a transverse deflecting rf structure for sub-micrometer ... · a transverse deflecting rf structure...
TRANSCRIPT
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A Transverse Deflecting RF Structure for
Sub-Micrometer Bunches at 5 to 50 MeV
LOLA (Greg Loew, Rudy Larsen and Otto Altenmueller)
REGAE (Relativistic Eelectron Gun for Atomic Exploration)
a first idea about numbers
REGAE
bunch
TDS (Transverse Deflecting Structure) measurement
two examples
rf structures
Remarks / other ideas
literature
-
LOLA in the FLASH facility
transverse deflecting structures are standard diagnostic devices in FELS
(there is no FEL without them)
1 TDS in FLASH
1 in PITZ
x in LCLS, SACLA, Swiss FEL, FERMI, …
3 in European XFEL
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from Christopher Behrens, Groemitz 2010, Betriebsseminar
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LOLA setup: horizontal plane
TDS: vertical plane
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from Christopher Behrens, Groemitz 2010, Betriebsseminar
OTR-2 → longitudinal phase space
compressed bunch uncompressed bunch
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REGAE
gun
buncher
waveguide (3 GHz) longitudinal focus
bunch length
(Relativistic Eelectron Gun for Atomic Exploration)
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Astra calculation
bunch length
energy
longitudinal phase space
nm 253sim =σ nm 190sim =σ nm 256sim =σ nm 568sim =σ
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(a first discussion with Klaus Flöttmann)
not the last!
first idea about numbers
Q ≈ 100 fC
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TDS measurement without spectrometer magnet
TDS drift + screen
1s
3y
length L, strength K’ length D
drift + screen
223 yDyy ′+=
( ) ( ) 1113 2 sKLDLyDLyy ′++′++=→
1 2 3
′
1
1
1
1
δs
y
y
′→
2
2
2
2
δs
y
y
-
′
′
′≈
′
δδs
y
y
K
K
s
y
y
dZ
d
0
1
′′′
′′
=
16/2/
0100
010
02/1
322
2
LKLKLK
LK
LKz
T
1→2: (period averaged) equation of motion in TDS
E
yEeK
λπ2=′with
′=
′→
1
1
1
1
2
2
2
2
δδs
y
y
Ts
y
y
with
( ) sKpsEev
sFvdZ
dpzy
zy
z
y ′≈
≈≈λπ2
sin11
z
y
p
py
dZ
dy =′=
notation: uppercase Z for beam line coordinate
lowercase s for bunch coordinate
transport matrix
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δδ
σσσ CCCCCC
e
syys
e
yyyyyye LL44 344 21
LL4444 34444 21
LLL
2vert-long,
2vert,
2 +++++= ′′′′
( ) ( ) 1113 2 sKLDLyDLyy ′++′++=more general
′=
1
1
1
1
3
δs
y
y
wy
measured
( )22
,1
,1
,1
,1
,1
,1
,1
,1
2,3
23 me
t
t
fw
C
s
y
y
s
y
y
wy σσ
δδ
σ
ν
ν
ν
ν
ν
ν
ν
ν
ν +×=
′
′==
44 344 21
with 2,12
νσ sm = ( )( )22 KLDLf ′+=
systematic error
and
vertical optics (~ spot size without deflection)
vertical - longitudinal correlation
correlation matrix
what we want to know
ν is particle index
correlations with energy
( )4321 wwwww =with coefficients
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error from vertical phase space
( ) ( )( )( ) KLDL
DLDL yyyyve ′+
+++−=
2
2 22
,
γαβεσ
vertical emittance and Twiss parameters
velocity effects: additional error from uncorrelated energy spread
δδ σγσ
2/
3/
2 2, LD
LDL
re +
+≈ uncorrelated (relative) energy spread δδδσ C=2
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period averaged equation of motion in TDS
with velocity effects (γ−2 terms)
′
′
′≈
′−
δγ
δs
y
y
K
K
s
y
y
dZ
d
r2
1
( )442746353
4232
2534232
3635242
2
322
2
24/5040/720/120/
24/6/2/
2/120/24/6/
6/720/120/24/
1
16/2/
0100
010
02/1
−+
′′′′′′′
′′′′′′′′
+
′′′
′′
= rr
O
LKLKLKLK
LLKLKLK
LKLKLKLK
LKLKLKLK
LKLKLK
LK
LKL
T γγ
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two examples
bunch
aperture rfλ∝A
Ayx
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Example 1:(not optimized)
w = ���� � �� ����
beam width
z/m
y/m
� 0
relative focus
s = 0
aperture
aperture:
� ����
A = 0.6 mm
L = 5 mmz/m
� �
� � �/2mm 3≈λ
-
w = ���� � �� ����
beam width
z/m
y/m
� 0 s = 0
aperture
relative focus
� �
� � �/2
DL +
L
Example 2:(not optimized)
aperture:
� ����
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rf structures
Massimo Dal Forno, et. Al.
rf breakdown tests of mm-wave metallic accelerating structures
Phys. Rev. Accel. Beams 19, 011301 – Published 6 January 2016
f = 115 .. 140 GHz
Eacc < 0.3 GV/m
Esurface < 1.5 GV/m
pulse length 2.4 nsec
accelerating structure from
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P. Arcioni, M. Bressan, F. Broggi, G. Conciauro, L. Perregrini, P. Pierini:
The Groove Guide as an Interaction Structure for Microwave FEL
Nuclear Instruments and Methods in Physics Research, Section A 358, pp. 108-111, 1995
H-type groove waveguide from
might overcome the aperture limitation (for x direction)
but: linear range is still small!
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remarks
time resolution limited by: maximal field
length/γ2 and aperture
open: working point, frequency, SW or TW regime
structure technology
rf source
couplers
even the method
increase energy (ACC+TDS?) or reduce resolution
TDS focus changes with K’
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other ideas ???
external field self-field + geometry
observe beam effect
observe field resonator → radiationundulator → radiation
TDS + screen wake + instability
+screen ~ Q2
observe
stimulate
sa σγ >
resonator → radiationundulator → radiation
22
2
ph 2
21~2
γλλ
γλπσ uus
K ≈+=
required undulator period su σπγλ22~
µm 60nm 100102 2 ≈⋅⋅π1002 6mm 1mm/100yes!
no!
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short magnet + spectrometer
take one magnet from the undulator → coherent short magnet radiation
multichannel infrared spectrometer
ph~2nm 200 λπσ s<
optical spectrometer
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literature
Klaus Floettmann and Valentin V. Paramonov
Beam dynamics in transverse deflecting rf structures
Phys. Rev. ST Accel. Beams 17, 024001 – Published 5 February 2014
Benno Zeitler, Klaus Floettmann, and Florian Grüner
Linearization of the longitudinal phase space without higher harmonic field
Phys. Rev. ST Accel. Beams 18, 120102 – Published 30 December 2015
ragae:
tds:R. Akre, L. Bentson, P. Emma, P. Krejcik
Bunch length measurements using a transverse rf deflecting structure in the SLAC linac
SLAC-PUB-9241, PAC2002
structures:
P. Arcioni, M. Bressan, F. Broggi, G. Conciauro, L. Perregrini, P. Pierini:
The Groove Guide as an Interaction Structure for Microwave FEL
Massimo Dal Forno, et. Al.
rf breakdown tests of mm-wave metallic accelerating structures
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funny beam dynamics:
−=
′ 0001.0001.0
1
1
y
y
=
0
0
1
1
δs
=
′ 0001.0
1
1
y
y
−=
′ 0002.0001.0
1
1
y
y
′
′
′≈
′
δδs
y
y
K
K
s
y
y
dZ
d
0
1
( )Zy
Z
=
0
0
1
1
δs
=
0
0
1
1
δs
′
′
′≈
′−
δγ
δs
y
y
K
K
s
y
y
dZ
d
r2
1
parameters as for example 2
( )22
1 −∞ ++= r
r
OTTT γγ γ
( ) ( ) 1XZTZX =