LCLS Conceptual Design Report - Stanford Synchrotron Radiation ...

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L C L S C O N C E P T U A L D E S I G N R E P O R T In addition, a 55-cm long S-band transverse RF deflecting structure will be located just after the L0-linac (see “RF Kicker” in Figure 7.32). This system will be used to ‘streak’ the bunch for bunch-length, slice emittance, and slice energy spread measurements using screens in the DL1 system. This diagnostic is described in more detail in Section 7.8.2. An insertable tune-up dump will also be included after DL1 in order to allow invasive tuning of the DL1 and upstream systems. The dump will need to handle a 1-nC beam at 120 Hz and 150 MeV or 18-W of average power. 7.5.2 High-Energy Dog-Leg The requirements for beam transport from the L3-linac to the <strong>LCLS</strong> undulator are fairly simple. The transport line must: • Include bends to introduce precise energy and energy spread measurement capability without generating significant CSR or other emittance dilution effects, • Include precise transverse emittance and matching diagnostics for final verification/tuning prior to undulator, • Provide adjustable undulator-input beta-matching for the various beam energies (i.e., various radiation wavelengths) desired, • Not alter the bunch length (must be nearly isochronous), • Make use of the existing FFTB tunnel and its components wherever possible, as long as the performance of the transport line is not compromised, • Adjust the vertical beamline angle to remove the 0.3˚ downward linac angle so that experimental areas do not need to be located below ground level. Energy and energy spread diagnostics are built into a four dipole horizontal inflector beamline (DL2) where the first bend is located just inside the beginning of the undulator hall, which previously housed the Final Focus Test Beam (FFTB). Primarily to meet the small energy spread measurement capability, a doublet of Chasman-Green [35] type cells is used. A cell consists of a dipole pair sandwiching a quadrupole triplet. The horizontal dispersion function in the center of each cell reaches a maximum, while the horizontal beta function converges towards a minimum. A horizontal OTR monitor here (ηx ≈ 50 mm, βx ≈ 1.6 m) is capable of measuring an rms energy spread of 0.03% at 14.3 GeV with a nominal betatron beam size contribution of only 10% at γεx ≈ 1 µm (see Secs. 7.8.2 and 7.8.2.3). The Chasman-Green type cells are advantageous since they introduce very little path length energy dependence and generate minimal emittance dilution due to synchrotron radiation. The net system forms a 4-dipole dog-leg (DL2) displacing the beamline horizontally toward the south by 0.45 m. The net R56 for the 4-dipole system is set to zero by allowing the dispersion function to reverse sign in half of the bends (see Figure 7.36). Bends of θ B ≈ 0.65° and L B ≈ 2.62 m produce R56 ≈ 0, and a second order term of T566 ≈ 73 mm, which is, for a worst-case energy spread of ~0.1%, completely isochronous (i.e., 7-60 ♦ A C C E L E R A T O R
L C L S C O N C E P T U A L D E S I G N R E P O R T 0.073-µm axial position shift per 0.1-% energy deviation). The emittance dilution due to incoherent synchrotron radiation at 14.3 GeV is insignificant at 1%. In order to include a high-resolution relative energy spectrometer that is insensitive to variable incoming betatron oscillations, the centers of the Chasman-Green cells are separated by a unity optical transformer (+I) in the horizontal plane. The signals from two BPMs, one placed at the maximum dispersion point in each cell, are then subtracted to eliminate all incoming betatron oscillations and to enhance the relative energy signal (the dispersion is of opposite sign in the two cells—see Figure 7.36). With two BPMs of 10-µm resolution, a relative energy change of 8×10 –5 can be resolved per pulse. Such resolution will be used in an energy feedback system controlling the L3-linac rf (see Section 7.8.4). Two vertical dipole magnets in DL2 remove the downward vertical angle imposed by the orientation of the SLAC linac. An upward net bend of 0.3˚ is added after the last horizontal bend. This makes the undulator level with respect to gravity. The vertical bends are 0.4 m long and each bend 0.15˚. They are separated by four quadrupole magnets to form a linear achromat (see Figure 7.36). These vertical bends are too weak to generate significant momentum compaction or synchrotron radiation (coherent or otherwise). 7.5.2.1 Parameters DL2 follows the beam switchyard (BSY), which transports electrons from linac to undulator hall. The DL2 parameters are summarized in Table 7.19. Beta-functions and dispersion are shown in Figure 7.36. The energy spread measuring profile monitor is indicated at S ≈ 1236 m. β (m) 50 40 30 20 10 0 B31 QL31 QL32 QL33 B32 QL34 QL35 QL36 B33 QL37 QL38 QL39 B34 QM31 QM32 VB1 QVB1 QVB2 QVB3 QVB4 VB2 QM33 QM34 1210 1220 1230 1240 S (m) 1250 1260 1270 QE31 QE32 QE33 QE34 β x β y η x η y QE35 QE36 QM35 QM36 QM37 QM38 −0.05 Figure 7.36 Dispersion and beta functions through DL2/ED2 beamline up to undulator entrance. Four-dipole dog-leg (DL2), 2-dipole vertical bend (VB), and final diagnostic section (ED2) are shown. Profile monitors are indicated by small circles in top schematic. Table 7.19 Nominal parameters of high-energy dog-leg (DL2) beamline. 0.1 0.05 0 −0.1 η (m) A C C E L E R A T O R ♦ 7-61
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Linac Coherent Light Source (LCLS)
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L C L S C O N C E P T U A L D E S I
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Preface This Conceptual Design Repo
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Table of Contents 1 Executive Summa
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6. Two experiment halls L C L S C O
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2.7.1.7 Conventional Facilities L C
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3 TECHNICAL SYNOPSIS Scientific Bas
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5 TECHNICAL SYNOPSIS FEL Parameters
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and the total peak beam power L C L
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5.4.2.2 Case II - High Charge Limit
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∆P ∆I sat pl / P / I sat pk L C
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5.9 Summary L C L S C O N C E P T U
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6 Injector TECHNICAL SYNOPSIS The i
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εn,x (µm) 4 3 2 1 4-2001 8560A95
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Quantum Yield (electrons/photon) 10
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Bz (T) 0.3 0.2 0.1 1-2002 8560A92 L
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Master Clock 9.917 MHz x8 x6 x6 Df
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1-2002 8560A198 Linac Center Line L
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B z (kG) 3 2 1 4-2001 8560A91 L C L
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γε x,y (µm) 3 2 1 0 3-2001 8560A
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γεx,y (µm) yn 10 0 -10 -10 0 10
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σ γ /γ 0 (percent) ∆N/N 0.02 0
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5 0 -5 5 0 -5 5 0 -5 L C L S C O N
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Table 6.5 PARMELA Output Parameters
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gama x (micro.m) 3 2 1 0 0 L C L S
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∆E/E 0 (%) ∆N/N 0 -1 -2 0.02 0
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Page 256 and 257: economic reasons. L C L S C O N C E
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Magnet String Location Existing, Ne
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8.1 Overview 8.1.1 Introduction L C
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Mu in the pole, for mu
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Gasload (Torr-l/sec-cm) (x10 -12 )
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8.10.4 Conclusion L C L S C O N C E
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x θ j > 0 L C L S C O N C E P T U
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Quad ∆X/µm Quad ∆Y/µm −500
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∆X/µm ∆Y/µm L C L S C O N C E
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8.13.2 Undulator Cell Structure L C
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9.2 Layout and Optics 9.2.1 Experim
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Fast Valve L C L S C O N C E P T U
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0.01 10 -4 10 -6 10 -8 10 -10 10 -1
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Table 9.5 Mirror requirements L C L
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Refractive Focusing System L C L S
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Pulse Split/Delay L C L S C O N C E
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Figure 9.20 LCLS Ion Chamber L C L
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9.4.3.2 Pulse Length L C L S C O N
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9.4.3.6 Divergence L C L S C O N C
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10 Conventional Facilities TECHNICA
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1-2002 8560A198 Linac Center Line L
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Figure 10.6 Near hall floor plan 10
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11 Controls TECHNICAL SYNOPSIS The
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11.5.3 Motion Controls L C L S C O
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12.1 Procedural Overview L C L S C
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13 Environment, Safety and Health a
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Table 13-1 Hazard Identification an
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13.1 Ionizing Radiation The design
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Table 13-2 Minimum Training Require
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13.10 SLAC References L C L S C O N
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L C L S D E S I G N S T U D Y R E P
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15 TECHNICAL SYNOPSIS Work Breakdow
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A A.1 FEL-Physics A.1.1 Performance
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A.2 Photo-Injector A.2.1 Gun-Laser
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A.2.3.2 Electron Beam L C L S C O N
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A.2.4.7 Vacuum L C L S C O N C E P
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A.3.8 DL-2 A.3.8.1 Subsystem L C L
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A.4 Undulator A.4.1 Undulator A.4.1
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B Control Points B.1 Injector Contr
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C Glossary ACO Anneaux Collisions O
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