Beam manipulation by self-wakefield at ATF · · 2013-07-10Beam manipulation by self-wakefield at...
Transcript of Beam manipulation by self-wakefield at ATF · · 2013-07-10Beam manipulation by self-wakefield at...
Beam manipulation by self-wakefield at ATF
Sergey Antipov
Euclid Techlabs
ATF Program Advisory Committee and the ATF Users' Meetings, April 26 - 27, 2012
Outline
1. Enhanced Transformer Ratio demonstration (wakefield mapping with the shaped beam)
2. Tunable beam energy chirp compensator
3. Conversion of self-wake energy modulation into a THz bunchtrain
High Transformer Ratio
• Wake mapping at higher frequency > 1 λ covered, if you can pass the beam through. Rule of thumb: aperture ≥ 6∙σr
• TR = lower gradient for witness beam long structure;
• Structure-to-beam alignment is the name of the game; virtually 100% transmission is required
• 5D positioning stage, similar to what UCLA/SLAC designed for Kraken chamber at FACET.
– Can be used for many other experiments
– Can carry different structures simultaneously
2m
m
200um
L
• Structure – to – beam alignment • Changing chirp – adjusting structure for chirp compensation • Spectrometer resolution: adding slits and performing slice – scan • It can be a part of other experiment (energy modulation –
bunchtrain conversion)
Plans: tunable E-chirp compensation
Proposed Experiment: Tunable Energy Compensation
• Adjustable geometry WF structure
• Tunable energy compensation is required in a real device
• Experiment is similar to the previous E - chirp compensation measurement
• Change beam E-chirp adjust chirp compensation system
• Spectrometer resolution
spectrometer image of a beam that passed through the structure
Energy, MeV57 57.05 57.1 57.15 57.2 57.25 57.3
spectrometer image of unperturbed beam
Energy, MeV57 57.05 57.1 57.15 57.2 57.25 57.3
beam image after the mask, triangle length is 247 micron
200 250 300 350
70
80
90
100
110
Table top beam-based THz source
Energy modulation via self-wakefield
Chicane energy modulation conversion to bunch train
THz radiation wakefield structure
THz
Flexible: each step has a tuning range
BNL, ATF: S. Antipov, C. Jing et. al. Phys. Rev. Lett. 108, 144801 (2012)
BNL, ATF: G. Andonian et. al. Appl. Phys. Lett. 98, 202901 (2011)
SLAC, NLCTA: D. Xiang et. al. Phys. Rev. Lett. 108, 024802 (2012)
Measured beam spectrum
Energy chirped rectangular beam
Measured beam spectrum
Energy modulated rectangular beam Bunch train frequency content
Tunable 10% source: Range: 0.3-1.5 THz
Pulse bandwidth: 1% Energy in pulse: ~ mJ
DWA structure
Beam @ the entrance
THz Radiation @ the exit
0.3mm / 0.4mm Quartz 3cm long
(ATF beam) 2.4mm, 0.8nC rectangular
6 MW peak, 0.7THz, 161ps pulse, 0.9%BW, 1.4mJ per pulse
1mm / 1.2mm Quartz 10cm long
(AWA beam) 6.3mm, 10nC rectangular
0.5 GW peak, 0.3THz, 320ps pulse, 1%BW, 155mJ per pulse
Couple Scenarios
ATF example. Stage I: self-wake
-0.2 0 0.2 0.4 0.6-40
-20
0
20
40
z, cm
wa
ke
, M
V/m
wake from ginput beam, 0.24 cm long, with 0.8 nC charge
0 0.05 0.1 0.15 0.260
60.5
61
61.5
62
z,cm
En
erg
y,
Me
V
no structure
with structure
ID = 300um; OD = 400um; Quartz 0.7 THz, vgr = 0.395c, rsh/Q = 210kOhm/m
800 pC, 2.4 mm long flattop rectangular 2MeV energy chirp ≤ 1 cm structure is required
ATF example, stage II: chicane
-6 -4 -2 0 2 4112
113
114
115
116
117energy - position along the bunch, ATF case
t, ps
o
f th
e b
ea
m
chicane input
chicane output
0 2 4 6 80
50
100
150
200
250
300beam current profile, ATF case
t, ps
be
am
cu
rre
nt
chicane input
chicane output
0 1 2 3 4 50
0.2
0.4
0.6
0.8
1beam frequency content, ATF case
Frequency (THz)
Bu
nch
ing
fa
cto
r
bunched up beam
original beam• R56 = 0.03m • Particles between the bands are
bunched! • Bunched frequency content is higher
then the self-wake bunching frequency (can be almost 2 times higher)
• Tunability
Adjustment by chicane
-1.5 -1 -0.5 0 0.5 1 1.5 2111.5
112
112.5
113
113.5
114
114.5energy - position along the bunch; based on ATF experimental data
t, ps
o
f th
e b
ea
m
chicane input
chicane output, case 1
chicane output, case 2
Proposed Experiment: Bunching with Chicane
• Demonstrate Stage I + Stage II; Energy modulation followed by the chicane
• We are designing a chicane to fit after the “IP” chamber (R56~=0.03m; 0.5m long design with PM); spectrometer will have to move a little bit
• Use CTR interferometry to measure bunching
• Observe tunability by a) adjusting the chicane, b) using tunable wakefield structure
Summary
1. Enhanced Transformer Ratio demonstration
2. Tunable beam energy chirp compensator
3. Conversion of self-wake energy modulation into a THz bunchtrain
• designed on previous experience
• inter-related, share hardware, structures
• part of a big picture:
– FEL applications
– table top high power, narrow band, tunable THz source
• Hardware
– Positioning stage
– Spectrometer resolution
– Chicane