| Paper |
Title |
Page |
| MOPC058 |
ALICE (ERLP) Injector Design
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196 |
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- B. D. Muratori, Y. M. Saveliev
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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In this paper we look at how the ALICE (formerly ERLP) injector has been re-designed to meet more realistic criteria from the previous design. A key component of ALICE is the high brightness injector. The ALICE injector consists of a DC photocathode gun generating 80 pC electron bunches at 350 keV. These bunches are then matched into a booster cavity which accelerates them to an energy of 8.35 MeV. In order to do this, two solenoids and a single-cell buncher cavity are used, together with off-crest injection into the first booster cavity, where the beam is still far from being relativistic. The performance of the injector has been studied using the particle tracking code ASTRA.
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| MOPC059 |
BBU Limitations for ERLs
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199 |
| |
- E. Wooldridge, C. D. Beard, P. A. McIntosh, B. D. Muratori, S. L. Smith
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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The BBU threshold in ERLs is a limitation on the maximum beam current due to the interaction of the electron bunches and the Higher Order Modes (HOMs) contained within the RF cavities. Several factors are involved in determining the threshold current; from the cavity the Q, R/Q and degeneracy of the modes all play an important part. From the beam transport the values of the lattice functions α, β and μ have an effect. We will discuss the limits on these variables to provide a BBU current threshold greater than 100 mA for a multiple cavity machine and what will be required to provide higher currents. Also three different cavity profiles were investigated with the aim of reducing the BBU threshold. The TESLA 9-cell cavity was used as a baseline for comparison against possible 7-cell cavity designs, using the TESLA cell shape for their inner cells. The ends of the 7-cell cavities join to different sized beampipes, with radii of 39 mm and 54 mm, to allow the most of the HOMs to propagate to a broadband HOM absorber. Two different beampipe to cavity to transitions were investigated. The optimised 7-cell cavity will be shown to provide an increase in the BBU threshold.
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| MOPC062 |
Results from ALICE (ERLP) DC Photoinjector Gun Commissioning
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208 |
| |
- Y. M. Saveliev, D. J. Holder, B. D. Muratori, S. L. Smith
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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The Energy Recovery Linac Prototype (ERLP) DC photoinjector gun has been commissioned and the beam characteristics measured. The gun has demonstrated the nominal ERLP parameters of 350 keV electron energy, 80pC bunch charge and ~140 ps bunch length (at 10% level). The bunch parameters were measured at different bunch charges from 1 pC up to 80 pC. Special attention was given to measurements of the beam transverse emittance (using a movable slit), correlated and uncorrelated energy spread (using an energy spectrometer) and bunch length (using a transverse RF kicker) at each bunch charge. The effect of the 1.3 GHz RF buncher on the bunch length was also investigated. The experimental results are then compared with ASTRA simulations. Experimental results obtained from the investigation of several other issues including the beam characteristics in the presence of field emission from the cathode and in the presence of strong beam halo are also presented and discussed.
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| MOPC063 |
Characterisation of Electron Bunches from ALICE (ERLP) DC Photoinjector Gun at Two Different Laser Pulse Lengths
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211 |
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- Y. M. Saveliev, S. P. Jamison, L. B. Jones, B. D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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In high-voltage DC photoinjector guns, the laser pulse duration affects the electron bunch characteristics and therefore is an important subject for experimental investigation and in the optimisation of the operation of the gun. Initial experimental study of this effect has been conducted using the Energy Recovery Linac Prototype (ERLP) photoinjector. During the commissioning of its DC photoinjector gun, the electron bunch parameters were measured at two laser pulse durations, ~7ps and ~28ps FWHM. The shorter laser pulse is the intrinsic output of the laser, while the longer pulse was produced with the use of a pulse stacker. The electron bunch parameters that were measured included transverse emittance, correlated and uncorrelated energy spread and bunch length. The experimental results and their comparison with computer simulations are presented and discussed.
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| MOPC066 |
Optimisation of a SRF High Average Current SRF Gun
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220 |
| |
- C. D. Beard, J. W. McKenzie, B. L. Militsyn, B. D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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An approximately 100 mA and 10 MeV continuous wave electron injector is required to deliver high brightness electron bunches for the spontaneous and VUV radiation sources. One of possible solutions might be a Superconductive RF (SRF) gun. Optimisation of the first half cell of the gun has been carried out to maximise the acceleration whilst providing additional focussing through shaping of the cathode region to meet the design specification. In this paper, the cavity design and specification are presented together with some initial optimisations.
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| TUPC002 |
Design of a Tomography Module for the PITZ Facility
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1038 |
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- G. Asova, K. Floettmann
DESY, Hamburg
- D. J. Holder, B. D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- S. Khodyachykh, S. A. Korepanov, M. Krasilnikov, S. Rimjaem, F. Stephan
DESY Zeuthen, Zeuthen
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The goal of the Photo Injector Test Facility at DESY in Zeuthen (PITZ) is to develop sources of high phase-space density electron beams that are required for the successful operation of SASE FELs. This requires detailed characterization of the sources and therefore the development of suitable advanced diagnostics. As part of the ongoing upgrade towards higher beam energies, new diagnostics components are being installed. An example is a tomography module for transverse phase space reconstruction which is designed to operate in the energy range between 15 and 40 MeV. The module consists of four observation screens with three FODO cells between them. A number of upstream quadrupoles are used to match the beam envelope parameters to the optics of the FODO lattice. This contribution presents the final design of the tomography module. Data from numerical simulations are used to illustrate the expected performance and to compare it to a simplified setup of two quadrupoles. The quality of the reconstruction is revised with the help of different algorithms.
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| WEPC085 |
Matching with Space Charge
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2192 |
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- B. D. Muratori, D. J. Holder
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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This paper explores the possibility of performing matching in the presence of space charge to an acceptable and useful level. Space charge gives rise to a mismatch for beams at low energies. This mismatch can be very harmful for certain applications, for example the tomography diagnostic of the PITZ2 test line. In this case, the Twiss parameters at the start of the tomography section have to be as close as possible to the design ones. As can be shown by a thin lens approximation, all the Twiss parameters at the start of the tomography section are fully determined, as is the quadrupole strength, once the length of the FODO cells is chosen. With the presence of space charge it is necessary to introduce a modification to the original matching, itself performed with a standard optimizing routine. The idea is that this modification can only compensate for the linear part of space charge and it does so by changing the quadrupole strengths. The theory is verified by using an very simple test line consisting of just two quadrupoles and modeling it using GPT (General Particle Tracer). This results in modified values for the quadrupole strengths to accommodate the effect of space charge.
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| THPP006 |
Injection and Extraction for the EMMA NS-FFAG
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3386 |
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- B. D. Muratori, S. L. Smith, S. I. Tzenov
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- C. Johnstone
Fermilab, Batavia, Illinois
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EMMA (Electron Machine with Many Applications) is a prototype non-scaling electron FFAG to be hosted at Daresbury Laboratory. NS-FFAGs related to EMMA have an unprecedented potential for medical accelerators for carbon and proton hadron therapy. It also represents a possible active element for an ADSR (Accelerator Driven Sub-critical Reactor). This paper will summarize the design of the extraction and injection transfer lines of the NS-FFAG. In order to operate EMMA, the Energy Recovery Linac Prototype (ERLP) shall be used as injector and the energy will range from 10 to 20 MeV. Because this would be the first non-scaling FFAG, it is important that as many of the bunch properties are studied as feasible, both at injection and at extraction. To do this, a complex injection line was designed consisting of a dogleg to extract the beam from ERLP, a matching section, a tomography section and some additional dipoles and quadrupoles to transport the beam to the entrance of EMMA. Further, an equivalent tomography module was placed in the extraction line together with several other diagnostic devices including the possibility of using a transverse deflecting cavity.
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| THPP008 |
Hamiltonian Approach to the Dynamics of Particles in Non-scaling FFAG Accelerators
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3392 |
| |
- B. D. Muratori, S. L. Smith, S. I. Tzenov
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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Starting from first principle the Hamiltonian formalism for the description of the dynamics of particles in non-scaling FFAG machines has been developed. The stationary reference (closed) orbit has been found within the Hamiltonian framework. The dependence of the path length on the energy deviation has been described in terms of higher order dispersion functions. The latter have been used subsequently to specify the longitudinal part of the Hamiltonian. It has been shown that higher order phase slip coefficients should be taken into account to adequately describe the acceleration in non-scaling FFAG accelerators.
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| THPP009 |
Injection and Extraction Orbits and Twiss Parameters for the EMMA Ring
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3395 |
| |
- B. D. Muratori, S. L. Smith, S. I. Tzenov
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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Using the FFEMMAG code, the injection and extraction orbits for the EMMA ring at a variety of injection and extraction energies together with the Twiss parameters to be used for matching have been calculated. The orbits include two kickers together with a septum at both injection and extraction. The FFEMMAG code has been used in conjunction with several scripts so as to be able to scan the parameter space of the two kicker strengths for a section of the EMMA ring. The results confirm the choice of magnet and vacuum pipe apertures as being adequate to operate EMMA from 10 to 20 MeV.
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| THPP004 |
EMMA - the World's First Non-scaling FFAG
|
3380 |
| |
- T. R. Edgecock
STFC/RAL, Chilton, Didcot, Oxon
- C. D. Beard, J. A. Clarke, C. Hill, S. P. Jamison, A. Kalinin, K. B. Marinov, N. Marks, P. A. McIntosh, B. D. Muratori, H. L. Owen, Y. M. Saveliev, B. J.A. Shepherd, R. J. Smith, S. L. Smith, S. I. Tzenov, E. Wooldridge
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- J. S. Berg, D. Trbojevic
BNL, Upton, Long Island, New York
- N. Bliss, C. J. White
STFC/DL, Daresbury, Warrington, Cheshire
- M. K. Craddock
UBC & TRIUMF, Vancouver, British Columbia
- J. L. Crisp, C. Johnstone
Fermilab, Batavia, Illinois
- Y. Giboudot
Brunel University, Middlesex
- E. Keil
CERN, Geneva
- D. J. Kelliher, S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
- S. R. Koscielniak
TRIUMF, Vancouver
- F. Meot
CEA, Gif-sur-Yvette
- T. Yokoi
OXFORDphysics, Oxford, Oxon
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EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory in the UK and will be the first non-scaling FFAG ever constructed. EMMA will be used to demonstrate the principle of this type of accelerator and study their features in detail. The design of the machine and its hardware components are now far advanced and construction is due for completion in summer 2009.
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