02 Synchrotron Light Sources and FELs

T12 Beam Injection/Extraction and Transport

Paper Title Page
TUPEC005 Development and Commissioning of the CUTE-FEL Injector 1716
 
  • S. Lal, B. Biswas, S. Chouksey, S.K. Gupta, U. Kale, M. Khursheed, A. Kumar, V. Kumar, P. Nerpagar, K.K. Pant, A. Patel, V. Prasad, A.K. Sarkar
    RRCAT, Indore (M.P.)
  • S. Krishnagopal
    BARC, Mumbai
 
 

The injector system for the Compact Ultrafast Terahertz Free Electron Laser (CUTE-FEL) consists of a 1 ns, 90 kV pulsed thermionic electron gun, a 476 MHz sub-harmonic prebuncher, and a standing wave, S-band Plane Wave Transformer (PWT) linac capable of accelerating beam to 10 MeV. Beam from this injector will be transported to the entrance of the undulator through a beam transport line, with the required diagnostic elements, that has been designed, developed and commissioned. The control system and the low and high power microwave lines have also been commissioned. In this paper, we discuss salient features of the injector system and results from recent commissioning trials of the injector.

 
TUPEC025 Artificial Intelligence Systems for Electron Beam Parameters Optimization at the Australian Synchrotron LINAC 1770
 
  • E. Meier, G. LeBlanc
    ASCo, Clayton, Victoria
  • S. Biedron
    ELETTRA, Basovizza
  • M.J. Morgan
    Monash University, Faculty of Science, Victoria
 
 

We report the development of an artificial intelligent system for the optimisation of electron beam parameters at the Australian Synchrotron Linac. The system is based on state of the art developments in Artificial Intelligence techniques for video games and is adapted here to beam parameters optimisation problems. It consists of a genetically evolved neural network that mimics an operator's decisions to perform an optimisation task when no prior knowledge other than constraints on the actuators is available. The system's decisions are based on the actuators positions, the past performance of close points in the search space and the probability of reaching a better performance in the local region of the search space.

 
TUPEC026 Determination of the Magnetic Characteristics in the Injection Septum for the Metrology Light Source 1773
 
  • O. Dressler, M.V. Hartrott
    Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
  • N. Hauge
    Danfysik A/S, Jyllinge
 
 

The pre-accelerator microtron supplies an electron beam at 105 MeV for the Metrology Light Source (MLS) of the Physikalisch-Technische Bundesanstalt (PTB) in Berlin. The beam is delivered via the transfer line to the injection septum and then into the storage ring. This septum magnet has its stainless steel vacuum beam pipe placed inside a laminated silicon iron magnet core. Hence, the pulsed magnetic field (half sine) used for the beam deflection must propagate through the thin metallic beam pipe. During the commissioning of the injection process, it became apparent that the calculated nominal pulse current for this energy and geometry had to be increased by 30 % to achieve proper beam transfer and accumulation. Two problems were apparent. Firstly, the injected beam trajectory had to be set at an angle away from the main beam axis. Secondly, the beam transfer from the septum entrance to exit was disturbed. As a first measure, the septum current pulse length was extended from 35 to 107 μs. Further on, the septum magnet was insulated from the transfer line beam pipe by a ceramic brake. This paper reports on measurements of pulsed magnetic fields inside the septum magnet.


* Commissioning and Operation of the Metrology Light Source, J. Feikes et al., BESSY, Berlin, Germany; R. Klein, G. Ulm, Physikalisch-Technische Bundesanstalt, Berlin, Germany; EPAC08, Genoa, Italy.

 
TUPEC027 Microbunching and RF Compression 1776
 
  • M. Migliorati
    Rome University La Sapienza, Roma
  • M. Ferrario, C. Vaccarezza
    INFN/LNF, Frascati (Roma)
  • C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
  • M. Venturini
    LBNL, Berkeley, California
 
 

Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.

 
TUPEC029 Comparison between Hexaboride Materials for Thermionic Cathode RF Gun 1782
 
  • M. A. Bakr, Y.W. Choi, T. Kii, R. Kinjo, K. Masuda, H. Ohgaki, T. Sonobe, M. Takasaki, S. Ueda, K. Yoshida
    Kyoto IAE, Kyoto
  • H. Zen
    UVSOR, Okazaki
 
 

RF gun has been chosen as injector for Kyoto University free electron laser because it can potentially produce an electron beam with high energy, small emittance, moreover inexpensive and compact configuration in comparison with other injectors. As for the RF gun cathode, thermionic cathode is simpler, easier to treat and reliable than photocathode. On the other hand, backbombardment electrons make cathode surface temperature and current density increase within the macropulse, as a result, beam energy and macropulse duration decrease, which means, it is difficult to generate stable FEL. The heating property of cathode not only depends on physical properties of the cathode material such as work function, but also backbombardment electrons energy. We investigated the heating property of six hexaboride materials against the backbombarding electrons by numerical calculation of the range and stopping power. In this investigation, the emission property of the cathode was also taken into account, since high electron emission is required for generation of high brightness electron beam. The results will be discussed.

 
TUPEC030 Conceptual Design of Injection System for Hefei Light Source (HLS) Upgrade Project 1785
 
  • G. Feng, W. Fan, W.W. Gao, W. Li, L. Wang, S.C. Zhang
    USTC/NSRL, Hefei, Anhui
 
 

In order to obtain more straight sections for insertion devices and higher brilliance synchrotron radiation, an upgrade project of Hefei Light source (HLS) is undergoing. A new injection system has been designed to improve injection efficiency and keep the machine running stably. Four kickers will be used to generate a local injection bump. Effects of injection system to injecting beam and stored beam have been simulated considering errors. Finally, ELEGANT code was used to simulate the injection process with new designed bump system. The simulation results show that the injection efficiency would be higher than 99% and perturbation on stored beam would be small enough, which are benefit to full energy injection and top-up operation of HLS in the future.

 
TUPEC031 The Operation of Injection System in the SSRF 1788
 
  • M. Gu, Z.H. Chen, B. Liu, L. Ouyang, R. Wang, Y. Wu, Q. Yuan
    SINAP, Shanghai
 
 

The injection system composed of four kickers and two septa in the SSRF have been built and operated. The commissioning shows that fine injecting efficiency and smaller disturbance are carried out. The septum magnets are eddy current designs with a sheet of magnetic screening material around the stored electron beam to reduce the leakage field. The beam tube with RF finger flanges at each end is added to keep the continuity of impedance for the circulating beam. The pulser excite the septum with 60μsecond waveform of half sine-wave and 8kA peak current. Four identical kicker magnets provide the symmetric bump in 10 meter long straight sections. The excitation waveform is a 3.8μsecond half sine pulse up to 7 kA peak. The emphasis was on achieving the best possible tracking in time of the magnet field waveforms so that the residual closed orbit disturbance is minimized for top-up injection. The performance of the injection system with these pulsed magnets are described.

 
TUPEC032 Injection Efficiency Monitoring with Libera Brilliance Single Pass 1790
 
  • M. Znidarcic
    I-Tech, Solkan
  • K.B. Scheidt
    ESRF, Grenoble
 
 

Initially, the Libera Brilliance Single Pass was intended for beam position monitoring at injector system for the FEL machines, this was afterwards followed by the idea of using it on transfer lines on the 3rd generation light sources. The device can be used on pickup buttons and on striplines. The measurement principles and results of Libera Brilliance Single Pass at ESRF, as beam-charge monitor and injection-efficiency monitor, are presented.

 
TUPEC033 Effectiveness of a Shielding Cabinet on the Storage-Ring Septum Magnet of Taiwan Light Source 1793
 
  • J.C. Huang, C.-H. Chang, C.-S. Hwang, C.Y. Kuo, F.-Y. Lin, C.-S. Yang
    NSRRC, Hsinchu
 
 

Pulsed magnet system of Taiwan Photon source(TPS) requires a very low stray field to avoid parasitic magnetic field into the stored beam. The stray field from storage ring(SR) injection septum is required to be less than 0.2 Gauss. The most common method to protect parasitic magnetic field is to use high permeability and conductivity material, such as a Mu-metal. A 1.2 ms half-sine wave pulse of up to 8280A current peak are supply to a septum and would result in eddy current loss in magnet and conductor current diffusion during the rapid charging on magnet. Moreover, competition between eddy current loss and magnetic permeability would lead to a complex phenomena inside the mumetal shielding cabinet and shielding performance. In this study, the magnetic shielding performance of a shielding cabinet was examined in different shielding cabinet geometry and thickness. The results were calculated in Opera software and show that there is a significant suppression of SR septum stray field when round shielding cabinet is in use.

 
TUPEC034 Dual One-turn Coils for TLS Extraction Kicker Magnet 1796
 
  • K.L. Tsai, C.-T. Chen, Y.-S. Cheng, C.-S. Fann, K.T. Hsu, S.Y. Hsu, K.H. Hu, K.-K. Lin, C.Y. Wu
    NSRRC, Hsinchu
  • Y.-C. Liu
    National Tsing-Hua University, Hsinchu
 
 

The test results of a dual one-turn coils configuration for Taiwan Light Source (TLS) booster extraction kicker is presented in this report. The achieved capability of the test unit demonstrates that the rise-time of the kicker current pulse has been improved for beam extraction optimization. This improved performance is mainly accomplished by reducing the load inductance effectively with a dual one-turn coils configuration. The measured result of rise-time variation versus the corresponding load inductance change is briefly discussed.

 
TUPEC036 Design of Post Linac Beam Transport for the UK New Light Source Project 1802
 
  • D. Angal-Kalinin, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • D. Angal-Kalinin, F. Jackson, S.P. Jamison, J.K. Jones, B.D. Muratori, N. Thompson
    Cockcroft Institute, Warrington, Cheshire
  • R. Bartolini, I.P.S. Martin
    JAI, Oxford
 
 

The design of free electron laser (FEL) driver needs careful beam transport design to pass very short bunches through the switchyard/spreader to switch the beam to different FEL lines. The spreader design which allows flexibility in operation has been adapted following the LBNL design*. In order to measure the slice properties of the bunches two beam diagnostics lines are proposed, a straight one for beam commissioning purposes and a branch of the spreader similar to the FEL lines to measure the adverse effects that may arise due to passing the short bunches through the kicker and septum magnets. As a part of machine protection, post linac collimation system collimates the halo particles in transverse and energy planes. The design of the collimation, beam spreader and beam diagnostics lines is discussed.


* Zholents A.A. et al, CBP Tech Note 401, 2009

 
TUPEC037 Beam Dump and Collimation Design Studies for NLS: Thermal and Structural Behaviour 1805
 
  • J.-L. Fernandez-Hernando, D. Angal-Kalinin
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
 
 

The proposed UK New Light Source project will need beam dump to absorb a bunch charge of 200 pC with the repetition rates starting from 1 KHz initially up to 1 MHz in the upgrade. We are exploring an option of a solid dump with a graphite core to absorb the beam power up to 450 kW for the upgrade option as this is the most challenging design. Since the beam dump design will also affect the building layout the choice of its design should be made at an early stage. Based on the feasibility studies of a solid dump, a decision not to go for more complex water dump can be taken. The post linac collimation section should protect the undulators from irradiation due to beam halo particles. This paper shows results and conclusions from simulations of the impact of the NLS beam on different solid beam dump solutions and the effect of the beam halo on the collimators.

 
TUPEC038 Multipole Kickers for the ALS 1808
 
  • G.C. Pappas
    LBNL, Berkeley, California
 
 

For quadrupole or sextupole magnets, the field at the center is zero and will not disturb the stored beam, while the field away from the center increases in magnitude, giving a larger kick to the particles off axis. By pulsing such multipole magnets it is possible to improve the injection efficiency of the Advanced Light Source (ALS) in top off mode. The requirements for a multipole pole kicker injection scheme for ALS are to kick a 1.9 GeV beam by an angle of 10 mrad with a magnet of 1 meter length. Both quadrupole and sextupole magnets have been studied, as well as a dipole magnet with non-constant field magnitude across the center of the aperture. This paper describes the design and gives a comparison of each type of magnet as well as the modulators needed to drive them.

 
TUPEC039 Injected Beam Dynamics in SPEAR3 1811
 
  • W.J. Corbett, A.S. Fisher, X. Huang, J.A. Safranek, S. Westerman
    SLAC, Menlo Park, California
  • W.X. Cheng
    BNL, Upton, Long Island, New York
  • W.Y. Mok
    Life Imaging Technology, Palo Alto, California
 
 

As SPEAR3 moves closer to trickle-charge topup injection, the complex phase-space dynamics of the injected beam becomes increasingly important for capture efficiency and machine protection. In the horizontal plane the beam executes ~12mm betatron oscillations and begins to filament within 10's of turns. In the vertical plane the beam is more stable but a premium is placed on flat-orbit injection through the Lambertson septum and the correct optical match. Longitudinally, energy spread in the booster is converted to arrival-time dispersion by the strong R56 component in the transfer line. In this paper, we report on turn-by-turn imaging of the injected beam in both the transverse plane and in the longitudinal direction using a fast-gated ccd and streak camera, respectively.

 
TUPEC040 Optimal Twiss Parameters for Top Off Injection in a Synchrotron Light Source 1814
 
  • R.P. Fliller
    BNL, Upton, Long Island, New York
 
 

Injection into a ring requires that the injected beam be optimally matched to the storage ring lattice. For on axis injection this requires that the twiss functions of the transfer line match the twiss functions of the lattice. When injection off axis, as is done in light sources for top off injection, the goal is to use the minimum phase space area in the storage ring. A. Streun* has given an analytical method to compute the twiss functions for top off injection into the SLS where injection occurs at a beam waist. We have extended his theory to include cases where there is no beam waist. A simple analytical formula is not possible in this case, however we give an algorithm to compute the twiss parameters of the injected beam given the storage ring lattice. We also compute the twiss functions for a variety of cases for the NSLS-II storage ring.


* A. Streun. "SLS booster-to-ring transfer line optics for optimum injection effciency". Technical Note SLS-TME-TA-2002-0193. May 27, 2005.

 
TUPEC041 Beam Stacking in the NSLS-II Booster 1817
 
  • R.P. Fliller, R. Heese, S. Kowalski, J. Rose, T.V. Shaftan, G.M. Wang
    BNL, Upton, Long Island, New York
 
 

The National Synchrotron Light Source II (NSLS-II) is a state of the art 3 GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster synchrotron. The injection system needs to deliver 7.5 nC in 80 - 150 bunches to the storage ring every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source, though it should be achievable. To alleviate the charge requirement on the linac, we have designed a scheme to stack two bunch trains in the booster. In this paper we discuss this stacking scheme. The performance of the stacking scheme is studied in detail at injection and through a full booster ramp. We show the the ultimate performance of the stacking scheme is similar to a single bunch train in the booster if the linac emittance meets the requirements. Increasing the emittance of the linac beam degrades the performance, but still allows an overall increase of train charge vs. one bunch train.

 
TUPEC042 NSLS-II Transport Line Performance 1820
 
  • R.P. Fliller, W.R. Casey, R. Faussete, H. Fernandes, G. Ganetis, R. Heese, H.-C. Hseuh, P.K. Job, B.N. Kosciuk, R. Meier, D. Padrazo, I. Pinayev, J. Rose, T.V. Shaftan, O. Singh, J. Skaritka, C.J. Spataro, G.M. Wang
    BNL, Upton, Long Island, New York
 
 

The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster synchrotron and associated transport lines. The transport lines need to transport the beam from the linac to the booster and from the booster to the storage ring in a way that provide high injection efficiency. In this paper we discuss progress on specifying and prototyping the NSLS-II transfer lines including diagnostics, magnet specifications, and safety systems. Commissioning plans are also discussed.

 
TUPEC045 Requirements on the Pulsed Magnets for the Best Injector Performance 1823
 
  • T.V. Shaftan, A. Blednykh, Y. Kawashima, S. Krinsky, J. Rose, L.-H. Yu
    BNL, Upton, Long Island, New York
 
 

Booster extraction presents a number of problems that include strengths and waveforms of the pulsed magnets and design of the vacuum chamber. Instabilities in the booster extraction may compromise the extracted beam quality deteriorating value of high-performance injector design. Here we discuss requirements and tolerances for the extraction system components and methods of increasing its performance.