus, N. Robinson, Proc. IRE, 43, 981 (1955)
[3] P. Emma, et al , Nature Photonics 4, 641 (2010)
[4] A. Dicke, Phys. Rev. 93, 99 (1954)

TUPLB06

Status of the Rare Isotope Science Project in Korea

455

J.-W. Kim
IBS, Daejeon, Republic of Korea

Funding: National Research Foundation of Korea
A heavy-ion accelerator facility is being designed in Korea for the production of rare isotope beams under the name of rare isotope science project (RISP). The project is funded and officially started in Jan. 2012. The accelerator complex is composed of three main accelerators: a superconducting linac to use in-flight fragmentation (IF) method in generating isotope beams, a 70 kW proton cyclotron for the ISOL method, and a superconducting post accelerator for re-acceleration of rare isotope beams to the energy range of 18 MeV/u. The minimum energy of a U beam required for the IF driver is 200 MeV/u at the beam power of 400 kW. The beam current of U ions in high charge states is limited by the performance of existing ECR ion sources. This facility will be unique in the aspect that state-of-art accelerators are facilitated for both the IF and ISOL drivers and combined to produce extreme exotic beams. Also, standalone operation of each accelerator will allow us to accommodate diverse users from beam application fields as well as nuclear physics. The current status of the design efforts will be presented.

Slides TUPLB06 [1.901 MB]

TUPLB07

Reduced-beta Cavities for High-intensity Compact Accelerators

458

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

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357 and WFO 8R268.
This paper reports on the development and testing of a superconducting quarter-wave and a superconducting half-wave resonator. The quarter-wave resonator is designed for β = 0.077 ions, operates at 72 MHz and can provide more than 7.4 MV of accelerating voltage at the design beta, with peak surface fields of 164 mT and 117 MV/m. Operation was limited to this level not by RF surface defects but by our available RF power and administrative limits on x-ray production. A similar goal is being pursued in the development of a half-wave resonator designed for β = 0.29 ions and operated at 325 MHz.

TUPLB08

R&D Towards CW Ion Linacs at ANL

461

P.N. Ostroumov, A. Barcikowski, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.V. Kutsaev, J.W. Morgan, R.C. Murphy, B. Mustapha, D.R. Paskvan, T. Reid, D.L. Schrage, S.I. Sharamentov, K.W. Shepard, G.P. Zinkann
ANL, Argonne, USA

Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under Contract DE-AC02-76CH03000, DE-AC02-06CH11357 and ANL WFO 85Y47.
The accelerator development group in ANL’s Physics Division has engaged in substantial R&D related to CW proton and ion accelerators. Particularly, a 4 meter long 60.625 MHz CW RFQ has been developed, built and is being commissioned with beam. Development and fabrication of a cryomodule with seven 72.75 MHz quarter-wave cavities is complete and it is being assembled. Off-line testing of several QWRs has demonstrated outstanding performance in terms of both accelerating voltage and surface resistance. Both the RFQ and cryomodule were developed and built to upgrade ATLAS to higher efficiency and beam intensities. Another cryomodule with eight 162.5 MHz SC HWRs and eight SC solenoids is being developed and built for Project X at FNAL. We are also developing both an RFQ and cryomodules (housing 176 MHz HWRs) for proton & deuteron acceleration at SNRC (Soreq, Israel). In this paper we discuss ANL-developed technologies for normal-conducting and SC accelerating structures for medium- and high-power CW accelerators, including the projects mentioned above and other developments for applications such as transmutation of spent reactor fuel.

Slides TUPLB08 [1.414 MB]

TUPLB09

Design and Beam Test of Six-electrode BPMs for Second-order Moment Measurement

464

K. Yanagida, H. Hanaki, S. Suzuki
JASRI/SPring-8, Hyogo-ken, Japan

In the SPring-8 linac, four-electrode beam position monitors (BPMs) have been utilized for the measurement of the transverse first-order moments, which correspond to the centroids of beam charge distributions. We have planed to measure the transverse second-order moments of beams to obtain information of beam optics and its energy deviations during the top-up beam injection without destruction of beams. Therefore, six-electrode BPMs with circular and quasi-ellipse cross-sections have been developed on the basis of a newly introduced theory. A low-noise signal processor for the six-electrode BPM has also been developed to perform fine measurement. We expected the following resolutions determined by the S/N ratio of the circuit; the first order moments (beam positions) > 1 μm, and the second order moments with a size > 110 μm. The first beam test was carried out using the six-electrode BPM with circular cross-section and the old signal processor. The measured sensitivities and resolutions of the second-order moments showed good agreement with the theory.

Slides TUPLB09 [8.248 MB]

TUPLB10

Non-destructive Real-time Monitor to Measure 3D-bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-seeded EUV-FEL

467

H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Togashi
JASRI/SPring-8, Hyogo, Japan
T. Matsukawa, H. Minamide
RIKEN ASI, Sendai, Miyagi, Japan
E. Takahashi
RIKEN, Saitama, Japan

Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3-D overlapping electron bunches and higher harmonic generation (HHG) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.

Slides TUPLB10 [2.713 MB]

TUPLB12

Development of Permanent Magnet Focusing System for Klystrons

470

Y. Fuwa, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
S. Fukuda, S. Michizono
KEK, Ibaraki, Japan

The Distributed RF System (DRFS) for the International Linear Collider (ILC) requires thousands of klystrons. The failure rate of the power supply for solenoid focusing coil of each klystron may be a critical issue for a regular operation of the ILC. A permanent magnet beam focusing system can increase reliability and eliminate their power consumption. Since the required magnetic field is not high in this system, inexpensive anisotropic ferrite magnets can be used instead of magnets containing rare earth materials. In order to prove its feasibility, a test model of a permanent magnet focusing beam system is constructed and a power test of the klystron for DRFS with this model is under preparation. The results of magnetic field distribution measurement and the power test will be presented.

Slides TUPLB12 [1.357 MB]

Paper	Title	Page
TUPLB01	The Swiss FEL RF Gun: RF Design and Thermal Analysis	442
	J.-Y. Raguin, M. Bopp, A. Citterio, A. Scherer PSI, Villigen, Switzerland
	We report here on the design of a dual-feed S-band 2.5 cell RF gun, developed in the framework of SwissFEL, capable of operating at 100 Hz repetition rate. As in the LCLS RF gun, z-coupling, to reduce the pulsed surface heating, and a racetrack coupling cell shape, to minimize the quadrupolar component of the fields, have been adopted. The cell lengths and the iris thicknesses are as in the PHIN gun operating at CERN. However the irises aperture has been enlarged to obtain a frequency separation between the operating π mode and the π/2 mode higher than 15 MHz. An amplitude modulation scheme of the RF power, which allows one to obtain a flat plateau of 150 ns for multibunch operation and a reduced average power is presented as well. With an RF pulse duration of 1μs it is shown that operation at 100 MV/m and 100 Hz repetition rate is feasible with very reasonable thermal stresses.
	Slides TUPLB01 [1.679 MB]

TUPLB02	Deflecting Structures with Minimized Level of Aberrations	445
	V.V. Paramonov RAS/INR, Moscow, Russia
	Funding: in part RBFR N 12-02-00654a Deflecting structures are now widely used for bunch phase space manipulations either in bunch rotation for special bunch diagnostic or in emittance exchange experiments. As a tool for manipulation, the structure itself should provide the minimal phase space perturbations due to non linear additives in the field distribution. Even if the field of synchronous harmonic is aberration free, the higher space harmonics provide significant non linear additives in the field distribution, leading to emittance growth during phase space manipulation. Criterion of the field quality estimation is developed and deflecting structures are considered for minimization of non linear additives. Examples with almost aberration free total field distributions are presented.
	Slides TUPLB02 [0.727 MB]

TUPLB04	Results of Testing of Multi-beam Klystrons for the European XFEL	448
	V. Vogel, L. Butkowski, A. Cherepenko, S. Choroba, I. Harders, J. Hartung DESY, Hamburg, Germany
	For the European XFEL multi-beam klystrons, which can produce RF power of 10 MW at an RF frequency of 1.3 GHz, at 1.5 ms pulse length and 10 Hz repetition rate, were chosen as RF power sources. Twenty-seven of horizontal multi-beam klystrons (MBK) together with connection modules (CM) will be installed in the XFEL underground tunnel. The CM will be installed on the MBK and connects the MBK to the pulse transformer with only one HV cable, because the CM has a filament transformer inside as well as all diagnostics for HV and cathode current measurements. MBK prototypes together with CM prototypes have been tested for long time at a test stand at DESY, about 3000 hours of operation for each of horizontal MBK with full RF output power, full pulse length and repetition rate of 10 Hz. Testing of first MBKs from series production has been started. In this paper we will give an overview of the test procedure, summarize the current test results and we will give a comparison of the most important parameters.

TUPLB05	Computational Model Analysis for Experimental Observation of Optical Current Noise Suppression below the Shot-Noise Limit	451
	A. Gover University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel A. Nause University of Tel Aviv, Tel Aviv, Israel
	Funding: We acknowledge support of the Israel Science Foundation grant We report first demonstration of optical frequency current shot-noise suppression in a relativistic e-beam. This process is made possible by collective Coulomb interaction between the electrons of a cold intense beam during beam drift, and is essentially a process of longitudinal beam-plasma oscillation [1]. Suppression of beam current noise below the classical “shot-noise” level has been known in the microwave tubes art [2]. This is the first time that it is demonstrated in the optical regime. We predict that the scheme can be extended to the XUV and possibly to shorter wavelengths with further development of technology. The fundamental current shot-noise determines the level of incoherent spontaneous radiation emission from electron-beam optical radiation sources and SASE-FELs [3]. Suppressing shot-noise would make it possible to attain spontaneous emission sub-radiance [4] and surpass the classical coherence limits of seed-injected FELs. The effect was demonstrated by measuring sub-linear growth as a function of current of the OTR Radiation. This finding indicates that the beam charge homogenizes due to the collective interaction, and its distribution becomes sub-Poissonian. [1] A. Gover, E. Dyunin, PRL, 102, 154801, 2009 [2] H. Haus, N. Robinson, Proc. IRE, 43, 981 (1955) [3] P. Emma, et al , Nature Photonics 4, 641 (2010) [4] A. Dicke, Phys. Rev. 93, 99 (1954)

TUPLB06	Status of the Rare Isotope Science Project in Korea	455
	J.-W. Kim IBS, Daejeon, Republic of Korea
	Funding: National Research Foundation of Korea A heavy-ion accelerator facility is being designed in Korea for the production of rare isotope beams under the name of rare isotope science project (RISP). The project is funded and officially started in Jan. 2012. The accelerator complex is composed of three main accelerators: a superconducting linac to use in-flight fragmentation (IF) method in generating isotope beams, a 70 kW proton cyclotron for the ISOL method, and a superconducting post accelerator for re-acceleration of rare isotope beams to the energy range of 18 MeV/u. The minimum energy of a U beam required for the IF driver is 200 MeV/u at the beam power of 400 kW. The beam current of U ions in high charge states is limited by the performance of existing ECR ion sources. This facility will be unique in the aspect that state-of-art accelerators are facilitated for both the IF and ISOL drivers and combined to produce extreme exotic beams. Also, standalone operation of each accelerator will allow us to accommodate diverse users from beam application fields as well as nuclear physics. The current status of the design efforts will be presented.
	Slides TUPLB06 [1.901 MB]

TUPLB07	Reduced-beta Cavities for High-intensity Compact Accelerators	458
	Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, J.W. Morgan, R.C. Murphy, P.N. Ostroumov, T. Reid ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357 and WFO 8R268. This paper reports on the development and testing of a superconducting quarter-wave and a superconducting half-wave resonator. The quarter-wave resonator is designed for β = 0.077 ions, operates at 72 MHz and can provide more than 7.4 MV of accelerating voltage at the design beta, with peak surface fields of 164 mT and 117 MV/m. Operation was limited to this level not by RF surface defects but by our available RF power and administrative limits on x-ray production. A similar goal is being pursued in the development of a half-wave resonator designed for β = 0.29 ions and operated at 325 MHz.

TUPLB08	R&D Towards CW Ion Linacs at ANL	461
	P.N. Ostroumov, A. Barcikowski, Z.A. Conway, S.M. Gerbick, M. Kedzie, M.P. Kelly, S.V. Kutsaev, J.W. Morgan, R.C. Murphy, B. Mustapha, D.R. Paskvan, T. Reid, D.L. Schrage, S.I. Sharamentov, K.W. Shepard, G.P. Zinkann ANL, Argonne, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of High Energy Physics and Nuclear Physics, under Contract DE-AC02-76CH03000, DE-AC02-06CH11357 and ANL WFO 85Y47. The accelerator development group in ANL’s Physics Division has engaged in substantial R&D related to CW proton and ion accelerators. Particularly, a 4 meter long 60.625 MHz CW RFQ has been developed, built and is being commissioned with beam. Development and fabrication of a cryomodule with seven 72.75 MHz quarter-wave cavities is complete and it is being assembled. Off-line testing of several QWRs has demonstrated outstanding performance in terms of both accelerating voltage and surface resistance. Both the RFQ and cryomodule were developed and built to upgrade ATLAS to higher efficiency and beam intensities. Another cryomodule with eight 162.5 MHz SC HWRs and eight SC solenoids is being developed and built for Project X at FNAL. We are also developing both an RFQ and cryomodules (housing 176 MHz HWRs) for proton & deuteron acceleration at SNRC (Soreq, Israel). In this paper we discuss ANL-developed technologies for normal-conducting and SC accelerating structures for medium- and high-power CW accelerators, including the projects mentioned above and other developments for applications such as transmutation of spent reactor fuel.
	Slides TUPLB08 [1.414 MB]

TUPLB09	Design and Beam Test of Six-electrode BPMs for Second-order Moment Measurement	464
	K. Yanagida, H. Hanaki, S. Suzuki JASRI/SPring-8, Hyogo-ken, Japan
	In the SPring-8 linac, four-electrode beam position monitors (BPMs) have been utilized for the measurement of the transverse first-order moments, which correspond to the centroids of beam charge distributions. We have planed to measure the transverse second-order moments of beams to obtain information of beam optics and its energy deviations during the top-up beam injection without destruction of beams. Therefore, six-electrode BPMs with circular and quasi-ellipse cross-sections have been developed on the basis of a newly introduced theory. A low-noise signal processor for the six-electrode BPM has also been developed to perform fine measurement. We expected the following resolutions determined by the S/N ratio of the circuit; the first order moments (beam positions) > 1 μm, and the second order moments with a size > 110 μm. The first beam test was carried out using the six-electrode BPM with circular cross-section and the old signal processor. The measured sensitivities and resolutions of the second-order moments showed good agreement with the theory.
	Slides TUPLB09 [8.248 MB]

TUPLB10	Non-destructive Real-time Monitor to Measure 3D-bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-seeded EUV-FEL	467
	H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan S. Matsubara, Y. Okayasu, T. Togashi JASRI/SPring-8, Hyogo, Japan T. Matsukawa, H. Minamide RIKEN ASI, Sendai, Miyagi, Japan E. Takahashi RIKEN, Saitama, Japan
	Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3-D overlapping electron bunches and higher harmonic generation (HHG) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.
	Slides TUPLB10 [2.713 MB]

TUPLB12	Development of Permanent Magnet Focusing System for Klystrons	470
	Y. Fuwa, Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan S. Fukuda, S. Michizono KEK, Ibaraki, Japan
	The Distributed RF System (DRFS) for the International Linear Collider (ILC) requires thousands of klystrons. The failure rate of the power supply for solenoid focusing coil of each klystron may be a critical issue for a regular operation of the ILC. A permanent magnet beam focusing system can increase reliability and eliminate their power consumption. Since the required magnetic field is not high in this system, inexpensive anisotropic ferrite magnets can be used instead of magnets containing rare earth materials. In order to prove its feasibility, a test model of a permanent magnet focusing beam system is constructed and a power test of the klystron for DRFS with this model is under preparation. The results of magnetic field distribution measurement and the power test will be presented.
	Slides TUPLB12 [1.357 MB]