Transcript Injector Commissioning Results

Injector
Commissioning
Injector Commissioning Results presentated to the
Facilities Advisory Committee, October 2007, by J.
Welch on behalf of the LCLS Commissioning Team.
October 29, 2007
FAC
James Welch
[email protected]
Introduction
Last April
Today
Commissioning plans
October 29, 2007
FAC
James Welch
[email protected]
Injector Layout
UV laser
OTR screens (7)
YAG screens (7)
Wire scanners (7)
Dipole magnets (8)
Beam stoppers (2)
S-band RF acc. sections (5)
RF Gun
Gun
Spectrometer
Emittance
Screens/Wires
6 MeV
Emittance
Screen/Wires
RF
Deflector
L1S
2-km point in 3-km SLAC linac
135-MeV
Spectrometer
(not to scale)
October 29, 2007
FAC
135 MeV
X-band RF
acc. section
BC1
TD11
stopper
250 MeV
James Welch
[email protected]
Summary April 16, 2007
(Last FAC Meeting)
April 5:
First e- from gun (6 MeV)
April 8:
First e- to inj-spectrometer (135 MeV)
April 14:
First e- through BC1 (250 MeV)
Beam transported to all areas. No trouble, but no systematic
checkout yet.
Controls still under development, but working well and improving
fast – great cooperation and effort
Communication with laser group excellent
Screens and toroids late, but installation continued
Some quality control issues with a few components
October 29, 2007
FAC
James Welch
[email protected]
Where We are Now
Commissioning Results
All Injector Commissioning Goals achieved
x & y emittance 1.2 m at 1 nC charge (design)
<1.5% rms charge stability (design is 2%)
Drive laser 98% up-time with 500 J (250 design)
Bunch compression in BC1 fully demonstrated
Remaining problems
Gun Faraday cup and toroid don’t work
BC1 dipole field quality is poor
Emittance growth from X-band RF
OTR beam size measurements altered by
COTR
Accelerated LCLS beam to 16 GeV (13.6 design)
Bunch length from injector 30% too long (1.1
mm, but design is 0.85 mm)
X-band & 2 RF deflectors both operational
Wire-scanners vibrate
New RF performing within spec (e.g., <0.1º rms)
Improvements underway
Feedback ON: launch, charge, energy, RF, & sz
Robust, high-quality RF gun
October 29, 2007
FAC
James Welch
[email protected]
FAC
http://wwwssrl.slac.stanford.edu/lcls/internals/commissioning/documents/l
clsinjector-commissioninggoals.doc
2007 Injector Commissioning Goals
October 29, 2007
James Welch
[email protected]
Laser Performance
R = 0.8 mm
8.87.2
psps
P. Hering. Oct. 8
Spatial shape on cathode using iris
Temporal shape (7.1 ps FWHM)
98% up-time with 500 J (250 J design).
Spatial profile and position stability were initially poor, but improved greatly
by extending the length of the drift tubes.
October 29, 2007
FAC
James Welch
[email protected]
Emittance Performance
design emittance
October 29, 2007
FAC
James Welch
[email protected]
Gun QE Performance
Emission Image of Cathode
on YAG
<1.5% rms
charge
stability
(design is
2%)
Now up to 1 nC
October 29, 2007
FAC
James Welch
[email protected]
EPIC Controls
Magnets
LLRF
Collimator
User App.
Launcher
MPS
Vacuum
Also use SLC Controls
October 29, 2007
FAC
Heroic and
successful
effort by the
Controls Group
James Welch
[email protected]
Matlab Application
Emittance Measurement - H. Loos
Example: emittance
measurement
Watch profiles as
scan proceeds
(avg. ~10)
Measure
emittance at
chosen location
using 3 OTRs, 3
wires, or quad
scan on OTR or
wire
Send results
to E-log
October 29, 2007
FAC
James Welch
[email protected]
gex (μm)
Transverse Wakefield in X-Band Structure
J. Turner
Dx  0.6 mm
Q  700 pC
sz  1 mm
E = 250 MeV
BC1 OFF
X-band RF OFF
X-Band cavity to be re-aligned
during this downtime.
Time Resolved Measurements
RF deflector OFF
RF deflector ON
RF deflector ON
in spectrometer
head
 high E
tail
sE  6 keV rms (40 m)
at 150 pC
October 29, 2007
FAC
James Welch
[email protected]
OTR2
135 MeV
Bunch Length
Measurements
PR55
14 GeV
Thanks to Controls Group
135 MeV
1.10 mm rms
14 GeV
‘Max’ Compression
14 GeV
BC1 Design Compression
520 A
97 A
10.3 ps
October 29, 2007
135 MeV
FAC
950 A
1.7 ps
14 GeV
0.89 ps
James Welch
14 GeV
[email protected]
Unexpected Physics!
Coherent OTR
Generation of COTR in the Visible Spectrum Indicates Micro-bunch Spike
& Interferes with Using OTR Profiles for Emittance Measurements. (~Frisch,
Tues 11:30)
OTR Light increases by 10-100 with maximum
compression
At max compression OTR Can Produce
“Ring-Like” Shapes!
Bunch Length Monitors
300 GHz
100 GHz
OTR
Optical
Signal
RF Phase of L1S, relative to crest (degS)
October 29, 2007
FAC
James Welch
[email protected]
BC1 Emittance Growth
BPM
CQ11
B2
B1
S-band acc.
poor bend field quality
BPM
B3
quads
correct hx
CQ12
BPM
OTR BPM
B4
TD11
wire(s)
best emittance transfer
nominal x-position
quads
off
read dnstr. BPMs while moving BC1
wire scan
after BC1:
gex  1.7 m
gex minimized with quads
Best gex after BC1 with nom. (& more) compression is 1.7 m (& larger)
Poor bend field quality (grad. + sext.) – DE/E scan shows 1st & 2nd-order hx
October 29, 2007
James Welch
Bends being upgraded + need shorter bunch (1.1 0.85 mm – less chirp)
FAC
[email protected]
Fix for BC1 Dipoles
Modifications include
wider poles (180 instead
of 100 mm) and new
pinning scheme for yokes.
October 29, 2007
FAC
James Welch
[email protected]
Commissioning Plans
1.2 km of existing linac (including new bunch compressor BC2) Frisch
~308 m of new transport line, LTU, up to Tune-up Dump at the
beginning of Undulator hall.
200 m of Undulator and Dump Line Nuhn
Commission the FEL X-Ray beam itself Welch
Commission the X-Ray diagnostics and beamlines Tompkins
1.
2.
3.
4.
5.
Injector
“LTU”
Linac
BC1
250 MeV
BC2
4 GeV
Existing and refurbished
housing
October 29, 2007
FAC
Undulator
“FEE” X Ray
Diagnostics
“NEH”
hutches
Xray
Tunnel
“FEH”
hutches
Electron
Dump
New housing construction.
Completion by ~ Mar. 08
LTU: Linac to Undulator
FEE: Front End Enclosure
NEH: Near Experimental Hall
FEH: Far Experimental Hall
BC1(2): Bunch compressors
James Welch
[email protected]
Timeline of Installation and Commissioning
FEE/NEH/X-Ray Tunnel/FEH Installation
Linac/BC2
LTU/UND/Dump Installation
Now
1st Spont. Light
1st FEL
Light 1st Users
2008
Controls checkout
& re-commission
Injector
…Injector
Commissioning
Linac/BC2
Commissioning
2009
Re-commission
Inj/BC2 to SL2
PPS
2007
PPS
J A S O N D J F M AM J J A S O N D J F M AM J J A S ON D
FEL/FEE
Commissioning
LTU/Und/Dump
Commissioning
downtime
commissioning
installation
October 29, 2007
FAC
James Welch
[email protected]
FEL Commissioning Timeline
October 29, 2007
FAC
James Welch
[email protected]
Thanks to All !
Commissioners
Laser Group
Operations
Controls
Power Conversion
MFD
Vacuum
Facilities
Acc. R&D
Metrology
ES&H (RP)
Mechanical Design
Materials Science
Facilities
Klystron/RF
SSRL/GTF
Acc. Systems
LCLS project personnel
Core group:
3 shifts/week
weekends
off
creditedno
to
a
large,
5 months
Results are very positive and
dedicated group of people at SLAC
+ R. Iverson, &
J. Schmerge…
October 29, 2007
FAC
James Welch
[email protected]