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1 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
1BFW ResultsJune 2009 FAC
BFW Results
Heinz-Dieter Nuhn – LCLS Undulator Group LeaderJune 9, 2009
2 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
2BFW ResultsJune 2009 FAC
LCLS Undulator Components
Quadrupole
BPM
Manual Adjustments
Segment
Cam Shaft Movers WPM
HLS
BFW
Sand-Filled, Thermally Isolated
Fixed Supports
Horizontal SlidesNot visible
Vacuum Chamber and
Support
3 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
3BFW ResultsJune 2009 FAC
Beam Finder Wire Location on Girder
Beam Finder Wire Housing
Beam Direction
Undulator Segment
Vacuum Chamber
4 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
4BFW ResultsJune 2009 FAC
BFW Assembly (Body Sectioned)
Wire card(Down Position)(Inactive Mode)
Lower Limit Switch(Actuated Position)
Pneumatic Solenoid Valve(Cylinder Vent Position)
Internal Return Spring(Expanded Position)
Electrical Connectors(Down Position)
Internal Kinematic Stop Plates
(Open Position)
Bellows Seal(Compressed Position)
BEAM
Potentiometer (Out Position)
Assembly model courtesy: J. Bailey, ANL
5 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
5BFW ResultsJune 2009 FAC
BFW Card
Material: MacorThickness: 3/16” (4.8 mm)Coating: Kovar
Full Stroke: 25.4 mm
X-wire end point: 39.614 mmBeam center: 40 mmGap between beam and X-wire: 0.386 mm
Y-wire end point: 37.014 mmBeam center: 37.2 mmGap between beam and Y-wire: 0.186 mm
Beam in OUT Position
Beam in IN Position
Beam travels out of slide plane
6 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
6BFW ResultsJune 2009 FAC
BFW Card Wiring: Tooling
Copper Tabs
Rods for hanging BFW wire with weights
Micrometer stage
BFW Card
Card holder
‘Carbon wire & weight’
• Wires soldered to copper tabs• Wires from copper tabs connect to BFW feedthrough• Feedthrough to be grounded and RF shieldedCourtesy: C. Field, Y.Sung
7 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
7BFW ResultsJune 2009 FAC
BFW Wires
X-Wire
Y-Wire
Nominal Beam Axisin IN Position
Card Out Direction(½ stroke length shown)
Wire Radius 34 - 40 µm
Note: Wires are fixed!Beam scanning will be achieved through girder motion.
8 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
8BFW ResultsJune 2009 FAC
BFW Functions
Beam Direction
A misaligned undulator will not steer the beam. It will just radiate at the wrong wavelength.The BFW allows the misalignment to be detected. (also allows beam size measurements)
A misaligned undulator will not steer the beam. It will just radiate at the wrong wavelength.The BFW allows the misalignment to be detected. (also allows beam size measurements)
Undulator QuadBFW
ReplacementVacuum Chamber
Wires
BFW
Planned Applications
Loose End Alignment
Beam Profile Scanning
Planned Applications
Loose End Alignment
Beam Profile Scanning
Girder
9 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
9BFW ResultsJune 2009 FAC
Location of BFW Detectors
40 Detectors are used for BFW readout 33 PEP-II style radiator/PMT units: one after each BFW device
5 ANL Beam loss monitors: next to PEP-II devices on girders 1, 9, 17, 25, 33.
2 Beam loss fibers: BLF U01-U16 covering upstream girder, BLFU 17-U33 covering downstream girders
Wire charge diagnostics is not installed
10 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
10BFW ResultsJune 2009 FAC
Scan Procedure Incorporated in Matlab GUI
Start matlab gui BFWscan_guiChoose girders (1-33), X-wire or Y-wire, scan range, and scan step sizeFor instance
Girder: 1 - 33Wire: ‘X’ and ‘Y’Range: -250 microns to +250 micronsStep size: 50 microns.
When started, the gui will then for each selected girderMove the girder cams to place the upstream girder end to the beginning of the scan range relative to the estimated collision point.(Motion is pivoted at the quadrupole)Move the wire card to “IN” position (while beam stopper is inserted)Take measurements from the 8 detectors, add the results to the graphs and go on to the next location.When done, return the girder to the position at which it was started.Move the wire card to “OUT” position.Move the girder back to its standard location.
The gui will stop the beam upstream of the undulator line during wire card insertion/extraction and during motion to the next position.
11 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
11BFW ResultsJune 2009 FAC
Scan with BFW11 Y-Wire
Dump Cerenkov Dump Scintillator
ANL BLM 25
Expected Collision Position
BLF:U17-U33BLF:U01-U16
PEP-II BLM25PEP-II BLM17
ANL BLM 33
12 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
12BFW ResultsJune 2009 FAC
BFW Alignment before FEL Commissioning
13 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
13BFW ResultsJune 2009 FAC
BFW Alignment after FEL Commissioning
14 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
14BFW ResultsJune 2009 FAC
DMP Cerenkov Detector Amplitudes
Noise levels is due to coarse step size of 50 microns.20 microns steps ize scans are planned for the near future.
15 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
15BFW ResultsJune 2009 FAC
Transverse Electron Beam Sizes
16 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
16BFW ResultsJune 2009 FAC
ANL/PEP Loss Monitor Responses
17 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
17BFW ResultsJune 2009 FAC
BLF 17-33 Responses
Girder Range Covered by Fiber
18 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
18BFW ResultsJune 2009 FAC
FEL Scattering on BFW wire
Fringes indicate transverse coherence
19 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
19BFW ResultsJune 2009 FAC
The 33 Beam Finder Wire (BFW) devices in the undulator system are working very well.They enable monitoring of several parameters
Loose-end alignmentBeam sizes, i.e. betatron matchingBLM calibrationTransverse FEL coherence.
Radiation levels produced by the scans are much lower than originally estimated allowing unrestricted use.Use has so far been restricted to higher electron beam energies due to the possibility of wire damage when interacting with the lowest energy FEL beam.
The 33 Beam Finder Wire (BFW) devices in the undulator system are working very well.They enable monitoring of several parameters
Loose-end alignmentBeam sizes, i.e. betatron matchingBLM calibrationTransverse FEL coherence.
Radiation levels produced by the scans are much lower than originally estimated allowing unrestricted use.Use has so far been restricted to higher electron beam energies due to the possibility of wire damage when interacting with the lowest energy FEL beam.
Summary
20 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
20BFW ResultsJune 2009 FAC
End of Presentation