bfw results

1 Heinz-Dieter [email protected]

1BFW ResultsJune 2009 FAC

BFW Results

Heinz-Dieter Nuhn – LCLS Undulator Group LeaderJune 9, 2009



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



Beam Finder Wire Location on Girder

Beam Finder Wire Housing

Beam Direction

Undulator Segment

Vacuum Chamber



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



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



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



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.



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



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



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.



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



BFW Alignment before FEL Commissioning



BFW Alignment after FEL Commissioning



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.



Transverse Electron Beam Sizes



ANL/PEP Loss Monitor Responses



BLF 17-33 Responses

Girder Range Covered by Fiber



FEL Scattering on BFW wire

Fringes indicate transverse coherence



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



End of Presentation

bfw results

Documents