close

Вход

Забыли?

вход по аккаунту

?

• experimental results from • experimental results from PITZ - Desy

код для вставки
• experimental results from
ATF@BNL, SDL@BNL,
GTF@SLAC, SHI+FESTA@Japan,
A0@FNAL, ELBE@Rossendorf
• experimental results from
PITZ@Zeuthen
• How to reach the beam quality required
for the XFEL ?
Frank Stephan (DESY Zeuthen),
TESLA meeting, Zeuthen, January 2004
Projected Emittance Measurements at ATF@BNL
parameters:
* 0.5 nC
* 110 MV/m at gun
* beam energy: 60 MeV
methode:
* fitting Twiss parameters to
4 subsequent beam size
measurements
* transport optics adjusted to
maximize beam size at BPM
locations
V. Yakimenko et. al.,
FEL 01
fit result:
n=
0.8 Вµm for 0.5 nC, accuracy: better than 15%
path to small emittance:
check resolution limit of BPM, stability of laser and RF, BBA of beam optical
elements, improve gun gradient and QE, optimize transverse laser shape and
emission phase, tune beam with SASE gain at VISA
Transverse Laser Shape Studies from ATF@BNL
cylindical symmetric
non-cylindical symmetric
parameters:
• 0.46 – 0. 48 nC
• phase: 30º from zero
crossing
• emittance measured
at 40 MeV via quad
scan
additional study:
emittance vs
charge ~ linear
F. Zhou et. al.,
EPAC 02
Slice Emittance Measurements from SDL@BNL
setup:
y
t
parameters:
• 75 MeV
signal (arb units)
• 200 pC
360
340
320
300
280
260
240
220
200
180
160
14
16
18
20
22
24
26
streak delay (picoseconds)
• laser: 2.4 ps FWHM
• slice width ~400 fs
Courtesy of W. Graves
Slice Emittance Measurements from GTF@SLAC
Spectrometer
Image
setup:
head
• 300 pC
• laser: 1.8 ps FWHM
2 mm diameter on cathode
Energy/Time
100
Current (A)
parameters:
D. H. Dowell et. al.,
LCLS-TN-03-2 (corr.)
60
40
20
-4
5.0
4.0
e n (mm)
• beam size: signal cut at 5% of max.
80
0
• phase: 30º from zero crossing
• slice width 550-750 fs
tail
3.0
-2
0
Time (ps)
Bsol = 1.982 kG
Bsol = 1.967 kG
Bsol = 1.937 kG
2
4
projected
emittance
2.0
1.0
0.0
-4.0
-2.0
0.0
Time (ps)
2.0
4.0
Projected Emittance vs Charge from GTF@SLAC
Courtesy of
J. Schmerge
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
6
WR on Emittance from SHI+FESTA@Japan
• 1.6 cell S-band gun (® 4 MeV) + 70 cm SW linac (® 14 MeV)
• Ti:Saphire laser system (® 50 fs long pulses at 800 nm) +
pulse shaping (e.g. gratings + liquid crystal spatial light modulator)
• temporal shape of laser pulses: (x-ray streak camera, resolution: ~2 ps)
„Gaussian“
rise/decay time: 1.5 ps,
limited by streak camera
„Square“
• transverse laser distributions: (cathode)
F. Sakai et. al., ICFA workshop 2002, SPring8
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
7
Methode: quad scan @ 14 MeV, gaussian fit to background subtracted signal frames
1.2
For 1 nC:
e
Frank Stephan
n
В» 1.2 p mm mrad
F. Sakai et. al., 8
ICFA workshop 2002, SPring8
TESLA meeting, Zeuthen, Jan. 2004
Measurements at FNPL(A0)@FNAL
flat beam production:
after solenoid field:
Courtesy of
Ph. Piot
et. al.
after skew quads:
proof-of-principle experiment done, measured:
В® now working for ratio > 100
towards polarized electrons: vacuum !! В®crogenic operated 1 ВЅ cell Cu gun
also working on e.g. plasma-wakefield acc.,
laser-based acceleration (needs E upgrade)
NEXT:
energy upgrade
+ 3.9GHz accelerating structure
+ 3.9 GHz deflecting cavity
SC RF Gun Development at ELBE@Rossendorf
1.3 GHz, 10 kW
half cell & 3 TESLA cells
Ez,max= 33 MV/m (1/2 cell)
= 50 MV/m (T cells)
77 pC
1 nC
Collaboration: BESSY, MBI, TJNAF, Univerity of
Peking, BINP, DESY, ACCEL, TU Dresden
• first operation of a SRF photo gun (1/2 cell) in 2002:
В® measured current, energy + emittance @ ~1 pC
• start of the 3+1/2 cell project in 2004:
I = 1 mA CW
E = 9.5 MeV
0.5 mm
mrad
Cavity
Cathode
2.5 mm
mrad
(without th. emit.)
Cooling insert
Courtesy of J. Teichert
Frank Stephan
Choke filter
TESLA meeting, Zeuthen, Jan. 2004
Helium tank
10
Experimental Results from PITZ@Zeuthen
Collaboration:
BESSY Berlin,
INFN Frascati,
INR Troitsk,
LAL Orsay,
TU Darmstadt,
U Hamburg,
DESY (HH + Z),
INFN Milano,
INRNE Sofia,
MBI Berlin,
TU Eindhoven,
YERPHI Yerevan
(1.3 GHz)
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
11
The Laser System at PITZ, В©MBI Berlin
Pulse shaper
(T = 5%)
Diode-pumped
Nd:YLF oscillator
diode-pumped
Nd:YLF preamplifier
1047 nm
AOM EOM AOM
fround trip = 27 MHz
Faraday
pulse
picker
1 MHz
Emicro = 16 mJ
P = 16 W
Emicro = 200 mJ
P = 200 W
pulse
picker
2-stage diode-pumped
Nd:YLF amplifier
Frank Stephan
fast
current
control
fast
current
control
2-stage flashlamp-pumped
Nd:YLF booster amplifier
TESLA meeting, Zeuthen, Jan. 2004
fourth
harm.
to
photocathode
20 ps flat-top
4 ps edges
Emicro = 30 mJ
Eburst = 24 mJ
UV (2662 nm)
shot-to-shot
optimizer
12
Longitudinal and Transverse Laser Profiles
longitudinal
transverse (measured in UV at virtual cathode)
(measured at 524 nm)
Measured
Flat Top Fit
a.u.
120
100
80
60
40
20
0
-20
y
FWHM В» 18-23 ps
rise/fall ~ 5-7 ps
40
50
60
70
t / ps
80
x
90
100
variable transverse size:
round diaphragms in the laser
room (~ 20 m from the cathode)
are imaged on the cathode
standard
parameters
Longitudinal Momentum of the Electron Beam
Mean momentum vs RF phase
f0, deg
RMS momentum spread vs RF phase
f0, deg
Maximum mean momentum 4.72 MeV/c
Minimum rms momentum spread 33 keV/c
Electron Beam Longitudinal Profile
Cherenkov radiation
use of aerogel: SiO2 ,
refractive index ≈ 1.03
Bunch length (mm) in RMS 90 %:
f0, deg
Minimum bunch length:
FWHM = (21.04 В± 0.45stat В± 4.14syst) ps
= (6.31 В± 0.14stat В± 1.24syst) mm
Transverse Beam Emittance Measurement
Single Slit Scan Technique
Beam spot at screen 2
Beamlets at screen 3
single slit
position
size of the beamlet is
measured for three slit
positions:
yn = Y
screen 2
n ГЋ {- 1,0,1}
+ n Г— 0.7s yscreen 2
Transverse Emittance vs Bunch Charge
laser diaphragm diameter D = 1.0 mm (not final optimum)
Оµn (ПЂ mm mrad)
10.0
9.0
8.0
7.0
6.0
5.0
4.0
emittance vs. charge, Imain = focus+5A
emitt_X 0deg
emitt_Y 0deg
emitt_X -5deg
emitt_Y -5deg
3.0
Оµn ~ Q
2.0
1.0
0.0
0.01
Frank Stephan
0.10
1.00
TESLA meeting, Zeuthen, Jan. 2004
Q (nC)
10.00
17
Steps to improve Beam Emittance
• status in Sept. 2003: min. emittance ≈ 3 π mm mrad
• improvement: steer beam away from vacuum mirror
1 nC, D = 1.2 mm
vacuum mirror
steerer A
improvement: > 0.5 ПЂ mm mrad
• systematic experimental optimization: long. laser profile, trans.
laser profile, 2D scan Imain and RF phase, Ibuck for fine tuning
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
18
ASTRA Simulation of Transverse Emittance
Parameters used for the
simulation:
• charge = 1 nC
• longitudinal laser profile:
– flat top
– 20 ps FWHM
– 5 ps rise/fall time
• transverse laser profile
– homogeneous
– sx,y = 0.6 mm
• max. gradient at the
cathode: 42 MV/m
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
19
Transverse Emittance Measurements
Parameters: 1 nC, ~20 ps FWHM, ~7ps rise/fall time,
diaphragm = 1.2 mm
norm. emittance Y / Вµm
Imain - Ifocus / A
Imain - Ifocus / A
norm. emittance X / Вµm
RFphase - F0 / degree
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
RFphase - F0 / degree
20
Fine Tuning of Laser Parameters
( measured in UV )
transverse profile
( D=1.2 mm )
Пѓ x = 0.55 В± 0.02 mm
Пѓ y = 0.61 В± 0.02 mm
Frank Stephan
FWHM В» 21 ps; rise/fall time В» 7 ps
TESLA meeting, Zeuthen, Jan. 2004
21
Measured Transverse Emittance vs Bucking Solenoid
normalized emittance / p mm mrad
3,0
Start-up Requirement for TTF2 =3
Оµx
2,8
1 nC, -5deg, Imain = 305 A
Оµy
2,6
Оµ x Оµy
2,4
2,2
2,0
1,8
1.7
1,6
1.5
1,4
1,2
WR=1.2
1,0
0
Requirement for the XFEL=0.9
10
20
30
40
50
Ibuck / A
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
Start-up requirement
of TTF2 is clearly fulfilled 22!
60
Summary PITZ1
• electron beam was characterized in a wide range of machine
parameters (e. g. Q, О¦0, Imain, Ibuck, laser parameters)
• optimum settings @ 1 nC:
Оµ x Оµ y = 1.7 p mm mrad
Оµ y = 1.5 p mm mrad have been reached with:
longitudinal laser shape:
�flat top’, FWHM » 21 ps, rise/fall time ≤ 7 ps
transverse laser profile:
�homogeneous’, sx,y » 0.55 - 0.6 mm
solenoid current:
Imain В» 305 A, Ibuck В» 20-25 A в†’ Bz = 0 at cathode
RF parameters:
gradient at cathode: ~ 42 MV/m
phase: F В» F0 - 5В° ,
• cavity is now installed at TTF2
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
23
How to reach the beam quality required for XFEL
Goal: 0.9 ПЂ mm mrad from the injector for 10 Hz, 650 Вµs !!
• upgrades with ~ 40 MV/m at the cathode:
– really homegenous transverse laser profile:
Гћ Оµn ~ 1.5 ПЂ mm mrad @ 1 nC
(ongoing in 2004)
– improved longitudinal laser profile ( 2 ps rise/fall time):
Гћ Оµn ~ 1.2 ПЂ mm mrad @ 1 nC (realisation in ~2004-2006)
• in addition, with 60 MV/m at the cathode:
Гћ Оµn ~ 0.9 ПЂ mm mrad @ 1 nC (started, ongoing in 2004,
depending on 10 MW
klystron)
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
24
Proposed Setup for Laser Beam Line to Cathode
Lin,1
beam-shaping
aperture
d = 2 mm
Lout,1a Lout,1b
f = 750 mm
f = -5000
<------------- M = 7.3 ------------->
Gaussian pinhole
input beam
FWHM = 2mm
<----- laser table ----->
f = 3000 mm
M1
M2
5m
Lin,2b Lout,2a Lout,2b
f = 750
f = -750 f = -750 f = 750 mm
<- wall ->
<--- M = 1:1 --->
M4
<------ optical rail ------>
M3
<-------------- shaft -------------->
0m
Lin,2a
10 m
Z0 - 25 cm
Z0
V - 50 cm
V - 25 cm
V - 00 cm
MV
photocathode
marginal rays
15 m
Z0 + 25 cm
20 m
Z0 + 50 cm
3 mm
Z0 - 50 cm
- 50 cm
В± 0 cm
+ 50 cm
В© I. Will (MBI), status: Draft
-0.1
V + 50 cm
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0.2
0
-0.2
V + 25 cm
0.4
0
0
0.1
0.2
-0.2
-0.1
0
0.0
0
0.1
0.2
-0.2
-0.1
0
0.1
0.2
-0.2
-0.1
0
0
0.1
0.2
-0.2
-0.1
0
0.1
0.2
How to reach the beam quality required for XFEL
Goal: 0.9 ПЂ mm mrad from the injector for 10 Hz, 650 Вµs !!
• upgrades with ~ 40 MV/m at the cathode:
– really homegenous transverse laser profile:
Гћ Оµn ~ 1.5 ПЂ mm mrad @ 1 nC
(ongoing in 2004)
– improved longitudinal laser profile ( 2 ps rise/fall time):
Гћ Оµn ~ 1.2 ПЂ mm mrad @ 1 nC (realisation in ~2004-2006)
• in addition, with 60 MV/m at the cathode:
Гћ Оµn ~ 0.9 ПЂ mm mrad @ 1 nC (started, ongoing in 2004,
depending on 10 MW
klystron)
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
26
Photo Cathode Laser Development for PITZ 2
Goals: - stable and reliable laser system for long pulse trains
Strategy:
- micropulses temporal profile: 20 ps FWHM,
rise and fall time ≤ 2 ps
• further improve the
Nd:YLF laser system
- homogenous transverse intensity profile
• two-channel mixing
scheme
- laser parameters widely variable
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
В© I. Will, MBI
27
ASTRA Simulation of PITZ 2 (20ps FWHM, 2ps rise/fall time)
Xrms(TESLA) / mm
8
7
EmX(TESLA) / m
um
m
matching
condition
(M. Ferrario)
6
used gun
gradient:
40 MV/m
Xrms(CDS14) / mm
EmX(CDS14) / mm
um
m
5
CDS booster
Xrms(no booster) / mm
4
mum
EmX(no booster) / m
m
3
diagnostics section
2
Оµn =
1
1.2 Вµm
0
0
1
2
PITZ 2 setup:
Frank Stephan
Gun
Booster
3
4
5
z/m
6
7
TESLA meeting, Zeuthen, Jan. 2004
8
9
10
28
How to reach the beam quality required for XFEL
Goal: 0.9 ПЂ mm mrad from the injector for 10 Hz, 650 Вµs !!
• upgrades with ~ 40 MV/m at the cathode:
– really homegenous transverse laser profile:
Гћ Оµn ~ 1.5 ПЂ mm mrad @ 1 nC
(ongoing in 2004)
– improved longitudinal laser profile ( 2 ps rise/fall time):
Гћ Оµn ~ 1.2 ПЂ mm mrad @ 1 nC (realisation in ~2004-2006)
• in addition, with 60 MV/m at the cathode:
Гћ Оµn ~ 0.9 ПЂ mm mrad @ 1 nC (started, ongoing in 2004,
depending on 10 MW
klystron)
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
29
Transverse Beam Parameters for the XFEL Injector
Gun param.:
rms laser
spot
11.5 MV/m
0.75 mm,
uniform
assumed 0.74
therm.
mrad mm
emittance
25.0 MV/m
13.9 MV/m
laser
pulse
length
20 ps,
uniform
gun acc.
gradient
60 MV/m
injecting
phase
44В°
proj. emittance
В» 0.5 mrad mm
(no th. emittance)
Frank Stephan
TESLA meeting, Zeuthen, Jan. 2004
30
Документ
Категория
Без категории
Просмотров
8
Размер файла
3 223 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа