Yujong Kim
PSI, CH-5232 Villigen PSI, Switzerland
[email protected], http://www.PSI.ch/~kim_y, http://FEL.WEB.PSI.ch PSI XFEL-2009-46
Stability Issues for the Coherent Single Spike
Mode Operation with Ultra-Low Charges
500 m
Altitude curves: 10 m
0 100 200 300 400
PSI - West
SLS
PSI - East
Access roadtunnel
linac
undulator hall+ beam dump
userarea
photontransport
250 MeV Injectortest area
Tunnel entry + Injector area
Aare
N
Workshop on X-ray Science at Femtosecond to Attosecond Frontier, UCLA, May 18, 2009
Electron Beam Generation and
2
Outline
Introduction to the PSI-XFEL Project
Site Limitation
Required Beam Parameters
Optimized Injector for Various Single Bunch Charges
Design Concepts & Summary of 13 Optimized Linac Layouts
Optimized Linac Layouts for Nominal Operations at 0.1 nm with 200 pC
Optimized Linac Layout for Single Spike Operation at 0.1 nm with 2 pC
Optimized Linac Layout for Single Spike Operation at 1 nm with 10 pC
RF Jitter Sensitivities and Tolerances for 10 pC Operation
Overall FEL Stability & Performance under RF Errors
300 Times S2E Simulation Results for 10 pC with required RF Jitter Tolerances
300 Times S2E Simulation Results for 2 pC with loose RF Jitter Tolerances
300 Times S2E Simulation Results for 2 pC with tighter RF Jitter Tolerances
Summary & Acknowledgements
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
33500 m
Altitude curves: 10 m
0 100 200 300 400
PSI - West
SLS
PSI - East
Access roadtunnel
linac
undulator hall+ beam dump
userarea
photontransport
250 MeV Injectortest area
Tunnel entry + Injector area
Aare
N
LEG Test Facility
PSI-XFEL Facility
2008-2011 : 250 MeV Injector Test Facility - Commissioning will be started in October, 2009
2011-2016 : RF Gun + Short Linac + Cryo (?) In-Vacuum Undulator based 5.8 GeV PSI-XFEL Facility
PSI-XFEL - Limited Site
Low Emittance Gun based PSI-XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
PSI - West
total available length < 950 m
total available length for linac < 540 m
no way, it should be compact !
4
PSI-XFEL - Required Beam Parameters
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
required or expected parametersnominal operation mode upgrade operation mode
long pulse short pulse ultra-short pulse
single bunch charge (pC) 200 10 10
required max core slice emittance (µm) 0.43 / 0.38 0.18 0.25
required max rms slice energy spread (keV) 350 / 250 250 1000
required min peak current at undulator (kA) 2.7 / 1.6 0.7 7
required min beam energy for 1 Å (GeV) 5.8 5.8 5.8
required max saturation length† (m) 50 50 50
expected max bunch compression factor 125 / 75 240 2400
expected max projected emittance (µm) 0.65 0.25 0.45
expected rms photon pulse length at 1 Å (fs) 12 2.1 0.3
expected number of photon at 1 Å (×109) 24 1 4
expected bandwidth (%) 0.031 0.025 0.050
†assumed undulator parameters: K = 1.2, λu = 15 mm, <β> = 15 m, length ~ 70 m
Parameters for the PSI-XFEL Project to generate XFEL Photon beams at 1 Å
Gsat
Gsat LEe
PLL 20ln
34
uGL 2~/
3/122
22
1
4
1
K
I
I
n
u
A
pk
)/exp( Go LzPP ]cm[]T[934.0,2
12
2
2 uou BK
K
higher ρ shorter LG
5555
PSI-XFEL - 250 MeV Injector Test Facility
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
CTF3 RF GUN
RF tested @ 100 MV/m - two weeks operation at CERN
power for 100 MV/m = 22 MW with 4.5 s RF pulse
power for 120 MV/m = 25 MW
RF frequency ~ 2998.5 MHz
cell = 2.5 cells (One TM02 + Two TM01)
Q0 = 16300
number of bunch in a train = 48
cathode wall angle = 20 degree
total length ~ 0.25 m
full cell length ~ 50 mm
designed charge ~ 2.33 nC for CTF3
bucking solenoid main solenoid
6666
PSI-XFEL - 250 MeV Injector Test Facility
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
Parameters 10 pC 100 pC 200 pC
laser diameter on cathode 400 µm 857 µm 1080 µm
laser pulse length (FWHM) 3.7 ps 7.9 ps 9.9 ps
peak current on cathode 3 A 14 A 22 A
thermal emittance on cathode 0.072 µm 0.155 µm 0.195 µm
core slice emittance before / after BC 0.078 µm / 0.078 µm 0.213 µm / 0.213 µm 0.320 µm / 0.330 µm
projected emittance before BC 0.095 µm 0.233 µm 0.350 µm
bunch length before BC (rms) 1.05 ps 2.23 ps 2.80 ps
bunch length after BC (rms) 33.2 fs 117.6 fs 193.3 fs
peak current after BC 104 A 285 A 352 A
x / y projected emittance after BC 0.104 µm / 0.096 µm 0.268 µm / 0.233 µm 0.379 µm / 0.350 µm
arrival error for stable seeding at ~ 160 nm ~ 5.5 fs ~ 19.6 fs ~ 32.2 fs
min beam size on OTRs in 3FODO (rms) ~ 14 µm ~ 35 µm ~ 55 µm
7777
PSI-XFEL - 250 MeV Injector Test Facility
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
Commissioning of 250 MeV Injector Test Facility will be started in October 2009
D. Dowell calculated
thermal emittance
line (0.5 μm/mm)
P. Emma, XFEL2008 Workshop, Courtesy of D. Dowell
PSI LEG
Measurement
0.61 µm/mm
LCLS Measured Core Slice Emittance
CTF3 Simulation
0.72 µm/mm
Euro. LCLS Simulation
0.91 µm/mm
8
PSI-XFEL - Used Thermal Emittance
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
LCLS Core Slice Emittance Measurements:Q = 20 pC, E ~ 135 MeV
Method = QM scan with LOLA
E = 135 MeV
Q = 20 pC
Ecathode ~ 115 MV/m
laser = 253 nm (= 4.899 eV)
ΔTlaser ~ 3.8 ps (FWHM)
Laser profile = pseudo-Gaussian shape
ζz ~ 1.3 ps
Ipeak ~ 5 A
)(0.5
eV,)V/m(107947.3 ~
beamroundaforσσ,3
σε
schottky0ave
5
schottky
2
schottky0
,th
hK
E
cm
hyx
e
yx
Kave = 0.4 eV was used for our
CTF3 RF gun based injector
optimizations !
Kave = 0.63 eV was used for our
European LCLS RF gun based
injector optimization !
2
e
ave,th
3
2σε
cm
Kyx
9
PSI-XFEL - Optimized Injector for 2 pC
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
CTF3 RF Gun may generate an ultra-low emittance < 0.06 µm for 2 pC !
1010
PSI-XFEL - Optimized Injector for 2 pC
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
CTF3 RF Gun may generate an ultra-low emittance < 0.06 µm for 2 pC !
for 2 pC, slice & projected emittances ~ εth = 0.042 µm
εnsc contribution to εslice is ignorable !
εprojected = 0.054 µm εslice = 0.044 µm
INSB01-RAC INSB02-RACGUN
Projected Emittance along Injector Slice Emittance at 172 MeV
After considering targeting slice emittance (~ 0.18 µm) at the end of linac,
we chose thermal emittance ~ 0.072 µm & a low peak current of 3 A at the cathode.111111
PSI-XFEL - Optimized Injector for 10 pC
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
CTF3 RF Gun may generate a low emittance < 0.1 µm for 10 pC !
ASTRA Simulation Results with Space Charge
Projected Emittance along Injector
121212
PSI-XFEL - Optimized Injector for 10 pC
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
Q = 10 pC
E = 167.654 MeV, = 0.021%
x= 105 m, y= 105 m, z = 316 m
nx= 0.095 m, ny= 0.095 m
Ipeak ~ 3 A, n,core,slice ~ 0.078 m
Excellent Projected & Slice Emittance !
Excellent Uniformity in Current Profile !
Better Twiss Mismatching Parameter !
Excellent Slice Emittance !
And Wide Uniform Range !
Slice Emittance at 167 MeV
INSB01-RAC INSB02-RAC
Good Invariant Envelope Matching !
Emittance Damping in Booster Linac !
Mismatching Parameter ζ at 167 MeV
GUN
131313
PSI-XFEL - Summary of Optimized Injector
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
Final beam parameters are at the exit of the 2nd S-band structure (130 MeV - 172 MeV).
Gun max gradient = 100 MV/m, assumed Kave = 0.4 eV.
For only Q 2 pC, εprojected εslice εthermal
For a much higher Q, εprojected εslice εthermal due to the nonlinear space charge force.
We can get an excellent emittance with a lower charge for the single spike mode operation!
ASTRA Simulation Results : CTF3 RF Gun based Injector for various Charges
Q laser length (FWHM) Ipeak, cathode laser ζx,or y εthermal εslice/εprojected
200 pC 9.9 ps 22 A 270 µm 0.195 µm 0.320/0.350 µm
150 pC 9.0 ps 18 A 245 µm 0.177 µm 0.272/0.283 µm
100 pC 7.9 ps 14 A 214 µm 0.155 µm 0.220/0.233 µm
50 pC 6.2 ps 8.7 A 170 µm 0.123 µm 0.160/0.174 µm
20 pC 4.6 ps 4.7 A 125 µm 0.091 µm 0.108/0.122 µm
10 pC 3.7 ps 3.0 A 100 µm 0.072 µm 0.080/0.096 µm
5 pC 2.9 ps 1.9 A 79 µm 0.057 µm 0.062/0.074 µm
2 pC 2.1 ps 1.0 A 58 µm 0.042 µm 0.044/0.054 µm
14
PSI-XFEL - Linac Design Concepts
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
Generate high quality electron beams to keep the saturation length smaller
than 50 m for 1 Å.
Keep length of whole linac as short as possible due to a bridge at 544 m.
To minimize space charge effects and COTR, avoid a dog-leg or BC1 at a low
energy (BC1 @ ~ 450 MeV, no dog-leg, no strong beam waist before BC1).
To minimize CSR, keep somewhat high energy spreads at BCs for weak strength
chicanes but keep ζδ ≤ 1.7% @ BC1 ≤ 0.55% @ BC2 to avoid chromatic effects.
Module type diagnostic sections to measure beam parameters without change optics.
To reduce the bandwidth of XFEL photon beams, keep a small energy chirp and
energy spread at the end of linac as small as possible (C-band linac is promising!)
By choosing weak strength QMs and by keeping small beta-functions and somewhat
low phase advances in FODO cells, minimize chromatic effects in whole linac.
To avoid too tight RF jitter tolerances, choose the near on-crest RF phases and
smaller bunch length compression factors if possible.
For single spike mode with 2 pC and 10 pC, make a short bunch to satisfy:
z 2×cooperation length
1515Low Emittance Gun based PSI-XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
PSI-XFEL - Efforts on Chirp & Bandwidth
Optimization-V
chirp for Ipk = 2.7 kA
Optimization-III, VI, VII
chirp for Ipk = 1.6 kA
wavelength = 0.1 nm @ FEL1
no of photon per pulse ~ 1.0×1011
saturation length ~ 40 m with 2.7 kA
saturation length ~ 48 m with 1.6 kA
From our recent full S2E simulations with ASTRA, ELEGANT, and GENESIS codes
(Y. Kim and S. Reiche), we confirmed that we can effectively minimize the bandwidth
of XFEL photon beams by optimizing energy chirping of electron beams.
BW ~ 0.05% for Ipk = 1.6 kABW ~ 0.1% for Ipk = 2.7 kA
Optimization-III & V
S-band based Linacs
Linac Length = 650 m
Optimization-VI & VII
C-band based Linacs
Linac Length = 540 m, 510 mSaturation Length < 50 m !!!
1717
PSI-XFEL - Several Optimized Layouts
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
Optimization-III with a longer S-band RF Linacs for Chirp Compensation
ASTRA up to exit of SB02 & ELEGANT from exit of SB02 to consider space chare, CSR, ISR, and wakefields !
Optimization-I with S-band RF Linacs
1818Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
Optimization-VI with S-band & C-band RF Linacs for Chirp Compensation
ASTRA up to exit of SB02 & ELEGANT from exit of SB02 to consider space chare, CSR, ISR, and wakefields !
Optimization-V with S-band RF Linacs
PSI-XFEL - Several Optimized Layouts
1919Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
ASTRA up to exit of SB02 & ELEGANT from exit of SB02 to consider space chare, CSR, ISR, and wakefields !
Optimization-VIII with New Injector for 2 pC Single Spike Mode
New Injector Layout with Laser Heater & BC1 @ ~ 450 MeV
PSI-XFEL - Several Optimized Layouts
Optimization-VII with Shortest C-band RF Linacs for Chirp Compensation
2020Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
ASTRA up to exit of SB02 & ELEGANT from exit of SB02 to consider space chare, CSR, ISR, and wakefields !
Optimization-IX with X-band Linac for Chirp Compensation
Optimization-X with New Injector for 10 pC Nominal Mode
New Injector Layout with Laser Heater & BC1 @ ~ 450 MeV
PSI-XFEL - Several Optimized Layouts
212121Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
New Injector Layout with Laser Heater & BC1 @ ~ 450 MeV
Optimization-XI with New Injector for 10 pC Single Spike Mode
single spike mode at 0.1 nm with 2 pC
rms bunch length ~ 0.43 fs @ 5.8 GeV
Optimization-VIII
photon
rms BW ~ 0.2%
rms pulse length ~ 140 as @ 0.1 nm
peak power ~ 19 GW
photons : 3.3e9
single spike mode at 1 nm with 10 pC
rms bunch lenght ~ 2.4 fs @ 3.4 GeV
Optimization-XI
photon
rms BW ~ 0.67%
rms pulse length ~ 280 as @ 1 nm
peak power ~ 10 GW
photons = 1.1e10
PSI-XFEL - Optimized Layouts
See details from Sven's talk later
222222Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
10 pC - Investigation of Jitter Sensitivity
ASTRA & ELEGANT codes + Ming Xie Model were used to consider space charge,
CSR, ISR, short-range wakefield, and performance of XFEL.
We assumed that orbit feedback is running even though there are errors in linac.
By applying an artificial error set to single linac component and looking into FEL
performance from Ming Xie Model at the entrance of undulator, we checked
the impact of the error on FEL performance (sensitivity of the error).
To determine tolerances, we used FEL performance instead of linac performance.
S03 X01 BC1 LINAC1 BC2 LINAC2 3.4 GeV for 1 nm with 10 pC
232323Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
10 pC - Criteria of Jitter Tolerance
To determine error tolerances for the single spike mode operation with 10 pC, at the
entrance of undulator (3.4 GeV), following FEL performance should be satisfied
when there is an error in a single machine component:
beam arrival time error Tarrival 5 fs (zero-to-max) ~ electron bunch length order.
saturation power error Psat/Psat 100% (zero-to-max) against any optics damage.
wavelength error / 0.01% (zero-to-max) against intensity lowering due to collimator.
saturation length error Lsat/Lsat 15% (zero-to-max) to get saturation with a given
undulator length (undulator length margin ~ 30-40%).
Please note that in rms (~ zero-to-max/3.0), they are about:
Tarrival 1.7 fs (rms), tighter than European XFEL (12 fs) due to a shorter bunch.
Psat/Psat 33% (rms), looser than European XFEL (5%)
/ 0.003% (rms), tighter than European XFEL (0.007%) due to smaller photons
Lsat/Lsat 5% (rms), looser than European XFEL (0.5%)
242424Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
10 pC - Ultra-Sensitive Jitter Sources
FEL power change due to 10 X-band RF phase errors peak current fluctuation due to 10 X-band RF phase errors
error source : X-band (X01) RF phase
error range : -0.06 deg to +0.06 deg with10 steps
monitoring point : at the entrance of undulator @ 3.4 GeV
For Psat/Psat 100% (zero-to-max), X-band RF phase error 0.002 deg (rms)
This X-band RF phase tolerance is challenging !
X-band RF phase error, single bunch charge error, and injector S-band RF phase errors are
sensitive jitter sources to FEL saturation power.
wavelength ~ 1 nm
energy ~ 3.4 GeV
undulator period = 40 mm
beta-function ~ 10 m
K ~ 1.6
252525Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
10 pC - Ultra-Sensitive Jitter Sources
saturation length change due to 10 timing errors peak current fluctuation due to 10 timing errors
error source : gun & laser synchronization timing
error range : -50 fs to +50 fs with10 steps
monitoring point : at the entrance of undulator @ 3.4 GeV
For Lsat/Lsat 15% (zero-to-max), gun timing jitter 1 fs (rms).
This gun timing jitter tolerance is challenging !
wavelength ~ 1 nm
energy ~ 3.4 GeV
undulator period = 40 mm
beta-function ~ 10 m
K ~ 1.6
gun timing error, X-band RF phase error, and injector S-band RF phase errors are sensitive
jitter sources to FEL saturation length.
262626Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
10 pC - Ultra-Sensitive Jitter Sources
arrival time change due to 10 S-band voltage errors arrival time fluctuation due to 10 S-band voltage errors
error source : RF voltage of S-band linac (S03) in injector
error range : -0.10% to +0.10% with10 steps
monitoring point : at the entrance of undulator @ 3.4 GeV
For Tarrival 5 fs (zero-to-max), S-band RF voltage error 0.005% (rms).
This S-band RF voltage tolerance is challenging !
~ 60 fs
BC1 chicane power supply error, gun timing error, injector S-band RF voltage and phase
errors are sensitive jitter sources to photon beam arrival time.
272727Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
10 pC - Ultra-Sensitive Jitter Sources
wavelength change due to 10 S-band phase errors long. phase space & peak current fluctuation due to errors
error source : RF phase of S-band linac (S03) in injector
error range : -0.06 deg to +0.06 deg with10 steps
monitoring point : at the entrance of undulator @ 3.4 GeV
For / 0.01% (zero-to-max), S-band RF phase error 0.005 deg (rms).
This S-band RF phase tolerance is challenging !
~ 30 fs
injector S-band RF phase errors and LINAC1 RF phase and voltage errors, and LINAC2 RF
phase and voltage errors are sensitive jitter sources to photon beam wavelength.
wavelength ~ 1 nm
energy ~ 3.4 GeV
undulator period = 40 mm
beta-function ~ 10 m
K ~ 1.6
282828282828
10 pC - Summary of Tolerances
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
parameters tolerance (rms) tolerance source
gun laser arrival timing error ≤ 1 fs (rms) saturation length, arrival time
single bunch charge error ≤ 1% (rms) saturation power
injector S-band RF phase error ≤ 0.005 deg (rms) power, wavelength, arrival time
injector S-band RF voltage error ≤ 0.005% (rms) arrival time
injector X-band RF phase error ≤ 0.002 deg (rms) power, saturation length
injector X-band RF voltage error ≤ 0.011% (rms) arrival time
BC1 dipole power supply error ≤ 7.5 ppm (rms) arrival time
LINAC1 S-band RF phase error per klystron ≤ 0.015 deg (rms) wavelength, power
LINAC1 S-band RF voltage error per klystron ≤ 0.010% (rms) wavelength, arrival time
BC2 dipole power supply error ≤ 7.5 ppm (rms) arrival time
LINAC2 S-band RF phase error per klystron ≤ 0.017 deg (rms) wavelength
LINAC2 S-band RF voltage error per klystron ≤ 0.011% (rms) wavelength
These are tolerances for the single spike mode at 1 nm with 10 pC.
Tolerances of the single spike mode at 0.1 nm with 2 pC are much tighter than these things !
Tolerance Criteria for Single Component Error
Tarrival 1.7 fs (rms)
Psat/Psat 33% (rms)
/ 0.003% (rms)
Lsat/Lsat 5% (rms)
292929292929
10 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
gun timing error ≤ 1 fs (rms)
bunch charge error ≤ 1% (rms)
injector S-band RF phase error ≤ 0.005 deg (rms)
injector S-band RF voltage error ≤ 0.005% (rms)
injector X-band RF phase error ≤ 0.002 deg (rms)
injector X-band RF voltage error ≤ 0.011% (rms)
BC1 & BC2 dipole power supply error ≤ 7.5 ppm (rms)
LINAC1 S-band RF phase error per klystron ≤ 0.015 deg (rms)
LINAC1 S-band RF voltage error per klystron ≤ 0.010% (rms)
LINAC2 S-band RF phase error per klystron ≤ 0.017 deg (rms)
LINAC2 S-band RF voltage error per klystron ≤ 0.011% (rms)
To see overall FEL Performance under various errors, we performed 300 times S2E
simulation with following random Gaussian errors (3 cut). Here, we considered all
collective effects such as space charge, CSR, ISR, and short-range wakefields.
Required Tolerances for 10 pC
303030303030
10 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
median : ~ 1.0 µs
rms variation : ~ 5.5 fs
median : ~ 83 GW (80% core slices)
rms variation : ~ 86%
still some fluctuation when we include
all errors together!
median : ~ 20 m
rms variation : ~ 4.5%
median : ~ 1 nm
rms variation : ~ 0.006%
313131313131
10 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
median : ~ 3.4 GeV
rms variation : ~ 0.003%
median : ~ 0.69 µm
rms variation : ~ 6.5%
median : ~ 0.109 µm
rms variation : ~ 3%
median : ~ 9.1e4
rms variaiton : ~ 2.1e-4%
323232323232
2 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
gun timing error ≤ 10 fs (rms)
bunch charge error ≤ 0.5% (rms)
injector S-band RF phase error ≤ 0.02 deg (rms)
injector S-band RF voltage error ≤ 0.02% (rms)
injector X-band RF phase error ≤ 0.04 deg (rms)
injector X-band RF voltage error ≤ 0.04% (rms)
BC1 & BC2 dipole power supply error ≤ 10.0 ppm (rms)
LINAC1 S-band RF phase error per klystron ≤ 0.02 deg (rms)
LINAC1 S-band RF voltage error per klystron ≤ 0.02% (rms)
LINAC2 S-band RF phase error per klystron ≤ 0.02 deg (rms)
LINAC2 S-band RF voltage error per klystron ≤ 0.02% (rms)
Note that tolerances above are better than current LCLS situation (phase ~ 0.04 deg, dV/V ~ 0.04%) in S-band.
For 0.1 nm with 2 pC, if tolerances is loose, operation becomes really unstable:
S03 X01 BC1 LINAC1 BC2 LINAC2 5.8 GeV for 0.1 nm with 2 pC
Loose Tolerances for 2 pC
3333333333
2 pC - Dancing Longitudinal Phase Space
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
very dynamic peak current & slice parameters!
gun timing error ≤ 10 fs (rms)
bunch charge error ≤ 0.5% (rms)
injector S-band RF phase error ≤ 0.02 deg (rms)
injector S-band RF voltage error ≤ 0.02% (rms)
injector X-band RF phase error ≤ 0.04 deg (rms)
injector X-band RF voltage error ≤ 0.04% (rms)
BC1 & BC2 dipole power supply error ≤ 10.0 ppm (rms)
LINAC1 S-band RF phase error per klystron ≤ 0.02 deg (rms)
LINAC1 S-band RF voltage error per klystron ≤ 0.02% (rms)
LINAC2 S-band RF phase error per klystron ≤ 0.02 deg (rms)
LINAC2 S-band RF voltage error per klystron ≤ 0.02% (rms)
For 0.1 nm with 2 pC, if tolerances is loose, operation becomes really unstable:
Loose Tolerances for 2 pC
under loose tolerances for 2 pC, we performed
300 times start-to-end simulations to see the
fluctuation of the longitudinal phase space at
the entrance of undulator.
beam chirp and position are very dynamically
dancing !
under this situation, peak current, beam
arrival time, and slice beam parameters are
also very dynamically dancing, which induce
unstable XFEL photon beams.~ 100 fs
3434343434343434
2 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
median : ~ 1.5 µs
rms variation : ~ 16 fs
median : ~ 13 GW (80% core slices)
rms variation : ~ 130%
with loose tolerances, power fluctuation
is very strong.
median : ~ 19 m
rms variation : ~ 12%
median : ~ 0.1 nm
rms variation : ~ 0.008%
poor performance with loose tolerances to generate single spike at 0.1 nm with 2 pC!
353535353535
2 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
gun timing error ≤ 1 fs (rms)
bunch charge error ≤ 0.5% (rms)
injector S-band RF phase error ≤ 0.001 deg (rms)
injector S-band RF voltage error ≤ 0.001% (rms)
injector X-band RF phase error ≤ 0.004 deg (rms)
injector X-band RF voltage error ≤ 0.004% (rms)
BC1 & BC2 dipole power supply error ≤ 1.0 ppm (rms)
LINAC1 S-band RF phase error per klystron ≤ 0.001 deg (rms)
LINAC1 S-band RF voltage error per klystron ≤ 0.001% (rms)
LINAC2 S-band RF phase error per klystron ≤ 0.001 deg (rms)
LINAC2 S-band RF voltage error per klystron ≤ 0.001% (rms)
For 0.1 nm with 2 pC, we need much more tighter tolerances for stable operation:
S03 X01 BC1 LINAC1 BC2 LINAC2 5.8 GeV for 0.1 nm with 2 pC
Ultra-Tight Tolerances for 2 pC
363636363636
2 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
gun timing error ≤ 1 fs (rms)
bunch charge error ≤ 0.5% (rms)
injector S-band RF phase error ≤ 0.001 deg (rms)
injector S-band RF voltage error ≤ 0.001% (rms)
injector X-band RF phase error ≤ 0.004 deg (rms)
injector X-band RF voltage error ≤ 0.004% (rms)
BC1 & BC2 dipole power supply error ≤ 1.0 ppm (rms)
LINAC1 S-band RF phase error per klystron ≤ 0.001 deg (rms)
LINAC1 S-band RF voltage error per klystron ≤ 0.001% (rms)
LINAC2 S-band RF phase error per klystron ≤ 0.001 deg (rms)
LINAC2 S-band RF voltage error per klystron ≤ 0.001% (rms)
For 0.1 nm with 2 pC, we need much more tighter tolerances for stable operation:
Ultra-Tight Tolerances for 2 pC
under tighter tolerances for 2 pC, we
performed 300 times start-to-end simulations
to see the fluctuation of the longitudinal phase
space at the entrance of undulator.
beam position dancing was reduced and chirp
dancing was dramatically damped.
under this situation, peak current and slice
parameters are almost constant. Therefore,
XFEL power becomes more stable. But there is
some small fluctuation in beam arrival time.~ 40 fs
37373737373737
2 pC - 300 Times S2E Simulation with Errors
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
median : ~ 1.5 µs
rms variation : ~ 4.5 fs
median : ~ 13 GW (80% core slices)
rms variation : ~ 12%
with tighter tolerances, fluctuation
is damped.
median : ~ 19 m
rms variation : ~ 3.9%
median : ~ 0.1 nm
rms variation : ~ 0.001%
great performance but ultra-tight tolerances! we will not use 2 pC to generate single spike !
year requirements compression factor operation conditions
2010 ϕs 0.1 deg (rms) 1 for injector gun
V/V 0.1% (rms) with 22 A, 200 pC
2011 ϕs 0.06 deg (rms) 16 for injector BC1
V/V 0.06% (rms) with 350 A, 200 pC
2012 ϕs 0.04 deg (rms) 75 for XFEL BC1+BC2
V/V 0.04% (rms) with 1.6 kA, 200 pC
2014 ϕs 0.02 deg (rms) 125 for XFEL BC1+BC2
V/V 0.02% (rms) with 2.7 kA, 200 pC
2016 ϕs 0.01 deg (rms) 240 for XFEL BC1+BC2
V/V 0.01% (rms) with 0.7 kA, 10 pC
after 2020 ϕs 0.005 deg (rms) 2400 for XFEL BC1+BC2
V/V 0.005% (rms) with 7 kA, 10 pC
These are requirements for S-band RF for about 1 minute. Requirements of X-band are four times of S-band.
383838383838
PSI-XFEL - RF Development Milestone
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
100 for LCLS 250 pC case
34 for LCLS 1 nC case
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3939
Summary
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
By performing the invariant envelope matching properly, slice and projected
emittances at the end of injector are very promising. They are smaller than 0.1 µm for
10 pC and smaller than 0.4 µm for 200 pC. Operations with 10 pC and 200 pC are
considered as the nominal modes, while the ultra-short mode with 10 pC will be
considered as an upgrade option.
By the help of the excellent emittance, we can use the low charge operation to generate
the coherent single spike at X-ray region.
We designed 13 different linac layouts with S-band and C-band RF linacs. Among
them, C-band based ones satisfy our design goal more easily (linac length < about 530
m, saturation of FEL power within a 50 m long undulator).
To minimize the bandwidth of XFEL photon beams, compensation of energy chirping
is a critical thing, which is normally difficult for us to compensate with a short S-band
linac.
To realize the stable single spike mode operation at 0.1 nm with 2 pC, it seems that we
need ultra-tight RF jitter tolerances. However, in case the other single spike mode at 1
nm with 10 pC, its required tolerances are somewhat looser. Therefore, we selected the
single spike mode at 1 nm with 10 pC as an upgrade mode.
4040
Summary & Acknowledgements
Low Emittance Gun based PSI XFEL Project - Yujong Kim of Paul Scherrer Institut, Switzerland
The single spike mode with a low charge has lots of advantages. But we need a high
resolution beam diagnostic system and ultra-tight RF tolerances to operate it stably.
If users does not care of arrival timing error and power fluctuation, the single spike
mode will be a great operation mode with a low charge.
Y. Kim sincerely give thank to many PSI colleagues (H. Braun, M. Pedrozzi, V. Schlott,
J.-Y. Raguin, T. Schilcher, and S. Reiche), Dr. Inagaki and Prof. Shintake of
RIKEN/SPring-8, Prof. Matsumoto of KEK, Dr. Miura of Mitsubishi Heavy
Industries, Dr. Yushiro of Toshiba, K. Floettmann of DESY, M. Borland of ANL, D.
Dowell, Y. Ding, J. Frisch, and P. Emma of SLAC for their encouragements, valuable
comments, useful information, and discussions for these works.
And many thanks to Rasmus for his presentation of this talk instead of me!