Transcript Beam Finder Wire Results

BFW Results
Heinz-Dieter Nuhn – LCLS Undulator Group Leader
June 9, 2009
BFW Results
June 2009 FAC
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Heinz-Dieter Nuhn
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LCLS Undulator Components
Vacuum
Chamber and
Support
BFW
Segment
Quadrupole
Cam Shaft
Movers
WPM
Manual
Adjustments
BPM
Horizontal Slides
Not visible
Sand-Filled,
Thermally Isolated
Fixed Supports
BFW Results
June 2009 FAC
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HLS
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Heinz-Dieter Nuhn
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Beam Finder Wire Location on Girder
Beam Finder Wire Housing
Undulator Segment
Vacuum Chamber
BFW Results
June 2009 FAC
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Heinz-Dieter Nuhn
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BFW Assembly (Body Sectioned)
Potentiometer
(Out Position)
Electrical Connectors
(Down Position)
Internal Return Spring
(Expanded Position)
Internal Kinematic Stop
Plates
(Open Position)
Pneumatic Solenoid Valve
(Cylinder Vent Position)
Lower Limit Switch
(Actuated Position)
Bellows Seal
(Compressed Position)
Wire card
(Down Position)
(Inactive Mode)
BEAM
Assembly model courtesy: J. Bailey, ANL
BFW Results
June 2009 FAC
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BFW Card
X-wire end point: 39.614 mm
Beam center: 40 mm
Gap between beam and X-wire: 0.386 mm
Material: Macor
Thickness: 3/16” (4.8 mm)
Coating: Kovar
Y-wire end point: 37.014 mm
Beam center: 37.2 mm
Gap between beam and Y-wire: 0.186 mm
Full Stroke: 25.4 mm
Beam in OUT Position
Beam in IN Position
Beam travels out of slide plane
BFW Results
June 2009 FAC
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Heinz-Dieter Nuhn
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BFW Card Wiring: Tooling
Micrometer
stage
BFW Card
Rods for hanging BFW
wire with weights
Card holder
‘Carbon wire
& weight’
Copper Tabs
Courtesy: C. Field, Y.Sung
BFW Results
June 2009 FAC
• Wires soldered to copper tabs
• Wires from copper tabs connect to BFW feedthrough
• Feedthrough to be grounded and RF shielded
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BFW Wires
X-Wire
Nominal Beam Axis
in IN Position
Wire Radius 34 - 40 µm
Y-Wire
Note: Wires are fixed!
Beam scanning will be
achieved through girder
motion.
Card Out Direction
(½ stroke length shown)
BFW Results
June 2009 FAC
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Heinz-Dieter Nuhn
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BFW Functions
BFW
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)
BFW
Undulator
Quad
Girder
Replacement
Vacuum
Chamber
Wires
Beam Direction
Planned Applications
Loose End Alignment
Beam Profile Scanning
BFW Results
June 2009 FAC
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Heinz-Dieter Nuhn
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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
BFW Results
June 2009 FAC
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Scan Procedure Incorporated in Matlab GUI
Start matlab gui BFWscan_gui
Choose girders (1-33), X-wire or Y-wire, scan range, and scan step size
For instance
Girder: 1 - 33
Wire: ‘X’ and ‘Y’
Range: -250 microns to +250 microns
Step size: 50 microns.
When started, the gui will then for each selected girder
Move 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.
BFW Results
June 2009 FAC
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Scan with BFW11 Y-Wire
ANL BLM 25
Dump Cerenkov
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June 2009 FAC
ANL BLM 33
BLF:U01-U16
PEP-II BLM17
Dump Scintillator
Expected Collision Position11
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BLF:U17-U33
PEP-II BLM25
Heinz-Dieter Nuhn
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BFW Alignment before FEL Commissioning
BFW Results
June 2009 FAC
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BFW Alignment after FEL Commissioning
BFW Results
June 2009 FAC
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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.
BFW Results
June 2009 FAC
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Transverse Electron Beam Sizes
BFW Results
June 2009 FAC
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ANL/PEP Loss Monitor Responses
BFW Results
June 2009 FAC
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BLF 17-33 Responses
Girder Range Covered by Fiber
BFW Results
June 2009 FAC
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FEL Scattering on BFW wire
Fringes indicate transverse coherence
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June 2009 FAC
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Heinz-Dieter Nuhn
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Summary
The 33 Beam Finder Wire (BFW) devices in the
undulator system are working very well.
They enable monitoring of several parameters
Loose-end alignment
Beam sizes, i.e. betatron matching
BLM calibration
Transverse 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.
BFW Results
June 2009 FAC
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Heinz-Dieter Nuhn
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End of Presentation
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June 2009 FAC
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Heinz-Dieter Nuhn
[email protected]