IBIC2014 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOPF27	Simulation and First Results of the ELBE SRF Gun II	gun, laser, SRF, simulation	106
	P.N. Lu, A. Arnold, U. Lehnert, P. Murcek, J. Teichert, H. Vennekate, R. Xiang HZDR, Dresden, Germany
	In Rossendorf, a 3 and one half cell cavity SRF photo injector has been installed, which promises to accelerate the electron beam to 9 MeV in 0.5 meter. The gun is expected to operate both in the 13 MHz mode with a bunch charge of 77 pC, or in the 500 kHz mode, with a 1 nC charge. The simulation presented in this contribution includes particle tracking in the new cavity itself with the ASTRA code, and in the bunch transport line in the ELBE beam lines with the elegant code. The measured profile and time structure of the UV laser on the cathode are utilized to specify the electron bunch parameters. Then a single bunch of electrons is tracked in the cavity field that was calculated by Superfish, with space charge effects considered. From the exit of the cavity, the electron bunch has a relatively high energy so we ignore the space charge effect there and apply elegant to track the particles through the magnet elements and accelerator modules. The main purpose of this simulation is to find the optimized parameters for different beam transport tasks. As a first experimental result of the photoinjector, energy and phase space measurement will be also presented in the paper. Both the slit mask and the quadrupole scan methods are applied to measure the beam emittance. An obvious progression will be to compare the results from this gun with those from the ELBE SRF gun I.
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MOPD05	Dual Transverse and Longitudinal Streak Camera Imaging at ELSA	damping, diagnostics, synchrotron, electron	144
	M.T. Switka, F. Frommberger, P. Hänisch, W. Hillert, M. Schedler ELSA, Bonn, Germany
	Funding: Funded by the German Research Foundation (DFG) within Colaborative Research Center (SFB/TRR) 16 The electron pulse stretcher ring ELSA located at Bonn University provides 0.5 – 3.5 GeV polarized and non-polarized electron beams for external experimental stations. A streak camera system has been installed to capture time resolved images of beam dynamics ranging from nanoseconds to several milliseconds. Particular attention was drawn to the capability of simultaneous imaging of both transverse beam dimensions, hence providing information of all spatial dimensions in one synchroscan or slow sweep measurement. Incoherent and coherent beam instabilities, especially at high stored beam currents, are subject of analysis due to the planned intensity upgrade towards 200 mA for standard operation. The current resolution performance of the imaging system and machine relevant measurements are presented.
	Poster MOPD05 [6.133 MB]
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MOPD19	Bunch Arrival Time Monitor for PAL-XFEL	timing, pick-up, LLRF, electronics	191
	J.H. Hong, J.H. Han, H.-S. Kang, C. Kim, H. Yang PAL, Pohang, Kyungbuk, Republic of Korea
	The X-ray Free Electron Laser project in Pohang Accelerator Laboratory (PAL-XFEL) requires high stability of bunch arrival time, and measurement resolution better than a few femtoseconds. The pickups of the electron Bunch Arrival time Monitor (BAM) for PAL-XFEL have been developed and simulated. The BAM pickups are based on an S-band monopole cavity with two coupling loops. The prototype BAM has been fabricated and installed downstream of the accelerating column at the Injector Test Facility (ITF) for PAL-XFEL. In this paper we will present the recent measurement results on the beam test of the BAM as well as a proposed strategy for developing the BAM for PAL-XFEL.
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TUCYB2	Pulsed Green Laser Wire System for Effective Inverse Compton Scattering	laser, electron, emittance, experiment	254
	A.A. Rawankar, N. Terunuma, J. Urakawa Sokendai, Ibaraki, Japan T. Akagi, A.S. Aryshev, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan D. Jehanno LAL, Orsay, France K. Sakaue Waseda University, Tokyo, Japan
	Funding: This work has been supported by the Quantum Beam Technology Program of the Japanese Ministry of Education, Culture, Sports, Science,and Technology(MEXT). Laser-Compton scattering has become an important technique for beam diagnostics of the latest accelerators. In order to develop technologies for low emittance beams, an Accelerator Test facility (ATF) was built at KEK. It consists of an electron linac, a damping ring in which beam emittance is reduced, and an extraction line. For emittance measurement we are developing a new type of beam profile monitor which works on the principle of inverse Compton scattering between electron and laser light. In order to achieve effective collision of photon and electron, a pulsed and very thin size laser is required. Laser wire is one technique of measuring a small beam size. With green lasers, which are converted to second harmonics from IR pulsed laser, minimum beam waist is half of the beam waist obtained using infrared (IR) laser oscillator. Therefore, it is possible to obtain beam waist less than 5 μm using green laser pulse, which is required for effective photon-electron collision. First, pulsed IR seed laser is amplified with 1.5 meter long PCF based amplifier system. This pulsed IR laser is converted to second harmonics with a non-linear crystal. Pulsed green laser is injected inside four mirror optical cavity to obtain very small beam waist at interaction point (IP). Using a pulsed compact laser wire, we can measure 10 um electron beams in vertical directions. We report the development of the pulsed green laser and parameters of compact four mirror optical cavity for effective inverse Compton scattering.
	Slides TUCYB2 [2.632 MB]
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TUPF05	Production Process for the European XFEL Re-Entrant Cavity BPM	cryomodule, quadrupole, vacuum, controls	307
	C.S. Simon, P. Carbonnier, P. Contrepois, F. Éozénou, Y. Gasser, O. Napoly, J. Novo, C. Servouin CEA/DSM/IRFU, France C. Boulch, Y. Gasser CEA/IRFU, Gif-sur-Yvette, France P. Daniel-Thomas, F. Gouit CEA, Gif-sur-Yvette, France J. Kruse, D. Nölle, M. Schalwat, S. Vilcins DESY, Hamburg, Germany N. Rouvière IPN, Orsay, France
	As In-Kind contributor to the E-XFEL project, CEA is committed to the procurement of around one third (31) cold beam position monitors (BPM) of the re-entrant RF cavities type and to the assembly on the Saclay site of the 101 cryomodules of the superconducting linac. Each cryomodule is equipped with a beam position monitor connected to a quadrupole at the high-energy end of the cavity string. The industrial process of those BPMs, used in an ultra-clean environment at cryogenic temperature, includes several steps and involves a quality control in collaboration with industrial partners. This paper describes the different steps of the re-entrant cavity BPM fabrication process: machining, copper coating, thermal treatment, EB welding, cleaning and mounting in clean room on the quadrupole. Problems encountered and the lessons learnt will be also reported.
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TUPF06	Commissioning of the Electronics for HOM-based Beam Diagnostics at the 3.9 GHz Accelerating Module at FLASH	HOM, electronics, alignment, dipole	311
	N. Baboi, O. Hensler, L. Shi, T. Wamsat DESY, Hamburg, Germany N. Eddy, B.J. Fellenz Fermilab, Batavia, Illinois, USA P. Zhang CERN, Geneva, Switzerland
	Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453. Transverse Higher Order Modes (HOM) excited by electron beams in the 3.9 GHz accelerating cavities at FLASH may damage the beam quality. They can be reduced by extracting their energy through special couplers and by aligning the beam in the cavity. Electronics has been designed at FNAL for monitoring some of the potentially most damaging HOMs. This may be used for beam centering and therefore reducing the HOM effects. Moreover, the signals can be potentially calibrated into beam offset, so that they could be used as beam position monitors (HOM-BPM). The specifications of the monitors have been defined during an extensive study on the 4-cavity accelerating module installed at FLASH. Signals around 5.44 GHz have been chosen for higher precision measurements. However these signals propagate into the entire 1.2 m long module. Therefore in addition modes at about 9 GHz were selected for localized measurements in each cavity. The electronics has been recently installed at FLASH. The commissioning results will be presented in this paper. Instabilities previously observed in a test electronics as well as the HOM-BPMs in 1.3 GHz cavities will also be investigated. This electronics will also serve as a prototype for the electronics developed for the 3.9 GHz cavities at the European XFEL. L. Shi et al., this Conference **T. Wamsat et al., this Conference
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TUPF07	FLASH Undulator BPM Commissioning and Beam Characterization Results	electronics, undulator, pick-up, controls	315
	D. Lipka, N. Baboi, D. Nölle, G. Petrosyan, S. Vilcins DESY, Hamburg, Germany R. Baldinger, R. Ditter, B. Keil, W. Koprek, R. Kramert, G. Marinkovic, M. Roggli, M. Stadler PSI, Villigen PSI, Switzerland
	Recently, the commissioning of FLASH2 has started, a new soft X-ray FEL undulator line at the DESY FLASH facility. In the FLASH2 undulator intersections, the beam positions are measured by 17 cavity beam position monitor (CBPM) pick-ups and electronics* developed for the European XFEL (E-XFEL). In addition four CBPMs are available at FLASH1 for test and development. The new CBPM system enables an unprecedented position and charge resolution at FLASH, thus allowing further analysis and optimization of the FLASH beam quality and overall accelerator performance. Results of first beam measurements as well as correlations with other FLASH diagnostics systems are reported. * M. Stadler et al., “Low-Q Cavity BPM Electronics for E-XFEL, FLASH-2 and SwissFEL”, this conference.
	Poster TUPF07 [1.112 MB]
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TUPF10	Stability Study of the Higher Order Mode Beam Position Monitors at the Accelerating Cavities at FLASH	dipole, HOM, electronics, polarization	327
	L. Shi, N. Baboi DESY, Hamburg, Germany R.M. Jones UMAN, Manchester, United Kingdom
	When electron beams traverse an accelerating structure, higher order modes (HOMs) are excited. They can be used for beam diagnostic purposes. Both 1.3 GHz and 3.9 GHz superconducting accelerating cavities at FLASH linac, DESY, are equipped with electronics for beam position monitoring, which are based on HOM signals from special couplers. These monitors provide the beam position without additional vacuum components and at low cost. Moreover, they can be used to align the beam in the cavities to reduce the HOM effects on the beam. However, the HOMBPM (Higher Order Mode based Beam Position Monitor) shows an instability problem over time. In this paper, we will present the status of studies on this issue. Several methods are utilized to calibrate the HOMBPMs. These methods include DLR (Direct Linear Regression), and SVD (Singular Value Decomposition). We found that SVD generally is more suitable for HOMBPM calibration. We focus on the HOMBPMs at 1.3 GHz cavities. Techniques developed here are applicable to 3.9 GHz modules. The work will pave the way for HOMBPMs of the E-XFEL (European X-Ray Free Electron Laser).
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TUPF12	First Tests of a Micro-TCA-Based Downconverter Electronic for 5GHz Higher Order Modes in Third Harmonic Accelerating Cavities at the XFEL	HOM, higher-order-mode, monitoring, electronics	337
	T. Wamsat, N. Baboi DESY, Hamburg, Germany
	Beam excited higher order modes (HOM) in 3.9GHz accelerating cavities at the European XFEL are planned to be used for beam position monitoring. The specifications of the monitors have been defined during an extensive study on the 3.9GHz module at FLASH. Selected HOMs for precision measurement are located around 5440MHz and 9040MHz. An electronics developed by FNAL has been recently installed at FLASH* and provides a basis for the XFEL electronics. The paper will present the design and first test of the hardware for the μTCA (Micro Telecommunications Computing Architecture) standard used for the XFEL. The hardware consists of three different Rear Transition Modules (RTM), two four channel downconverter RTMs (5GHz and 9GHz) and a third RTM with two phase locked loop synthesizers on board for LO generation. Presently the 5GHz and the PLL RTMs are under construction. The first measurements with these cards will be presented. N.Baboi, N.Eddy at al., this conference *N.Baboi, N.Eddy at al., this conference
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TUPF16	FRIB Beam Position Monitor Pick-Up Design	linac, pick-up, cryogenics, ion	355
	O. Yair, J.L. Crisp, G. Kiupel, S.M. Lidia, R.C. Webber FRIB, East Lansing, Michigan, USA
	Due to the different beam diameters and the inclusion of superconducting cavities, different Beam Position Monitor (BPM) types with welded buttons are to be used in the Facility for Rare Isotope Beams (FRIB). The varying BPM sizes include the following apertures: 40 mm, 50 mm, 100 mm, and 150 mm. The 40 mm BPMs include both warm and cold types where the cold BPMs are located in cryomodules next to SRF cavities. Steel-jacketed SiO2 coaxial cables with sealed SMA connectors have been selected as signal cables in the cryomodule insulating vacuum. These will connect to the BPM assembly at roughly 4 K temperature at one end and to the feedthrough flange in the vacuum vessel wall at 300 K at the other end. The 40 mm and 50 mm BPMs will include 20 mm custom-made buttons. The 100 mm and 150 mm aperture BPM buttons will be larger, anywhere from 30 mm to 40 mm. This paper will specify the mechanical and electrical design challenges and the resolutions associated with FRIB operations in the following areas: varying BPM conditions, changes in apertures, and variants in button sizes.
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WEIXB1	LCLS Beam Diagnostics	electron, undulator, diagnostics, laser	475
	H. Loos SLAC, Menlo Park, California, USA
	Funding: Work supported by DOE contract DE-AC03-76SF00515 An extensive set of beam diagnostics has been one of the factors in the successful commissioning and operation of the Linac Coherent Light Source (LCLS) x-ray FEL over the last seven years. The originally developed and installed diagnostics were geared towards measuring the electron beam parameters of the LCLS design specifications. Since then, a number of improved and new diagnostics have been implemented to accommodate a much wider range of beam parameters and to overcome the challenges of diagnostics for a high brightness electron beam. Plans for the diagnostics of the LCLS-II project with its high repetition rate and high beam power and ongoing developments will also be discussed.
	Slides WEIXB1 [4.408 MB]
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WEIYB1	Direct (Under)Sampling vs Analog Downconversion for BPM Electronics	electronics, pick-up, detector, timing	486
	M. Wendt CERN, Geneva, Switzerland
	Digital signal processing by means of undersampling the analog signal has become a popular method for acquiring beam position monitor signals. This presentation discusses the technique and its principle limitations, presents today’s technical limits (e.g. in terms of performance of available ADCs), and provides an outlook for the future. It will also try to compare the technique with more tradition analog downmixing and signal processing methods.
	Slides WEIYB1 [3.957 MB]
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WEPF15	Status of the Standard Diagnostic Systems of the European XFEL	diagnostics, electronics, undulator, gun	569
	D. Nölle DESY, Hamburg, Germany
	The European XFEL, an X-ray free-electron-laser user facility based on a 17.5 GeV superconducting LINAC, is currently under construction close to the DESY site at Hamburg. DESY is in charge of the construction of the accelerator. This contribution will report the status of the standard diagnostic systems of this facility. The design phase has finished for all main systems; most of the components are in production or are already produced. This paper will show details of the main systems, their installation issues and will report on the further time schedule. Furthermore, the experience from the commissioning of the RF gun with beam will be reported.
	Poster WEPF15 [5.427 MB]
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WEPD03	Conceptual Design of Elliptical Cavity Beam Position Monitors for Heavy Ion Storage Rings	storage-ring, pick-up, ion, impedance	634
	M.S. Sanjari, X. Chen, P. Hülsmann, Yu.A. Litvinov, F. Nolden, M. Steck, T. Stöhlker GSI, Darmstadt, Germany J. Piotrowski AGH University of Science and Technology, Kraków, Poland
	Funding: M.S.S. acknowledges partial support by the Alliance Program of the Helmholtz Association (HA216/EMMI). X.C. acknowledges funding by the European Commission (PITN-GA-2011-289485). Over 50 years in the history of accelerator physics, RF cavities have been used as beam position and intensity monitors. Their structure has been extensively discussed across numerous papers reporting their successful operation. The application of RF cavities as pick-ups has recently been extended to include radioactive ion beam (RIB) facilities and heavy ion storage rings. These pick-ups allow for very sensitive, accurate, and quick characterisation of ion beams and turn out to be indispensable tools in nuclear as well as atomic physics experiments. A notable example is the resonant pick-up in the ESR at GSI Darmstadt () where single ion detection was achieved for lifetime measurements of radioactive nuclides (). A similar cavity pick-up was installed in CSRe in IMP Lanzhou (*). In this work, we describe a novel conceptual approach that utilizes RF cavities with an elliptical geometry. While requiring a high precision determination of the position and intensity of particle beams, it has to cope with design restriction at heavy-ion storage rings such as large beam pipe apertures. The latter become inevitable at facilities aiming at storing large-emittance beams as, e.g., planned in the future Collector Ring (CR) of the FAIR project at GSI Darmstadt. Simulation results are accompanied by results achieved from bench-top measurements on model cavities. F. Nolden et. al., NIM A, v 659 No 1 pp 69–77 (2011) P. Kienle, F. Bosch et. al., Phys. Lett. B, v 726, 4–5, pp 638–645 (2013) * J. X. Wu et. al., NIM B, v 317, pp 623–628 (2013)
	Poster WEPD03 [1.967 MB]
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WEPD12	Low-Q Cavity BPM Electronics for E-XFEL, FLASH-II and SwissFEL	electronics, undulator, pick-up, controls	670
	M. Stadler, R. Baldinger, R. Ditter, B. Keil, F. Marcellini, G. Marinkovic, M. Roggli, M. Rohrer PSI, Villigen PSI, Switzerland D. Lipka, D. Nölle, S. Vilcins DESY, Hamburg, Germany
	PSI has developed BPM electronics for low-Q cavity BPMs that will be used in the E-XFEL and FLASH-II undulators, as well as in SwissFEL injector, linac and transfer lines. After beam tests at the SwissFEL test injector and FLASH, a pre-series of the electronics has been produced, tested and commissioned at FLASH-II [1]. The design, system features, signal processing techniques, lab-based test and calibration system as well as latest measurement results are reported.
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WEPD13	Development of the SwissFEL Undulator BPM System	pick-up, undulator, electronics, linac	675
	M. Stadler, R. Baldinger, R. Ditter, B. Keil, F. Marcellini, G. Marinkovic, M. Roggli, M. Rohrer PSI, Villigen PSI, Switzerland
	For SwissFEL, two types of cavity BPMs are used. In the linac, injector and transfer lines, low-Q dual-resonator cavity BPMs with a loaded Q (QL) of ~40 and 3.3GHz mode frequency allow easy separation of the two adjacent bunches with 28ns bunch spacing. For the undulators that receive only single bunches from a beam distribution kicker with 100Hz repetition rate, dual-resonator BPM pickups with higher QL are used. The baseline version for the undulator BPMs is a stainless steel pickup with QL=200 and 3.3GHz frequency. In addition, an alternative version with copper resonators, QL=1000 and 4.8GHz frequency has been investigated. For both pickups, prototypes were built and tested. The status of pickup and electronics development as well as the latest prototype test results are reported.
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Paper

Title

Other Keywords

Page

MOPF27

Simulation and First Results of the ELBE SRF Gun II

gun, laser, SRF, simulation

106

P.N. Lu, A. Arnold, U. Lehnert, P. Murcek, J. Teichert, H. Vennekate, R. Xiang
HZDR, Dresden, Germany

In Rossendorf, a 3 and one half cell cavity SRF photo injector has been installed, which promises to accelerate the electron beam to 9 MeV in 0.5 meter. The gun is expected to operate both in the 13 MHz mode with a bunch charge of 77 pC, or in the 500 kHz mode, with a 1 nC charge. The simulation presented in this contribution includes particle tracking in the new cavity itself with the ASTRA code, and in the bunch transport line in the ELBE beam lines with the elegant code. The measured profile and time structure of the UV laser on the cathode are utilized to specify the electron bunch parameters. Then a single bunch of electrons is tracked in the cavity field that was calculated by Superfish, with space charge effects considered. From the exit of the cavity, the electron bunch has a relatively high energy so we ignore the space charge effect there and apply elegant to track the particles through the magnet elements and accelerator modules. The main purpose of this simulation is to find the optimized parameters for different beam transport tasks. As a first experimental result of the photoinjector, energy and phase space measurement will be also presented in the paper. Both the slit mask and the quadrupole scan methods are applied to measure the beam emittance. An obvious progression will be to compare the results from this gun with those from the ELBE SRF gun I.

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MOPD05

Dual Transverse and Longitudinal Streak Camera Imaging at ELSA

damping, diagnostics, synchrotron, electron

144

M.T. Switka, F. Frommberger, P. Hänisch, W. Hillert, M. Schedler
ELSA, Bonn, Germany

Funding: Funded by the German Research Foundation (DFG) within Colaborative Research Center (SFB/TRR) 16
The electron pulse stretcher ring ELSA located at Bonn University provides 0.5 – 3.5 GeV polarized and non-polarized electron beams for external experimental stations. A streak camera system has been installed to capture time resolved images of beam dynamics ranging from nanoseconds to several milliseconds. Particular attention was drawn to the capability of simultaneous imaging of both transverse beam dimensions, hence providing information of all spatial dimensions in one synchroscan or slow sweep measurement. Incoherent and coherent beam instabilities, especially at high stored beam currents, are subject of analysis due to the planned intensity upgrade towards 200 mA for standard operation. The current resolution performance of the imaging system and machine relevant measurements are presented.

Poster MOPD05 [6.133 MB]

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MOPD19

Bunch Arrival Time Monitor for PAL-XFEL

timing, pick-up, LLRF, electronics

191

J.H. Hong, J.H. Han, H.-S. Kang, C. Kim, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

The X-ray Free Electron Laser project in Pohang Accelerator Laboratory (PAL-XFEL) requires high stability of bunch arrival time, and measurement resolution better than a few femtoseconds. The pickups of the electron Bunch Arrival time Monitor (BAM) for PAL-XFEL have been developed and simulated. The BAM pickups are based on an S-band monopole cavity with two coupling loops. The prototype BAM has been fabricated and installed downstream of the accelerating column at the Injector Test Facility (ITF) for PAL-XFEL. In this paper we will present the recent measurement results on the beam test of the BAM as well as a proposed strategy for developing the BAM for PAL-XFEL.

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TUCYB2

Pulsed Green Laser Wire System for Effective Inverse Compton Scattering

laser, electron, emittance, experiment

254

A.A. Rawankar, N. Terunuma, J. Urakawa
Sokendai, Ibaraki, Japan
T. Akagi, A.S. Aryshev, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
D. Jehanno
LAL, Orsay, France
K. Sakaue
Waseda University, Tokyo, Japan

Funding: This work has been supported by the Quantum Beam Technology Program of the Japanese Ministry of Education, Culture, Sports, Science,and Technology(MEXT).
Laser-Compton scattering has become an important technique for beam diagnostics of the latest accelerators. In order to develop technologies for low emittance beams, an Accelerator Test facility (ATF) was built at KEK. It consists of an electron linac, a damping ring in which beam emittance is reduced, and an extraction line. For emittance measurement we are developing a new type of beam profile monitor which works on the principle of inverse Compton scattering between electron and laser light. In order to achieve effective collision of photon and electron, a pulsed and very thin size laser is required. Laser wire is one technique of measuring a small beam size. With green lasers, which are converted to second harmonics from IR pulsed laser, minimum beam waist is half of the beam waist obtained using infrared (IR) laser oscillator. Therefore, it is possible to obtain beam waist less than 5 μm using green laser pulse, which is required for effective photon-electron collision. First, pulsed IR seed laser is amplified with 1.5 meter long PCF based amplifier system. This pulsed IR laser is converted to second harmonics with a non-linear crystal. Pulsed green laser is injected inside four mirror optical cavity to obtain very small beam waist at interaction point (IP). Using a pulsed compact laser wire, we can measure 10 um electron beams in vertical directions. We report the development of the pulsed green laser and parameters of compact four mirror optical cavity for effective inverse Compton scattering.

Slides TUCYB2 [2.632 MB]

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TUPF05

Production Process for the European XFEL Re-Entrant Cavity BPM

cryomodule, quadrupole, vacuum, controls

307

C.S. Simon, P. Carbonnier, P. Contrepois, F. Éozénou, Y. Gasser, O. Napoly, J. Novo, C. Servouin
CEA/DSM/IRFU, France
C. Boulch, Y. Gasser
CEA/IRFU, Gif-sur-Yvette, France
P. Daniel-Thomas, F. Gouit
CEA, Gif-sur-Yvette, France
J. Kruse, D. Nölle, M. Schalwat, S. Vilcins
DESY, Hamburg, Germany
N. Rouvière
IPN, Orsay, France

As In-Kind contributor to the E-XFEL project, CEA is committed to the procurement of around one third (31) cold beam position monitors (BPM) of the re-entrant RF cavities type and to the assembly on the Saclay site of the 101 cryomodules of the superconducting linac. Each cryomodule is equipped with a beam position monitor connected to a quadrupole at the high-energy end of the cavity string. The industrial process of those BPMs, used in an ultra-clean environment at cryogenic temperature, includes several steps and involves a quality control in collaboration with industrial partners. This paper describes the different steps of the re-entrant cavity BPM fabrication process: machining, copper coating, thermal treatment, EB welding, cleaning and mounting in clean room on the quadrupole. Problems encountered and the lessons learnt will be also reported.

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TUPF06

Commissioning of the Electronics for HOM-based Beam Diagnostics at the 3.9 GHz Accelerating Module at FLASH

HOM, electronics, alignment, dipole

311

N. Baboi, O. Hensler, L. Shi, T. Wamsat
DESY, Hamburg, Germany
N. Eddy, B.J. Fellenz
Fermilab, Batavia, Illinois, USA
P. Zhang
CERN, Geneva, Switzerland

Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
Transverse Higher Order Modes (HOM) excited by electron beams in the 3.9 GHz accelerating cavities at FLASH may damage the beam quality. They can be reduced by extracting their energy through special couplers and by aligning the beam in the cavity. Electronics has been designed at FNAL for monitoring some of the potentially most damaging HOMs. This may be used for beam centering and therefore reducing the HOM effects. Moreover, the signals can be potentially calibrated into beam offset, so that they could be used as beam position monitors (HOM-BPM). The specifications of the monitors have been defined during an extensive study on the 4-cavity accelerating module installed at FLASH. Signals around 5.44 GHz have been chosen for higher precision measurements. However these signals propagate into the entire 1.2 m long module. Therefore in addition modes at about 9 GHz were selected for localized measurements in each cavity. The electronics has been recently installed at FLASH. The commissioning results will be presented in this paper. Instabilities previously observed in a test electronics as well as the HOM-BPMs in 1.3 GHz cavities will also be investigated*. This electronics will also serve as a prototype for the electronics developed for the 3.9 GHz cavities at the European XFEL**.
*L. Shi et al., this Conference
**T. Wamsat et al., this Conference

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TUPF07

FLASH Undulator BPM Commissioning and Beam Characterization Results

electronics, undulator, pick-up, controls

315

D. Lipka, N. Baboi, D. Nölle, G. Petrosyan, S. Vilcins
DESY, Hamburg, Germany
R. Baldinger, R. Ditter, B. Keil, W. Koprek, R. Kramert, G. Marinkovic, M. Roggli, M. Stadler
PSI, Villigen PSI, Switzerland

Recently, the commissioning of FLASH2 has started, a new soft X-ray FEL undulator line at the DESY FLASH facility. In the FLASH2 undulator intersections, the beam positions are measured by 17 cavity beam position monitor (CBPM) pick-ups and electronics* developed for the European XFEL (E-XFEL). In addition four CBPMs are available at FLASH1 for test and development. The new CBPM system enables an unprecedented position and charge resolution at FLASH, thus allowing further analysis and optimization of the FLASH beam quality and overall accelerator performance. Results of first beam measurements as well as correlations with other FLASH diagnostics systems are reported.
* M. Stadler et al., “Low-Q Cavity BPM Electronics for E-XFEL, FLASH-2 and SwissFEL”, this conference.

Poster TUPF07 [1.112 MB]

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TUPF10

Stability Study of the Higher Order Mode Beam Position Monitors at the Accelerating Cavities at FLASH

dipole, HOM, electronics, polarization

327

L. Shi, N. Baboi
DESY, Hamburg, Germany
R.M. Jones
UMAN, Manchester, United Kingdom

When electron beams traverse an accelerating structure, higher order modes (HOMs) are excited. They can be used for beam diagnostic purposes. Both 1.3 GHz and 3.9 GHz superconducting accelerating cavities at FLASH linac, DESY, are equipped with electronics for beam position monitoring, which are based on HOM signals from special couplers. These monitors provide the beam position without additional vacuum components and at low cost. Moreover, they can be used to align the beam in the cavities to reduce the HOM effects on the beam. However, the HOMBPM (Higher Order Mode based Beam Position Monitor) shows an instability problem over time. In this paper, we will present the status of studies on this issue. Several methods are utilized to calibrate the HOMBPMs. These methods include DLR (Direct Linear Regression), and SVD (Singular Value Decomposition). We found that SVD generally is more suitable for HOMBPM calibration. We focus on the HOMBPMs at 1.3 GHz cavities. Techniques developed here are applicable to 3.9 GHz modules. The work will pave the way for HOMBPMs of the E-XFEL (European X-Ray Free Electron Laser).

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TUPF12

First Tests of a Micro-TCA-Based Downconverter Electronic for 5GHz Higher Order Modes in Third Harmonic Accelerating Cavities at the XFEL

HOM, higher-order-mode, monitoring, electronics

337

T. Wamsat, N. Baboi
DESY, Hamburg, Germany

Beam excited higher order modes (HOM) in 3.9GHz accelerating cavities at the European XFEL are planned to be used for beam position monitoring. The specifications of the monitors have been defined during an extensive study on the 3.9GHz module at FLASH. Selected HOMs for precision measurement are located around 5440MHz and 9040MHz. An electronics developed by FNAL has been recently installed at FLASH* and provides a basis for the XFEL electronics. The paper will present the design and first test of the hardware for the μTCA (Micro Telecommunications Computing Architecture) standard used for the XFEL. The hardware consists of three different Rear Transition Modules (RTM), two four channel downconverter RTMs (5GHz and 9GHz) and a third RTM with two phase locked loop synthesizers on board for LO generation. Presently the 5GHz and the PLL RTMs are under construction. The first measurements with these cards will be presented. *N.Baboi, N.Eddy at al., this conference
**N.Baboi, N.Eddy at al., this conference

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TUPF16

FRIB Beam Position Monitor Pick-Up Design

linac, pick-up, cryogenics, ion

355

O. Yair, J.L. Crisp, G. Kiupel, S.M. Lidia, R.C. Webber
FRIB, East Lansing, Michigan, USA

Due to the different beam diameters and the inclusion of superconducting cavities, different Beam Position Monitor (BPM) types with welded buttons are to be used in the Facility for Rare Isotope Beams (FRIB). The varying BPM sizes include the following apertures: 40 mm, 50 mm, 100 mm, and 150 mm. The 40 mm BPMs include both warm and cold types where the cold BPMs are located in cryomodules next to SRF cavities. Steel-jacketed SiO2 coaxial cables with sealed SMA connectors have been selected as signal cables in the cryomodule insulating vacuum. These will connect to the BPM assembly at roughly 4 K temperature at one end and to the feedthrough flange in the vacuum vessel wall at 300 K at the other end. The 40 mm and 50 mm BPMs will include 20 mm custom-made buttons. The 100 mm and 150 mm aperture BPM buttons will be larger, anywhere from 30 mm to 40 mm. This paper will specify the mechanical and electrical design challenges and the resolutions associated with FRIB operations in the following areas: varying BPM conditions, changes in apertures, and variants in button sizes.

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WEIXB1

LCLS Beam Diagnostics

electron, undulator, diagnostics, laser

475

H. Loos
SLAC, Menlo Park, California, USA

Funding: Work supported by DOE contract DE-AC03-76SF00515
An extensive set of beam diagnostics has been one of the factors in the successful commissioning and operation of the Linac Coherent Light Source (LCLS) x-ray FEL over the last seven years. The originally developed and installed diagnostics were geared towards measuring the electron beam parameters of the LCLS design specifications. Since then, a number of improved and new diagnostics have been implemented to accommodate a much wider range of beam parameters and to overcome the challenges of diagnostics for a high brightness electron beam. Plans for the diagnostics of the LCLS-II project with its high repetition rate and high beam power and ongoing developments will also be discussed.

Slides WEIXB1 [4.408 MB]

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WEIYB1

Direct (Under)Sampling vs Analog Downconversion for BPM Electronics

electronics, pick-up, detector, timing

486

M. Wendt
CERN, Geneva, Switzerland

Digital signal processing by means of undersampling the analog signal has become a popular method for acquiring beam position monitor signals. This presentation discusses the technique and its principle limitations, presents today’s technical limits (e.g. in terms of performance of available ADCs), and provides an outlook for the future. It will also try to compare the technique with more tradition analog downmixing and signal processing methods.

Slides WEIYB1 [3.957 MB]

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WEPF15

Status of the Standard Diagnostic Systems of the European XFEL

diagnostics, electronics, undulator, gun

569

D. Nölle
DESY, Hamburg, Germany

The European XFEL, an X-ray free-electron-laser user facility based on a 17.5 GeV superconducting LINAC, is currently under construction close to the DESY site at Hamburg. DESY is in charge of the construction of the accelerator. This contribution will report the status of the standard diagnostic systems of this facility. The design phase has finished for all main systems; most of the components are in production or are already produced. This paper will show details of the main systems, their installation issues and will report on the further time schedule. Furthermore, the experience from the commissioning of the RF gun with beam will be reported.

Poster WEPF15 [5.427 MB]

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WEPD03

Conceptual Design of Elliptical Cavity Beam Position Monitors for Heavy Ion Storage Rings

storage-ring, pick-up, ion, impedance

634

M.S. Sanjari, X. Chen, P. Hülsmann, Yu.A. Litvinov, F. Nolden, M. Steck, T. Stöhlker
GSI, Darmstadt, Germany
J. Piotrowski
AGH University of Science and Technology, Kraków, Poland

Funding: M.S.S. acknowledges partial support by the Alliance Program of the Helmholtz Association (HA216/EMMI). X.C. acknowledges funding by the European Commission (PITN-GA-2011-289485).
Over 50 years in the history of accelerator physics, RF cavities have been used as beam position and intensity monitors. Their structure has been extensively discussed across numerous papers reporting their successful operation. The application of RF cavities as pick-ups has recently been extended to include radioactive ion beam (RIB) facilities and heavy ion storage rings. These pick-ups allow for very sensitive, accurate, and quick characterisation of ion beams and turn out to be indispensable tools in nuclear as well as atomic physics experiments. A notable example is the resonant pick-up in the ESR at GSI Darmstadt (*) where single ion detection was achieved for lifetime measurements of radioactive nuclides (**). A similar cavity pick-up was installed in CSRe in IMP Lanzhou (***). In this work, we describe a novel conceptual approach that utilizes RF cavities with an elliptical geometry. While requiring a high precision determination of the position and intensity of particle beams, it has to cope with design restriction at heavy-ion storage rings such as large beam pipe apertures. The latter become inevitable at facilities aiming at storing large-emittance beams as, e.g., planned in the future Collector Ring (CR) of the FAIR project at GSI Darmstadt. Simulation results are accompanied by results achieved from bench-top measurements on model cavities.
* F. Nolden et. al., NIM A, v 659 No 1 pp 69–77 (2011)
** P. Kienle, F. Bosch et. al., Phys. Lett. B, v 726, 4–5, pp 638–645 (2013)
*** J. X. Wu et. al., NIM B, v 317, pp 623–628 (2013)

Poster WEPD03 [1.967 MB]

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WEPD12

Low-Q Cavity BPM Electronics for E-XFEL, FLASH-II and SwissFEL

electronics, undulator, pick-up, controls

670

M. Stadler, R. Baldinger, R. Ditter, B. Keil, F. Marcellini, G. Marinkovic, M. Roggli, M. Rohrer
PSI, Villigen PSI, Switzerland
D. Lipka, D. Nölle, S. Vilcins
DESY, Hamburg, Germany

PSI has developed BPM electronics for low-Q cavity BPMs that will be used in the E-XFEL and FLASH-II undulators, as well as in SwissFEL injector, linac and transfer lines. After beam tests at the SwissFEL test injector and FLASH, a pre-series of the electronics has been produced, tested and commissioned at FLASH-II [1]. The design, system features, signal processing techniques, lab-based test and calibration system as well as latest measurement results are reported.

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WEPD13

Development of the SwissFEL Undulator BPM System

pick-up, undulator, electronics, linac

675

M. Stadler, R. Baldinger, R. Ditter, B. Keil, F. Marcellini, G. Marinkovic, M. Roggli, M. Rohrer
PSI, Villigen PSI, Switzerland

For SwissFEL, two types of cavity BPMs are used. In the linac, injector and transfer lines, low-Q dual-resonator cavity BPMs with a loaded Q (QL) of ~40 and 3.3GHz mode frequency allow easy separation of the two adjacent bunches with 28ns bunch spacing. For the undulators that receive only single bunches from a beam distribution kicker with 100Hz repetition rate, dual-resonator BPM pickups with higher QL are used. The baseline version for the undulator BPMs is a stainless steel pickup with QL=200 and 3.3GHz frequency. In addition, an alternative version with copper resonators, QL=1000 and 4.8GHz frequency has been investigated. For both pickups, prototypes were built and tested. The status of pickup and electronics development as well as the latest prototype test results are reported.

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