Download laser room - CERN Indico

Laser Beam Transport and Integration
AWAKE Collaboration meeting
Mikhail Martyanov
Christoph Hessler
Valentin Fedosseev
CERN, EN-STI-LP
CERN, 04-06.12.2013
Overview
• Short intense laser pulse is needed for:
– to create a 100% ionized plasma
– moving ionization front is a source of perturbation for proton-laser
instability (micro-bunching and wake-field with a stable phase)
• Plan for the Laser system:
– First it is delivered to MPP Munich for plasma experiments
– Then it goes to CERN
05.12.2013
M.Martyanov, CERN
- mid 2014
- end 2015 ?
2
AWAKE Area:
Zones
- doors to laser room,
local access control
- doors with central
access control
- safety “shutters” with central control
AWAKE gallery
laser SAS
e-gun room
laser room
Laser
connection tunnel
to be drilled…
e-gun
laser beam 2
400mm
p-tunnel
electron beam
laser beam 1
proton beam
05.12.2013
M.Martyanov, CERN
plasma chamber
3
Overview
• Laser system comprises:
- laser with 2 beams (for plasma and for the e-gun)
- delay line is possible in either one of these beams
- optical compressor
- focusing telescope
- small optical compressor and 3rd harmonics generator for e-gun
• Laser parameters for plasma:
- energy 450 mJ
- pulse duration 120 fs after compression
- beam diameter 40 mm (smoothed flat-top)
05.12.2013
M.Martyanov, CERN
Only reflective optics
on the way
Rule of thumb (B<1):
I[GW/cm2]L[cm]<36
4
Laser system base-line
• Laser, Compressor and Telescope are in the laser room
• Focusing down to 35 meters to the center of the plasma
• Question is if this possible?
• Back solution: Compressor and Telescope are next to merging point
in the proton tunnel
• Focusing down to 25 meters to the center of the plasma
• Question is if this possible?
Crucial points are:
•
•
•
•
•
Focusability of the laser beam down to 25 or 35 meters
No detailed information on the laser system yet (beam quality)
The placement of the optical compressor and the focusing telescope has an impact on
the position of the anew drilled connection tunnel
Availability of vacuum components for the compressor and telescope is under study.
10-6 Torr “easily” achievable. Pellicle or differential pumping as an option to go better
05.12.2013
M.Martyanov, CERN
5
Base Line: Merging point Laser + Protons
Protons and laser towards plasma
Merging point
05.12.2013
M.Martyanov, CERN
Thanks to integration team for pictures
Some measurements of laser room with respect to merging point
6
Horizontal connection tunnel 400mm
Thanks to integration team for pictures
05.12.2013
M.Martyanov, CERN
7
Merging point in details
1400
last mirror
laser beam
• p-beam height about 1 m
• HV volume (10-6 Torr) can be “easily” achieved in the laser pipes
• UHV volume (10-8 Torr) is supposed to be in the p-beam line
500
HV volume
500
1400
750
500
p-beam
10002000
05.12.2013
M.Martyanov, CERN
8
Merging point in details
•
•
•
•
Distance from p-beam envelope to optical axis is 14 mm
Assuming laser beam  10 to 16 mm
Gap between beams is 6 to 9 mm
Tough but manageable
• Possible issue: mirror charging and destruction
laser beam
gap 6  9 mm
proton beam
Thanks to Chiara Bracco
05.12.2013
M.Martyanov, CERN
9
Vacuum components
Company
Product
Comments
ARUM Microelectronics
Stepping motors, translators
1e-10Torr
Phytron
Stepping motors
1e-11Torr, 10MJ/kg rad.resist.
Princeton Research
Instruments
Stepping motors, translation
and rotation stages
1e-09Torr, 4e-10Torr achieved
with 190 l/s pumping
Tectra
Stepping motors
1e-10Torr
NewFocus
Picomotors
1e-09Torr
SmarAct
Picomotors, mirror mounts,
translators
1e-09Torr,
2900 Eur per mount
Standa
Everything… but
Mounts 1e-09Torr,
Motorized 1e-06Torr 1800Eur
05.12.2013
M.Martyanov, CERN
10
Compressor and Telescope are in the laser room
Flat-top beam focusing profiles
Focusing of a 430 mJ flat-top beam 35 m downstream to the middle of the plasma.
At the ideal Gaussian waist Wmax = 6.84 J/cm2 and FWHM = 2.35 mm.
Flat-top beam focusing has been optimized to obtain the same maximum fluence somewhere in
the plasma and equal fluence on both sides. Flat-top beam d=14 mm , f=52 m looks like a
Gaussian beam and considered as an optimum.
0 m, FWHM=14mm, Wmax=0.32J/cm2
10 m - last mirror, beam size 16 mm, no peak in the
middle for reasonably smooth beams, Wmax ~ 0.5J/cm2
cm
35 m, FWHM=2mm, Wmax=6.6J/cm2
11
Compressor and Telescope are at the merging point
Flat-top beam focusing profiles
Focusing of a 430 mJ flat-top beam 25 m downstream to the middle of the plasma.
At the ideal Gaussian waist Wmax = 6.84 J/cm2 and FWHM = 2.35 mm.
Flat-top beam focusing has been optimized to obtain the same maximum fluence somewhere in
the plasma and equal fluence on both sides. Flat-top beam d=10.6 mm , f=47 m looks like a
Gaussian beam and considered as an optimum.
0 m, FWHM = 10.6mm, Wmax=0.57J/cm2
20 m, FWHM = 1.6mm, Wmax=5.9J/cm2
05.12.2013
M.Martyanov, CERN
cm
25 m, FWHM = 1.9mm, Wmax=6.8J/cm2
12
Compressor predesign
Two gold coated gratings 1700 lines/mm, 100x140 and 120x140 mm
Damage threshold ~ 250 mJ/cm2 (in AWAKE less then 100 mJ/cm2)
Efficiency per 1 reflection @ 800nm and 10deg deviation – 92%
Gratings supplier – SPECTROGON, Sweden
Acceptance: compress 160 ps to 120 fs, bandwidth 24nm, beam size 50mm
Compressor fits to 1200 x 400 mm footprint, 400 mm high, 2 view-ports for alignment
Max efficiency of the compressor – 70%
05.12.2013
M.Martyanov, CERN
13
Telescope predesign
Around 3-fold mirror telescope, detuned to provide 25 meter focusing, flat geometry
Concave mirror R=2400mm, incident angle 2
Convex mirror R=800mm, incident angle -3.54 in the same plane
Mirrors displacement 806mm
Beam size 40mm, ray focal spot size ~100m
Aberrations are negligible with respect to diffraction limit (spot size ~1 mm)
Telescope footprint is 1000 x 200 mm
05.12.2013
M.Martyanov, CERN
14
Compressor and Telescope
Entire footprint is 2400 x 600 mm
Launch mirror 3”
05.12.2013
M.Martyanov, CERN
Concave mirror 3”
Mirrors 2”
Convex mirror 2”
15
Laser dedicated list of “Things to Do”:
Laser Installation
System
To define / To do
Laser room, equipped with a big Air circulation, conditioning, humidity, filters, circuits (electrical,
SAS
demineralized water, tap water, compressed air, control cables), safety
(fire/smoke alarm), shutters, access etc.
Connection tunnel 40cm
Drilling, coordinates of laser beam to be defined
Access to laser room and tunnel
AWAKE access concept including Laser Access Modes to p-tunnel and
e-gun room, safety shutters
Ti:Sa laser
Arrangement in a squeezed room, max laser table width is 1m
Chillers and electronics are below the tables or in the separate ventilated
rack/cabinet or in the big SAS
Vacuum pulse compressor and Placement is not defined yet
focusing telescope.
Placement in the laser room is a base-line
In case of p-tunnel everything must fit between p-beam and wall,
HV (10-6 Torr) or UHV (10-8 Torr): “dirty” environment in p-tunnel is not good for compressor/telescope
pellicle or differential pumping
installation and maintenance
Transfer line to p-tunnel
Merging point chamber
HV
UHV (only 2 mirrors, possibly without in-vacuum motors)
Transfer line to e-gun
Separate small compressor
3rd harmonic generation
In fore-vacuum
Next to the gun
05.12.2013
M.Martyanov, CERN
16
Laser dedicated list of “Things to Do”:
Laser Operation
System
Ti:Sa laser
Issues
Controls and diagnostics are provided by the supplier of the laser system
Pulse compressor and focusing Diagnostics are provided by the supplier
telescope
Laser beam in the p-tunnel
Steady diagnostics:
Focused beam spot monitor (virtual plasma, the same long distance run);
near field before merging mirror; screens before and after plasma tube
sensitive to “both” beams (laser, electrons, protons) also equipped with
fiber-coupling for rough timimg measurements
On demand or maintenance diagnostics:
Auto-correlator, angular spectrometer, phase-front detector, …
Laser beam in the e-gun room
(small compressor and 3rd
harmonic generation are next
to the gun)
Steady diagnostics:
Virtual cathode CCD, UV energy meter, some IR signal coupled to a fiber
for rough timimg measurement
On demand or maintenance diagnostics:
Auto-correlator, angular spectrometer, …
Delay control between pulses: Delay line either on one of 2 beams, proper delay simulation required.
ionization and e-gun
Split after RegAmp was proposed by AMPLITUDE with 2.5mJ IR output for
e-gun
05.12.2013
M.Martyanov, CERN
17
Alignment of 3 beams
Just started …
OTR or laser light
- Imaging (lens system and CCD)
- Capture and measure with photodiode or streak-camera
(coupling to a fiber or lens system)
- Other techniques
laser-beam
05.12.2013
plasma
BPM
BPM
p-beam
M.Martyanov, CERN
18
Alignment of 3 beams
•
•
•
•
3 beams (protons, electrons and laser) have to be align in space and time
Transverse accuracy ~ 0.2mm
Angular accuracy ~ 0.2mm / 10 m = 20rad
Timing electrons-laser ~ 100fs – alignment by response? Rough alignment is needed
anyway
• Timing protons-laser ~ 100ps – alignment with fast photodiode and scope possible,
1pJ of light is required. Streak-camera.
For robust alignment of 3 beams we need an optical
signal which comes from the same screen sensitive to 3
beams (the power of laser beam can be reduced for the
measurements not to damage the screen)
05.12.2013
M.Martyanov, CERN
19
AWAKE access modes are under discussion …
05.12.2013
M.Martyanov, CERN
20
Thank you!
05.12.2013
M.Martyanov, CERN
21