Machine:Injection System

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Introduction

The Sirius injection system is composed of a 150 MeV Linac, a full energy 3 GeV synchrotron booster operating in top-up mode and 2 transport lines, one from the Linac to the Booster (LTB) and another from the Booster to the Storage Ring (BTS). The booster and the storage ring are concentric and share the same tunnel. Their injection sections are placed close together to restrict the 'dirty' area in terms of radiation. A general layout of the Sirius injection system is shown in Figure 1.

Figure 1: Layout of the Sirius injection system with a 150 MeV Linac and a full energy 3 GeV booster in the same tunnel as the storage ring. The booster and storage ring injection sections are placed close together to restrict the 'dirty' area in terms of radiation.


Booster

Linear Optics

The booster lattice consists of 50 modified FODO cells with combined-function magnets suitable to provide low emittance. The main difference from other booster designs is that the Sirius booster contains only arc sections: no long dispersion-free straight sections are provided. This means that injection and extraction, as well as the Petra 5-cell RF cavity, are located in these dispersive straight sections. With this concept a very high lattice symmetry for the booster is obtained and only a few magnet families are necessary. A high lattice symmetry is not only beneficial for beam dynamics but also to maximize the radial distance between the storage ring and the booster beam centers, minimizing the variations in the size of the corridor between the two concentric rings.

The lattice is composed of three main families of magnets: combined function dipoles (BD), with defocusing quadrupole and sextupole field components, focusing quadrupoles (QF) and focusing sextupoles (SF). Together, they define the working point and set the chromaticities to +0.5 in both planes. The achieved natural emittance at the extraction energy of 3 GeV is very low, which is essential to provide a clean injection process into the storage ring with the nonlinear kicker injection process.

The families of focusing quadrupoles QF and the defocusing quadrupolar component in the dipoles BD set the nominal horizontal and vertical tunes. In order to allow for flexibility in tune adjustment, an extra family of weak corrector quadrupoles QD is added to the lattice. A QD quadrupole is placed every two dipoles, right next to it. In the same way, the chromaticities are set to +0.5 in both planes by the family of sextupoles SF and the defocusing sextupolar component in the dipoles BD; and to allow flexibility for chromaticity adjustment, an extra family of corrector sextupoles SD is introduced. A sextupole corrector SD is placed every five dipoles in the lattice. There are 2 kinds of straight sections connecting the dipoles: odd sections contain orbit correctors and even sections contain quadrupoles QD and sextupoles SF. All sections contain quadrupoles QF and BPMs. Ten sextupoles SD are distributed in odd and even sectors. A schematic diagram of the Booster straight sections is shown in Figure 3

The booster main parameters are summarized in Table 1 and Table 2, and the optical functions are shown in Figure 2.

Table 1: Major Sirius BO main parameters.
Lattice version V03
Beam extraction energy 3.0 GeV
Beam injection energy 0.150 GeV
Beam current 2.0 mA
Circumference 496.800 m
Revolution frequency 0.603 MHz
Revolution period 1.657 μs
Cycling frequency 2 Hz
Betatron tune, horizontal 19.204
Betatron tune, vertical 7.314
Momentum compaction factor 7.19×10-4
Natural chromaticity, horizontal -33.70
Natural chromaticity, vertical -13.95
Natural emittance 3.47 nm⋅rad
Natural energy spread 0.087  %
Damping time, horizontal 11.3 ms
Damping time, vertical 13.8 ms
Damping time, longitudinal 7.7 ms
RF frequency 499.654 MHz
Harmonic number 828

Table 2: Sirius booster magnets main parameters.
Dipoles Name DipB
Number 50
Length 1.221 m
Dipole field (min/max) 0.0515 / 1.030 T
Bending radius 9.716 m
Integrated* quadrupole grad. (min/max) 0.12 / 2.48 T
Integrated* sextupole grad., ∫B"/2.ds, (min/max) 1.28 / 25.63 T·m-1
QF Quadrupoles Name QF
Number 50
Effective magnetic length 0.228 m
Maximum gradient -18.7 T·m-1
QD Quadrupoles Name QD
Number 25
Effective magnetic length 0.100 m
Maximum gradient ± 5.3 T·m-1
QS (skew) Quadrupoles Name QS
Number 1
Effective magnetic length 0.100 m
Maximum gradient ± 1.6 T·m-1
Sextupoles Names SF and SD
Number (SF + SD) (25 +10)
Effective magnetic length 0.105 m
Max. integrated gradient, ∫B"/2.ds 200.14 T·m-2
* integration along particle trajectory.
Figure 2: Twiss functions for V02.


Figure 3: Booster straight sections. All 50 sections contain a QF in the center and a BPM in the Upstream part. Odd sections contain correctors CH and CV in the Upstream part, and Even sections contain SF (Upstream) and QD (Downstream). Section 49, where extraction septa are located, is an exception with CH in the Downstream part. The 10 sextupoles SD are distributed in Odd and Even sections.

Tune correction

Tune correction in the Sirius Booster will be performed with QF and QD families:

where is the tune and is the integrated quadrupole strength.

Chromaticity Correction

Chromaticity correction in the Sirius Booster will be performed with SF and SD families.

where is the chromaticity and is the integrated sextupole strength. From the above equation, we notice the chromaticity is corrected to 0.5 in both planes when and are equal to 1.189 and 0.742, respectively.

To specify the maximum SD integrated strength, we considered, among others, the effect of a systematic error of 12% in the sextupolar component of the dipoles and a range of variation of chromaticity of [0.5,4.0] in both planes.

Error Tolerance Specifications

Assumed multipole errors for Booster dipoles, quadrupoles and sextupoles are shown in Table 3, Table 4 and Table 5

Booster Magnets Multipole Errors

Table 3: Booster dipole multipole errors specification. Standard deviation for random multipole errors; simulations assume Gaussian distribution truncated at ±2σ.
Multipole error Systematic Random
Normal Skew
Dipoles
@r = 17.5 mm
B2/B0 (sextupole) -- 5.5×10-4 * 1.0×10-4
B3/B0 (octupole) +4.0×10-4 4.0×10-4 1.0×10-4
B4/B0 (decapole) -3.6×10-4 4.0×10-4 1.0×10-4
B5/B0 (12-pole) +2.7×10-4 4.0×10-4 1.0×10-4
B6/B0 (14-pole) -1.3×10-4 4.0×10-4 1.0×10-4
  • * This spec is replicated in the dipole alignment and rotation errors table
  • Actual designed dipole model shows numbers are that in accordance with these specs. (see fieldmap analysis)

Table 4: Booster QF quadrupole multipole errors. Standard deviation for random multipole errors; simulations assume Gaussian distribution truncated at ±2σ.
Multipole error Systematic1 Random
Normal Skew
quadrupoles
@r = 17.5 mm
B2/B1 (sextupole) -- 7.0×10-4 1.0×10-3
B3/B1 (octupole) -- 4.0×10-4 5.0×10-4
B4/B1 (decapole) -- 4.0×10-4 1.0×10-4
B5/B1 (12-pole) -1.0×10-3 4.0×10-4 1.0×10-4
B6/B1 (14-pole) -- 4.0×10-4 1.0×10-4
B7/B1 (16-pole) -- 4.0×10-4 1.0×10-4
B8/B1 (18-pole) -- 4.0×10-4 1.0×10-4
B9/B1 (20-pole) +1.1×10-3 -- --
B13/B1 (28-pole) +8.0×10-5 -- --

1 Multipoles of prototype magnets measured with radial rotating coils

Table 5: Booster sextupole multipole errors. Standard deviation for random multipole errors; simulations assume Gaussian distribution truncated at ±2σ.
Multipole error Systematic1 Random
Normal Skew
sextupoles
@x = 17.5 mm
B3/B2 (octupole) -- 4.0×10-4 1.0×10-4
B4/B2 (decapole) -- 4.0×10-4 1.0×10-4
B5/B2 (12-pole) -- 4.0×10-4 1.0×10-4
B6/B2 (14-pole) -- 4.0×10-4 1.0×10-4
B7/B2 (16-pole) -- 4.0×10-4 1.0×10-4
B8/B2 (18-pole) -2.7×10-2 4.0×10-4 1.0×10-4
B9/B2 (20-pole) -- 4.0×10-4 1.0×10-4
B14/B2 (30-pole) -1.4×10-2 -- --

1Relative multipoles calculated around the Runge-Kutta trajectory for the latest sextupole model-03 fieldmap at 3 GeV

Booster Magnets Alignment and Excitation Errors

Table 6: Maximum absolute value of random alignment and excitation errors for the Booster. The errors are generated with a Gaussian distribution truncated at ±1σ.
Dipoles Quadrupoles Sextupoles BPMs
Transverse position, , 160 160 160 300 μm
Rotation around longitudinal axis 0.8 0.8 0.8 -- mrad
Excitation error (static or low frequency) 0.15 0.3 0.3 --  %
Dipole Gradient Error 2.4 -- -- --  %

Booster Magnets High Frequency Errors

Table 7: Booster magnets high frequency errors.
Girder vibration rms amplitude 500 nm
Power supply ripple
Tracking error 100 ppm

Closed orbit correction system

The specification for the closed orbit correction system for the Sirius booster is in Table 8 and its distribution along the ring is shown in Figure 4. To calculate corrector kicks and estimate residual orbit displacements, we have simulated static orbit distortions due to random alignment and excitation errors in all magnets in the lattice (see Table 6). These are relaxed error tolerances, we expect better results for the real machine. The implicit safety margin that is assumed should account for the dynamic effects during energy ramping that were not taken into account in these calculations. The closed orbit before correction is shown in Figure 5 and the residual closed orbit distortion after correction is shown in Figure 6. The corrector strengths are listed in Table 9

Figure 4:

Table 8: Parameters of the global closed orbit and coupling correction system for the Booster.
Number of BPMs 50
Number of horizontal dipole correctors 25
Number of vertical dipole correctors 25
Maximum horizontal dipole corrector strength 310 μrad
Maximum vertical dipole corrector strength 310 μrad
Figure 5: Horizontal (blue) and vertical (red) uncorrected closed orbit for 20 random booster machines. The bold curves represent one rms value.
Figure 6: Horizontal (blue) and vertical (red) corrected closed orbit for 20 random booster machines. The bold curves represent one rms value.

Table 9: Statistics of orbit correction in the Booster for 20 random machines.
Horizontal Vertical
COD rms 238 380 µm
COD rms @ BPMs 247 284 µm
Rms corrector strength 60 89 µrad
Max. corrector strength 186 253 µrad

Aperture requirements

The physical aperture requirements for the booster are defined by the injected Linac beam size and energy variation from pulse to pulse, by the closed orbit distortions and by a tolerance for beam oscillations after injection. During acceleration the beam size shrinks as well as the oscillations due to mismatched energy, position and angle of the injected beam.

The beam stay clear (half-aperture) was defined by the following formulae:

The resulting requirements are illustrated in Figure 7.

Figure 7: The half-aperture requirements for the Booster are based on error tolerances for the injected beam at 120 MeV. Allowances in both planes (horizontal and vertical) have been set for orbit distortions and residual beam oscillations due to errors in meeting the on-axis injection conditions. In the horizontal plane, an extra allowance is set for a Linac beam energy mismatch.

The booster vacuum chambers will be made of 1 mm thick stainless steel cylindrical tubes with inner diameter of 23.4 mm at the dipoles and 36 mm at the straight sections.


Dynamic aperture

The chromaticity correction sextupoles, multipole components in dipoles and quadrupoles, and alignment errors reduce the dynamic aperture to about ±12 mm in the horizontal and ±4 mm in the vertical plane at the injection point. This is sufficiently large for an efficient on-axis injection and for beam lifetime. Figure 8, Figure 9 and Figure 10 show the dynamic and momentum apertures for 20 machines with random multipole, alignment and excitation errors in all magnets.

Figure 8: On-momentum dynamic aperture at the center of quadrupole QF for 20 machines with alignment and multipole errors, orbit and tune corrections. The color scale represents the percentage of machines in which a given point of the grid is stable. For these calculations, the following configuration was used: 6D tracking with Trackcpp; 5000 turns for on-momentum and off-momentum apertures; The vacuum chamber physical aperture (17.5x17.5 mm2 in the straights and 12x12 mm2 in the dipoles) is considered along the ring.
Figure 9: Off-momentum dynamic aperture at the center of quadrupole QF for 20 machines with alignment and multipole errors, orbit and tune corrections. The color scale represents the percentage of machines in which a given point of the grid is stable. For these calculations, the following configuration was used: 6D tracking with Trackcpp; 3500 turns for on-momentum and off-momentum apertures; The vacuum chamber physical aperture (17.5x17.5 mm2 in the straights and 12x12 mm2 in the dipoles) is considered along the ring.
Figure 10: Momentum aperture for 1/10 of the Booster for 20 machines with alignment and multipole errors, orbit and tune corrections. For this calculation, the following configuration was used: 6D tracking with Trackcpp; 2000 turns; The vacuum chamber physical aperture (17.5x17.5 mm2 in the straights and 12x12 mm2 in the dipoles) is considered along the ring. Black lines represent the loss rate.

Booster injection

The 150 MeV electron beam from the Linac is injected on axis into the booster. The injection septum and the on-axis injection kicker are shown in Figure 43, the horizontal trajectory of the injected beam in Figure 12 and a cross section at the injection point in Figure 13. The injection point at the booster is defined at the physical end of the injection septum.


Figure 11: Booster injection section layout.


Figure 12: Trajectory of the injected beam from the Linac in the horizontal plane. The solid red curve represents the injected beam centroid and the dashed curves represent ±3σx beam envelope.


Figure 13: Schematic representation of the transverse cross section at booster injection point. Incoming beam from TB is moving towards the viewer.

Booster extraction

Two kickers are used to extract the beam from the booster. They deflect the beam towards the extraction septum, passing through a defocusing dipole and a tune corrector quadrupole along the way. The nominal strength for this quadrupole is zero, it will only be used for small tune corrections. The arrangement of the booster extraction system elements is shown in Figure 44.

Figure 14: Booster extraction layout.


The extracted beam horizontal trajectory is shown in Figure 15. Due to the large amplitude of the extracted beam, the horizontal size of the dipole vacuum chamber next to the septum will have to be increased. The beam arrives at the septum with an amplitude of x=22 mm and angle of x'=5.0 mrad. This amplitude considers:

Table 10: Booster extraction apertures.
half-aperture for stored beam 18.0 mm
vacuum chamber thickness 1.0 mm
septum thickness 3.3 mm
half-aperture for extracted beam (4σ) 1.0 mm
Total 23.3 mm
Figure 15: Trajectory of the extracted beam from the booster in the horizontal plane. The solid red curve represents the extracted beam trajectory calculated by the linear model and the dashed curves represent ±4σx beam envelope. The green curve is the horizontal beam stay clear. Due to the large amplitude of the extracted beam at the dipole, the beam trajectory has also been calculated by Runge-Kutta integration using the simulated dipole field map (dark blue curve).
Figure 16: Schematic representation of transverse cross section at booster extraction point.

Booster RF system

Table:Booster RF parameters shows the design parameters of the RF system for the booster. The value of the Peak RF voltage presented in the table was calculated assuming the energy spread of the beam could be 90% larger than the expected value, also present in the table, and the momentum compaction could be 30% higher than the value in the table. These are very pessimistic scenarios for the system design, being the nominal

Table 11: Parameters used to design the booster RF system.
Beam energy 3.0 GeV
Beam current 2.0 mA
Energy loss/turn 721.3 keV
SR power 1.44 kW
Cavity type PETRA 5-cell
Peak RF voltage 1.05 MV
Total scaled shunt impedance 15 MΩ
Maximum RF power needed 45.0 kW
Energy spread 0.0874  %
RF frequency 499.654 MHz
RF wavelength 0.6000 m
Harmonic number 828
Momentum compation factor 7.19×10-4
Overvoltage 1.456
Synchronous phase 136.6 °
Synchrotron tune 0.0044
Synchrotron frequency 2.67 kHz
Natural bunch length 11.25 mm
Natural bunch length 37.53 ps
Energy acceptance 0.79  %
Quantum lifetime 4267 s
Linac to Booster phase stability @500MHz 5.0 °

Booster straight sections allocation

Sector U (upstream of QF) D (downstream of QF)
01 InjSept InjKckr, Scrn-1, Scrn-2
02 Scrn QS, TuneShkr
03 chicane
04 TunePkup GSL
05 P5Cav
06
07
08 chicane
09
10
11
12
13 chicane
14
15
16
17
18 chicane
19
20
21
22
23 chicane
24
25
Sector U (upstream of QF) D (downstream of QF)
26
27
28 chicane
29
30
31
32
33 chicane
34
35 DCCT
36
37
38 chicane
39
40
41
42
43 chicane
44
45
46
47 chicane
48 EjeKckr
49 EjeSeptF
50


QS = Skew Quadrupole

GSL = Generic Stripline

TunePkup = Tune Pickup

TuneShkr = Tune Shaker

InjKckr = Injection Kicker

InjSept = Injection Septum

EjeKckr = Ejection Kicker

Scrn = Fluorescent Screen

Linac

The Sirius 150 MeV Linac is a 'turn-key' system provided by SSRF/SINAP. The Linac design parameters are specified in Table 14.

Table 14: Main parameters of Sirius Linac in multi-bunch and single-bunch operation modes.
Multi-bunch Single-bunch
Energy 150 150 MeV
Frequency (e-gun and SHB) 499.664 499.664 MHz
Frequency (accelerating structures) 2997.948 2997.948 MHz
Normalized emittance 50 50 π·mm·mrad
Relative energy spread (rms) 0.5 0.5  %
Pulse to pulse energy variation 0.25 0.25  %
Pulse to pulse beam position variation 0.20 0.20 mm
Pulse to pulse jitter 100 100 ps
Pulse charge 3 1 nC
Pulse duration 150 to 300 1 ns
Repetition rate 2 2 Hz


Figure 17: General layout of Sirius 150 MeV Linac.
Figure 18:
Figure 19: Schematic diagram of Sirius 150 MeV Linac.

Linac pictures during FAT at SSRF

LI injector assembly.png
LI AccelStruct assembly 3.png
LI AccelStruct assembly 1.png
LI AccelStruct assembly 2.png

Linac to booster transport line (LTB)

The Linac-to-Booster transport line (LTB - naming initials TB), transports the 150 MeV electron beam from the end of the Linac (by definition, just after the last accelerating section) to the booster injection point, just after the injection septum. A general view of the LTB transport line is shown in Figure 24. A schematic diagram of the LTB elements with their names is shown in Figure 25. The main parameters are shown in Table 15.

Figure 24: Overview of the LTB transfer line.
Figure 25:


Table 15: Main parameters of the LTB transfer line.
Nominal energy 150.0 MeV
Lattice version V02
Total length including septum 21.2475 m


LTB Lattice

The LTB lattice is composed of two chromatic sections separated by an achromatic section. In the first chromatic section just after the Linac the dispersion function is negative, created by two negative deflection dipoles. The first dipole is also a beam energy spectrometer for the Linac. An energy slit is placed in this section at the position where the energy resolution is maximum, i.e., where the relation ηxx is maximum. In the achromatic section, the LTB line goes through a shielding wall separating the Linac from the storage ring tunnel. In the last chromatic section the dispersion is positive and the optical functions are matched to the Booster's functions. The beam is injected on-axis into the Booster.

Since the optical functions at the Linac exit are not precisely known, we have considered 6 different initial condition modes (M1, ... , M6) for the transport line and looked for solutions that are flexible enough to accommodate all modes. The initial Twiss functions for the modes are shown in Table 16, where several different combinations of initial αx and αy are covered. The corresponding optical functions are shown in Table 17.


Table 16: Initial Twiss functions for the LTB transfer line modes, and matching parameters at booster injection point.
Linac exit Booster injection
M1 M2 M3 M4 M5 M6
βx 7.0 10.0 7.0 7.0 7.0 7.0 14.673 m
αx 0.0 0.0 -1.0 +1.0 +1.0 -1.0 -3.407
βy 7.0 10.0 7.0 7.0 7.0 7.0 9.649 m
αy 0.0 0.0 -1.0 +1.0 -1.0 +1.0 1.657
ηx 0.0 0.0 0.0 0.0 0.0 0.0 0.291 m
η'x 0.0 0.0 0.0 0.0 0.0 0.0 0.069

Table 17: Optical functions along the LTB transfer line for 6 different initial condition modes.
TB twiss M1.svg TB twiss M4.svg
TB twiss M2.svg TB twiss M5.svg
TB twiss M3.svg TB twiss M6.svg


LTB Beam Size and Aperture Requirement

The figures below show the horizontal and vertical beam sizes along LTB for the different modes M1 to M6. The beam parameters at the Linac end are: emittance: εx = εy = 170 nm.rad; rms energy spread: δ=0.5%.

Figure 26: Horizontal beam size along LTB transfer line for various operation modes. Different operation modes correspond to different initial conditions for the optical functions at the Linac end. The beam sizes are calculated for the following parameters: beam energy=150 MeV; emittance: εx = εy = 170 nm.rad; rms energy spread: δ=0.5%.
Figure 27: Vertical beam size along LTB transfer line for various operation modes. Different operation modes correspond to different initial conditions for the optical functions at the Linac end. The beam sizes are calculated for the following parameters: beam energy=150 MeV; emittance: εx = εy = 170 nm.rad; rms energy spread: δ=0.5%.


The aperture requirements and BSC for the LTB transport line are calculated considering a clearance for residual orbit distortion and trajectory variations due to pulse to pulse differences in beam energy and launching conditions (position and angle) as described in Table 18.


Table 18: Parameters for LTB transfer line aperture and BSC calculations.
Max. orbit distortion along LTB (H and V) ± 1 mm
Linac pulse to pulse energy variation 0.4  %
Linac pulse to pulse beam centroid position/angle variation (H and V) 40 nm.rad
LTB vacuum chamber inner aperture (full) at quadrupoles (H / V) 36.1 / 36.1 mm
LTB vacuum chamber inner aperture (full) at dipoles (H / V) 23.4 / 23.4 mm
Number of beam sigmas that fit in the aperture (H / V) ± 3.3 / ± 4.6


The calculated horizontal and vertical BSC for LTB transport line modes are shown in the figures below.

Figure 28: Horizontal beam stay clear (BSC) for LTB transfer line. The BSC can accommodate the residual orbit distortion and trajectory variations due to pulse to pulse differences in beam energy and launching conditions (position and angle) described in Table 18. The vacuum chamber inner half-aperture is represented by the solid black curve.
Figure 29: Vertical beam stay clear (BSC) for LTB transfer line. The BSC can accommodate the residual orbit distortion and trajectory variations due to pulse to pulse differences in launching conditions (position and angle) described in Table 18. The vacuum chamber inner half-aperture is represented by the solid black curve.


LTB Orbit Correction

The LTB orbit correction parameters are shown in Table 19 and the magnet alignment and excitation error tolerances assumed for orbit correction studies in the LTB transport line are shown in Table 20. The trajectory correction statistics are shown in Table 21 and the orbits before and after correction for all modes are shown in Table 22. The correction system uses a beam position measurement station with integrated fluorescent screens and striplines. The injection septum is used as corrector to adjust horizontal position and angle at the booster injection point.


Table 19: Parameters for LTB transfer line orbit correction.
Number of beam position measurement stations 6
Number of horizontal correctors 6
Number of vertical correctors 6
Maximum corrector strength ± 2.5 mrad


Table 20: Errors for LTB transfer line orbit correction simulation. A uniform random error distribution is assumed.
Type of error (applied to all magnets)
X alignment ±0.3 mm
Y alignment ±0.3 mm
Roll angle ±0.4 mrad
Relative field error ±0.1  %
BPM alignment error
X alignment ±0.5 mm
Y alignment ±0.5 mm
Error in beam launching conditions
x ±0.4 mm
θx ±0.1 mrad
y ±0.4 mm
θy ±0.1 mrad
dp/p ±0.5  %

Table 21: Orbit correction statistics over 100 random seeds for LTB transfer line modes M1 to M6.
Orbit in mm
before after
Max. rms H orbit 2.1 ± 0.14 0.53 ± 0.02
Max. rms V orbit 1.6 ± 0.29 0.40 ± 0.02
Max. rms H orbit @ BPMs 1.6 ± 0.09 0.31 ± 0.01
Max. rms V orbit @ BPMs 1.5 ± 0.27 0.31 ± 0.004
Average H peak-to-peak 3.8 ± 0.26 1.17 ± 0.02
Average V peak-to-peak 1.8 ± 0.23 0.87 ± 0.02
Corrector strength in mrad
rms max
CH 0.63 ± 0.03 1.88 ± 0.12
CV 0.38 ± 0.013 1.85 ± 0.13
septum 2.27 ± 0.13 5.9 ± 0.3


Table 22: Orbit along the LTB transfer line for modes M1 to M6. For each mode, 100 random machines are simulated with errors given in Table 20. The bold solid curves represent one sigma of the orbit distribution.
TB.V01.M1 Orbit.svg TB.V01.M4 Orbit.svg
TB.V01.M2 Orbit.svg TB.V01.M5 Orbit.svg
TB.V01.M3 Orbit.svg TB.V01.M6 Orbit.svg


LTB Diagnostic Elements

The LTB diagnostics elements are summarized in Table 23.

Table 23: LTB diagnostics elements.
Measurement Probe type Resolution
Bunch waveform (micro & macro bunch) Stripline BPM 1% peak value
Bunch charge ICT 2.0 %
Position Stripline BPM 0.2 mm
Fluorescent screen 0.5 mm
Profile Fluorescent screen 0.5 mm
Energy slit / collimation Beam scraper 0.1 mm


Figure 30: Schematic layout of LTB diagnostic elements.


LTB Horizontal/Vertical Scrapers

A horizontal scraper with a pair of blades will be used in the LTB line as energy slit, to select the portion of the beam coming from the Linac that is within the Booster energy acceptance at injection energy. For this purpose it is installed at a high dispersion and low horizontal betatron function place. An identical scraper will also be installed in the vertical plane, at a high vertical betatron function place, to reduce particle losses at the septum or in the Booster.

Specifications for the LTB horizontal and vertical scrapers are given in Table 24.


Table 24: Specifications for LTB transfer line scrapers.
Quantity of scrapers 2 (1 horizontal + 1 vertical)
Number of blades per scraper * 2
Blade position resolution (transverse) 10 μm
Position accuracy 100 μm
Position repeatability 50 μm
Motion range per blade ** 20 mm
* Blades with independent movement
** Vacuum chamber diameter ∅=36 mm


LTB Beam Position Measurement Stations

Beam position measurement stations combining a stripline BPM and a fluorescent screen will be used in the LTB line to measure the beam position. The specifications for the stripline BPMs are shown in Table 25 and for the fluorescent screens in Table 26.


Table 25: Specifications for LTB transfer line stripline BPMs.
Quantity 6
Dynamic range 50 dB
Alignment accuracy 0.5 mm
Measurement accuracy 0.2 mm
Resolution @ 1 nC 100 μm
Measurement range (radius) ± 5 mm


Table 26: Specifications for LTB transfer line fluorescent screens.
Quantity 6
Spatial resolution (transverse) 0.2 mm
Mechanical positioning accuracy 0.2 mm
Mechanical positioning repeatability 0.1 mm


LTB ICTs

Two Integrating Current Transformers (ICTs) will be installed at the LTB extremities allowing measurements of its transmission efficiency. The first ICT is being purchased as part of the Linac. The specifications for the LTB ICTs are shown in Table 27.


Table 27: Specifications for LTB transfer line ICTs.
Quantity 3 (1 from Linac + 2)
Dynamic range 50 dB
Resolution 2  %
Model ID 34.9 - Bergoz CF4.5"-34.9-40/1.1

Booster to storage ring transport line (BTS)

The main function of the booster-to-storage ring transport line (BTS - with naming initials TS), is to transport the 3.0 GeV electron beam from the booster synchrotron to the storage ring (SR). The geometric requirements for this line are determined by the lattice of the two accelerators located in the same machine tunnel. Since the BTS line traverses the machine tunnel, a long element-free drift section is required to facilitate the passage of people and equipment through this region. To save costs, the BTS line uses the same quadrupoles as the storage ring and same dipoles and correctors as the booster. The booster dipole is scaled to a lower value as compared to the booster peak value, so that it can be set to DC operation without overheating the coils.

A general view of the BTS transport line is shown in Figure 31. A schematic diagram of the BTS elements with their names is shown in Figure 32. The main parameters are shown in Table 28.

Figure 31: Overview of the TS transfer line.
Figure 32: TS transfer line in detail.


Table 28: Main parameters of the BTS transfer line.
Operation energy 3.0 GeV
Lattice version V03
Total length including septa 26.89 m
Number of dipoles 3
Number of quadrupoles 8
Number of horizontal correctors (CH + septa) 4 + 2
Number of vertical correctors 6


BTS Lattice

The BTS lattice is designed with the same magnetic elements of the Booster (dipoles and correctors) and of the Storage Ring (quadrupoles Q14 and Q20). We define the BTS transport line from the Booster extraction septum to the Storage Ring thin injection septum, with both septa included.

The BTS initial optical conditions are matched to the Booster parameters at the extraction point, but the final conditions are mismatched to optimize the injection efficiency into the storage ring with a nonlinear kicker (NLK). The 2 modes M1 and M2 are optimized for different positions of the injected beam at the NLK. Mode M1 assumes the beam is injected at x=-8.0 mm, close to the NLK field maximum, and mode M2 assumes the beam is injected at x=-5.3 mm, where the NLK field has a slope. We expect to inject the beam close to the NLK field maximum, but, for safety, in case the dynamic aperture is not sufficiently large in the beginning, we have studied the possibility of injecting the beam closer to the storage ring axis.

In addition to usual requirements for beam transmission, the BTS transport line optics also requires a free space to allow people and equipment to pass by bending below the beam pipe.

The parameters of the injected beam at the booster extraction point, SR injection point and NLK for the 2 modes are shown in Table 29 and the corresponding optical functions are shown in Table 30.


Table 29: Beam parameters at the booster extraction point and storage ring injection point optimized for injection with NLK.
Booster extraction point Storage Ring injection point NLK
M1 M2 M1 M2
βx 9.321 7.803 11.649 4.0 5.0 m
αx -2.647 0.975 1.305 0.0 0.4
βy 12.881 4.902 4.902 6.66 6.66 m
αy 2.00 0.186 0.186 -0.637 -0.637
ηx 0.231 0.0 0.0 0.0 0.0 m
η'x 0.069 0.0 0.0 0.0 0.0


Table 30: Optical functions along the BTS transfer line for operation modes M1 and M2.
TS twiss M1.svg
TS twiss M2.svg


The considerations for the extracted beam amplitude at the booster extraction septum are described in Table 10, and the considerations for the injected beam aperture at the storage ring injection point (end of thin septum), in Table 31.

Table 10: Booster extraction apertures.
half-aperture for stored beam 18.0 mm
vacuum chamber thickness 1.0 mm
septum thickness 3.3 mm
half-aperture for extracted beam (4σ) 1.0 mm
Total 23.3 mm

Table 31: Storage ring injection apertures.
half-aperture for stored beam 12.0 mm
vacuum chamber thickness 1.0 mm
septum thickness 3.35 mm
half-aperture for injected beam (4σ) 1.0 mm
Total 17.35 mm

BTS Beam Size and Aperture Requirement

The figures below show the horizontal and vertical beam sizes along BTS for the modes M1 and M2.

Figure 33: Horizontal beam size along the BTS transfer line for modes M1 and M2 assuming the booster parameters for emittance, ε=3.47 nm.rad, energy spread, σε=0.087%, and emittance coupling, κ=1%.
Figure 34: Vertical beam size along the BTS transfer line for modes M1 and M2 assuming the booster parameters for emittance, ε=3.47 nm.rad, energy spread, σε=0.087%, and emittance coupling, κ=1%.


The aperture requirements and beam stay clear (BSC) for the BTS transport line are calculated considering a clearance for residual orbit distortion and trajectory variations due to pulse to pulse differences in beam energy and launching conditions (position and angle) as described in Table 32.

Table 32: Parameters for BTS transfer line aperture and BSC calculations.
Max. orbit distortion along LTB (H and V) ± 1 mm
Booster pulse to pulse energy variation 0.1  %
Booster pulse to pulse beam centroid position/angle variation (H and V) 0.4 nm.rad
BTS vacuum chamber inner aperture (full) at quadrupoles (H / V) 23.4 / 23.4 mm
BTS vacuum chamber inner aperture (full) at dipoles (H / V) 23.4 / 23.4 mm


The calculated horizontal and vertical BSC for BTS transport line modes are shown in the figures below.

Figure 35: Horizontal beam stay clear (BSC) for BTS transfer line. The BSC can accommodate residual orbit distortion and trajectory variations due to pulse to pulse differences in beam launching conditions described in Table 32. The vacuum chamber inner half-aperture is represented by the solid black curve.
Figure 36: Vertical beam stay clear (BSC) for BTS transfer line. The BSC can accommodate residual orbit distortion and trajectory variations due to pulse to pulse differences in beam launching conditions described in Table 32. The vacuum chamber inner half-aperture is represented by the solid black curve.

BTS Orbit Correction

The BTS transport line orbit correction main parameters are shown in Table 33. The specification of error tolerances takes into consideration the maximum Booster corrector strength at 3 GeV, since the same correctors are used. The tolerances are shown in Table 34 and the correction statistics in Table 35. The orbits before and after correction for all modes are shown in Table 36. The correction system uses the same beam position measurement station with integrated fluorescent screens and striplines. The Booster extraction septum is used as a horizontal corrector as well as the storage ring injection septa, that are used to adjust horizontal position and angle at the storage ring injection point.


Table 33: Parameters for BTS transfer line orbit correction.
Number of beam position measurement stations 5
Number of horizontal correctors 4
Number of septa used as horizontal corrector 2
Number of vertical correctors 6
Maximum corrector strength ±0.35 mrad


Table 34: Maximum absolute random errors for BTS transfer line orbit correction simulation. A Gaussian distribution with cutoff in ±1σ is assumed.
Magnets
X alignment 0.16 mm
Y alignment 0.16 mm
Roll angle 0.5 mrad
Relative field error 0.1  %
BPMs
X alignment 0.2 mm
Y alignment 0.2 mm
Beam launching conditions
x 0.2 mm
θx 0.1 mrad
y 0.2 mm
θy 0.1 mrad
dp/p 0.2  %

Table 35: Orbit correction statistics over 100 random seeds for BTS transfer line.
Orbit in mm
before after
Max. rms H orbit 0.86 0.17
Max. rms V orbit 0.92 0.18
Max. rms H orbit @ BPMs 0.79 0.11
Max. rms V orbit @ BPMs 0.78 0.12
Average H peak-to-peak 1.4 0.4
Average V peak-to-peak 1.4 0.4
Corrector strength in mrad
rms max
CH 0.10 0.37
CV 0.10 0.29
septa 0.20 0.54


Table 36: Orbit along the BTS transfer line for modes M1 and M2. For each mode, 100 random machines are simulated with errors given in Table 34. The bold solid curves represent one sigma of the orbit distribution.
TS.V02.M1 Orbit.svg TS.V02.M2 Orbit.svg


BTS Diagnostics Elements

Figure 37: Schematic layout of BTS diagnostic elements.




Injection into the Storage Ring

The injection point in the storage ring is, by definition, the physical end of the thin septum.

Figure 38: Layout of the storage ring injection straight section.
Figure 39: Schematic representation of the transverse cross section at the storage ring injection point.

Injection with Nonlinear Kicker (InjNLKckr)

Figure 40: Injection into the storage ring using a Nonlinear Kicker. The trajectory of the injected beam centroid in the horizontal plane is shown in solid red curve. The dashed curves represent ±3σx beam envelope.
Figure 41: Phase space at the Pulsed Multipole Magnet (PMM) position. The green curve represents the injected beam (±4σx) inside the storage ring acceptance (red curve) after the PMM non-linear kick. The black curve is plotted against the right axis and represents the magnetic field of the PMM.

On-axis injection (InjDpKckr)

Figure 42: On-axis injection into the storage ring with a on-axis dipole kicker. The trajectory of the injected beam centroid in the horizontal plane is shown in solid red curve. The dashed curves represent ±3σx beam envelope.


Pulsed Magnets Parameters

General layout

Figure 43: Booster injection section layout.


Figure 44: Booster extraction layout.


Figure 45: Layout of the storage ring injection straight section.


Septa

Table:Septa parameters

Table 37: Main parameters for Sirius septa.
Septum Booster Storage Ring
Injection Extraction Thin Extraction Thick Injection Thick Injection Thin
Number 1 1 1 2 1
Arc length 0.500 0.577 0.577 0.577 0.500 m
Nominal deflection +21.75 -3.60 -3.60 +3.60 +3.12 °
+379.61 -62.83 -62.83 +62.83 +54.42 mrad
Maximum deflection 400.0 68.0 68.0 60.0 60.0 mrad
Nominal magnetic field 0.380 -1.089 -1.089 1.089 1.089 T
Nominal beam trajectory radius 1.317 -9.188 -9.188 9.188 9.188 m
Magnet shape radius 1.350 -12.500 12.500 12.500 12.500 m
Sagitta 23.7 4.5 4.5 4.5 3.4 mm
Horizontal Beam Stay Clear (full) 22 ≥ 9 ≥ 9 ≥ 9 ≥ 9 mm
Vertical Beam Stay Clear (full) ≥ 16 ≥ 8 ≥ 8 ≥ 7 ≥ 7 mm
Septum thickness 3 3 3 2.5 2.5 mm
Amplitude reproducibility (rms) ≤ 0.07 ≤ 0.006 ≤ 0.006 ≤ 0.017 ≤ 0.017  %
Flat top (rms) ≤ 0.07 ≤ 0.006 ≤ 0.006 ≤ 0.017 ≤ 0.017  %
Flat top width 150 150 150 150 150 ns
Minimum half-sine pulse duration to satisfy flat-top ≥ 6.2 ≥ 21 ≥ 21 ≥ 12.6 ≥ 12.6 μs
Integrated leak field ≤ 50 ≤ 200 ≤ 200 ≤ 3.7 ≤ 3.7 G.cm

See Booster extraction apertures and SI injection apertures.

Kickers

Table:Kickers parameters

Table 38: Main parameters for Sirius kickers.
Kicker Booster Storage Ring
Injection Extraction DpKckr (On-axis) NLKckr
Beam energy 0.15 3.0 3.0 3.0 GeV
Number 1 1 1 1
Length 0.5 0.5 0.5 0.47 m
Nominal deflection 19.34 2.52 6.1 2.9 (@x=-8 mm) mrad
Maximum deflection 23.4 2.9 6.7 3.4 (@x=-6 mm) mrad
Nominal integrated field 0.010 0.025 0.061 0.029 (@x=-8 mm) T.m
Maximum integrated field 0.012 0.029 0.067 0.034 (@x=-6 mm) T.m
Horizontal Beam Stay Clear (full) ≥ 36 ≥ 36 ≥ 24 ≥ 24 mm
Vertical Beam Stay Clear (full) ≥ 15 ≥ 15 ≥ 9 ≥ 9 mm
Amplitude reproducibility (rms) ≤ 0.31 ≤ 0.37 ≤ 0.33 ≤ 0.7  %
Flat top (peak-to-peak) ≤ 0.62 ≤ 0.74 ≤ 0.66 ≤ 1.4  %
Flat top width 150 150 150 150 ns
Rise time - ≤ 1.5 - - μs
Fall time ≤ 1.5 - ≤ 1.5 ≤ 1.5 μs
Minimum half-sine pulse duration to satisfy flat-top ≥ 3.0 ≥ 2.7 ≥ 2.9 ≥ 2.0 μs
Tolerance for integrated dipole field at center 1 - - - < 3.7 G.cm
Tolerance for integrated quadrupole gradient at center 2 - - - < 0.12 T

1 For horizontal stored beam centroid oscillation < 10% of beam size.

2 For horizontal stored beam size oscillation < 10%.

Assumptions for aperture requirements and tolerance calculations

Aperture requirements

Table:Pulsed Magnets aperture requirement

Table 39: Beam aperture requirement considerations for Sirius septa.
Septum Booster Injection Booster Extraction Storage Ring Injection
Horizontal Vertical Horizontal Vertical Horizontal Vertical
beam size, ±3σ mm ±6.3 ±4.0 ±1.0 ±1.0 ±1.0 ±0.5
orbit distortion mm ±1.0 ±1.0 ±1.5 ±1.0 ±1.5 ±1.0
tolerance for vacuum chamber mm ±1.0 ±1.0 ±1.0 ±1.0 ±1.0 ±1.0
position/angle variation mm ±2.0 ±2.0 ±1.0 ±1.0 ±1.0 ±1.0
energy variation mm ±0.7 - - - - -
Total mm ±11.0 ±8.0 ±4.5 ±4.0 ±4.5 ±3.5
Total Full Size mm 22 16.0 9.0 8.0 9.0 7.0

Flat-top and pulse-to-pulse reproducibility

The requirements for the 3 GeV kickers and septa flat-top and pulse-to-pulse reproducibility were determined based on the NLK injection efficiency in the storage ring. The injected beam position and angle stability at the NLK are required to be within Δx < 150 μm and Δx' < 50 μrad. Random variations in the injected beam position and angle at the NLK are supposed to be caused by uncorrelated random variations in:

1) Booster extraction kickers

2) Booster extraction septa

3) Storage ring thick injection septum

4) Storage ring thin injection septum

5) Storage ring NLKckr

6) BTS transport line magnet vibrations and ripple

If we suppose these effects add in quadrature and have the same weight, the tolerance for each contribution becomes:

Δx < 60 μm and Δx' < 20 μrad

1) Booster extraction kickers (bek): A variation in the bek kick (same kick in both kickers) affects the position and angle at the NLK according to:

Δx [mm] = 11.1 Δθbek[mrad]    and     Δx' = 3.4 Δθbek   ,   thus
Δθbek < 5.4 μrad    or    Δθbekbek < 0.3%

2) Booster extraction septa (bes): A variation in the bes kick (same kick in both septa) affects the position and angle at the NLK according to:

Δx [mm] = 13.9 Δθbes[mrad]    and     Δx' = 0.5 Δθbes   ,   thus
Δθbes < 4.3 μrad    or    Δθbesbes < 0.006%

3) Storage ring thick injection septum (stk): A variation in the stk kick affects the position and angle at the NLK according to:

Δx [mm] = 5.3 Δθstk[mrad]    and     Δx' = Δθstk   ,   thus
Δθstk < 11.4 μrad    or    Δθstkstk < 0.01%

4) Storage ring thin injection septum (stn): A variation in the stn kick affects the position and angle at the NLK according to:

Δx [mm] = 3.7 Δθstn[mrad]    and     Δx' = Δθstn   ,   thus
Δθstn < 16.2 μrad    or    Δθstnstn < 0.019%

5) Storage ring NLKckr (pmm):

Δθpmm < 20 μrad    or    Δθpmmpmm < 0.7%


For the other pulsed magnets:

1) Storage ring on-axis injection kicker (sik): The tolerance is calculated by requiring that the injected beam oscillation amplitude be limited to Δxmax < 0.5 mm along the storage ring horizontal plane. The trajectory of the electron beam after a residual kick at sik is:

Δx(s) = Δθsikx,sik βx(s)]1/2 sin(Δφ)

Δxmax is limited if

Δθsik < Δxmax / [βx,sik βx,max]1/2

Using βx,sik=18.6 m and βx,max=19.3 m, we have

Δθsik < 26.4 μrad    or    Δθsiksik < 0.33 %


2) Booster on-axis injection kicker (bik): The tolerance can be calculated in a similar way, by requiring that the injected beam oscillation amplitude be limited to Δxmax < 1.5 mm along the booster horizontal plane. When specifying the booster aperture, an allowance of 4.5 mm was considered for beam oscillations after injection. For the booster βx,bik=17.9 m and βx,max=23.2 m, so we have

Δθbik < 0.074 mrad    or    Δθbikbik < 0.31 %


3) Booster injection septum (bis): A variation in the bis kick affects the position and angle at the injection kicker (bik) according to:

Δx [mm] = 1.85 Δθbis[mrad]    and     Δx' = 0.2 Δθbis   ,

if we require Δx < 0.5 mm at the booster injection kicker, we have:

Δθbis < 0.27 mrad    or    Δθbisbis < 0.07%

Leakage field

To calculate the allowed storage ring injection septa leakage field at the stored beam position in the storage ring, we have assumed that the oscillations caused by the perturbation be limited to 10% of the beam size. The beam trajectory after a kick is given by:

Δx(s) = Δθ00β(s)]1/2 sin[φ(s)-φ0] < 0.1 σx(s) = 0.1 [εx β(s)]1/2

and as a worst-case estimate we take sin[φ(s)-φ0]=1, and the residual kick at the stored beam position should satisfy:

Δθ0 < 0.1 [εx0]1/2
for εx=0.27 nm.rad and β0=20 m, we have Δθ0 < 0.37 μrad, or ∫B.dl < 3.7 G.cm at E = 3 GeV.


For the booster extraction septum, we set the allowed leakage field so that the orbit distortion amplitude is limited to 0.3 mm.

Δx(s) = Δθ00β(s)]1/2 sin[φ(s)-φ0] < 0.3 mm   ,   then
for βx,max=23.2 m and β0=9.2 m, we have Δθ0 < 20 μrad, or ∫B.dl < 200 G.cm at E = 3 GeV.


For the booster injection septum, we set the allowed leakage field so that the orbit distortion amplitude is limited to 1.5 mm.

Δx(s) = Δθ00β(s)]1/2 sin[φ(s)-φ0] < 1.5 mm   ,   then
for βx,max=23.2 m and β0=9.2 m, we have Δθ0 < 0.1 mrad, or ∫B.dl < 50 G.cm at E = 150 MeV.


Half-sine pulse duration

If we define the pulse amplitude by

A = A0 cos(π t/T)

then the half-sine pulse duration T required for a flat-top dA/A0 in the time range 2t0 << T is given by

T = π t0 * (2 dA/A0)-1/2
Figure 46: Septum pulse.