1. EBTF Design Review Technical Meeting Group
Clive Hill
27th September 2011

2. Notes from Meeting
Transition tapers for low impedance are required, therefore a transition taper is required before the window flange which will need slots to allow laser beam to pass. Continue with additional design work of the current scheme should show this.
2.3mm nominal clearance between centre of laser beam and diameter 14.8mm gun aperture tube appears not to be enough. Laser beam may be 2mm diameter and it may be necessary for it to scan 3mm x 3mm square area of the cathode plate. Moving the mirror flange further down stream to increase clearance would extend the distance to the 1st quadrupole and also reduce the size of the electron beam aperture in the mirror region.
In the current scheme the positions o the BPM and WCM should be swapped.
It was agreed it was essential that a visit to LAL should be arranged asap to discuss the technical issues concerning the gun.
A single power point should be generated to show both the in-vacuum and out of vacuum mirror schemes. This should include slide which to summarise the advantages and disadvantages of the two schemes.

3. In Vacuum Lightbox Design
Ppot, YAG, H & V Slit
Collomator
Stripline BPM
Bellows
Bellows
H & V Corrector
Valve
Lightbox
Gun Solenoid
WCM
H & V Corrector
Laser In

4. In Vacuum Lightbox Design
Ppot, YAG, H & V Slit
Collomator
Valve
WCM
Gun Solenoid
Lightbox
H & V Corrector
Bellows
H & V Corrector
Bellows
Stripline BPM
65mm
1235 mm

5. In Vacuum Lightbox Design
Rigid gun support at cathode end
In Vacuum Lightbox Design
Strip line BPM
120 mm slot length

6. In Vacuum Lightbox Design
Tapered beam pipe with ø 6 mm holes for laser
Mirror
Laser path 1.4⁰ from hor. Shown 90⁰ out of position for clarity
Beam impedance screens in bellows and valve
Restriction due to 15mm aperture
Beam impedance screen ø15mm aperture
RF spring here or capacitance plate

7. In Vacuum Lightbox Design
Accurately machined mirror holder with 4 mirror positions– can be removed from chamber to assemble mirrors.
kinematic mount – can adjust inside chamber
Mirror OD 10mm ?
Mirror thickness 2mm ?
Laser path
Shown 90⁰ out of position for clarity

8. EMMA H&V Corrector

9. Lightbox design with mirrors inside vacuum system
Possible angular error in laser mirror position due to resolution of adjustment = 0.01°
Possible error in cathode position due to resolution of gun adjustment = 0.02°
Nominally 2.3mm distance between laser beam centre and tube id. At this position the laser beam translates 0.068mm for every 0.01° angular error of laser mirror
Nominal angle of laser path
laser mirror in vacuum
Ø14.7m aperture tube
1.4°
1.42°
1.44°
217mm
538mm
610mm
With 0.01° angular error of laser mirror and 0.02° angular error of cathode the distance between laser beam centre and tube id = 2.16mm
Possible angle of reflected laser path due to error 0.01° in laser mirror and 0.02° in cathode
Ø6 Holes for laser path

10. Lightbox design with mirrors outside vacuum system
Ppot, YAG, H & V Slit
Collomator
Stripline
BPM
H &V Corrector
Laser mirrors
H &V Corrector
Valve
WCM
Gun Solenoid
Laser Path
Ion Pump ?

11. Lightbox design with mirrors outside vacuum system
Ppot, YAG, H & V Slit
Collomator
Lightbox design with mirrors outside vacuum system
Laser entrance/exit window flange
Valve
H & V Corrector
Gun Solenoid
H & V Corrector
WCM
Stripline BPM
Bellows
Laser mirror
Ø35mm chamber aperture
Ø18mm chamber aperture
Ø48mm chamber aperture
1235 mm

12. Lightbox design with mirrors outside vacuum system
Electron beam aperture Ø18mm
Ø16mm laser port
Lightbox design with mirrors outside vacuum system
Aperture transition cone with slots for laser to pass
Ø12.7mm x 3 thick laser mirror on adjustable mount

13. 2.3mm clearance between laser beam centre and tube
1.4°
Aperture transition cone with slots for laser to pass
Ø12.7mm x 3 thick laser mirror on adjustable mount
Ø16mm laser port
Ø16mm laser port
Ø12.7mm x 3 thick laser mirror on adjustable mount
Ø18mm Electron beam aperture

14. Window Flange Could the e-beam be mis-steered into a window ?
4 x standard mini conflat windows – aperture ø16
Braze in to standard kovar spinning
Weld,
kovar to st. st.
Weld
St. st. tube ? or
st. st. cooled ? or
copper cooled ?
depending on mis –steer of electrons or laser beam heating ?
Could the e-beam be mis-steered into a window ?
114 CF flange

15. Lightbox design with mirrors outside vacuum system
Adjustable laser mirror in atmosphere adjustment resolution = 0.01° (175µrad)
Possible angular error in cathode position due to resolution of gun adjustment = 0.02°
Nominally 2.3mm distance between laser beam centre and tube id. At this position the laser beam translates 0.125mm for every 0.01° angular error of laser mirror
Possible angular error in laser trajectory due to resolution (0.01°) of laser mirror
Ø14.7mm aperture tube
Nominal angle of laser path
1.4°
1.42°
1.44°
217mm
938mm
With 0.01° angular error of laser mirror and 0.02° angular error of cathode the distance between laser beam centre and tube id = 1.85mm
Possible angle of reflected laser path due to error 0.01° in laser mirror and 0.02° in cathode

16. Comparison of 2 designs Mirrors In Vacuum Mirrors Outside Vacuum
Angle of laser to horizontal
1.4 degrees??
Distance from laser centre to 15mm aperture restriction in gun
2.3mm
Distance from cathode to mirrors
610mm
920mm
Diameter of mirrors
10mm
12.7mm
Mirror adjustment
4 mirrors on same mount which can only be adjusted following vacuum let up.
Mirrors on individual mounts which can be adjusted without vacuum let up.
Electron beam aperture (downstream of gun)
Ø35 reducing to
Ø15 at position of mirrors increasing to Ø35
Ø18 at position of mirrors increasing to Ø35
Potential risks due to electron beam mis-steer
None
Damage to window
Order of devices
H & V Steerer-Valve-Lightbox-WCM-H & V Steerer-BPM-YAG/slit/ppot etc
H & V Steerer-Valve-BPM--WCM-H & V Steerer-mirrors- YAG/slit/ppot etc
Vacuum performance
Mirrors are vacuum baked and some risk of damage or misalignment during bakeout. Could compromise design of vacuum design
Mirrors not effected by bakeout